G64 not slowing down

More
24 Apr 2017 03:53 #91929 by Nico2017
Hi,
I am just starting with linuxCNC, but tried to understand as much as I could of the documentation provided. Here is what I want to achieve. I am using a machine to draw a curve which is divided in a long series of straight segments (G1 moves) and curved segments (G2 or G3 moves). I would like to use the G64 P5Q5 trajectory planner as I don't need to exactly match the line and want to keep a reasonable good speed. However along this curve, I would like to be able to achieve one action (M64M68 then M65M68) which require the line draw to stop along the curve at a specific point to achieve this action. My issue is that the G64 trajectory planner does not seem to properly decelerate before reaching this point and the machine is suffering a large jerked motion stopping at the point. I would like to make this deceleration much smoother.

Here is an example in my Gcode:

Preamble
G21 (Units in millimeters) G90 (Absolute programming) G64 (Default cutting) G17 (XY plane) G40 (Cancel radius comp.) G49 (Cancel length comp.) G54 (relative coord system)
G64 P 5.000 Q 5 (plot path tolerance)
F45000 (initial feed rate)
... (list of G1 G1 G2 actions)
G1 Z -56.145
G1 X32683.510 Y2150.113
G2 X32683.611 Y2150.179 Z -57.686 I 2.507 J -3.737
M65 P3 (do action)
M68 E0 Q 4 (set a parameter to a given value to do action)
G4 P0.5 (pause)
M64 P3 (undo action)
M68 E0 Q 2 (set a parameter to a given value to undo action)
G4 P0.5 (pause)
G1 Z -57.686
G1 X32660.924 Y2186.047
G2 X32661.026 Y2186.110 Z -59.207 I 2.406 J -3.803
... (rest of the list of G1 G1 G2 actions)

I already tried several things:
-adding a smaller feed rate F2000 before entering in the action section and have given the initial feed rate F45000 at the action section exit. This seems to slightly make it better but once again the deceleration is not as smooth as the initial acceleration along the curve provided by the G64 trajectory planner
-I replaced the the M65->M63 M64->M62 to make the immediately digital output M64 and M65 becoming a synchronized with motion digital output. However this require a G1 or G2 or G3 action after them but I'd rather not specify any action at this point to remain general and because I want to stay at this point location. I did it because according to documentation the immediate digital output 'will break blending'. Without any specific action the synchronized digital output are however not applied and the trajectory planner go through the curve without stopping (if I remove the pause G4).
-The dwell (G4 command) for pausing seems also to break the cinematic of the G64 Trajectory planner and I don't know if it is supposed to make the trajectory planner decelerating or not.

I have also been looking at the .ini file in the TRAJ section but I am not sure that the problem comes from those value. Might be more about the way the Gcode should be used with the trajectory planner.

Thank you for your help
Nicolas

Please Log in or Create an account to join the conversation.

More
24 Apr 2017 11:46 #91951 by tommylight
Replied by tommylight on topic G64 not slowing down
You have something set wrong or you actualy have a 33 meter long machine??!!
If you have such a long machine, lucky you. In that case you should check the acceleration, if it is set to high the machine can cope with given tolerances so it will start and stop obruptly and jerk the machine.
We would need more info on the setup, and the confirmation for the machine length.

Please Log in or Create an account to join the conversation.

Time to create page: 0.075 seconds
Powered by Kunena Forum