Operator Safety Switches

Hello all,

My shop recently purchased one of your MR-1 Gantry systems and we are trying to figure out how to wire in operator safety switches, like a light curtain, to protect an operator without sending a “E-Stop Signal” that kills the whole machine. Has anyone had any experience with wiring in extra safeties to the MR-1 system?

Welcome to the forum! I’ve moved your post to the MR1 category where it will get a more focused response.

I dont know a ton about the internal system, but I dont think this all runs on what would be considered a “safety PLC” so you might struggle doing a light curtain in a legit safe method.

If you have the full cabinet, I assume you could put a lock on the door and keep operators out while its running. Some how tie it to the power on the spindle.

Thanks for the reply! We are using the system to cut a piece of plastic off of an injection molded component. So, we were hoping to wire in a light curtain where the door is so that we could pop parts in and out with ease. The machine does not shut off when the doors are opened so we are not sure how to wire it.

And you don’t want to use E-Stop because it resets the machine?

As @maisonvi pointed out, this is not a robust controller with recoverable safety interlocks.

I think you’d have to do some rewiring as the source code for the controller isn’t something that can be modified. I would put an open door sensor switch to turn off the enables on the stepper drivers and to also control a relay to turn off the Spindle power.

You could also hook the light curtain to an input on the PC and have it “press” the cycle pause button. not sure how reliable it would be but could be an option. Also cant remember if the pause button is also the start button. That could create issues with this option unless you are good with computers.

True, but since the controller is a GRBL controller, which streams several G-Code instructions, the Pause may not really pause right away so can’t be relied on as a Safety interlock.

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If the controller is a GRBL controller, then why isn’t the firmware source code available for download and modification?

Because they customized it for their purposes and made no claim about Open Source or even that it’s GRBL.


If there is any GRBL code in their firmware, Langmuir is legally obligated to share it. The GPL license automatically sticks to any derivative software.

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Is this what you are looking for?

That’s the idea, but I couldn’t find anything in there supporting MR1. The last push appears to add the Crossfire XR.

There is an MR branch. But the whole repository looks stale.

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Hello MTUHusky, My company recently purchased an MR-1 and asked me to integrate an AB interlock for the doors. Did you ever get any assistance from Langmuir on how to wire a safety circuit into their system?

I’m unsure if the Cutcontrol program will like the stopping of the program. The doors require being opened for a hundred reasons. I believe it will lose its position in the G code. We have some G Code rocket scientists here on the forum. Maybe they can chime in?

An example is removing chip debris from the part, opening the door, and screwing up the almost-finished part.

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If the switch was wired to signal and arduino to send a quick series of commands to the pc via USB it might work without too much hinderance. Program the arduino macro to pause the program (Spacebar). Then follow up with triggering an AFK bot to trigger the touch screen and stop the spindle.
A pretty convoluted way to get there, but I think it would work if you had to have something in place. I’m pretty sure you’d have to have another piece or two to make the whole loop work properly, but I haven’t really put a pencil to it yet.

Once the new CC update comes around and we have the ability to start on a line of a program it wouldn’t be as troublesome to have the machine go into a full E-stop status. The downside there would be homing the machine back out and trusting the limit switches will maintain your home position to your work coordinate. I’d definitely recommend upgrading the limit switches anyway, and this would be as good a reason as any… right? That’s what I’m telling my wife anyway :rofl:

Tie into one of the limit switches? That’ll stop it. Also require rehoming and cause headaches, but so will an E-stop.