Question

Scheduling - shop order gap

  • 7 July 2021
  • 6 replies
  • 254 views
J
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Hi 

i am using Apps 10 and have put a 1 day shop order gap on an inventory part so MRP would schedule only 1 shop order requisition each day. (below)

As you can see from the image below it is still scheduling 4 different shop orders to start on the same day at the same time which is not possible for us to achieve.

 

 

When I go into the actual shop order i can see the Earliest start date on all for shop orders have a 1 day gap between them but all have the same finish date. We use backwards scheduling so I don't think MRP looks at the earliest start date?

 

Why is there not a shop order start date gap of 1 day between the shop order ? and how do i achieve what i am trying to implement?

regards

Jamie 

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6 replies

S
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What are the scheduling capacity settings for your workcenters for this item?  It seems you have them set to infinite capacity, which will allow MRP to schedule each shop order individually irrespective of the other orders for the same item.  You will probably need to change the work center to finite capacity and set the exact amount of work the work center(s) can complete if you don’t want parallel scheduled shop orders for the same item and the same work center.

J
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Hi Shawn

the schedule capacity on the work centre is set to finite capacity and there are only 2 resources with the correct labour class on the routing so the maximum capacity should only be 16 hours per day.

regards

Jamie 

S
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OK, that was the first and easy thing to check, so that looks right.

Order gap time says it will only shift the start date (not the finish date) of the additional shop orders, and only then if they are created as multiple proposals due to exceeding the lot size of the part.

It sort of looks like the shop orders/proposals are appearing on sequential days, but all have the same need date, so forcing the finish date back to the same one for all of them.

It may be that something more sophisticated like Constraint Based Scheduling to manage this, but I’m afraid that is beyond my experience to answer directly.

matt.watters
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Work Center Capacity has no effect on this.

Experiment with a setup like this:

Manufactured component part with an Order Gap Time of 1. On its parent part’s BOM, this part has a QPA = 1.

This part also has Min/Max/Multiple lot size parameters all set to 1, so for any demand I will get multiple shop order reqs each for a lot size of (1). Set these values to how many you can make per order/per day.

I have a shop order for the parent part, lot size = 10.

Run MRP and the resulting due dates of the requisitions for the component are:

Had the Min/Max/Multiple been (2), I would have (5) shop reqs each with a proposed start date gapped by one day.

Regards - Matt
M
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Hi!

I am a bit summer-lazy so I have not read all the details. Just wanted to highlight that MRP only considers gap time if MRP planned supply on a specific day is greater than max lot size. 

So let say have a net requirement of 1000 4th July and max lot size is 100 and gap time is 1. Then you will see the effect. You will have 10 orders. And required date of the 1st order will be the 4th July, the 2nd order will be the 3rd July and so on. Well system considers manufacturing calendar days only.

-Mats

matt.watters
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I had a reply on here, edited it and now it’s gone, but it follows the logic explained above by @majose.

I have this manufactured component part, order gap time =1. In its parent part’s BOM it has a QPA = 1.

Also on this part, I have the Min/Max/Multiple Lot Size all set to 1.

I have a shop order for the parent part, lot size = 10.

When MRP is run, the resulting requisitions for the component are each for lot size = 1 and all with due dates one day apart from each other.

 

Regards - Matt
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