Unless the bearing blocks are loose meaning you can rock them in some direction, I doubt alignment issues would come from the actual slides. Also unless they are warped or bent. A laser doesn’t expose slides to high pressures or extreme speeds or high amounts of debris to cause any damage. I don’t believe that they need to be high quality. What makes you think the linear rails are causing alignment issues?
OK Sorry I have to say I miss lead with the topic/wording.
I think it is the bearing.
The reason I think it is this is because, I get the left rail and gantry squared and after a few uses it is unsquared by an 1/8th.
Well that’s what I would like to do is replace the bearing. But it is something I haven’t done before. My guess is I have to take the gantry off on that one side. Because it looks like the bearing block is connected to the gantry, then I can slide it out of the front end of the machine.
Unless you would happen to know a way for me to test this to make sure 100% that it is the bearing.
“The reason I think it is this is because, I get the left rail and gantry squared and after a few uses it is unsquared by an 1/8th.”
To me this sounds like a belt or loose pulley issue. The gantry (X axis) is attached to the bearing block but those screws are not strong enough to rigidly maintain square. The timing belts on either side maintain square. I would perform the same checks after changing the bearing to prove the problem is resolved.
A lot of lasers are not truly square, I once paid £28k for a 900x600 machine that could not cut true, when I stripped it doen the bearing rails were running off a few mm on both sides, there is wiggle room in the holes in the rails, I aligned mine starting with the left one, made sure it was 90 degrees to the shaft that controlled the y axis, then set the right rail so they were parallel, if i tried to cut a 600x600 square it would “lean” to the right nearly 10mm, once i reset the rails it was within less than 0.2mm, The biggest cause of failure of Recirculating ball bearings is using oil or wd40 to lubricate, these bearings need grease, any supplied from a decent supplier will have grease nipples fitted
Here are a few photos of what I see when I place my square up from the left and right rails to the gantry .
The machine is 55x35 130w Does not cut 1x1 circles smooth at higher speed. But at very slow speeds it does. When I move the gantry by hand when it is off it is not very smooth or as smooth as I think it should be.
You can see how it is not squared from the images, shes a lot better from the right side, a lot off from left side.
I have used this machine for a lot of jobs shes been great but now I have to put a bit of TLC to her.
Looking at your photo’s I’d say your side rails aren’t parallel, the gantry will be swapping between sides trying to stay square to one side or the other and it’ll be putting a lot of strain on the structure as it tries to accommodate the rails getting further apart.
I’d check which one was square to the gantry and loosen the other rail to see if there is enough movement to get it parallel to the first one, if not then you may have to file or re drill the holes to suit.
Also check the bearing blocks for slack on the rails.
Also just in case you don’t know, you can easily check how square the laser is cutting by marking a square box and then measuring diagonally corner to corner, and then the other set of corners should be the same measurement. It doesn’t actually have to be square, a rectangle will still work but a square is also handy for checking calibration so I do both at the same time.