Systems Modelling and Simulation Assignment 2015-2016 Brunel University

8/18/2019 Systems Modelling and Simulation Assignment 2015-2016 Brunel University

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2015

Systems Modelling

and Simulation

MN5543 1446800

Brunel University

10/12/2015



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CONTENT

1. Introduction .................................................................................................................................. 8

2. Simulation model of the manufacturing system ........................................................................... 9

2.1. Sequences of components .................................................................................................... 9

2.2. Transfer Time ...................................................................................................................... 12

2.3. Run Setup ............................................................................................................................ 12

2.4. Resource Schedules ............................................................................................................ 13

2.5. Resource Failures ................................................................................................................ 14

2.6. Creating Orders ................................................................................................................... 16

2.7. Stations and Routes ............................................................................................................ 19

2.8. Suppliers ............................................................................................................................. 20

3. Identification the bottleneck process ......................................................................................... 23

3.1. Proposal for improvement .................................................................................................. 24

3.1.1. Increase resources in processes 1 and 3 ..................................................................... 25

3.1.2. New work shift ............................................................................................................ 26

3.1.3. Bonus .......................................................................................................................... 27

3.2. Comparison of results ......................................................................................................... 31

3.2.1. Throughput Time ......................................................................................................... 31

3.2.2. Work in Process ........................................................................................................... 32

3.2.3. Resource Utilization .................................................................................................... 33

4. Assembly Station......................................................................................................................... 34

5. Conveyor System ........................................................................................................................ 38

5.1. Bonus .................................................................................................................................. 42

CONCLUSION ...................................................................................................................................... 45

REFERENCES ........................................................................................................................................ 46



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INDEX OF FIGURES

Figure 1. Flowchart of the manufacturing systems ............................................................................... 9

Figure 2. Component n Process Plan................................................................................................... 10

Figure 3. Steps, Component n Step n .................................................................................................. 11

Figure 4. Assignment of Process Time ................................................................................................ 11

Figure 5. Component Sequence .......................................................................................................... 11

Figure 6. Members of the Component Sequence ............................................................................... 11

Figure 7. Transfer Time ....................................................................................................................... 12

Figure 8. Expression for Transfer Time ............................................................................................... 12

Figure 9. Run Setup ............................................................................................................................. 13

Figure 10. Station n Machine .............................................................................................................. 13

Figure 11. Station Schedule ................................................................................................................ 14

Figure 12. Station Schedule ................................................................................................................ 14

Figure 13. Failures, Station 5 Machine Failure .................................................................................... 15

Figure 14. Failure module, Station 5 Machine Failure......................................................................... 15

Figure 15. Statistic module, Station 5 Machine State ......................................................................... 15

Figure 16. Set Basic Process ................................................................................................................ 16Figure 17. Picture Name – Members .................................................................................................. 16

Figure 18. Entity Pictures – Members ................................................................................................. 16

Figure 19. Edit entity pictures for components 1, 2, 3, 4 & 5 .............................................................. 17

Figure 20. Link between Type.Component n and Picture.Component n ............................................ 17

Figure 21. Create Orders ..................................................................................................................... 18

Figure 22. Orders Types and Sequences ............................................................................................. 18

Figure 23. Assignments ....................................................................................................................... 18

Figure 24. Station n Station ................................................................................................................. 19

Figure 25. Route from Station n .......................................................................................................... 19

Figure 26. Process n ............................................................................................................................ 20

Figure 27. Station 2 Machine as resource of the Process 2 ................................................................. 20

Figure 28. Process n. Queue, FIFO ...................................................................................................... 20

Figure 29. Supplier n Time .................................................................................................................. 21

Figure 30. Supplier 1 Time .................................................................................................................. 21

Figure 31. Supplier 2 Time .................................................................................................................. 21



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Figure 32. Assignments ....................................................................................................................... 21

Figure 33. Supplier Delay .................................................................................................................... 22

Figure 34. Simulation for the manufacturing system .......................................................................... 22

Figure 35. Animation for the manufacturing system .......................................................................... 23

Figure 36. Identification of the Bottleneck Process ............................................................................ 24

Figure 37. Station 1 Machines ............................................................................................................. 25

Figure 38. Station 2 Machines ............................................................................................................. 25

Figure 39. Capacity factor for new and old machines ......................................................................... 25

Figure 40. Station 1 Machines incorporated in process 1 ................................................................... 26

Figure 41. New Resource Module ....................................................................................................... 26

Figure 42. Priority for components ..................................................................................................... 28

Figure 43. Queue Priority .................................................................................................................... 29

Figure 44. Process Analyser ................................................................................................................ 30

Figure 45. Improved model layout ...................................................................................................... 31

Figure 46. Comparison of throughput times ....................................................................................... 32

Figure 47. Comparison of work in process .......................................................................................... 33

Figure 48. Comparison of instantaneous utilization ........................................................................... 34

Figure 49. Type.Product n & Picture.Product n ................................................................................... 34

Figure 50. Assembly 1 Time ................................................................................................................ 34Figure 51. Assembly 2 Time ................................................................................................................ 34

Figure 52. Assembly Station ................................................................................................................ 35

Figure 53. Assembly Record ................................................................................................................ 35

Figure 54. Assign Product.................................................................................................................... 35

Figure 55. Assembly Decide ................................................................................................................ 36

Figure 56. Product Match n ................................................................................................................ 36

Figure 57. Product Batch n .................................................................................................................. 36

Figure 58. Assembly Process ............................................................................................................... 37

Figure 59. Route from Assembly Process ............................................................................................ 37

Figure 60. Plan Layout ......................................................................................................................... 38

Figure 61. Loading and unloading times ............................................................................................. 39

Figure 62. Loop Conveyor ................................................................................................................... 39

Figure 63. Loop Conveyor.Segment .................................................................................................... 39

Figure 64. Probability density function ............................................................................................... 40

Figure 65. Probability density function TRIA(20, 30, 40) ..................................................................... 40



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Figure 66. Next Stations ...................................................................................................................... 41

Figure 67. Start Sequence & Route from Station n ............................................................................. 41

Figure 68. Station n Station ................................................................................................................. 41

Figure 69. Conveyor System Layout .................................................................................................... 42



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INDEX OF TABLES

Table 1. Component routings and Process times ................................................................................ 10

Table 2. Waiting time (Queue) ............................................................................................................ 23

Table 3. Number waiting (Queue) ....................................................................................................... 23

Table 4. Accumulated wait time (Process) .......................................................................................... 24

Table 5. Difference of schedules ......................................................................................................... 27

Table 6. Total time per component type ............................................................................................ 28

Table 7. Best Combination .................................................................................................................. 30

Table 8. Percentage of improvement of throughput time .................................................................. 32

Table 9. Percentage of improvement of work in process ................................................................... 32

Table 10. Percentage of improvement of instantaneous utilization ................................................... 33

Table 11. Number out of components ............................................................................................... 38

Table 12. Throughput Time ................................................................................................................. 43

Table 13. Work in Process ................................................................................................................... 43

Table 14. Instantaneous Utilization .................................................................................................... 44



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INDEX OF EQUATIONS

Equation 1. Discrete Probability Distribution ...................................................................................... 18

Equation 2. Supplier Time ................................................................................................................... 21

Equation 3. Process Time for process 1 .............................................................................................. 26

Equation 4. Throughput time in Area.................................................................................................. 28

Equation 5. Queue Priority Equation .................................................................................................. 29

Equation 6. Throughput Time Equation .............................................................................................. 29

Equation 7. Assembly time ................................................................................................................. 37

Equation 8. Distance for the conveyor system.................................................................................... 39

Equation 9. Triangular distribution equation ...................................................................................... 40



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SYSTEMS MODELLING AND SIMULATION ASSIGNMENT 2015-16

1.

Introduction

The assignment consists of four main parts. Additionally, two bonuses will be presented, as listed

below:

Main Parts

Simulation model of the manufacturing system without assembly station

Identify the bottleneck process and present a proposal for improvement

Simulation model of the manufacturing system with assembly station

Introduce a conveyor system

Bonus

Queue priorities and the process analyser will be used to improve the original system

A transporter system will be introduced to compare with the conveyor system

The Development of the manufacturing system is divided into eight parts. However, its basic

operation can be studied according to the Figure 1.

Although Company A and B are two different enterprises; the common objective is maximize their

profits. In order to achieve that goal, they have created a strategic alliance; Company A does

outsourcing with Company B. In other words, the activities of Company B are done in the Company A

factory. For that reason, the assembly process and stations are in the same area.



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Figure 1. Flowchart of the manufacturing systems

2.

Simulation model of the manufacturing system

2.1.

Sequences of components

The company B has 5 machining stations and each component has a separate processing sequence

through the system and operation times at each machine are shown in Table 1.

http://localhost/var/www/apps/conversion/tmp/scratch_4/Assigment.vsd



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Table 1. Component routings and Process times

There are five components, therefore five sequences. They are created in the sequence module of

the advanced transfer panel . Furthermore, each of them is named “Component n Process Plan” , as

illustrated in Figure 2.

Figure 2. Component n Process Plan

The set of steps depends of each component. For instance, component 1 consists of five steps, as

shown in the first row of Table 1. These data are introduced as displayed in Figure 3. Additionally, it

is important to highlight that the set of steps can end in the Assembly Station or in the exit system.

To put it differently, if the model does not contain an Assembly Station, the final step is the exit

system. Contrary, if the model contains an Assembly Station the final step is the Assembly Station.

Components Step 1 Step 2 Step 3 Step 4 Step 5 Step 6

Stati on 1 Stati on 2 Stati on 3 Stati on 4

C1

Station 1 Station 5 Station 4 Station 2 Stati on 3C2

Stati on 2 Stati on 4 Stati on 5

C3

Sta ti on 1 Sta ti on 2 Sta ti on 3 Sta ti on 5 Sta ti on 4

C4

Stati on 2 Stati on 1 Stati on 3

C5

(5,15,20) (3,9,15) (5,10,12) (3,10,12) (4,8,12)

(6,10,14) (6,10,14) (5,8,15)

(11,13,15) (4,6,8) (6,9,12) (27,33,39)

(7,9,11) (7,10,13) (18,23,28)

Assembly

Station

AssemblyStation

(5,15,20) (5,8,10) (15,20,25) (8,12,16)

(6,8,10)

Assembly

Station

Assembly

Station

Assembly

Station



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Figure 3. Steps, Component n Step n

Each step has a process time as shown in Table 1. These times are given in minutes and represent a

triangular distribution. For example, the step 1 of the component 1 has a process time TRIA(5, 15,

20) min. It is imperative to point that the Process Time is saved as Attribute, as observed in Figure 4

Figure 4. Assignment of Process Time

Finally, the five sequences will be stored as a set. Arena offers two types of sets: basic set and

advanced set , the first one can be found in the Basic Process Panel and the other one can be found

in the Advanced Process Panel. For this part of the assignment, the advanced set will be used, due to

the Set Type required is the option “ Other ” . The set name is Component Sequence, as illustrated in

Figure 5 and the set members are “Component n Process Plan” as observed in Figure 6

Figure 5. Component Sequence Figure 6. Members of the Component Sequence



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2.2.

Transfer Time

The transfer times between each station is TRIA(1,1.5,2) minutes. This expression can be set up in

each station module. However, it is more efficiently if the transfer time is defined as an expression,

as indicated in Figure 7 and Figure 8. Alternatively, the transfer time could also have been defined as

a variable using the Assign Module.

Figure 7. Transfer Time

Figure 8. Expression for Transfer Time

2.3. Run Setup

The data are “Warm-up Period = 1 day, Replication Length = 2 Months and Number of Replication =

5”. The system does not require initialisation between replications”. It is extremely important to

highlight, it might be better to make just one long run and therefore the warm-up only will appear

once. Whether this concept is applied, the number of replications would be 1 and the replication

length would be 300 days, as shown in Figure 9. This is the same simulation effort as making the five

replications of length 60 days each.

As defined in article 2.1, there are five stations, consequently five machines. Moreover, these

machines work in shifts of eight hours and an hour break between the shifts. For this reason, the

number of hours per day is considered equal to 17, as displayed in Figure 9.



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Figure 9. Run Setup

2.4.

Resource Schedules

This section consists of three parts. First, it is necessary to create five machines in the Resource

Module of the Basic Process Panel ; each machine is named Station n Machine. Additionally, work

shifts are configured as “Based on Schedule” , the schedule name as “ Station Schedule” and the

Schedule Rule as “Preempt ” , as illustrated in Figure 10. In other words, machine will stop

immediately at the end of the current shift and the preempt component will be held back by Arena

until the beginning of the next shift and continue with its remaining processing time.

Figure 10. Station n Machine



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The second step is setting up the schedule; it can be done in the Schedule Module of the Basic

Process Panel. It is necessary to choose “Capacity” as Type and “Hours” as Time Units” , as shown in

Figure 11

Figure 11. Station Schedule

In the tab named Durations, work shifts and break will be configured. As defined in the paragraph

2.3, the capacity for the first work shift (eight hours) is one and the capacity for the break (one hour)

is zero. To put it easily, there will be one machine working in each station during the first work shift

and none during the break. This statement is depicted in the Figure 12. It is important to mark that

Arena starts the first work shift at 0:00 and the after the seventeenth hour the schedule will repeat

from beginning.

Figure 12. Station Schedule

2.5.

Resource Failures

This section consists of three parts. First is needed to activate the Failure Option in the “Station 5

Machine” , as can be observed in the last row of the Figure 10. The name of the failure is “ Station 5

Machine Failure” , as shown in Figure 13.

Although others authors recommend the Wait Option for the Failure rule, when the time between

capacity decrease (up time) is much larger than duration of the decrease (down time) (Kelton, et al.,

2003); in this paper the Preempt Option will be used, since a breakdown is an unexpected event.



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Moreover the Station 5 Machine can go into failure status at any time, regardless of whether the

entity has seized the resource or not.

Figure 13. Failures, Station 5 Machine Failure

The previous action adds a row in the Failure Module labelled “Station 5 Machine Failure”. The up

time (duration of the nominal capacity) is EXPO(120) min and the down time (duration of the

decrease) is EXPO(4) min, as shown in Figure 14.

Figure 14. Failure module, Station 5 Machine Failure

Finally, it is imperative to request extra information on the Station 5 Machine, specifically the

amount of the time the resource is in a failed state. This feature is achieved using the statistical

module, as can be seen in Figure 15. It will give statistics based on all the states of the Station 5

Machine (Busy, Idle and Failed).

The tab labelled Output File is used to save output data and later be analysed in the Output Analyser .

The file needs an extension *.dat, for instance “Station 5 Machine State.dat” . However, the Output

Analyser will not be studied in this paper.

Figure 15. Statistic module, Station 5 Machine State



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2.6.

Creating Orders

This section is divided into six parts. The objective for the first four steps is relating each component

with a particular picture, the aim for the next steps is creating the orders. First, it is necessary to

establish two sets. Contrary to the Figure 5, the Basic Set will be configured in this occasion; since

“Entity Picture” and “Entity Type” are required as Set Type. The labels are “Component Picture” and

“Component Type” respectively, as illustrated in Figure 16.

Figure 16. Set Basic Process

The second step is creating Picture Names and Entity Types. Each set will have five members because

there are five components, as can be observed in Figure 17 and Figure 18.

Figure 17. Picture Name – Members Figure 18. Entity Pictures – Members

The third step is editing the pictures of the components. It can be achieved using the Entity Pictures

option. In this example coloured balls have been selected to represent the five components, simply

because it is easy to identify them. However it is possible to select any picture from the libraries.



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Figure 19. Edit entity pictures for components 1, 2, 3, 4 & 5

The fourth step is linking each Entity Type with its Initial Picture. It can be done using the Entity

Module, as can be observed in Figure 20.

Figure 20. Link between Type.Component n and Picture.Component n

The fifth step is creating the orders. The order sizes and the time period between each order can be

configured in the Create Module, as follows: the time period describes an exponential rate of 24

hours and the order sizes follow a triangular distribution of (30,40,50).



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Figure 21. Create Orders

Finally, the percentage of the components in each order will be established in an Assign Module,

labelled “Orders Type and Sequences” , as shown in Figure 22.

Figure 22. Orders Types and Sequences

Orders follow a discrete probability distribution with the following data: 26% of C1s, 10% of C2s, 20%

of C3s, 14% of C4s and 30% of C5s. Therefore the Equation 1 depicts the cumulative distribution

function.

(0.26 , 1 , 0.36 , 2 ,0.56 , 3 ,0.7 , 4 , 1 ,5)

Equation 1. Discrete Probability Distribution

The Equation 1 will be stored in an Attribute named “Component Index” and the three sets created

previously: Component Sequence, Component Type and Component Picture will be in function of this

attribute, as shown in Figure 23.

Figure 23. Assignments



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2.7.

Stations and Routes

This section consists of three stages: Station Module, Process Module and Route Module. The Station

Module represents a physical place. For example, work stations or warehouses. The Route Module

depicts a physical path between stations.

Figure 24 and Figure 25 show the parameters to configure these modules. It should be noted that

the Route Time is the “Transfer Time” defined in section 2.2 and “By Sequence” is configured as the

Destination Type

Figure 24. Station n Station

Figure 25. Route from Station n

Figure 26 illustrates the Process Modules. There are five Process Modules because there are five

resources, defined in the Figure 10. The Process Time established in Figure 4 is used here as

Expression.



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Figure 26. Process n

The next step is establishing the resources of each process. The resources were defined in Figure 10.

For instance, the “Station 2 Machine” is the Resource Name of the Process 2, as shown in Figure 27

Figure 27. Station 2 Machine as resource of the Process 2

The final step is setting up the queue priorities; it can be done in the Queue Module. The Figure 28

shows the First in First out (FIFO) option. It means that at each of the machine stations, the highest

priority is given to the earliest orders.

Figure 28. Process n. Queue, FIFO

2.8.

Suppliers

This section is formed by three steps. The first one is storing the supplier times in the Expression

Module (Figure 29). Both suppliers follow a triangular distribution, TRIA(1,1.5,2) hours for supplier 1



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and TRIA(0.5,1,1.5) hours for supplier 2. These data can be saved as Expression Values, as shown in

Figure 30 and Figure 31.

Figure 29. Supplier n Time

Figure 30. Supplier 1 Time Figure 31. Supplier 2 Time

The second step is building the expression. Supplier 1 sends raw material for components 1, 2 and 3.

On the other hand, supplier 2 sends raw material for components 4 and 5. The Equation 2 represents

the Supplier Time, which varies with the type of component. In Figure 32 can be seen that the

expression has been stored as attribute because it is an entity feature.

( ≤3) × 1 + ( >3) × 2

Equation 2. Supplier Time

Figure 32. Assignments



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The third step is using a Delay Module to apply the Supplier Delay . It could have also used a Delay

Block ; however it is important to keep the harmony in the model.

Figure 33. Supplier Delay

This is the last step for the manufacturing system without assembly station. The simulation model

with animation and the report file can be edited following the next links.

Simulation model with animation (CD:\ 01 Without Assembly Station\01 Without AS.doe)

Report file (CD:\ 01 Without Assembly Station\01 Without AS.pdf)

The simulation model and the animation are presented in Figure 34 and Figure 35 respectively.

Figure 34. Simulation for the manufacturing system

http://localhost/var/www/apps/conversion/tmp/scratch_4/01%20Without%20Assembly%20Station/01%20Without%20AS.doe


http://localhost/var/www/apps/conversion/tmp/scratch_4/01%20Without%20Assembly%20Station/01%20Without%20AS.pdf






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Figure 35. Animation for the manufacturing system

3. Identification the bottleneck process

Based on (Groover, 2010) the bottleneck is a constraint of the system. It restricts the system

throughput. In industry, bottlenecks limit the system performance in terms of capacity, money or

time. Thus, in this report, bottlenecks will be defined in terms of time and capacity. Three indicators

are used to identify the constraint of the model

Accumulate Wait Time (Process)

Waiting Time (Queue)

Number Waiting (Queue)

Table 2. Waiting time (Queue) Table 3. Number waiting (Queue)

Queue Waiting time Percentage

Process 1.Queue 3.1254 34%





Total 9.2867 100%

Queue Number Waiting Percentage

Process 1 4.0374 34%

Process 2 3.0671 26%

Process 3 4.0066 34%

Process 4 0.0967 1%

Process 5 0.7398 6%

Total 11.9476 100%



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Table 4. Accumulated wait time (Process)

The results are presented in Figure 36. The Waiting Time, Accum Wait Time and Number Waiting for

processes 1 and 3 are around 34%, meanwhile process 2 barely reaches 26%. Consequently,

processes 1 and 3 are the bottlenecks of the system.

Figure 36. Identification of the Bottleneck Process

3.1.

Proposal for improvement

There are mainly two options to improve the statistics for processes 1 and 3:

Increase the capacity of the resources 1 and 3

Increase resources in the processes 1 and 3

Both options produce the same result. However, in this paper the second option will be studied; just

because it permits to create independent work shifts and differentiate the capability of each

machine. There are other simpler options to enhance the statistics. For instance, reduce the delays

Process Accum Wait Time Percentage

Process 1 12420.6 34%

Process 2 9611.85 26%

Process 3 12361.38 33%

Process 4 337.59 1%

Process 5 2339.7 6%

Total 37071.12 100%



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of the suppliers or reorganize the purchase orders. However, this assignment assumes those data

are constant.

3.1.1.

Increase resources in processes 1 and 3

New machines are 30% faster than the old ones. In other words, Process Time will be improved 30%

with this acquisition. Additionally, the characteristics of each machine are:

Doosan Lynx 220LSY, for process 1 (CD:\Doosan Lynx 220LSY.mp4)

Doosan Puma 2100MS, for process 3 (CD:\Doosan Puma 2100MS.mp4)

Two sets of resources were created, “Station 1 Machines” and “ Station 3 Machines” . Further, each

set contains two members, as shown in Figure 37 and Figure 38.

Figure 37. Station 1 Machines Figure 38. Station 2 Machines

In order to improve the Process Time, a variable named “Factor” was introduced. Initial Value “1”

represents the capacity for old machines and Initial Value “0.7” depicts the capacity for new

machines, as illustrated in Figure 39.

Figure 39. Capacity factor for new and old machines

http://localhost/var/www/apps/conversion/tmp/scratch_4/Doosan%20Lynx%20220LSY.mp4


http://localhost/var/www/apps/conversion/tmp/scratch_4/Doosan%20Puma%202100MS.mp4






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The next step is incorporating the corresponding set in each process. It can be done in the tab

Resources of the Pr ocess Module. For example Figure 40 shows the set "Station 1 Machines"

incorporated in process 1. Moreover, Equation 3 represents the expression for process 1 to calculate

the new Process Time.

Figure 40. Station 1 Machines incorporated in process 1

1 = × (ℎ 1 )

Equation 3. Process Time for process 1

3.1.2.

New work shift

The new machines will work at a different work shift. To achieve this requirement, a secondschedule name “New Schedule” is created, as can be observed in Figure 41. The new machines will

start the work shift one hour later, in other words at 01:00 am. The difference between the original

schedule and the new one can be observed in Table 5.

Figure 41. New Resource Module

Time Table Station Schedule New Schedule

00:00 - 01:00Shift 1

Break

01:00 - 02:00 Shift 1



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02:00 - 03:00

03:00 - 04:00

04:00 - 05:00

05:00 - 06:00

06:00 - 07:00

07:00 - 08:00

08:00 - 09:00 Break

09:00 - 10:00

Shift 2

Break

10:00 - 11:00

Shift 2

11:00 - 12:00

12:00 - 13:00

13:00 - 14:00

14:00 - 15:0015:00 - 16:00

16:00 - 17:00

17:00 - 18:00 Break

Table 5. Difference of schedules

3.1.3. Bonus

The system can be improved even more. According to (Groover, 2010) Throughput Time (TT) is the

amount of time required for a product to pass through a manufacturing process, thereby being

converted from raw materials into finished goods. In other words, TT covers the entire period from

when the entity enters to manufacturing until it exits from manufacturing. Furthermore, it includes

the following time intervals:

Processing time. This is the time spent transforming raw materials into finished goods.

Inspection time. This is the time spent inspecting raw materials, work-in-process, and

finished goods, possibly at multiple stages of the production process.

Transfer time. This is the time required to move items into and out of the manufacturing

area, as well as between workstations within the production area.

Wait time. This is the time spent waiting prior to the processing.

Arena adds five values to calculate this parameter, as depicted in Equation 4



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ℎℎ = + + + + ℎ

Equation 4. Throughput time in Area

Analysing the report offered by Arena, it can be concluded that Wait Time has a weight of 77.4% of

the Total Time, as presented in Table 6. In other words, the more the Wait Time is improved, the

more the Total Time is reduced.

Entity VA time NVA time Wait Time Transfer Time Other Time

Throughput

time

Type.Component 1 0.8823 0 8.8005 0.1251 1.5037 11.3116

Type.Component 2 1.1526 0 10.2404 0.1505 1.4943 13.0378

Type.Component 3 0.6997 0 3.9964 0.0998 1.5021 6.298

Type.Component 4 0.7921 0 6.608 0.1503 1.005 8.5554

Type.Component 5 0.4885 0 8.5963 0.1001 0.9973 10.1822

Total 4.0152 0 38.2416 0.6258 6.5024 49.385

Percentage 8.1% 0.0% 77.4% 1.3% 13.2% 100.0%

Table 6. Total time per component type

In the original model, the rule for Queue Priorities was FIFO; in this section the objective is assigning

priorities to components to reduce the Wait Time and consequently, the Throughput Time. The First

step is creating five variables labelled Priority C1, …, Priority C5, as shown in Figure 42.

Figure 42. Priority for components



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A new Assign Module will be created, named “Assign Priority” . In this module each component will

be linked with its priority, according to the Equation 5. It should be observed that the result of that

expression is stored in an Attribute named “Priority” .

Name:

Type:

Attribute Name:

New Value:

Assign Priority

Attribute

Priority

(Component Index == 1) * Priority C1 + (Component Index == 2) * Priority C2 +

(Component Index == 3) * Priority C3 + (Component Index == 4) * Priority C4 +

(Component Index == 5) * Priority C5

Equation 5. Queue Priority Equation

The last step is setting up “Lowest Attribute Value” as the rule for the Queue Priority , as shown in

Figure 43. It means that the priority will be given to the entity with the lowest attribute. It should be

observed that the Attribute Name was defined in the previous step.

Figure 43. Queue Priority

Before searching the best combination is necessary to build the Response Expression. It will be built

in the same Assign Module of the previous step, according to the Equation 6.

Name:

Type:

Attribute Name:

New Value:

Assign Priority

Variable

Throughput Time

TAVG(Type.Component 1.TotalTime) + TAVG(Type.Component 2.TotalTime) +

TAVG(Type.Component 3.TotalTime) + TAVG(Type.Component 4.TotalTime) +

TAVG(Type.Component 5.TotalTime)

Equation 6. Throughput Time Equation



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The challenge is finding the best priority combination to reduce the Throughput Time. There are five

components and five priorities, therefore 120 combinations (5!). Those 120 combinations can be

evaluated in the Process Analyser . The Table 7 shows the best combination. The Process Analyser file

can be edited in the next link:

Process analyser file (CD:\07 With Assembly Station and Improved\07 With AS and

Improved.pan)

The Figure 44 shows the Process Analyser with all combinations.

Table 7. Best Combination

Figure 44. Process Analyser

The simulation model with animation and the report file can be edited following the next links.

Queue Priority

Type.Component 1 2Type.Component 2 1

Type.Component 3 5

Type.Component 4 4

Type.Component 5 3

http://localhost/var/www/apps/conversion/tmp/scratch_4/07%20With%20Assembly%20Station%20and%20Improved/07%20With%20AS%20and%20Improved.pan





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Simulation model with animation (CD:\07 With Assembly Station and Improved\07 With AS

and Improved.doe)

Report file (CD:\07 With Assembly Station and Improved\07 With AS and Improved.pdf)

The Figure 45 depicts the improved model layout. Contrary to the Figure 35, this new layout has the

two new machines.

Figure 45. Improved model layout

3.2.

Comparison of results

3.2.1. Throughput Time

The Throughput Time decreased in overall 35%, according to Table 8 and Figure 46. Component 1, 2

and 3 reported an improvement around 30%. However, Component 5 had a dramatically decrement

of 63%. On the other hand, Component 3 increases 1%.

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Table 8. Percentage of improvement of throughput time

Figure 46. Comparison of throughput times

3.2.2.

Work in Process

Similarly to previous article, Work in Process decreased in overall 40% (Table 9 & Figure 47).

Component 1, 2 and 3 reported an improvement around 35%. However, Component 5 had a

dramatically decrement of 62%.

Table 9. Percentage of improvement of work in process

EntityThroughput time

Original

Throughput time

Improved

Percentage of

Improvement

Type.Component 1 11.1321 7.8129 30%

Type.Component 2 12.8801 8.3039 36%

Type.Component 3 6.2899 6.3233 -1%

Type.Component 4 8.3722 5.5758 33%

Type.Component 5 10.0447 3.6907 63%

Total 48.719 31.7066 35%

EntityWork in Process

Original

Work in Process

Improved

Percentage of

Improvement

Type.Component 1 4.6812 3.1401 33%

Type.Component 2 2.0674 1.3351 35%

Type.Component 3 1.971 1.7951 9%

Type.Component 4 1.9426 1.223 37%

Type.Component 5 4.8034 1.83189 62%

Total 15.4656 9.32519 40%



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Figure 47. Comparison of work in process

3.2.3.

Resource Utilization

Instantaneous Utilization changed around 11%. The biggest changes are in Station 1 Machine and

Station 3 Machine, this modification is due to the addition which took place. The remaining three

machines maintain almost the same level of resource utilization; although, they vary near 5%. Table

10 and Figure 48 display these statistics.

Table 10. Percentage of improvement of instantaneous utilization

Resource

Instantaneous

Utilization

Original

Instantaneous

Utilization

Improved

Percentage of

Improvement

Station 1 Machine 0.2452 0.2008 18%

Machine 1_New 0.0945

Machine 1_Old 0.1063



Machine 3_New 0.1245

Machine 3_Old 0.1546



Total 1.1914 1.0585 11%

-

-

-

-



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Figure 48. Comparison of instantaneous utilization

4. Assembly Station

This section is composed of seven steps. Firstly, is needed to create entities representing to Product

1 and Product 2. This paragraph covers the same four stages done in article 2.6 Creating Orders.

Figure 49 displays the result.

Figure 49. Type.Product n & Picture.Product n

The next step is creating the expressions representing the Assembly Time. This paragraph covers the

same first stage done in article 2.7. Figure 50 and Figure 51 display the result.

Figure 50. Assembly 1 Time Figure 51. Assembly 2 Time



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The third step is creating a station labelled “ Assembly Station” , as shown in Figure 52. It represents

the entrance to the assembly process and the warehouse of components.

Figure 52. Assembly Station

The fourth step is developing a programming logic to divide the statistics before and after the

Assembly Station, because the Waiting Time in Queue of components should not be influenced by

the Match Queue or Batch Queue. This is due to the assembly process is part of Company A, as

explained in article 1 Introduction.

This logic can be programming using a combination of Record Module plus Assign Module. “ Assembly

Record ” is the name for the Record Module, as shown in Figure 53. “Assign Product” is the label for

the Assign Module, as displayed in Figure 54

Figure 53. Assembly RecordFigure 54. Assign Product

Then, it is necessary to separate the components to store them in the warehouse of components.

The Figure 55 shows a Decide Module named “ Assembly Decide” . In this module are written four

paths, however there is a fifth path; the option “else” .



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Figure 55. Assembly Decide

The warehouse of components can be modelled using a combination of Match Module plus Batch

Module. Match Modules gather the components; for instance, Product 1 is formed by Component 1,

2 and 3. For this reason, the tab named number to match is “3” . Similarly, Product 2 consists of

Component 4 and 5. Figure 56 displays the parameters for Match Modules.

Figure 56. Product Match n

Batch Modules sends the components together to the assembly process. Additionally, entities

named “Type.Product 1” and “Type.Product 2” (created at the beginning of this article) are used as

Representative Entity Type. Figure 57 illustrates the parameters for Batch Modules.

Figure 57. Product Batch n

The sixth step is creating a process named “Assembly Process” , as indicated in Figure 58. Equation 7

represents the assembly time, which varies with the type of product.



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= ((. 1)) × 1 + ((. 2))× 2

Equation 7. Assembly time

Figure 58. Assembly Process

The last step is the Route Module. It is important to point that unlike the Route Modules created in

the article 2.7 Stations and Routes; in this step the Destination Type is “Station” , because after this

module the products will go directly to the “Exit System Station” . Figure 59 displays this module.

Figure 59. Route from Assembly Process




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Simulation model with animation (CD:\02 With Assembly Station\02 With AS.doe)

Report file (CD:\02 With Assembly Station\02 With AS.pdf)

In order to find the best position for the assembly station is necessary to analyse the indicator

named Number Out in the tab of process of the report. The assembly process receives components

from three processes, as indicated in Table 1. Process 3 and 4 send more quantity of components,

around 41% and 36% respectively (Table 11). Consequently, the assembly station should be located

between stations 3 and 4, as shown in Figure 60.

Table 11. Number out of components

Figure 60. Plan Layout

5. Conveyor System

This section consists of fourth steps. Firstly, variables for “Load Time” and “Unload Time” were

created, as shown in Figure 61. In addition, the loading and unloading times have a value of 0.25

min. In other words, the conveyor temporarily stops while the load or unload occurs.

Process Number Out Percentaje

Process 3 3960 41%

Process 4 3447.8 36%

Process 5 2167.6 23%

Total 9575.4 100%

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Figure 61. Loading and unloading times

The conveyor system name is “Loop Conveyor” . Additionally, this type of conveyor is “Non-

Accumulating” , it means when an entity accesses space, the entire conveyor stops moving. The tab

“Max Cells Occupied” represents the maximum number of cells that entity requires to be

transported. Furthermore, size of each cell is 3 ft. Parameters can be observed in Figure 62.

Figure 62. Loop Conveyor

The third step is configuring the conveyor segments; it was realized in the Segment Module of the

Advanced Transfer Panel , as shown in Figure 63. It is important to note that “Order Release” is the

Beginning Station.

Figure 63. Loop Conveyor.Segment

The actual Transfer Time corresponds to a triangular distribution TRIA(1,1.5,2) min. However,

considering the Uniform Motion, the expression for distance is obtained using the Equation 8.

= ×

= 2 0 × (1,1.5,2)

= (20,30,40)

Equation 8. Distance for the conveyor system



40

Figure 64 and Equation 9 depict the probability density function and triangular distribution equation

for distance = TRIA(20,30,40) ft. This expression could have been calculated in Microsoft Excel; in this

assignment the Input Analyser was used.

Figure 64. Probability density function

2( − 2 0)(40−20)(30−20) 20 ≤ ≤ 30

2(4 0 − )(40−20)(40−30) 30 ≤ ≤ 40

0 ℎ

Equation 9. Triangular distribution equation

The software generated 5000 elements. However, just eight of those are necessary and were

introduced as measures of length in the Segment Module, as shown in Figure 66. Moreover, Figure

65 shows the input analyser results.

Figure 65. Probability density function TRIA(20, 30, 40)



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Figure 66. Next Stations

The fourth and last step is replacing all Route Modules by Leave Modules, as shown in Figure 67.

Similarly, the Stations Modules by Enter Modules, as displayed in Figure 68.

Figure 67. Start Sequence & Route from Station n

Figure 68. Station n Station


Simulation model with animation (CD:\05 Conveyor\05 Conveyor.doe)

Report file (CD:\05 Conveyor\05 Conveyor.pdf)

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Figure 69. Conveyor System Layout

5.1.

Bonus

The conveyor system will be compared and contrasted with a transport system. The Transfer Time is

the same as used in conveyor system. Additionally, it was assumed that there are two transport

units. The indicators to compare both models are:

Throughput Time

Work in Process

Resource Utilization

The Throughput Time decreased in overall 16%, according to Table 12. Components 2 and 5 reported

the best numbers, around 22%. However, Components 1 and 3 only had a slight increase about 7%.

Component 4 is the third best with a decent 12%.



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Table 12. Throughput Time

The Work in Process decreased in overall 31%, according to Table 13. Components 1 and 4 improved

around 27%. However, Components 2 and 5 enhanced significantly about 37%. Although, Component

3 reported the lowest number; it is a remarkable improved of 17%.

Table 13. Work in Process

The Instantaneous Utilization is the steadiest indicator. It reported an average of 20%, according to

Table 14. There is barely five points of difference between the highest mark of 22% for Station 3

Machine and the lowest of 17% for Station 5 Machine.

EntityThroughput time

Conveyor

Throughput time

Transporter

Diference of

Percentage

Type.Component 1 12.206 11.1097 9%

Type.Component 2 15.2866 12.1739 20%

Type.Component 3 6.7027 6.3487 5%

Type.Component 4 9.4319 8.313 12%

Type.Component 5 12.2111 9.2118 25%

Total 55.8383 47.1571 16%

EntityWIP

Conveyor

WIP

Transporter

Diference of

Percentage

Type.Component 1 5.2069 3.8526 26%

Type.Component 2 2.5176 1.5954 37%

Type.Component 3 2.0574 1.7172 17%

Type.Component 4 2.1162 1.5247 28%

Type.Component 5 5.9991 3.6902 38%

Total 17.8972 12.3801 31%



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Table 14. Instantaneous Utilization


Simulation model with animation (CD:\04 Transporter\04 Transporter.doe) Report file (CD:\04 Transporter\04 Transporter.pdf)

Resource

Instantaneous

Utilization

Conveyor

Instantaneous

Utilization

Transporter

Diference of

Percentage






Total 1.2201 0.9788 20%

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CONCLUSION

This paper represents a manufacturing system. Further, it consists of five process and five

components. The Chapter 2 describes sequences, transfer times, schedules, failures, stations and

routes. At this part, the manufacturing system has some flaws. For instance, resources to move

components from one station to another are unknown. However, in the analysis is possible to draw

some conclusions.

Machines 1 and 3 receive more components than others. Furthermore, Components 1 & 2 require

more time to be processed. These issues can be solved incrementing the process capacity or

reorganizing the purchase orders. The second option is the most cheap and intelligent solution.

However, Company B is facing an increase in demand. For that reason, the first option was

implemented; an extra machine was added to stations 1 and 3. In addition, queue priorities were

modified to give preference to Components 1 & 2.

These actions led to remarkable improvements; throughput time decreased 35%, work in process

40% and resource utilization around 11%. Although, these numbers are very promising, the

imperative conclusion would have been analysing the profits received due to these changes, as

Eliyahu Goldratt relates in his book “The Goal ” .

With the addition of an assembly machine was necessary to develop a business strategy to relate

Companies A and B. Company A does outsourcing with Company B. In other words, the activities of

Company B are done in the Company A factory. Additionally, the warehouse of components is

crucial, due to it can be seen as a new restriction for the system, considering that the number of

components stored is between 742 and 958 (This statistic can be read in the label "Product Match

2.Queue2" of "Waiting Time" ).

The conveyor was contrasted with a transport system. The last one reported important

improvements; throughput time decreased 16%, work in process 31% and resource utilization

around 20%. This results are due to the conveyor system is "Non-Accumulating" . It would be

interesting to compare the transport system vs. an “ Accumulating” conveyor system.



REFERENCES

Groover, M. P., 2010. Fundamentals of Modern Manufacturing: Materials, Processes, and

Systems. 4 ed. Bethlehem(Pennsylvania): John Wiley & Sons Inc..

Kelton, D. W., Sadowski, R. P. & Sadowski, D. A., 2003. Simulation with Arena. 4 ed. New

York: McGraw-Hill Education.

Documents

Systems Modelling and Simulation Assignment 2015-2016 Brunel University