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

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.)



Attached are my .ini and .hal files.

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).

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...

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.

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??

You have not told Linuxcnc which joints are used on your gantry in your ini file.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.

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.

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

In the master branch (2.8~pre):

e.g., a 0 sequence is not required
Ref: linuxcnc.org/docs/devel/html/config/ini-....html#_home_sequence

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 )