Heijunka / Leveling

Short Description

As customer demand fluctuates and may change within days or even hours, your production has to have some mechanism to protect your upstream processes. Leveling is one of these protections. It helps you to run a smooth production without having to react 1:1 onto your customer fluctuations. The Heijunka Box helps you as a tool to level your shop floor and avoids the bullwhip effect to be passed upwards your internal and external suppliers.

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Why do you have to implement Heijunka / Leveling?

Better schedule your Production

When leveling your production, demand for a defined time span (e. g. 1 week) can be forecasted. Hence Production Managers and Group Leaders can plan the shifts for that week more precisely. You can give a far better forecast towards your suppliers and improve your planning for machine and line changeovers.

Avoid the Bullwhip Effect

The bullwhip effect appears due to actions taken by different parties trying to limit fluctuations. In cases you have internal customers, your production will try to serve that demand. As that will happen delayed, you will even increase the peaks and valleys of that demand instead of limiting them. Those peaks will be passed forward upstream your process and supply chain making it more difficult to handle the demand.

Reduce Inventory and Throughput Time

When leveling your production and processes you also level the space needed to store WIP material and supplier parts. As you limit the peaks you also limit the space required between process steps and your storage.

How do you implement Heijunka / Leveling?

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Leveling by Decoupling your Process

  • Start leveling your production by decoupling your production from the customer. For example, increase the buffer of finished goods to cover peaks during 1 week of production. Or decouple inside your process chain between a pre and final assembly process.
  • By increasing that buffer, you smooth your production. This will result in far more benefits compensating the additional buffer you implemented by far.
  • Define the size of the buffer by simulating a production week based on history data. What size is needed to be able to fulfill the customer needs but fix your production schedule fix and constant for one week?

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Mixed Production Scheduling to reduce a Bullwhip Effect

  • Leveling your production means also to reduce batch-sizes. That will result in more changeovers.
  • By decreasing batch-sizes, you will reduce your WIP inventory and throughput time, giving you far more transparency and control on your shop floor.
  • Use the Heijunka Box to produce each product each day. Put Kanban cards inside the Heijunka Box representing 1 Finished Good pallet per card. Each Kanban card is a production order. Make sure to produce according to the Kanban card, card by card.

Enabler for:

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Downloads

Training document – Heijunka / Leveling (pptx)
Training document – Heijunka / Leveling (PDF)