5 axis machine XYZAC Traj planner

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12 Mar 2021 15:03 #201976 by ioiotutu
Hi,
i have a 5 axis machine running on debian10 and linuxcnc 2.8.1 with TCP control using 5axiskins.c adjusted for my rotary axis configuration. All works fine but when the path is a 3D surface the CAM generate many linear movement G1X...Y...Z...A...C... and G64 command doesn't work fine. The result is a jerky movement. It seems that the machine stop and run every block like a G61 command.
Changing aceleration or feed on axis the situation is better and the worked path is not so bad.
Is there a solution? I read that the new trjectory planner does'nt work on rotary axis. Is it true?
Thanks,
Michele

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12 Mar 2021 15:27 - 12 Mar 2021 15:34 #201986 by chris@cnc
Hi,
i am not so far that my 5 axis fully working but i use xyzac-trt-kins. I don't know the different but maybe you can try this modul...
I pick up from here linuxcnc.org/docs/2.8/html/motion/5-axis-kinematics.html and here forum.linuxcnc.org/10-advanced-configura...kinematics?start=290
Last edit: 12 Mar 2021 15:34 by chris@cnc.

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12 Mar 2021 17:54 #202003 by ioiotutu
The kins that you are using is similar to my kins, and work well.
My problem is small linear movement on surface, this movement aren't smooth but jerkly. Here is a piece of program that work a sferic surface:
...
G1X74.966Y0.015Z-33.82A48.337
X74.482Z-33.277
X74.046Z-32.793A47.596
X73.554Z-32.255
X73.112Z-31.778A46.855
X72.612Z-31.245
X72.163Z-30.776A46.113
X71.656Z-30.249
X71.201Z-29.787A45.371
X70.71Z-29.289A45.055
X70.225Y0.014Z-28.811A44.63
X69.759Z-28.351A43.888
X69.235Z-27.848
X68.762Z-27.395A43.147
X68.232Z-26.898
X67.753Z-26.453A42.405
X67.215Z-25.962
X66.731Z-25.525A41.664
X66.185Z-25.039
X65.695Z-24.61A40.923
X65.143Z-24.131A40.924
X64.647Y0.013Z-23.71A40.183
X64.088Z-23.237
X63.587Z-22.823A39.443
X63.029Z-22.365A39.339
...
The movement aren't continuos.
It is the same in 2D when a path is made of multiple small linear movement and G61 is active.

I'll try your kins.

Thanks,
Michele

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13 Mar 2021 01:06 #202045 by andypugh

ioiotutu wrote: I read that the new trjectory planner does'nt work on rotary axis. Is it true?


Sadly, yes, that is true. The TP improvements are only applied to XYZ. Motion that includes rotary motions reverts to the old trajectory planner.

There isn't much wrong with the old planner apart from it having only one-line lookahead. This can work very well, as long as the segments are reasonably long in comparision to the machine speed/accel profile.

It sounds like you are the wrong side of that ratio.

Is there any way to tweak the CAM to create longer segments, or to use G2 G3 instead of polygons?

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13 Mar 2021 01:08 #202046 by andypugh
Have you tried tweaking the "naive CAM detection"? It sounds like you have naive CAM after all.

linuxcnc.org/docs/2.8/html/user/user-con...#_trajectory_control

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13 Mar 2021 08:32 #202071 by ioiotutu
OK i understand. I 'm using Alphacam, but i don't know it very well so I selected default parameters for 3D path, probably i can select different segments long but i don't know if it is able to generate G2/G3 on the surface.
I'll check the acc/vel for trajectory control to trim better my axis.
Thanks.

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