SAP MRP - Step 8 - Scheduling of the Procurement Proposals in a SAP MRP run
SAP MRP - Step 8 - Scheduling of the Procurement Proposals in a SAP MRP run
The next task in the SAP MRP algorithm is to schedule the procurement proposals created in the previous steps. You can expected to know how SAP MRP schedules the procurement proposals so as to correctly evaluate them once they are created. There is no manual task involved in this step.
To expect the MRP run to schedule the procurement proposals correctly, we have to maintain the following in the master datas properly:
a) In-house production times (for in house manufacturing, maintained in the material master MRP 2 view as lot independent and as lot dependent in the work scheduling view),
b) Planned delivery times (for external procurement, maintained in the material master),
c) Schedule margin keys for float times (optional for In house Production, maintained in the material master),
d) Interoperation times (optional for in house production, maintained in the material master or Task lists such as routing or recipes),
e) Planned goods receipt times (optional for external and internal procurement)
f) Set up times and tear down times (optional for in house production, maintained in the material master Work Scheduling view or in the task list such as routing or recipes)
For the externally procured materials, SAP uses the planned delivery time (lead times) and goods receipt times in Material master to schedule the delivery & release dates for the procurement proposals. You can either use forward scheduling or backward scheduling for these materials. SAP uses the basic date scheduling in the case of externally procured materials.
For materials which are to be manufactured in house, as assemblies and sub-assemblies (in-house produced materials), the scheduling is done according to the scheduling method selected in the selection screen of the MRP run.
If “Basic Date scheduling” is selected then the system considers the “in-house production time” of the material in the MRP 2 view along with its goods receipt time. Please note that the times in terms of days’ as included in the material master are not quantity dependant and MRP uses them directly for scheduling regardless of whether it is planning for 1 unit or for a million units. The Planning does not generate any capacity loading and operation dates are not derived. The system generates the basic start date of the order and the basic finish date of the planned order. This type of scheduling is best used when the lot sizes of the production and their timings are usually fixed.
It is also said that the system carries out Basic Date scheduling using quantity dependent timings as included in the Work Scheduling views of the material master. Though I am really doubtful whether the MRP run can really do this. You can really try this and include the set up time (this is not quantity dependent), the processing machine time and the interoperation time for a given base quantity. It is expected that the system calculates the total lead time for a planned quantity.
Alternately if the scheduling method selected is - “Lead time Scheduling” the scheduling for the planned orders are done through the use of standard timings in the routings/recipes of the material. The Standard values or the standard timings in the routings or recipes are for a base quantity, which means that the scheduling carried out using the lead time method is an accurate method of scheduling and gives the greatest results every time. It not only calculates the operation lead time (operations start and finish times) but also cumulates them to arrive at a total lead time with an order start date and order finish date.
When you use the “lead time scheduling” method, the system uses the scheduling methods configured; you can use either forward scheduling or backward scheduling method for the MRP run. As a default scheduling type, the system uses backward scheduling but it also switches automatically to forward scheduling if the determined start date lies in the past. Though if you do not want the system to switch to forward scheduling automatically, you can specify per plant in Customizing for MRP, in the IMG activity Parameters for determining the basic dates that the system is to continue the backward scheduling calculation even if the resulting start date lies in the past.
Check the Lead time Scheduling example as shown below. Lead time scheduling uses the floats in the schedule margin keys (if any) and the standard values in the operation along with the operation’s interoperation times.
Order Lead time scheduling for In-house produced materials =
Opening Period from where the Planning opens as mentioned in Schedule Margin Key
+
[Order Start date] – ‘Order Floats before Production’ starts here – Floats mentioned in Schedule Margin Key. If floats = 0 then Operation start date = order start date
+
Operation 0010 Start date – to – Operation 0010 Finish date (calculated through the standard values in operations)
+
Operation 0020 Start date – to – Operation 0020 Finish Date (calculated through the standard values in operations)
+
Operation 0030 Start date – to – Operation 0030 Finish Date (calculated through the standard values in operations)
+
[Order Finish date] – ‘Order Floats after Production’ ends here – Floats mentioned in Schedule Margin Key. If floats = 0 then Operation Finish date = order start date
The selection of the Routing/Recipe is made through the “task list determination strategies included in the configuration” or if the selection method for the BOM selection is through ‘production versions’ then the task list included in the version is used.
At the end of this step, SAP has a procurement proposal which has the estimated quantities, dates. Though what is not known yet, is, whether the procurement proposal is for external procurement or for internal production. The Procurement type for a material in MRP views would decide that for the MRP program as explained below.
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