Monday, July 25, 2011

The Porsche JIT Game - The Beer Game or the Lean Box Game?

There's a lean box game out there on the internet, but when you do a search it's very difficult to find any information on it. I've played a variation of this lean game before at a Bosch Rexroth lean demonstration and it shows the difference between batch and flow production very well.

The game was originally described in Jame's Womack's book Lean Thinking as the Porsche JIT game. According to the book, the game was used at Porsche prior up to the writing of the book, circa 1991. So it's been around for quite a bit.

The website, "The Blog from a Lean Thinker," has a pretty good description of how the game works, although the author refers to it as the beer game. The box game probably owes it's heritage to the MIT Beer Game, but the Porsche version is much simpler and easier to manage.

The Lean Box, as described in Lean Thinking:

  1. Operator 1 delivers batches of unfolded large and small boxes in 3 colours to two stations. 
  2. Operator 2 assembles the large box and puts an elastic band around it. 
  3. Operator 3 assembles the small box and puts an elastic band around it. 
  4. Operator 4 opens the large box, puts the small box inside, puts a piece of paper on top of the small box and closes the large box again, with elastic around it. 
  5. Operator 5 opens the large box and checks to make sure the small box and ticket are inside. 
As you can imagine, the fourth operation takes the longest and creates a huge bottleneck in the process. 

The best part of this game is the redundancy of opening that large box multiple times. It's easy to see the inefficiencies when looking at this simulation. And it's easy to figure out how to fix it and create some flow. 

But rather than fixing the obvious (not opening the box so many times, or rebalancing the work), the book suggests reducing lot sizes and only making when the next operation asks for it. Soon, with batches of 5, than 3, a good flow is achieved and the customer is able to randomly vary his order and still get the correct boxes. 

By not rebalancing, the game achieves the goal of showing how to manage inventory at the slowest process. 

The Lean box game or Porsche JIT game, is a simple lean game that shows the difference between push and pull production, with cheap materials. Everyone has boxes lying around their facility. 

Learn more about it in the book, Lean Thinking, where it's described on page 208, or you can just try it yourself. The rules are pretty simple. 

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