XYYZBC-str config

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23 Aug 2020 23:40 #179159 by OT-CNC
XYYZBC-str config was created by OT-CNC
I'm working on a config for a gantry router with tilting/rotating spindle. I have looked over the docs and I'm trying to understand the differences between the kinematics as I'm new to anything beyond 4 axes.
For starters, I'm working on a standard 5 axis trivkins config with 6 joints, Y Y2 for gantry homing/squaring to get my mesa hardware connected and running.
If I understand correctly, TCP is not supported in trivkins? In trivkins mode, the head would work more like an indexer? For more complex work, TCP mode with proper CAM would work on 5axiskins and xyzbc−trt−kins only?
I looked at the vismach 5 axis bridge mill example and that's what I'm after with the addition of gantry squaring. Is that supported on 5axiskins or xyzbc−trt−kins? I don't follow if I need the additional W axis for tool offsets?
I read that in order to drive both Y axes, the kinematics module would have to be modified. I'm assuming it's, not as simple as modifying a hal or ini file for someone who hasn't programmed in C?
There is also switchKins that switches between modes. Has it be adapted and tested on a tilting/rotating head?
I'm on ver 2.8 and don't fully understand what each kinematics option has to offer and where I should focus my time. Any suggestions where to start?

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28 Aug 2020 13:23 #179831 by OT-CNC
Replied by OT-CNC on topic XYYZBC-str config
I'm still looking for guidance on the best 5 axis option

From another post from Andy:

Try running the sample simulator config sim/axis/vismach/5axis/bridgemill which should be a lot like your machine.

That uses this kinematics:
github.com/LinuxCNC/linuxcnc/blob/master...nematics/5axiskins.c

Which does not, as it stands, support a double Y axis. But it is a very simple change to make it do so. (You just need to add an extra joint and, in the kins, make it take the same value as its twin)

Or, you could connect the Y axis motor command to two separate stepgens. But the modified kins is the better way.


What is the workflow to add the double Y? I currently have a double Y in the hal and ini configs, how do I add the extra joint in the kins? Where is the 5axis kins located in my install and which file needs modifying?

TIA

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09 Sep 2020 16:02 - 09 Sep 2020 16:04 #181460 by Aciera
Replied by Aciera on topic XYYZBC-str config
Note that I don't actually have a 5 axis machine. I modified a 5-axis kinematic to use on a XYZA machine with a manual swivel head.

Regarding the the double Y: I think you can set that up in the INI like a gantry, set the homing offsets on your Y joints to be -1 (needs to be negative and the same number) then you can use the homing offsets to square the gantry when it homes.
I would think that the kinematic would not need to be changed because the calculated Y-position is fed to both motors.

Trivkins can be used for indexing as you say. With trivkins there is no TCP calculation in LinuxCNC that would have to be precalculated in a CAM that can do that.

Switchkins is a branch by Dewey Garrett that enables you to switch between different kinematics, for example between trivkins and xyzbc−trt−kins. This enables you to switch between TCP and Non-TCP mode.

I'm sorry I can't be more thorough but I need to head out the door.
This thread might be worth your attention:
forum.linuxcnc.org/10-advanced-configura...kinematics-x?start=0
Last edit: 09 Sep 2020 16:04 by Aciera.

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09 Sep 2020 17:36 - 09 Sep 2020 17:51 #181472 by Aciera
Replied by Aciera on topic XYYZBC-str config
Regarding the W-"axis": This is not a physical axis but rather a way to command a coordinated move by the physical xyz axis to move the tool along its rotational axis.
For example if you wanted to drill a hole to a depth of -5 with a drillbit with B and/or C at any angle you would command say G01 W-5 and the drillbit would then move along its axis by -5. Then you could do G0 W10 and the bit would be retracted with a rapid move by 10.
So I don't think you would define a W axis in the INI because that would probably do strange things. (MAybe check in the 5axiskins-sim config)
edit: I think I might be wrong there. So you would define it in the INI so you get a DRO for it.

Note that xyz-bc-trt-kins is for a machine where the tilt and rotation is done by the table. You need a kinematic where the B and C movement is done by the spindle. I think 5axiskins is the one you want.
Last edit: 09 Sep 2020 17:51 by Aciera.

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09 Sep 2020 22:41 #181525 by OT-CNC
Replied by OT-CNC on topic XYYZBC-str config
Aciera,

Thank you for the response, I appreciate it.
I will look closer at the 5axiskins.

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10 Sep 2020 06:59 #181562 by Aciera
Replied by Aciera on topic XYYZBC-str config
The simulation config sim.axis.vismach.5axis.bridgemill should give you a good idea to get you started.

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