Approaches to Master Scheduling
There are several possible approaches to creating and managing master production schedules, each allowing a different amount of control by the system:
• Fully automatic
• Fully manual
• Computer-assisted
Fully Automatic Scheduling
The master schedule can be generated entirely by MRP. This means that the system has complete control over master scheduled items, with no distinction between master scheduled and MRP items.
Note: When this approach is used, material plans may change dramatically each time MRP is run. For example, a master schedule order may be expedited one day and canceled the next.
To use the fully automatic approach to master scheduling items, set the following values for each master scheduled item in Item Master Maintenance (1.4.1) or Item Planning Maintenance (1.4.7).
Master Schedule
Yes.
Plan Orders
Yes.
Order Policy
Any option other than blank.
Fully Manual Scheduling
The master schedule can be created and maintained entirely by a master scheduler, who enters firm planned orders using Master Schedule Order Maintenance (22.13) or Work Order Maintenance (16.1). MRP can be set up to generate action messages to assist the master scheduler in creating orders for master scheduled items.
To have MRP review master scheduled items and produce action messages, but not plan orders, for those items, set the following values for each master scheduled item in Item Master Maintenance (1.4.1) or Item Planning Maintenance (1.4.7).
Master Schedule
Yes.
Plan Orders
No.
Order Policy
Any option other than blank.
Note: If an item’s Order Policy is blank, MRP does not generate action messages for that item.
Computer-Assisted Master Scheduling
By defining time fences for master scheduled items, you can let MRP control orders outside of a specified time period and allow the master scheduler to control orders within that time period. To use this approach to master scheduling, specify a planning horizon, in calendar days, for each master scheduled item in the Time Fence field in Item Master Maintenance (1.4.1) or Item Planning Maintenance (1.4.7). When MRP plans orders for these items, it will not schedule order due dates within this time fence.
Note: The time fence for an item should generally be equal to the cumulative lead time for that item.
To use the computer-assisted approach for master scheduling, set the following values for each master scheduled item in Item Master Maintenance (1.4.1) or Item Planning Maintenance (1.4.7).
Master Schedule
Yes.
Plan Orders
No.
Order Policy
Any option other than blank.
Time Fence
The cumulative item lead time.
Selective Materials Plan
Selective Materials Plan (23.3) lets you plan master scheduled items separately from MRP items. If you use the computer-assisted approach to master scheduling, you may want to run Selective Materials Plan as follows.
1 Run Selective Materials Plan for master schedule items only.
2 Adjust the master schedule and rerun Selective Materials Plan as needed.
3 Run Selective Materials Plan for MRP-scheduled items only.