BLTouch one side too high - how do I square the printer?

I’ve seen a number of threads on this issue but I have been unsuccessful in fixing my problem.

The problem is, the BLTouch auto-leveling reads that the left side is about 0.4 mm higher than the center and ~0.2mm too low on the right side. Predictably, a test print reveals that nothing sticks on the left but is really squished close on the right.

I read this topic The left side is too close, the right side is too high (or the contrary) which makes me believe that my printer is not square. Unfortunately it doesn’t mention any method to actually square it so I have no idea if it’s done right. I used a speed square to ensure the towers are square with my table (along the x axis), and then I used it to ensure they’re 90 degrees in respect to the frame (along the y axis).

I do have the Gulfcoast Robotics Z-brace (https://www.amazon.com/Gulfcoast-Robotics-Z-Brace-Duplicator-Printers/dp/B07B3X1XH8) and I used it to square the towers perfectly along the y axis.

Also, I used these bars to ensure the x-axis is level (https://www.thingiverse.com/thing:1138928).

Any help would be greatly appreciated. I’m running out of hairs to pull out :slight_smile:

This may help:

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This may or may not help.
I had the same issues with mine and it was quite some time before I worked out what was causing it.
The issue is a very small twist in the X-Axis rails causing a slight rotation of the carriage as the head moves from the left to the right.
Because the BLTouch sits forward of the nozzle, the amount of vertical movement by the BLTouch is greater than that of the nozzle.
Most people, myself included, level the bed to take out the slight movement up or down of the nozzle, but the extra travel by the BLTouch cannot be taken into account.
I found by using the non scientific method of using a leaver and twisting in the opposite direction worked well.
The following link is to a very short video I made on this problem for another maker.:

Hope this helps you out.

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I have added your explanation and video to the Troubleshooting part, as it is a common issue and you explain it well.

Ray, this has to be my problem. It’s the only thing that makes sense after checking everything else. Thank you so much for pointing it out.

I am a little unclear on how to fix it though. Your video was helpful in explaining the issue but I don’t fully understand the solution. I think you mentioned using a shifter but I’m not sure what that is. Can you translate to American please? :stuck_out_tongue: :cowboy_hat_face: :gun: (edit: I think a shifter is a wrench)

I’m not sure where exactly to put the lever (I assume a screwdriver would do?) and apply pressure. I would assume directly between the X axis rails, but your video seems to focus more on the motor bracket (this part). Clarification would be greatly appreciated!!

In this case yes a shifter is as I understand it a wrench, and adjustable tool for undoing or fastening nuts :slight_smile:
I use it in this case as a leaver to twist the mounting frame on the right side.
The twist is caused by the sheet metal bracket on the right side, so I apply the adjusting twist there.
The direction you need to twist it depends on if your printing high or low on the right side.
If your printing high like mine was, then you need to twist it back rotating down when attaching the shifter to the horizontal surface of the bracket as close as practical to the side where the X-axis rails are attached, in my case I came up from the bottom at the back.
Alternatively, a long large screw driver can be inserted through the x-axis rails from the front and rotated up from the front.
Keep in mind, you are only making a very small adjustment here, so start out with very small amounts of twist pressure and test, is it is still printing too high, twist it a bit more.
This is a trial and error approach but the amount of error is most likely going to be different for each printer, It is better to try 5 times than to overshoot and go the other way and have the nozzle digging into the bed or the left side printing too high.

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I think your should also look at this:

Did you mean vertical here? I don’t have any horizontal surfaces other than the very top of the bracket…

I hate to ask as you’ve been so helpful already, but can you just upload a picture of how you attached the shifter? I am about ready to office-space this thing into a million pieces…