Static Lot Sizing Procedures

The static lot sizing procedures are namely – the ‘exact lot sizing’, fixed lot sizing and ‘replenish to maximum stock level’.

When the lot size is “EX” or exact lot size, the system creates planned orders or procurement proposals to cover the exact shortage requirement. The lot size is the whole shortage quantity required to satisfy the demand. That is, if the requirement is for a quantity of 112 units, the proposal will be created for an exact 112 units.    

On the other hand if the lot sizing procedure is “fixed lot size”, then the total requirement quantity as proposed by the system, to cover the shortages is divided in to the number of fixed quantities as included in the material master (MRP 1 view), for example, if the lot size is fixed as 100 Units and the shortage quantity is 500, then the system will create 5 planned orders to cover the shortages. 

Similarly if the lot size of the material is “replenish to maximum stock level” (Lot Size – “HB” for example oil tankers or barges) then on shortages of the requirement quantities the system creates planned orders to fill it to the maximum stock level. 

Periodic Lot Sizing Procedures

Periodic lot sizing procedures are namely - the ‘daily lot sizing’, ‘monthly lot sizing’ and ‘weekly lot sizing’ (in fact you can decide the period of the lot size in lot sizing customizing). The requirements that lie in a given period are clubbed together and the availability date for the procurement proposals would be the start date of the first requirement in the period. The standard configuration of lot sizes puts the requirements for periodic lot sizing at the start of the first requirement in the period, but you can have it set to the end of the period also. 

Availability Date = Start of the period or

Availability Date = End of the period 

And if the lot sizing procedure is “weekly”, SAP MRP will consider all the demands for the week and all the receipts for the week and place a weekly proposal (planned order or purchase requisition). The weekly proposal can be put at the start of the week or at the end of the week as the configuration in the lot sizing procedure. 

You can use the below listed tools along the lot sizing procedures selected in the MRP 1 view of the material master. It should also be noted that not all the tools can be used along with all the lot sizing procedures. 

Minimum lot size

When the minimum lot size is 80 and the required quantity is 100, the system creates a requirement proposal for a quantity of 100 Units, to cover the shortages. 

This can be used with almost all the lot sizing procedures. 

Maximum lot size

If the required quantity through a demand is 120 kg, then the system will create two planned orders of 80 kg & 40 kg {if the Plant/Storage location stock for that material is Zero} 

If the procurement qty is 140 kg, and the Maximum lot is 80 kg and minimum is 15 kg, then the system will create 2 planned orders of 80 kg & 60 kg. {If the Plant/Storage location stock for that material is Zero} 

If the procurement qty is 85 kg, and the Maximum lot is 80 kg and minimum is 15 kg, then the system will create 2 planned orders of 80 kg & 15 kg {if the Plant/Storage location stock for that material is Zero}.   

This can be used with almost all the lot sizing procedures. 

Fixed Lot Size

In this procedure, the lot sizes are fixed and the procurement proposals are created for the given fixed quantity. 

If the required Quantity through demand/demands is 120 and the fixed lot size is 80, then the system will create 2 planned orders with one planned order of quantity 80 an the other planned order of Qty 80 {if the Plant/Storage location stock for that material is Zero}. 

Rounding Values

If the Rounding Value is 20 units, the procurement quantity is 70 units, and the minimum lot size is 15 units, then the system will always round up the planned order to a multiple of 20 units, specifying the rounding to a quantity of 20 Units.

You would have already noticed that the minimum lot size, in the above example, really did not play any role, but if the procurement quantity, for example, would have been 13 units, then the system would have created one planned order of 20 units, which covers both the minimum lot size and the rounding requirements. 

One more example would be, if we don’t consider the Min/Max Lot size and the procurement quantity is 70, then the system would just create one planned order of 80 to round off to 20 {if the Plant/Storage location stock for that material is Zero}. 

Again the rounding value tool in the MRP 1 view can be used with almost all the lot sizing procedures. 

Maximum stock level

Maximum Stock level is a Quantity of the material in this plant that may not be exceeded. In materials planning, the maximum stock level is used only if you have chosen Replenish to maximum stock level as the lot-sizing procedure; that is, you have entered HB as the lot size key. Enter a value if you have chosen Replenish to maximum stock level as the lot-sizing procedure.

If you have chosen to work on Maximum stock level then the system procures for the maximum stock level quantity and then adds the Procurement quantity to that.

Examples:

a) If the Maximum Stock level is 500 and the demanded quantity is 45, then the system creates a planned order of 545, thereby first ensuring the 500 stock is filled up and then the demand quantity is added to that.