Laser tube noticeably mounted askew in cabinet

I have just received my new k40 today, first thing I did was check the laser tube was not smashed, it seems fine but I noticed it was not mounted straight In the cabinet. I would have thought this would have a knock-on effect to the mirrors and the gantry? The gantry looks askew too.

Later addition:

I ended up having to take the gantry out anyway because I noticed the y-axis beam was nearly 1cm lower on the right hand side, turns out on the right hand bracket the wheel had slipped down beneath its rolling rail and over the belt. Good job I didn’t try it first.

I would proceed with setting up and testing the machine before concluding the mounting is a problem.

1 Like

Welcome to the maker forum @Uncle_Pipe .

well you are not the first one, unfortunately.

What you want before you go for mirrors alignement, is to have the tube parallel to your X axis. then only do your alignement as square as possible. a good initial setup is better than a long chasing.


Ok will do, thanks.

1 Like

Thank you.

The orientation of the tube doesn’t need to be super precise. Just don’t trap any air bubbles and if you can hit mirror #1 somewhere close to the center, it’s usually good enough.

However, what is very important is that X is square to Y.

You can move the left and right side of the gantry independently if you loosen the coupler/spider in the front right corner.


A correct alignment requires all parts in all three dimensions to be ‘square’ with each other, including the tube. Just because you can hit the mirror doesn’t mean you can align it properly.

I thought air bubbles are usually handled by rotating the tube in it’s holder so outgoing coolant is going up.

How much horizontal latitude is there on m1?


Mirror #1 doesn’t move.

If you remove mirror #1 and make the tube point directly at mirror #2, then the angle of the tube would matter. But with mirror #1 in place, the angle of the beam which heads towards mirror #2 can be adjusted with mirror #1.

The #1 to #2 beam segment has to be parallel with Y because mirror #2 moves along Y.

And the #2 to #3 beam segment has to be parallel with X, because mirror #3 moves along X.

X has to be square to Y, because you’re using a Cartesian coordinate system.

Now, the caveat is that you have to hit mirror #3 at the correct height in order for the downwards reflected beam to be in the center of the lens tube. If you can’t move the head or mirror #3 up/down, you have to move the tube up/down. So, there is a point in having height-adjustable tube mounts.

(Mirror #3 can slightly nudged in/out by adjusting all three screws by the same amount.)

Yes, I was talking about comically weird angles. Like, the back being 10 cm higher than the front.

If it’s straight-ish and the outlet from the water cooling tube is pointing up, the bubbles will pushed along.

1 Like

I usually find that some bubbles are always trapped by the bends and edges in the water path - even with the exit tube upwards - unless I tilt the entire box by about 10 degrees up on the left, until they’ve all moved into the pump tubing.

If I understand correctly, small bubbles that do not touch the inner surface that is being cooled are immaterial. If the tube is level, I would expect air bubbles that impact cooling capacity should produce enough drag on current flow that they would ultimately be moved to the exit port.

Does that rule of thumb make sense to those here with lots of experience?

1 Like

You’re almost certainly right. I’m just satisfying an obsessive desire to get them ALL out : )

1 Like

Just to be clear, what has to point up is the circled outlet:

Cross section of the problematic area:

The short piece of tubing and the cooling ring for the output mirror are fairly restricted. Air bubbles will just pushed through those sections no matter what.

1 Like

Rotationally the laser is ok, but the tube is not parallel with the x-axis.

As long as it hits near the center of the first mirror, you can adjust the mirror for the aligned exit path, within the range of adjustment of the mirror stage.

Does the tube holder mounted correctly or could have it moved ?

How much space to play with do you have within the tube holder ? it’s not unusual to put some padding there to correct the tube alignement.
by how much is it off ? (maybe some photos if you could)