Suction Bucket lid plate design and welding automation · welding automation Make Offshore wind turbines a competitive technology by making the production processes of new foundtiona

Suction Bucket lid plate design and

welding automation

Make Offshore wind turbines a competitive technology by making the

production processes of new foundation structures more flexible

By

JAVIER ZARAGÜETA GONZÁLEZ

MASTER THESIS

Department of Mechanical and Manufac-

turing Engineering

Fibigerstræde 16

DK - 9220 Aalborg Øst

Tlf. 45 9940 8938

[email protected]

www.m-tech.aau.dk

Title:

Suction Bucket lid plate design and welding

automation

Semester:

VT-4

Theme:

Master Thesis Project

Project period:

February 2017 - June 2017

ECTS:

30

Javier Zaragüeta González

Supervisors:

Morten Kristiansen (AAU)

Sigurd Villumsen (AAU)

Iñaki Díaz Garmendia (Tecnun)

Contact at Universal Foundations:

Soren A. Nielsen

Group Number:

3.120J

Number printed: 3

Pages: 70

Appendix: 22

Enclosures: 1

Synopsis

O�shore wind is potential technology to en-

sure the transition to a cleaner energy pro-

duction. However, even its energy generation

potential has been proven, this technology's

high costs and consequently low LCOE rate,

have left it in the background of the renewable

energy production.

An important item from this cost is the foun-

dation manufacturing. The low automation

on the manufacturing of foundations for o�-

shore wind turbines and the use of ine�-

cient technologies are the main causes of the

high costs of this technology. Nevertheless,

new emerging foundation technologies, like

the Mono Bucket, are being developed to

change this situation.

This project proposes a solution that searches

the reduction of the designing and welding

processes cost of one of the main components

of a Mono Bucket foundation. To ful�l this

task a solution consisting of two parts:

1. Parametric design of some structural

components.

2. De�nition of an automatic welding pro-

cess and an automatic robot program

generator.

The content of the report is freely available, but publication (with source reference) may only take place in

agreement with the author.

Preface

This report documents the Master Thesis composed by Javier Zaragüeta González on his

exchange program at Aalborg University during the period from the 1st of February to the

2ND of June 2017. The theme for the thesis is Manufacturing automation.

The project is completed under supervision of Associate Professors Morten Kristiansen

and Sigurd Villumsen, from Aalborg University, and Iñaki Díaz Garmendia from Tecnun,

University of Navarre. This project would not have been possible without the collabora-

tion of Søren A. Nielsen from Universal Foundations, who provided this project with very

interesting information about Mono Buckets and lid plates design.

Reading guide

Through the report source references in the form of the Harvard method will appear and

these are all listed at the back of the report. References from books, homepages or the

like will appear with the last name of the author and the year of publication in the form

of [Author, Year]. They can furthermore appear with speci�c reference to a chapter, page,

�gure or table.

Figures and tables in the report are numbered according to the respective chapter. In

this way the �rst �gure in chapter 3 has number 3.1, the second number 3.2 and so on.

Explanatory text is found under the given �gures and tables. Figures without references

are composed by the project group. As for �gures and tables, equations are also numbered

according to their respective chapter.

All the code �les, 3D models and RobotStudio �les and folders are available as an enclosure

of the project. This project provides the reader and user of the tools presented a user guide

that can be found on Appendix E. For further questions or support for the software tools,

write an email to the following address:

[email protected]

v

Table of contents

Chapter 1 Introduction 1

1.1 Europe 2020 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 O�shore wind energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Chapter 2 Problem statement 11

2.1 Modular Suction Bucket components . . . . . . . . . . . . . . . . . . . . . . 11

2.2 Design variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.3 Long manufacturing process . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.4 Suction Bucket cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Chapter 3 Project goals 17

Chapter 4 Parametric design 19

4.1 Mono Bucket design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.2 Lid plate components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.3 Parametrization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.4 SolidWorks' Equiation Manager . . . . . . . . . . . . . . . . . . . . . . . . . 30

Chapter 5 Automatic welding process 33

5.1 Welding station design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

5.2 Welding geometry determination . . . . . . . . . . . . . . . . . . . . . . . . 36

5.3 Welding parameters de�nition . . . . . . . . . . . . . . . . . . . . . . . . . . 43

5.4 Tool orientation de�nition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.5 Welding sequence de�nition . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Chapter 6 Lid Plate Generator 51

6.1 Parametric modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

6.2 Interaction with the lid plate 3D model . . . . . . . . . . . . . . . . . . . . 54

6.3 RAPID program generation . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

6.4 Welding characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Chapter 7 Economic study 61

7.1 Automatic welding cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

7.2 Cost - design variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

7.3 Cost variation with diameter . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Chapter 8 Conclusion and perspectives 69

8.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

8.2 Further work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

List of Figures 71

vii

List of Tables 73

Bibliography 75

Appendix A Bulb plate sections

Appendix B Welding parameters

Appendix C RAPID program structure

Appendix D Lid plate welding time and cost breakdown

Appendix E User guide

Introduction 11.1 Europe 2020

Europe 2020 is the European Union's ten-year jobs and growth strategy launched in 2010

to create the conditions for smart, sustainable and inclusive growth. Five headline targets

have been agreed for the EU to achieve by the end of 2020:

• Employment

• Research and development

• Climate change and Energy sustainability

• Education

• Social inclusion and poverty reduction

As it can be seen, climate change and energy sustainability are both issues of great

importance that directly condition the growth and development of a country. Therefore,

the following objectives have been set:

� Reduction of the 20% (or even 30%, if the conditions are right)of the greenhouse gas

emissions (1990)

� 20% of energy from renewable

� 20% increase in energy e�ciency

Of all renewable energies, wind energy is the technology expected to provide the largest

contribution to the EU's 2020 renewable energy targets. It is planned that wind will

provide the largest contribution from all Renewable Energy Sources (RES), supplying

14.4% of total net electricity generation by 2020. Wind energy is mainly produce by

two di�erent technologies: Onshore and O�shore wind turbines. Both are experiencing a

signi�cant increase in the last years, but onshore has been always the dominant technology.

A share of 24% of total wind generation is produced from wind o�shore capacities in 2020

(33 GW installed capacity), but the share of o�shore wind declines thereafter, as the high

costs of wind-o�shore limit its market penetration [ICCS-NTUA, 2016].

However, the North Sea in particular is well suited to the development of o�shore wind

energy and will be key in increasing the EU's energy security and de-carbonising the

economy. Some countries like Denmark have even more ambitious goals that the one set

by the EU regarding energy. The Danish Energy Agency invests heavily in renewable

energy and is working towards two main goals[Gillis, 2014]:

� 2020 goal: 50% of the total electricity consumption supplied by wind power.

� 2050 goal: Energy and transport sector completely supplied by renewable energy.

1

VT3 1. Introduction

Denmark's progress in meeting these targets is remarkable. Last year, international press

praised Denmark's work in this regard, when the Nordic country broke world record

for wind power: "Denmark produced 42% of its electricity from wind turbines last year

according to o�cial data, the highest �gure yet recorded worldwide" [Neslen, 2016]. Since

EU member met on 2010 and �x the 2020 targets, Denmark has kept on increasing its

wind energy production and it is very likely to achieve its on 2020 goals. The following

graph shows this fact perfectly:

Figure 1.1: Wind power in Denmark [Neslen, 2016]

However, there are great opportunities in o�shore wind farms, as they can be much more

e�cient, specially in countries like Denmark:

"There is a huge potential for power generation on o�shore wind farms in the Danish

seas. Denmark has a geographical advantage in regards to cost-e�ective installation and

operation of large-scale o�shore wind farms in that the quality of the spatial, substrate

and wind conditions exceeds those of the neighbouring countries."[Association, 2014]

1.2 O�shore wind energy

The accomplishments described above are primarily achieved due to a high number of

onshore turbines. However within the recent years a new trend of moving the wind turbines

o�shore is evolving. O�shore wind technology is not something new. The �rst o�shore

wind project was Vindeby O�shore Wind Farm, installed o� the coast of Denmark in 1991.

Since then, bigger and bigger o�shore wind farms have been operating in shallow waters

around the world, mostly in Europe.

2

1.2. O�shore wind energy Aalborg University

Figure 1.2: Annual o�shore and onshore wind installations (MW) [Europe, 2016]

Figure 1.2 clearly show this trend of bringing wind turbines o�shore rather than building

onshore wind farms. This fact is mainly due to the following two reasons:

� Null a�ection to the population

As o�shore wind farms are built several kilometres far from the coast, both visual

and noise impacts decrease dramatically. Landscape perception and visual impact

are key environmental issues in determining wind farm applications related to wind

energy development as landscape and visual impacts are by nature subjective and

changing over time and location.

� Higher wind speeds

The higher strength and lower turbulences of marine wind makes it more suitable

for wind turbines. Danish Wind Industry Association estimates the wind resources

o�shore to be on average 50 % better than the ones obtainable onshore. The higher

winds has a considerable impact on the energy production of the turbines, e.g.

moving from 7.5 m/s to 9.5 m/s in wind speeds increase the energy production

with 40 %.

Even though the bene�ts of o�shore wind energy, its high cost is the main reason why

there is still a great di�erence between it and onshore wind and other renewable energy

sources. A common way to compare and express the overall cost of an energy source is

through the Levelized Cost Of Energy.

LCOE =Total cost over a lifetime

Energy produced over a lifetime(1.1)

3

VT3 1. Introduction

Figure 1.3: LCOE for all primary energy sources, Source: Siemens

From �gure 1.3 it can be concluded that, despite the potentials of o�shore wind energy, it

is still far from being considered a competitive energy source. To increase its LCOE, it is

fundamental to bring down the costs of this technology. To determine the potential areas

of improvement it is important to analyse the cost breakdown of the technology.

Figure 1.4: Capital cost breakdowns for typical onshore and o�shore wind systems [IRENA,2012]

As it can be seen in �gure 1.4, foundations and installation is the second most important

item on the budget of a o�shore wind system. Therefore, a reduction on the cost

foundations manufacturing and installation is a great way of making o�shore wind a more

competitive energy production technology.

1.2.1 Traditional o�shore foundations

One of the main components of every turbine to be installed o�shore is the foundation

where it lays on. The design of these structures has not received much attention, inheriting

designs from other sectors such as the Oil & Gas Industry. The traditional foundations

designs for o�shore wind turbines are the following ones:

� Monopile

� Tripod

� Jacket

� Gravity

4


1.2.1.1 Monopile foundation

Monopile foundation structure is a relatively simple design by which the tower is supported

by a single reinforced concrete pile, either directly or through a steel transition piece, that

is stuck into the seabed. The standard method of installation of piled structures is to lift

or �oat the structure into position and then drive the piles into the seabed using either

steam or hydraulic powered hammers. Monopiles are currently the most commonly used

foundation in the o�shore wind market due to their ease of installation in shallow to

medium water depths. [Association, 2003a]

Figure 1.5: Monopile foundation components, Source: 4CO�shore

1.2.1.2 Tripod foundation

The tripod foundation draws on the experiences with light weight and cost e�cient three-

legged steel jackets for marginal o�shore �elds in the oil industry. From a steel pile below

the turbine tower emanates a steel frame which transfers the forces from the tower into

three steel piles. The three piles are driven 10 to 20 metres into the seabed depending on

soil conditions and ice loads. The advantage of the three-legged model is that it is suitable

for larger water depths. At the same time only a minimum of preparations are required at

the site before installation. [Association, 2003b]

Figure 1.6: Tripod foundation components, Source: 4CO�shore

5

VT3 1. Introduction

1.2.1.3 Jacket foundation

These foundations consist of a more complex structure of steel bars, which are �xed

symmetrically outside the main axis of the structure. This leads to a signi�cant decrease

of material costs. There are many variants of the three or four-legged jacket structure,

typically consisting of corner piles interconnected with welded tubular joints with diameters

up to 2 meters. The soil piles are driven inside the pile sleeves to the required depth to

gain adequate stability for the structure. [4CO�shore, 2013b]

Figure 1.7: Jacket foundation components, Source: 4CO�shore

1.2.1.4 Gravity foundation

The gravity type support structure is normally a concrete based structure which can be

constructed with or without small steel or concrete skirts. The ballast required to anchor

the foundation consists of sand, iron ore or rock �lled into the base of the structure with

adjustments in the designed base width to suit the soil conditions. The design will include

a central steel or concrete shaft for transition to the wind turbine tower. The structure

requires a �at base and for most locations will require some form for scour protection which

is determined during detailed design stage. [4CO�shore, 2013a]

Figure 1.8: Gravity based foundation components, Source: 4CO�shore

6


1.2.2 New o�shore foundations

All the previous foundation types are the once that have been used for mainly all the

o�shore wind projects during the last years. As can be seen in �gure 1.9, the monopile

foundations have the dominant role on the o�shore wind foundations market

Figure 1.9: Current o�shore wind foundation type distribution, Source: WEU

However, as has been stated before, these foundation technologies absorb nearly a quarter

of all the budget and leave o�shore wind energy far from being competitive. To tackle

this problem some companies have been working on developing new foundations that can

bring down the price. The main innovative technologies are the following:

� Crane free gravity foundation

� Floating wind turbines

� Suction Bucket foundations

All the previous technologies have been developed to reduce the manufacturing, transport

and installation costs as much as possible. However, the Suction Bucket foundations have

to be highlighted among the others due to the fast development presented on the last years.

This technology is supported by the Carbon Trust's O�shore Wind Accelerator (OWA),

which is the world's largest industry collaboration focused on reducing the cost of energy

from o�shore wind through technology innovation.

1.2.2.1 Suction Bucket foundations

Suction Bucket foundations have been using for quite a long time in Oil & Gas industry,

but it has proved to be a very useful technology for o�shore wind foundations. They are

installed using a jet and suction system as the driving force. Lowering the pressure in

the cavity between the foundation and the seabed generates a water �ow, which lowers

resistance around the edge of the foundation's skirt. This reduces resistance and allows

seabed penetration. Once installed, it works like a common gravity foundation.

7

VT3 1. Introduction

Figure 1.10: Suction Bucket working principle, Source: Universal Foundation

This foundation technology has very interesting characteristics that make it a very

interesting alternative to traditional foundations:

� No seabed preparation needed

� Uses less steel than conventional piled foundations

� No pile driving needed, reducing the environmental impact during installation and

operation

� Can be removed for reuse or recycling by reversing the suction process

Nowadays, this technology has two main applications:

� Mono Bucket foundation

� Suction Bucket Jacket

Mono Bucket

On the one hand, Universal Foundation's Mono Bucket is an all-in-one steel structure

consists of a multi-shell foundation with vertical sti�eners, a robust lid and a shaft for

interfacing with the wind turbine. This design combines the main aspects of a monopile

and a suction bucket into one product. As the design involves an installation technique

whereby the verticality of the foundation is controlled by a lip-mounted jetting system,

there is no transition piece.

The technology has been developed over nearly a decade and after a number of successful

prototype installations for both met masts and turbine foundations, is now entering full-

scale production and supply to the commercial o�shore wind market.

8


Figure 1.11: Mono Bucket, Source: LEEDCo

Suction Bucket Jacket

On the other hand, Suction Bucket Jacket has been designed by DONG Energy based on

ideas from the SPT O�shore foundation, which consists on a three-legged jacket structure

with three cup foundations that are anchored in the seabed using suction. So, this

technology can be considered as a combination of previously explained jacket foundations

and suction bucket technology.

This foundation has been designed for serial fabrication and will save costs across design,

fabrication, installation through to operation. The German o�shore wind project Borkum

Ri�grund 1 has been selected for testing this foundation before a new innovative design

can be considered for commercial projects.

Figure 1.12: Lifting of a jacket structure with suction buckets, Source: DONG Energy

9

Problem statement 2At the end of the previous chapter some innovative o�shore foundations have been

described. These technologies are thought to bring down the manufacturing and

installation cost of the foundations, e.g. using less raw material or facilitating the transport

from the harbour to the installation point. However, there is still a long way to reduce the

LCOE of the o�shore wind technology to make it a more competitive energy source.

In this chapter the main characteristics of a Suction Bucket foundation structure, the

modular design of Mono Bucket foundations in particular, will be analysed in order to point

this technology's strong and weak points. Knowing this, this project problem statement

will be stated.

2.1 Modular Suction Bucket components

The studied Suction Bucket consist on a new design. Currently, all the parts of the

structure were formed in a single piece. The new version consists on a modular structure

that tries to ease the manufacturing of the components and its transportation, but increases

the welding needed to assemble the foundation. The modular structure is composed by

three components:

Figure 2.1: Exploded view of a suction bucket [Villumsen, 2017]

11

VT3 2. Problem statement

1. Skirt plates

These plates are bended metal sheets which welded together to form the skirt of the

foundation. This part of the foundation is actually the one that is grounded into the sea

bead to form the foundation.

2. Lid plates

Lid plates enclose the cylinder formed by the skirt plates and connect them with the wind

turbine. The typical design consists on a main �at plate with some smaller plates welded

perpendicularly to act as reinforcement and ensure the mechanical properties of the part.

3. Legs

These components act as reinforcement by transmitting the loads from the wind turbine

to the foundation.

2.2 Design variability

The Suction Bucket is a very �exible foundation technology that can be installed in many

di�erent soils with little seabed preparation. This �exibility, however, makes the size of

the bucket very variable. All the components that are part of the structure have to be

scale every time the soil changes, what is quite common considering the size of the o�shore

wind farms.

Additionally, the large areas covered by the o�shore farms usually have some depth

variations, what also implies some size variations on the Suction Buckets situated at

di�erent depth in the same farm. For example, London Array wind farm's, situated near

the North Sea coast of the United Kingdom, covers an area of 122 km2 in which the seabed

depth varies as is shown in �gure 2.2:

Figure 2.2: Depth variation in the London Array wind farm area, [H. Burningham, 2008]

As it can be seen in �gure 2.2, the transition from a depth of 5 meters to 20 meters can

happen in ranges of tens of meters. This makes that from one turbine to the to the next

12

2.3. Long manufacturing process Aalborg University

the diameter of the Bucket foundation can vary almost to double.

Finally, it is important to remark that these foundations can be used by di�erent

manufacturers of wind turbines. This means that the diameter of wind turbine tower

might change from one company to another. What is more, every company has di�erent

models of wind turbines depending, specially on their power, which introduces another

variation fact in the design of the foundations.

2.3 Long manufacturing process

When the foundation parts have been scaled to the needs of every turbine model, soil

conditions and water depth, the manufacturing of the structure is carried out. The

productions process follows the next diagram:

Figure 2.3: Suction Bucket manufacturing process

As it can be seen in �gure 2.3, the manufacturing process consists on the sub-assembly of

all the components of the modular Suction Bucket described in 2.1 welding which are later

13

VT3 2. Problem statement

welded (represented by red boxes on the �ow diagram) to form the structure. So, even

if there are more processes involved(like bending and cutting, represented by green and

blue boxes), it can be said that welding is the predominant one. The welding precesses

described in �gure 2.3 are shown in the following �gure:

Figure 2.4: Welding paths types for the manufacturing of the Suction Bucket [Villumsen,2017]

From �gure 2.4 it can be said that all the welds needed for the union of the di�erent

components of the Suction Bucket consist on straight paths, which eases the welding

process. However, the thickness of the plates to be welded makes it necessary to carry out

several passes for every weld. If we add this fact to the size of the structure, which can

reach diameters of 19 meters, implies that welding is the what determine the production

cycle time, specially if the welds are carried out manually. What is more, taking into

account that some parts, like the lid plate, need a sub-assembly before beginning with the

whole assembly of the structure, the number welding hours increase even more.

Table 2.1: Deposit rates of di�erent welding technologies, Source: TWI

Welding technologyDeposit rate [kg/h]

min max

MMA 0.4 5.5

GMAW 0.6 12

FCAW 1.0 15

SAW 3 16

14

2.4. Suction Bucket cost Aalborg University

2.4 Suction Bucket cost

After the quick overview of the two main problems of the production of a single Suction

Bucket explained on the previous sections, it can be concluded that the price of every

Bucket is not low enough to make this a competitive technology. What is more, the

transportation and inspection costs must be sum to the manufacturing cost, resulting in

a breakdown of the cost shown in the following �gure:

Figure 2.5: Estimated cost of a single suction bucket [Villumsen, 2017]

It is important to take into account that the manufacturing cost is nearly a quarter of the

hole budget of every modular Mono Bucket. This is mainly due to the facts presented in

the previous points of the chapter:

� Great amount of welding process needed due to the modular design

� Continuous design changes due to external conditions

� Size and thickness of the steel plates used in the structure

� High ine�ciency of carrying out all the welding manually

� Need of sub-assemblies

In conclusion, all these design and manufacturing problems do not allow the Suction Bucket

technology to break into the market of o�shore wind turbine foundations. The LCOE

reduction of the o�shore wind technology can come from the implantation of the Suction

Bucket as the predominant foundation technology, but before that all this problems have

to be tackled. To sum up, the problem statement of this project is stated as:

How could the design and manufacturing time of a Suction Bucket be reduced

to make a more economical and reduce its LCOE?.

15

Project goals 3From the previous chapter it can be concluded that the production of Suction

Bucket foundation structures is a small-batch-size process. That implies that product

characteristics change from order to order and the number of identical products in an

order is small or single. This means that the design of the product and the production

preparation have to be rede�ned every time a new order is placed.

Furthermore, the manufacturing time needed to produce each foundation structure makes

the Suction Bucket foundations in particular and o�shore wind energy in general non-

viable technologies if they are compared with other energy production technologies. As

was explained on the previous chapter, welding is the determinant process of the modular

Mono Bucket's manufacturing, so this project will be focused on improving the e�ciency

and productivity of this process. Manual welding of the di�erent structural components

should be substituted by a more e�cient manufacturing process.

Taking this two facts into account, the question stated on the problem statement can be

particularized in more detailed questions:

� How can the design process be simpli�ed?

� How can the generation of manufacturing data be automatized?

� How can the welding be more �exible?

This project proposes a solution focused only on the lid plates of the foundation structure,

to serve as an starting point for future development to the whole structure. Knowing this

and taking the previous questions as a guide the main objectives of this project can be

stated:

Design of a 3D parametric model of the lid plate

To enable a fast resizing and modi�cation of the design of the lid plate, a parametric

model would be developed in SolidWorks. This model will ask the user to select a model

of lid plate from a prede�ned list and will scale and modify a base model based on the

geometrical characteristics of that selection.

Development of an automatic manufacturing data generation tool

Once the geometry of the model has been correctly scaled, welding data will be generated

by the means of welding points, paths and parameter de�nition. For this purpose, a

software tool will be programmed using C# language that will interact with the 3D model

of the lid plate to de�ne all this data.

17

VT3 3. Project goals

De�nition of an automatic manufacturing process based on a robotic arm

With all the data from the previous steps, a robot programming will be carried out in

order to make the manufacturing process completely automatic. This programming will

be automatically generated from the C# programmed tool and uploaded to ABB's o�-line

simulation and programming software; RobotStudio.

To accomplish these three objectives the �ow diagram shown in �gure 3.1 will be followed:

Figure 3.1: Project �ow diagram

In conclusion, this project searches the reduction of the design and manufacturing costs

of the Suction Buckets by proposing a faster and more e�cient design and manufacturing

processes. So, to make sure that the proposed solution is a e�cient way of reducing the

costs of producing each modular Mono Bucket and economic study will be carried out. In

this study the costs of traditional and automatic manufacturing processes will be compared

and how di�erent designs of Suction Bucket's lid plate a�ect the manufacturing cost.

18

Parametric design 4This chapter describes the design and geometry of lid plates from a modular Mono Bucket

foundation. Once the geometry has been analysed, the relations between the di�erent

dimensions of this component will be de�ned to geometrically relate all the available

designs of lid plate studied in this project. This will enable the parametrization of the

lid plate which will simplify its design, reducing the time needed to carry out the 3D

design of every lid plate model.

4.1 Mono Bucket design

While designing modular Mono Bucket foundations there are a lot of aspects to consider

to size all the components of the structure. Aspects such as the forces introduced by the

maritime environment and the wind turbine or the conditions of the soil are critical to

determine the loads that the foundation structure has to hold. So, to correctly design the

Bucket complicated mechanical calculations have to be carried to.

Universal Foundation, the company responsible of the design of the Mono Bucket

foundations, has developed a calculation tool based on Matlab called Fast Bertha that

calculates the loads that the foundation has to withdraw in every case and obtains all the

geometrical parameters needed to design the foundation. The main task pane of this tool

is shown in �gure 4.1:

Figure 4.1: FastBertha tool task pane, Source: Universal Foundation

19

VT3 4. Parametric design

As the focus of this project is not to carry out all the mechanical calculations that the

FastBertha does to design each Mono Bucket model, some models obtained from this tool

would be analysed. In the following table, all the design variations that will be studied in

the project are shown:

Table 4.1: Lid plate design variations, Source: Universal Foundation

Model Lid pressure [KPa] Do [m] Di [m] Bulb plates α [◦]

MB9_200 200 9 2 8 20

MB9_300 300 9 2 8 20

MB9_400 400 9 2 8 20

MB10_200 200 10 2 8 20

MB10_300 300 10 2 8 20

MB10_400 400 10 2 8 20

MB10_400_6 400 10 2 6 30

MB10_400_12 400 10 2 12 15

MB10_400_15 400 10 2 15 12

MB11_200 200 11 2 8 20

MB11_300 300 11 2 8 20

MB11_400 400 11 2 8 20

MB12_200 200 12 2 8 20

MB12_300 300 12 2 8 20

MB12_400 400 12 2 8 20

MB12_400_12 400 12 2 12 15

MB12_400_15 400 12 2 15 12

These models are typical designs of Mono Buckets that have already been installed or are

going to be installed soon in some of Universal Foundation's projects. As it can be seen in

table 4.1, the main variables that determine the Mono Bucket model are the outer diameter,

lid pressure and lid angle. These parameters have an important roll on determining the

characteristics of the Mono Bucket and are subject to a great variability as was explained

in the previous chapter.

In order to answer the need for designing parts which size has to be rede�ned constantly,

this project proposes the development of a parametric design. The �rst step on making the

design of the parts from the foundation structure more �exible is to analyse the target part

and determine how it has to be rescaled. From all the components of the Mono Bucket,

the lid plate is the one whose manufacturing is most easily automated, so it is the chosen

part to build a �rst parametric design.

20

4.2. Lid plate components Aalborg University

4.2 Lid plate components

Lid plates are responsible for closing the top of the foundation structure and are connected

to the rest of the parts, making them vital elements of the foundation. Each lid plate is

formed by the assembly of multiple parts, shown in �gure 4.2

Main plate1. Bulb plates2. Lateral plates3.

Figure 4.2: Geometrical parameters of the main plate

Before carrying out any design, is important to study the geometry of each of the

components of the lid plate.

4.2.1 Main plate

The main plate is responsible for supporting the remaining parts that form the lid plate.

It has the shape of a circular annular sector and is de�ned by the following parameters:

Figure 4.3: Geometrical parameters of the main plate

21


α : Lid plate angle

Do : Outer diameter

Di : Inner diameter

t : Plate thickness

Both diameters; Do and Di de�ne the annular sector. These features depend mainly on

the seabed depth where the Suction Bucket is going to be installed and the wind turbine

that is going to be put on the top of the foundation.

On the other hand, the lid plate angle α de�nes the width of the lid plate. This parameter

is de�ned by the number of legs that are going to be installed to connect the foundation

with the wind turbine. As the number of legs increases, the angle α will be reduced and

consequently, the number of lid plates need to complete the lid of the Suction Bucket will

increase too.

4.2.2 Lateral plates

These plates consist of a simple rectangular shape plate with two 45º cuts on each end.

They are positioned parallel to the edges of the main plate and are responsible of linking

all the bulb plates together to ensure the improvement of the mechanical properties of the

lid plate.

(a) Lateral plates layout

(b) Detailed view of the lateral plates' cut

Figure 4.4: Lateral plates

22

4.2. Lid plate components Aalborg University

4.2.3 Bulb plates

Bulb plates are installed on top of the main plate and between the lateral plates, arranged

in a pattern in which the separation between bulb plates decreases as they move away

from the inner part of the piece. This arrangement can be seen in �gure 4.5:

Figure 4.5: Bulb plates layout

These plates are standardized structural pro�le commonly used for ship building and other

constructive applications. The dimensions that give the name to each model of bulb plate

are the height (bmm) and thickness (tmm) of the plate. So, a 180x10 bulb plate model,

would have a height of 180 mm and a thickness of 10 mm. These two dimensions are

display in �gure 4.6:

Figure 4.6: Bulb iron section and main dimensions

All the bulb plate models used for the di�erent lid plate designs are picked from a

manufacturer's catalogue that can be found in Appendix A.

The main objective of these plates is to improve the mechanical properties of the part

and for that is important to de�ne correctly the position of each one of them. Depending

on the operating and environmental conditions in which the foundation is going to be

installed, the section model selected varies. As the mechanical stresses that the foundation

has to withstand increase, the selected model will have bigger and more robust sectional

properties. Additionally, if the diameter of the bucket increases the separation between

bulb plates will vary too.

Going into detail of the design of the lid plate, FastBertha calculates the previously shown

parameters plus the bulb plate disposition to completely de�ne the lid plate (see �gure

23


4.7). This disposition depends barely on the diameter of Bucket or the outer diameter the

lid plate, as can be seen in table 4.2:

Figure 4.7: FastBertha lid plate results example, Source: Universal Foundation

In this project only 8 bulb lid plates will be designed and analysed to focus on how the

variability of other parameters like the lid angle or the Bucket diameter a�ect the design

and the manufacturing of the lid plate. Knowing this, in the following table the position

of each one of the eight bulb plates on every lid plate model can be seen:

Table 4.2: Bulb plates possible disposition [mm], Source: Universal Foundation

Do = 9 mDo = 10 m

Do = 11 mDo = 12 m

30◦ 20◦ 15◦ 12◦ 20◦ 15◦ 12◦

0-1 810 830 930 960 980 1040 1160 1200 1220

1-2 490 500 560 580 590 630 700 720 730

2-3 420 430 480 500 510 540 600 620 630

3-4 390 400 440 460 470 500 560 580 590

4-5 320 330 370 380 390 420 460 480 490

5-6 290 300 330 350 350 380 420 430 440

6-7 290 300 330 350 330 380 420 430 440

7-8 230 230 260 270 270 290 330 340 340

What is more, the section of the bulb plate changes depending on its position and the lid

plate model selected. The selection of each bulb plate is based on the calculation carried

out by FastBertha and the available bulb plate models (see Appendix A). So, all the bulb

plates required for each one of the lid plate models obtained from this tool have been saved

on a Excel data base, so, the program can easily acces that date. The bulb plate sections

selected for every model are displayed in table 4.2:

24

4.3. Parametrization Aalborg University

Table 4.3: Bulb plate sections of every lid plate model [mm x mm], Source: UniversalFoundation

Bulb plate

Model 1 2 3 4 5 6 7 8

MB9_200 140x8 160x7 160x9 180x8 180x8 180x10 180x10 200x9

MB9_300 180x8 180x8 200x9 200x9 200x10 220x10 220x10 220x11.5

MB9_400 180x10 200x9 220x10 220x10 220x11.5 240x10 240x11 260x10

MB10_200 160x8 180x8 180x9 200x9 200x9 200x11.5 220x10 220x10

MB10_300 180x10 200x9 220x10 220x11.5 240x10 240x11 240x11 260x10

MB10_400 200x10 220x10 240x10 260x10 260x10 280x11 280x11 280x11

MB10_400_6 260x12 280x11 300x13 320x13 340x12 340x14 320x13 430x17

MB10_400_12 160x9 180x8 200x9 200x11.5 220x10 220x10 220x11.5 200x11.5

MB10_400_15 140x8 160x7 180x8 180x8 180x9 200x9 200x9 180x8

MB11_200 180x8 180x10 200x10 220x10 220x10 240x10 240x10 240x11

MB11_300 200x9 220x10 240x10 260x10 260x10 280x11 280x11 280x11

MB11_400 220x10 240x10 260x11 280x11 300x11 300x12 300x13 320x12

MB12_200 180x10 200x9 220x10 240x10 240x11 260x10 260x11 260x12

MB12_300 220x10 240x10 260x10 280x11 280x12 300x11 300x12 320x12

MB12_400 240x10 260x10 300x11 300x13 320x12 340x12 340x12 340x14

MB12_400_12 200x9 220x10 240x11 260x10 260x10 280x11 280x11 260x10

MB12_400_15 180x8 180x9 200x10 220x10 220x10 240x10 240x10 200x11.5

As it can be seen in table 4.2, in every model, as the bulb plate is positioned further from

the inner diameter its size increases. Additionally, the size of the bulb plates increases

with the bucket diameter, the lid pressure and the lid angle. So, for bigger lid plates (α ↑or Do↑) and for deeper seabed applications (Lid pressure↑) the used bulb plates would be

bigger.

Knowing all the characteristics of a lid plate and having all the data provided by FastBertha

it is possible to look for the equations and relations that will enable the parametric design

of all these lid plate models.

4.3 Parametrization

To start with the parametric modelling, a base model has to be de�ned. In this case,

the smallest lid plate model (MB9_200, see characteristics in tables 4.1, 4.2 and 4.3) will

be used as the base model and will be scaled based on the user's needs. To de�ne the

geometry of the 3D model of the base model there are a series of geometrical parameters

that have to be determined. Figure 4.8 shows the most important dimensions of the lid

plate:

25


Figure 4.8: Geometrical parameters of the lid plate

α : Lid plate angle

Ro : Outer radious

Ri : Inner radious

d1 - d8 : Distance between bulb plates

To determine all these properties it is important to calculate the mechanical stresses that

the structure has to withdraw in each application. However, there is not a single solution

for each case, because there are more than one way of improving the mechanical properties.

For example, it can be done by increasing the size of the lid plate by increasing its outer

diameter or by increasing the number of bulb plates.

All the models obtained using Universal Foundation's FastBertha tool are di�erent design

options for multiple working environments. The �rst decision that has to be taken is the

size of the bucket. This fact will determine the design of the rest dimensions. On the one

hand, the disposition of the bulb plates on top of the main plate depends on the size of

the bucket (table 4.2) . The relation between the distances between bulb plates on a base

model of 9 meter of diameter and distances on buckets with a bigger diameters can be seen

in �gure 4.9:

26


Figure 4.9: Distance between bulb plates relation

As it can be seen, the relation is almost linear and can be expressed using the following

equations:

d10m = 1.1525 · d9m − 4.2797 (4.1)

d11m = 1.2775 · d9m + 5.0953 (4.2)

d12m = 1.4256 · d9m + 3.8676 (4.3)

However, looking at table 4.2 it can be realized that the disposition of the lid plates also

changes with the lid angle. Once more the relation of the distances between the bulb plates

on 10 m and 12 m diameter Mono Buckets with di�erent lid angles and a base model of 9

m diameter and a lid angle 20◦ is graphed:

27


Figure 4.10: Distance between bulb plates relation Do = 10 m, α 6= 20◦

This time again the linear relations are easily identi�ed. The equations of the lines shown

in �gure 4.11 are the following:

d10m,30◦ = 1.0245 · d9m,20◦ + 0.0466 (4.4)

d10m,15◦ = 1.1807 · d9m,20◦ + 3.0582 (4.5)

d10m,12◦ = 1.2150 · d9m,20◦ − 3.3421 (4.6)

28


Figure 4.11: Distance between bulb plates relation Do = 12 m, α 6= 20◦

As in the previous cases, the relation of bulb distances is linear and is expressed by the

following equations:

d12m,15◦ = 1.4771 · d9m,20◦ + 1.7669 (4.7)

d12m,12◦ = 1.5017 · d9m,20◦ + 1.8136 (4.8)

On the other hand, each model's bulb plate selection is unique and depends on the outer

diameter, the lid pressure and the lid angle. To allow a easy manipulability of the bulb

plate set of each lid plate model a data base has been created on Excel.

As it was said in the previous section, bulb plates are standardized pro�les selected from

distributor's catalogues and their main characteristics are the height and the thickness of

the plate. However, as it can be seen in �gure 4.12 there are some more dimensions that

have to be determined to de�ne a 3D model of every lid plate.

29


Figure 4.12: Dimensions of a bulb plate section, , Source: British Steel

Just by taking a look at the catalogue available at Appendix A, it can be realized that the

radius r and the distance c only depend on the height of the bulb plate. So, taking the

smallest lid plate section as a reference a linear relation can be stated to determine these

two dimensions for a given bulb plate height. These relations are de�ned by the following

equations:

c =b− 140

20· 3 + 19 (4.9)

r =b− 140

20+ 5 (4.10)

So, just by knowing the height and the thickness of the bulb plate its section is completely

de�ned.

4.4 SolidWorks' Equiation Manager

To ensure the correct resize and modi�cation of the base model, the equations that relate

the di�erent dimensions have to be introduced into the 3D design software, SolidWorks

in this case. For this purpose SolidWorks' Equation Manager is used. This tool allows

the user to state relations between di�erent dimensions of the model. All the equations

previously de�ned are introduced in the manager, so every time a dimension changes all

the other dimensions related to it will change too.

Additionally, a series of Custom Properties are set to de�ne each lid plate model. These

properties are unique for each model, its value will be determinate when the lid plate

model is generated and will be introduced in the equations to obtain all the remaining

dimensions of the lid plate. The de�ned custom properties are the following:

30

4.4. SolidWorks' Equiation Manager Aalborg University

� LidModel: Model of lid plate selected

from the list

� InnerD: Inner diameter (same as the

wind turbine to be installed)

� OuterD: Outer Bucket diameter

� LidAngle: Angle formed by the lid

plate and its centreline

� NumberBulbs: Number of bulb

plates (in this case always 8)

� LidPressure: Pressure that the en-

tire lid has to withstand

� Thickness: Main plate thickness

� LateralHeight: Lateral plate height

� Bulbm: Slope of the inter bulb dis-

tance relation

� Bulbn: Intercept of the inter bulb

distance relation

� Bh1-Bh8: Bulb plate heights

� Bt1-Bt8: Bulb plate thickness

With all these Custom Properties and all the equations stated previously a lid plate base

3D model is designed in SolidWorks. As was said before, this base model has the dimensions

of the smallest lid plate model from table 4.1; MB9_200. These parametrization equations

are introduce to the Equation Manager using the interface shown in �gure 4.13:

Figure 4.13: SolidWorks's Equation Manager

This way, a completely de�ned 3D parametric model is designed in SolidWorks. It will

wait for the user to introduce the required values of the Custom Properties to de�ne the

desired lid plate model 3D design.

31

Automatic welding process 5The welding of the Mono Bucket's lid plate consist mainly, on a series of linear welds

to join the smaller components to the main plate. However, these welding paths' length

changes depending on the lid plate design, so the proposed automatic solution should be

able to quickly rede�ne the welding targets and be �exible enough to manufacture all the

di�erent lid plate designs introduced by the user. The solution proposed in this chapter

has been developed to tackle both problems, using an automatic weld path de�nition and

a proper working cell design.

5.1 Welding station design

With a diameter that can exceed 12 meters, the work station need to produce lid plates

needs a big working area and a tool that is able to reach all the welding points. For this

purpose, this project presents a solution based on a robot arm mounted on a gantry crane

that enlarges its reachability and working area.

5.1.1 Robot and tool selection

The robot arm selected for this application is the IRB 4600-40/2.55 model, selected from

ABB 's catalogue. IRB 4600 robot series is a robotic arm commonly used for welding

applications and model 40/2.55 is the one with the largest working range from the series,

so it is a good choice for the working cell needed to produce lid plates.

Figure 5.1: IRB 4600-40/2.55 working range, Source: ABB

33

VT3 5. Automatic welding process

On the other hand, the tool chosen to be installed in the robot is the model PK 500. This

welding torch is the one which geometry best suits the welding orientations needed to carry

out in the lid plate from all the models available in the RobotStudio library.

Figure 5.2: PK 500 welding torch installed on a IRB 4600 robot in RobotStudio

5.1.2 Gantry crane design

The gantry crane used in this application would work as X and Y auxiliary axes to enlarge

the working area of the robot. With these mechanism the manufacturing of the lid plate

is carried out mainly on a horizontal plane, making it easy to position all the components

on top of the main plate. In addition, the support structure to hold and correctly position

the plate is much simpler than if another mechanism displacement is chosen. Additionally,

gantry cranes are commonly used in industry, so the implementation of this solution can

be carried out using an existing installation or at least it should be easier to implement in

a common factory than other solutions.

To represent the gantry crane a simpli�ed design has been carried out which basically

consist of three elements: X axis, Y axis and Joint. Both axes will consist of two prismatic

bodies which length has been set so that the the biggest lid plate model �ts on the work

area and connected by a simple double "U" shape joint. In this case, the largest lid plate

has a length of approximately 6 meters, so the gantry crane axes have been designed with a

length of 10 meters to be ensure that this and lager lid plate models would be manufactured

without problems. The representation of the gantry crane is shown in �gure 5.3:

Figure 5.3: XY Crane in RobotStudio

34

5.1. Welding station design Aalborg University

Once the components of the crane have been designed the mechanism characteristics are

de�ned. This consists of de�ning the moving limits of each axis and the frame where the

robotic arm is going to be attached. On the one hand, the moving limits of each axis

are 8 meters for the X axis and 7 meters for the Y axis. These dimensions of the axes

has been set to be able to �t all the available Mono Bucket design, leaving room if the

manufacturing of bigger lid plate designs is implemented in the future.

On the other hand, the position and arrangement of the frame (see �gure 5.4b) was selected

to ensure a easy translation of the welding points from the 3D model to the welding

station. Due to the arrangement of the welding cell, it is important to correctly de�ne the

coordinates origin. This will allow to correctly reference the welding coordinates obtained

from the parametric 3D model and generate the welding paths.

(a) Lid plate origin

(b) Work station origin

Figure 5.4: Coordinates origins

35


The coordinates origin of the welding station is situated at the base of the robot when

the XY is at home position, as is shown on �gure 5.4b. On the other side, remembering

from 6.2, the welding coordinates obtained from the 3D model and shown in the report

are referred to the center of the inner circle of the annulus (�gure 5.4a).

To �t those welding points into the working area of the station designed in RobotStudio,

some translations and a rotation have to be applied to each point. The rotation consist of

a 180◦ turn around the y axis and can be represented by the following rotation matrix:

Ry =

cos(180◦) 0 sin(180◦)

0 1 0

−sin(180◦) 0 cos(180◦)

=

−1 0 0

0 1 0

0 0 −1

(5.1)

Additionally, some translations are needed to position the lid plate on a reachable area for

the robot. So, these translations are added to the previous matrix:

T = 1000 ·

−1 0 0 1

0 1 0 3

0 0 −1 2, 3

0 0 0 1

(5.2)

Using this transformation matrix the coordinates from the 3D model can be translated to

the welding station following the next expression:Xstation

YstationZstation

1

=

Xlid

YlidZlid1

· 1000 ·−1 0 0 1

0 1 0 3

0 0 −1 2, 3

0 0 0 1

[mm] (5.3)

5.2 Welding geometry determination

Taking into account the geometry of the lid plate and its components de�ned in chapter 4,

the main welding points that de�ne the welding sequence of the process can be determined.

Looking at the 3D model of the part it is quickly observed that all the welds needed to

build the lid plate are straight lines which can be di�erentiated in three groups:

� Lateral - main plate welds

� Bulb - main plate welds

� Bulb - lateral plate welds

The �gure 5.5 shows an example of the di�erent types of welds on a lid plate model:

36

5.2. Welding geometry determination Aalborg University

Figure 5.5: Weld types

Knowing that all these weld paths are de�ned by lines, just by de�ning the starting and

the end points of each line would be enough to determine the welding. So, the �rst step is

to de�ne all the points required to obtain the weld geometry.

For the case of the bulb - main plate welds and the bulb - lateral plate welds the start and

end points of these lines are labelled as is shown in the next �gures:

(a) Bulb weld start points and left bulb -lateral weld points labelling

(b) Bulb weld end points and right bulb -lateral weld points labelling

Figure 5.6: Bulb welding points labelling

37


The welding of each bulb plate consist of two horizontal welds; front and back. They are

de�ned by two points that are coincident with the intersection of the bulb, lateral and

main plates. For example, the front bulb weld is de�ned by BulbStart and BulbEnd.

On the other hand, the welds between the lateral and the bulb plates are de�ned by two

vertical welds; front and back. The start point of these welds coincides with the end of

the lateral plate and the end point coincides with the start or end of the bulb welds. In

the case of the front left bulb - lateral weld, it is de�ned by the points LeftBulbLat and

BulbStart (see �gure 5.7a).

(a) Lateral plate weld start points la-belling

(b) Lateral plate weld end points la-belling

Figure 5.7: Lateral welding points labelling

On the other side, the lateral plates are welded on the both sides. The outer welds consist

of a single weld de�ned by an start and end point (LateralStart and LateralEnd). However,

the de�nition of the inner weld is completely di�erent. They are composed by multiple

segments between the start (InLateralStart) and the end (InLateralEnd) delimited by the

bulb plates.

So, to ful�l the right lateral weld the �rst segment is de�ned by InLateralStart and BulbEnd.

After that, all the segments delimited by bulb plates are de�ned by BackBulbEnd and

BulbEnd point of the next bulb plate. Finally, the last segment is de�ned by BackBulbEnd

point of the last bulb plate and InLateralEnd.

5.2.1 Intermediate points de�nition

Nevertheless, just with these points and the ones de�ned previously is not enough to carry

out a correct welding of the lid plate. Some intermediate points have to be designed to

avoid any possible collision between the welding tool and the working piece.

To ensure a correct transition from the front to the back weld of bulb plates, two

intermediate points are de�ned. This transition can start at LeftBulbLat point or at

RightBulbLat point, depending on how many passes are needed to complete the front

welding, but the de�nition of these two intermediate points is equivalent for both

cases. Figure 5.8 shows the case where the transition starts at LeftBulbLat and ends

at BackLeftBulbLat :

38


Figure 5.8: Examples of bulb weld transition intermediate points

Following �gure 5.8, in the case that the robot �nishes welding the front of the bulb plate

on the left side of it (LeftBulbLat), to carry out the transition to the back side of the plate

the sequence is the following one:

LeftBulbLat → BulbStartInter → BackBulbStartInter → BackLeftBulbLat

More transition points are required for the transition between lateral plate welds. In this

application, the transition between lateral plate welds happens when the right outer lateral

weld is carried out, ending at LateralEnd point of that plate. Then the robot has to move

to LateralEnd point of the other plate. To ensure that this transition is done correctly the

following intermediate points are de�ned:

Figure 5.9: Lateral weld transition intermediate points

39


So, by de�ning the LateralEndInter points the collision with both the lateral and bulb

plates is avoided.

5.2.2 Welding coordinates de�nition

Now that all the di�erent points required to de�ne all the welds have been de�nes, the

geometrical relations between their coordinates have to be de�ned. These relations will

help to de�ne all these points during the automatic robot program generation.

To state these geometrical relations, the Custom Properties de�ned in chapter 4 are used.

This way, when these properties are modi�ed in the 3D parametric model of the lid plate,

this modi�cation will be automatically translated to the geometrical relations between

weld points. So any change on the lid plate dimensions will mean a rede�nition of the weld

point coordinates to �t the new shape of the part.

Back bulb weld points

In the case of the back bulb weld points, a relation with the front weld point can be stated

knowing the bulb plate thickness (Bti) and the lid plate angle (α) (see �gure 5.10).

Figure 5.10: Front and back bulb points

Applying trigonometry and using the two Custom Properties, the translation from the

front to the back weld points can be expressed using the following equation:

Xback

YbackZback

=

Xfront

YfrontZfront

+

Bti∗ ±Bti · tanα

0

∗

+ Left,−Right (5.4)

The sign of the translation on the Y axis depends on the side of the bulb plate where the

point is situated. For the case of the start point (BackBulbStart), which is on the left side

of the plate, the translation will have a positive sign, because BackBulbStart point's Y

coordinate is bigger than the front point's (see �guere 5.10). On the other side, due to the

axes arrangement the sign of the translation for the end point will be negative.

40


Bulb - lateral weld points

As it was said at the beginning of the section, the start points of the bulb - lateral welds

coincide with the star or end point of the weld points. These welds consist on vertical

lines that have a length equal to the height of the lateral plate, which (remembering from

chapter 4) is a Custom Property (LateralHeight) of the 3D parametric model.

Knowing this, to obtain the points that de�ne the welds between the bulb and the lateral

plates the following translation on the Z direction is necessary:Xbulblat

YbulblatZbulblat

=

Xbulb

YbulbZbulb

+

0

0

LateralHeight

(5.5)

Bulb weld intermediate points

The intermediate points de�ned to avoid the collision of the torch with bulb plates each

time that it makes the transition from the front to the back weld of the bulb plate some

intermediate points can be related to the bulb weld point between whom they de�ne its

transition.

(a) Left view (b) Top view

Figure 5.11: Left and top views of a bulb plate with the intermediate points displayed

As can be seen in the example shown in �gures 5.12a and 5.12b, a translation in all the

axes has to be applied to obtain the coordinates of the intermediate points from the ones

from the bulb welds. To ensure that the robot won't collied against the bulb plate and

that this intermediate points are reallocated every time the lid plate model changes the

Custom Properties of the bulb height (Bhi) is used.

Xbulbinter

YbulbinterZbulbinter

=

Xbulb

YbulbZbulb

+

±Bh∗i±Bh∗∗i1, 5 ·Bhi

∗ + Front,−Back∗∗ +Right,−Left

(5.6)

41


In this case, as for the back bulb weld points, the sign of the Y and X changes depending

on the reference point that is being used to de�ne the coordinates of the intermediate

point.

On the one hand, the sign of the X translation is positive if the intermediate point is

related to a front weld point (BulbStart or BulbEnd) and negative if it is related to a back

one (BackBulbStart or BackBulbEnd). On the other, the translation in Y will be negative

if the intermediate point de�nes a transition on the left side of the bulb plate (related to

BulbStart or BackBulbStart) and positive if the point de�nes a transition on the right side

of the bulb plate (related to BulbEnd or BackBulbEnd).

Lateral weld intermediate points

The intermediate points needed to avoid the collision of the torch with lateral plates during

the transition from one lateral weld to the next one can be related to the end point of the

outer lateral welds.

(a) Left view (b) Top view

Figure 5.12: Left and top views of a bulb plate with the intermediate points displayed

This relation consists of a translation on the Y and Z axes. To ensure the correct relocation

of these points last bulb plate's height (Bh8)is used:

Xbulbinter

YbulbinterZbulbinter

=

Xbulb

YbulbZbulb

+

0

Bh81, 5 ·Bh8

(5.7)

Bulb plate transition intermediate points

One �nal group of intermediate points is de�ned to ensure a good transition between bulb

plates. Once the welding of one plate has been carried out the tool has to move to the

next one without colliding with any of the bulb plate or the lateral plate. To ensure this

the following points are de�ned:

42

5.3. Welding parameters de�nition Aalborg University

Figure 5.13: Bulb plate transition intermediate point

This intermediate points' coordinates are related to the back bulb weld points in a similar

way to the transition points between the front and back welding of the plate. The

translation is de�ne by the same equation, but the Z translation is smaller because there

is no need to avoid any bulb plate from above.

Xinterbulb

YinterbulbZinterbulb

=

Xbulb

YbulbZbulb

+

Bhi±Bh∗i

LateralHeight

∗ +Right,−Left (5.8)

5.3 Welding parameters de�nition

Once described the structure of the robot program, there are a set of parameters that have

to be de�ned or calculated for every weld that the robot has to carry out to produce the

selected lid model:

� Welding speed

� Welding voltage

� Welding material feed speed

� Welding angles and tool orientation

The determination of these parameters is not an straight forward process and depend

on an important number of variables. However, one of the variables that most in�uences

these parameters (except the welding angle) is the thickness of the plate that is going to be

welded. So, as a simpli�cation, in the following points the relation between the parameters

and the plate thickness will be set. (See Appendix B)

43


Table 5.1: Welding parameters for di�erent plate thicknesses, [CSFE, 2006]

Plate thickness Voltage Wire feed Travel speed

[mm] [V] [mm/s] [mm/s]

7 20 45 8

8 22 45 8

9 24 50 7

10 26 50 7

11 24 60 7

11.5 26 65 7

12 24 75 6

13 26 85 6

14 28 90 6

All the welds that are carried out to manufacture a lid plate consist of joining 90◦ �llets.

The main angles that form the tool and the working piece in this kind of welding are shown

in �gure 5.14:

Figure 5.14: Main welding angles, Source: WeldCorTM

Work angle: Is the angle of less than 90◦ between a line perpendicular to the major

work piece surface and the plane determined by the electrode axis and the weld axis.

Typically this angle is set to 45◦, but any possible collision has to be avoided

Travel angles: Push and Drag angles are the maximum angles that the tool forms

when it travels through the welding path with respect to the perpendicular position

of the tool to the welding path.

The determination of the tool orientation depends on which type of weld is being carry

out, so it will be analyse with more detail on the next section.

44

5.4. Tool orientation de�nition Aalborg University

5.4 Tool orientation de�nition

Once the welding points coordinates have been correctly de�ne the tool orientation for each

one of the points has to be set. This is critical point on the robot movement de�nition

to ensure the avoidance of collisions and the optimal welding process for a given set of

parameters.

Figure 5.15: Tool orientation during right lateral plate welding

For this purpose, a complex Robot Path Planning algorithm has to be implemented. This

process consist of breaking down the desired movement task into discrete motions that

satisfy movement constraints and makes possible to optimize some aspect of the movement;

tool orientation in this case. However, this task is beyond the scope of this project and

would be an interesting future work to optimize this solution.

In this project, the de�nition of the tool orientation has been set manually, checking

orientations that ensure no collisions or singular points and are close to the desired welding

angles. Next table shows the tool orientations chosen for every weld point type:

Table 5.2: Possible tool orientation

Weld pointTool orientation [ ◦ ]

Roll ( φ ) Pitch ( θ ) Yaw ( ψ )

Right Lateral 20 -30 -90

Left Lateral 15 45 -90

Bulb Start 18 -20 -90

Bulb End 0 60 -120

Left Bulb Lateral 20 -40 -93

Right Bulb Lateral 0 60 -120

Back Bulb Start -45 0 -90

Back Bulb End -10 60 -80

Back Left Bulb Lateral -45 0 -90

Back Right Bulb Lateral -10 60 -80

45


Knowing all the angles all the rotation matrices can be built following the next structure

obtained from multiplying the three rotation matrices of each turn in Yaw - Pitch - Roll

order:

RT = RTψ ·RTθ ·RTφ =

c(ψ)c(θ) s(φ)s(θ)c(ψ)− c(φ)s(ψ) s(φ)s(ψ) + c(φ)s(θ)c(ψ)

c(θ)s(ψ) c(φ)c(ψ) + s(φ)s(θ)s(ψ) c(φ)s(θ)s(ψ)− s(φ)c(ψ)−s(θ) s(φ)c(θ) c(φ)c(θ)

For an easier manipulation of the rotation matrix of each orientation and because of

RobotStudio requirements, the corresponding quaternion would be used to represent all

the orientations. The structure of the rotation matrix can be de�ned the following way:

RT =

x1 y1 z1x2 y2 z2x3 y3 z3

(5.9)

The components of the quaternions can be calculated from this rotation matrix using the

following expressions:

q1 =

√x1 + y2 + z3 + 1

2

q2 =

√x1 − y2 − z3 + 1

2sign(q2) = sign(y3 − z2)

q3 =

√y2 − x1 − z3 + 1

2sign(q3) = sign(z1 − x3)

q4 =

√z3 − x1 − y2 + 1

2sign(q4) = sign(x2 − y1)

So, the value of the quaternion for each tool orientation is displayed on the next table:

Table 5.3: Quaternion of every possible tool orientation

Weld pointQuaternion

q1 q2 q3 q4

Right Lateral 0,707106 0 -0,241844 -0,664463

Left Lateral 0,612372 0,353553 0,183013 -0,683013

Bulb Start 0,706999 -0,012341 -0,230211 -0,668583

Bulb End 0,433013 0,433013 0,25 -0,75

Left Bulb Lateral 0,680096 -0,132001 -0,350218 -0,630391

Right Bulb Lateral 0,433013 0,433013 0,25 -0,75

Back Bulb Start 0,653281 -0,270598 0,270598 -0,653281

Back Bulb End 0,688901 0,262350 0,430082 -0,521169

Back Left Bulb Lateral 0,653281 -0,653281 0,270598 -0,270598

Back Right Bulb Lateral 0,688901 -0,521169 0,430082 0,262350

46

5.5. Welding sequence de�nition Aalborg University

5.5 Welding sequence de�nition

Once all the welding coordinates and paths have been de�ned the welding sequence has

to be set. Taking into account the disposition of the lid plate in the working area, the

closest weld to the Home position of the mechanism is the right lateral - main plate and

consequently the �rst weld to be carried out. After this �rst weld, the welds between bulb

plates and main and lateral plates would be carried out, starting from the most inner bulb

plate as is described in �gure 5.16:

Figure 5.16: Welding path representation in RobotStudio

5.5.1 Number of passes de�nition

Depending on the thickness of the plates that have to be welded one or more passes would

be necessary to ensure that all the required welding material is correctly deposited. To

determine the number of passes needed for every bulb plate thickness the data from table

5.4 has to be taken into account.

First the weld cross section area (Aw) has to be de�ned to determine how much welding

material is needed for every type of weld. To calculate this area the weld throat has to be

de�ned. In this case, all the welds consist of "T" shape �llet welds like the one shown in

�gure 5.17:

Figure 5.17: Fillet welds, Source: mitcalc.com

The �llet weld thickness (a) is chosen depending on the used material and thickness of the

welded parts. As a recommendation, the following expression can be followed to determine

47


the weld thickness:

amin ≥ tmin (5.10)

Knowing this and considering a welding angle of 45 the weld throat area can be calculated

as:

Aw = a2 = t2min (5.11)

With the required welding material cross area and the density of the welding material

(typically 7850 kg/m3) the target mass that has to deposited per meter of welding can

be calculated. After that, considering a deposit rate of 8 kg/h for an automatic GMAW

(see deposition rate table 2.1) and the speed of every type of welding the mass of welding

material that the robot is able to deposit is determined. Then, just by dividing these two

values the required number of passes is obtained. The following table show all these values

for the di�erent plate thicknesses:

Table 5.4: Welding passes calculation

Plate Travel Target Deposited

thickness speed Aw mass mass Passes

[mm] [mm/s] [mm2] [kg/m] [kg/m]

7 8 4.9 0.31 0.28 1

8 8 6.4 0.5 0.28 2

9 7 8.1 0.64 0.31 3

10 7 10 0.79 0.31 3

11 7 12.1 0.95 0.31 3

11.5 7 13.2 1.03 0.31 3

12 6 14.4 1.13 0.37 3

13 6 16.9 1.32 0.37 4

14 6 19.6 1.54 0.37 4

5.5.2 Outer lateral plate welding sequence

The lateral plates of all the lid plate models studied in this project have a thickness of 10

mm, so based on table 5.4, three passes are needed to properly weld them to the main

plate. Taking this into account, the same sequence can be de�ned for the outer welding of

the lateral plates of all the lid plate models.This sequence is represented in the following

�gure:

48

5.5. Welding sequence de�nition Aalborg University

Figure 5.18: Outer lateral plate welding sequence

1. Start on the LateralStartInter point of the right lateral plate and move to Lateral-

Start to start the welding.

2. Carry out three welding passes, ending at LateralEnd of the right plate.

3. Follow the transition sequence using the LateralEndInter points of the lateral plates

described on section 5.2.2 to reach LateralEnd point of the left lateral plate and start

the second welding.

4. Carry out three welding passes, ending at LateralStart of the left plate and move to

the LateralStartInter point to �nish with the outer weld of the lateral plates.

5.5.3 Bulb plate and inner lateral plate welding sequence

All the bulb welding sequences start with the front welds. The thickness of the bulb plate

determines the number of passes that are needed. Each one of these passes will follow a

left to right or a right to left sequence like the ones described bellow:

Left to Right Sequence

� LeftBulbLat� BulbStart� BulbEnd� RightBulbLat

Right to Left Sequence

� RightBulbLat� BulbEnd� BulbStart� LeftBulbLat

These two sequences alternate until the required number of passes are ful�lled. Once the

front welds have been �nished the transition to the back side of the plate is carried out.

This transition is de�ned by the intermediate points determined in section 5.2.2 and will

situate the robot at the beginning of one of the back bulb - lateral plate welds.

Once the robot is situated on the back side of the bulb plate, both the back bulb weld and

the inner lateral weld segment are carried out. Under this lines an example of this welding

sequence is described:

49


Figure 5.19: Bulb plate and inner lateral plate welding sequence

1. After the transition to the back side of the bulb plate the robot will be situated on

the beginning of the back bulb - lateral weld (BackLeftBulbLat in this case).

2. First, the bulb left bulb - lateral weld is carried out, with the robot ending at the

BackBulbStart point.

3. Then, all the passes needed for the left inner lateral weld segment are carried out.

This segment is de�ned by the BackBulbStart point of the �rst bulb plate and the

BulbStart point of the second one.

4. The last operation will end at the BulbStart point of the second plate, so to ensure

a correct return transition to the �rst one, the robot will move through the LeftIn-

terBulb point to reach the BackBulbStart point of the �rst bulb plate.

5. After that, the �rst pass of the remaining bulb and bulb - lateral welds are carried

out, �nishing at the BackRightBulbLat point.

6. At this point, the same sequence followed for the left inner lateral segment weld is

followed.

7. Finally, the remaining passes of the bulb and bulb - lateral welds are carried out to

�nish the welding of the bulb plate.

50

Lid Plate Generator 6The parametrization of the lid plate design and the interaction with the 3D model to

obtain all the manufacturing data is possible thanks to a SolidWorks add-in that has

been called Lid Plate Generator. The development of this add-in starts from SolidDNA,

a SolidWorks API that makes the programming of add-ins easier and intuitive developed

by Luke Malpass.

The Lid Plate Generator is able of scaling a 3D base model of the lid plate based on what

was stated in chapter 4 and then generate a RAPID robot program with the information

obtained from the model that has to be loaded to RobotStudio to simulate the welding

process of the di�erent lid pate models presented in this project.

Figure 6.1: Lid Plate Generator task pane

51

VT3 6. Lid Plate Generator

6.1 Parametric modelling

Remembering all that was said at the conclusion of chapter 4; once the base model has

been de�ned with all the equations and relations with the Custom Properties stated, the

user only has to correctly set the values of those properties to generate a valid 3D model of

any of the available lid plate models. So, from the parametric modelling point of view, the

main objective of the Lid Plate Generator is to ease the modi�cation of those properties

by the user to generate valid lid plate models. For this purpose, �rst a task pane has been

created that follows the next logic:

Figure 6.2: Task pane logic

Following the �ow diagram of �gure 6.2, the �rst that the user has to do to access the full

functionality of the add-in is to select a valid base model like the one described before.

Until the user does this action, the task pane of the add-in will show the display shown in

�gure 6.3a and once a valid model has been uploaded to SolidWorks, the displayed task

pane will be the one shown in 6.3b.

(a) Start view of the task pane (b) Fully operative task pane

Figure 6.3: Add-in task pane's views

52

6.1. Parametric modelling Aalborg University

As it can be seen on the task pane shown in �gure 6.3b, the user has to choose the lid plate

design that wants to generate from all the available models that are listed on the combo

box. Once the desired model has been selected, all the text boxes below are �lled with the

geometrical information of the selected lid plate design. Then, as the �ow diagram shown

in �gure 6.2, each of the buttons in �gure 6.3b enable one of the three options that the

user has:

1. Generate: This button enables the introduction of changes on the base model.

Once it is clicked, all the values shown in the text boxes will be translated to the

base model scaling and modifying it to obtain the 3D model.

2. Reset: By clicking this button the values of the driving parameters are set to the

ones of the base model.

3. Save: The user can save the desired 3D model of the lid plate by clicking this button.

It is interesting to analyse in detail the logic that the add-in follows when the Generate

button is clicked. The following �ow diagram shows clearly this logic:

Figure 6.4: Generate logic �ow diagram

So, following the �ow diagram in �gure 6.4, the �rst thing that the add-in does is to get the

lid plate model selected by the user from the combo box. After that, the lid plate model is

used to determine the value of Custom Properties that do not need further information (as

the inner and outer diameters) and the set of bulb plates that has to be installed for that

particular model from the Excel data base. With this new information the last parameters

are de�ne, such as the ones that de�ne the linear relation of the disposition of the lid

plates. Finally, all the custom properties are set and the model is rebuild to generate the

desired lid plate design.

When the user has generated the desired 3D model for a certain application all the

dimensions of the components of the lid plate would have been de�ned too. With the 3D

53


model of the desired lid plate fully de�ne, it can be used to obtain very valuable information

to de�ne the welding robot program that would carry out all the welds required. So, the

add-in is extended to be able to interact with the SolidWorks 3D model.

6.2 Interaction with the lid plate 3D model

The �rst problem that arises while de�ning the welding process of the lid plate is the

de�nition of the welding paths. To be able to overcome this problem, another functionality

has been added to the SolidWorks add-in described on the previous section. If all the

welding paths are de�ned on the base model, they would be rede�ned and adjusted to the

scaled model of the lid plate, thanks to the parametric design of the lid plate.

Consequently, all the welding paths stated previously are de�ned on the base model of the

lid plate using a sketch. This sketch is formed by lines that match the joints between the

di�erent plates that form the lid plate. As the start and the end points of these lines are

referenced to points belonging to the plates, when these components are scaled, all the

lines will change its size and coordinates too.

Figure 6.5: Lid plate base model with the welding paths de�ned in blue

Once all the lines needed to de�ne the welding paths are drawn, a new button is added

to the SolidWorks add-in to enable the creation of a report in which all the coordinates of

the weld lines' start and end points are shown. To do this, the user has to select the Edit

Sketch option to access the lines that de�ne the welding paths and select all the lines from

which the coordinates of the start and end points are desired to get.

The next step is simply to press the Get button next to Sketch coordinates in the task

pane to make the add-in produce the desired report and save it in whatever �le the user

chooses. This report would contain all the coordinates needed to de�ne the welding paths

to manufacture the chosen lid plate design.

54

6.2. Interaction with the lid plate 3D model Aalborg University

Figure 6.6: Get button to obtain the sketch coordinates in the task pane

An example of a report generated from a scaled model cab be seen bellow these lines:

Lateral plate weld 1

Start point: 2005.20581632308 623.417453471473 15

End point: 5671.15956207984 1957.71549712362 15

...

Left Bulb Lateral plate weld 1

2900 933.133235537259 100

Bulb plate weld 1

Start point: 2900 933.133235537259 15

End point: 2900 -933.133235537259 15

Right Bulb Lateral plate weld 1

2900 -933.133235537259 100

...

It is important to remember that all these coordinates are referred to and origin placed

on the center of the inner diameter of the lid plate. Furthermore, looking at �gure 6.5 it

can be realized that only the front welds of the bulb plates are represented in the sketch.

So, all the relations described in sections 5.1.2 and 5.3 have to be applied to obtain all the

points required for the de�nition of the welding process.

55


6.3 RAPID program generation

Remembering what was set on the project goals (chapter 3):

"With all the data from the previous steps, a robot programming will be carried out in order

to make the manufacturing process completely automatic. This programming will be

automatically generated and uploaded to ABB's o�-line simulation and programming

software; RobotStudio.[...]"

To ful�l this objective, the Lid Plate Generator analyses all the data generated from the

interaction with the parametrized lid plate model and all the characteristics of the welding

process de�ned in chapter 5 to be able to automatically generate a welding robot program.

Once the desired lid plate 3D model has been generated and saved, the user has to click

the Generate RAPID program button from the add-in's task pane. By doing this the

add-in will generate all the documents required by RobotStudio to de�ne a welding robot

program and will ask the user the location to save them.

The Lid Plate Generator generates all the �les, con�gurations and instructions following

the structures speci�ed by RobotStudio. For further information about all this features see

Appendix C.

6.3.1 Weld data de�nition

The �rst thing that the Lid Plate Generator does during the robot program generation is

the de�nition of the seam and weld data following the structure stated in section C.1 of

Appendix C. To do this, it follows the next logic:

Figure 6.7: Weld data de�nition logic

A weld data has to be created for every di�erent plate thickness that has to be welded.

So, the add-in checks the di�erent thicknesses that are present on the selected lid plate

model and the collects all the parameters for each case from the Bulb Plate database to

write them in the RAPID �les.

6.3.2 Robot target generation

The next step that the add-in takes after de�ning the weld data is to generate robot targets

from the sketch lines de�ned on the lid plate model. For each selected line it follows the

next �ow diagram:

56

6.3. RAPID program generation Aalborg University

Figure 6.8: Target line generation logic

First, it checks if the selected line represents a bulb or a lateral weld. If the X coordinate of

the start point is equal to the X coordinate of the end point it will mean that the selected

line is a bulb weld. In the case of the bulb welds, the add-in de�nes both front and back

welds applying the relations described in section 5.2. Additionally, all the intermediate

points related to each weld are de�ned.

Once all the points coordinates have been obtained from the sketch line they are translated

to the welding cell reference system applying the translation described in section 5.1.2.

Then all the additional data required by RobotStudio to complete a robot target is

generated:

� Tool orientation

� Robot con�guration

� External axes position

On the one hand, the tool orientation depends on the type of point and is obtained on the

57


consultation of the database by stating the quartenion that de�nes the rotation of the tool

with respect to the origin frame. All the quartenions can be found in table 5.3.

On the other hand, RobotStudio allows to Autocon�gure any path de�ned to the

con�guration that best suits the robot. So, for every welding point the robot con�guration

is set to [-1,0,-1,0], taking into account that once the welding path has been Autocon�gured

they might change to a more suitable con�gurations.

Finally, for the robot to be able to reach all the welding points the position of the XY

crane has to be de�ned for each target. To ensure a good reachability to all points and

to maintain the robot far from critical con�gurations, the position of the two axes of the

crane are calculated following the next expression:

[Xcrane

Ycrane

]=

[Xpoint

Ypoint

]·

[−1 0

0 1

]+

[0

−1000

](6.1)

It is important to take into account that due to the disposition of the coordinates axes of

the station, all the X coordinates of the welding points will have a negative value. However,

the position of the crane axes needs to have a positive value.That is the reason why the

position of the X axes for every point of the crane is obtain by changing the sign of the

point's X coordinate.

6.3.3 Move instruction and sequence generation

RobotStudio provides four di�erent instructions to de�ne the di�erent movements between

targets that �t this welding application (for a more detailed description go to Appendix

C):

� MoveL: de�nes a normal movement between two targets.

� ArcLStart: de�nes a movement to a target where the welding torch is going turn on.

� ArcL: de�nes the movement between intermediate welding targets maintaining the

welding torch on.

� ArcLEnd: de�nes the movement to a target where the welding torch is going to

turn o�.

The de�nition of each instruction is related with the type of target towards which the

robot has to move (see section 5.2.2) and the sequence needed to perform each weld (see

section 5.5). This de�nition is done after the determination of all the robot targets and

follows the next logic:

58

6.4. Welding characteristics Aalborg University

Figure 6.9: Movement instruction generation logic

Following the �ow diagram from �gure 6.9, when the add-in �nishes generating all the

robot targets, it reads again the sketch and checks every sketch line to see what type of

weld it represents.

Once the type of weld is determined, the thickness of the plate that is going to be welded

is obtained. This value will determine the number of passes and the parameters of the

instructions, like the welding voltage or the speed. All this data is required to determine

the sequence of targets that the welding robot has to follow to ful�l that weld. Finally,

this sequence is programmed by the correct sort of the moving and welding instructions

de�ned before to build the robot program.

6.4 Welding characteristics

The last functionality added to the Lid Plate Generator is the determination of the total

welding length and welding material volume needed to produce the desired lid plate model.

This data is fundamental to carry out the economic study of each model of lid plate because

it a�ects directly the welding time and the welding material cost.

To obtain the length and volume, the following logic is followed:

59


Figure 6.10: Welding characteristics obtaining logic

The user can select as many sketch lines as wanted to de�ne the welding length and volume

to be calculated. The add-in reads all the lines and determines what kind of weld they

represent. Knowing this, the plate thickness and weld length are obtained. With this

values the volume of welding material can be obtained following the expression described

in section 5.5.

60

Economic study 7To determine the bene�ts of the automation of the lid plate manufacturing process an

economic study has to be carried out. Here the productivity and e�ciency improvements

will be analyse to see if is worth it to make all the investment on the automatic welding

station. Additionally, the in�uence of design variation on the manufacturing cost will be

analysed. How the welding cost varies in di�erent lid plate solutions for a same applications.

7.1 Automatic welding cost

To compare the automatic solution proposed in this project and the traditional welding

method used until now all the costs will be analysed.

7.1.1 Welding time calculation

To determine the welding time needed to manufacture the lid plate the �rst thing to do is

to determine the amount of material needed to carry out all the welds. The total volume

of welding material (V ) is calculated by multiplying the length of each weld (L) times its

weld throat area (Aw) as is shown in equation 7.1:

V = L ·Aw (7.1)

To calculate the weld throat area the weld cross section has to be de�ned. This parameter

is obtained using the same expression stated on the previous section for "T" shape �llet

welds with a determine thickness (a) like the one shown in �gure 5.17.

So, knowing the volume of welding material it is possible to calculate the mass of material

required for the welding process (Md) by multiplying the volume times the density of the

welding material (ρ):

Md = V · ρ (7.2)

However, the consumption of welding material would be bigger due to di�erent material

losses during the welding process. The real welding material mass (Mw) is calculated

correcting the previous value:

Mw =Md · 1.8 (7.3)

Knowing the required mass, to calculate the time needed to deposit all the welding material

(tarc) can calculated by the expression given in equation 7.4:

tarc =Mw

dr(7.4)

61

VT3 7. Economic study

The deposit rate (dr) can be obtained from table 2.1 from section 2.3. Taking into

account that the welding technology used for the manufacturing of lid plates is Gas Metal

Arc Welding (GMAW), for the cost calculation the deposit rate would be considered to be

8 kg/h.

Finally, to calculate the real time needed to produce each lid plate the e�ciency of the

welder has to be added to the previous time value. The e�ciency of each welding method

is stated in table 7.1:

Table 7.1: Welding e�ciency for di�erent welding methods [León, 2013]

Welding method Welder e�ciency, φ [%]

Manual 5 - 30

Semiautomatic 10 - 60

Automatic 50 - 95

So, the total welding time is obtained by the expression 7.5:

tt =tarcφ

(7.5)

7.1.2 Labour cost

Labour cost can be easily obtain by multiplying the total welding time (tt) by the cost per

hour of a welder:

CL = tarc ·Chφ

(7.6)

As it can be seen in equation 7.6, this value of the labor cost strongly depends on the

welding method used in the manufacturing process.

7.1.3 Electrode cost

To calculate the electrode cost the number of electrodes consumed during all the welding

process has to be determined. This value is obtained by multiplying the price of each

kilogram of electrode (Cel) times the total mass of welding material used (Md). However,

this value has to be modi�ed by the deposition e�ciency factor (ψ):

CEl =Md ·Celψ

(7.7)

Deposition e�ciency depends mainly on the welding technology that is being used. Table

7.2 shows the typical values of ψ for the most common welding technologies:

Table 7.2: Deposition e�ciency factor for di�erent welding methods [León, 2013]

Welding technology Deposition e�ciency factor, ψ [%]

SAW 95 - 100

GMAW 90 - 95

FCAW 80 -85

62

7.1. Automatic welding cost Aalborg University

7.1.4 Energy cost

The energy cost of the welding process is calculated by multiplying the system's power

consumption (P) times the time that the torch is welding (tarc) and the cost of energy (cE)

in ¿/KWh. Additionally, the e�ciency of the welding technology has to be applied to the

expression by the means of the deposition e�ciency.

CE = P · tarc ·cEφ

(7.8)

7.1.5 Total cost comparison

To be able to compare the traditional welding process and the designed automatic solution

all the cost's items and the productivity have to be calculated. To obtain the total cost of

the welding process all the cost items described on the previous points have to be added:

CT = CL + CE + CEl (7.9)

As an example, the cost of the manufacturing of the lid plate base model will be studied.

For both welding techniques there is a set of process parameters that have to be de�ned:

Table 7.3: Process parameters

Parameter Value

Torch Power 6.6 KW

dr 10 kg/h

ψ 90 %

The weld cross section is the same, just like the total welding length. With these values

the total welding material mass and the arc time can be determined. Additionally, the

unitary costs of every cost item have to be de�ned. The values of these parameters are

shown in table 7.4:

Table 7.4: Welding geometry

Parameter Value

L 40,0339 m

V 0,0026 m3

Mw 20,44 kg

tarc 4,6 h/lidplate

Ch 50 ¿/h

Cel 1,2 ¿/kg

ce 0,14 ¿/KWh

With all this data the cost breakdown can be calculated for each welding technique. The

results are shown in table 7.5:

63


Table 7.5: Welding time and cost comparison

Manual welding Automatic welding

φ 30% 65%

Welding time 15,33 h 7,08 h

Labor cost, CL 766,5 353,8

Electrode cost, CEl 53,75 53,75

Energy cost, CE 14 6,5

Total cost, CT 834,25¿ 414,05¿

As can be seen in table 7.5, the great di�erence of e�ciency between the automatic and

the manual is the responsible of the drastic reduction on the welding time when the robotic

solution is used. This fact a�ect directly the labour cost, which is the most important cost

item.

The main conclusion that can be taken from this economic comparison is that the

important reduction on the welding cost of the lid plate makes the automatic solution

presented in this project a very interesting action to carry out in order to reduce the overall

cost of the Mono Bucket and consequently the LCOE of the O�shore Wind technology.

7.2 Cost - design variability

Once shown the improvement on the welding process cost, it is interesting to see how the

cost changes depending on which model is manufactured. As it was said in chapter 4, for

every application there are di�erent available models of the Mono Bucket that can ful�l

the mechanical requirements and be possible options. That is why it is interesting to see

which is the best choice from the welding cost point of view.

To carry out this comparison the same procedure described in section 7.1 will be followed

for every available lid plate model. The all the costs breakdowns and times calculated are

displayed on table D.1 on Appendix D.

7.2.1 Cost variation with pressure

First the variation of the cost with the pressure that the complete lid has to withstand

is studied. As this pressure increases, for a same Mono Bucket, mechanical stresses that

each bulb plate has to withstand would increase. So, for higher pressure applications, the

thickness and height of the bulb plates arrange on top of the main plate would increase.

This increase in the thickness of the plates would mean that the amount of welding material

needed to ensure a correct welding would increase too. Consequently, the time required

to ful�l all the welding process would increase to, so would do the labour, electrode and

energy costs. This phenomenon can be seen in the graphs shown in �gure 7.1:

64

7.2. Cost - design variability Aalborg University

Figure 7.1: Cost variation with lid pressure

In the graphs of �gure 7.1 it can be seen that the increase of the total welding cost is not the

same for the di�erent diameters of the Mono Bucket. This is mainly due to the bulb plate

selection that the FastBertha does for every model. The limited bulb thicknesses available

means that some times the picked bulb plate model is thicker than what is required, so

the weld needed to join that plate would be bigger than needed. This di�erence on the

bulb plate thicknesses can be seen in table 4.3.

This is specially signi�cant for the 10 meter diameter Bucket. The 300 KPa and 400

Kpa model's welding cost is very similar because, even if the bulb plates are higher, the

thicknesses are maintained quite similar.

65


7.2.2 Cost variation with lid angle

On the other hand, it is interesting to analyse what lid angle makes cheaper to produce

a hole Mono Bucket lid. Although the welding cost to produce a lid plate model with a

wider angle would be bigger, the number of lid plates needed to complete the entire lid of

the Mono Bucket would decrease. For this reason, instead of analysing the welding cost

per lid plate, the cost of the entire lid would be analysed to carry out a proper comparison

and determine the cheaper solution from the welding cost point of view.

From all the available models obtained with Universal Foundation's tool, only 10 and 12

meter diameter models have di�erent lid angle models, always for lid pressure of 400 KPa.

So, only for these two cases the cost variation with the lid angle will be carried out.

Figure 7.2: Cost variation with lid angle (Do = 10 m)

For the case of a Mono Bucket with a diameter of 10 meters, it can be seen in �gure 7.2

that the best solution from the welding cost point of view is to make use of a lid plate

design with an angle of 12◦, what means that 15 lid plates would be needed to complete

the lid of the Bucket.

Another interesting fact that can be seen in �gure 7.2 is that a lid compose by 20◦ lid plate

models is cheaper to weld than one form by plates of 15◦. These happens because, even if

it is cheaper to produce a single 15◦ plate than a 20◦ one, the prize is not low enough to

produce a complete lid of 12 lid plates of 15◦ rather than one with 8 of 20◦.

66

7.3. Cost variation with diameter Aalborg University

Figure 7.3: Cost variation with lid angle (Do = 12 m)

As for the 10 meter Mono Bucket, the cheapest model to weld for the 12 meter one is the

one of 12◦. However, the di�erence between this model and the one of 15◦ is very small, so

other aspects from the total cost (like the material cost or the transportation) can easily

incline the weighing on the behalf of the 15◦ lid plate.

It is important to underline what was said in the previous section concerning the in�uence

of the available bulb plates. As the lid angle increases, the number of lid plates needed to

install would be reduced but the stresses that they would have to undertake would increase

too. This means that the bulb plates to be installed would be thicker and more costly to

weld. If the chosen bulb plates' thickness is bigger that the requirement, the cost would

increase even more. This is mainly the reason why the lid plate models with wider lid

angles are more expensive to weld.

7.3 Cost variation with diameter

Finally, the cost variation with the Mono Bucket diameter is analysed for di�erent

operating lid pressures. In this case, the available models only have been designed for

three di�erent lid pressures (200, 300 and 400 KPa) which represent di�erent working

environments where the Mono Bucket can be installed.

67


Figure 7.4: Cost variation with diameter

As it can be seen in the graphs of �gure 7.4, for all possible lid pressure the best option to

reduce the welding cost is to manufacture the lid of the Mono Bucket with the lid plates

of the smallest diameter possible. The longer welding distances and thicker bulb plates

make the bigger diameter lid plate models to be more expensive.

68

Conclusion andperspectives 8

8.1 Conclusion

In conclusion, the main achievements of this project are:

� Development of a parametric design of a set of lid plate models.

� De�nition of an automatic welding process for lid plates based on a robot arm

mounted on a gantry crane.

� Development of an Add-in for a fast parametrization of lid plate models and RAPID

robot program generation for an automatic welding process.

� Proof of the economic bene�ts of using an automatic welding process to produce the

parametrized set of lid plate models.

The parametrization of the design makes it much faster and easier to develop 3D designs

of the di�erent lid plate models available for this project. What is more thanks to the

easy resizing of the base model the sketches that de�ne the weld paths are simultaneously

correctly resized as weld. This fact is key to automatically generate the robot program no

matter the lid plate design wanted to be manufacture.

Checking the project goals stated at the beginning of the project:

X Design of a 3D parametric model of the lid plate

Development of an automatic manufacturing data generation tool

X Automatic welding coordinates de�nition.

X Automatic welding sequence de�nition.

Automatic welding parameters de�nition

X Average welding parameters de�nition.

X Optimization of the welding parameters

X De�nition of an automatic manufacturing process based on a robotic arm

69

VT3 8. Conclusion and perspectives

The only sub-objective that has not be tackled in this project is the optimization of the

welding parameters such as the welding speed or voltage. These parameters have been

set to average values for this kind of welding processes to be able to generate the robot

program and simulate it even if it is not the most optimal one.

This project has proved that an automatic welding process is a recommendable way of

reducing the manufacturing cost of the lid plates. So, it can be concluded that this is a

very interesting solution to reduce the LCOE of O�shore Wind Energy by reducing the

cost of the foundation.

In conclusion, this project o�ers a very interesting tool to easily work in the design of

di�erent lid plate models and automatically obtain the welding robot program to simulate

and posteriorly weld the desired lid plate model. However, there is further work and

optimization that would be needed to carry out before implementing this design and

manufacturing solution on a real application.

8.2 Further work

Even if the Lid Plate Generator is a fully functional tool, it needs some optimization to

be able to use it to de�ne real welding processes of lid plates. This optimization should be

centred specially on a more detailed de�nition of welding parameters and an enlargement

of the set of available lid plate models.

As it was commented on chapter 5, a Robot Path Planning algorithm has to be

implemented to optimize the tool orientation. This is a critical fact to ensure that no

collisions happen during the welding process of the lid plate, while the robot maintains

the best orientation from the welding characteristics point of view. This, will strongly

in�uence the other welding parameters, so it should be the �rst thing to do to improve

this solution.

What is more, a better and more detailed analysis of the welding parameters have to be

carried out. On the one hand, it is interesting to analyse how the continuous orientation

change of the welding torch a�ect the quality of the welds to see if this parameter has

to be rede�ned. On the other hand, a proper tuning of the welding parameters, such as

voltage, feed rate and speed, is very necessary to ensure that the quality of the welds. For

this purpose some welding tests would be necessary with plates of the sections present on

the di�erent lid plate models and the same welding equipment to be installed on the �nal

application.

Additionally, the available lid plate model data base should be extended to be able to use

this solution for a wider set of Mono Bucket designs. It would be specially interesting

to carry out the parametric design of lid plates with a number of bulb plates di�erent

from 8. This plates have proved to be a very determining factor of the welding time and,

consequently, of the welding cost of every lid plate model. So, after developing a parametric

design for this lid plates models a new economic study should be carried out to see the

in�uence of the number of bulb plates on the cost breakdown.

70

List of Figures

1.1 Wind power in Denmark [Neslen, 2016] . . . . . . . . . . . . . . . . . . . . . . 2

1.2 Annual o�shore and onshore wind installations (MW) [Europe, 2016] . . . . . . 3

1.3 LCOE for all primary energy sources, Source: Siemens . . . . . . . . . . . . . . 4

1.4 Capital cost breakdowns for typical onshore and o�shore wind systems [IRENA,

2012] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.5 Monopile foundation components, Source: 4CO�shore . . . . . . . . . . . . . . 5

1.6 Tripod foundation components, Source: 4CO�shore . . . . . . . . . . . . . . . . 5

1.7 Jacket foundation components, Source: 4CO�shore . . . . . . . . . . . . . . . . 6

1.8 Gravity based foundation components, Source: 4CO�shore . . . . . . . . . . . . 6

1.9 Current o�shore wind foundation type distribution, Source: WEU . . . . . . . 7

1.10 Suction Bucket working principle, Source: Universal Foundation . . . . . . . . 8

1.11 Mono Bucket, Source: LEEDCo . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.12 Lifting of a jacket structure with suction buckets, Source: DONG Energy . . . 9

2.1 Exploded view of a suction bucket [Villumsen, 2017] . . . . . . . . . . . . . . . 11

2.2 Depth variation in the London Array wind farm area, [H. Burningham, 2008] . 12

2.3 Suction Bucket manufacturing process . . . . . . . . . . . . . . . . . . . . . . . 13

2.4 Welding paths types for the manufacturing of the Suction Bucket [Villumsen,

2017] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.5 Estimated cost of a single suction bucket [Villumsen, 2017] . . . . . . . . . . . . 15

3.1 Project �ow diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.1 FastBertha tool task pane, Source: Universal Foundation . . . . . . . . . . . . 19

4.2 Geometrical parameters of the main plate . . . . . . . . . . . . . . . . . . . . . 21

4.3 Geometrical parameters of the main plate . . . . . . . . . . . . . . . . . . . . . 21

4.4 Lateral plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4.5 Bulb plates layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.6 Bulb iron section and main dimensions . . . . . . . . . . . . . . . . . . . . . . . 23

4.7 FastBertha lid plate results example, Source: Universal Foundation . . . . . . . 24

4.8 Geometrical parameters of the lid plate . . . . . . . . . . . . . . . . . . . . . . 26

4.9 Distance between bulb plates relation . . . . . . . . . . . . . . . . . . . . . . . 27

4.10 Distance between bulb plates relation Do = 10 m, α 6= 20◦ . . . . . . . . . . . . 28

4.11 Distance between bulb plates relation Do = 12 m, α 6= 20◦ . . . . . . . . . . . . 29

4.12 Dimensions of a bulb plate section, , Source: British Steel . . . . . . . . . . . . 30

4.13 SolidWorks's Equation Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

5.1 IRB 4600-40/2.55 working range, Source: ABB . . . . . . . . . . . . . . . . . . 33

5.2 PK 500 welding torch installed on a IRB 4600 robot in RobotStudio . . . . . . . 34

5.3 XY Crane in RobotStudio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

5.4 Coordinates origins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

71

VT3 List of Figures

5.5 Weld types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5.6 Bulb welding points labelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5.7 Lateral welding points labelling . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5.8 Examples of bulb weld transition intermediate points . . . . . . . . . . . . . . . 39

5.9 Lateral weld transition intermediate points . . . . . . . . . . . . . . . . . . . . 39

5.10 Front and back bulb points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5.11 Left and top views of a bulb plate with the intermediate points displayed . . . 41

5.12 Left and top views of a bulb plate with the intermediate points displayed . . . 42

5.13 Bulb plate transition intermediate point . . . . . . . . . . . . . . . . . . . . . . 43

5.14 Main welding angles, Source: WeldCorTM . . . . . . . . . . . . . . . . . . . . . 44

5.15 Tool orientation during right lateral plate welding . . . . . . . . . . . . . . . . . 45

5.16 Welding path representation in RobotStudio . . . . . . . . . . . . . . . . . . . . 47

5.17 Fillet welds, Source: mitcalc.com . . . . . . . . . . . . . . . . . . . . . . . . . 47

5.18 Outer lateral plate welding sequence . . . . . . . . . . . . . . . . . . . . . . . . 49

5.19 Bulb plate and inner lateral plate welding sequence . . . . . . . . . . . . . . . . 50

6.1 Lid Plate Generator task pane . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

6.2 Task pane logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

6.3 Add-in task pane's views . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

6.4 Generate logic �ow diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

6.5 Lid plate base model with the welding paths de�ned in blue . . . . . . . . . . . 54

6.6 Get button to obtain the sketch coordinates in the task pane . . . . . . . . . . 55

6.7 Weld data de�nition logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

6.8 Target line generation logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

6.9 Movement instruction generation logic . . . . . . . . . . . . . . . . . . . . . . . 59

6.10 Welding characteristics obtaining logic . . . . . . . . . . . . . . . . . . . . . . . 60

7.1 Cost variation with lid pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

7.2 Cost variation with lid angle (Do = 10 m) . . . . . . . . . . . . . . . . . . . . . 66

7.3 Cost variation with lid angle (Do = 12 m) . . . . . . . . . . . . . . . . . . . . . 67

7.4 Cost variation with diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

A.1 Bulb iron section and main dimensions . . . . . . . . . . . . . . . . . . . . . . . 3

B.1 Conditions to apply table B.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

C.1 Example of moving instructions in RAPID, [ABB, 2003] . . . . . . . . . . . . . 9

C.2 Example of a complete welding movement, [ABB, 2003] . . . . . . . . . . . . . 10

E.1 SolidWorksAddinInstaller main window . . . . . . . . . . . . . . . . . . . . . . 16

E.2 Lid Plate Generator start task pane . . . . . . . . . . . . . . . . . . . . . . . . 17

E.3 Lid Plate Generator functional task pane . . . . . . . . . . . . . . . . . . . . . 17

E.4 Description of the functional task pane . . . . . . . . . . . . . . . . . . . . . . . 18

E.5 Edit WeldPaths sketch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

E.6 Set position control panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

E.7 Lid plate model loaded and correctly positioned in the virtual welding station . 21

E.8 Load to Station check box window . . . . . . . . . . . . . . . . . . . . . . . . . 22

72

List of Tables

2.1 Deposit rates of di�erent welding technologies, Source: TWI . . . . . . . . . . . 14

4.1 Lid plate design variations, Source: Universal Foundation . . . . . . . . . . . . 20

4.2 Bulb plates possible disposition [mm], Source: Universal Foundation . . . . . . 24

4.3 Bulb plate sections of every lid plate model [mm x mm], Source: Universal

Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5.1 Welding parameters for di�erent plate thicknesses, [CSFE, 2006] . . . . . . . . 44

5.2 Possible tool orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.3 Quaternion of every possible tool orientation . . . . . . . . . . . . . . . . . . . 46

5.4 Welding passes calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

7.1 Welding e�ciency for di�erent welding methods [León, 2013] . . . . . . . . . . 62

7.2 Deposition e�ciency factor for di�erent welding methods [León, 2013] . . . . . 62

7.3 Process parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

7.4 Welding geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

7.5 Welding time and cost comparison . . . . . . . . . . . . . . . . . . . . . . . . . 64

A.1 Bulb plates section description, Source: British Steel . . . . . . . . . . . . . . . 3

A.2 Bulb plates section description, Source: British Steel . . . . . . . . . . . . . . . 4

B.1 Welding procedure schedules for GMAW of plain carbon and low alloy steels

using spray transfer, Source: [CSFE, 2006] . . . . . . . . . . . . . . . . . . . . . 5

D.1 Cost breakdown for all lid plate models . . . . . . . . . . . . . . . . . . . . . . 13

E.1 Lid plate design variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

73

Bibliography

4CO�shore, 2013a. 4CO�shore. Gravity Based Support Structures. Available at

http://www.4coffshore.com/windfarms/

gravity-based-support-structures-aid8.html, 2013.

4CO�shore, 2013b. 4CO�shore. Jacket or Lattice Structures. Available at

http://www.4coffshore.com/windfarms/jacket-or-lattice-structures-aid5.

html#sthash.XVqjpNtQ.dpuf, 2013.

ABB, 2003. ABB. RobotWare-Arc and ArcSensor, Application Manual, 2003.

Association, 2014. Danish Wind Industry Association. O�shore. Available at

http://www.windpower.org/en/policy/offshore.html, 2014.

Association, 2003a. Danish Wind Industry Association. O�shore Foundations: Mono

Pile. Available at http://dr\T1\omst\T1\orre.dk/wp-content/wind/miller/

windpower%20web/en/tour/rd/monopile.htm, 2003.

Association, 2003b. Danish Wind Industry Association. O�shore Foundations: Tripod.

Available at http://dr\T1\omst\T1\orre.dk/wp-content/wind/miller/windpower%

20web/en/tour/rd/tripod.htm, 2003.

CSFE, 2006. CSFE. Chapter 10, Gas Metal Arc Welding, 2006.

Europe, 2016. Wind Europe. Wind in power - 2016 European statistics. Available at

https://windeurope.org/wp-content/uploads/files/about-wind/statistics/

WindEurope-Annual-Statistics-2016.pdf, 2016.

Gillis, 2014. Justin Gillis. A Tricky Transition From Fossil Fuel. New York Times,

Available at https://www.nytimes.com/2014/11/11/science/earth/

denmark-aims-for-100-percent-renewable-energy.html?_r=0, 2014.

H. Burningham, July 2008. J. French H. Burningham. Historical changes in the

seabed of the greater Thames estuary, The Crown State, July 2008.

ICCS-NTUA, July 2016. ICCS-NTUA. EU Reference Scenario 2016 - Energy,

transport and GHG emissions Trends to 2050, European Commission, July 2016.

IRENA, 2012. IRENA. Renewable energy technologies: cost analysis series. Available

at https://www.irena.org/DocumentDownloads/Publications/RE_Technologies_

Cost_Analysis-WIND_POWER.pdf, 2012.

León, 2013. A. Tejedor De León. Estimación de los costos en la soldadura eléctrica,

Universidad Tecnológica de Panamá, 2013.

75

http://www.4coffshore.com/windfarms/gravity-based-support-structures-aid8.html

http://www.4coffshore.com/windfarms/gravity-based-support-structures-aid8.html

http://www.4coffshore.com/windfarms/jacket-or-lattice-structures-aid5.html#sthash.XVqjpNtQ.dpuf

http://www.4coffshore.com/windfarms/jacket-or-lattice-structures-aid5.html#sthash.XVqjpNtQ.dpuf

http://www.windpower.org/en/policy/offshore.html

http://dr\T1\o mst\T1\o rre.dk/wp-content/wind/miller/windpower%20web/en/tour/rd/monopile.htm

http://dr\T1\o mst\T1\o rre.dk/wp-content/wind/miller/windpower%20web/en/tour/rd/monopile.htm

http://dr\T1\o mst\T1\o rre.dk/wp-content/wind/miller/windpower%20web/en/tour/rd/tripod.htm

http://dr\T1\o mst\T1\o rre.dk/wp-content/wind/miller/windpower%20web/en/tour/rd/tripod.htm

https://windeurope.org/wp-content/uploads/files/about-wind/statistics/WindEurope-Annual-Statistics-2016.pdf

https://windeurope.org/wp-content/uploads/files/about-wind/statistics/WindEurope-Annual-Statistics-2016.pdf

https://www.nytimes.com/2014/11/11/science/earth/denmark-aims-for-100-percent-renewable-energy.html?_r=0

https://www.nytimes.com/2014/11/11/science/earth/denmark-aims-for-100-percent-renewable-energy.html?_r=0

https://www.irena.org/DocumentDownloads/Publications/RE_Technologies_Cost_Analysis-WIND_POWER.pdf

https://www.irena.org/DocumentDownloads/Publications/RE_Technologies_Cost_Analysis-WIND_POWER.pdf

VT3 Bibliography

Neslen, 2016. Arthur Neslen. Denmark broke world record for wind power in 2015. The

Guardian, Available at https://www.theguardian.com/environment/2016/jan/18/

denmark-broke-world-record-for-wind-power-in-2015, 2016.

Villumsen, 2017. Sigurd Lazic Villumsen. Bucket Assembly Welds - Modular Bucket,

2017.

76

https://www.theguardian.com/environment/2016/jan/18/denmark-broke-world-record-for-wind-power-in-2015

https://www.theguardian.com/environment/2016/jan/18/denmark-broke-world-record-for-wind-power-in-2015

Suction Bucket lid plate design and welding automation

Make Offshore wind turbines a competitive technology by making the

production processes of new foundation structures more flexible

By

JAVIER ZARAGÜETA GONZÁLEZ

APPENDIX

Table of content

Appendix A: Bulb plate sections 3

Appendix B: Welding parameters 5

Appendix C: RAPID program structure 7

Appendix D: Lid plate welding time and cost breakdown 13

Appendix E: User guide 15

1

Bulb plate sections A

Figure A.1: Bulb iron section and main dimensions

Table A.1: Bulb plates section description, Source: British Steel

Section description

b t c r

mm mm mm mm

140x8 140 8 19 5

160x7 160 7 22 6

160x8 160 8 22 6

160x9 160 9 22 6

180x8 180 8 25 7

180x9 180 9 25 7

180x10 180 10 25 7

200x9 200 9 28 8

200x10 200 10 28 8

200x11.5 200 11,5 28 8

220x10 220 10 31 9

220x11.5 220 11,5 31 9

3

Table A.2: Bulb plates section description, Source: British Steel

Section description

b t c r

mm mm mm mm

240x10 240 10 34 10

240x11 240 11 34 10

260x10 260 10 37 11

260x12 260 12 37 11

280x11 280 11 40 12

280x12 280 12 40 12

300x11 300 11 43 13

300x12 300 12 43 13

300x13 300 13 43 13

320x12 320 12 46 14

320x13 320 13 46 14

340x12 340 12 49 15

340x14 340 14 49 15

430x17 430 17 62,5 19.5

Welding parameters B

Figure B.1: Conditions to apply table B.1

Table B.1: Welding procedure schedules for GMAW of plain carbon and low alloy steelsusing spray transfer, Source: [CSFE, 2006]

Thickness of Electrode Welding Welding Wire Feed Gas Flow Travel

base metal Diameter Voltage Current Speed Rate Speed

mm mm V A mm/s l/min mm/s

6,4 1,6 24-26 325-375 89-110 21 13-14

6,4 2,4 26-29 400-450 42-51 21 14-15

9,5 1,6 24-26 325-375 42-51 21 8-10

9,5 2,4 26-29 400-450 42-51 21 8-12

12,7 1,6 24-26 325-375 89-110 21 9-11

12,7 2,4 26-29 400-450 42-51 21 11-13

19,1 1,6 24-26 325-375 89-110 21 9-11

19,1 2,4 26-29 400-450 42-51 21 10-12

5

RAPID program structure CThree �les are needed to be able to upload a RAPID program to a station created in

RobotStudio:

RobotProgramm.pgf : This �le indicates the version of the program and the name

of all the �les that are used for the robot programming.

CalibData.mov: This �le contains the calibration data of the tool used by the

robot and the work objects de�ned in the work station.

ModuleX.mov: This �le contains the RAPID program of the robot. There could

be more than one of this �les, but, if so, the name of the extra �les have to be

indicated in RobotProgramm.pgf �le.

Knowing this, the C# program that controls the parametric design of the lid plate and the

welding coordinates report generation is extended to generate this three �les. Basically,

the SolidWorks add-in generates the three �les based on the lid plate model selected by

the user and the welding station and parameters previously de�ned.

The RAPID code from ModuleX.mov is what will de�ne the operation of the welding

station. In every RAPID program four main parts can be distinguish:

a) Welding data de�nition

b) Target coordinates de�nition

c) Robot movement de�nition

d) Movement sequence de�nition

7

C.1 Welding data de�nition

For any welding instruction in RAPID programming language two types of welding data

have to be de�ned:

� Seam data: used to control the start (ignition) and end of the weld.

� Weld data: used to control the welding operation while the arc is established.

In this case the de�nition of the seam data is not relevant and all its components are set

to 0. On the other hand, as weld data usually changes from one weld to another, so it is

important to identify all the di�erent welding conditions and de�ne as many weld data as

needed. To de�ne all the weld data the following structure has to be followed:

PERS welddata name:=[weld_speed, org_weld_speed, main_arc, org_arc];

name : Unique name for each weld data set.

weld_speed : Desired welding speed.

org_weld_speed : Original welding speed.

main_arc: Main arc parameters during the weld phase.

org_arc: Original arc parameters.

For this application, both org_weld_speed and org_arc will be ignored and set to 0 to

simplify the parameter de�nition. On the other hand, weld_speed is represented in mm/s

and parameters inside main_arc data consist mainly on the weld voltage and the welding

material feed speed.

C.2 Target coordinates de�nition

To de�ne each one of the coordinates in the RAPID code, the following structure has to

be follow:

CONST robtarget point_name:=[coord, orient, con�g, external_axis];

point_name : Unique name of the welding coordinate.

coord : X, Y and Z coordinates of the point.

orient : Four values that de�ne the orientation of the tool at the point.

con�g : Four values that de�ne the con�guration of the joints of the robot arm at

the point.

external_axis: Position of each one of the external axes. In total there are �ve

possible values.

C.3 Robot movement de�nition

During the automatic manufacturing process there are two main types of movement that

the robot has to carry out:

� Transition movement

� Welding movement

For each type of movement need di�erent instructions to be de�ned. Figure C.1 show a

simple example of a typical welding robot movement and the RAPID instructions needed

to carry it out:

Figure C.1: Example of moving instructions in RAPID, [ABB, 2003]

Taking this �gure as a reference, transition instructions' structure can be de�ned the

following way:

MoveX point_name, speed, prec, tool ;

X : Represents the type of movement; J for a joint movement or L for a linear move-

ment.

point_name : Name of the point towards the robot is going to move.

speed : Linear speed of the robot during the movement in mm/s.

prec: The precision with which the robot will approach the target point.

tool : Name on of the tool installed on the tip of the robot.

Unlike the transition movements, to de�ne a complete welding movement three di�erent

instructions have to be de�ned.

Figure C.2: Example of a complete welding movement, [ABB, 2003]

As it can be seen in �gure C.2, every welding has to start with a ArcLStart and end with

a ArcLEnd instruction. If the welding consists on one ore more concatenate weld seams

with the same or di�erent welding parameters, as many as needed ArcL instructions have

to be de�ned. These three types of instructions follow the same structure that can be seen

in �gure C.1:

ArcLarc_inst point_name, speed, seam_data, weld_data, prec, tool ;

arc_inst : ArcLStart, ArcLEnd or ArcL.

point_name : Name of the point towards the robot is going to move.

speed : Linear speed of the robot during the movement in mm/s.

seam_data : Seam data of the weld.

weld_data : Welding parameters.

prec: The precision with which the robot will approach the target point.

tool : Name on of the tool installed on the tip of the robot.

C.4 Movement sequence de�nition

Finally, all the movement instructions previously explained are grouped on a certain

sequence to form paths. Two main structures could be distinguish for the movement

sequence de�nition:

Path programs:

These sets of code de�ne a sequence of movement instructions like the one stated in

the previous point.

Main program:

In this program the correct sequence of paths is stated. This is the program that

will run during the simulation of the station.

These two structures could be simpli�ed the following way:

PROC Path name()

Movement instruction 1

...

Movement instruction n

ENDPROC

PROC Process name()

Path 1

...

Path n

ENDPROC

Lid plate welding timeand cost breakdown DTable D.1: Cost breakdown for all lid plate models

Welding Labour Electrode Energy Total

Model time cost cost cost cost

h ¿ ¿ ¿ ¿

MB9_200 7,08 353,8 44,15 6,5 404,48

MB9_300 8,61 430,71 53,75 7,96 492,43

MB9_400 9,55 477,44 59,59 8,82 545,85

MB10_200 9,24 462 57,66 8,53 528,22

MB10_300 10,87 543,51 67,83 10,04 621,39

MB10_400 11 550,1 68,65 10,16 628,92

MB10_400_6 26,1 1304,94 162,86 24,11 1491,91

MB10_400_12 7,97 398,28 49,7 7,36 455,34

MB10_400_15 4,02 201,14 25,1 3,72 229,96

MB11_200 11,14 556,82 69,49 10,29 636,61

MB11_300 11,98 598,83 74,73 11,06 684,64

MB11_400 14,63 731,43 91,28 13,52 836,23

MB12_200 13,47 673,7 84,08 12,45 770,23

MB12_300 15,18 759,17 94,74 14,03 867,94

MB12_400 17,66 882,85 110,18 16,32 1009,34

MB12_400_12 9,30 465,11 58,05 8,6 531,75

MB12_400_15 7,05 352,3 43,97 6,51 402,78

13

User guide EThis document how the SolidWorks' add-in and RobotStudio's welding cell designed for

this project have to be used to obtain the desired results. It is important to remember

that all the following �les are required to ensure the functionality of both tools:

� C# folder: Contains the add-in's code �les and bulb plates Excel data base.

� SolidWorks folder: Contains the lid plate base model on .PRT and .SAT formats.

� RobotStudio folder: Contains the weld station design, 3D models of the crane

components and a �le to save all the RAPID codes generated with the add-in.

The Lid Plate Generator and the welding station have been designed to be installed and

used with SolidWorks 2016 and RobotStudio 6.04, so de compatibility with other versions

of these two software cannot be ensured.

The development of this add-in has been possible thanks to the previous work of the

software developer Luke Malpass from AngelSix. He has created a easy to use SolidWorks

API called SolidDNA, which makes the usage of the SolidWorks API much easier. It is

totally free and open source. For further information about Luke's projects or deeper

questions about the software:

Email: [email protected]

Web page: AngelSix.com

YouTube: AngelSix

15

www.angelsix.com

https://www.youtube.com/channel/UCJ3AxeCHGPZkMi3kRfCuiHw

E.1 Lid Plate Generator

This add-in enables the parametric design of lid plates 3D models to scale a base model

and obtain a desired lid plate design from the set of models available. Once the desired lid

plate model has been generated the welding robot program can be automatically generated

to load it to RobotStudio and simulate the process.

E.1.1 Add-in installation

To install the add-in go into the C# �le and you will �nd the SolidWorksAddinIn-

staller:

Figure E.1: SolidWorksAddinInstaller main window

As it can be seen in �gure E.1, to install the add-in a .dll �le is required. This �le can be

found inside C# �le in the following location:

solidworks-api-master → LidPlate.Generator.AddIn →LidPlate.Generator.AddIn → bin → Debug → LidPlate.Generator.AddIn.dll

Once selected the correct .dll �le, press the Install and wait until the add-in has been

installed.

E.1.2 Generate and save a lid plate model

The �rst functionality that the SolidWorks add-in o�ers is the generation of di�erent lid

plate models from a base model. Once the add-in has been installed, the required graphical

interface will be available showing the following task pane:

Figure E.2: Lid Plate Generator start task pane

To unlock the functional task pane of the add-in a valid base model has to be loaded to

SolidWorks. This base model can be found in the SolidWorks folder.After doing this, the

following task pane will be visible:

Figure E.3: Lid Plate Generator functional task pane

The detailed description of the full operative task pane can be seen in �gure E.4:

Figure E.4: Description of the functional task pane

So, the desired lid plate model has to be selected from the LID PLATE MODEL combo

box. The naming of the di�erent models follows the following logic:

MB OuterDiameter _ LidPressure _ LidPLatesNumber

The last component of the name represents how many lid plates like the one selected are

needed to complete a Mono Bucket lid. This will only appear if the number is di�erent

from 8. All the available models and their properties can be seen in table E.1:

Table E.1: Lid plate design variations

Model Lid pressure [KPa] Do [m] Di [m] Bulb plates α [◦]

MB9_200 200 9 2 8 20

MB9_300 300 9 2 8 20

MB9_400 400 9 2 8 20

MB10_200 200 10 2 8 20

MB10_300 300 10 2 8 20

MB10_400 400 10 2 8 20

MB10_400_6 400 10 2 6 30

MB10_400_12 400 10 2 12 15

MB10_400_15 400 10 2 15 12

MB11_200 200 11 2 8 20

MB11_300 300 11 2 8 20

MB11_400 400 11 2 8 20

MB12_200 200 12 2 8 20

MB12_300 300 12 2 8 20

MB12_400 400 12 2 8 20

MB12_400_12 400 12 2 12 15

MB12_400_15 400 12 2 15 12

Once the desired model has been selected, just by clicking the Generate button the base

model will be resized and scaled as the selected lid plate model.

If you want to recover the base model geometry, it can be done by clicking the Reset

button.

To save the generated lid plate model click the Save button and decide the location where

the model id going to be saved.

E.1.3 RAPID welding program generation

To generate the welding program that later will be loaded to RobotStudio to simulate the

process the desired lid plate model has to be generated. Then the WeldPaths sketch

has to be accessed to allow the add-in to take the geometrical information for the welding

coordinates de�nition. To do this right-click theWeldPaths sketch of the design tree and

select Edit Sketch.

Figure E.5: Edit WeldPaths sketch

Then select all the lines from the sketch and click the Generate RAPID program

button of the task pane and select the location where the �les are going to be saved. This

action will take some seconds, so wait until the light on the right side of the button turns

green to load the program to RobotStudio.

E.2 Robot Studio welding cell

E.2.1 Loading and positioning of a lid plate

Once the 3D model of the desired lid plate design has been generated, it has to be saved

as a .SAT �le. This type of �les is the only one that RobotStudio can work with.

To load .SAT model into RobotStudio's working environment follow the next steps:

1. Delete any exiting lid plate model.

2. Click Import Geometry from the Home tab and Browse for Geometry...

3. Search the .SAT �le that contains the desired lid plate model.

4. Double click the �le and wait until the model has been completely loaded to the

station.

With the model loaded to the station some positioning has to be carried out to arrange

the plate correctly in the station. To do so, follow this steps:

1. Select the loaded model in the weld station.

2. Go to Modify tab and click on Set Position and the following control panel will

appear:

Figure E.6: Set position control panel

3. For this application the translations and rotations that have to be introduced to

correctly position the lid plate are the ones shown in �gure E.6:

Position:

X = -400 mmY = 4600 mmZ = 900 mm

Orientation:

α = 90◦

β = 0γ = 0

After doing this the lid plate would be correctly positioned an ready to introduce its

welding program as is shown in �gure E.7:

Figure E.7: Lid plate model loaded and correctly positioned in the virtual welding station

E.2.2 Loading and setting a RAPID welding program

First of all, to be able to use the arc welding instructions of the RAPID programs the Arc

Welding Power Pack has to be installed. To load a RAPID welding program obtained from

the Lid Plate Generator the Arc Welding Add-in has to be activated on the Add-ins tab.

After doing this, follow the next steps:

1. Delete all existing points and paths from the tree on the Paths&Targets tab.

2. On theRAPID tab click Program and thenDelete Program to erase the existing

program from the virtual controller.

3. Click again Program and Load Program....

4. Search the location where the folder with all the program �les are saved.

5. Select the .pgf �le and load it.

6. Synchronize all the information of the RAPID program to the station marking all

the check boxes that appear on the next window:

Figure E.8: Load to Station check box window

7. Wait until the synchronization process ends.

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