Aligning mirrors on K40 laser

I am having problems with lining my mirrors on my k40, i could have 400 pints a walk a better straight line. I have watched hours of youtube videos on how to do this step by step and also spent hours on even trying it myself. And im at the point of chucking it down the garden. Can some please help , Im at the stage now of paying someone to come and do it for me. I have spoken to a number of companies and a lot cant or wont deal with K40’s. Please can some help before i lose my marbles

It will be easier to get help if you describe the problem more precisely, without hyperbole. Post pictures showing the problem or problems. You’ll need to be patient; there are people here who can help you diagnose problems, but it’s also quite likely it will take a while. When folks try to help, make sure to answer all questions they ask fully and clearly. We are hobbyists who help each other, so you “pay” for help here by being patient, clear, and complete, and later helping others with what you have learned. :slight_smile:


I’m sorry Michael, I will look at posting pictures but I feel they wont help with the problem because the pictures wont show what the laser are not doing because the first one is way of level so you can even see where the laser is going

  1. Are you following any type of guide for the alignment?

Post a target on each mirror and laser mark it with a test fire. Label the marked targets, take photos and post them here.

1 Like

@shorty, it might be worth your time to read this section from our FAQ on how to get good help here on Maker Forums — and really, anywhere else on the internet, or even off the internet!

How to ask for help

Paul Stoffregen, of Teensy fame, wrote How to get technical help from strangers on the Internet. Please read it before asking for help, here on Maker Forums, or on any other forum. From his summary:

  1. Good first impression ⇒ Humans will want to help
  2. Explain context ⇒ Humans will understand your needs
  3. Share details ⇒ Humans will be able to help

Right now, what I am seeing is “I want help but I won’t actually give you information about what is wrong, so you have to guess what I’m asking for” which doesn’t make it easy to help. So if you want help, please give clear and complete answers about what is wrong, and about what you have done.

1 Like

You might have to loosen and move the mounts for the mirrors and/or head. I could never get the alignment even close until I shifted the second mirror to left, and the head forward a little. The beam has to hit the mirror pretty squarely or you will be in alignment h3ll. Once I moved the mounts, and squared everything up, alignment went relatively smooth.

Also, I use 3d printed alignment jigs that take little paper targets which also makes the process a little easier. I found them on Thingiverse, made by, but I cannot locate them at the moment. I can print you up a set if you want.


Hey @Shorty how did you go with what Donkjr asked?

First time aligning the mirrors (for a novice like us) is a huge pain in the butt but once its done the laser is quite simple to use. You just need to take your time doing the alignment and work on one mirror at a time, personally I found using post it notes worked best for me.

Also with the K40 there is some other things you should take care of before using such as checking (and most likely redoing) the wiring in the fan unit and removing the paint for the earth point. But check out the “Getting Started” section for the K40 in the forum as it has some awesome guides and info.


If you think the first mirror is off, first put a post-it over the hole between rear laser compartment and front XY compartment. Then put a post-it on the second mirror and move the carriage all the way to the back. Do a test burn, move it a few inches towards the front, and repeat. Do this a few times and you’ll be able to see where the beam is going and correct the first mirror.

Don’t expect to get it all correct on the first pass through - get it approximately right, so at least the beam hits the 3rd mirror, then repeat the setup procedure 2-3 times getting closer on each go.


Do take care with the tests. When you’re repeating them over and over again it’s easy to start skipping safety procedures and forget that there’s an invisible beam that can destroy your eye before you feel it.


These the ones you are talking about?


Yup, those are the ones, I had k40 in my search…thx


This is the best video I have found.


@Seank Definitely! Good call. It’s been recommended enough times here that it is now referenced in K40 initial setup and regular maintenance along with two PDF guides for those who prefer written material. :relaxed:

1 Like

I’m able to adjust the mirrors, but I think I’m way to far away to help.
And of course there is no payment needed !