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modelling an (R,ss,S) inventory system
Posted: Thursday 10 March, 2011 - 15:29
by WU1
(See attachment for English problem statement)
Ik heb een vraag omtrent het modelleren van onderstaand voorraadsysteem met periodieke replenishment:
Er is een centraal voorraadpunt en een decentraal voorraadpunt. Producten worden van centraal naar decentraal gebracht volgens een (R,ss,S) regel: d.w.z als aan het eind van iedere R perioden (zeg iedere dag) als de voorraad x kleiner is dan ss dan wordt een order ter omvang S-x geplaatst bij het centrale magazijn. Een dag (of een aantal uur) later worden de bestelde producten afgeleverd bij het magazijn.
Het zou toch relatief eenvoudig moeten zijn dit met 4Dscript te modelleren maar ik kom er niet uit. In de bijlage mijn gedachten en idee.
Re: modelling an (R,ss,S) inventory system
Posted: Tuesday 15 March, 2011 - 15:07
by JeroenSteenbakkers
I propose the following 4dscript. To keep overview I will use ome local variables
Everytime the review is performed the following code should return the number of product you want to order
valCurAdminstock is the value for current administrative stock
CODE:
Code: Select all
do(
var([valResult], vbvalue),
var([valS], vbvalue),
var([valss], vbvalue)
var([valCurAdminStock], vbvalue),
if(
valCurAdminStock < valss,
valResult := valS - valCuradminstock,
valResult := 0
),
valResult
)
Re: modelling an (R,ss,S) inventory system
Posted: Wednesday 16 March, 2011 - 15:01
by WU1
Thanks Jeroen,
I might have formulated my question not precise enough. I was wondering what atoms to use and where to enter the 4Dscript.
By now, I do have a simple model that works with an arrival list to generate orders and an assembler to deal with the order picking and final demand is modelled by a server. This works fine but I wonder what approach you would suggest: e.g. using lock and unlock atoms and conditional control atom?
The problem with using the assembler is that when one ingredient is not available that the processing of other request is blocked by the one currently in the assembly atom. (I will post this subproblem also as a separate topic.)
Thanks and regards
Rene
Re: modelling an (R,ss,S) inventory system
Posted: Wednesday 16 March, 2011 - 15:28
by JeroenSteenbakkers
Rene,
when i modelled such a system i also used the assembler to attach an "demand" to a product. In this case the demand was created by the source (because of negexp behaviour). the assembler took the products from a "local shop" queue, on the exit trigger of this queue was the replenishment strategy, based on this strategy i opened and closed the output of the "supplier" queue. IN between the local shop queue and the supplier queue i placed a multiserver to simulate the leadtime of the replenishment.
However this was a s,Q system with continuues review. To simulatie a review period i would release a atom every review period immediately to a sink, and the place the strategy code in the "on entry" of the sink.
greets, jeroen