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Emily K avatar image
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Emily K asked Carter Walch commented

Job scheduling using spt_Time error

Hi! I have made reference to the below question, and successfully build a model

  1. https://answers.flexsim.com/questions/45708/pull-strategy-and-shortest-processing-time.html
  2. https://answers.flexsim.com/questions/130092/i-would-like-to-know-how-to-adjust-this-model-of-m.html
  3. https://answers.flexsim.com/questions/65374/applying-dispatching-rules.html

But I realize the model time finished all jobs is weird. One of my operation's processing time is 1600s, but the model runtime end at 352s

I checked all the labels and processing time on processor, but still no idea..

Anyone figure out why?

SPT.fsm

FlexSim 18.1.2
sptjobshoptime error
spt.fsm (36.1 KiB)
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1 Answer

Carter Walch avatar image
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Carter Walch answered Carter Walch commented

Hi @Emily K ,

It looks like you are assigning labels correctly based on your J1_Time and J1_Machine tables. However, the processors are not using the process time (pt) label as the actual process time. For example, like you said, this item has a pt label of 1600 but the actual process time is found using the Type and Process labels, which leads to a different value.

1688570114553.png

1688570163304.png

Note: The label Type is 2 and label Process is 2 so when it pulls from the J1_Time table, the actual process time that is used is 80 seconds (row 2 and column 2)

1688570270138.pngTo fix this, you can use the pt label as your processing time by typing item.pt as the process time on each processor instead of the global table lookup. This is how they accomplished an SPT dispatching rule in this post you linked.

1688570395201.png

Let me know if that helps!


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Emily K avatar image Emily K commented ·
Thanks! I realised that I just need to change the trigger on processor, as when item enter the processor, the Process label will increase 1

This cause the processor read the following process's processing time

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Carter Walch avatar image Carter Walch Emily K commented ·

That's great! Then that will make your pt match with the Type and Process values on the table. Glad it worked out!

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