Looking for new mirrors for your K40 laser machine? Check out Cloudray Laser!

The ultimate K40 mirror alignment guide for your k40 laser cutter equipment is here.

This tutorial contains some tips and ideas for the popular K40 laser machine type, but it may be used to any laser machine on the market because the science behind laser mirror alignment is the same.

90% of laser machine faults are caused by bad alignment of the equipment’s three mirrors, which are not aligning up with each other.

Some of you will have a machine of that 10% with a skewed or non square gantry, but follow through this guide to the end anyway and you will find a link my other guide how to fix gantry problems. But first, you have to identify the problems by following this guide.

Please read through the preface about this guide before you start to avoid doing it wrong.
In my old guide about K40 laser alignment i had numerous examples of readers who skipped some parts and ended up doing the alignment backwards. I know it´s tempting to skip a step or two, but please, read everything and let me know if something is not clear 🙂



This guide will help you align your laser machine to perfection.
It is very important that you follow each step and not jumping around, you will miss important information or details how to identify your machines problems.

Tools you need to complete this alignment
– Any tools needed to adjust the mirrors on your machine.
– Screw drivers, sockets or wrenches to adjust mirror holders.
– Painters tape, labels or paper with adhesive backing for covering the mirrors when test firing.
– In rare occasions, files and drill bits to adjust the holes where mirrors are mounted.
– A pint of beer, wine or a good cup of coffee 😉

How to interpret the results
This guide has a lot of test-firing and looking at the tape/label what the beam does and where it moves. Some parts need you to identify if the beam moves up, down, left or right – when doing this the direction is always as if you remove the tape and hold it in front of you, if the dot has moved right when you look at the tape – you choose right in the sections below.
It does not matter wich way the tape was mounted – just keep it horizontally the same from the mirror to where you look at it.

Adjust the tube if needed so you hit aprox. center on mirror 1.
Also, familiarize with the three adjustment screws on the mirrors which screw moves the mirror in what direction. This will help later in the alignment.

Machine locations and centering the beam
Here is a picture of different position i will refer to in this guide, please have a look to see what is what.
When i mention centering the beam, this has nothing to do with quality or power of your machine, it´s just a easy position to remember. You do not have to be exactly center – keep it close to center so it´s easy to see where the next test-fire will go.

Now, are you ready to align your laser machine? Let´s go!

Part 1 – mirror 1 and 2

This part identifies the movement of mirror 1, moving up and down (from rear to front) of your machine. Follow each step of the instructions and lick on the button corresponding with your problem to find the information how to solve it.

Step 1 – first fire

– Move the gantry to bottom as the first picture shows
– Do a test fire and have a look at the tape on the 2nd mirror.
– Adjust mirror 1 until you hit center on mirror 2 in bottom left position.


Step 2 – upper axis

– Move gantry to top right position
– Do a test fire and have a look at the tape on the 2nd mirror.


By looking at your tape – did your beam move up or down?

Click on the answer below to see the solution.

Your 2nd mirror is too low.
Make sure the bracket holding the mirror is square and not bent.

Remove the two screws holding the bracket, mark the position so you can put it back and add some shims between the bracket and the gantry so the 2nd mirror is lifted some.

Start over with the alignment and re-center the beam in furthest position and adjust more if needed.

A alternative solution is to lower mirror 1, but do not go that route until you tried the tips above first.

Visual example of movement up.
k40 mirror top top


Your 2nd mirror is too high.
Make sure the bracket holding the mirror is square and not bent.
The solution for this problem is to bend down the bracket a bit if its bent up, which is the most common issue. Second solution is to lower 1st mirror but almost never needed.

Start over with the alignment and re-center the beam in furthest position and adjust more if needed.

Visual example of movement down.
k40 mirror top bottom


Sweet, your vertical movement is already aligned. You can now go to the next step.

Visual example of perfect alignment.
k40 mirror center


By looking at your tape – did your beam move left or right?

Click on the answer below to see the solution.

Your 2nd mirror is too far to the left. Loosen the two screws holding the white plate and move it slightly to the right.

Start over with the alignment and re-center the beam in furthest position and adjust more if needed.

Visual example of movement to the left.
k40 mirror left

Your 2nd mirror is too far to the right. Loosen the two screws holding the white plate and move it slightly to the left.

Start over with the alignment and re-center the beam in furthest position and adjust more if needed.

Visual example of movement to the right.
k40 mirror right

Sweet, your horizontal movement is already aligned. You can now go to the next step.

Visual example of perfect alignment.
k40 mirror center


Part 2 – mirror 3 and laser head

Half way there! This part helps you align the laser head in square line with the 2nd mirror. We know the 2nd mirror is in line now since part 1, and now it´s time for the laser head.

Just remember, after each adjustment – re-center the dot on the laser head before test-firing up close to mirror 2 to see where the beam moved.It´s important that you do not touch the alignment at all from part 1.

Step 3 – bottom right

– Move the gantry to bottom right position
– Adjust mirror 2 until you hit center on mirror 3 (hole in the laser head) in bottom right position.


Step 4 – bottom left

– Move the laser head to bottom left and do a test fire and have a look at the tape on the 3rd mirror.


By looking at your tape – did your beam move up or down?

Click on the answer below to see the solution.


Your laser head is too low.
Mark the position of the three screws on the laser head with a pen or small mark, remove one screw at the time and insert a washer between the standoff and the plate holding the laser head.
Doing this will not ruin the location of the plate, confirm with your marking and adjust if it moved.

Start over with the alignment and re-center the beam in furthest position and adjust more if needed.

Visual example of movement up.
k40 mirror top top

Your 2nd mirror is too high.
Make sure the bracket holding the mirror is square and not bent.
The solution for this problem is to bend down the bracket a bit if its bent up, which is the most common issue. Second solution is to lower 1st mirror but almost never needed.

Start over with the alignment and re-center the beam in furthest position and adjust more if needed.

Visual example of movement down.
k40 mirror top bottom


Sweet, your vertical movement is already aligned. You can now go to the next step.

Visual example of perfect alignment.
k40 mirror center

By looking at your tape – did your beam move left or right?

Click on the answer below to see the solution.


Your laser head is too far away from the gantry. Loosen the three screws holding the bracket and move the plate up (if you look at your machine standing in front of it - looking down on the work area). Up - away from you.

Start over with the alignment and re-center the beam in furthest position and adjust more if needed.

Visual example of movement to the left.
k40 mirror left

Your laser head is too close to the gantry. Loosen the three screws holding the bracket and move the plate down (if you look at your machine standing in front of it - looking down on the work area). Down = towards you.

Start over with the alignment and re-center the beam in furthest position and adjust more if needed.

Visual example of movement to the right
k40 mirror right

Sweet, your horizontal movement is already aligned. You can now go to the next step.

Visual example of perfect alignment.
k40 mirror center

Laser head centering

It almost suffices to align the machine in a horizontal and vertical plane. The laser head is the final component. It’s typically not enough to hit the hole in the middle, but it’s close.

The simplest way to do this is to use my tool to cut a piece of 2 mm acrylic or wood, mount it on the laser head, test-fire in each of the four corners, and check the tape to ensure that your beam is hitting the lens well. There is an issue with the corners moving around excessively.
Since you have mastered the mirror alignment, I advise adding little pieces of paper between the mirror and the holder for the laser head in case you need to make any last-minute adjustments.


By all means necessary, you have now aligned your machine. If you’re still having issues, check to see sure the gantry is square, level, and parallel to your bed and machine.
I´m sorry to say it, but if this guide cannot align your machine, it has some bigger issues and a general guide like this will not cover the problems it might have if i want to keep it quick and helpful for 95% of the users.

Feel free to comment below if you have any questions.


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Forums are just mean.. Trying to align and adjust mirror and fix other issues. This is what I get when I test fire (From the board obviously I have another issue.) the beam is curved.. slightly crescent shaped. It’s 3mm wilde as well. This first tap of the test button made that crescent and pin point. Now it’s just doing that weird crescent shape.


I’m exhausted trying to align the mirrors. 3 kids being in the vicinity and a wife wanting her kitchen back.
I cannot get mirrors 1 and 2 to align consistently. For example, I manage to get it aligned in the bottom left, and when I move it back to the home position it’s WAY OFF alignment.
I’ve had the gantry out the machine and that’s square so can only assume the laser is shooting at an angle, being amplified the further I move away from home position??
I really don’t know and just guessing, would be great if someone could help

Haley White

I have spent WAY to long trying to align and center my mirrors. I have watched countless guides. Right now, I have it pretty close.

Mirror one: Good to go
Mirror two: Off by the slightest, approx 1/2mm.
Mirror three: Same, I’m assuming because of Mirror 2.

When I do my test cut, the laser is clearly hitting the wood, its smoking, cutting, just not cutting deep, at all.

So clearly, something is off.

I am going to follow your steps, and see what needs adjusting!

I have been trying to find support via phone, as I need my laser fixed asap, are you available via phone? or if needed, through this chat, today? around 5pm PST. I will follow your steps first, but if I just cant figure out that last tweak, I would be grateful for your assistance!


Very grateful for this guide and thank you for the time you spend helping others. With that being said, I’m having problems with mirror #2 alignment at top left on gantry. The laser is hitting center left. Your guide says it to far left, needs to go to the right. Does it mean to swivel to the right or do I make new holes in the plate for the mirror to entirely move right?


That is my problem. I’ve moved as far right as possible. The plate connecting to the gantry and the mirror on the plate.


Hello again. I thought that I had posted a request for your help via WhatsApp but I don’t see it here. I would be very very grateful if you would be able to aide me because I am nearing a deadline to have this machine working. Thanks


Hi, thanks for a great guide and offering your spare time to help us all.

I have managed to set mirror 1 and 2 perfectly. Mirror 3 is giving me some resistance. Bottom right perfectly centred, Botton left moved around 4mm up. According to the guide, the head is too low, so I made a spacer and lifted the head, but machine went haywire and stopped reading the stoppers and goes past home and hits the edges with some noise.

I removed the spacer and all back to normal, is there any other way to get the head aligned, it does not have any other screws except the ones that fit it to the rail.

Many thanks


Thanks mate, managed to make a metal spacer as I realised the metal was talking to the sensor. Now working properly. Thanks for your response ?


New issue arised. Mirror 1, middle spot on. Mirror 2, middle spot on bottom and top. Mirror 3, middle spot on bottom right and left, and top right. When moving to top left, beam drops around 2mm. Gantry out?


Ok, it’s top left though. So top right perfectly centered, then when moving to top left, drops down about 2mm


Thanks mate, will give that a go. Have not had to make changes to the gantry before, this is my 3rd machine, so going to be a new learning curve ?


Hi – great guide thank you! Just a quick question – just replaced laser tube and mirrors are all out, I’ve been fiddling around with the mirrors and then wondered if it’s critical for the tube to be levelled as well, and is this adding to my headaches if it isn’t! The one I took out had a little piece of rubber stuck to the protective ring around the tube – is it needed to somehow level the tube too?


Excellent , one less thing to worry about. Will need to try again following the instructions. This is what I got initially from moving the lens head around the four points of the bed. Bottom Right missed the hole in the final mirror / lens completely

Last edited 2 years ago by JonR
Mike Godbe

Every other guide I’ve seen discusses adjusting the three screws on the back of each mirror, where yours seems to only discuss moving the plates up and down or left to right to not adjust the direction of the beam, but to adjust the receiving mirror so the beam hits it in the center. Is this right? Doesn’t this assume that the mirrors start at a true 45 degrees and are square to each other (but just out of plane)?

I have tried other guides and made things worse, but now I’m in a situation where I need to zero everything out and start over, and I don’t see how this guide can help with that if there is no discussion of correcting misalignment from the screws.

Am I missing something? Thank you fir making the guide and for making this resource.


How am I supposed to cut out your tool when my machine is out of alignment?


Nope. Mine won’t even cut…I made a big mistake getting this machine without having any kind of technical support and I’ve already wasted too much time trying to figure it out so I guess it’s time to cut my losses and stick to what I already know since this machine has made me seriously doubt my intelligence.


hi HP, I have a problem with my laser alignment, the bottom right is centred the bottom left centred, top right is 3mm below centre and 1mm left, while top left is centred. I don’t really know how to go about this and I need your help urgently because have been on this for like 9days now.


Since every upgrade needs a readjustment, i mostly have a non functioning K40 more than a working one 😀

but looking around one question came up:

Should the Lasertube be close to Mirror 1 or farther away?
Ive seen setups where the tube is almost touching the mirror, some medium distance..
I have mine as far back as possible, what is better?

Have the long 40W,Cloudray holders, Upgraded lens and mirrors and thinking of changing the whole gantry to 2020/2040 profiles and linear rails.


Since the backwards alignment has reducing the risk of optics damage as a reason
a quick trick to reduce damage the classic way:
Get some Aluminum tape (or foil) to use behind the tape you are firing at, since it doesn’t penetrate the aluminum, it saves the mirror being aligned from the glue and paper soot from gathering on the mirror until it is aligned.


I have spent the last 7 days trying to align my K40. I replaced the tube and upgraded the mirrors to the cloudray set up. I even bought a 40.00 reverse laser that you put in the laser head to align it. I followed the above guide exactly and have gotten it close but still off. Included picture. I was trying to do the payed help but its showing not available.


if this post twice I’m sorry I changed computers and my reply isn’t showing on this.
It’s mirrors 1 and 2 that I cant get lined up. I followed the steps above for those. I lowered my mirror and even had to drill out some more to lower it. I went from that big gap down to the smaller gap but can not get it exact. I’m not sure if I should drill it out more to lower it or not.

I installed the new tube and made sure it was level also checked the level of my gantry and the guide bar that mirror 2 runs on and they are both level.

Carlos Pereira

Hi guys!

Top guide but i have one problem.
You guys only test in the bottom, and have a problem in the top.
In the bottom the laser is in the center, but when i test in the top the laser goes to the right. You can see the problem in attach.

Carlos Pereira

Hi there, thanks for the reply.
But can you show me, where you are talking about


Thank you for the awesome effort and your free time to help us to align our K40 lenses!

I am near finish and dont know what is the issue. Dont want to mess again all steps, so if you have another minute of your precious time to take a look and maybe hit suggestion how to solve this final step which bothers me:

As provided in few pictures.
Did everything you wrote in instructions but when my laser head is in top left and bottom left position – laser point (hit) is centered 100% (Mirror 1 and 2 are centered) – conclusion – works fine.


When I move laser head to the far right UP and far right BOTTOM, my hit point is the same (which is good) on both positions BUT FAR RIGHT from center (as on pictures).

What should I do to move that spot to the center when laser head is far up and bottom at right position, and not to screw up whole work?

EDIT: Couldn`t attach more photos, so I upped this 6 photos on permanent image hosting to better describe my issue (if its ok with you). Wisdom: 1 picture worth more than 1000 words :))

Thank you!!!


Last edited 3 years ago by Hrvoje

Thanks. I will try with that option. Will post result here.

chris lewin

just fitted replacement mirrors (Mo) and lens. They are thicker than stock but doesn’t seem to affected alignment too much only needed to adjust mirror 2 slightly. i noticed that the mirror 2 and mount seem to be getting warm since now touching them , Is this normal ? All this was done as my machine seems less powerful not cutting/engraving as normal

chris lewin

Found the problem. Ran the laser and only mirror 2 is getting hot, replaced mirror with original k9 mirror and it didn’t get hot and cutting ability returned to normal. So returned Mo mirrors as faulty and being replaced with Si mirrors

Andy Frost

Thanks for the great article. I was getting stuck on adjusting the mirror 2 bracket, I couldn’t move it any further to the right. I read another post about checking the tube placement. I could see the tube wasn’t aligned with the frame/gantry. I easily adjusted the laser to be straight and that put the laser in the correct range of mirror 2. Just wanted to mention this in case anyone else is chasing their tail like I was.


I did the Alignment and everything is done! But Still i hitting in the front of my laserhead. How do i get it to move to back of the nozzle. Left and right i do with the screws on the right.. But to move forward and backwards?

Last edited 3 years ago by Harold

Hello Sir,
I tried to align the mirror as I saw here.

The first problem was that from tube beam was hitting into the mirror quite low, so I raised mirror 1 about 4mm.

Then it was quite easy to align with mirror 2 but I had also to race mirror 2 now.

Then ofcourse I need to race laser head and I did but beam hits it in a corner, and also at top right corner it is few millimeters to high.

I have put laser head on I angle (raised left side) so beam hits center of lens, for engraving it works fine, but for cutting I can see its cuts on a angle.


Last edited 3 years ago by Renatas

thanks for responding 🙂

I have changed quite a lot, so I will repost the steps I took.

  1. 1 I noticed that the beam from the tube hits the first mirror quite high, so to not mess up with the tube I raised the mirror 1 about 4mm, now it’s dead center.
  2. comment imagecomment image

  1. 2 the main thing from the youtube guide was when align mirror 1 to mirror 2 first align horizontal and vertical to gantry axel witch I did. Moving mirror 2 to top and back to bottom, both test shots were dead center. And also I raised mirror 2 because I raised mirror 1.
  2. comment image

  1. 3 Then it was the turn of mirror 3. I adjusted mirror 2 so it goes parallel with the bottom x-axis and both left test shot meets right test shot dead center than I moved to the top right and top left. The top left was in the same spot as the bottom left and right, but the top right was 2 millimeters too high.
  2. comment image

    I found that I can lift the gantry top right corner with few metal washers which I did but it didn’t make any difference.
    The main problem is that beam from mirror 3 to the lens is hitting in a corner.
    This image shows the laser head raised and regular height shots of the focus lens burn from the bottom of the laser head.
    not raised laser heads lens shot look better, but mirror3 shots are too high.comment image

Last edited 3 years ago by Renatas

Hi ,

I was having a problem in my gantry that was not standing straight in the bed. Took out the gantry and fixed the problem. But know the right side of the gantry does not run smoothly. And when tensioning the left side to tide I won’t run. What is the best way to tension the Y belts


Hey there, I am having an issue aligning my laser after changing my tube. I have went through and aligned it 6 times or so I thought, First couple times I had a shadow. I reset the tube and it appeared center no more shadow. I then adjusted the other 2 mirrors assuming again it was centered on all four corners. On my laser I have a circle frame in front of mirror 1 and mirror 2 so I went off that to set this time and put the tape there? All looked good cleaned mirrors and tried again this time I can not cut through 1/8 wood at even 18 it is a 100w laser with a brand new reci 100w tube.
I am a single mom and was part of the deep freeze in Texas and both my laser tubes cracked with no power of water for days, Bought now 2 tubes first one arrived cracked. I have been down for almost a month now and am running out of ideas. Please help.


Changed my laser head holder. Have good alignment at all positions on the table. But unit will no longer cut with the power that it had prior. I was cutting 6 mm pine at 8mm jog and 18 percent power. Unit now will fail to cut 3mm into same material at given settings.
It extremely frustrating.
Any ideas


How would that happen. Bad alignment on head mirror ?


I have two issues. Beam hits center on laser head mirror. Burn is off center. Mirror was shimmed originally but I changed brackets for the head to one that wasn’t bent from the factory. If you turn the laser head mirror left or right does that effect where it will hit on the lens ? Almost changing the angle of the head mirror?

It’s brand new and I already broke it I have another one I used for like ever. And I bought this one because it was nicer.


It appears that I have gotten the laser fixed and focused. Do you have a suggestion for a new laser head. With screw adjustable head mirror that is short enough to work on the k40.

The lens ended up needing shimmed . It was shimmed when I took it apart. And I would like to be able to just turn screws to adjust it not paper shim it.

Thanks for the help btw.

Your knowledge was excellent

geoff Fischer

I tried to follow your guide but am having problems. Mirror 1 is centered, by mirror 2 I’m getting 3 small holes and by mirror 3 I’m getting nothing. Mirror issue? Laser bad? Laser is pinkish purple when firing but the power is diminishing or very poor for some reason. Only has this like 2 weeks, worked fine out of the box but now this 🙁 any help would be appreciated!

Myrthe Vandendriessche


I do have a similar problem;

  • on the top right of the engraving field, I still have a good engraving, going more down and to the right, the engraving gets weaker and weaker. More or less in the middle of the engraving field I do no longer have any result. I already put my ampères relatively high (up to 60% – as a test, still no optimal results.

I checked the alignement of the mirrors. They are still fine.
but I don’t have a clear dot on my mirror 2 and more or less two circles on my mirror 1.

I added a picture of the test shots on mirror 1 (post-it on top) and 2 (post-it on the bottom of the picture).

Do you know how to fix this?

WhatsApp Image 2021-04-24 at 20.46.50.jpeg
Myrthe Vandendriessche

thanks for your help. I alligned the mirrors again. Mirror 3 was out of line so that’s better now.
But I still have a 2 cirkles to begin with so that’s not ok. Because the cirkles are getting bigger on every mirror.
It seems like the beam is getting splitted or something.
is there a way to check if the tube is damaged other then watching the cirkle?
Can i see something in the tube itself?
It would be really bad if the tube allready died because I barely used the machine.



Thanks for your answer, it really helped me!

Steve Lee

Thanks for these instructions, I was chasing my tail until I found them.

I think I am close just not quite there.

Mirror 1 is in the middle, mirror 1 to mirror 2 is square, mirror 2 is is the middle.

Bottom right is correct, bottom left is correct. But top right is off, 1mm left and 1mm up. Top left is halfway between the placement of the top right and being centred.

Also, when the laser passes the lens, it also comes out to the right by 2mm (opposite side to when the beam enters).

Any advice please?


Steve Lee

Thanks for getting back to me.

Im now even closer but not there yet. I raised the back right by 1, 2 and 3 thick washers. 1 wasn’t enough, 2 brought the top left into line, but 3 made it go out again.

So with two washers, the 1st and 2nd mirrors are aligned and in the middle, bottom left is centre, bottom right is centre, top left is now centre, top right has come down to be level with centre vertically, but 1-2mm to the left.

I have attached a pic, the 3 centre dots are on the right, the off one (top right) is on the left.

Any more advice please? Thanks very much.



Firstly thank you for the guide, have used it myself multiple times, as well as advising others to check it out.

On the current machine I am working on, the everything is spot on as above, except the drift to the left when in the Back Right Corner.

I have identified the bar and coupler (original bed is stripped from this machine, but am unsure what you are referring to move etc.

Are you able to advise further?


Thanks for the great guide, I did everything as instructed but I didn’t get a good result. Namely, the laser does not cut up to the right and it cuts perfectly on other parts. I checked the mirror settings and
Bottom right: centre
Bottom left: centre
Top right: centre
Top left: up from the center by 1mm
I didn’t try to adjust the beam because I will disturb the other sides. What can I do to fix it? Thanks in advance. I Sorry for the bad English.


So I have a perfect dot on my mirrors all where stated. Mirror 3 perfect same dot in the centre

but when I move the mirror 3 to the top left or right the dot is quite off centre for both tests. Does this mean my gantry is off?


had to replace my lens. did your test i had to move my 1st mirror in so the laser tube would be center.(i believe this might be my mistake) continued to line all the other two mirrors up and finally at the head assembly my bottom left mark is dead center but when i move the head to the bottom left it goes up and becomes double

Julia Kosir

So i have all my corners alligned except for my top right. I aligned all my mirrors parallel, not to the center. I also just re aligned my bed to 0.1mm difference on all ends so it is very straight and i raised all the other 3 ends to make the top right lower (as suggested everywhere online) but it did not change where the beam was hitting. I also tried shimming 4x the distance i needed but i still did not make a difference where the beam was hitting so the shimming is clearly not the problem. I do not know what do now. If i align the top left corner and the top right corner, than the bottom left corner hits too low (essentially the same thing as above but reversed), so i am truly confused as to how to fix this problem. Any help would be extremely appreciated as this issue has made me pretty upset.

Julia Kosir

Thank you for the speedy response, it means a lot

Bottom right: centre
Bottom left: centre
Top right: below center
Top left: centre

Attached is a picture showing how the beam hit the tape on the laser head. The middle beam is darker cause all the other 3 sides of the machine hit at about the same spot, but you can see that the top right is sitting too low for some reason

Julia Kosir

Thank you very much for the assistance, I will see how well it cuts as soon as I have the time, and if it is not adequate I will try the above. One last thing. my 30mA Current Meter that came with my k40 (analog version) does not appear to work when the laser is running. I can get it to work if I tap the top but then in a few seconds it stops again. Any idea on how to fix this? I know this is not directly related to mirror alignment but someone else on here may also encounter a similar issue.

Julia Kosir

Also to note, those 4 red dots around the circle are just an indicator for me to see approximately how close I am to the centre (not actua laser burn marks) because my eyesight is a bit poor and I have trouble making out the circle else wise


This is, by far, the easiest tutorial to follow. Thank you for putting so much work into it!
I have a quick question, if you don’t mind. I’m having a hard time aligning mirrors 2 and 3. I need the beam to fire down and left more, but I can’t seem to get the top left and bottom right corners of mirror 2 close enough to the back plate because the screws come apart from the front plate. Am I missing something? Is there a way to remedy this issue? I appreciate any help yours willing to offer.


Nice guide, thanks. Even if everything in K40 regulation is pretty much evident, I am facing problem that is currently breaking my head in two.
I brought home K40 from public workshop for some laser cutting. I noticed that it does not operate at the power it should. After disassembling the head the problem was evident – third mirror (that brings the beam vertically down) and focusing lens should be better replaced.
After receiving both mirror and lens from aliexpress I assembled the head together, but now the beam does not hit anymore into the center of the bottom hole. Putting a piece of paper or two under the third mirror does not help – now the upper edge of the mirror is to be lifted about 1.5 mm to direct the beam vertically down! And such deviation is far from “fine adjustment” term.
I just totally do not know what happened. It worked fine previously. I believe I did not lost any parts nor anything seems to be missing from the assembly. Overall geometry seems to be fine for the first two mirrors, and in fact this have nothing to do with the current prob 🙁
I just can’t figure out… 🙁


Hello! Your guide is great and much appreciated. I have an issue I didn’t see in the comments and previous answers, I am sorry if I missed it. I have aligned my test fires and they line up but when test firing with the head at front right (closest to me, right side) through about halfway up towards the back right, I get no dot. As I get closer to the back right, I start to get the burn mark and at the top right it’s aligned with my back and front left dots fine. But that whole front right quadrant seems to get no power in the test fires as it won’t mark the paper on mirror 3.
I should add that if I repeatedly fire in bursts I may finally get a tiny dot which does seem in the correct place, so it doesn’t seem that the bean is out of place there just very weak
Any ideas on the cause?

Bruce Garoutte

Here is a little trick that I learned on my K40. To help ensure that the thumb screws do not move while tightening the lock nut, I use a pair of 8″ curved Hemostats to hold the thumbscrew. Now, as I tighten the locking nut, I can securely hold the thumb screw and keep it from turning. This really helps cut down on the errors incurred by trying to hold it by hand while tightening. Also, the Hemostats can get in those tight places where my fingers do not like to go.

razvan constantin

First theank you very much for this isntructions .I do all the steps but one i can not get it wright .STEP 3 dont matter what i do the beam move 2 mm up …i try to put something onder to elevate the head but still i get the twoo mm diffrence .Do you please have any ideea what can be .
Kind regards


Hello, I am having an issue aligning my mirrors. I’m stuck on the first step. After I adjust the screws on mirror one so that the laser hits the center of mirror two in the far position, I move mirror two to the near position and test the laser again. There is no change vertically, but horizontally the laser is firing several mm to the left of center. The guide says to adjust the white plate that mirror 2 sits on to correct for this. However, I can only adjust the plate 1-2mm before it is scraping against the side of the frame and prevents the gantry from moving. And, I don’t notice any difference in results when I make this minor adjustment and then start over from the beginning. Is there something else that could be causing my 2nd mirror to be in the wrong spot? And, is it normal to have so little room to work with when moving the white plate?


Thanks for the help. I ended up moving the whole gantry (and consequently mirror 2) as drilling new holes for the first mirror would have been a lot more work. When I moved the gantry as far to the right as the pre-drilled holes allowed, I was able to get everything aligned in a matter of minutes. I’m guessing it had shifted during shipping.


after did all of this and 3rd mirror is centered and i try to cut my wooden piece but unfortunately it is not like before.power is very lower and why is it?

Jacob Smelt

My laser is hitting the edge of the lens how do I fix this please

Jacob Smelt

Thanks I will try this


Thank you for the excellent guide. you made my alignment an easy task to do.


I love you man. 3 days of work and nothing. 30 minutes with your guide and everything is perfect. Thank you very much


Thank you for the mirror alignment instructions. I have my mirrors aligned, but when I start my engraving project, there is a shadow. I’ve had this problem before and fixed it, but I cannot remember how I did it. My mirrors are aligned and clean. Any suggestions?


got a question. in the beginning of the guide it says if the test fire it to low or too high at the second mirror, then the bracket for mirror 2 maybe to low or too high. what about any adjustments to the screws on mirror one. do they ever come into play?
im having an issue where i cant really cut anything on the right hand side of the cutting platform. lens and mirrors are clean. i dont appear to be hitting the inside of the air assist nozzle.


Hello You say to add a shim on the mirror to raise it ?? what is a shim ? how do i do that ?

Thank You


Hi there, first let me say thanks for the articles, very helpful. I have just bought one of these machines and your alignment advice is great for me, the only thing that I am struggling with is the lens adjustment using the tool – would it be possible to add a photo to show the tool in place to help understand the usage?

I am trying to get my machine to cut MDF and acrylic, and so far test pieces show that with the 40w tube I can only cut a maximum of 1mm deep in one pass, and to get any deeper requires many (15+) passes, so am suspecting that something is up with the lens alignment. Of course, I had to follow many of your tips to get the machine to that stage! They are cheap, but you get exactly what you pay for!

Gary hunt

Amazing guide had to shim up second mirror and shim up right side of my tube now my beam on all mirrors are centred cuts like a dream!!!!!!

Ryan Pacheco

How much to have you help me align? I can’t figure it out. Mirror 2 hits center and mirror one is off to the far left and down. About to the rim of the mirror.

Wayne Erney

ha if all mirrors are in alignment but the laser beam is hitting on the inside of the air assist head what is the fix for that?


Have followed Your guide mirror 1-2 hit centre target but not dead, Moving to mirror 2 – laser head, at the bottom right target hit centre at bottom left target hit centre but not dead, moving to top right target hit up to the right. Please help with solutions.


URGENT!!!! in your mirror alignment guide you said we should place mirror 2 at the far end before setting, you now mentioned ADJUST MIRROR 1 UNTIL IT GET TO CENTRE OF MIRROR 2, my question now is, are we to adjust the mirror with the knob behind mirror 1 or adjusting the mirror itself to get the dot to the centre of mirror 2.


After the centring from the bottom left of mirror 1 to mirror 2, moving mirror 2 close to mirror 1 the DOTS are beside each other with the use of the 3 knobs behind mirror 1, in your guide you said we should loosen the mirror 2 and slightly move it to the right and start all Again.
My Question is, DO WE NEED TO UNSCREW THE 3KNOBS TO IT ORIGINAL POSITION before starting allover with the alignment and re-centring.


is there a guide pr can you tell me how to adjust my x axis belts? there are two philips that adjust tension, but i cant tell which way to adjust. im getting curved lines where there should be straight lines. Im very frustrated over something that seems so simple! Thank you


Hi, I have aligned all the mirrors, but nothing comes out of the head. I have placed a small bit of card between the 3rd mirror and the lower lens. There are burn marks on the card, a bit off center but they are there. I just don’t know what to do next. I have polished all the mirrors, turned the lens around so much I now don’t know the correct way, is it the oval face facing up or down. I thing that it must be that somehow the beam is just not hitting the lens center, but how do I adjust that.?…

Bernd Uthoff

Hej HP,
1000-Tak for dit fantastisk fine styke arbejde!, det har sparet mig for mange timers arbejde.
Har det rigtigt godt



Thank you for your work preparing this tutorial.


My 2nd mirror when its far from the first mirror its perfectly in the middle but when it gets close to the first mirror it goes to the upper right corner only for like two and a half millimeters.I wanted to ask if you can tell me a way to solve this problem.and get it perfectly in the middle in both ways.When its close and when its far.i already tried to adjust it but it didn’t work.


I’m centered on step 3 and step 4 but when I put the leaser in home position it’s high right

S.C. Haywire

My stock Blue/White K40 tube hits the first mirror quite low– down by about 4.5mm. I can’t lower the bracket the mirror is mounted on so I assume I need to move the tube itself upwards. The large plastic brackets that hold the tube don’t appear to have any up/down adjustment. Do I unseat the tube from the plastic brackets and place shims under the tube? Or rather, I should ask “What is the correct way to up/down align the tube?”