Working Gantry (2 motors - 1 axis) CNC router w. Mesa 7i76e

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01 Apr 2018 22:21 #108233 by tripwire
I just spend a couple of days searching for config examples or instructions to get a simple XYZ CNC router configured with 2 motors on the Y (gantry) axis.

I began with a config I created using pncconf. Though this config worked, I didn't think I had the 2 Y-axis motors master/slaved because (I now realize) LinuxCNC starts out in "joint" mode in which you can jog the 4 joints (motors) independently. You have to "Home" all the individual joints, then the program switches to "World" mode, which allows you to jog the X, Y and Z axis' "normally" and the 2 Y-axis motors are in sync.

This is probably elementary stuff but it took me a while to figure out. So now someone who searches can find something that should work to start out with. (I'm running LinuxCNC 2.8.0-pre1.)

File Attachment:

File Name: DavesCNCMachine.hal
File Size:12 KB

File Attachment:

File Name: DavesCNCMachine.ini
File Size:4 KB


Attached are my .ini and .hal files.
Attachments:
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01 Apr 2018 23:03 #108238 by rodw
Funny, I had that problem recently but can no longer replicate it. The Axis GUI should detect the axes with a negative homing sequence and refuse to jog it until you press home all. It also raises an error message. For some reason this test was being ignored. Gmoccappy got it right. We put it down to being a config error somewhere but I don't know what.

I posted a barest minimum config for a 7i76e here
forum.linuxcnc.org/47-hal-examples/34072...ranch-gantry-example
If you want to test, You should be able to cut and paste your velocity and acellerations into the Ini file as the way its written, the Geometry settings in the ini file are the only things determining which axis is what. (eg. all of the hal settings refer to joint numbers).

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02 Apr 2018 00:09 #108244 by tripwire
Thanks Rod. I should have said, I did get everything to work! The hal and ini files I posted are for a working config for an X, Y, Z stepper motor system with a 2-motor Y-axis gantry. I'm curious to see if that would work for someone else.

Also, thank you and cncnoob1979 very much! I followed 'noob's "Complete How-To...." and successfully installed mint 18.1, both Live and from the debs. I noticed you offered lots of help on that, thanks!

Limit switches are the next step...

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02 Apr 2018 00:53 #108249 by rodw

tripwire wrote: Also, thank you and cncnoob1979 very much! I followed 'noob's "Complete How-To...." and successfully installed mint 18.1, both Live and from the debs. I noticed you offered lots of help on that, thanks!

Limit switches are the next step...


I think the massive journey I had just before that tutorial was published was one of the things that inspired him to write it. Well he said that in the first post. :)

Limit switches are pretty easy. Just follow the docs on homing configuration which is very well written. Make sure you access the master docs, not 2.7. I have one shared home/limit switch and its important to move the axis of the switch when homing or it will error when it comes out of the homing sequence.

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03 Apr 2018 01:59 #108280 by tripwire
I should clarify that my original post is for a working gantry config *but* I believe I need additional configuration to clean up the homing sequence. With the current config, the gantry joints are synced and jog properly in "world" mode but it seems I can only home the axes in "joint" mode and here, the two gantry joints operate independently.

(To reach my home/limit switch, I've been alternately stepping the two joints by a small amount as to not rack the gantry too much while seeking the home/limit switch. There *has* to be a better way...)

PS: Does anyone know how to edit one's original post??

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03 Apr 2018 02:37 - 03 Apr 2018 02:38 #108283 by rodw
You have not told Linuxcnc which joints are used on your gantry in your ini file.
HOME_SEQUENCE = -1
Refer to the example I linked to earlier in this thread.
I would make sure this is set for every joint (make the Z axis joint = 1 and the Y axis joint= 0 and the two gantry joints -1.
That way the Z axis should home to the top of travel first so it clears any fixtures before Y and Z moves. (you can set Y and Z to the same value and they'll home together but I had a couple of collisions.
Last edit: 03 Apr 2018 02:38 by rodw.
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03 Apr 2018 03:50 #108285 by Todd Zuercher
Actually joints home in the order of their absolute value from 0 up. So the joint(s) you want to home 1st would be 0. Next any joints with a -1 and 1 would home simultaneously, with ones having negative values slaved.
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03 Apr 2018 04:24 #108287 by dgarrett

Actually joints home in the order of their absolute value from 0 up.

In the master branch (2.8~pre):
The initial HOME_SEQUENCE number may be 0, 1 (or -1). The absolute value of sequence numbers must increment by one — skipping sequence numbers is not supported. If a sequence number is omitted, "Home All" homing will stop upon conmpletion of the last valid sequence number.


e.g., a 0 sequence is not required
Ref: linuxcnc.org/docs/devel/html/config/ini-....html#_home_sequence
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23 Jul 2020 18:22 #175561 by ki4swy
Note, The requires 2.8 or newer, It will not work on 2.7.14/2.7.15 ( it is noted this was tested on 2.8 , just confirming it will not work on prior version )

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