Difference Between Reorder Pt and Safety Stk

Hi All, I have been trying to find the difference between the reorder point and the Safety stock fields in the item card. I have set a requisition Method code of Make-to-stock, Calc. below Reorder Point, Fixed reorder policy, calc. with Inventory. When I have a reorder point of 250 for a certain item. and I have 100 in stock. I understand that when I run the calculate plan in the requisition worksheet the system must suggest to me for a Qty of 150. But when I do so system suggest to me to buy 250 instead. After some investigation when I key in the value of 250 in the safety stock field then the requisition change to 150. I want to know if this is how the calculation should be. Thanx, Best regards, Prashanth NCFC, NCMC, NCSD prashycool@yahoo.com

Hi Prashanth According to my notes and manual the Safety Stock Quantity is not included in any caluclations (I am presuming this is in Attain). However your findings suggest this to be untrue. I will try and test this from another perspective later today. In other systems I have been involved with the safety stock has been an additioanlly calculated field in an MRP regen, ticked or not ticked by the user. In these instances You could, for instance flag safety stock at 100, this is to cope, in tandem with the reorder level, great fluctuations in demand. The reorder level could then be set at 250. During the MRP regen you could choose to include or exclude the safety stock. If you included it the starting point of inventory would be current stock minus safety stock. So if you had none in stock and none on orders anywhere, then if you included the safety stock the system would tell you to order 350, if you did not it would be 250. Anyway reorder levels and safety stocks are open to great interpretation depending on which school of manufacturing you come from. If it was me I would always try and seperate the two, never using them in tandem, it just makes explanation and finding the requirements easier. Anyway I will set this up later and let you know how I get on. Regards Steve

Hi Prashanth You are absolutely correct in your sceanrio, I am running GB version 3.10A and get the same results. In answer to your other question, No, it is not calculating correctly. I have reported this back through channels at this end and I will let you know of any response. Worrying though! Steve

Hi all, when stock is below the reorder point, the system suggest an order with quantity = reorder point and planned forward. when stock is below safety stock, the suggest order quantity is Safety Stock - Stock and the order is planned backward.

Hi Elena Okay, the system DOES it ths way for reorder point, but that does not necessarily make it correct. The reorder point is a trigger, surely reorder quantity should be used to get back to the required stocking level, not the reorder point itself? As for stock below safety stock, it cannot simply be safety stock - stock. In Prashanth’s example safety stock was 150 with stock of 100 on reorder point of 250. This was giving a requirement of 150. Whereas in your example the requirement would have been 50, so I suppose it then generates another requirement to get it back up to the reorder point of 100 for the requirement? Why on the second one does it not follow the rules of the first example and use the reorder point again and suggest a planned order for 350? Whichever way the system is working, I would argue agains the methodology of the first one, and wish they had told us that safety stock is now included in calculations. I only went on the Attain course a few months ago and they said it was not! Thanks for the input though Steve

Thanks Steve, I agree with your argument, the concept of safety stock is that this stock cannot be consumed and you would enter a value in this field only if you want to maintain a minimum level in your inventory. As per my understanding, the safety stock should not be used in the calculation unless the current inventory of the item goes below safety stock. let me know your view. Best regards, Prashanth NCFC, NCMC, NCSD prashycool@yahoo.com

IF you have: Reorder point = 250 Safety Stock = 150 Project Stock = 100 date 31/07/02 the system suggest you two order: 1) Safety Stock - Stock. Backward scheduled. Qty 50 End Date 31/07/02 2) Reorder Point - Safety Stock. Forward scheduled. Qty 100 Start Date 31/07/02 But this was in NM 2.60. You are right Attain does not consider Safety Stock. It use it only to calculate the planned order when you use Reorder Point and the Safety Stock is below the Stock (e.g. RP 250, SS 50, Stock 70 => Qty ordered is 200). Morevore if your current stock is already below the reorder point, the projected stock (considering suggestions from planning) will be twice the reorder point. Whereas if the current stock is not below the reorder point, you could have a projected stock below the reorder point. i.e.: A) current stock = 35 reorder point = 30 sales order = 10 delivery 13/07/01 sales order = 40 delivery 20/07/01 => suggestion is 30 due date 19/07/01 projected stock = 15 B) add a sales order qty 20 delivery 15/08/01 => suggestion is two order: a) qty 65 due date 19/07/01 b) qty 30 due date 20/08/01 projected stock is 60 C) change reorder point to 40 remove sales order created in B => suggestion is two orders: a) qty 40 due date 26/07/01 b) qty 55 due date 19/07/01 projected stock is 80.

Hi Elena I am running GB 3.10A, and I get slightly different results than yourself, I have detailed them below; Step A Current Stock = 35 Reorder Point = 30 Sales Order = 10 off 13/07/02 Sales Order = 40 off 20/07/02 Suggestion is one order a) 30 due on 14/07/02 Projected is stock is 15 I still feel this is incorrect. If I have a reorder point of 30 then I should be getting another replenishment order considering projected stock is below the reorder point. Step B Add a sales order for 20 off 15/08/02 Suggestion is three orders a) 30 due on 14/07/02 b) 30 due on 16/08/02 c) 35 due on 15/08/02 Projected stock is 60, which is the same end result as yourself, although got to differently. The order b being generated as the projected stock hits the reorder point of 30, and as no other parameters exist it has chosen the reorder point as the reorder quantity. Step C Change the reorder point to 40 and remove the sales order created in Step B Suggestion is one order a) 40 due on 02/06/02 Generated as at my order date on the regen my stock is below the reorder point. Once again it has used the reorder point as the reorder quantity, rather than generating a replenishment to fulfil future orders and the reorder point current stock difference. The projected stock is 20, again below my reorder point. I presume you are running 2.60 as you are getting different results. I will try and run the same figures through this later today to see what happens. Cheers Steve

Hi Steven, I’m running IT 3.10.A but I used 1M as reorder cycle (I didn’t realize that), after removing it, the result of scenario B is the same you got. But i still have two order in case C. I agree with you the results are not correct. About the fact that reorder point is used also as reorder quantity … it’s an old story, in version NM 2.01 reorder quantity was calculated as you described “…rather than generating a replenishment to fulfil future orders and the reorder point current stock difference”. They changed it in 2.60 and this caused big discussion. Anyway, there’s a whitepaper explaning how mrp works (at least in NM 2.60).

Okay Elena Seems like its a discussion that will go on! Its been good discussing this, I hope our paths cross again. It will also be interesting to hear what Navision UK have to say on functionality working in teh manner it was designed to, although they are clearly struggling as I am still awaiting an initial response! I will look into the white paper, thanks again. Take care Steve

Hi Elena I have fianlly got my hands on the white paper, I had it previously, only could no longer find it. To quote “The reorder point is normally forecasted consumption during the replenishment lead time plus the safety stock. When the projected available balance falls below the reorder point, the MRP makes a suggestion for a replenishment order” Under the Fixed Reorder Qty it tells me that a fixed reorder qty is processed when the projected available balance falls below the reorder point. The planned order receipt will either be the quantity in the Reorder Quantity field on the item card or the net requirements (whichever is greater). Therefore I could only recommend that the reorder cycle chosen for the reordering policies on a reorder point item would be better served by “order” or “lot-for-lot”. So I suppose to correct myself from earlier when I felt it was not calculating it correctly, it is when you follow the white paper through. Two interesting facts to finish with: 1. Navision UK believe it to be a problem and are processing it internally. 2. The White Paper has been completely re-written for 3.60 (joy!) Cheers Steve

Can anyone tell me where I can get a copy of the 3.60 Planning white paper? Thanks!

Hi Liz I have a copy of the calculating MRP white paper, written in 1999, which I believe is still the applicable white paper [:D]. If you email me through the forum or post your email address in the forum I will send it to you. Alternatively you should be able to get all white papers from your NTR.

Hi Liz, I’ve a 3.10 version, written in 2002.

Hi Elena I was told by my NTR (10/07/02) that a new white paper was being re-written for version 3.60, but no release date was given, until then I had to use the older and not precise version written for 2.60 (I think [:D]). I cannot check on my NTR website currently as the partner network is down! It was written in March 1999 and I have been told has been used on all subsequent releases of the software. Page One has a table of contents and teh following script:


Calculating MRP White Paper for Navision Manufacturing The manufacturing environment is often characterized by a diversity of approaches. This includes the calculation of MRP. Therefore, this whitepaper is provided to explain MRP in relation to Navision Manufacturing. It defines the procedure for calculating MRP with Navision Manufacturing and also describes MRP in terms of the broader manufacturing environment. This information is relevant to the MIDWAY release. Information about MRP might change slightly for future product releases.

If you have a different one I would appreciate a copy sent to sweaver@xonitek.co.uk Whilst I am awaiting for the 3.60 to be published [:D]

Hi Elena, Could you email me a copy for Version 3.10? ssissenwein@polestarlabs.com Thank you :slight_smile:

I have the 3.10 one too… was hoping the 3.60 version had been published… Thanks!

Hi I have loaded a service request on Navision requestng the 3.60 white paper or an expected publish date. I will let you know what happens.

yes please!! Would love a copy… alison.porter@proaccess.co.uk Ta Steven

Hi Ally You must be having a slow day - I loaded the reply on this string and then felt it would not be obvious so deleted it and opened a new topic - which makes your posting look really strange! Email on its way!