This article is written as a walkthrough for the understanding of what is Heijunka and its use in production.
What is Heijunka?
The slide in document below shows that Heijunka is defined as the levelling of workflow or production levelling. Toyota Production System (TPS) has defined Heijunka as levelling the types and the volume of produced goods and it is a prerequisite for “just-in-time” production. Both types of levelling (i.e. by volume and by product type) must work together for it to be effective. Traditionally, production volumes and product types can vary according to customer demands, poor planning or just because it is easy for the production to produce the goods in a sequence. The methods and goals of Heijunka are explained below.
The method is to balance the work load among manufacturing lines and it is essential to add planned buffers to improve raw material availability and to level demand spikes. The traditional erratic production demand must be smoothed out using it when applying Lean Manufacturing. The ultimate goals are to create a process that is stable, to improve delivery performance, to minimise fluctuations and to align production rate with demand.
The slide in document below shows the ultimate production levelling achieved through the levelling of production by volume and by product type. It shows that for a weekly orders of 350, the daily smoothed orders are 70 in which, each four types of products (namely Product A, B, C and D) are manufactured on a daily basis.
Consider another example as above for levelling by volumes: For an erratic production demand from Monday to Friday which consists of 180, 100, 50, 100 and 70 units respectively, the fluctuation is seen to be between 50-180 units for the entire week. This would mean that the production operators would be very busy on certain days and during the low production demand days, they would be looking for work to do.
By: Dr. Satnam Singh, PhD (Managing Director MBizM Group)