Preparation for the self-construction of a carousel changer

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26 Jun 2022 15:51 - 26 Jun 2022 15:53 #245931 by mgm
I have added an additional "U" axis to my sim, as Joint 4.
I can also bring the U axis home.

When I move it, nothing changes in the preview at U, only DTG counts down the path. The preview moves the travel of the X axis!
I hope I could express myself understandably!

I think that is not what I want.
I want to have an independent axis, which has nothing to do with the X axis! only that it moves in the same plane, it should move the changer.

 
Last edit: 26 Jun 2022 15:53 by mgm.

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26 Jun 2022 16:21 #245932 by andypugh
The preview shows the XYZ point. I don't see how it could show a UVW point. Moving X might be some sort of "best guess" that the preview is doing.

What is your GEOMETRY in the INI?

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26 Jun 2022 16:22 #245933 by mgm
When I move the U axis I always get the error "joint 4 following error".
no matter what I set in the ini!

ini setting:
[AXIS_U]
MAX_VELOCITY = 125
MAX_ACCELERATION = 150
MIN_LIMIT = -0.001
MAX_LIMIT = 500

[JOINT_4]
TYPE = LINEAR
HOME = 0.0
MIN_LIMIT = -0.001
MAX_LIMIT = 500
MAX_VELOCITY = 125.0
MAX_ACCELERATION = 150.0
STEPGEN_MAXVEL = 62.5
STEPGEN_MAXACCEL = 937.5
SCALE = 80
FERROR = 1
MIN_FERROR = .25
HOME_OFFSET = 0
HOME_SEQUENCE = 2

The same settings I have but with the other axes also and there is no problem!
Could this be an error in the simulation in connection with the u axis?

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26 Jun 2022 16:24 #245934 by mgm
Geometry is:
KINEMATICS = trivkins coordinates=XYZYU kinstype=BOTH

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27 Jun 2022 10:56 - 27 Jun 2022 10:57 #245989 by andypugh
GEOMETRY is in the [DISPLAY] section and controls how the preview displays the G-code. If you don't mention U in there then I would expect X to stop moving on U moves.

If your U axis has following errors then it's probably a problem in the HAL.
The system compares motor-position-cmd and motor-position-fb pins for each joint, and if they are different then it flags the error.

Did you copy the HAL sections too, when you added U?
Last edit: 27 Jun 2022 10:57 by andypugh.

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27 Jun 2022 18:34 #246018 by mgm
So the missing entries in the Hal I have now made and the error is gone ...

I have also entered the geometry in the [DISPLAY] section
GEOMETRY = X Y Z
Unfortunately the U axis still moves when I move the U axis.
I have made two pictures.
Once with U = 120 moved and once with U =0
 
 
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28 Jun 2022 09:03 #246064 by andypugh
How much of a problem is this extra movement? Presumably the preview returns to normal when the toolchanger retracts?

I have had a look through the code where I was expecting to see X and U being summed (glcanon.py) but haven't managed to spot it.

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03 Jul 2022 20:11 #246535 by mgm
I have made a sketch so that I can better explain my project.

I have a portal milling machine with X YY Z

I want to be able to move the carousel changer on an axis parallel to X!
In the sketch as axis U drawn.

 

It is not necessary that the U axis moves back to 0.

Is there another possibility to integrate an independent axis which I can move with a G-code command?
It does not have to be displayed visually!

 
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03 Jul 2022 21:55 #246543 by tommylight
Not sure about this, so please double check or wait for someone with more experience to answer:
LinuxCNC can have joints that are not related to axis, i think they can also be homed and positioned independently.
Again, not sure in any of it, just fragments of what i read on this forum.

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04 Jul 2022 08:17 #246562 by andypugh

Is there another possibility to integrate an independent axis which I can move with a G-code command?
It does not have to be displayed visually!
 

Yes, you can have "extrajoints" which are homed like normal joints, but are not connected to axis letters. 
You would then (typically) control them with an M67 command. 


This is only currently available in the development version of LinuxCNC, though. 
linuxcnc.org/docs/devel/html/man/man9/motion.9.html
(look for num_extrajoints) 

You can (almost) use simple_tp (linuxcnc.org/docs/devel/html/man/man9/simple_tp.9.html) in 2.8 but that doesn't know how to home, so is probably more trouble than it is worth. 
 
The following user(s) said Thank You: tommylight

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