A process plan converts a part definition into an ordered manufacturing route.

The route specifies which operations create, locate, finish and verify the required features. It must respect both geometry and the evolving state of the workpiece.

Typical planning questions include:

• What starting form or near-net process is appropriate?
• Which surfaces establish datums for later setups?
• Which features should be created before a treatment that may change dimensions?
• Which precision operations should occur after major sources of distortion?
• When must inspection occur before a feature becomes inaccessible?
• Which operations require the same setup and can be grouped?

A generic route can look like

starting stock or near-net part
  ↓
rough geometry
  ↓
material / thermal processing
  ↓
finish critical features
  ↓
inspect functional requirements

Performing a precision finish before a later operation that predictably distorts the part would be poor routing, because the achieved accuracy can be lost.

Operations also create prerequisites for one another. A reference surface may need to exist before later features can be located from it; a feature may need rough creation before a finishing operation can refine it.

Process planning is therefore a dependency problem over physical operations. The best route satisfies drawing and material requirements while minimizing unnecessary setups, handling, inspection and rework.