[justinj]

I'm having an issue where corners are being rounded when there is no compensation or curves set in the GCode file, in fact the file specifically contains a G40 and G49 at the beginning to cancel any compensatory moves.
I've used the same GCode files before on my old install so I'm assuming it's either a wrongly configured setting or something new in LinuxCNC since my old install (2.6.4). This is the first time I've used these files since my upgrade (I changed my controller to a GeckoDrive from a cheap Chinese one at the same time as upgrading) and the only thing that I think is different is the max speed and velocity (The only one had to be quite low to avoid skipping steps).
I did notice the same issue occurring on vertical moves in other files where it would start lifting just before it got to the end but I had assumed that was to do with the higher speeds it was running at which is evidently not the case now I have encountered this file.

(Generated with: DXF2GCODE, Version: PyQt4 Beta, Date: $Date: Tue Jun 9 17:40:00 2015 +0200 $)
(Created from file: /home/cnc/Documents/CAD Drawings/Letters/N.dxf)
(Time: Sun Aug 27 21:02:48 2017)
G21 (Units in millimeters) G90 (Absolute programming) G64 (Default cutting) G17 (XY plane) G40 (Cancel radius comp.) G49 (Cancel length comp.)
G0 Z  15.000 


(*** LAYER: Letters ***)
T906 M6
S14000


(* SHAPE Nr: 0 *)
G0 X  42.286 Y  19.286
M3 M8
G0 Z   3.000 
F100
G1 Z  -1.200
F1200
G1 X  42.286 Y  65.689
G1 X  63.714 Y  19.311
G1 X  63.714 Y  65.714
F100
G1 Z  -2.400
F1200
G1 X  63.714 Y  19.311
G1 X  42.286 Y  65.689
G1 X  42.286 Y  19.286
F100
G1 Z   3.000
G0 Z  15.000 
M9 M5
G0 X   0.000 Y   0.000
M2 (Program end)

[justinj]

Turns out it's a combination issue of my new controller handling a higher max speed (but keeping the accel lower to avoid wobble in the gantry in sudden direction changes) and the result of a newer trajectory planning algorithm in 2.7 that was absent in 2.6.

[samco]

Yes.. you need to specify a path following tolerance. G64Px.xxxx