Dashboard WorkInProgress and TimeInSystem

[laurenz_peleman]

Goodmorning everyone

I tried to use the WorkInProgress and TimeInSystem dashboards for the first time, and found out they behaved a bit different than expected. I thought these TrackedVariables were updated automatically, any time a flowitem was created or destroyed.

Hence, I expected that, when plotting the WIP as a 'content' value against time, it would be incremented on creating and decremented on destoying an item. However, WIP only goes up (correctly, as items are created), but apparently no correction is made when flowitems are destroyed. Besides, the value of the TrackedVariable TIS is fixed at 0 during the whole simulation, while I expected it to show the total staytime of all actually present flowitems in the system, which should definitely be a positive value.

Since it is my first attempt to use these statistics, do I overlook some (manual) action I have to do to make these TrackedVariables work?

Thanks in advance, kind regards

Laurenz Peleman

[matt_long]

Can you share a model that displays this behavior? I can only guess that you're creating flowitems through something other than a Source, Create Object activity in Process Flow or a Create Flowitems pick option. All of these call the applicationcommand("trackdefaultsoncreate", newitem); that cause these tracked variables to autmoatically be recorded.

[laurenz_peleman · Accepted solution]

I will post it in a private question then.

[philboboADSK]

@Mischa Spelt

This looks like it might be a bug with the FloWorks::ItemToFlow object not correctly handling WIP and TimeInSystem when it destroys objects.

Laurenz,

This model is a FloWorks model. You should contact Talumis for technical support. Talumis can't see private questions on Answers; only FlexSim USA employees can.

[laurenz_peleman]

Hi @phil.bobo, thanks for the reply. However, even if issues originate from the ItemToFlow objects (I presume that could cause the WIP not to decrement as expected), why is the TIS of the flowitems in the queue not properly monitored? Is this caused by the downstream objects as well?

[philboboADSK]

TIS is recorded when an item is destroyed. An item's TIS is the time it was destroyed minus the time it was created.

[laurenz_peleman]

Okay, so if I understand it right, TIS does not monitor the total staytime of the items that are in the model at that particular moment, but the total value for all items that are already finished in the past? If so, I will have to look for another variable to show me what I want.

[philboboADSK]

Time in System doesn't monitor total staytime at all.

It monitors the individual time in system for each object that has been destroyed:

You would need to sum that up to get total time in system, or average it to get average time in system.

And yes, that tracked variable only accounts for items that have left the system. It has no information about items still in the system.

[laurenz_peleman]

Okay, thanks for the clarification! Think this problem is easily solved by updating the TrackedVariables explicitly