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Microsoft Dynamics NAV (Archived)

NAV 2013 MRP problems

Posted on by Microsoft Employee

Hello,

We are in the process of implementing a new NAV 2013 system, moving on from a different ERP system.

One area that we can't get working reliably is MRP.

The results we are obtaining from the production planning worksheet (regenerative plan) are unusable. We don't use forecasts - our inventory control is based on setting reorder points against relevant items. We set the 'Minimum Order Quantity' field using our economical batch quantity for each item. Our items generally have BOM & Routing, and may have multiple levels.

Scenario 1 - 'Lot-for-Lot' reorder policy

If we set all items to 'Lot-for-Lot' reordering policy, & set our reorder point using the 'Safety Stock Quantity' field (as the 'Reorder Point' field is not used with this method), then the planning worksheet produces a reliable suggested order list in terms of order quantities, but because most order suggestions are triggered by inventory falling below the safety stock level*, the suggestions are mostly flagged as an 'Exception', and the due date is set to today, regardless of whether we have raw material or sub-components in stock. Order suggestions for raw material and sub-assembly components are then scheduled backwards, so e.g. NAV tells us that we should have purchased a component 6 weeks ago.

We have been unable to change this behaviour, so the dates being suggested by NAV are useless - we need to know when we can actually make the items, planning forwards, not looking backwards!

* e.g. An item has safety stock = 100, inventory = 110, and we ship a sales order for 20. We still have 90 in stock, which is sufficient until we can make some more in 6 weeks time, but NAV flags an 'exception' in the planning worksheet and sets the due date to today.

Scenario 2 - 'Fixed Reorder Qty.' reorder policy

If we set all items to 'Fixed Reorder Qty. reorder policy, NAV requires entry of a 'Reorder Quantity' against each item - we cannot leave it as zero.

We can set the 'Reorder Point' field with this policy, so 'Safety Stock' is set to zero. The results of the planning worksheet's date suggestions are generally OK (unless an item falls below the safety stock qty., even though it is set to zero), and the quantity calculations for genuine demand are also generally OK. However, instead of maintaining stock at our reorder point, NAV wants to keep stock above our reorder point (even if reorder point = 0); so NAV suggests that we order every item on our system. Even if the reorder point is set to zero, and there are no commitments for an item, NAV suggests that we order 1, because we have set the 'Reorder Quantity' field to 1 (because NAV won't allow us to leave it set to zero!).

We therefore end up with a ridiculously long list of nonsense suggestions to order items that we don't actually need.

 

Has anyone else experienced similar problems using either of 'Lot-for-Lot' or 'Fixed Reorder Qty.' reorder policies?

Are there any solutions available? I don't mind if we have a solution based on 'Lot-for'Lot' or 'Fixed Reorder Qty.' as long as it works.

Any help would be gratefully received!

Thank you.

Mark Woodward

*This post is locked for comments

  • Assent Profile Picture
    Assent 10 on at
    RE: NAV 2013 MRP problems

    Hello Mark,

    Please let me know if you are still experiencing issues with MRP. We may have a solution that might help. We developed the solution for Nav 5.0, and we are now developing for BC .

    schalunkal@assentresources.com

    SC

  • Verified answer
    Community Member Profile Picture
    Community Member Microsoft Employee on at
    RE: NAV 2013 MRP problems

    Hello,

    I thought that I would update this as we have finally started to make use of NAV's MRP planning worksheet, after much testing and long trials.

    We did follow Olof's suggestion in the end (thank you Olof), i.e. to set all items not requiring minimum stock to have 'lot-for-lot' reorder policy, with safety stock = 0. Any items that we have a minimum stock level for were set to 'fixed reorder qty.' reorder policy, with reorder point set as required. We found that for items where we only need to keep 1 in stock, setting the reorder point to 0.5 did the trick.

    We also found that some other item fields were key to getting good results, e.g.

    time bucket = 6M (for fixed reorder qty. items)

    dampener qty = 0.75 x reorder qty (for fixed reorder qty. items)

    lot accumulation period = 2W (for lot-for-lot items)

    rescheduling period = 6M (for lot-for-lot items)

    We also altered planning flexibility to be automatically set to 'None' for all production and purchase orders, to prevent the planning worksheet from constantly suggesting changes to existing orders.

    In addition to this, we had some customisation work carried out to enable us to run 'capable to promise' against the planning worksheet results - this gives us more realistic dates than the planning window (at least they achieve start dates in the future rather than the past).

    Overall I remain disappointed that Microsoft's solution isn't more effective at calculating dates, but with our settings and workarounds, we at least have a workable solution now. 

    I hope that the above information is of use to some.

  • Community Member Profile Picture
    Community Member Microsoft Employee on at
    RE: NAV 2013 MRP problems

    Hi Mark,

      We're facing exactly the same situation you have encountered.

    Have you found any solution/ workaround or any third party software to solve it?

    Talks a lot for your help

    Ciao

    Davide

  • Community Member Profile Picture
    Community Member Microsoft Employee on at
    RE: NAV 2013 MRP problems

    Hi Jerry,

    no i didn't get/have a solution for this Issue.  I'm not happy about it.

    You can only change the Reorder Policy on the Item from "Fixed Reorder Qty." to "Lot-For-Lot".

  • Jerry Goforth Profile Picture
    Jerry Goforth 5 on at
    RE: NAV 2013 MRP problems

    Mark,

    Did you ever get a reply/solution to this?  From my experience, this is a very common occurrence in the Planning Worksheet and poses a big problem. It would be amazing if someone could actually responded to your questions without referring to another blog, all of which I have read and none of them offer an answer.

  • Community Member Profile Picture
    Community Member Microsoft Employee on at
    RE: NAV 2013 MRP problems

    Hello Olof,

    Thank you for your explanation & consideration..

    I will aim to conduct some testing using your suggestion this week & will report the results here.

    Regards,

    Mark Woodward

  • Verified answer
    Community Member Profile Picture
    Community Member Microsoft Employee on at
    RE: NAV 2013 MRP problems

    Hi Mark,

    My suggestion is to use lot-for-lot for those SKUs that you want to have a reorder point = 0 (because you are saying that you don't want inventory and only replenish when there is a demand, which to me is lot-for-lot).

    For the SKUs where you want a reorder point, my suggestion is to use the fixed reorder qty. and set the reorder point (since this schedules forward like you expect).

  • Community Member Profile Picture
    Community Member Microsoft Employee on at
    RE: NAV 2013 MRP problems

    Hello Olof,

    Thanks for your reply, but I don't really understand what it is you suggest we try instead.

    NAV will not allow us to set reorder point = 0, hence the problem with fixed reorder qty. method.

    NAV doesn't use reorder point with lot-for-lot method, only the safety stock qty. - when demand is triggered based on the safety stock qty. NAV always treats it as an "emergency" order and does not plan forward.

    Please advise if I have misunderstood your suggested answer?

    Regards,

    Mark Woodward

  • Community Member Profile Picture
    Community Member Microsoft Employee on at
    RE: NAV 2013 MRP problems

    Hi Mark,

    I my mind lot-for-lot is used when you want to produce based on your demand and not have inventory (other than the safety stock). And fixed reorder qty. is used if you want to carry inventory of the item and replenish based on a reorder point.

    So, using fixed reorder qty. and set the reorder point to 0 and only get suggestion to replenish when there is a demand sound to me like it should be a lot-for-lot.

    And your scenario 1 sounds to me like it should be fixed reorder qty, instead of lot-for-lot, since you want to carry inventory and replenish when you fall below a certain point.

    NAV calculates forward if you reach the reorder point.

  • Community Member Profile Picture
    Community Member Microsoft Employee on at
    RE: NAV 2013 MRP problems

    Hallo  Aleksandar,

    thank you for this link. I will read it. But i think you don' understand our problem. Look at secanrio 2.  If the Reorder Policy = Fixed Reorder, the reorder point is set to zero and the Inventory of this Item is zero, but no any demand exist, NAV will suggest an Purchase. Thats not the real world. The inventory value from our customer will explode.

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