Alignment prob

hi there !

i m new to lasers and just got my k40.
i got it used and it took some bad hits on transport with dhl i guess,
mirror alignment is driving me crazy.

so i ve bee trying for 2 days, problem is:

the beam goes up in quite an angel from mirr1 to 2.
its like 3cms.
what i guess and read it needs some adjustment of the tube.
i would guess the tube needs to be lifted on the right side if your in front of the laser.

i ll try that tomorrow, please if anybody has another idea, tell me !!
thank you all,

Welcome to the MakerForums @cristl_egg,
The tube should be parallel to the bed before even trying to set the mirrors. You can use a level spirit for that. Only then you can set your mirrors.

Sometime for transportation they use some foam/protection around the tube which could interfere. Look if it is necessary or just transport.

1 Like

@cristl_egg welcome. In case you didn’t see the pinned post there are some alignment guides that should be of some help.


hey, thanks for your answers…
i found out the tube got twisted on transport, twisted it back a bit,
now working…
i didnt know theres a fixed built in mirror in the tube as well and the tube
has to be in the correct rotation angle…
it was just a cm or so, now i m in almost perfect alignment.


How did you find out the tube was twisted out of place? How do you figure out how to twist it back into place?

The rotation of the tube doesn’t matter, unless the tube output isn’t attached properly for some reason. Most likely by rotating the tube he changed the alignment of the tube relative to the plane of gantry / mirrors. It makes things a lot easier for mirror alignment if the tube is level and parallel to that plane. Bigger lasers come with adjustable tube brackets for this purpose. There are also some 3d printable versions that have been designed for the K40.

But if rotating the tube changes the alignment of the tube relative to the plane of the gantry and mirrors, wouldn’t that mean that the rotation does matter? I’m asking because what I’m currently dealing with is a situation where I believe Mirror 1 in my machine is too low and needs to be placed higher with washers or something along those lines. using the tape method on Mirror 2, the spot that burns is lower in the top left position than the bottom left position. Leading me to believe that the mirror is angled on an upward slope. When centering the mark in the bottom left position for Mirror 2 and checking the position of the mark in the top left position, it’s roughly a couple of mm lower. I’ve positioned everything as best I can and checked the levels on the ganrty itself.Mirror 1 is held in place by 2 screws on either side of the bracket, while mirror two is held by 2 screws on one side of it’s bracket. The bracket on Mirror 2 is not level, though. I can’t see the bracket being the source of the angle being off if everything else is level, unless I’m missing something or not looking at this the right way.

Pictures to illustrate the point…

Rotation will only matter if it changes the changes the positioning of the tube output. This is certainly a possibility. I was just saying that the laser tube itself doesn’t care about rotation.

If you put a piece of tape on mirror 1 and the spot is too high then then you either need to move the mirror up with washer shims or shim the tube up at the back bracket.

Regardless of where the laser is hitting mirror 1, at least to a certain extent, you should be able to align it to mirror 2 using the adjustment screws on mirror 1. Get the spots on mirror 2 to line up and see where that spot is relative to the center of mirror 2. If that alignment spot is high then your tube is possibly angled up.

I suggest following one of the alignment guides noted previously in this post.

I initially used the alignment guide to get where I am at this point. I get what you’re saying about the tube. I will have to look at the brackets for the tube to see how I would accomplish shimming the tube if that’s needed. What is the best way to figure that part out if the beam is hitting the center of mirror 1? Looking to see if I can cover an issue before it happens, in case it is a plausible issue (which I think it is).

Just put a piece of tape over mirror 1 like you did for mirrors 2&3

1 Like

Here is the best alignment explanation I have seen so far:


That was actually very helpful and I will be holding on to that video. Thank you for that!

…other reasons to pay attention to rotation is the closeness of the anode to the frame and the orientation of the coolant output to help prevent bubbles.


I remembered the bubbles part when I was dealing with setting up my most recent machine. I believe it was explained in the video and they had the guy in the video rotate the entire machine in a particular way, but I would definitely prefer just orienting the tube itself to solve that issue in a more permenant way.