Here is a SIPOC for an armature winding process (this SIPOC was made with the Microsoft Word template found on the templates page).
Note that this SIPOC is very high level (always the best place to start), and would be of value to new employees, customers, or leadership team members who are unfamiliar with the process.
In a case like this, it is common to create a SIPOC for each process step in the overall manufacturing process (lamination stacking, commutator placement, etc.), at which point many of the process details would become apparent, in an organized way.