Smoother ARC support

Hi Sirs! Thank you advance for your good job ! I have question about precise of ARC support. Repetier i use for hobby on CNC3020 china machine and only for milling. If i made small vias about 2mm diameter by support function G02/G03. It is divide on segments and hole do not looks good :) So I tried change "MM_PER_ARC_SEGMENT 1" value on "0.1" Now it's great but..... in fast speed is it nonusable. Machine not running smoothly. I don't check if it's run back on start position (lost pulses?) I understand that Mega2560 has no enough computing capacity, or is it any way to make more precise? My idea is buy arduino Due, there is more computing capacity. Is it good steps for me? I tried build new firmware from your side on DUE type and in code is still "MM_PER_ARC_SEGMENT 1", i understand it is no important for another user with real 3D printers. Oscilator on DUE is more times quickly, but is real that benefit will be sufficient ? Thank You advance for answer, BR Alexandr.


  • I guess the problem is limited path planning. 16 buffered lines * 0.1mm = 1.6mm so max. speed is what you can achieve on 0.8mm at best (for safety we always calculate that we decelerate to jerk speed at end). So increasing bufferel lines would help. Only tests can say if AVR is fast enough or due is already required as it also contains some sin/cos which are incredibly slow but normally a rotation matrix is used and only every x steps updated with sin/cos if I remember right.
  • edited January 2017

    Might be too heavy on AVR , as it´s a threaded rod driven machine.

    if you want high Speed on G0 moves you should change to DUE,

    but playing around with step adjustment (Think quarter step  is ok for that)

    will give a compromise between Speed/Resolution.

    i also have a rod driven machine and changed to due because of Speed reason.

    regarding arcs i increased buffer to 80, runs fine

  • I increase PRINTLINE_CACHE_SIZE on 32 and it is really enough. My maximal speed of cnc is up to 1500mm/min and now it run clear and smooth! Thank you for best way to all !! BR Alexandr
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