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Repetitive Planning Control

The repetitive planning process uses the planning time fence to help stabilize your material plans and minimize disruption to your short term shop floor and supplier schedules. You can control the nervousness of your repetitive material plans by specifying minimum and maximum rate changes that are enforced by the repetitive planning process inside the planning time fence.

Acceptable Rate Changes

There are two repetitive item attributes used by the repetitive planning process to stabilize production inside the planning time fence. The acceptable rate increase percent and acceptable rate decrease percent represent the percentage of the current aggregate rate by which your suggested daily rates can vary from current aggregate rates within a repetitive planning period inside the planning time fence.

Acceptable rate changes allow you to represent assembly constraints. For example, you might define acceptable rate changes for a repetitive assembly to simulate the rate at which you can realistically ramp production of the assembly up or down.

The repetitive planning process calculates acceptable rate increase amounts by multiplying the current aggregate rate by the acceptable rate increase percent. For example, if the current aggregate rate is 100/day and the acceptable rate increase percent is 10%, the acceptable rate increase amount is 10/day. Inside the planning time fence, the repetitive planning process could not suggest a daily rate greater than 110/day.

Similarly, an acceptable rate decrease amount is calculated by multiplying the current aggregate rate by the acceptable rate decrease percent. For example, if the current aggregate rate is 100/day and the acceptable rate decrease percent is 10%, the acceptable rate decrease amount is 10/day. Inside the planning time fence, the repetitive planning process could not suggest a daily rate greater than 90/day.

Acceptable Rate Increase

If the optimal rate is greater than the current aggregate rate plus the acceptable rate increase amount, the repetitive planning process suggests a daily rate that is equal to the current aggregate rate plus the acceptable rate increase amount. Using the earlier example, the repetitive planning process would suggest a daily rate of 110/day for any optimal rate greater than 110/day.

If the optimal rate is less than or equal to the current aggregate rate plus the acceptable rate increase amount, the repetitive planning process suggests a daily rate that is equal to the optimal rate. Using the same example, the repetitive planning process suggests a daily rate equal to the optimal rate for any optimal rate between 100/day and 110/day.

Acceptable Rate Decrease

If the optimal rate is less than the current aggregate rate minus the acceptable rate decrease amount, the repetitive planning process suggests a daily rate that is equal to current aggregate rate minus the acceptable rate decrease amount. Using the earlier example, the repetitive planning process suggests a daily rate of 90/day for any optimal rate less than 90/day.

If the optimal rate is greater than or equal to the current aggregate rate minus the acceptable rate decrease amount, the repetitive planning process suggests a daily rate that is equal to the optimal rate. Using the same example, the repetitive planning process suggests a daily rate equal to the optimal rate for any optimal rate between 90/day and 100/day.

The following diagram illustrates the conditions that must hold true for acceptable rate increase and acceptable rate decrease. Notice that the repetitive planning process is free to suggest any daily rate outside the planning time fence.

Undefined acceptable rate changes remove the planning time fence since they do not restrict the amount by which the repetitive planning process can vary suggested rates. This is not true for zero acceptable rate changes. Zero acceptable rate changes are used to restrict the repetitive planning process from suggesting any rate changes at all inside the planning time fence.

Undefined values allow the repetitive planning process to suggest changes to the current aggregate rate without restriction. Zero values prevent the repetitive planning process from suggesting any changes at all. For example, if you choose to make the acceptable rate increase zero and leave the acceptable rate decrease undefined, the repetitive planning process suggests a rate between zero and the current aggregate rate, but no greater than the current aggregate rate.

Overrun Percent

You can also use the overrun percent item attribute to control the nervousness of your material plans by allowing current repetitive schedules to overbuild by a small amount without incurring new suggested daily rates. In this way, planning overrun amounts reduces minor and unnecessary rate change suggestions.

The overrun amount is equal to the optimal rate for the planning period multiplied by the overrun percent. For example, if your optimal rate is 100/day and your overrun percent is 10%, the repetitive planning process calculates an overrun amount of 10/day.

The repetitive planning process only recommends a new repetitive schedule if the current aggregate rate is greater than the optimal rate plus the overrun percent. According to the previous example, the repetitive planning process only suggests a new repetitive schedule if the current aggregate rate is greater than 110/day.

The following diagram illustrates the relationships between the optimal rate, overrun amount, and the current aggregate rate.

The overrun percent for repetitive planning is analogous to acceptable early days delivery in discrete planning. Both attributes allow you to make the business decision that you would prefer to carry additional inventory for a short time, rather than disrupt your shop floor production schedules.

It is important to note that the overrun percent only applies for overproduction. As with acceptable early days delivery, the repetitive planning process allows you to build ahead and carry excess inventory, but does not allow you to plan a shortage. Because the overrun percent often results in overproduction within planning periods, use of this attribute can sometimes have an impact on subsequent planning periods. Later periods may need to produce less as a result of the excess supply produced in earlier periods.

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