Issue with 4'x4' pro build

I am building my machine for the second time. First time everything went together exactly as expected and it was in operation for a few years. We recently moved and I disassembled and am rebuilding it at my new place. I just got done with all the wiring and everything is moving as expected. I was testing all of my limit switches and noticed when I brought the gantry all the way to the front of the machine only one of the switches was being triggered. After looking closer it appears one side of the gantry is 1/16" closer to the front than the other side, which makes sense why only one sensor is being triggered.

I am wondering if there is any advice on how to get this squared up. I’m hoping there is an adjustment I can make that isn’t taking it all apart and starting completely over.


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This is normal; welcome to the club :wink:

You have two options.

  1. Let the motors force the gantry into square with software, either by adjusting the sensor stops or by calibrating it out (I’m not familiar with mach3 enough to know if it has a setting for that; linuxcnc does)

  2. Shim the gantry into square, which means taking it partially apart. I had an old thread where I went through this, but in my case, a 0.006" shim on both ends took out most of the twist… You end up loosening the red vertical plates just enough to shim under one side or the other.

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Well I’m glad its “normal”. I thought about shimming the gantry, but that would still leave one of the two limit switches inaccesible. I’m curious about figuring out how to offset one of the motors on the track with software, will do a little more digging.

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You shim the gantry to take out the twist (or you untwist the bed itself, depending on which one is “off”. You still need the motors to take out the last bit based on the limit switches, shimming the gantry means they’re taking less out.

The gantry should move forward until one of the two switches is hit, then one side moves until the other switch is hit, and now both motors are lined up on their limit switches. If it’s not doing this, something else may be wrong too.

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It’s supposed to do that by itself during the homing process. one side gets triggered, and then it moves the other side until that side’s switch is triggered.

If you hold a piece of steel or something ferrous, does the light on the limit switch do anything? I forget if it comes on of goes off when triggered, but something has it.

what limit switches do you have? I see none in your pictures, and there are no sensor flags either.

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Although as others have said you can shim it, but you don’t need to. The software takes care of squaring on homing.

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Ok, thanks all. I got it figured out. I had to edit the ref all home button and add homing for the slave motor. This “squared” the issue away :slight_smile: