Definition
What is process planning?
Process planning is the systematic determination of the best way to manufacture a part: choosing appropriate operations, machines, tooling and their sequence, with the goal of satisfying the part's requirements at a workable cost and lead time. It sits between product design and manufacturing execution, translating a part's geometry and requirements into an actionable plan.
Computer-aided process planning (CAPP) is the application of software to assist process planners in this task, and has long been considered a key connecting technology between computer-aided design (CAD) and computer-aided manufacturing (CAM).1
Variant versus generative planning
CAPP systems are traditionally divided into variant planning, which retrieves and adapts an existing process plan for a similar part, and generative planning, which attempts to derive a new plan automatically from a part's geometry and requirements. Despite four decades of active research, a fully generative CAPP system that reliably handles arbitrary parts and real factory constraints remains an open problem; most production CAPP tools assist a human process planner rather than replace one.1
What process planning actually produces
The concrete output of process planning is a routing: the ordered list of operations, machines, setups and times a part goes through. Getting there requires reasoning over manufacturing features, machine selection and manufacturability together, since a change in one (a tighter tolerance, a different available machine) can change what the best operation sequence actually is.
Frequently asked questions
Is process planning the same as a routing?
Process planning is the activity; a routing is one of its outputs, the resulting ordered list of operations, machines and times.
What is CAPP?
Computer-aided process planning: software that assists or automates parts of process planning, connecting CAD design data to CAM manufacturing preparation.
Why is process planning still mostly manual in many shops?
Because a fully automated (generative) CAPP system that handles arbitrary parts and factory constraints remains an open research problem; most real systems assist rather than replace a process planner.
Notes & references
- Alting, L. & Zhang, H. (1989). Computer Aided Process Planning: the state-of-the-art survey. International Journal of Production Research, 27(4), 553–585. https://doi.org/10.1080/00207548908942569 Classic survey of CAPP techniques, including the variant-versus-generative distinction and the open problem of fully generative planning.