Your example has 4 steps and it is relatively easy to remember to do all steps. In my situation, I have had anywhere from 6-10 steps (multiple pages to be folded, return label, “please post” stamp) and it gets much more difficult to remember each step. You waste a lot of time going back to check that all 10 steps were completed for each piece.

Additionally, it a lot of cases, you need to match up a specific piece of paper with a specific envelope. For example, an uniquely addressed letter must go in the correct uniquely addressed envelope. If you find a mistake during OPF, you must go back and re-open many envelopes to find the incorrect one, wasting huge amounts of time, not to mention creating a lot of stress.

Using mass production, would the item be in stock and already tested? Wouldn’t the customer see the item in days rather than the entire time it would take to produce the whole thing from scatch?

In the example you showed, it relies on the fact that a single operator is present. What if for each envelope you folded, you had to wait for the tree to be cut down for the paper by a single person? Batch processing a tree for all the paper is surelt more efficient in this case?

When I work as a consultant I try to make my customers think in one-piece flow. But I have to admit that I sometimes also try to sell them “batch production” – but just in smaller batches than they work with today.

The reason is that it sometimes leads to more waste to run one-piece flow. Like in an office or a production where a process it too short to justify a transportation for each product. Then I rather talk about frequency of transportation between processes. Where they today hand over products (papers or parts) e.g. every 2nd day (could be much longer!) they now change to e.g. 2 times per day.

I use a self-made example to illustrate one-piece flow at courses etc.
Round 1: 10 workstations. All products = LEGO bricks at workstation 1. Now the operator should assemble 10 “products” running back and forth with parts doing assembly.
Round 2: The LEGO bricks are now placed a 5 workstations with one-piece flow.
Round 2 is 30% faster than round 1.
Approx the same result as you get.

I would like to make a video with my example and share it with you once it is ready.