This morning a spent a few hours measuring, inspecting and checking the squareness of my Shapeoko. I will attempt to go through my findings clearly and as concise as possible. However, if you need more information or a different explanation, please let me know.
First I began with checking the corner to corner measurement of the frame. Here are the two measurements: Back Left to Front Right and Back Right to Front Left. I originally thought these two measurements, were close enough, anyone disagree?
I then did a quick test to see if there was a wobbly wheel, so I put my magnetic base with dial gauge on both Y-Plates. This can be seen here: Right Side Y-Plate. Doing this on both Y-Plates, found about the same error between the two, with no large jumps. So I believe my Y-Axis wheels do not have any defects.
After this, I measured the length of each Y-Axis Rail. I took these measurements from the back Y Plate, to the front of the Rail. Here are the photos of each side: Left Side, Right Side. Now my wife helped with these photo’s as the measuring tape would not stay without two hands. The Left Side picture was taken from a slight angle so the photo doesn’t do it justice, but it is slightly over 40.125 Inches, while the right side is right at 40.125 inches. To ensure the dimension of the Y-Plate did not effect these measurements, I measured both sides and each plate was 0.14 inches thick. So as far as I can tell, I have on Y-Rail that is slightly longer. We are talking like 0.2 mm - 0.4 mm longer.
I then wanted to double check my measurements from yesterday. Today this is what I have found:
For some reason, today the measurements between the front and back plates are more agreeable. I then started looking at the squareness of the X-Axis to the Y-Axis. Here is the first photo, which shows the Right Side as seen from the front of the X-Axis. I set a machining square flat to the Y-Plate and as you see there is a slight gap. Which leads us to the second photo, which shows the left side of the X-Axis. The photo did not turn out great, but the left side of that photo is were the Y-Rail sits, and the top of the photo is the back of the machine, this shows a minor gap again.
When Liam mentioned my X-Axis was about 1.2 - 1.4mm out of square I was a little confused as I was pretty thorough with my initial squaring and setup of the machine. So the measurements and what I found today make more sense.
So the question then becomes is it worth trying to perfectly square the X-Axis to the Y-Axis? If so where would you shim? Here is a photo of how I numbered the four locations of the X-Axis, and the screw locations.
Hopefully someone can interpret my photos and help me. I am terrible with this, as it took my like 5 hours to tram my HDZ. I will conclude with some photos of the issue I am experiencing, here is a photo of my measuring the squareness of a piece of MDF I cut out: First Side, here I am holding the machining square flush with this side, and as you can see in this photo, the square does not sit flush with the otherside of the MDF square.
Let me know if I need to clarify anything.