On Fri, 30 May 2014, bruno wrote:
> Date: Fri, 30 May 2014 17:29:28 +0200
> From: bruno <[email protected]>
> Reply-To: EMC developers <[email protected]>
> To: [email protected]
> Subject: [Emc-developers] bug with nurbs ?
>
> Hello,
>
> I wrote a quadrangle pocketing routine in G-Code which uses nurbs
> (G5.2). The motivation for this is that I dislike the current ngcgui
> routine (qpocket) for a couple reason. When qpocket cuts from one quad
> to another, "spiraling out", it actually cuts a scaled quad, then adds
> one edge where it slowly cuts toward the next scaled quad. That cut is
> really slow and is superfluous if the cut was really following a quad
> spiral instead. Second, and most important for me, the cut fully digs in
> on each corner (depending on the angle of the corner of course, but
> generally it is pretty big).
>
> So the width of cut goes from the overlap set for each pass, to almost
> the full endmill width. Maybe not important on a big mill, but I have a
> mini-mill and I like to try to cut at full depth if possible and with
> very small overlap, on many fast passes, it gives (I think ) better
> finish and wears the mill more evenly. (kind of like with adaptative
> clearing). So the way corners are cut is really a problem with qpocket.
>
> Here is the fruit of my experiments using nurbs, pasted below. The nurb
> weight are scaled with an exponential as the path comes closer to the
> final pocket shape, to (un)round the corners progressively. The function
> is parametrable.
>
> The preview looks great, however, when running it, I get a path that
> does not follow the previewed path ! And I see no reason for the massive
> divergence from the programmed path. See a screenshot here:
>
> http://imagebin.ca/v/1OCw5gNzXQBF
>
> http://ibin.co/1OCw5gNzXQBF
>
> notice how the purple path has "wobbles" in some sections, which go way
> aside the previewed path.
>
> I tested with the sim on linuxcnc 2.5.3
>
> At first sight it really seems to be a bug as the preview looks correct.
> Could anyone test this on their setup ? Is there an explanation for this ?
>
> Thanks !
> Bruno
>
At first glance it looks like the machine aceleration limits are not being
followed or G64 mode issue. Have you tried G64 Px.xxx?
>
Peter Wallace
Mesa Electronics
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