See this link for how to make your homing switches work as limit switches also. I learned this from Tim just a few minutes ago. Just remember if this works it is only on three points. You need an additional switch for the other X and Y direction and maybe Z depending on your confidence in not running the Z off the lower end of your machine.
1 Like
Sounds reasonable, thanks @dtilton71 - I’m still new to this, learning a lot as I go.
Can you clarify how homing helps bit changes? For example, it took me a while to figure out that bit changes require separate files in Carbide Motion. Once I got that down, I currently finish a rough pass, swap bits, then use the original Z-axis reference to zero ONLY the z-axis with the new smaller bit.
How does Homing help with that?
And thanks @Bonch, I’ll check that out. I’m reasonably sure I won’t be running off the edge of the machine anytime soon, but I’d certainly prefer to know that the SO3 will know what to do in the worst-case!
Yes I beat the hell out of my machine on the end. I finally installed an emergency cutoff switch. Now that I have learned how things work it is much better. I am now in the process of installing hall effect switches on all 3 axis both high and low to make sure I avoid doing any damage should I not be watching and something go wrong.
With homing on you will retain your position even if you have to power down. Not usually necessary, but say you have an e-stop wired and engage it for whatever reason, the power to the router and the controller will be shut off. Without homing you would lose your work position. With homing, you can turn the machine back on, re-home to set the machine position, and your work position will be retained and you can go back to running your job.
Homing is essential when you have a tool measure probe mounted at a know location ala the 883.
Useful to hear, thanks again everyone.
I got a Triquerta (sp?) probe, which I haven’t used yet, so I’m hoping that’s a nice way to do the tool setup, alongside the homing benefits you all have helped me understand here.
You can set “hard limits” to use the homing switches as limit switches, and then “soft limits” to prevent travel past your programmed max X,Y, and Z. My XXL will alarm and stop if it exceeds limits in any of the six directions (-X,+X,-Y,+Y,-Z,+Z). Three of those limits are “hard” (the homing switches) and three are “soft” (max allowed travel away from homing switches, as set in GRBL parameters).
Not at the machine at the moment so I can’t give more specific details. But homing, hard limits, and soft limits all seem to work on my XXL.
awesome @mpfreivald – the link @Bonch posted included the code line: $21=1 (hard limits, bool)
Did you use that, or some other setup format? Would love to hear, whenever you get back to the machine, thanks!
Still not at the machine, but @WillAdams posted a link upthread that has what you need:
Specifically, $21 turns on hard limits, $20 turns on soft limits, and $130 through $132 set the max travel used by the soft limits – again as best as I recall.
You can use the MDI interface on whatever control software you are using to query and set the GRBL parameters and generally “talk to” GRBL. I’ve done this on both my Nomad Pro and my XXL using Carbide Motion, Universal Gcode Sender, and GRBLweb – all of which have their pluses and minuses. Carbide Motion for example requires you to set some things like the table X and Y in the software GUI itself, not just in GRBL (GRBL is the software that runs on the Arduino based microcontroller on the hardware board that directly controls your machine).
1 Like
So I followed @ApolloCrowe directions and enabled the setting for homing on my XXL and set the table X and Y to 850 each. I go to the jog function and click to home. and get the following:
Here are my settings:
So, how do I get my machine to home? Any help is appreciated…thx!
Heres the link to the process for activating Homing in GRBL:
http://docs.carbide3d.com/article/67-shapeoko-3-limit-switch-installation
At the bottom of the article you will see how to enter $22=1 on the MDI line.
That did the trick! I tried doing my first homing operation and got an error right away “Limit Switch Hit”. Found out my Z homing switch was bad. Fortunately I had an extra and replaced it. Homes like a champ now.
Now that question is…How the heck do I use them now? I’ve read on the wiki about it, but it’s kind of confusing about how to actually implement it. It seems to me that it would be awesome to use to set a precise zero every time for a jig to hold plaques that I need to machine the same operation over and ovedr again.
Thx again! 
Actually I spoke too soon… when opening the jog menu CM says to home the machine. I click the button, it starts to go, them when it’s almost all the way to the switches limit, it stops and hangs.
If I turn off everything and restart CM (with the cutting head still near the home limits), go to jog, tell it to home, then it works right.
It’s almost it doesn’t like how big my table is and wont home when it’s furthest away from the limit switches.
Any thoughts?
I suspect the initial odd Homing behavior has gone away, and your getting used to the Rapid Positioning options that come with the homing feature.
Here are the steps to take otherwise:
Cycle power, RE-establish SB connection and re-open Carbide Motion.
Update your CM.
You did adjust your table X Y size? 430Y and 850X for the XL .
850X x 850Y for the XXL.
With the power off, can you move your gantries smoothly?
Pulley set screws are on the flat of the stepper shafts and tight?
Is there a way to “permanently” set the “Has Homing” parameter? It works for me, thanks for the help, but I have to reset it to “true” every time I restart the app.
@cobalt60 the command $22=1 set it permanently for me.
@ApolloCrowe the strange homing behavior has not changed. The Z axis looks to home properly; as the gantry travels to the back and the X moves to the right, the Z will move up to the homing switch and then back off slightly (which is, I suspect, correct behavior). Once the gantry moves toward the back of the machine, both the X and Y stop short of the limit, never touching off the switches. Then CM just sits there and waits. Here’s a video of what happens:
I can, after the failed homing attempt (without moving anything), close CM, switch power off my XXL, power back on, run CM, connect my XXL, jog and home; then homing works. It’s always the first homing attempt after sitting a while off that fails.
Setting the table size in the Carbide Motion settings is not the only place you have to set the table size.
Did you set your table size in the GRBL settings via the MDI? You need to set $130=850 and $131=850 for the XXL.
3 Likes
@dtilton71 I think that did it! I’ll try again later when I’ve got more time to putz with it, but it seems to be working now. Thanks man!!
Now does anyone have a class on WCS? LOL!
Tim Foreman wrote up a nice bit for the wiki:
http://www.shapeoko.com/wiki/index.php/G-Code#Using_the_Work_Coordinate_Systems
WCS other than G 54 is not presently supported in carbide motion. I know Rob is working on it