DXF vs. SVG import format ?

[bLouChip]

It seems I read somewhere that SC prefers DXF import format vs. SVG format for a technical reason I don't recall. Is that correct ?
I'm using SC v7.1.35.

Reason I ask is that I have been using SVG format since I began using SC about 2 years ago, and of course if it ain't broke, don't fix it; so when ever I read what I thought I read above, I just kept using SVG because it was working fine. Well, now it just broke; an SVG import of 7.62mm circles did not get fully recognized as circles in SC. What I mean by that is for the purpose of leadin arc beginning in circle center in an Inside Offset Operation, and for the purpose of a Plasma Drill Operation, SC recognized the shapes as true circles just fine. However, for the purpose of Path Rules 'on small circle' qualification, it did not recognized the shapes as circles. So I tried a DXF import format (from my CAD LightBurn v1.5.01) and SC recognized the shapes as circles in all cases.

in the case of the SVG format, the circles have a short vertical 0.038mm line segment at 3 and 9 o'clock positions joining together the top and bottom hemispheres, the DXF format does not have these segments. The SC 'Circle recognition limit' setting is 0.2mm, but then that setting quick help implies its only used for drilling operations, which do recognize the shape as a circle.

I'll switch to using DXF import format going forward, was just curious about SC's preference.
Also, I sort of suspect LightBurn new version as the culprit here, I've had circles this size and smaller work just fine in SC and imported as SVG format, but then SC recognizing the shape as a circle in some use cases but not in Path Rules is strange also.

[Les Newell]

Historically SheetCam's SVG import was a bit buggy but these days it is pretty solid. These days the choice of file format mostly relates to the application the file was exported from. For example Inkscape has history of isses with it's dxf export so I generally recommend SVG with Inkscape.
In your case I suspect the issue is that Lightburn is outputting the circles as bezier curves. Beziers can only approximate a circle. As G-code cannot understand bezier curves directly, SheetCam jumps though a number of hoops to try to match Beziers to arc segments. As a last resort it sometimes just converts the beziers to a series of short straight lines.

You may be able to improve the SVG import by going to Options->application options->drawing import and increasing the arc fitting tolerance. However this is hiding the underlying problem rather than fixing it. It can affect the accuracy of the resultant tool paths.
If dxf is working better for you, I'd suggest sticking with it.

The 'On circles' rule is pretty strict about the geometry. It has to be a circle or a number of circular arcs that are exactly on a circle. Hole centres for drilling on the other hand are a lot more tolerant and anything that is even roughly a circle will be recognised. The circle recognition tolerance setting is purely for drilling.

[bLouChip]

Thank you Les. Good info.
I’ll switch to dxf format going forward. Not a problem.