How to. 2 or more motors on one axis. Gantry

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01 Jan 2021 06:10 #193701 by nau

This sounds like the home switch is not connected to the right pin or the homing direction is wrong. I've been caught with similar issues heaps of times...

It is impossible that connection is wrong. I've checked many times that both Y joints connected in right pins. Checked signals and joints status - all match (home-y1 -> joint1, home-y2 -> joint2 and etc).
I had even switched Y home switches (home from Y2 connected to Y1 pin and vice versa) behaviour is same destroying-full (already smashed two sensors).

Home direction - while homing both axis comes in right direction to home switches. All of my axis have sensor connected at same side of motors. And it's works in XYZ mode just perfectly.
Frankly I don't understand one thing: all my sensors is at same side of motors, Z axis configured as -205 to 0 and search vel is positive, X axis 0 to 610 and search vel is NEGATIVE, Y axis is 0 to 1005 but search vel is POSITIVE. Where is a logic?
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01 Jan 2021 07:51 #193705 by rodw


This sounds like the home switch is not connected to the right pin or the homing direction is wrong. I've been caught with similar issues heaps of times...

+1
And yes, when using tandem axis ( two motors for the same axis ) LinuxCNC is always in joint mode until homed, then it switches to world mode.


Tommy, I don't think that is always the case. what happens with your beloved axis if you delete kinstype=both? Joint mode is banned from my Gmocappy config and I never see joints. And why would you bother with joint mode?

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01 Jan 2021 07:59 #193706 by phillc54
Have you tried with a negative latch velocity on JOINT_1 and JOINT_2
HOME_LATCH_VEL = -0.781250

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01 Jan 2021 08:01 #193707 by rodw
Actually, when I think back, I had similar issues and reduced all of the various homing velocities to be super slow (say 10%-20% of whatever you are using now. That lets you see whats going on...

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01 Jan 2021 08:32 #193708 by nau

Have you tried with a negative latch velocity on JOINT_1 and JOINT_2
HOME_LATCH_VEL = -0.781250

I did.
First attempt - "Home switch inactive before start of latch move j=2"
Second attempt - One of the axis had been homed
Third attempt - One more sensor smashed.

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01 Jan 2021 08:44 #193709 by phillc54
When you said earlier that it worked as a 3 axis config did you then try with the other Y axis as the second axis.

If you are smashing sensors then you probably should try mounting them so that cannot happen.

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01 Jan 2021 14:00 #193723 by nau

When you said earlier that it worked as a 3 axis config did you then try with the other Y axis as the second axis.

If you are smashing sensors then you probably should try mounting them so that cannot happen.

You mean swap physically pins from Y1 and Y2 axis and home switches? Yes I've swapped that and with XYZ config it works exactly fine.
Also i've decreased homing velocity to 5 and check what happens more clearly. Both Y drives in right direction hit sensors, stop and then it drives Y2 axis (even if both home sensor is ON).

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01 Jan 2021 14:37 #193725 by Clive S
This is a stab in the dark but I would try to cut and paste the section of the ini file into a text editor then cut and paste it back.

This will guarantee that there is no hidden control codes in the file.

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01 Jan 2021 19:54 #193752 by rodw

When you said earlier that it worked as a 3 axis config did you then try with the other Y axis as the second axis.

If you are smashing sensors then you probably should try mounting them so that cannot happen.

You mean swap physically pins from Y1 and Y2 axis and home switches? Yes I've swapped that and with XYZ config it works exactly fine.
Also i've decreased homing velocity to 5 and check what happens more clearly. Both Y drives in right direction hit sensors, stop and then it drives Y2 axis (even if both home sensor is ON).


Make sure the axis is deliberately skewed before homing at slow speed. What you should see is both axes proceed towards the home switch. The first one there will stop and wait until the other catches up. Then they both should back off the home switch position in unison, move forward to trigger it again, then move to the home offset position. If one side has a direction of travel wrong, or its looking for the incorrect sensor, it will sail past.

I think the only other thing to check is if it is the current version of 2.8 that you are using. If not then upgrade your config.

I think we have reached the limits of what can be done with remote trouble shooting. The unfortunate thing is that there are thousands of machines that are homing correctly so it not Linuxcnc at fault. You need to walk away for a day or two and then come back with fresh eyes, study the homing configuration docs and resolve the issue.

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02 Jan 2021 05:42 #193804 by Trihwangyudi1990
I have 2 Y axis... Now its not work after i edit INI file and HAL file...
Try to move z axis but in screen moving Y1 axis (join 2 in my hal file)
Its swaping... :( :(
This my ini and hal file
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