Ron Pereira over at the LSSAcademy.com offered a really cool video that pits regular mass production vs. one piece flow, and his simulation produced a time savings with the one piece flow.
In his video, what I found to be as interesting as his presented material were the comments at the bottom by professionals in manufacturing.
They all seemed to think that one piece flow definitely has its place, and that it CAN be more efficient in certain contexts, but most of them also pointed out that, from a batch processing point of view, one piece flow doesn’t save any time when it comes to actually delivering the product to customers if the customers are in the same place.
For example, if you are folding, stuffing, and stamping envelopes, but they all have to go to the same post office to be mailed, there isn’t really enough of a time saving compared to the possible amount of trips to the post office under a per piece system.
Someone else also mentioned the idea of spreading each step in the one-piece flow out to several people vs. to one person, and the savings in time would not be outweighed necessarily by the fact that, now, several people are needing to be paid, instead of the one person.
Either way, I think, under certain circumstances (like building full sized dump trucks with different customers), one piece flow is definitely a time saver and waste reducer than building a ton of dump trucks and running the risk of some of them not being sold.
Plus, envelopes are way easier to simulate than building a bunch of dump trucks.