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Production Scheduling – Level the Volume

Level the Volume

This post is part of our series discussing the 7 lean manufacturing guidelines. In this post we’ll discuss supermarkets as a way to design a lean future state.

Post 1: The 7 Lean Manufacturing Guidelines
Post 2: Building to Takt Time
Post 3: Developing Flow
Post 4: Supermarkets & Pull
Post 5: The Pacemaker Process
Post 6: Leveling the Mix

This post will discuss the sixth of the seven guidelines for designing a lean future state, which is to level the production volume by releasing and withdrawing small, consistent increments of work at the pacemaker.

With this guideline we get to perhaps the least known of lean principles – pitch. Our goal is to release work to the pacemaker processes in small increments and to then manage each schedule to ensure completion.

Understanding the Pitch Process

Pitch is the lean term for the consistent increment of work released to production. The pitch period is the length of time that the increment of work covers. The value of pitch is to set the timeframe for management feedback and reporting. If you release work with a pitch period of a week, you’ll only know at the end of the week whether you achieved your week’s production. If you release work daily, you’ll know day by day but not more frequently than that. If you release by shift, each shift can know if they are ahead or behind. Or better, if you release with 4-hour, 2-hour, or even hourly pitch, you can know if you are ahead or behind much more frequently. The more frequently that you can monitor your production progress, the shorter your time to respond to issues that may impact your delivery to customers.

The broader concept is called fixed interval scheduling. With fixed interval scheduling, work is released to all operations in a consistent rhythm with all work linked to each schedule to track start and end time. Schedules produced for each pitch period must be confirmed to have available capacity and available material. With short pitch periods, scheduling can be very dynamic.

Working with Limited Staging Space

Fixed interval scheduling is an effective mechanism when there is a limited amount of space to hold products coming off production before shipping. In some very high volume plants, there may not be physical space to hold and stage products for shipping for more than a couple of hours of production. In these situations, the fixed interval scheduling process must also observe any requirements for shipping complete orders. That maybe especially challenging with products for a single order may be produced across multiple production lines. It’s in these situations of very high volume manufacturing that production scheduling must be highly controlled.

Fixed interval scheduling must be planned at least as far ahead as the lead time of make-to-order (MTO) sub-assemblies plus final assembly. In doing so, true MTO flow can be supported from feeder areas into final assembly. When feeder areas are not in flow, supermarkets provide an intermediate buffer to isolate upstream operations.

The future state design of your value streams across all operations must identify the pitch period and other requirements for fixed interval scheduling. Once in place, continuous improvement efforts should focus on the obstacles to reducing pitch to shorter and shorter intervals. The pitch period will be limited by the batching that remains necessary despite our best efforts to eliminate or reduce it.

Our final installment in the series is to use EPEI to calculate and then continuously reduce batch size.

Written By:  Phil Coy

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