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  #1  
Old 03-11-2013
Stefan Jerenz Stefan Jerenz is offline
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Default Start Processing again after Breakdown

Hi Community,

I want to model a normal production plant which includes machine breakdowns.
My problem here is the handling of items which are being just processed when a breakdown happens. Flexsim only offers the standard option that the flowitem will be processed further after the repair of the machine. But I want to model that the processing of the flowitem has to start from the beginning after the repair.

One solution (a little bit long-winded) would be to manipulate the processor:
With the repair:
  • Close the output of the involved processor
  • put STATE_PROCCESING
  • Sending a delayed message to the involved processor - time delay correspond with original processing time of the flowitem
With OnMessage:
  • put STATE_IDLE
  • Open the output
With this solution the result and also the states for analysis would be OK.

But now I am searching for a more easy solution by manipulating the eventlist.
My question here is if there is any possibilty to put a new processing time by changing the Process Finish time of the involved processor?
What commands I have to use?
Which problems may occur?

Or are there any other easy solution for my problem?

Thanks for your Help
Stefan
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  #2  
Old 03-11-2013
Jason Lightfoot Jason Lightfoot is offline
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Default

If you're only processing one item at a time you could see if this does what you needs. The failure code modifies some variables of the processor and item.

Update: Use Kris' response below

Last edited by Jason Lightfoot; 03-11-2013 at 08:53 AM.
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  #3  
Old 03-11-2013
Stefan Jerenz Stefan Jerenz is offline
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Default

Thanks Jason,

this is what I am searching for, but the processing times are not OK.
I expand the model with a Global Table for analysing the processing times of all flowitems and I modified the MTBF/MTTR so that the breakdowns happen every x00-x10 seconds.

In the GlobalTable you see that when a breakdown happen the processing time for the currently flowitem increase to exactly 30 seconds instead of something between 20 seconds and 30 seconds.
  • processing time before the breakdown + MTTR + full processing time after repair
  • [0,10] sec + 10 sec + 10 sec
  • [20,30] sec

I only recognize new things in the DownFunction of the MTBFMTTR, is this correct or did you do sth else?
Can you explain the commands you use?


Thanks
Stefan
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File Type: fsm RestartProcessAfterStop_withAnalysis.fsm (42.6 KB, 71 views)
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  #4  
Old 03-11-2013
Kris Geisberger Kris Geisberger is offline
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Default

Looks like you only need the following in the Down Function after stopobject:

HTML Code:
if (content(downobject)==1)
	setvarnum(downobject,"timeoflaststop", getentrytime(first(downobject)));
The state profile seems to be correct after all is done.
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File Type: fsm RestartProcessAfterStop_KG.fsm (48.3 KB, 82 views)
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  #5  
Old 03-11-2013
Stefan Jerenz Stefan Jerenz is offline
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Default

Thanks Kris for this addition - this is what I was looking for.

Can you explain the the command
"setvarnum(downobject,"timeoflaststop", getentrytime(first(downobject)));" do or better what the Variable "timeoflaststop" means?


Stefan
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Old 03-11-2013
Kris Geisberger Kris Geisberger is offline
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It depends on the object, but in general it is set to the current time when stopobject() is called, and then used to determine how to resume the events of an object when resumeobject() is called. If there were multiple concurrent stops, then it would be set on the first stop, and used on the last resume.

I set timeoflaststop (after the stopobject) to the item's entry time so that when the object resumes it will think that it was down since the start of the process. Fortunately, the state profile is not managed using this variable, so it shows the truth.

All said, I'd wait for a thumbs up from Phil or Anthony... we might be missing something yet. It would be nice to have a pick option for this situation though. Also, the case where the item is scrap because of the failure and we want to abort the remainder of the process and send the item to another port.
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  #7  
Old 03-11-2013
Stefan Jerenz Stefan Jerenz is offline
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Default

Thanks Kris, now I understand (a little bit more)

The options you mentioned would be very useful for building production plant models because in reality you always have one the three possibilites after a breakdown:
  • processing can go on
  • processing has to start from the beginning
  • processing is not possible any more (item is waste)
So it would be very helpful to have these options available as a MTBF-MTTR-Parameter or so.


Stefan
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