Hi!

Happy Valentine's!!! I'm looking for a company we can make a good benchmark in heijunka system. Does anybody knows someone doing this? We are in the automotive industry.

regards,
soulma

"heijunka" or production smoothing, is one of the tools of Lean Manufacturing. Folks who are involved in Lean or Supply Chain Management refer to this visual "flow picture" to make minor adjustments to production, inventory, staffing, etc. in short intervals - hours versus days or weeks in conventional systems.

I don't recall seeing anything recent using the term "heijunka" in the Advanced Manufacturing Forum over in ASQ.

I have no personal experience using the system at all. Perhaps folks familiar with the Toyota Production System have a clue?

Heijunka is a Japanese term that refers to production smoothing in which the total volume of parts and assemblies are kept as constant as possible throughout the value stream. A Heijunka box is a visual scheduling mechanism that distributes work into small time increments and ensures level work load.

In a dual kanban system, the heijunka box contains production kanbans or signal cards. How do you compute the numbers of cards in a heijunka box? One example of the use of a heijunka box is in leveling production and shipping. For our purposes, let's assume a box per product produced. It is filled with kanbans. Each production kanban signals the start of a production cycle that pulls a minimum product lot size. A withdrawal kanban from shipping triggers the pull of a production kanban.

The issue is how many kanban cards should be in the heijunka box?

The key factors to consider are:

* Customer demand for product over a given period of time (usually one shift for one line)
* Lead time to produce the product lot size (replenishment rate; use the same unit of time as you used in representing customer demand - e.g., hours)
* Safety stock expressed as a percentage of demand during lead time (if the total demand is 100 units and the safety stock is 10 units, then the safety stock value you should use is .10)
* Production lot size

Here is a formula offered by Professor Herbert Tuttle, University of Kansas.

To compute the number of kanban cards, use the following formula.

Number Cards Needed = [(Customer Demand x Lead Time) x (1+Safety Stock)] / Production Lot Size. If the computation produces a fractional result, then round up.

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I also found this link that should be helpful: http://www.si.umich.edu/ICOS/Liker04.pdf

This one looks pretty good too: http://www.bmpcoe.org/bestpractices/pdf/uec.pdf