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Abdelrahman Mahmoud S avatar image
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Abdelrahman Mahmoud S asked Joerg Vogel answered

How to start a process on a multiprocessor before the previous one finishes?

I am modeling a job shop car maintenance facility, and 1 worker can start letting oil drain, then leave it drain, while its draining, he starts on another process. I am not able to do that on a multiprocessor, which i find to be the most suitable processor for this scenario. Note that I am currently a student and am not really experienced in flexsim.

Thank you in advance.

FlexSim 20.0.0
job shopin parallelmultiprocesser
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Joerg Vogel answered

@Abdelrahman Mahmoud S

If you don’t want to build a special logic, I think you can use a totally different approach with a combiner, a separator, processors and a sink.
A worker has to perform several independent tasks on a car, so the car is a container of tasks. My approach puts the tasks to do like a recipe into the car as items. I use a combiner for this to pack items into the car. There is trigger option OnEntry to exchange the recipe by a global table lookup in the combiner. The car enters the job shop. A separator is the entrance of a working cell where a worker do the tasks. The separator closes its input OnEntry trigger of a car. The process time of the separator is the time for administration, parking and so on. The actual working time of the worker begins with the transport of the unpacked items to processors in the working cell. For example oil draining - opening the oil outlet plug and draining the oil out of the car consists of:

  1. going to the car,
  2. transport the box to a processor,
  3. setup the processor with an operator,
  4. process the item without an operator,
  5. transfer the box to the sink with an operator or without. You can use the load time to put the plug into place again.

Transport the next unpacked item is another job task.

[At point 3 - you can replace setting up the processor by the unload time.]

The sink counts entering items. If the number of unpacked items matches a label value, the sink opens the input of the separator and resets its statistics. The label value is set through the content of the car when the car enters the separator.
If you want to keep the worker in the cell, give him a long lasting task to do with a low priority at a station, where another item (not unpacked item) is processed. Each other task in the cell calls the worker by preempting a tasksequence and a different higher priority. The priorities defines the order of the tasks the worker has to do in sequence. You can set the priority by labels on the items and evaluate the label values when the worker receives the tasksequences or creates the tasksequences.

The car leaves the separator and the job is done. Another car can enter the working cell.
[If you want to control more workers simultaneously in more cells you can tag the workers. There are options in the picklists to keep operators tagged.]

If I must build such a scenario, I would begin with a working cell consisting of a separator, a single processor and the sink. If the mechanism works well, I would add a second processor and test the model. Each progression step should be small. The model must always run as desired.

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Joerg Vogel answered Benjamin W2 commented

The concept of this object is different. A classic processor can do a single activity, then the item has to leave the object. A multiprocessor can do several different tasks on an item in a row before the item must leave. It is a matter of the statistic in combination with entering and exiting of items that counts. What you want is an own logic in a processor. You need not a classic processor nor a multiprocessor, you need a Fixed Resource Process Flow processor with operator object.

If you have inserted the process flow sheet, you'll find a new class of objects in the 3D Modell Library "Process Flow".

Now you can build a logic upon your needs in process flow beginning and enhancing the process flow templates.


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Benjamin W2 avatar image Benjamin W2 commented ·

Hi @Abdelrahman Mahmoud S,

Did Joerg's answer help you out? If so, please click the Accept button. If not, how else can we help?

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