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X/Y Orthogonality

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I have a problem that prints are not orthogonal on the X/Y axis. I created a test object for this, and have found that the x/y axis are not at 90 degrees. I don't have a protractor on me to measure actual angle but my tri-square shows 2 or 3 mm deviation over the 15cm test print. This makes it unsuitable for some of the tasks I have been trying to use it for.

I have attached the test stl I created for this.

Any idea where to start trying to fix this problem?

I have been searching for info for a while and not found much. I was considering rebuilding the whole frame again but wonder if anyone has pointers on things to try before going that far.


Well I finally squared my X and Y axis. It didn't work out quite as expected and the left of the front plate of my Y-axis is now raised off the table about 1mm, but appears to be working properly otherwise.

I thought I would document what I tried in case anyone has feedback that may help me or comes across the same problem.

I tried a few things to square it and they didn't work out quite as expected.

Method 1: Loosen frame, measure align and re-tighten each part of the frame

Using the first instructions of squaring all parts of the frame loosening bolts and re-tightening didn't really help. I had a few problems:
1) Measurement accuracy is difficult
I tried with tape measure, ruler, vernier calipers and string for different parts but I think there was still at least 1mm measurement error just trying to measure parts of the frame on the diagonal in particular. I considered super-gluing sewing pins to the frame to give accurate posts to measure between with string but didn't get around to trying that

2) After aligning everything I can get it to look ok, but then tightening it up and it just goes back to non-orthogonal

Method 2: Adjust just Y-carriage bolts

I then tried the idea of keeping the frame as it was tightened (and potentially unaligned), and just playing with adjusting the Y carriage bolts. But every time I tightened up the nuts on the M8 rod (particularly the rear ones), they would become perpendicular to the rear frame and non-orthogonal to the main frame/x-axis again.

I "think" the problem is that somehow the rear frame that the Y-Axis attaches to is not perpendicular to the main frame. I couldn't see this with measurements (measurement error) but was a hunch.

Method 3 (kind of worked): Space out rear frame

In the end my solution is not great and I wonder what other consequences it may have going forward.

I spaced out the rear frame with some plastic on one side (see attached photos).

This has also resulted in a problem I had earlier where the front right of Y-carriage (that sticks in front of the machine) is now raised about 1mm off the flat surface (See other photos where I have red plastic under it).

I used to have this same Y-axis problem where front left was raised 1mm off the bench and it was causing "grabbing/shuddering" of the bed as it moved in +Y direction. I am not seeing that now so maybe it is ok.

On the A6 the X/Y-Axis can easily be skewed by just moving the front plate right/left.

Maybe the following helps to get an idea what's happening (haven't tried that by myself):

  • move the nozzle to the origin (home) and pull the bed towards you. The nozzle should run perfectly parallel to the bed's edge. If not: the bed is not mounted parallel to the y-axis. That's no problem for printing, but crucial for the next test.
  • If the bed's left edge is perfectly aligned with the y-axis, the front edge should be perfectly aligned with the x-axis. Move the nozzle along the front edge of the bed and see if they're parallel. If not: you have a skewing problem AND an easy way to re-test after trying any solution.

If you are a member of the "Official, Anet, A8R 3D printer Support Group (Inc RepRap Prusa i3 clones)" then there is an instruction document on how to get the XY orthogonal. Link here: https://www.facebook.com/groups/1068531466501015/1698957226791766/

I think this is the document (attached) mastabug was saying, in case you're not a member and can't access it. Also, if you have Marlin firmware, there is a whole section on Bed Skew Compensation with instructions on how to enter the values obtained by printing https://www.thingiverse.com/thing:2563185, but of course getting the frame as square as possible first is probably better.

Hope this helps.

YACS (Yet Another Calibration Square

Those two comments were exactly what I was looking for thanks.

Looking forward to being able to print squares without the need to file them down :-)

Did you fix the frame or use Marlin?

Mine is off by around 0.6mm but can't do anything more to the frame :(