I’m a newbie in the middle of an LR3 build. After adding the Y rail, I noticed that the gantry was not even with the edge of my table. It’s far enough that if I flex it to compensate, it jumps off the Y rail. I purchased the whole kit from the store including the printed parts. I made sure all of the affected bolts/screws were tight (but not too tight) and parts did not have gaps. So, that’s wheel brackets to YZ plate, YZ plate to linear rails, linear rails to XZ plate, XZ plate to rail brackets. The toe to heel difference is 3mm (router side of the beam is further away). But, I think it’s amplified because the back side on the Y rail needs to come in, but the front side needs to come out. So, I have somewhat of a parallelogram. I also made sure that the top of the printed parts on the ends of the beam are facing out. Some of them are smoother than others, so I thought about swapping the one with another. I was checking for square against the linear rails to the top tube. The MDF on the table is square.
Could be that the tubes are extending slightly past the end braces and are contacting the XZ plates. The tubes should be retracted a mm or so inside the braces, especially the bottom ones.
Also try loosening the end braces and squaring the tubes to the XZ plates .
There also may be a “twist “ in the gantry, try laying it against a flat surface to check.
The far side seems to have other issues. I think it’s due to the surface of the printed part. I’m going to take it off and see if there’s a spot like this (photo from the same part) against the XZ plate. I think there is a small gap but it’s hard to see. If there is, I’ll remove the bump and try again.
Also, just to make sure we check the obvious, check your square. If you have a really straight edge, you can use it to mark a line or dot, flip it over, and make sure the line/dots are still showing square.
I had trouble with mine, but I had printed plates and they warped. I ended up adding a small cutting from a yogurt cup to shim one of the screws and it is very square now.
This is resolved. I replaced the printed part with a spare and it squared up nicely. The instructions say to put the top side against the XZ plate but that side had bumps so it didnt go all the way against the plate. The part there now is the bottom side against the XZ plate but that surface is very uniform.
It didn’t help that it’s difficult to measure squareness. My original method was somewhat flawed because if you’re looking at even a slight angle, the results are incorrect. At least now, its hitting the Y belt blocks on both sides at the same time.
