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11 Production Tools / Optimization User’s Manual Line Computer UNIX 11.4 Optimization Dial og Software Version 402.xx Edition 06/96 11 - 26 - DETERMINA TION OF RUN TIME: Optimizat ion r un time increa ses exponential ly …
User’s Manual Line Computer UNIX 11 Production Tools / Optimization
Software Version 402.xx Edition 06/96 11.4 Optimization Dialog
11 - 25
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SETUP CHANGEOVER TIMES
Set-Up Optimization requires a basis for the calculation of the changeover times. The parameters listed in
the following can be set to specify how much time is required for setup changeover operations.
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Basic time for set-up changeover [sec]:
The basic time refers to the time that elapses between the
last placement from the predecessor setup and the first placement of the follow-up setup. The actual
setup changeover times are not included in the calculation. The default setting is 600 sec.
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Trolley changeover time [sec]:
Estimated time required for the removal and installation of a compo-
nent changeover table. While the placement process continues, the feeders are prepared, away from
the line, on a second changeover table. The changeover table is then exchanged completely during the
changeover procedure. The default setting is 180 sec (= 90 sec for taking down + 90 sec for setting up).
To be able to use this parameter, a feeder part must be defined as component changeover table in the
Configuration Editor (see chap.12).
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Feeder changeover time [sec]:
Estimated time required for the removal and installation of a feeder
on a fixed component table. The feeders are prepared outside the line with the placement process
continuing. They must be changed over individually; this is why the time required for the setup
changeover increases with the number of machine components to be changed over. The default set-
ting is 60 sec (= 30 sec for taking down + 30 sec for setting up).
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COMPONENT TYPE
Components with a dominant proportion in the assembly and a dominant vibration time are set up re-
peatedly by Set-Up Optimization so as to avoid load imbalances. This has an effect on the setup and thus
the changeover times. If a component type is not to be set up an unlimited number of times, the number of
feeders per component type can be restricted.
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Fixed set-up components to be set up only once
This parameter is only relevant where a fixed setup is defined. It is possible to define whether or not a
component already contained in the fixed setup is allowed to be set up by Optimization at another or
several other locations that may be more advantageous.
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Maximum number if dominant
This parameter allows you to define the maximum number of times a dominant component type may
be set up. If only a minimum of setups is to be created, the number of feeders in the case of domi-
nance should be limited to 1. With the setting of 0, Set-Up Optimization can decide on its own how
often the component type at issue is to be set up.
11 Production Tools / Optimization User’s Manual Line Computer UNIX
11.4 Optimization Dialog Software Version 402.xx Edition 06/96
11 - 26
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DETERMINATION OF RUN TIME:
Optimization run time increases exponentially with the number of jobs. The quality of the setup can be set
via the run time: long run time -> good setup, short run time -> poor setup. The run time of Optimization
can be limited. Once the preset run time is exceeded, or the preset number of iteration steps completed,
Optimization is aborted. The best solution hitherto found continues to be used.
Optimization can produce reproducible (parameter: no. of iteration steps) and non-reproducible results
(parameter: program run time per lot).
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Program run time per lot [sec]
This parameter allows you to define how long Optimization is to run for a given job. By multiplication
with the number of jobs contained in a lot file it is possible to determine the total run time of Optimiza-
tion for that lot file. The optimization results are not reproducible.
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No. of iteration steps
This parameter allows you to define how many Optimization runs (iteration steps) are to be performed
until a setup is established. Thereafter, Optimization is aborted and the best setup selected. The opti-
mization results are reproducible, however the time required for optimization cannot be precisely pre-
determined.
Meaning of the buttons
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Reset
This button is used to reset the standard values to the default values. They are deleted when so doing.
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OK
This button is used to accept the modified values.
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Cancel
This button is used to discard the modified values and to restore the previous state.
11.4.3.2 Examples of Parameter Settings
The parameter settings for Set-Up Optimization greatly depend on the frequency of setup changeover
operations taking place during a production run.
Three examples have been selected to show how the parameters can be set in different production situations:
●
highly flexible production:
many different jobs are processed in a very short time with the setup
changeover operations required.
●
flexible production:
frequent setup changeover operations are carried out whereby identical jobs are
also processed over and over.
●
inflexible production:
only one single setup is used for production over a long period of time.
User’s Manual Line Computer UNIX 11 Production Tools / Optimization
Software Version 402.xx Edition 06/96 11.4 Optimization Dialog
11 - 27
Example 1: Highly flexible production
Setup problem:
In the case of a highly flexible production, setup changeover operations are performed daily in order to
produce new products. Setup changeover is carried out job-specifically.
Objective:
A setup is to be calculated for a given job as fast as possible. As little time as possible is to be expended
on the setup changeover. Production time plays is of minor importance.
Parameter settings:
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Clustering according to the Sequence method.
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Maximum number (feeders) if dominant: 1.
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No. of iteration steps: 1
(With a setting of 0 one single setup is created. It is, however, not optimized. This is the fastest
method for obtaining a setup.).
Lot file setting:
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Set the lot size to 1 so that only the setup changeover time is of importance.
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Enter an initial setup, i.e. the current setup of the line.
Effect:
From the initial setup a follow-up setup is computed in the shortest possible amount of time, having the
following features:
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A minimum changeover time from the initial setup to the follow-up setup is achieved.
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Every component is set up only once. The dominance of components is suppressed.
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Feeders with two compartments that are taken over from the initial setup and integrated into the
follow-up setup remain set up on the exactly same tracks as before.
●
Components from the initial setup that are not required will be discarded.
Example 2: Flexible production
Setup problem:
In the case of flexible production, frequent setup changeover operations are performed with identical jobs
also being produced over and over again. Planning is medium-term.
Objective:
Grouping of products into setup families with the focus on short production times. Setup changeover
operations should be limited to changeover tables as far as possible.