93
Managing with the Master Schedule to see if we can get the materials.” To imply otherwise is to send the signal that schedules are of no great importance and can be changed at will.
Sometimes we simply have to say no to change requests. But instead of an absolute no, we should say something like this: “I can’t move that order up because the production schedule is currently booked. If you would be willing to move one of your other orders to a later date, however, I might be able to use that capacity. Do you want me to look into that?” This response helps the salesperson understand the limits of schedule fl exibility, and conveys the important idea that trade- offs are often the answer.
For companies whose traditions have been to refl exively accept or- der changes, the greater care and study suggested here may not be agreeable to everyone—especially at fi rst. Sales representatives who routinely telephone in order changes and get an instant answer will not like being told “We’ll get back to you after we do some check- ing.” One of management’s challenges is to help these people see that a more thoughtful way of handling order changes is in the company’s best interests.
Of course, computer software continues to get better and better in its support of demand and supply balancing. However, it’s not just about computer software. The company must have solid processes that approach Class A to make use of the software available today. The movement in the twenty- fi rst century is to customer and supplier col- laboration and the sharing of information. This is what might be called real Class A integrated demand- driven Supply Chain Management.
where necessary, given product lead times, lot sizes, and safety stock requirements. We also observed how a planning time fence can be used to create a boundary between time periods in which the com- puter proposes and the master scheduler disposes.
One way in which computer and scheduler communicate is through action messages (also known as exception messages). Action messages are the master scheduling software’s way of getting the master sched- uler’s attention and directing it to areas of potential problems. They identify the need for intervention to correct a current problem or to avoid a potential one. Examples of action messages are release an order, reschedule- in, reschedule- out, cancel, convert a computer planned order to a fi rm planned order, and so forth.
Figure 4.1 provides an example in which several of these action messages appear. Here, the planning time fence is somewhere beyond period 8; thus, all the numbers in the master schedule row represent fi rm planned orders (FPOs).
Demand for the product is stated as 50 units per period. With 70 units on hand, the MPS logic projects the available balance for each period. An FPO for 115 is scheduled to be received in period 2. (The lot size was 115 when the fi rm planned order was created, or the mas- ter scheduler had decided to override the lot size specifi cation of 125 when the order was placed, or 10 have been received or scrapped, or the like.) The above discussion could be true if the company manu- factures to a rate and expresses this rate using fi rm planned orders.
It is the master scheduler’s job to keep the master schedule line valid in quantity and due date. Remember, inside the planning time fence only the master scheduler can create orders and alter released and fi rm planned order dates and quantities. Additional FPOs for 125 have previously been placed in periods 5, 6, and 8.
A potential shortage of 15 units is projected for period 4, but a positive projected available balance reappears in the next period (60 in period 5). Subsequent periods project additional positive balances (135, 85, and 160). Because the projected available balance goes nega- tive in period 4 and then returns to positive, the master scheduling system recognizes that a timing, not a volume, problem exists. The master scheduling system notes this and looks into future periods for
95
Managing with the Master Schedule
orders that could be moved up. Since an FPO for 125 units is sched- uled to be received in period 5 and really is needed in period 4, the system generates an action message recommending that the FPO in period 5 be rescheduled-in to period 4, thus solving the defi cit prob- lem.1 The computer would also scan future periods and spot the larger than needed available balance of 135 in period 6. If the scheduled FPO for this period was not received, the 60 remaining from the pre-
Figure 4.1 Action Message Example
1 Only 15 units are needed here, but most master scheduling and material require- ments planning systems recommend bringing in the entire lot. However, the master scheduler has several options: Split the lot of 125 into 15 and 110; increase the planned order in period 2 to 130; do nothing; and so on.
vious projected balance would be more than enough to cover period 6’s demand of 50 units; 10 units would, in fact, be left over. This being the case, the software would send an action message to reschedule- out the 125 units from period 6 to period 7.
Scanning still further, it would be clear that the FPO of 125 units in period 8 is not needed if the projected demand beyond period 8 is less than 35 units, and a cancel message would be sent to the master scheduler for his or her consideration.
In addition to the action messages discussed here, the master sched- uling system would notify the scheduler that the FPO due in period 2 should be released (e.g., converted to a released order, such as a work order) since the item under evolution has a one- period lead time.
To review, a master scheduling system generally has the capability to analyze the supply/demand balance and to generate the following key action messages:
• Convert fi rm planned orders into released orders
• Convert computer planned orders into fi rm planned orders
• Reschedule released orders or FPOs into a closer time frame
• Reschedule released orders or FPOs into a future time frame
• Cancel a released order or fi rm planned order
• A negative projected available balance exists within the planning time fence
• Demand requirements are past due
• Scheduled receipts or FPOs are past due
• A planned order release has inadequate lead time to properly or- der material or secure the necessary capacity (past- due release) Although the above listed action messages are considered the key ones, Enterprise Resource Planning and master scheduling systems today have the capability to generate far more exception- driven action messages.
97
Managing with the Master Schedule