MRP and Dampeners - Help Please!

I am doing an implementation of navision 3.70 in a brewery and using MRP to generate the orders from a production forecast. The scenario is this: Run MRP and view suggested orders Modify orders in planning worksheet slightly (including small quantity changes and splitting orders) Create Firm Planned orders Change planned times and machine centres until we are happy with the plan for the first week. As the plan is now firm, the next MRP run I wish to do is for the following week. However MRP suggests changing my existing orders back to its original suggestions. Perhaps if I could make the dampeners work “both ways” i.e. allow smaller quantities and later dates as well as larger and earlier I could get MRP to accept my plan for the first week without suggesting any changes (unless a substantial forecast change takes place for the week concerned). If I set the “Planning Flexibility” option to “None” on the orders I get a reasonably good result UNTIL I change the planned times for the orders. I then do NOT understand the result - MRP seems to not only suggest orders for items which are already covered but also suggests additional orders for the same item! Cany anyone help as I am at my wits end!!

Hi Chris I will reply as standard out of the box MRP works in Navision. Firstly you can stop Navision suggesting re-planning messages if the demand moves out, but you cannot is the demand moves in as this has an adverse affect – namely you need the goods quicker. The Change Quantities can be dampened, but only as a percentage of the lot size. This is the lot size on the replenishment tab of the item card. If you set this up you could restrict the messages, for example if the lot size was 10 and the dampner percentage at 9999 then any quantity change of less than 100 would be ignored. This however is ONLY when demand is reduced. If demand is increased it will tell you to change the quantity. You could alter this in the reorder policies of the item card, but it will depend upon what you do. For example the reorder cycle - what is it set to? The planning flexibility if not set set to none fixes the order and will not allow it to move, so if you alter the dates of the sales orders it will plan for the replenishment again, but leave the original orders as you have told the system to “fix” these. I am guessing your prefered setting here would be unlimited! What you really need to do is list all the relevant item settings, describe the changes you make and then the planning messages you get. But this is only if demand is reduced or planning is pushed out, if it is the opposite the system will give you replanning messages. Of course you might be able to further handle these with good reorder cycle and order multiple settings to reduce the replanning messages further. If you need to break the standard Navision processing and cannot configure the items to meet your needs you will need to modify the system (whilst not uncommon with Navision MRP many are developed unnecessarily due to a lack of understanding.).

Thanks for the reply Steven, I already fully understand what you have said and I believe that the ONLY way out is to enable the dampeners to work “both ways”. The alternative would seem to be to set flags which exclude both the forecast and the resulting orders for the firm planned week to be ignored by MRP. The only problem there is that I DO want significant changes in the forecast to be reflected in suggested changes to Prod orders. I am using my own graphical planner (VB and C++) to re-plan the jobs in the brewery as I can set the algorithms as required - this is very successful. Now that there is a Navision planner in version 4.0 this problem is going to become more prevalent as MRP will be used as the “initial starting point” for planning and the planner used to fine tune it. The net change reporting from MRP will then give the same sort of problems as I am trying to resolve.

Hi Chris The navision limitations on dampners are for good reasons, if you need to ship it sooner than planned it affects the customer so you get a replanning message, if you need more, again a replan as you do not have enough. To break these rules you will need to make modifications to the system, but be aware you will naturally not be told you need to make goods earlier than suggest or more than you plan to, so you will ship late and not enough! Have fun! [:D]

Hi again Steven, The problem for me (and I suspect a lot of other people in the future) is that there is now a tendency to use MRP for “Macro planning” and some form of planner/finite scheduler to “micro plan” within an acceptable delivery “bucket” for the customer. If the customer is told delivery will be w/e 27/4/05 we may choose to plan the job early or late in the week using a planning tool - this may be “too late” for Navisions needlessly detailed planning calculation. Hence “two way” dampeners set to, say 3 days each way would work well. In the brewery we only work within full weeks as the final operation (kegging or casking) only takes one day but brewing takes 7 days. My problem is further compounded by the quantities on Production Orders in the brewery - MRP calculates detailed order sizes based on BOM values but when we actually create the orders the head brewer sets them to “nominals” - for which there are no “cast iron” rules. These may be slightly more, or less than calculated by MRP - gain hence the need for a two way dampener on quantity. Another complication is that, as brewing is an organic process, you will NEVER actually get the ordered quantity - you may get more or less. We have overcome this by dynamically changing the order quantities and Order BOM quantities “pro-rata” to the quantity of “principal ingredient” resulting from the previous orders - this again upsets the net change reporting of MRP

Horses for Courses as they say. Navision will probably never go in anyweher perfectly without changes, this is one you’ll have to make for this customer and industry.