If you are at a cocktail party, and someone asks you to compare and contrast the differences between batch and continuous flowing processes, calmly lower your martini, grab the nearest table napkin, and proceed to draw the following picture:
Suppose we were in the toy car manufacturing business and there were three stages to building a car: the body, the wheels, and the paint. You decide the most optimal way to build the cars would be to batch them up into groups of ten, and send them from one stage to the next in one big batch.
If we assume it takes 1 min per car at each stage, then we would expect the following results:
Time to build first car: 21 minutes
Time to build first batch of ten: 30 minutes
Now, suppose we were to draw this picture on another napkin:
Only this time instead of manufacturing our cars in groups of ten, we build them one at a time in a one-piece continuous flow process. Were we to do this, we could expect these results:
Time to build first car: 3 minutes
Time to build first batch of ten: 12 minutes
In the continuous flow example, the first car rolled off the assembly in in 3 minutes (18 minutes faster than the batch process).
All ten cars were built in 12 minutes (an improvement of 18 minutes over the batch process).
To really impress your guests, you could then demonstrate your worldly knowledge and command of automotive history by explaining that this is precisely what Toyota figured out when it began competing with Ford’s mass production system.
Toyota realized that a continuous one-piece flow process:
* increases productivity – more cars in less time
* builds in quality – easier to spot defective parts sooner
* is more efficient – less material lying around
* reduces costs – less inventory
By this time, other party goers will have no doubt picked up on your conversation, and you will most likely be the life of the party with everyone hinged on your every word.
You could excuse yourself.
You could change topics.
Or you could pickup a copy of Jeffrey Liker’s excellent book, The Toyota Way, and prepare yourself for the next party.