About the Lead Time Processor Algorithm

Basic Algorithms

The Lead Time Processor uses this algorithm to calculate Fixed Lead Time.

1. Sums the setup, move, queue, and finish hours on all operations in the item's current routing.
2. Divides the total by the average hours in a day on the DSC shift (the "default" shift).
3. Rounds up or down to the nearest whole number.
4. Posts the resulting number of days into the Fixed Lead Time field in the Item record.

The Lead Time Processor uses this algorithm to calculate Variable Lead Time.

1. Sums the run duration on all operations in the item's current routing.
2. Multiplies the total by 100 / the operation's Efficiency percentage.
3. Posts the resulting number of hours into the Variable Lead Time field in the Item record.

If an operation has a value in the Fixed Sched Hrs field, the Lead Time Processor adds that figure to the move, queue, setup, run, and finish times.

Use WC Calendar and Use Offset Hrs

The Use WC Calendar and Use Offset Hrs options ensure that the system's lead time calculations are more accurate if you are using operation overlapping and multiple scheduling shifts with varying hours per day. The following explains how using those two options will affect the calculations.

If some of the operations in the item's current routing have more or fewer hours per day than the shift, the date the MRP or APS planning arrives at when creating planned orders may different than the date the Scheduler generates.

Enable the Use WC Calendar option to factor in the variable length calendars and compensate for the extra hours available per day. If you select Use WC Calendar, the Lead Time Processor calculates a shift factor for each operation that does not use the shift. To arrive at this shift factor, the LTP uses the scheduling shift specified for the operation's work center, using this calculation:

(average hours per day from shift / average hours per day from operation's work center shift)

The Lead Time Processor then multiplies the shift factor by the fixed and variable times for the operation. For example, if an operation that uses a 10 hour/day work center has one hour per piece of run duration and the shift has eight hours, there will be 0.8 hours added to the cumulative variable lead time for the item.

This option allows you to factor the operation offset hours into the lead time calculations. If you clear the Use Offset Hours field, the Lead Time Processor simply accumulates the setup and duration for each operation as described above. This calculation assumes that each operation starts when the previous one finishes and gives no consideration to operation overlapping (which is defined in the Offset field).

When you select Use Offset Hours, the algorithm attempts to compensate for the overlap. When the Lead Time Processor encounters an operation with offset hours, it subtracts the previous operation's fixed and variable times from the running totals and adds the current operation's offset to the total fixed time. Therefore, the system assumes that the current operation's offset is the duration of the previous operation. It does not change the actual values in the move, queue, setup and run hours fields of the previous operation.