Viewing a single comment thread. View all comments

buildyourown t1_jeb9aft wrote

Reply to comment by Scuka1 in Eli5: On a production line, how do they make a car, plane or anything else be identical from one another without differences? by SideburnG

Tools wear. Every part is going to be a little different. Materials also aren't perfect. Even with lots of quality control 1 heat treat lot might be a little different than another. The grain structure of materials are going to vary slightly. Etc, etc.

1

Ratnix t1_jebqjzg wrote

We do metal machining for the auto parts we make. The parts we make get randomly checked a couple of times per shift for all of the necessary specifications down to a couple hundredths of a millimeter variance.

If a part checks out of spec, the production of those parts are shut down and an engineer comes out to do what is necessary to make good parts again.

While they are doing that, quality control goes to the parts that were made by the out of spec machine and checks them, from oldest produced since the last line check, to the newest produced, until they find where the bad parts started getting made. They are then quarantined and sorted and measured, throwing out all out of spec parts.

They are all virtually identically, only having slight differences of no more than 0.02mm

1

Scuka1 t1_jedip7z wrote

Which is why I said "nearly identical", not "identical".

Tools wear, but to the naked eye that's not visible. There's also quality control and preventitive maintenance systems in place to make sure that tools don't wear out to the point where they start producing non-functional parts.

1