Tuesday, May 18, 2010

The Kanban System Game

At first glance this kanban game seems a little confusing, but once you understand the spreadsheet, it's surprisingly addictive. The kanban game is an Excel spreadsheet available from strategosinc.com, a website that also includes a wealth of Lean information. The game is free, but you have to sign up to the website to get the download. I was hesitant at first, but after playing for an hour, I think it's worth it.

The game simulates the production of 4 different goods. Each turn, a macro will generate the sales of the 4 products and you get to decide what to manufacture. Your constraints are the the size of your kanban buffer, or stock area, and the capacity of the machine. Keeping in mind that each time you switch products, the changeover takes 1 unit of time as well.

As a heijunka student, I immediately tried to level load and produce an equal amount of each product, every day. I soon found out that the fluctuations in demand created conditions where I produced too many of one product and not enough of another. See this chart of the buffer size after 50 game turns. You can see a ton of "yellow" and not enough "red" parts.

Realizing that heijunka only works when you know the customer demand and you can average it appropriately, I came up with another technique. Look at the buffer and produce what is needed, ie. kanban! Unfortunately, I gave myself another restricting rule of having to produce at least one of every product. I wanted to level load, but the downtime created by product changes were killing me! A fitting demonstration of the need for fast tool changes or SMED. So the next graph is much better, you can see the buffer remaining steady, with the dip in the middle caused by multiple turns of demand exceeding capacity and manufacturing being hampered by long product changes, or a limit on capacity.

The simulation provides detailed instructions about how to reduce the constraints, giving yourself a progressively harder game. I tried one more time at the hardest setting and started to get into the groove. I produced only 2 or 3 products each turn, focusing on the products with the lowest levels in the stock area. By the end of it, I didn't even look at the demand each turn, only the buffers. Just like you are supposed to do with kanban!

From a facilitation perspective, it might be a little dry to go through this with a group, but as a solo experience, I was surprised at how attached I became to my virtual spreadsheet!

The game is available here.

No comments:

Post a Comment