DEMO — fictional range. Local brief only, NOT SENT. No personal data is collected or transmitted.
PROCESS
Every re-clamp adds a datum.
A part is made in setups, and each setup introduces a new reference. The error between two references is added to the part, which is why the setup count is a drawing decision rather than a machine decision.
- Turning between centres
- One axis for every diameter · the setup that keeps a shaft concentric
- Chuck turning
- Faster, but each re-chuck introduces a new axis
- 3-axis milling
- Faces and pockets from one direction · one datum, one setup
- 4- and 5-axis milling
- Features on several faces without re-clamping · fewer datums accumulated
- Fixture design
- What holds the part decides what can be reached and what distorts
- Deburring
- Always required, rarely drawn, and the step most often skipped
Why the setup count is worth designing for
A design that needs three setups is a design with three chances to drift. Where the part allows it, moving a feature so it can be reached in the same setup as the datum removes an error rather than tightening a tolerance to absorb it.
What a machine list cannot tell you.
Whether the process holds the tolerance on your geometry. A machine's published accuracy is measured in ideal conditions on a test piece, not on the part in front of it.
The question worth asking instead.
Which feature will be hardest to hold, and how will it be measured. A supplier who can answer that has thought about the part rather than about the equipment list.