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  #1  
Old 05-16-2008
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Default Operator dependent process times

First a short background...
I'm working as an industrial engineer for a job-shop type manufacturing plant. I myself have limited (mostly Arena) simulation/modelling experience and basic C++ knowledge, but it's been a few years since I've needed to use either.

Our process times depend on elbow grease--that is, how much each particular operator has (depends on skill level), and how many operators are working on the process at any given time (depends on plant-wide flow/demand). After playing around with the Flexsim demo, I have a couple questions related to how I could apply it to manual operations.

1. Is there a way in Flexsim to model process time as being dependant not only on a particular operator, but also on the number of (particular) operators who happen to be working? All of our process times are in man-hours.

2. Can the operators be assigned to processes based on both their particular skill set and system flow (max queue, for example)?

I appreciate any response.
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  #2  
Old 05-18-2008
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Goksin Yilmaz Goksin Yilmaz is offline
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Default The answer to both questions is affirmative.

Yes, Flexsim can handle both scenarios in quite a flexible manner. I have used an Excel-based "Skills Matrix" with Flexsim and (although I have not had the need to do that yet,) the other scenarios are not difficult to simulate with Flexsim either.

The only caveat is that you may need to go a bit beyond the standard drop-down options available in objects to model these scenarios. However it is not that complicated and if you developed logic with any simulation tool, you should not have much of a trouble with these scenarios.

In my experience C++ knowledge is not really required, but familiarity with any programming language and coding certainly help.

I hope this helps and good luck...
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Shawn Henkel (05-22-2008)
  #3  
Old 05-22-2008
Shawn Henkel Shawn Henkel is offline
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Default I appreciate the response...

...and maybe your response will be the same, but to clarify the question/answer, I'm like to delve a little bit into this.

An example of a piece of what I would like to model: a single operator is welding a large machine, a task which takes 30 man-hours to complete. At any point during the welding process, based on the state of the model (a large queue behind the welding process, operators with nothing else to do, etc.) and different operator skill sets, other operators may or may not join the original welder until completion of the process.

So my questions are:
1. Can operators be modelled to, basically, keep busy, as long as there is work to be done?
2. Can processes be modelled to accept more operators than are required?
3. Can process times be altered during the process, triggered by additional (or subtracted) operators?
4. Can this be done continuously, or instead only by breaking things down?

Thanks again.
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  #4  
Old 05-22-2008
Alex Christensen Alex Christensen is offline
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The way the processor in the library works is when a flowitem enters, it calculates the process time and makes an event for the flowitem to leave that far into the future. It would be tricky (VERY tricky) to make an operator come help work at a processor and make the process end earlier. But there is still hope! Everything is possible with Flexsim, it just might be hard to do it with your first approach.

In the library, there is an object called the BasicFR that has picklist options to make it behave like a processor, except the picklist options make it easier to edit. It is possible to write logic that would behave as you described, Shawn.

Last edited by Jeff Nordgren; 05-22-2008 at 05:09 PM.
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  #5  
Old 05-22-2008
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Default BasicFR or a simpler approach

Hello,
Shawn: I guess your question is an interesting case to model in any simulation environment. As Alex suggested, Flexsim is quite flexible and BasicFR may be a solution. I am not familiar with BasicFR, so by using the standard processor in Flexsim, I can suggest the following approach:
  • Create a label (let’s call it “process_time”) on the flowitem representing the work piece welding will be done on and assign the total process time on that flowitem when it enters the model,
  • Flowitem enters the welding processor,
  • Capture available operators and flag them (through a label) as assigned to this piece of work (so that they will not be captured by any other jobs). Obviously you will need to use “requestoperators” command. There is a sample in the “Pick Operator” pick list.
  • Process the item for a minute (or two or more, according to your system dynamics).
  • Depending on the number of operators who worked on the job, reduce the “process_time”. Temporarily free operators.
  • If “process_time” is greater than zero, send the flowitem back to the processor,
  • If new operators are available, capture (and flag) them. Make sure the latest process time to be performed in the processor will not exceed remaining “process_time”.
This also gives you the capability to re-dispatch some operators who might be needed to work on a higher priority flowitem that entered another processor.

By the way, I guess this is the method I would use in a couple of other simulation applications I am familiar with.

I hope this helps… GY
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  #6  
Old 05-23-2008
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Tom David Tom David is offline
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There is a model called Sample_IdleOperatorHelpsOtherOperatorWithProcess_T D in the Download Section under User Concept Models (click here). Even if the model is not v4.32 yet, it shows one solution how to reduce process time if another operator helps with the process. This is a tricky problem in general for discrete-event simulators. I work with different once in the past and in my eyes Flexsim has best and most flexible concept (delayedmessages, tasksequences) to solve this problem.

In my eyes the described model from Shawn can be build in Flexsim using different dispatcher for the different teams of operators (skill) and delayedmessages and tasksequences to have fully control on the operators and the process times. But it is not a point and click model and needs some coding and a good concept to start with.

The above model I build, because I had something similar and first tried to figure out how I would solve it in general. So the above model is my general idea how to solve it.

Anyway, I hope the model will give some hints and help, even if it is not really easy to understand how it is done, but I hope the Description and the Comments will help.

Good success!
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Last edited by Cliff King; 05-24-2008 at 11:04 AM.
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  #7  
Old 05-23-2008
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Jeff Nordgren Jeff Nordgren is offline
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Shawn, I guess what everyone is saying here is that what you are asking is possible. Just may not be for the beginner at the first. As you can see, there actually may be more than one way to solve the problem, depending on your needs. I hope you can see that with the input of some of our users that you can see that this problem and pretty much any problem can be solved using Flexsim. Does this answer your question?
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  #8  
Old 05-23-2008
Shawn Henkel Shawn Henkel is offline
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Default Thank you all

And to answer your question, Jeff, yes, I think my questions have been answered. I understood the concept that, with code, pretty much anything was possible. But at first (and second) glance, it seemed to me that the structure of the program interface might be too rigid to allow access to all of the possibilities. Thanks to everyone who replied, I'm starting to see the flexibility of the program. And maybe even picking up and idea or two on simulation in general.

Thanks again.

And on a side, note, it's surprising to see a community this involved with a simulation program. Keep up the good work.
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