eBay Chinese CO2 Laser Cutter & Engraver - Squaring and Alignment 

I do not know, but I would think that aligning the second mirror close to the laser, then at the opposite end would be much more precise than measuring against the sheet metal. If the laser burns a hole in the tape in the same spot at both ends, it's aligned. It's all based on where that first mirror is pointing. I am only guessing.

Yes, bring out the Geekdom, laser-measure it ! This is very handy, i've ordered a set square now, thanks :)

This has to be the best video for metric measurement i have seen for a while. 1/28th? Thanks for the video though!

Actually, if that first order mirror points the beam parallel to the Y axis of the gantry, then it doesn't matter if it's square with the case. That second order mirror adjusts left and right so you can get it in the center of the beam once the beam is parallel to the Y axis. But the issue I'm having is that the anodized x axis bar that carries the laser head left and right, is not 90 degrees to the y axis bars. So far, I don't see an adjustment to square it. Of course I could skew my file to make a perfect part but I'd hate to have to do that for every part I cut. Do you know of a good way to get the x bar a perfect 90 degrees to the y bars?

I just got a k40 and noticed that when I slide the y axis of the gantry it seems to have a lot of friction especially compared to the x axis. It seems to be from the metal rail on the left side. There is an audible grind when I move it. Would lubricating the rail fix this or could it be the belts?

I'm many hours into a confusing problem. On my 100W china laser, the X axis does not cut at a 90 degree to the Y axis. My gantry is true and square. When I move the head on the Y axis front to back it stays straight. When I move my X left to right, it measures a half inch different for left to right. In other words, from the front gantry rail to the X beam, it can be 5 inches from rail to beam, and on the other side it will be 5.5 inches. I don't see any adjustments? When I tied to shim the rail end it binds in the Y rails. It does a great job unless I need a square cut or a perfect circle, not other things you can't notice its off.

Seems funny to be squaring to the side. How do you know that is level and square.?

Okay I have a question, I have a k40 I updated the exhaust port and hade to take out the gantry and when I put it back in the mirrors won’t line up. The primary and secondary will until I move the secondary back to the other end and it’s so far off it’s. It even on a sheet of paper. I’ve tried everything and I’m so frustrated I want to just sell it. How can I fix this problem ? Please help.

I've perfect Y axis alignment. I fight with X axis alignment of the 2nd mirror aligning with the laserhead along the X axis. What are the square mechanical actions to align the moving gantry's alignment? Thank you!

Instead of worrying about the gantry being square to the sheet metal, couldn’t you reposition the first order mirror so that it casts the beam parallel to the y axis rail of the gantry?

After getting mirror 1,2 and 3 perfectly aligned, i perform the test at all four corners to see if they all hit the same place. However, only the top right hand corner of the machine is not aligned, all three other corners are perfectly aligned. Any idea what could be causing this problem?

apparently the huge waste of a vent that sticks out half way into the bed area is so wide that I cant get the gantry far enough over to align it square with the laser. I'm a woodworker and this is out of my element. Wish you were near as I would pay you to fix this...

wouldn't it help just to get Adjustable brackets for the tube and alignm the tube with the rail? surely non of them rest should matter then should it? if you can align the tube parallel with the direction the x rail moves.

I say that because I’ve got a 100 watt 3500 dollar Chinese laser and the metal box is not square with itself

It’s not as important that the carriage is square to the box just the frame

My K40 gantry is spot welded to the bottom sheet metal at the 4 corners, not bolted. :(

You aren't going to believe this, I didn't at first and I saw it with my own eyes. I destroyed the second mirror while realigning because I apparently had the tape touching while doing the test fires and ended up noticeably scuffing it, plus it had a black mark in one spot that wouldn't come off. While searching for the best type of mirrors, (Si,Mo etc.) I saw a post that mentioned using metal (not the glass or ceramic) hard drive platters because of their mirror finish. I had a few bad drives waiting to be scrapped, so I said what the hell and tried it. I placed tape on the platter to protect it from scuffing and used my Harbor Freight hole punch (3/4") and my press as the first try, but it looked slightly concave to me, so I used a hole saw on the second one and it looked perfectly flat. I swapped the mirror in the head with the second mirror and proceeded to test the platter cutout from the hole saw in the head at 4ma. I grabbed a wood ruler for a quick test and it left a burn mark about as good as the original lens. Just for the hell of it, I thought I would try the piece I punched out AND ABOUT FREAKED OUT! It left a much smaller hole that punched right through the wood ruler and out the other side! I repeated the test to be sure and was in shock at this point. I wanted to see how each mirror performed at 5ma, 10mm/s with 1/4" cast acrylic. The punched out platter mirror went just past the midway point while both the flat and original mirror were just under the midway point. I haven't added air assist yet and can cut 1/4" acrylic clean through at 16-17ma at 5mm/s. Not sure if that's good or not since I'm new to this.

Squaring to flimsy sheet metal is a joke in itself. Majoring in minor things.