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Jeff Whittle

Flow that randomly stops

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I want to model a flow mechanism which usually runs at a certain rate but randomly fails and stops for a time before restarting (e.g. a rock crusher in mining).

I currently model the "crusher" with a FlowNode and can start and stop it via buttons.

I expected to use a monitor on Run.TimeNow with varying intervals to toggle the crusher on/off, but Run.TimeNow is not accepted as a monitor state variable.

How should this be handled? (I'm a simulation and Simio newbie.)

 

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You should use the timer element. Definitions-->Elements-->Timer. To see how it works quickly you should look for "timer" in sample simbit solutions or for a satisfactory explanation use help.  

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Thanks gocken.

By setting up two timers and alternating between them I've managed to stop and start, but with fixed time intervals, whereas the intervals need to be partially random.

I attach my attempt.

I would appreciate any ideas.

Eventually I hope to have a number of such entities, each with different timing, in a processing chain.

Development 02.spfx

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Hi Jeff,

You can use a Resource object to model the unplanned failures and repairs of a crusher or conveyor.  The Resource object has unplanned failures built in, and furthermore, can accommodate a shift pattern.

When the resource fails, close the flow node and when it is repaired, open the flownode again.

I have modified your model to illustrate this concept.

There was custom Flow Library shared in the past that contains a "flow server".  Basically an object such as a server, but that can handle flow.  

 

Development 03.spfx

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Hi Jeff, 

your model is ok. You can assign random variable's to timer element as well. By this way you can get random intervals. In order to work properly you only need to set timer2's reset event name property to timer2.event which in fact you have made this assignment at timer1 element. I attached your model with modifications. It seems it works as you intended. Hope this helps? 

Development 02.spfx

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Hi Jeff,

I present another, and I think, a more compact approach in the attached model. In this model, I subclassed flownode object. And define a timer element in it. I also defined two properties in this subclassed object as Time_to_repair, time_to_failure. By this way you can use these properties to assign failure times and repair times after failure seperately. hope this helps!

all the best,

gocken

Development 02_subclassed.spfx

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