Master Schedule Grid (Format)

The master schedule format is a time phased grid format that is basically a spreadsheet where the rows represent supply & demand & the columns represent time periods/buckets from the present to the end of the planning horizon.
If the time bucket is one day, the system is called Bucketless.

It is important that the planning horizon be established beyond the cumulative lead time of the longest lead time component. The master production schedule is a rolling plan where new periods are added at the end of the planning horizon as the current periods become history.
The rows in the master schedule are as below :

Forecast: Forecast as calculated in demand management for all the periods

Customer Orders: the backlog of planned shipments for the product. This demand is certain & should always be used in preference to the sales forecast within the demand planning fence.

Projected Available Balance (PAB):

“An inventory balance projected into the future. It is the running sum of on-hand inventory minus requirements plus scheduled receipts and planned orders”. A –ve value here within the planning time fence should cause the master scheduler to take action by creating an MPS quantity.

In all supply environments the available inventory in future periods can be tracked as the projected available balance. The PAB considers the availability of good based on consuming the forecast with orders. In the distant future periods the PAB uses the greater of the forecast qty. or customer order quantities while in the near future customer orders are used as the statement of demand. The PAB is
calculated in the following way:

For the 1st period: PAB = Current on hand qty + MPS – Customer Orders

After the 1st period & prior to the demand time fence: PAB = Prior period PAB + MPS –Customer Orders

After the demand time fence:  PAB = Prior period PAB + MPS – (> forecast or customer orders, take the greater value of either the
forecast or the summed customer orders)

It is usually necessary to calculate a PAB beyond the planning time fence

Available to promise:

“The uncommitted portion of a company's inventory and planned production maintained in the master schedule to support customer-order promising. The ATP quantity is the uncommitted inventory balance in the first period and is normally calculated for each period in which an MPS receipt is scheduled. In the first period, ATP includes on-hand inventory less customer orders that are due and overdue. Three methods of calculation are used: discrete ATP, cumulative ATP with lookahead, and cumulative ATP without lookahead”.

It helps to project available inventory/capacity. ATP is a technique used with ATO & MTO operations to commit the uncommitted portion of a company’s inventory or planned production to customer orders. It ignores forecasts. ATP is maintained as a tool for customer order promising. It is uncommitted future inventory or capacity. It is calculated from the MPS & the summed customer orders until the next MPS qty is due. The ATP uses customer orders alone as the basis for it’s demand computation i.e. not forecasted values.

ATP = On hand balance + MPS –Sum of customer orders before the next MPS (1st period only).
For each other period ATP is calculated only in those periods where there is a MPS using the following formula:
ATP = MPS – Sum of customer orders before the next MPS.