Delay function, Time step

[neelu@nitw.ac.in]

Dear Tom,

Request you go through the model.
in this model, the time step is 0.25 days
cycle time varies between 0.25 days to 0.75 days
I used the fixed delay function in production rate variable to create a delay for the processing time of the cycle time.
the FGI (Finished goods inventory) is a stock variable because it is an inventory.

in these models I have some questions, please explain to me
1) If cycle time ( delay time) is 0.3404 days then the production rate should happen after that cycle time but in the model, it has shown at 0.25. so please explain
2) if the production is done then immediately it has to come to finished goods inventory (FGI) but it appears in next time step. if I want that what can I do.
3) the production rate at 0.25 is 96 but in FGI at 0.5 it is shown as 24 and again production rate at 0.5 is 104 but FGI at 0.75 is 44 units. so please explain it.

[Administrator]

If the cycle time is 0.3404, then your time step is too large. I always choose time step to be 1/4 of the smallest delay in the model.

I'd also suggest adding units to your model. There are already errors in it that a units check would reveal.

[tomfid]

Regarding 3), I think there are several things going on.

First, a delay of .34 is not a multiple of the time step, so it has to be rounded off to .5. Presumably that's why production doesn't appear until time 0.5.

Second, adding units to the model would help illuminate the quantity in FGI. Production at time 0 is 96 units/day for 0.25 day. So the increase in FGI is not 96 units; it's 96 units/day *.25 days = 24 units.