Manual of simul8

General Cable Flexibles Factory Simulation

An Introduction
to SIMUL8

Daniel W. McGregor & Matthew J. Cain

Department of Management
College of Business and Economics
University of Canterbury
New Zealand

Introduction to SIMUL8

Contents
What is SIMUL8...................................................................................................................... 3
Starting SIMUL8.................................................................................................................. 4
1. Using Help ................................................................................................................... 4
2. Toolbox....................................................................................................................... 5
2.1. Work entry point .................................................................................................. 5
2.2. Storage area......................................................................................................... 5
2.3. Work Center ........................................................................................................ 5
2.4. Work Exit Point ................................................................................................... 5
2.5. Resources ............................................................................................................ 5
2.6. Work Items .......................................................................................................... 6
3. Controlling the machines .............................................................................................. 6
3.1. Distribution.......................................................................................................... 6
3.2. Required Resources.............................................................................................. 6
3.3. Efficiency ............................................................................................................ 6
3.4. Routing in ............................................................................................................ 6
3.5. Routing out .......................................................................................................... 6
3.6. Label actions ........................................................................................................ 6
3.7. Priority ................................................................................................................ 7
3.8. Contents .............................................................................................................. 7
3.9. Graphics .............................................................................................................. 7
4. Getting started.............................................................................................................. 7
5. Example 1.................................................................................................................... 8
6. Efficiencies.................................................................................................................. 9
7. Work Items .................................................................................................................. 9
8. Clock Properties..........................................................................................................10
9. Warm up period ..........................................................................................................10
10. Results collection period ..........................................................................................10
11. Graphics .................................................................................................................11
12. Example 2...............................................................................................................11
13. Results....................................................................................................................13
14. Trials ......................................................................................................................14
15. Routing in and out ...................................................................................................14
15.1. Routing In.......................................................................................................14
15.2. Routing out .....................................................................................................15
16. Batching .................................................................................................................16
17. Travel times............................................................................................................16
18. Sub windows...........................................................................................................17
19. Labels.....................................................................................................................17
20. High Volume ..........................................................................................................18
21. Resources ...............................................................................................................18
22. Groups....................................................................................................................19
23. Change-Over times..................................................................................................19
24. Inputting data parameters.........................................................................................19
25. Exporting data/Results to Excel................................................................................21
26. Visual Logic ...........................................................................................................21
27. Example of visual Logic .........................................................................................21
28. Example 3...............................................................................................................22
CASE STUDY........................................................................................................................25
References..............................................................................................................................28
Authors...................................................................................................................................28
Appendix A: Order of Operations.............................................................................................29

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What is SIMUL8

SIMUL8 is a computer package for Discrete Event Simulation. It allows you to create a
visual model of the system under investigation by drawing objects directly on the screen.
Typical objects may be queues or service points. The characteristics of the objects can be
defined in terms of, for example, capacity or speed.

Once the system h been modelled a simulation can be undertaken. The flow of Work
as
Items around the system is shown by animation on the screen so that the appropriateness of
the model can be assessed.
When the structure of the model has been confirmed, then a number of trials can be run
and the performance of the system described statistically. Statistics of interest may be
average waiting times, utilisation of Work Centers or Resources, etc. Shalliker and
Ricketts [2002].

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Starting SIMUL8

On starting SIMUL8, the screen below will open.

This page will allow you to:
- Open an existing simulation that came with SIMUL8
- Open one of your own recent simulations
- Start a new simulation.

1. Using Help
SIMUL8 has a very good online
help section built into the program.
To access this click on the help
menu on the main screen then
index or use the F1 key. This will
open an index to all the help Items
within SIMUL8.

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2. Toolbox
Each of the sections below 2.1 to 2.6, are basic icons that are used within simulation.

2.1. Work entry point

This is where Work Items (Job orders) arrive into the system. How they arrive can
be controlled by the arrival distribution and parameters associated. [See section on
controlling machines to see how to control]. The Work Items can arrive singly or in
batches (multiple Work items together).

2.2. Storage area

This is where Work is held in a queue while waiting to be processed. This gives a
buffer for the Working machines to allow them to continue Working. [They are usually
required before all the Work Centers so the Workflow is not blocked; SIMUL8 will show
an error if the Work Center blocks the Workflow]. You can control the capacity of the
Storage area, the shelf life of the Work Items (How long it lasts) in the queue and how the
queue sorts the Work Items it contains (First in, First out or Last in, First out, or priority
etc).

2.3. Work Center

This is where the Work is performed on the Work Items by either machines or
Workers [See section 3]. You control the time and distribution that the Work takes at each
machine, and can collect a certain number of Work Items from different areas within the
simulation and give probabilities or specific Routing out after processing [see Routing in
and out]. Used mainly to change the state of the Work item.

2.4. Work Exit Point

This is where the Work leaves the system. There can be multiple Exit points for
different produced Work Items, i.e., scrap and finished products or happy and unhappy
customers. Do not get confused between storage areas and finished goods, no Work can be
performed once Item reaches the Work Exit point. These can be used to capture Results for
Work Items that cannot join the system if the queues are full.

2.5. Resources

These are only necessary when processes at Work stations compete for Resources,
such as when there is only one operator for several machines and can only operate one at a
time.

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2.6. Work Items
These objects are temporary entities within the system. They are processed by the system
and are automatically generated at Work entry points and destroyed once they have left the
system. It is better practice to have only one type of Work Item with multiple Labels if
multiple Work Items are required. [See Labels]

It is easy to change the appearance to any of
the graphics of any of these, refer to the
graphics section.

3. Controlling the machines
The machine Title is the title of the machine and if
there is any Visual Logic code we can refer to the
machine using this title. To get to the window,
double click on any of the machines or storage
areas.

3.1. Distribution
Controls how the machine operates and the
processing time. The operation parameters that the
distribution requires will show when the
distribution is chosen.

3.2. Required Resources
Are the requirements of personal to operate the
machine. [See Resources]

3.3. Efficiency
The percentage of the time the machine is able to
operate and can include more detailed breakdown
or maintenance schedules. [See efficiency]

3.4. Routing in
This is where the Work Items come into the machine. When you link other machines or
Work storage areas together, this automatically updates. You can collect a certain number
of Work Items from each storage area [see Routing in and out section]

3.5. Routing out
Is where the Work Items go after the Work is finished [see Routing in and out section]

3.6. Label actions
If a particular Work Item has an attached Label, we can dictate what are the processing
speeds are, where the unit goes after, before and during the processing. In addition, we can
set or adjust any of the Labels at any stage during the processing at a given machine. [See
Labels]

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3.7. Priority
If two or more Work Centers, which are ready to start Work, are competing for Resources,
the Work Center with the highest priority will receive the Resource first. Do not get this
confused with the Routing In and Out Priority Rules, these are different.

3.8. Contents
At the end of a run, or when the simulation is stopped during the course of a run, we can
see the contents of a Work Center or a storage area. This shows all the Work Items that are
currently in there and the Labels attached to the Work Items.

3.9. Graphics
You are able to change the appearance on the screen of the Work Center/storage/Exit/entry
by adjusting the graphics. [See graphics section]

4. Getting started
The menu-bar at the top of the screen will include all the pictures below. Run the mouse
pointer over the toolbar to find out what each button means or below is a simple
explanation.

The speed bar allows you to adjust the speed at which the simulation is running.

The Build Tools toolbar allows you to create simulation objects. Click each of them to be
able to place them on the SIMUL8 Screen. See section 2 for details on the different
objects.

The route drawing mode enables you to connect two icons. Click on one and drag to the
other you want to connect. The Show/Hide button toggles the display of route arrows.

The clock shows you how far through the simulation the time is. Double click or right
click the clock to get to the Properties of the timing.

The first icon (left to right) shows a graph of the processing content of the selected Work
Center or Storage Area over time. The second icon is linked to a spreadsheet where
SIMUL8 can read in or export out to, (Discussed later, [see inputting data parameters and
exporting data]). The third is a link to the Results page, and fourthly the dollar sign is a
link to the financia l data that can be collected.

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(L to R)
Click on the Reset tool to reset the clock to the beginning of the simulation.
Click on the Step tool allows you to advance the simulation time to the next event.
Click on the Run tool to run and observe the animated simulation

The basic toolbar includes the open icon to load existing simulations. The save icon, to
save the simulation, Print, Undo and Zoom.

5. Example 1
A Simple example – we will build on this example later on.

Step 1: add the Work entry point Double click the icon to be able to open the
Properties dialog. This will allow you to change the name and the arrival distribution.

Step 2: add two storage areas and link them from the Work entry point. To
link use the Route Drawing button, and drag the connection in the direction
that is required.

Step 3: add the Work Centers after the storage areas and name them in the
Properties menu by either double clicking on the Work Center or right clicking
or going to Properties.

Step 4: add the new storage area before the packing Work area, and the Work
area. Make sure these are connected, as shown and connect them to the Work
Exit Point.

Step 5: add a Resource, i.e. one operator to Work the two process machines. Add
the icon on the page. Note that the default value for the Resource is 10. Double
click to get the Properties and change the number available to 1, and rename as
Human Resource.

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Step 6: make the process machines require the Resource, by clicking the Resources tab on
the Properties window of the Work Centers. Click add, then select Human Resource.
Repeat this for the other process Work Center.

Step 7: to show the titles for each of the storage areas, get the Properties window >
graphics > title then tick the tick-box for showing the title.

Step 8: to have Work Items already in storage at the start of the simulation, start with 5
units in each of the storages before processing. Properties > Start-up> set to 5.

Step 9: set the processing speeds and distributions for each of the machines.

Work
Distribution Mean Standard Deviation
Center
Arrival Exponential 10 minutes N/A
Process 1 Uniform min = 5 and max = 6 N/A
Process 2 Normal 6 minutes 0.1 minutes
Packing Average 10 minutes N/A

The example is attached on CD as file example.S8

6. Efficiencies
Efficiency of a machine is the percentage of the
time the machine is able to operate. You are able
to adjust these parameters and the average repair
time, if known, to be able to adjust the operating
time when the machine breaks down.

If a more detailed efficiency or breakdown
schedule is required, toggle the “Detailed” radio button. This allows you to change the time
between the breakdowns and the time to fix the breakdowns. You are also able to specify
multiple different breakdowns by clicking on “more>>”.

7. Work Items
Individual Work Items
flow through the Work
Centers in a simulation.
Each of these may have
Labels attached. Accessed
from the main screen
under:
Objects> Work Item types.

You are able to add and remove the Labels attached to each of the Work Item types [see
Labels]. It is much easier to have one Work Item with multiple Labels than to have
multiple Work Items.

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Changing the graphics for each of the Work Items [See graphics]

8. Clock Properties
Accessed from the main screen menus Clock
> Clock Properties or double click the clock
on the main screen. This allows you to adjust
the units of ‘time- measurement’, and how
long to run the simulation. Note that the
default Time Unit is minutes, and hence
processing times etc should be specified in
minutes. Default settings start at 9 am and run
for 8 hours a day for 5 days. The Warm Up
and Collection Period is discussed below in
the next section.

9. Warm up period
The warm up period is the time that the
simulation will run before starting to collect
Results. This allows the queues and the
machines to hopefully achieve a steady state
(i.e., remove transient bias). If the simulation
is set up with appropriate initial values, such
as initial loadings and Work in progress, a
warm up period may not be required.

10. Results collection period
The Results collection period is how long the
simulation will run before automatically stopping
while collecting Results. The simulation will not
start to collect Results until the warm up period has
finished as discussed above ; the collection period
should be adjusted to suit the problem. Be careful
what units being used the simulation, i.e., if the time
units are minutes you should run for (60 minutes * 8
hours a day * 5 days a week) = 2400 minutes to
simulate the system running for a week.

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11. Graphics
Used for changing the
graphics or appearance of
the SIMUL8 icons.
Double click on them to
get the Properties window
> graphics. This opens the
window shown. By
changing the default
image, this changes the
graphic for the machine.
You are also able to make
the machine look different
for each of the possible states the machine is in, by changing the animated images further
down on the window.

After clicking on changing the image, it opens
the Image dialog box, which allows you to open
any of the images stored in SIMUL8 and
outside sources. To add from an outside source,
click on “Add from Library”, this will allow
you to insert graphics from any of the drives on
the computer.

12. Example 2
Including: efficiencies, clock, changing
graphics, Results warm up and collection
period.

Step 1: add an efficiency rating to one of the
machines. Process 1 machine. On the
Properties window for the machine, click
efficiency> then make it 95% efficient and
to repair to take 10 minutes.

Step 2: clock Properties. Clock > Clock
Properties or double click the clock on the main
screen. Make the starting time for each day be 7
am and the simulation to run for 5 hours a day.
For 5 days a week

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Step 3: changing the graphics for the
Resource. Resource Properties >
Graphics > select >
Then you are able to select a
different graphic or add one from
elsewhere in your files or from the
library. If you click on “Add from the
library” you can select a Worker man
or other graphics.

Step 4: Results warm up and collection period. Change the warm up period to 30 minutes,
so the Results are collected after this period. This should be sufficient time to allow the
state of the system to reach a steady state. Change the Results collection period to the rest
of the time in the week. (5 days * 5 hours a day * 60 minutes/hour – warm up time) =1470
minutes.


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13. Results
Once the simulation has been run, you are able to get
quick Results on the performance of a Work Center or
storage area, via Work Center Properties >Results

Export Results: This tells the
Results collection table to
record information about this
Work Center.

Many other Results can be collected from each of the simulations. Results can be added to
the Results Summary by right-clicking on the Results in the Objects Results Dialog Box.
The Results that have been set to Results Collection are found on the main screen: Results
> Results Summary, shown below.

Results > Results Comparison.

This returns all the information that has been collected for each of the last 200 runs. If the
information that you require is not here, you will have to click the export Results button for

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the desired machine or area, as discussed at the top of the Results section or
Results>Results Summary> Detail, then add the Results that you require.

14. Trials
A trial is a series of runs of the
simulation. They are all
performed with the same values
for parameters but using different
random number streams.

Trials > Random Sampling, tick
the ‘Auto-change box’. This puts
different random numbers in
each of the runs that you do.

15. Routing in and out
Refer to the Visual Logic [see section 21] that can be behind the Routing in and out.

15.1. Routing In
The Routing in and out tells SIMUL8 how Work Items should be brought into and sent out
from each of the Work Centers. Shown below is the Routing in for the process 1 Work
Center. By clicking in the window on name of the Item where the Work Item is coming
from, it will be circled on main the SIMUL8 window. There are many available Routing
rules, collect is discussed more later.

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The following Routing rules are the most common:

The priority Routing rule sends all Work Items to the first destination in the list, unless
this is blocked, in which case the second is tried and so forth.
Collect lets you collect a number of Work Items from a number of places, for example you
might want two shoes (one left and one right) to make a pair before boxing them.
Passive Routing means that the object does not attempt to pull (for passive Routing in) or
push (for passive Routing out). Work Centers normally attempt to pull Work in and push
Work out when it is complete. [SIMUL8 help]

For explanation of the others, use the SIMUL8 online Help [shortcut F1].

15.2. Routing out
Routing out indicates where to send the Work Items after the have finished at the Work
Center.
Circulate is default, the first Work Item will go to the first destination in the list, the
second Work Item to the second,...., the Nth Work Item to the Nth destination on the list.
Label Routing sends Items according to the value of a Label. Click the DETAIL button to
select which Label to use. Items with Label value 1 will route to the first in the list, those
with 2 to the second route etc. Note that Items with Label value 0 will cause the Work
Center to block.

For explanation of the others, use online help for SIMUL8, [shortcut F1]

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Batching is discussed below More>>, as discussed later,
explores the visual Logic
underlying the Work Centers.

16. Batching
Under Routing In and Out, we can decide to handle a
number of Work Items as a batch. You need to tell
SIMUL8 to group them together by collecting the
batch size for Routing into a Work Center [see
Collect]. Alternatively, by changing the batch size for
Routing out of a Work Center, you are able to change
the value of the size to leave a Work Center. The
Work Center routes out a batch of Items that are
replicas of the Item being processed.

17. Travel times
You are able to change the time that it takes to
travel between two Work Centers or storage areas.

You are able to set all the travel times to zero,
when they created. To do this,
Tools>Preferences>Distance, then set the travel
times to zero.

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18. Sub windows
Sub windows help to tidy up the screen and group many Work
Items together. Drag a box around the objects you would like in
the sub-window, right click the mouse button, and choose the
“Create Sub-Window” option. You are able to change the
Properties of the sub window. E.g., to change the Title and
graphics by right clicking on the closed sub window and going to
the graphics dialog.

To open the sub window double click on the icon, to close the
window click the X in the top right corner.

19. Labels
Labels are generally used for two purposes. Firstly to distinguish between different type of
Work Items, e.g. product types, and secondly to store attributes possessed by any Work
Item going through the simulation, e.g. a quantity or length. To create a new Label:
Object> Labels> New.
The value of a Label is set by a Work Center or Work Entry Point, by using the Label
Actions option. Add the Labels you wish to modify and choose the action you wish to
perform.

The order of initiation of the Visual Logic that can be behind the Label actions, are
displayed in the table in appendix A. It is important to note when label actions are initiated
if they are required before the processing at a particular Work Center. Multiple Work
Centers may be needed with zero processing times to change a Label before it is processed
i.e., dummy Work Centers.

After clicking Set to: click on value, to input what value you want to set the Label to. In
this example, all the Work Items that pass through this Work Center will have a Label of
distance attached to them, with a value of 500.

Work Centers that have the high volume box ticked can make use of the Quantity Label. If
you have a Quantity Label, this is a very powerful and reserved Label. Every Work Item

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type, which goes through a high volume Work Center, must have the Quantity Label
attached to it. The total processing time for the Work Item will be that specified in the in
the Work Center Properties multiplied by the value of the Quantity Label.

20. High Volume
The High Volume option provided by SIMUL8 allows near identical objects to be handled
as a batch rather than as a large number of indistinguishable Work Items. An example of
where this feature might be appropriate would be a mail bag containing 200 letters. In
some situations the processing time would be for the entire bag (e.g. transferring from the
post box to a van). Other times it is more appropriate to specify timing for each item (e.g.
sorting into destinations). In this case the Work Center High Volume option should be
chosen and the specified time will be multiplied by the Work Items Quantity label, a label
reserved specifically for this purpose.

When Batching-out from a Work Center, the value of the Quantity label is split over the
newly created Work Items. Using the example mentioned above, if the mail bag passed
through a Work Center with a batching out of 4, then 4 new Work Items would be created,
each with Quantity 50.

21. Resources
A Resource is an Item that is potentially
scarce. They are often used to model
staff that are required to run Work
Centers, either to set up a process, or to
reset a machine after processing a Work
Item.

To add a new Resource, click on the icon
in the toolbar, place it in the screen then
double click to get the Properties. This
dialog allows you to adjust the number
of Resources (usually people) available
and change the graphics.

To enable the Work Centers use the Resources, open the Resources option on the
Properties for the Work Center, and then ADD a Resource. This will show all the
Resources that are currently in the system; if the Resource is not there, you may have to
add it before continuing.

You are able to pool Resources together
as well as make the Resources dependent
on shift times, and how many Resources
per shift. Tick the check boxes on the
Resource form to pool or make the
Resources shift dependent.

You are able to change the details of the
Resources in terms of when you require
and release them. Different Work Centers

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are able to release Resources that have been required in previous ones. You are also able to
change the nature of how many Resources can be used by a Work Center, this may want to
be used to speed up a processing time if more than one Resources in available.

The order of initiation of the Visual Logic that can be behind Resource allocation, are
displayed in the table in appendix A.

22. Groups
A group is a collection of simulation objects, i.e., Work Centers or storage areas. A great
feature of these is being able to limit the number of Work Items which can be within the
group. To place Items in a group select them, right click and select either “Add to Group”
or “Create Group”.

Objects>groups

23. Change-Over times
SIMUL8 allows you to have a set up time
when a new Work Item is loaded. This is
good in a manufacturing situation when
Work Item type (change of Label)
changes and we have to have a setup time
before the next Item. Machine Properties
> Routing in > Change Over. By default,
there is no change over time between
Work Items.

24. Inputting data parameters
A very helpful tool within SIMUL8 is that it can read from and export to an Excel
spreadsheet.

19


Any spreadsheet has to be saved as a *.csv file, so save the Excel sheet and change the file
name from *.xls to *.csv. After saving the file, you have to create an object within
SIMUL8, i.e., pressing Ctrl+I to get the information store, and creating a new spreadsheet.
This one is called “orders”. Within the open simulation Logic and the reset logic, make
sure that you set :

Once the file is saved, then you can refer to the spreadsheets within SIMUL8 and as single
cells, i.e., orders[1,2]. The sheet above shows a form that is called “orders” for a particular
type of Work Item and having an attached Label for Quantity.

The window beside sets the Label Quantity value for each
of the Work Items to the second column of the above table.
Var1 is a counter that is updated with Visual Logic [refer to
visual Logic section] after every iteration of setting the
Work Items. Therefore, it sets the Quantity Label of the
first Work Item to 200, then 300 for the second Work Item,
and so on.

Another example of using the spreadsheets is shown on the
picture below; it refers to another spreadsheet that is called
parameters. The rate of processing is 1/800 metres per
second, and the cell parameters[3,4] have the number 800
in it. This is a very good consistency tool, so that if all the
Work Centers within the system change processing speeds,
we are able to alter the parameters just within the
spreadsheet.

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25. Exporting data/Results to Excel
Results>Results export

Exporting data allows you to send data from all of the runs or trails to Excel to facilitate
analysis. The data that is sent to the spreadsheet is whatever Results are currently being
collected. [See the Results section]. Make sure that you have the file name of a sheet that
you are using, with the correct sheer name [default sheet 1]. The Excel spreadsheet may
need to be open for the export to occur.

26. Visual Logic
Visual Logic is good for coding complex interactions that cannot be achieved using
standard drag-and-drop modelling. It is an alternative approach to controlling a model by
writing code as a programming language. The ‘SIMUL8 'wizard' helps users to write the
commands correctly by building code using drop down menus and lists. Once you become
more familiar, you may choose simply to write the code manually.

All the Visual Logic commands, with explanations, examples and where they can be
applied in a simulation, can be found in the Help menu under Visual Logic. Visual Logic
code is executed when triggered by an event, e.g. a Work Item being loaded into a Work
Center. It can receive and send signals to all the Work Centers and Resources in the
system. It can be good for updating counters at given times within the simulation and more
complicating Routing rules. All the decisions can use information about any of the
SIMUL8 Work Items, including counting the contents of a Work Center and current states.

The order of initiation of the Visual Logic is displayed in the table in appendix A.

27. Example of visual Logic
This example shows that if a storage area has
0 initial Work Items, then we set the initial
Work Items to the value of row 1, column 1 in
the parameters spreadsheet. If the storage area
does not have zero initial Work Items, then
we set all the Items within the storage area to
have a Label of Quantity = 1000.

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28. Example 3
This continuation of the last examples and includes steps for: Sub windows, scheduled
breakdowns, Labels.

Step 1. Create a sub window
Highlight the things that you want within the sub window, right click the mouse> create
sub window. [See section 17]. Create three sub windows on the example. One for each of
the Work Centers, with their own storage area within the sub window. The picture on the
main screen of the sub window will change. You are able to change the picture and make
sure the title is displayed under the properties of the sub window.

Step 2. Put a scheduled stoppage for maintenance on the packing machine. Click on detail
on open more of the Properties window.

Step 3. Add a Label
To create a new Label: Object> Labels> New. Then create a new Label called distance.
Then go into the Properties for the Work Arrivals > Label actions > Add, then add the

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‘new’ Label called distance. When back at the actions window, check the radio button for
set to: then change the value to a Normal distribution with mean of 50 and std dev of 10.

Adding the Label allows information about each of the Work items to be passed through
the system. If you stop the simulation and check the Work items that are within the queue
for packing at a given time, each of the Work items will have an attached distance with
them. The below figure is of the simulation finished, with two work items in the storage
area before the packing process, with their attached label.

The finished simulation is shown on the next page.

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This is a very brief introduction to the basics of SIMUL8. There are many extra
complicating features behind the world of simulation and this manual only scraps the
surface. One thing that has to be noted that all the actions within this document do not get
into depth with the Visual Logic, this is a very powerful feature and all of the commands
within SIMUL8 as a whole can be controlled within Visual Logic.

For more details and examples, refer to the Online Help within SIMUL8 and the following
section on the Case Study of General Cable.

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CASE STUDY
Simulation of the Flexibles Factory at General Cable New
Zealand Limited
Abstract of the Problem Situation

General Cable NZ Ltd has been investigating changing the layout, machinery and product
flow within their Flexibles Factory. However, they are unsure of the flow-on effects of
implementing these changes. The basis of this project was the construction of a detailed
simulation model using SIMUL8 modelling software, to assist the managers in their
evaluation of alternatives. We illustrate the simulation that was constructed to represent the
expected future state of the Factory and which will allow the managers to make decisions
that are more informed.

The follow examples are interesting techniques that the Authors found while doing the
Project for General Cable. This case was in terms of a manufacturing environment and
some terms and practices are specific to manufacturing but the ideas can be applied
elsewhere.

1. Sub windows
A good practice that we found that was that the simulation window does not itself have to
show all the detail in your simulation. With a complex simulation, you may want to
summarise your simulation at different levels and only display the upper levels of
information. You can achieve this by creating sub-windows.

We had many underlying Work Centres that together represent one actual machine.
Therefore, on the simulation window we used a Sub-window to show the machine that was
within the factory, while the actual Work Centers were contained within it.

2. Resources to stop machines
If the machine warrants only running for limited periods of time, then it was good practice
to control this by making the Work Centre require a resource. This allows you to control
the resource and turn these on and off when required. If the Work centre can only run when
it has the resource then it will not run. We controlled this using visual logic code, and

25


when the job orders ran out, we set the resource for the FWD machine to zero, as shown in
the screenshot above.

3. Using Labels
Labels are attributes possessed by any Work Item going through the simulation. For
example a certain Work Item can have a Quantity or product type associated with it. The
Labels that we required were;

Due date – defined in the month spreadsheet and sets the due date so each of the jobs
get prioritised on the coilers and the extruders.
Quantity – sets the value for the job on how many metres of the product type the job is.
This is a reserved Label, so using High Volume gives the total time for processing.
Product type – is what type of product the job is, so the specifics to the processing time
can be set.
Routed WD’s – this is used as a Label only for the setups. If the Work Center requires a
setup, then the route Label is one value and goes to the setup Work Center, else the route
Label is the default value and goes straight to processing.

4. Routes for setups
Some machinery required resources during setups but not for the remainder of the
processing time. Because of this the Work Items must follow a different path when the
Label product type changes. This is done using the changeover option in routing in. This
calls the distribution “ChangeOver” [see below VL code] when the Label changes, which
in turn changes the Label Route WDs from 1 to 2. Items are routed-out by Label which
causes the first item of each type to pass through the “setup FWD X” Work Center, while
all other items travel directly to the “FWD X” Work Center.

5. Groups

An important feature that SIMUL8 can make use of is grouping items together. This can be
a good idea if you need to limit the number of Work Items that can be simultaneously
processed by a set of Work Centers.

6. Dummy Work centres

26


Dummy Work centres that have a zero processing time can be very useful. When dealing
with Label actions and requiring these to be modified before being passed to W ork
Centers, then creating a Dummy Work Center can do this. There are some limitations to
SIMUL8, in dealing with certain instances, and sometimes many dummy Work Centers
with different routing rules can overcome some of these. For example, the below diagram,
shows many routes into the sort Work Center, that just sorts the Work items and routes
them out by a given Label.

27


References
Giffin, J. (2003). MSCI 311 Simulation Course Handout. Department of Management
:University of Canterbury,.
Haige, J.W. and Paige, K.N. (2001). Learning SIMUL8: The Complete Guide. Plain Vu:
Bellingham, WA.
Shalliker, J. and Ricketts C. (2002) An Introduction to SIMUL8, Release nine. School of
Mathematics and Statistics, University of Plymouth.
SIMUL8 Help (2003) Retrieved October 2004. Release 10.0 software
SIMUL8: Manual and User Guide. Visual Thinking International: Mississauga, Ontario
Canada.

___________________________________________________________

Authors

Daniel W. McGregor Matthew J. Cain

Department of Management, Department of Management,
University of Canterbury, University of Canterbury,
Private Bag 4800, Private Bag 4800,
Christchurch 8020, Christchurch 8020,
NEW ZEALAND NEW ZEALAND

Email: Email:
dmc89@student.canterbury.ac.nz mjc181@student.canterbury.ac.nz

28


Appendix A: Order of Operations.

This table shows the order of events that occur during processing at a Work Center
(from Haige and Paige, 2001). It is important to be aware of this sequence when relying
on changes to label values to control the model. Make sure that any necessary changes
are completed before the dependant decisions are made.

Direct Work Center
Sequence Distribution Pre-Sample Recommended Uses
Sections

Routing-in before(if Examine conditions in the model.
Work Center is idle, this Select and examine a specific
section will be called Work Item. Set Routing-in
after each event in the conditions s uch as batching-in or
1 simulation) collecting rules
Examine each of the Labels and
current model conditions to
determine processing time. Update
After loading Work
other model conditions when a
new Work Item is moved into the
2 Work Center.
Examine Labels and current model
Change Over conditions to determine processing
3 time
Examine Labels and current model
Process Time conditions to determine processing
4 time
Determine Routing-out discipline,
Work Complete set Labels and batch sizes. Update
5 result statistics

Batch Size Examine Labels and current model
6 conditions to determine batch size.
Set Label to a distribution Adjust parameters of the
vale ( repeated for each Item distribution based on conditions in
7 in batch) the model
Label Actions ( repeated
8 for each Item in batch) Set Label values
Before Exit ( repeated
after each event while Execute code to check for and/or
9 Work Center is blocked) handle downstream blockages
On Exit (after all Update inventory calculations. Set
Routing out decisions individual Label values across a
10 have been made) batch.

29


Department of Management
College of Business and Economics
University of Canterbury
Christchurch
New Zealand

http://www.canterbury.ac.nz

30

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