Defining Heijunka, Batching & Takt Time

Defining Heijunka, Batching & Takt Time

By Discovery Lean Six Sigma

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Defining Heijunka, Batching & Takt Time

What would you say if you heard the word Heijunka in your next staff meeting?

“Bless you?”

Maybe. Nobody would fault you. Heijunka (pronounced hi-JUNE-kuh) is a word that many organizations have been using to garner serious results. It’s based on an old business principle that seems obvious, but goes relatively unpracticed:

If nobody is going to buy your product, don’t waste time and resources making it.

That’s basic economics, and at first glance, it seems like a principle every worthwhile business adheres to. But if you dig a little deeper, you’ll realize how many big, reputable organizations actually ignore this advice.

The Widget Example

Think about it like this – Company X makes black and white widgets. They sell an average of 500,000 black widgets per year and 500,000 white widgets per year. When the fiscal year begins, Company X prioritizes widget manufacturing above all else. The leadership wants to create all the widgets they need – one million in total – as quickly and cheaply as possible.

It makes sense. That’s called efficiency, after all. Right?

Not exactly. That’s called batching. It’s a process that’s been around since the birth of mass manufacturing.

The Failure of Batching

Many years ago, Taiichi Ohno (the father of the Toyota Production System, and, by proxy, Lean Manufacturing) decided he didn’t like batching very much. He realized that batching had some serious drawbacks, such as:

  • Customer demand is hard to predict – If a buying trend inspires a consumer frenzy over white widgets, Company X will need to adjust their process and drastically increase white widget manufacturing, which in turn takes away from black widget manufacturing.
  • Unsold goods don’t make any money – If Company X over-produced white widgets, they need to either throw them away or store them as unsold inventory. That’s wasted effort and an inefficiency.
  • Machines and personnel get overworked easily – A change in process requires a lot of startup and slowdown time, which can create inconsistent product quality and exhausted equipment and people.

Ohno, who had worked his way up from the Toyota manufacturing floor, recognized the inefficiency of batching, and believed he could improve manufacturing if he could just get everyone to slow down.

“The slower but consistent tortoise,” Ohno said, “causes less waste and is much more desirable than the speedy hare that races ahead and then stops occasionally to doze. The Toyota Production System can be realized only when all the workers become tortoises.”

The Heijunka Way

The Heijunka method of manufacturing can be deceptively simple (but very complex when it’s fully realized). It starts by measuring takt time – the time it takes to manufacture a specific product, ship it and get it into the hands of a customer.

It’s the rate at which customers buy a product. Once you know the takt time for every product your company creates, the next step is easy – work slowly. Each week, take your time and manufacture only enough product to cover demand and takt time. If there’s a surge in consumer demand, simply manufacture more of the product over the next week.

So long as you keep a small cache of safety stock, this approach keeps manufacturing patterns predicable, stable, and still flexible, which is exactly what Ohno envisioned when he reimagined the Toyota Production System.

The post Defining Heijunka, Batching & Takt Time appeared first on Six Sigma Daily.

By: James LoPresti
Posted: August 25, 2017, 12:22 pm

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