I will look for you at the next party

All the best - JR

I totally agree with you. Every time I discuss batch vs. continuous flow at a party (with or without cocktails) it engages the interest, fascination, and admiration of all attending. And it is much better if you can draw it on a napkin. Sometimes you can even tear up some napkins, label them, and move them around to show the differences. Awe-inspiring stuff….

Anyway, I’ll toss in 2 more cents. Pretty much every implementation of continuous flow I’ve been engaged in results in inventory reductions of 50-90%, and floor space reductions of 30-70%. Defects drop off 90% or more, and labor efficiency increases 20-50%.

What never ceases to amaze me is why so many businesses continue to manufacture the “old way.” My first work in this area was in the early 80’s, and you would think by now every production manager and engineer would understand the concepts. Go figure.

Take care,

Greg

Yes you are correct. The throughput between the two system will be the same (all things being equal). The example was designed to compare and contrast the two systems as you said.

We can agree to disagree on it being academic

Chris mentioned that the “Full teams to work paint and wheels sit idle”. But I was assuming a resource (people) that could be moved between processes. Either imagine just one team who can build, put wheels on, and paint; or imagine that the teams “sitting idle” are not invited in that day and thus don’t draw down resources.

In either case for a given amount of resources (people), and with the ability to allocate those resources between steps as you see fit, then the throughput will be the same.

The example was designed to demonstrate that the “same” process is done more efficiently. But if you measure efficiency by person-hours, or dollars, in this type of thought experiment, you will find that they are identical. And if you have flexibility in where you put your resources, they are pretty much identical in terms of throughput, too. So touting the difference as one between processes is quite misleading, misleading enough that I would call it wrong.

This is all academic, really. Nobody doing real manufacturing has “batch” and “continuous” bandwagons they cheer for: they use gigantic models, simulated annealing and genetic algorithms, actuarial accounting, economic modeling, and reams and reams of PhD-level research to carefully tweak everything to manage the complex interactions of throughput, risk, and demand.

He is not wrong. In the example, the full teams to work paint and wheels sit idle until it is there turn to produce.

That is an astute observation.

In the batch processing example you have a lot of waiting (or waste).
As machines are working, you have idle inventory sitting there, doing nothing.

As you correctly pointed out, the continuous process doesn’t have that idle time. As soon as one product is finished, it is immediate sent to the next stage for processing.

Regarding the other example you describe. It is not a similar comparison. In the example I use above, the assumption I use in both cases is that the machine can only work on one car at a time. Obviously if you bought x3 machine your would triple output.

In your batch example, the cars are finished with 30 person-minutes of labor.

In your ‘continuous’ example… the cars are finished with 30 person-minutes of labor. The only reason that the time is shorter is because you have two more people working!!!

Consider if you had three people working at each step of the batch process: It would only take 3 1/3 minutes to build 10 car bodies; 3 1/3 minutes to put on wheels, and 3 1/3 minutes to paint them. For a grand total of: 10 minutes! Batch processing for the win!

* is more robust - because continuous flow is so disruptive due to equipment failures, workers are forced to fix root cause problems fast

This is another fascinating aspect of the Toyota Production System (TPS).
I hope to write more about this later.

In this context continuous flow refers to the continuous movement of cars from one stage to the next many cross functional teams working together on one car at a time.

One of the many differences between batch processing and continuous flow is the amount of WIP (work in process). Batch process have a lot of WIP. Lean manufacturing tries to minimize WIP.

Cheers