Definition
CAD (computer-aided design) creates and stores a part's geometry and requirements: the shape, dimensions and tolerances that define what the part is. CAM (computer-aided manufacturing) takes that geometry and a chosen process plan and generates the toolpaths and NC code a specific CNC machine uses to actually produce it.
Why CAD stays constant while CAM varies by factory
A part's CAD model doesn't change based on which factory makes it; its CAM program does, since different factories have different machines, tooling and postprocessors, which is why the same CAD file can lead to different CAM programs in different shops.
Where each fits in the workflow
CAD produces the drawing and 3D model themselves; CAM operates downstream of them, in preparation for a specific machine to run the job, and isn't reflected on the drawing.
Common mistakes
Assuming a CAD file alone is enough to start machining; without a process plan and CAM program specific to a given machine, a CAD file describes the part but doesn't yet instruct any machine how to make it.
A part's CAD model doesn't change based on which factory makes it; its CAM program does, since different factories have different machines, tooling and postprocessors, which is why the same CAD file can lead to different CAM programs in different shops.
See how Blake reviews a partFrequently asked questions
Is CAM part of CAD software?
Sometimes bundled in the same software suite, but they are distinct functions: CAD defines geometry, CAM generates machine instructions from it.
Does the same CAD file always produce the same CAM program?
No, the CAM program depends on the specific machine, tooling and process plan chosen, which can differ between factories or even orders.
Which comes first, CAD or CAM?
CAD; a part's geometry and requirements need to exist before CAM can generate toolpaths to produce it.