How to Select The Appropriate Time Bucket for the MRP Process

Executive Summary

• The MRP process requires the selection of a planning bucket.
• The planning bucket changes based on the application.
• When selecting a planning bucket for MRP, users face a trade-off that must be considered.

Introduction to Selecting the Right Planning Bucket

The planning bucket is one of the primary control areas of the planning system. You will learn about the planning bucket and its interactions in this article.

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What is the Planning Bucket?

The planning time bucket is how the timeline is divided for planning purposes.

It should not be confused with the storage bucket. The storage bucket is how the planning data is stored by the system, a different relationship to the MRP process. Of course, the storage bucket must always be smaller than the planning bucket.

How the Planning Bucket Changes Depending Upon the Application

Some typical timings in different planning systems are listed below:

• In demand planning, it is usually a week.
• In supply planning, it is either a day or a week.
• In production planning and scheduling, it is usually the day.

Plossl’s Observations on the Timing of the MRP Process

George Plossl had an interesting observation on the planning bucket from his book Orlicky’s Material Requirement’s Planning…

“When selecting the size of the MRP time bucket, users face a trade off between the desire to have planned events pinpointed in time and the need for clear and simple ordering data. Specifying order completions by month is less than helpful to shop supervisors. They need to know what next to produce for this week or better yet today. When several hundreds or thousands of shop orders are due in October, but MRP schedules provide no relative priority information, shortage lists and expediting will replace the formal system and performance will deteriorate. Planning is not an exact science, in spite of the apparent rigor of MRP calculations. A one week time bucket is most common, except in a few businesses like food, pharmaceuticals and fine chemical manufacturing, where production times are very short. In other types of manufacturing, one week is reasonable for order releases, completions, priorities, lot sizing and load reporting.”

This indicates important trade-offs for the MRP process and the setup of the MRP system. It is essential to acknowledge that these trade-offs exist and their implications on the MRP system’s timing settings.

Conclusion

George Plossl is correct, and this is the most common planning bucket for the MRP process. However, it is interesting to hear the positives and negatives laid out by a person quite experienced in the area.

Learn about the history of MRP at this link.