Drag knife compensation: lifting the tool while changing direction

[GoogleCodeExporter]

Dear Dan,

thank you very much for helping so fast with the previous drag knife 
compensation issue!
I added the line in 'kurve_funcs.py' and now I get the resulting G-Code.

But, using cutting tools like e.g. the 'Donek' drag knife or a self build 
roller cutting tool in order to cut thicker materials, it is necessary to lift 
the blade before performing the compensation movement which changes the 
orientation of the cutting blade and to lower it again before continuing to cut.

Is this possible with heekscnc already - or does the offset function in the 
curve class has to be updated in order to produce G-Code with XY-compensation 
with Z-lifting and lowering?

Thank you very much for helping!
with best regards,
Felix

Original issue reported on code.google.com by Felix.b...@softpath.de on 14 Oct 2014 at 8:16

[GoogleCodeExporter]

Hi Felix,

Currently, the function is receiving a Curve and modifying it.
https://code.google.com/p/libarea/source/browse/trunk/Curve.cpp#783

If it finds a sharp corner, it adds an arc
https://code.google.com/p/libarea/source/browse/trunk/Curve.cpp#826

We would need to change the function to return a list of curves.
I could add a parameter to the OffsetForward function, to specify to break it 
up like this.
Would the compensation move still need to be the same shape?

Original comment by danhe...@gmail.com on 14 Oct 2014 at 8:26

• Changed state: Accepted

[GoogleCodeExporter]

Hi Dan,

yes, I think so.

This is the text from 'Donek Tools': 'Sharp corners are achieved with what are 
referred to as corner actions within the CNC tool path. These corner actions 
instruct the CNC to raise the blade such that the tip is just barely in contact 
with the material surface.  The machine then moves through a very small circle 
around the tip of the blade causing the blade to rotate, while the tip of the 
blade remains in the same location.  The machine then moves the blade back to 
the cutting depth and resumes cutting.'

It confirms the way you calculate the compensations by using parts of small 
circles.
The only difference is the added vertical movement for making the rotation easy 
and smooth.

Eventually, it is helpful to allow a lower speed (e.g. 300) while performing 
the compensation movement because cutting speeds (e.g. 6000) could be very 
high…this would be perfect!

Thanks a lot and with best regards,
Felix

Original comment by Felix.b...@softpath.de on 14 Oct 2014 at 8:48