Batch work, that is what it is.
I am making thirty identical objects at the moment. They are trays, about 330mm square, and each tray has eight little compartments. So by making a batch, certain ‘set up times’ will be split across the thirty. Let me give you an example, not connected to what I am currently making, but still a good example.
Suppose I need to shape a piece of wood that will be the back leg of a chair. Look at a dinning chair you have at home. It will probably be curved somewhere so the back leans from the seat. You get the idea. Now I need to make a jig or two that holds the wood while it is being shaped. It might take two hours to make these two jigs, but to actually use them to shape the wood may only take a couple of minutes. If I were making just the one chair, then in total, it has taken two hours four minutes (two hours for the jig, and two legs at 2 minutes each) to shape the two back legs, or 62 minutes each. If I was making a batch of ten chairs, then it would equate to two hours forty minutes (two hours to make the jig, and twenty legs at 2 minutes each), or 8 minutes per leg. You can see the time saving.
It is not all time savings though. Some tasks don’t save time no matter how many you do, as there is no set up time. For example, when you hand sand the sharp edge off a piece of wood and give it a little curve. This can only be done at a certain speed, no matter how many you do. Maybe if you do loads, you get slower as your arm starts to ache!
Anyway, I am keeping times of each task I perform in making the trays to see where the time savings are.
It will make interesting analysis.
To some people.