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QcadCAM ignores path direction

Posted: Wed Aug 07, 2019 10:33 am
by frantheman
Good day,

I have been using QcadCAM for 3 years now - recently noticed an issue with circles and direction of cutting. I don't know if the issue has always been there, but I only noticed it recently. It seems that the CAM processor ignores which direction you specify on the toolpath, and uses the codes G2 / G3 randomly. Attached DXF with multiple toolpaths all specified as direction-Conventional/Right.

When I export the G-code (using G-code offset (mm) as required by my machine) I notice the following:

N1860 G2 X-140.5 I-140.5 J0 F800
N1870 G2 X140.5 I140.5 J0
N1880 G1 Z5
N1890 G0 X100.7627 Y-100.7627
N1900 G1 Z-2 F200
N1910 G3 X-100.7627 Y100.7627 I-100.7627 J100.7627 F800
N1920 G3 X100.7627 Y-100.7627 I100.7627 J-100.7627
N1930 G1 Z5
N1940 G0 X90.1561 Y-90.1561
N1950 G1 Z-3 F200
N1960 G3 X-90.1561 Y90.1561 I-90.1561 J90.1561 F800
N1970 G3 X90.1561 Y-90.1561 I90.1561 J-90.1561
N1980 G1 Z5
N1990 G0 X128.5 Y0
N2000 G1 Z-3 F200
N2010 G2 X-128.5 I-128.5 J0 F800

G-code also attached.

Why would it create toolpaths for both clockwise and counterclockwise - when only clockwise paths has been specified? At this point I need to manually edit my NC files and replace all G3 with G2. And if I don't - I break router bits.

Please assist

Qcad/CAM details:
Version: (3.23.0)
Build Date:
Jul 18 2019
Qt Version:
MSVC++ 12.0 (2013)

OS: Windows 10

Re: QcadCAM ignores path direction

Posted: Thu Aug 08, 2019 12:06 am
by CVH
First CW and CCW are more convetionally.

The polys are CCW
The two outer ones and the inner one are CW
Two are Circle Entity so CCW


Re: QcadCAM ignores path direction

Posted: Thu Aug 08, 2019 8:39 am
by frantheman
Thank you for the reply. I agree CW and CCW are more correct - however when you specify the path direction on the CAM profile QcadCAM uses "Conventional/Right" and "Climb/Left". Maybe this should be addressed then?

I did some more investigation:

Procedure as follows:
1. Create a circle with the draw tool.
2. Create an offset of the circle using the "Modify - Offset with distance" tool

Create a CAM profile for both these entities.

What happens is that Qcad now decided the offset that I created by using the offset tool is an actual polyline, and not a circle anymore. The polyline now has a direction field associated with it - which overrides any CW or CCW CAM profile settings. Setting the CAM profile to "Conventional/Right" or "Climb/Left" has zero effect on a polyline. Weird. These settings do however change the direction that the CAM processor uses on a circle - which is the way it should be (according to me).

Is this correct? My guess would be that the CAM profiling is independent of the actual polyline direction?

Re: QcadCAM ignores path direction

Posted: Thu Aug 08, 2019 11:34 am
by CVH
CW / CWW are well defined.
Depending on the motion and the spindle direction and the side of the cutter in action we can speak of Conv./Climb cutting.