The Japanese lean method Heijunka pushes a production where the production flow of the parts market is continuously guaranteed despite market fluctuations. This avoids transport and idle times and distributes the time needed for materials over the entire production; bottlenecks in replenishment are taboo.

The origin of Heijunka

The Heijunka lean method was developed in the 1950s by Toyota production manager Taiichi Ohno and forms the basis of the Kanban and just-in-time production methods. At the end of the 1940s, Toyota could not assemble vehicles until the end of the month, as they had sufficient production parts available at that point. Therefore, the prerequisite for production planning according to Heijunka’s principle is a forecast of the likely products sold in the next periods.

Market analysis

Taiichi Ohno already knew back then that detailed, long-term market research would provide the necessary data for accurate forecasting – just like back then, customer orders, past sales data, studies on related industries and general market research (surveys, market analyses) are used for this purpose today. Once planning is complete, usually a period of one to three months is chosen, spare parts/important production components, for example, are kept in stock as a precautionary measure to absorb the fluctuations in demand mentioned above.

Retrofit and other optimizations

In order to implement Heijunka successfully, some kind of retrofit(optimization) of the production facility is indispensable. Machines and the material flow itself must withstand an economic test and, if necessary, be adapted to the production according to Heijunka – the production material must flow through the production process without much intermediate storage, batch sizes must be reduced (ideal: batch size 1). Human labor is also included in the planning. Only in this way can the trend towards the production of individually configured products (contract work) be taken into account.

Pull principle

For a functioning Heijunka, planners and logisticians use the pull principle. The customer places the demand to the manufacturer, whereupon the manufacturer starts the production. Each production unit (process section) reports to the previous unit what it needs to meet this demand.

The result of the Heijunka lean method: The respective production section produces what has been ordered according to demand. The above-mentioned forecast / market analysis over a period of up to three months thus helps to harmonize or level out production and inventory in the long term.

Picture source: © Kanban Consult GmbH / License: CC-by-sa/2.0

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