QCAD.org Forum

Apologies if this has been answered, I searched the forum and Google...
I recently upgraded to QCADCAM from pro. Specifically, I upgraded for nesting and breakout gaps for laser cutting thin wood parts.
The breakout tool is intuitive enough, but I can't place a breakout on a spline because "Entity is not a line, arc or circle".
Is there a way to use the breakout tool on splines? I don't want to place breakouts on the straight areas of the drawing as they are mating surfaces during assembly, and any distortion from removal would cause interference. And I don't want to convert the splines to polylines, as that distorts the contour of the curve when machined.

Hi,

pflumph wrote: ↑

Sat Mar 11, 2023 7:09 am

And I don't want to convert the splines to polylines, as that distorts the contour of the curve when machined.

In that case only a workaround comes into my mind. "Break out segment" etc. works on splines. Would it be possible for you to post an example dxf to your post which indicates a few positions and needed lengths of the gaps?

pflumph wrote: ↑

Sat Mar 11, 2023 7:09 am

The breakout tool is intuitive enough, but I can't place a breakout on a spline because "Entity is not a line, arc or circle".

I think you mean a retaining bridge ... Called a TAB.

pflumph wrote: ↑

Sat Mar 11, 2023 7:09 am

I don't want to place breakouts on the straight areas of the drawing as they are mating surfaces during assembly, and any distortion from removal would cause interference. And I don't want to convert the splines to polylines, as that distorts the contour of the curve when machined.

Unless you know a G-Code to process a spline in direct ...

G-Code is all about G1 and G2/3 or line-segments and CW/CWW arcs.
Meaning that QCAD/CAM explodes your spline entities internally to arcs and/or lines before exporting them.
That doesn't differ much with polyline segments what can also be line and arcs-segments.

XP explodes the selected spline entities to polylines by preferences in App.Prefs.
Please have a look at menu Edit .. Application Preference .. Modify .. Explode.
Probably you need to increase the approximation accuracy by decreasing the tolerance.
I would not opt for 'explode splines to polylines with line segments'.
Explosion to tangentially connected arcs with a proper tolerance results in a far better approximation.
Remark that the better the approximation, the more and shorter segments are created.

Unfortunately this setting default is not drawing unit depending ...
... e.g. an approximation error of 0.1mm is hardly noticeable, 0.1inch is 25.4 times that large and 0.1meter is off the scale.

QCAD/CAM doesn't use this QCAD native preference for exploding spline entities.
After a little search ... CamSplineTolerance = this.splineTolerance = 0.01 by default.
Meaning that it can even be coarser or finer by including this.splineTolerance = 'value xxx'; in your postprocessor.

The next step before exporting G-Code is exploding polylines to line and arcs-segments.
Again QCAD/CAM explodes polyline entities internally but this doesn't require any further approximation.

Regards,
CVH