Simulation of flexible assembly system using tecnomatix

at Vietnamese-German University

Lecturer: M.Sc. B.Eng. Müller Bastian

By Group 4:

Bùi Minh Đức (ID:1549)

Phạm Đăng Khoa (ID:1543)

Nguyễn Quang Thanh (ID:1558)

Tsang Ping Wang (ID:1553)

Trương Thị Xuân Đào(ID:1538)

DATE : 1 July 2014

SIMULATION OF FLEXIBLE ASSEMBLY SYSTEM

Agenda

Preparation Realization EvaluationBottleneck Analysis - Improvement References

Agenda Preparation Basic decision Target system Structure of the simulation database Rough analytical estimation Modelling Validation Realization Simulation experiment Evaluation Bottle-neck Analysis - Improvement References

Basic Decision-Complexity of the task

Eight stations: one load/unload station A1, three identical single working stations A2, one single station A3,A4,A5 and one flexible machine at station A6.

Shifting parts system Sx, Sy at each station. Two parallel conveyor belts, in which station Ax is placed at B2 and pallets is circulating at

B1.

Basic Decision- Expected benefit of the simulation

Be able to run the experiment in a short period of time.

Bottle-neck analysis.

Development control strategy.

Evaluation the optimal of pallets on system.

Target

Understood how does the system work by building up a visualize model

Observe the modelling while 20,40 and 60 pallets working Determine the suitable optimal pallet. Figure out the bottleneck then improve system to increase the

throughput.

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Structure of the simulation database

Some other rules are important to keep in mind when building up the simulation model: Ax is shifted back to B1 in Sy, having

priority over those coming from the left on B1.

Pallets from station A23 can be shifted directly to A3 and from A6 directly to A1

Pallets can queue up in front of stations or Sx/Sy when the conveyor is moving with its normal speed.

Sx,Sy cannot function as buffers.

Main data of flexible assembly system can be divided into 2 groups as follows: Technical Data for describing the

system components. Data for describing the flow

operation of system.

Structure of the simulation database- Technical Data for describing the system components

Technical data of stations

Other technical data

Station Operation time (sec.)

Length of B1 (m)

Input buffer (m) Length of station (m)

Output buffer (m)

A1 15 2.0 1.2 0.4 0.4

A2 60 1.6 0.8 0.4 0.4

A3 20 1.6 0.8 0.4 0.4

A4 20 1.6 0.8 0.4 0.4

A5 20 1.6 0.8 0.4 0.4

A6 30 2.0 1.2 0.4 0.4

Data description Value Data description Value

Speed of conveyors (m/min) 18 Sx/Sy wide (m) 0.4m

Pallet length (m) 0.36 Loading/Unloading time(sec.) 7.5

Length between two stations(m) 0.4 Shifting time (sec.) 2

Structure of the simulation database- Process Flow Chart

Station A1: load unprocessed part and unload finished part.

Parts can either be processed in A2 first, then A3,A4,A5 or A3,A4,A5 first then A2.

Process in A3,A4,A5 can follow arbitrary sequence.

A6 can substitute for any of stations A3,A4,A5.

Rough analytical estimation

The flow time is calculated in scenario of only one circulating pallet in system in order to check the validation of simulation model.

Loading at A1 -> A2_1 -> A3 -> A4 -> A5 -> Unloading at A1Therefore 20 + 20 + 20 +7.5 =135s

The total length which parts has been traveled is L= LA1 + LA2 + LA3 + LA4 + LA5 + LSx-Sy = (1.2+0.4)+4.(0.8+0.4)+7.6 = 14(m)

Conveyors move with the same speed 18m/min, so transportation time can be determined as the equation below

sThe number of shifting times when parts moving as the sequence above is 10 times,each time take 2 seconds, so the shifting time is 20s

secondsThe number of pallets are limited by the capacity of buffer B1:

Agenda Preparation Basic decision Target system Structure of the simulation database Rough analytical estimation Modelling Validation Realization Simulation experiment Evaluation Bottleneck Analysis - Improvement References

Modelling

The model is included three sub-frame: FAS model to define whole assembly system by connecting stations

from A1 to A6.

Modelling

The model is included three sub-frame: Ax sub model to define the working station (A2 to A6, in which A6 is a

flexible machine and can substitute for A3, A4, A5).

Modelling

The model is included three sub-frame: A1 sub model to define the load / unload station.

Validation

Validation 1: One pallet is circulated in the system and then determine its flowtime

- From rough estimate : Flowtime = 207.8 seconds

- From simulation : Flowtime = 207 seconds

Difference = (207.8-207)/207.8 = 0.38 % Validation 2: Number of pallet causing the system to blocked

- From rough estimate : Number of pallets = 44 pallets- - From simulation: Number of pallets = 44 pallets Validation 3: Length of conveyor belt B1

- From rough estimate : Length of conveyor = 16 m

- From simulation: Length of conveyor = 16 m

Conclusion: this simulation model is valid to simulate the flexible assembly system

Realization: Simulation Experiment- Planning

The number of pallets which are circulating in the system is the variable can influence to the through put time when the structure of system such as number of station, technical operation data cannot be changed. On the other hand, the number of pallets are limited by the capacity of buffer B1:

The experiment step is started with 1 pallet is circulating in system, then in each next experiment the number of pallets will be increased by 1 up to over the limit number : 44 pallets for validation. Due to this variable is deterministic; the observation in each experiment is 1.

Realization: Simulation Experiment - Execution

The simulation study is executed according to the trial plans to arrive at the desired output data. This study is facilitated by ExperimentManager of the Plant Simulation Software.

The first step is to define input values and output values of the experiments as showed in figure below.

And then the experiment is run with the defined settings, the full results of the simulation can be found as chart in the simulation evaluation part.

Simulation Evaluation- Determine throughput time

Experiment Number of Pallets Throughput Throughput time (minutes)

1 20 1439 7

2 40 1440 14

3 60 0 0

. The model is unable to calculate these above 46 pallets; the cause of this is that at some point all the belts and switches are full causing the system to lock.

Simulation Evaluation –Optimal number of pallets

The chart depicts that 14 pallets (Thoughput = 1440, cycle time 5 minutes) is the optimal pallets, with the target are maximise the throughput and

minimize the Cycle time

Note : Simulation with optimal pallets (14 pallets)

Bottle-neck Analysis - Improvement

Conclusion :A2 is a Bottleneck

Add one Station A2 :

Bottle-neck Analysis – Improvement : Option 1

* Capacity = 2

0 10 20 30 40 50 600

500

1000

1500

2000

2500 4 Station A2

Num of Pallets [Pallets]

Thou

ghpu

t [Pa

rts]

Optimal pallets = 21 pallets increase 7 Pallets

Thoughput = 1920 parts Increase 480 parts

Reanalysis the system when add one A2 machine


Should we add more A2 station ?

0 10 20 30 40 50 60 700

500

1000

1500

2000

2500

5 Station A2

Thou

ghpu

t [Pa

rts]

Add two A2 machines:

Bottle-neck Analysis – Improvement – Option 2

* Capacity = 3

Optimal pallets = 30 pallets increase 9 Pallets

Thoughput = 2100 parts Increase 180 parts


add one A2 machineAdd two A2 machine

Recommendation : Option 1

Option 1 Option 2

• optimal Pallets = 21 (pallets) • Max throughput = 1920 (parts) • % Throughput Increase =(1920-1440)/1440= 33,4%

• With 30 Pallets• Max throughput = 2100 (parts)• % Throughput Increase =(2100-1440)/1440= 45.8%

SUMMARY Success in modelling the Flexible Assembly System by Plant-

Simulation Software Throughput time with 20 pallets: 7minutes.

Throughput time with 40 pallets: 14minutes.

Throughput time with 60 pallets: system is blocked Optimal number of pallets: 14 (Throughput = 1440, cycle time 5

minutes) Improve Recommendation: add 1 machine A2

• optimal Pallets = 21 (pallets) • Max throughput = 1920 (parts) • % Throughput Increase 33,4%

References

[VDI-3633] Association of German Engineers. Simulation of systems in materials handling, logistics and production: Fundamentals. 2010. Beuth Verlag, Berlin.

[Book] Walter Terkaj, Tullio Tolio, Anna Valente.Design of Flexible Production Systems.(2009).

[Book] Steffen Bangsow. Manufacturing Simulation with Plant Simulationand SimTalk. (2009)

[Self-Guided Script]

Azrul Azwan Abdul Rahman, Bastian Muller. Tecnomatix Plant Simulation 11. Version 15.06.2014

THANK YOU FOR YOUR ATTENTION

Simulation of flexible assembly system using tecnomatix

Engineering

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