Hello,

Does anybody know if & how Navision calculates the total cumulative lead time for a manufactured item that has a multilevel BOM ? If yes does it store this information somewhere, is there any standard report showing this information or is it calculated "on the fly" during MPS / MRP Calculations ?

What I mean by total cumulative lead time is the longest lead time of the components that make the item plus the manufacturing time to produce the assembly for a standard batch size. And if we are talking about a product that has multiple BOM levels that would take into account also time needed to build the lower level assemblies.

To make it clear I will use the following example:

INPUT DATA

BOMs: I have product A that consists of raw materials A1, A2 and semi-finished item B. Semi-finished B item consists of raw materials B1 & B2.

Purchase Lead Times: A1 = 1w, A2 = 2w, B1 = 1w, B2 = 2w.

Production Standard Times: To assemble product A it takes 2hr/pcs. To assemble semi-finished B it takes 1hr/pcs. (Is production lead time calculated by the item routing or Navision simply uses the "Lead Time Calculation" value it will find in the item master file if item is defined as replenished by "Prod. Order" ?)

Production Standard Batch Sizes: Product A = 20pcs, Semi-Finished B = 40pcs

EXPECTED CALCULATIONS

Cumulative Lead Time Semi-Finished Item B: Longest lead time of BOM components = max (B1 LT = 1w, B2 LT = 2w) = 2w. Time to produce standard batch size of 40pcs = 40pcs * 1 hr/pcs = 40hrs = 1w. So Cumulative Lead Time Semi-Finished B = 2w (to buy the raw material) + 1w (to assemble the product) = 3w.

Cumulative Lead Time Product A: Longest lead time of BOM components = max (A1 LT = 1w, A2 LT = 2w, B LT = 3w) = 3w. Time to produce standard batch size of 20pcs = 20pcs * 2 hr/pcs = 40hrs = 1w. So Cumulative Lead Time for Product A = 3w (to buy raw material A1 & A2 and produce semi-finished B) + 1w (to assemble the product) = 4w.

So does anyone know if & how Navision calculates above information which is a mandatory input for MRP algorithm ? Is this information stored in any Navision table or is it just calculated "on the fly" during MRP run and not stored anywhere ? Is there maybe a standard NAV report showing this information ?

The cumulative lead time of a product is a very important piece of information not only for MRP calculations but also for business reasons such as, for example, to calculate how much time you need to build a product if you start from scratch (without 0 stock for example). That would be your longest lead time to deliver this product as long as the lead time information you have in the system is correct and every component is delivered of course on schedule.

Hope somebody will have the patience to read this question and provide an answer !

Cheers

Dimitris