Switching absolute coordinates (G90) to relative coordinates (G91)

Igor_Maia

Good evening, 

I'm a mechanical engineering resercher and I'm trying to adapt the G-codes generated by Repetier-host to a Laser-Direct Energy Depositon machine. During this process I'm facing some problems coused by the absolute coordinates setup. I would like to know how to switch the absolute coordinate to relative coordinates. Thank you for helping,


Igor Maia

Repetier

Actually G91 does that as you guessed. That is of course only for externally send g-codes. Internally firmware must work with absolute coordinates, so question is just is the send position absolut so we copy it or relative so we add it to last position. Problem with relative coordinates is that they can sum up rounding errors, so should be avoided e.g. for long sequences. That is why slicers create absolute positions.

What exactly is the problem you need to solve requiring relative positions? After all you can also use G92 to define a reference point for absolute coordinates changing the absolute position.