CLICK ON The X-Upper Right of Main Window.

12. BICYCLE.GPS

Simulation of a bicycle factory.

Problem Statement

A factory assembles bicycles, employing the following staff, 2 clerks, 3 framers, 1 saddler, 1 handler, 1 wheeler, 1 pedaler, 4 assemblers, and 3 packers. The company commences to assemble a bicycle, every 50±10 minutes. The clerical department prepares the delivery documents, instructions, tool kit and invoice.

Each department withdraws the component required for a particular order from stock, inspects (3±1 minutes) and prepares it for assembly. The frame is manufactured and takes 65 minutes, exponentially distributed. When the components are available, they are assembled. This takes on average 90 minutes, with a standard deviation of 10 minutes. When the delivery documents, tool kit, and the assembled bicycle, are ready, they are packed (40±5 minutes), in preparation for delivery.

1.Find the utilization of the staff in each department.

2.Determine the transit times of customers’ orders.

3.Should the number of staff be changed in any department.?

4.Simulate the bicycle factory assembly operation, for 5 days.

Listing

; GPSS World Sample File - BICYCLE.GPS by Gerard F. Cummings

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**

*Bicycle Assembly Model *

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Orders FUNCTION P$Department,L6

1,Order/2,Frame/3,Saddle/4,Handlebars/5,Wheels/6,Pedals

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Transit TABLE M1,100,100,20

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Clerks STORAGE 2

Framers STORAGE 3

Saddlers STORAGE 1

Handlers STORAGE 1

Wheelers STORAGE 1

Pedalers STORAGE 1

Builders STORAGE 4

Packers STORAGE 3

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GENERATE 50,10 ;Order arrives for bicycle

SPLIT 5,Factory,Department ;Make 5 copies of order Order ENTER Clerks

ADVANCE 80,10 ;Prepare invoice LEAVE Clerks

Invoice MATCH Bicycle ;Synchronize with bicycle TERMINATE ;Transaction finished

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Factory TRANSFER FN,Orders ;Route to correct dept.

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Frame ENTER Framers

ADVANCE (Exponential(1,0,65)) ;Make frame ADVANCE 12,2 ;Inspect frame

LEAVE Framers

TRANSFER ,Build ;Send for assembly

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Saddle ENTER Saddlers ADVANCE 6,3 ;Get a saddle

ADVANCE 3,1 ;Inspect the saddle LEAVE Saddlers

TRANSFER ,Build ;Send for assembly

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Coordinated use of the FN mode TRANSFER Block labeled

Factory, the Order Function Entity, and the serializing SPLIT

Block automatically deliver department orders. Notice that the

C operand of SPLIT first increments the parent Transaction’s parameter to 1 and the newly created Transactions then have

2, 3, 4, 5, and 6 placed in the department parameter.

When all 5 suborders have been completed, they are combined at the ASSEMBLE Block labeled Build, a simulated delay represents the final assembly and pack steps, and the overall order completion time is tabulated.

The bottom model segment decrements the Termination Count once a day.

Running the Simulation

To run the simulation and create a Standard Report,

CHOOSE File / Open and in the dialog box

SELECT BICYCLE

and then

SELECT Open

Next, create the simulation.

CHOOSE Command / Create Simulation

then

CHOOSE Command / START and in the dialog box, replace the 1.

TYPE 5

SELECT OK

The simulation will end when 5 Transactions have entered the TERMINATE 1 Block. This represents 5 days of operation.

When the simulation ends, GPSS World writes a report to the default report file, Bicycle.1.1. As discussed in Chapter 1, the

Report extension will vary depending on saved simulations and previously existing reports. For our purposes, we will assume that this is the first time the simulation has been created and run giving an extension of 1.1.

This report will be automatically displayed in a window. If you close the window, you can reopen it by using the GPSS World File / Open in the Main Menu. Then you should choose Report

in the "Files of type" drop down box at the bottom of the

window. GPSS World reports are written in a special format. If you wish to edit the report, you will have to copy its contents to the clipboard and from there into a word processor. You will not be able to open the file directly in a word processor.

Discussion of Results

The utilization of the staff in each department is given under the Util. column of the Storages subreport. The Clerks are busiest with a utilization of 78%. To determine the most desirable staff levels, we need to experiment with the Storage definitions.

The distribution of order transit times is given by the Table

Transit. The average was about 235.5 minutes with a standard deviation of 51.2 minutes.

Inside the Simulation

Let us now explore the ending condition of the simulation which generated the Standard Report above. If you are not at the end of the simulation, please translate the model and run it again.

First let’s open the Storages Window. Press

CHOOSE Window / Simulation Window / Storages Window

This shows the utilization and current state of the 8 Storage Entities. Let’s use the SHOW Command to look at some System Numeric Attributes. First, the time delay for clerical operations. In the Main Window menu

CHOOSE Command / SHOW

and in the dialog box

TYPE ST$Clerks

This is the average holding time per unit of the Storage Entity Clerks.

Next, use the SHOW Command to look at the time delays associated with each department. In all cases, there appears to be no significant queuing. In other words, the need for additional personnel in any department is not suggested by the results. Perhaps we could get by with fewer personnel.

It would be easy to insert QUEUE, DEPART, and QTABLE Blocks to collect more detailed statistics. The final word on the predicted effects of personnel changes would, of course, be based on full simulations of the proposed changes using multiple replications and statistical analysis before final conclusions are drawn.

Please feel free to modify the parameters and Blocks of this simulation. If you wish to go on to the next lesson, close all