Re: [CAD_CAM_EDM_DRO] Re: Open (i think) design for a parallel robot (reprap ma

A decent parabola would require a rather large billet to start with, and a
lot of material to be removed. I agree that it would be a good test.

The proposed test came out of a discussion of quantization error, which
intrinsically prevents a hexapod from cutting a smooth plane, unlike a
Cartesian machine which could cut a perfect plane.

What I was curious about is how to measure the small-scale deviations from
the desired shape. Isn't this property called surface roughness? What is
a simple way to measure surface roughness?

-- Carl

At 11:44 AM 9/4/2006, gran3d wrote:

>Yes, a flat plane and a bowl are excellent tests for a hexapod. You
>might also include a parabola. The focus point would be a good (if
>analog) measurement of both the overall shape and the surface
>roughness. Use it to reflect the sun onto something. The fuzzyness
>would reflect the roughness. The evenness would reflect the shape
>accuracy.
>
>Carl Mikkelsen wrote:
>
> >What are good ways to measure surface smoothness? It would be
>interesting
> >sometime to attempt to cut a plane, and see what the error actually
>is, and
> >somehow estimate what portion is quantization related, vibration
>related,
> >calibration related, and simple actuator error related.
> >
> >
>One test I can think of is to try to cut a "bowl", the inside of a
>hemisphere. I
>would think a lot of motion artifacts would show up in that, especially
>stickiness
>or backlash in the struts.
>
>Jon Elson
>
>