162

PART-A

1. Write CAD definition.

Computer Aided Design (CAD) may be defined as the use of computer

system to help in the creation, modification, analysis and optimization of a

design.

2. What is meant by scaling?

Scaling is the enlargement (or) reduction in size of the graphic element.

3. What are the two types of geometric modeling?

2D models

3D models

4. List out FEA advantages.

Increased accuracy

Enhanced design

Virtual prototyping

Increased productivity

5. What are the functions of Cam?

Manufacturing planning

Manufacturing control

6. Define part families.

A part family is a collection of parts which are having similar design

attribute (geometric shape and size) or similar manufacturing attributes

(similar operation steps are required in their production).

7. What are the advantages of CAPP?

Automated process planning leads to more logical and optimal

process plans.

High product quality

The productivity of process planner is increased.

The lead time for process planning is reduced.

8. What is rapid prototype?

Rapid prototyping is the automatic construction of physical objects using

additive manufacturing technology.

9. Expand NC, DNC, and CNC.

NC- Numerical Control

DNC- Direct numerical Control

CNC- Computer Numerical Control

10. What are the features of CNC machines?

Automatic Tool changing

Automatic Work piece positioning

Automatic pallet changer

11. What are the types of slide ways?

Friction type slide way

Anti friction type slide way

12. What is ATC?

Automatic tool changer (ATC) is an important part of a CNC

machine. An ATC picks up a tool from the tool magazine and replaces it with

the tool in the spindle.

13. Define co-ordinate system.

The co-ordinate system is to provide a means for locating the tool in

relation to the work piece.

14. What is a datum point?

The origin of the coordinate system is considered as zero point.

15. List out M code for spindle on and off.

M03- Spindle ON, Clockwise

M04- Spindle ON, Anti Clockwise

M05-Spindle OFF

16. What is meant by peck drilling?

It is used for deep hole drilling. In this cycle, the feed from the work

surface is intermittent.

17. List out benefits of FMS.

Higher machine utilization.

Reduced number of tools and machines required

Reduced work-in-progress inventory

Reduced manufacturing lead time.

18. Define AGV.

An Automated Guided Vehicle is a material handling equipment which can be

independently operated and guided along defined pathways in the factory

floor. It is normally powered by on-board batteries.

19. List the robot programming methods.

Manual method

Walk through method

Lead through method

Off-line programming method

20. What is virtual machining?

The various modules available in the CAM software packages are used to

simulate the machining operations on the computer workstation. Since the

machining is carried out in a virtual environment it is called virtual

machining.

PART-B

21. (A) (i) Explain integrated CAD/CAM system. (theory =3 marks +

fig=3 marks)

CAD /CAM is concerned with the engineering

functions in both design and manufacturing. Product design, engineering

analysis and documentation represent engineering activities in design.

Process planning, NC part programming and other activities associated

with CAM represent engineering activities in manufacturing.

In addition, CAM has evolved to include many

other functions in manufacturing such as material requirement planning,

production scheduling, computer production monitoring and computer

process control.

Figure: Scope of CAD/CAM

In the conventional method, engineering

drawings were prepared by the design draftsmen and later by

manufacturing engineers to develop the process plan. This was time

consuming and duplication of effort by design and manufacturing

personnel. Nowadays, the product design and manufacturing functions are

integrated by using CAD /CAM technology. This is termed as integrated

CAD / CAM. The goal of CAD /CAM is not only to automate certain

phases of design and certain phases of manufacturing but also to automate

the transition from design to manufacturing.

Figure: Common database linkage

In integrated CAD /CAM organization, the

CAD system creates the model and its design database. The database

contains geometric data, bill of materials, specification of the product etc.

The CAM system uses this common database

and converts it to a process plan for manufacturing the product. This

conversion can be automatically done by AutoCAD software’s.

A large portion of processing is accomplished on a numerically controlled

machine tool. The NC part program necessary for making the product is

automatically generated by CAM system. The CAM system downloads the

NC part program directly to the machine tool by means of

telecommunication network. Thus product design, NC part programs,

machining the product (component) are all implemented by computer in

integrated CAD/ CAM environment.

(ii) Briefly explain 2D and 3D transformations. ( 2D =3marks + 3D =3

marks)

2D transformations.

The X and Y coordinates are specified to

locates a point in a two axis Cartesian system. These coordinates may be

represented by lx2 matrix as (X,Y). For example the matrix (4,6) represents

a point, which is 4 units from the origin in the X direction and 6 units from

the origin in the Y direction. Similarly, a line may be represented by a 2 x2

matrix by giving the X and Y coordinates of the two end points of the line.

The Notation of line matrix is as follows L =

Where, (X1, Y1), (X2, Y2) be the two end points of the line L.

Using the rules of matrix algebra, any geometric element represented in

matrix notation can be changed into a new element by using the following

matrix transformations.

i) Translation

It means moving the element from one locations to another. In the case

of a point, the operation is as follows:

X1 = X + m Y1= Y+ n

where

X', Y' = Coordinates of the new location after move

XY = Coordinates of the original location (old location)

m , n = Movements in the X and Y direction respectively

In line matrix notation, It can be represented as

(X 1Y1) = (X,Y) + t

where

t = (m , n) Translation matrix. Like this the translation matrix is

applied to line and other geometric elements.

Example: Consider a line with original end coordinates (1,1) and (2,4) is

moved to new location of coordinates (3.4) and (4,7). For this

The line matrix is

(or)

(B) (i) Explain two types of solid modeling. ( each type 3 marks)

The best method for three modeling model

construction is the modeling technique. It provide the user with complete

information about the model. When color is added to the solid model, the

resulting picture becomes very realistic. All solid modeling systems

provide facilities for creating, modifying and inspecting models of three

dimensional solid objects.

The following representation schemes are

available for creating solid models.

1) Constructive solid geometry (CSG) (or) C-rep

2) Boundary representation (B-rep)

3) Pure primitive instancing

4) Generalized sweep

5) Cellular decomposition

6) Hybrid scheme

1) Constructive solid geometry (CSG) (or) C-rep

It is also called as building block approach.

Combination of simpler solid objects makes CSG model.

Boolean operators are used for combining the primitives

to form the complete solid object.

Figure: Boolean operations for two dimensional model

Simplest solid objects are termed as primitives. Some of

the primitives are cubes, spheres, cylinders. cone,

rectangular blocks etc.

The available Boolean operators are union (u or +),Intersection (n)

and the difference (-).

Figure: Boolean operations for three dimensional model

CSG Using Boolean Operators

Union( ̬̮ )

When two or more solids are combined with the

boolean operator union, the result is the single solid incorporating all the

space occupied by any of the individual components. Simply, this is

like adding components together.

Difference(-)

When two or more solids are combined with the

boolean operator difference, the result is the single solid incorporating the

space, which is occupied by the first component but is outside all of the

remaining components. This is like subtracting the second and subsequent

components from the first component

Intersection (̂ ̯)

When two or more solids combined with

intersection, the result is a single solid object incorporating the s 4

occupied in common by each of the components.

2) Boundary representation (B-rep) method

In representation scheme, a solid is represented

by the data structure containing the elements, boundary. These elements are

divided into topologies elements and geometric elements. These geometric

elements are linked to the appropriate topological elements as follows:

Face ------- Surface

Edge-------- Curve

Vertex------- Point

There are two types provided to create 3D model by B-rep method.

• Topological elements (Vertex, Edge and Face)

• Geometrical elements (Point, Curve, Surface)

The following is the example for B-rep. The various faces are •med by

vertices and Edges. The faces are linked to create the solid model.

Figure: Boundary representation

(ii) Explain graphics standard. (6 marks)

The standard for exchanging graphics and

data from one CAD stem to another CAD system without anti trouble is

called as “graphic standard". Various types of data to be exchanged from

one CAD system to another CAD system are explained below.

1. Shape data - This consists of geometrical, topological and part

information’s.

2. Non shape data - This consists of shaded images and global data of

models.

3. Design data - This consists of analytical information like mass

properties and finite element mesh data.

4. Manufacturing data - This consists of information on tooling, tool

design, NC tool paths. tolerance, process planning and bill of

materials.

Need or Benefits of Graphic Standards

Graphic standards are needed to achieve the

following benefits in CAD.

1. Application program portability - To exchange application softwares.

2. Picture data portability - To exchange graphics

3. Text portability - To exchange text

4. Database portability - To exchange object related data

The following are the common graphic standards used in CAD / CAM

application

1. GKS : Graphic Kernel System.

2. PHIGS : Programmer's Hierarchical Interface for Graphics.

3. IGES : Initial Graphics Exchange Specification.

4. DXF : Drawing Exchange Format Standard for The Exchange of

Product model data.

5. STEP : Dimensional Measurement Specifications.

6.DMIS : Virtual Device Interface Virtual Device Metafile GKS Metafile

7. VDI : Virtual Device Interface

8.VDM : Virtual Device Metafile

9 .GKSM : GKS Metafile

10. WMF : Windows MetaFile

22. (A) (i) Explain part classification and coding system (6) marks

Part classification is the process of separating the part into groups based on the characteristic attributes. Coding

is the process of providing a symbol to the component. Part classification

and coding process starts from the examinations and analysis of the design

and manufacturing attributes of each part.

An alternative approach is to use a computerized classification and coding system in which the user responds to

questions asked by the computer. On the basis of the responses, the computer

assigns the code number to the part. A number of classification and coding systems and software packages for coding are commercially available.

However, none of the systems has been universally adopted.

One of the reasons for this is that a classification and coding system should be customized for a given company

(Industry). A system that is best for one company may not be best for

another company

Features of part classification and coding system Design and manufacturing are the important

functional areas that utilize a part classification and coding system. Accordingly, the systems fall into one of the following three categories

1) System based on design attributes.

2) System based on manufacturing attributes. 3) System based on both design and manufacturing attributes.

Part classification by design attributes

The part classification by design attributes means the following points

are to be considered.

• Basic shape (Both Internal or External) • Length to diameter ratio

• Major dimensions

• Minor dimensions • Tolerances

• Surface finish

Part classification by manufacturing attributes

The part classification by manufacturing attributes means the

following points are to be considered. • Major (or) Minor processes

• Operations sequence

• Cutting tools • Fixtures needed

• Production time

• Production rate

Application of part classification and coding

The part classification and coding can be effectively

used for the following purpose:

Design retrieval

While developing a new part, h is economical to use a design

retrieval system to determine if a similar part already exists. A simple change in a existing part will take much less time than designing a

complete new part from scratch. The existing part can be retrieved by

specifying its part code.

Automated process planning

The part code of a new part can be used to search for process plans for

existing parts with identical (or) similar codes.

Machine cell design

the part codes can be used to design machine cells capable of producing all

members of a particular part family, using the composite part concept.

(ii) Explain master production schedule. ( Theory=4 marks+ fig=2 marks)

Master Production Schedule (MPS) Master

production schedule (MPS) is a revised aggregate production planning.

MPS gives the specific schedule of individual products in the aggregate production plan. It is a list of products to be manufactured, when they

should be completed and delivered and in what quantities.

A typical aggregate production plan and a master production schedule are

shown in the figure. The aggregate production plan indicates the production

output levels for the major product lines of the company. The aggregate

production plan must be coordinated with the plans of the sales and

marketing departments.

Figure: Aggregate production plan and master production schedule

The following are the information needed to prepare master production

schedule

1) The production plan conveyed by the Top management.

2) Long term forecast of the individual Items

3) Actual orders received from the customers

4) Present inventory level of the individual items

5) Resource constraints.

Objective of MPS

The following are the objectives of master production schedule:

1) To make the best use of the resources available equipments, material

and labour.

2) To maintain the inventory as low as possible

3) To maintain the finished products delivery as perpendicular the

expectations of the customers.

(or)

(B) (i) Briefly explain shop floor control.( theory=3 marks+ fig= 3 marks)

Shop floor control is concerned with the

release of production orders to the factory, monitoring and controlling the

progress of the orders through the various work centers and collecting

current information on the status of the orders.

Figure: Shop floor control system

A typical shop floor control consists

1) Order release

2) Order scheduling

3) Order progress

1) Order release

This phase provides the documentation needed to process production

order through the factory. The collection of documents is called shop

packet. It consists oldie following:

Route Sheet : It gives the process plan for the item to be produced.

Material requistion: It is a form needed for getting the necessary raw

materials from inventory.

Job cards: It is a form required to enter the direct labour time for each

operation on the route sheet.

Move tickets :It is a form needed to move the parts between work

centers.

Parts list: It is a list of parts needed for assembly jobs. MRP

,engineering and manufacturing database are inputs to the order

release module.

2) Order Scheduling

Orders scheduling is the process of assigning the production orders to the

various work centers in the plant.

(ii) Describe deposition modeling .( theory=3 marks+ fig= 3 marks)

In this process, a plastic filament is unwound

from a coil and supplies material to an extrusion Nozzle. The Nozzle is

heated to melt the plastic and has a mechanism which allows the flow of

the melted plastic to be turned on and off.

The Nozzle is mounted to a mechanical

platform, which can be moved in both horizontal and vertical directions.

As the Nozzle is moved over the table in the required geometry, it deposits

a thin bead of extruded plastic to form each layer. The plastic hardens

immediately after being squirted from the Nozzle and bonds to the layer

below. Several materials are available for the process including investment

casting wax. Some FDM systems utilize two extrusion nozzles-one for the

deposition of a build material and second for the deposition of washable

material to make support environment.

A large range of FDM materials are available

that include ABS (Acrylonitrile Butadiene styrene), polycarbonate,

polypropylene, PMMA (polymethyl methacrylate) and various polyesters.

This process is widely used for concept models, form, fit and function

models, along with patterns for the creation of moulds and tooling. The size

ranges of the machines range from a low bulk envelope of200 x 200 x

300mm to a high of 600 x 500 x 600mm, Fused deposition modeling

process is shown in the figure.

Figure: Schematic of fused deposition modeling device

23. (A) (i) Explain the construction and working principle of turning

centre.( horizontal turning centre=3 marks + vertical turning

centre=3 marks)

CNC turning centre is a machine tool

capable of performing various turning and related operations, on work piece in one setup under CNC system. These are generally provided with

two axis control, Z axis parallel to the spindle and X axis perpendicular to

spindle axis. It is also provided with a index able tool turret which can hold 8,12 (or) 16 tools of various types.

CNC turning centers are classified as follows: 1) Horizontal turning centre.

2) Vertical turning centre.

3) Turn-mill centre. 4) Twin turret turning centre.

5) Multiple spindle turning centre.

Horizontal Turning Centre

CNC Horizontal turning centre is capable of performing all the

operations of a conventional lathe.

CNC Horizontal turning centre is provided with two axis control.

Figure: CNC Horizontal Turning Centre

Z axis parallel to the spindle

X axis perpendicular to the spindle.

CNC lathe bed is sloped to have better view of machining and also

for easy movemet of turrets.

Turret can hold 8 (or) 12(or) 16 tools of various types.

The sophisticated horizontal turning centres have the following

features.

Automatic cheching of workpiece dimension after machining

Sensing when tools are worn out.

Automatic tool changing when tools become worn (or) damaged.

Automatic workpiece changing at the completion of the work

cycle.

Vertical Turning Centre

CNC vertical turning centre is capable of performance all the

operation of a conventional lathe.

CNC vertical turning centre is provided with two axis control.

Z axis parallel to the spindle.

X axis perpendicular to the spindle

CNC lathe bed is sloped to have better view of machining and also

for easy movement of turrets.

Turret can hold 8 (or) 12(or) 16 tools of various types.

Figure: CNC VerticalTurning Centre

The sophisticated vertical turning centres have the following

features.

Automatic cheching of workpiece dimension after machining

Sensing when tools are worn out.

Automatic tool changing when tools become worn (or) damaged.

Automatic workpiece changing at the completion of the work

cycle.

Vertical turning centres are used for very large diameter

workpiece

The spindle is in vertical position like slotting machine.

The bed/ table carries workpiece in horizontal plane.

Automatic pallet changer may be provided for quick changing of

the jobs.

(ii) Briefly machine axis convection in machine centre.(Theory=4

marks + Fig =2marks)

In CNC machines . the first axis to be

identified is the Z axis .This is then followed by X and Y axis

respectively.

Z axis

The Z-axis motion is along the spindle

axis (or) parallel to the spindle axis. In the case of machine without a

spindle such as shaper and planer, Z-axis is perpendicular to the work

holding surface.For the machines such as milling, drilling and lathe, the

cutting tools move in the negative “Z” direction to move a tool into the

workpiece. The positive “Z” motion increases the clearance between the

tool and workpiece surface.

Figure: Designation of axes

X-axis

X-axis is always horizontal and parallel to the

work holding surface (Table (or) bed) .When Z axis is vertical, the +ve Xaxis movement is towards right when looking from the spindle towards

its supporting column. The other direction is –ve X axis movement. When

Z axis is horizontal, the +ve Xaxis movement is towards right when looking from the spindle towards the workpiece. (Table (or) bed). The

other direction is eve X axis movement. For turning machines, X-axis is

radial and parallel to the cross

Y-axis

Y-axis is perpendicular to both X and Z axes and

the direction is identified by the right hand Cartesian coordinate system.

(Or)

(B) (i) Explain recalculating ball screw mechanism. .(Theory=4

marks + Fig =2marks)

Figure: Ball scerw mechanism

Recirculating ball screw and nut arrangement

are used to transmit motion to the slides. It consists of screw thread which

acts as ball race to hold steel balls. The balls are surrounded by a nut as

shown in the figure.

The balls rolling in the grooves exit from the

trailing end of the nut and are picked up by return tube inserted from

outside and are recirculated into the leading end of the Nut. The rotation of

the ball between the screw and the nut moves the slide attached to the nut.

Advantages

1. Very low coefficient of friction

2. Higher transmission efficiency

3. No stick-slip

4. Backlash between the parts are eliminated by preloading the assembly.

5. Reduced wear and tear.

(ii) Explain the construction and working principle of CMM.

.(Theory=4 marks + Fig =1+1marks)

Coordinate measuring machine (CMM) is an element mechanical system designed to determine the location, orientation,

dimensions and geometry.

Figure: Coordinate measuring machine

A CMM consists of the following components

1) Probe head and probe to contact the workpiece surface.

2) Displacement transducers to measure the coordinate values of each point (or) axis on the Job.

3) Drive system and control unit to move each of the three axes. 4) Digital computer with software.

Figure: a) Single tip probe B) Multiple tip probe

Probe

Probe is the main part of a CMM. It is used to make contact with the

workpiece surface.

This contact records the X,Y,Z coordinates of the contact this point to calculate the dimensional (or) other needed data for inspection. The tip of

the probe is high hardened ruby ball. Sing tip (or) multi tip probes are used

in CMM. Most of the probes used today are Touch-trigger probes. When this probe is

made to contact with the surface, When this probe is It actuates and

coordinate position of the probe is measured by displacement ached to the three linear axes transducers attached to the three linear axis.

The coordinate positions are recorded by the CMM controller, Rotary encoders, optical scales and magnetic scales are the commonly used

displacement transducers.

(A) (i) Explain CNC programming procedure. .(Theory= 3 marks + Fig

=3 marks)

24.

The following are the steps involved in the

development of a part program and its proving.

1) Process planning

The programmer carryout a careful study of a part drawing to prepare th

process plan. It includes the following:

Machine tools used.

Fixtures required.

Sequence of operations.

Cutting tools required.

Process parameters

Figure: CNC program procedure

2) Axes Selection

The reference axes should be chosen so that the coordinates for various

features can be determined easily.

3) Tool Selection

Various tools are feasible for a given operation, but some of them

would be more economical than others. So it is essential to choose the

right tool for the Job.

3) Cutting process parameters planning

For a given tool and the operation, the appropriate process parameters

such as speed, feed and depth of cut are to be selected. These may be taken

from the handbooks supplied by the cutting tool manufacturer (or) based

on the shop experience.

4) Job and tool setup planning

The initial position of job and tool are defined carefully.

5) Tool path planning

A careful planning of the tool path ensures that the required

manufacturing specifications are achieved at the lowest cost.

6) Part program writing

This involves the actual writing of the part program undertaking the

format and syntax restrictions into account.

7) Part program proving

Once the part program is created, It should be verified before it can be

loaded on the machine controller for the manufacture of the component. A

trial run can be carried out with (or) without the tool or workpiece to

enable visualization of movements taking place, and any collision possible

between the tool, the workpiece and the clamping device.

DEFINITIONS

a) Bit : A binary digit is called bit. It includes 0 (or) 1.

b) Character : A character is formed by a row of bits. It represents a

numerical digits (0-9), an alphabetical letter (A-Z) and (a-z) (or) a symbol.

c) Word : A word is formed by the combination of

characters.

d) Block : A block is formed from a collection of words. A block is

complete NC instruction.

(ii) Explain six G code using part programming. (codes explanation =3

marks + part program =3 marks)

G90-rough turning

Syntax:

G90 X_Z_F_

G90-taper turning canned cycle

Syntax:

G90 X_Z_R_F_

G94-box facing canned cycle

Syntax:

G94 X_Z_F_

G71-stock removal cycle

Syntax:

G71 U_R_

G71 P_Q_U_W_F_

G70-finish turning canned cycle

Syntax:

G70 P_Q_F_

G72-multiple facing cycle

Syntax:

G72 W_R_

G72 P_Q_U_W_F_

G76-multiple thread cutting cycle

Syntax:

G76 X_Z_A_I_K_D_F

G75-grooving canned cycle

Syntax:

G75 X_Z_I_K_F

(Or)

(B) (i) Explain linear interpolation and circular interpolation. (linear =3

marks +circular =3 marks)

Linear Interpolation (G01)

This is the most basic and is used for creating straight line path. G01 is used for linear interpolation at a given feed rate. The programmer specifies

the beginning point and end point of the straight line and the feed rate to be

used along the straight line.

The format of G01 is as follows: G01 X_ Z_ F_ Example: (Programming from A-B-C-D)

Figure: inear interpolation

ABSOLUTE MODE

Diameter programming Radius programming N030 G00 X20 Z0 N030 G00 X10 Z0

N040 G01 X30 Z-25 F150 N040 001 X15 Z-25 F150

N050 GOO X60 Z-23 N060 GOO X60 Z-23

INCREAMENTAL MODE

Diameter programming Radius programming N030 G00 U-90 W-25 N030 G00 U-45 W-25 N040 G01 U10 W-25 F150 N040 001 U5 W-25 F150

N050 G00 U30 W2 N060 G00 U15 W2

Circular Interpolation

This method is used for generating

circular arc. The circular interpolation can be achieved either by specifying

the radius (or) centre coordinates of the arc.The radius can be directly specified using the R word address. When the centre coordinate is

specified, its value is to be given in incremental from the start point of the

arc with word address I and K.

i) Circular interpolation-clockwise (G02)

The format of G02 is as follows: G02 X_Z_R_F_ (or) G02 X_Z _K_F_

Example: (Programming from A-B-C-D-E)

Figure: Circular interpolation-clockwise

ABSOLUTE MODE (Diameter programming) N030 G00 X20 Z0 N030 G00 X10 Z0

N040 G01 X30 Z-25 F150 N040 001 X15 Z-25 F150 N050 G02 X30 Z-30 R5 F50 N050 G02 X30 Z-30 R5 F50

N050 G00 X60 Z-28 N060 GOO X60 Z-28

ii) Circular interpolation-counter-clockwise (G03) The format of G02 is as follows:

G02 X_Z_R_F_ (or) G02 X_Z_I_K_F_

Figure:Circular interpolation-clockwise

Absolute mode (Diameter programming) NO30 G00 X20 Z0 NO30 G00 X20 Z0 NO40 G01 X20 Z-20 F150 N040 G01 X20 Z-20 F150

N050 G02 X30 Z-30 R5 F50 NO50 G02 X30 Z-30 10 K-5 F50 N060 G00 X60 Z-28 N060 G00 X60 Z-28

(ii) Write part program for peck drilling and explain. (program =4

marks+ explain =2 marks)

Peck Drilling Cycle[ G83]

It is used for deep hole drilling. In this cycle, from the

work surface is intermittent.

The format of G83 code is as follows.

G83 X_Y_Z_R_Q_F_

Where,

X,Y- Hole position data.

Z-Final depth of the hole to be drilled.

R- Position of the clearance plane workpiece surface.

Q- Depth of cut for each pass.

F-Feed rate.

Example :

Write a part program for producing the component shown below in

machining centre using Fanuc controller system

%

04130

N010 G21

N020 G95

N030 G40

N040 G91

N050 G28 X0 Y0 Z0

N060 G90 (Centre drilling 5 holes)

N070 M06 T0l

N080 M03 S2000

N090 G00 X50 Y20 Z5

N100 G81 X50 Y20 Z-5 R2 F0.5

N110 X50 Y50

N120 X50 Y80

N120 X50 Y80

N130 X20 Y50

N140 X80 Y50

N150 G80

N160 G91

N170 G28 X0 Y0 Z0

N180 G90

N190 M05

(Drilling 5 holes of Ø8.5mm)

N200M06 T02

N210 M03 S750

N220 G00 X50 Y20 Z5

N230 G83 X50 Y20 Z-33 R2 F0.1

N240 X50 Y80

N250 X50 YS0

N260 G83 X20 Y50 Z-13 R2 F0.1

N280 G80

N290 G91

N300 628 X0 Y0 Z0

N310 G90

N320 N105

(Counter Boring)

N330 M06 103

N340 M03 S1500

N350 G00 X50 Y50Z5

N360 G82 X50 Y50 Z-15 R2 F0.1

N370 G80

N380 G91

N390 G28 X0 Y0 Z0

N400 G90

N410 M05

(Tapping)

N420 M06 T04

N430 M03 S250

N440 G00 X20 Y50

N450 G84 X20 Y50 Z-10 R2 F1.5

N460 X80 Y50

N470 080

N480 G91

N490 G28 X0 Y0 Z0

N500 G90

N510 M05

N520 M30

25. (A) (i) Explain flexible turning cell. (6 marks)

A turning centre fitted with a gravity loading and unloading system

and pallets for storing workpiece and finished parts is a typical

flexible turning cell.

If the turning centre is incorporated with post process metrology

equipment like Renishaw probes and inductive measuring equipment

for automatic offset correction, the efficiency of the system

improves.

Automatic tool changers, tool magazines, block tooling, automatic

tool offset measurement, and automatic check change and chuck jaw

change etc help to make the cell to be more productive.

The availability of C-axis and line tools in the turret enables the

process designer to complete not only turning but also operations like

milling, off-centre drilling, tapping and helical groove cutting etc in

one setup. This means that all operations required to completely

machine a component can be carried out in one setup itself.

(ii) Explain AGV working principle. .(Theory= 3 marks + Fig =3

marks)

For the functioning of an AGV, it contains the

following Components :

1) Vehicle Guidance System

2) Vehicle Routing System

3) Traffic Control System

4) Vehicle dispatching System

1) Vehicle Guidance System

The guidance system is the method by which AGVS pathways are defined

and vehicles are controlled to flow the pathways. The following two

technologies are used for vehicle guidance.

Guide wire method

Paint strip method

Guide wire method

Figure: Guide wire method

In this method, electrical wires are placed in

a rectangular slot cut into the factory floor. Then the slot is filled with

cement. Then guide wire is connected to a frequency generator which emits

a low voltage, low-current signal with a frequency in the range 1-15 KHZ.

This induces a magnetic field along the pathway that can be follwed by on-

board sensors in the vehicle.

The sensors are mounted on the vehicle on either side of the guide wire.

When the vehicle is located such that the guidewire is directly between two

sensors, the intensity of magnetic field at each sensor will be equal.

If the vehicle goes one side, or if the guide wire path changes direction, the

magnetic field intensity at the two sensors will be different.

This difference is used to control the steering motor. The motor makes

required changes in vehicle direction to equalize the two sensor signals,

thereby tracking the guide wire.

Paint strip method

In this method, paint strips are used to define the pathways. The vehicle

uses an optical sensor system for tracking the pathway. The strips can be

taped, sprayed (or) painted on the floor.

Figure: Paint strip method

The fluorescent particles in the paint strip reflect on Ultraviolet light source

from the vehicle. An on-board sensor detects reflected light in the strip and

controls the steering mechanics to follow it.

This method is useful when the installation of guide wires in the floor

surface is not practical. The paint strip must be kept clean and periodically

repainted.

2) Vehicle Routing System

An AGVS layout contains multiple tracks, pickup and drop off

stations. The most appropriate route must be selected from the alternative

pathways available. The following two methods are used to select the route.

Frequencies select method: In this method, the guide wires leading into

various paths have different frequencies. The vehicle reads an identification

code on the floor to determine its location. Depending on its programmed

destination, the vehicle selects the correct guide path by following only one

of the frequencies.

Path switch select method: In this method, the appropriate path is selected

by switching off the power in all other pathways except the required path. I

he guide path layout is divided into blocks that are electrically insulated

from each other. The blocks can be turned ON and OFF either by the

vehicle itself or by a computer control.

3) Traffic Control System

The purpose of traffic control in an AGV system is to minimize

interference between vehicles and to prevent collisions. The following two

methods are used for traffic control in AGV system.

Forward sensing control: In this method, the vehicle uses °Ile Or) more

on-board sensors to detect the presence of other vehicles and obstacles in

front of it. When the sensor detects an obstacle, the vehicle stops (or)

down. This system is most effective on straight pathways.

Figure: Forward sensing control system

Zone control: In this method, AGV system layout is divided into separate

zones. The operating rule is that NO vehicle is permitted to enter a zone if

that zone is already occupied by another vehicle.

Figure: Zone control system

By controlling the forward movement of

vehicles in the separate zones, collisions are prevented and the traffic in the

iii controlled.

5) Vehicle dispatching System

In an AGV system, the vehicles

must be dispatched in timely and efficient manner. The following

methods are used in AGV system to dispatch vehicles.

On-board control panel: Each guided vehicle is equipped with some form

of ON-board control panel for the purpose of manual vehicle control,

vehicle programming and other functions. Most commercial vehicles can

be dispatched by means of this control panel to a given station in the

AGVS layout.

Remote Call stations: The simplest call station is a press button mounted

at the load / unloads station. This transmits a hailing signal for any

available vehicle in the neighborhood to pick up (or) drop off a load.

Central computer control: This method is used to accomplish automatic

dispatching of vehicles to the various stations in the layout according to the

preplanned schedule. It also responds to calls from various load / unload

stations.

The central computer issues commands to the

vehicles in the system regarding their destinations and operations. Radio

Frequency is commonly used to achieve the required communication links.

Applications of AGV

The following are the major applications of AGV.

1) Driverless train operations.

2) Storage and Distribution

3) Assembly line application

4) Flexible Manufacturing system

5) Office mail delivery

6) Hospital material transport

7) Material handling in mines and hot working condition.

Benefits of AGV

1) To avoid wastage of time in handling

1) Reduce the manpower in handling

3) Flexible approach because of computer, the path of AGV

can be easily altered (or) modified.

4) They decrease labour costs.

5) They can operate in hazardous environment

6) Reduced product damage.

7) It is safe because of its low speed, sensor capacity and warring

arrangement.

(Or)

(B) (i) Explain flexible machining system.(6 marks)

Flexible machining systems consist of several flexible automated

machine tools of the universal (or) special t which are flexibly

interlinked by an automatic workpiece flow system so that different

workpieces at the same time.

The characteristic feature is the external linkage of the machines.

Different machining times at the individual stations are compensated

for by central (or) decentralized workpiece buffer stores.

Flexibility is applied to machines because of CNC control and flow

of products from one machine to another which is possible through

flexible transport system.

Flexibility is characterized by the system's ability to adapt to

changes in the volume in the product mix and of the machining

process and sequences. This means that FMS will be able to respond

quickly to changing market and customer demands.

FMS Application

Some of the important FMS applications are listed below:

1) All types of machining operations

2) Assembly works

3) Sheet metal press working

4) Forging

5) Welding

6) Elastic Injection moulding

7) Inspection and Testing

FMS Benefits / Advantages

1) Higher machine utilization

2) Reduced number of tools and machines required

3) Reduced work-in-progress inventory

4) Reduced manufacturing lead time

5) Reduced cycle time

6) Decreased direct and indirect labour costs.

7) Improved product quality

8) Reduced space requirements

9) Quicker response to market change

10) Flexibility within family parts.

(ii) Briefly explain various types of robot sensor. (6 marks) For certain robot applications, the type of

workstation control using interlocks is not adequate. The robot must take

on more humanlike senses and capabilities in order to perform the task in a satisfactory way. These senses and capabilities include vision and hand-eye

coordination, touch and hearing.

Accordingly, we will divide the types of sensors used in robotics into the following three categories.

1. Vision sensors

2. Tactile and proximity sensors 3. Voice sensors

1. Vision sensors Computerized vision systems will be an important technology in

future automated factories. Robot vision is made possible by means of a

video camera, a sufficient light source, and a computer programmed to

process image data.

The camera is mounted either on the robot (or) in a fixed

position above the robot so that its field of vision includes the robot's work

volume. The computer software enables the vision system to sense the

presence of an object and its position and orientation.

Vision capability would enable the robot to carry out the

following kinds of operations:

Retrieve parts which are randomly oriented on conveyors.

Recognize particular parts which are intermixed with other objects.

Perform visual inspection tasks.

Perform assembly operations which require alignment.

2. Tactile and proximity sensors

Tactile sensors

Tactile sensors provide the robot with the capability to respond I to

contact forces between itself and other objects within its work d volume. Tactile sensors can be divided into two types:

1. Touch sensors

2. Stress sensors (also called Force sensors)

Touch sensors are used simply to indicate whether contact has been made with an object. A simple micro switch can serve the purpose of

a touch sensor. Stress sensors are used to measure the magnitude of

the contact force. Strain gauge devices are typically employed in force-measuring sensors.

Proximity sensors

Proximity sensors are used to sense when one object is close to another object. On a robot, the near the e proximity sensor would be

located (or) near the end effectors.

The sensing capability can be engineered by means of optical proximity devices, eddy current proximity detectors, magnetic-field

sensors or other devices.

In robotics, proximity sensors might be used to indicate the presence (or) absence of a workpart (or) other object. They could Also helpful

in preventing injury to the robot’s human coworkers in the factory.

3. voice sensors Another type of robotics sensors is vice sensing (or) voice

programming. Voice programming can be defined as the oral communication of commands to the robot (or) other machine.

(Voice programming is also used in NC part programming). The

robot controller is equipped with a speech recognition system which analyzes the voice input and compares it with a set of stored word

patterns.

When a match is found between the input and the stored vocabulary word, the robot performs some action which corresponds to that

word.

Voice sensors would be useful in robot programming to speed up the programming procedure, just as it does in NC programming.