It takes lots of planning and coordination. You have to study how much time it takes for each part and when they need to be assembled, then "balance" the work load between all of the line operators.
The Industrial Engineers (IE's) are the ones who are responsible to time how long it takes to put each part on. They time the operators to see how long it takes. The operators try to slow down when they notice that the IE's are timing them (obvious when they have stop watches) so they don't get more work added to their station. The IE's try to hide behind poles, boxes, etc to catch the operators by surprise, so that they are working at normal speed instead of stalling/milking it. The joke between the engineers is that a good IE can count with their toe, by tapping it in their shoe so the operators don't realize that they are being timed....
It's a cat-and-mouse game that goes on in the industry.
