Hi,
From my experience as a 3D modeller, engineer and a CNC owner/builder/operator there are few things I would advise to account for if you want to machine something really precise:
1) 3D model is an approximation of most of not trivial shapes. in most case scenarios splines are the approximation curves. So if you actaully want to machine involutes this will introduce first error (this approximation in 3D model, that by definition is not "precise" as it is approximation)
2) than there is a CAM software that approximates your ideal shape for the second time (from your first approximation from 3D model). So next generation of errors is introduced.
3) than there is CNC machine itself that interpolates this second approximation written in G-Code. But there is actually quite little you can do about that easily, and if there is anything you can do it is a totally different field than first 2.
Perhaps you would like to consider using excel or open office to actaully generate coordinates of the points on the curve analytically.
From there you can just feed these to g-Code. As g-Code only uses straight lines and arcs splines will be interpolated by many straight segments anyway.
So by doing that you actually skip two levels of approximation. But this would most likely require substantial quantity of maths, depending on the case.
Alternatively you can try to feed inventor not with spline definition but with a equation curve of your profile. This way you will skip one level of approximation. and will only be left with CAM, but there you can set some very tight tolerance for approximation so error introduced can be limited to really insignificant level.
This is actually the approach I took for a cycloidal curves.
Cris
Cris,
https://simply.engineering
