Multi-axis and Rotary
Indexed work in one setup, so features referenced across faces do not accumulate datum-transfer error.
A fourth axis changes what a three-axis machine can hold. Features on several faces can be cut in one setup, which removes the datum transfer that multiple setups introduce — and datum transfer, not the machine's positioning accuracy, is usually what consumes the tolerance between faces.
Kitagawa MR200 rotary table
| Specification | Value |
|---|---|
| Table diameter | 202 mm |
| Centre height | 140 mm |
| Indexing accuracy | 60 arc-seconds |
| Repeatability | 4 arc-seconds |
| Brake | Triple-disc pneumatic |
| Mounted on | VC Ez 410 IP |
Figures from the RAVIS capability profile, p. 11.
What indexing accuracy means for your part
60 arc-seconds is roughly 0.29 milliradians. Over a 100 mm radius that is about 29 µm of positional deviation at the feature — before anything else in the stack is counted. Repeatability of 4 arc-seconds is the figure that matters when the same index position is returned to across a batch, because a systematic offset can be corrected while a random one cannot.
When a fourth axis is the right answer
- Features on two or more faces that carry a positional tolerance between them
- Bolt circles and radial features that would otherwise need a separate fixture per angle
- Parts where the second setup would need re-indicating by hand on every piece
When it is not
If every feature lies on one face, indexing adds setup time and buys nothing. And if the part needs true simultaneous five-axis contouring rather than indexed positioning, that is a different machine class — we will tell you so rather than approximate it.
Send the model with the datum scheme marked and we will say which route the part should take.