Mirror alignment – no more sweat and tears

Mirror alignment is the action many of us fear the most, looking at videos and reading guides and after two weeks your mirrors are still not aligned.

Many of the guides and how to´s forget the most important part of aligning, that the pieces you try to align actually are aligned themselves.

I have therefore made this guide in three parts, with three steps in each part., how you can see if your gantry is not level, or not square.
This is the most common problem, users try to align a gantry out of square/level. It can´t be done.

Before starting

Before moving the laser head or gantry, remove the cable connector from the stepper motors to prevent current going back to the controller and damaging it.
Close the lid before test-firing the laser and make sure the tape do not catch fire.

Part 1 – identifying your machines problems

Until we start aligning the mirrors, we need to know how the machine behaves and if it´s crooked or not level at any axis.
Without this any alignment you do is wasted time.

Step 1 – preparations

You need some tape, pen and paper to take notes and a clean mind before starting this. Lock up the wife/husband/kids/dog and do this with no stress and calm around you ;)


Step 2 – first fire

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


Step 3 – moving on

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

You have now done the first three tests to determinate how to align your machine properly.
Depending on how the dot moved when you moved the gantry, you have different kinds of problems. However the dot moved you can never ever align that with the mirrors.

– If the dot has moved up or down
Your gantry isn´t level, it´s leaning.
If the dot hits above center, top left part of the gantry has to come up the same amount
If the dot hits below center, top left part of the gantry has to come down, easiest by shimming the other side.

– If the dot has moved left or right
Your gantry is not square, loosen the bolts and square it up.

That´s it for part 1
Take notes or save the tape-pieces on a bigger piece of paper.
In a later part we will analyze the test firing to identify whats up with the machine and how to fix it.

Part 2 – welcome to the next 20 minutes of pain and words not written in the bible ;)

It´s important that you do not touch the alignment at all from part 1.

Step 1 – the furthest position

– Move laser head to top right position
– Do a test fire and have a look at the tape on the mirror, adjust mirror 2 until you hit center.


Step 2 – back again

– Move laser head to top left position
– Do a test fire and have a look at the tape on the mirror.

If the dot moved left-right – the gantry is not square
If the dot moved up-down – the gantry is not level on that plane.
Take notes, similar to the last thing you did in part 1.


Step 3 – full bottom

As in step 1 and 2, repeat this in the bottom position, test fire in bot bottom right and bottom left positions.
– Do a test fire and have a look at the tape on the mirror, adjust mirror 2 until you hit center.

Bottom right position

Bottom left position

Take notes of the dot position on the mirrors, this will translate to how your gantry is out of alignment. In Part 3 we go into how to fix the issues.

Part 3 – translating your notes to a solution

Now it´s time to identify your notes, how the beam moves on the surface of your mirrors.
The beam cannot bend, you can only move the mirrors side to side, up or down or the angle, if the beam deviates when the mirror moves it´s not the beams fault, it´s the gantry´s fault, and you can never ever align that with the mirrors.

I will now go trough a possible scenario with how my laser behaved, and how i fixed it.

Here is a fictional result, i´ll show where the beam hit and how to solve it.


Results from Part 1 – Step 2 – test-fire 1 and 2
Where the 2nd mirror is at bottom and top.

Test fire 1 – 2nd mirror at bottom

Test fire 2 – 2nd mirror at top
Explanation:
When you did Part 1 – step 2, you centered the laser beam on the bottom location. So here the dot is in the center as it supposed to.
Test fire 2 shows the dot has moved down and to the right, this shows the gantry is leaning towards the top, being lower than the bottom part.
The dot moving to the right tells you the gantry is skewed, the top part of the gantry is not square.

Solution:
Shim the top part of the gantry with paper or thinner plastic to raise the top left part of the gantry. To solve the left-right movement of the dot, make sure the gantry is square, loosen the bolts and use a true 90 degree speedsquare or similar that you know is 100% angled to align the gantry.


Results from Part 2 – Step 1 and 2
Where the 3rd mirror is at top right and top left.

Test fire 1 – 3rd mirror at top right

Test fire 2 – 3rd mirror at top left
Explanation:
When you did Part 2 – step 1, you centered the laser beam on the top right location. So here the dot is in the center as it supposed to.
Test fire 2 shows the dot has moved left, this shows the moving X gantry is not square and moves diagonal from right to left.
The dot moving up tells you the gantry is is not level and needs to be shimmed in the top left position, same results as from Part 1.

Solution:
Shim the top part left of the gantry with paper or thinner plastic to raise the top left part of the gantry. To solve the left-right movement of the dot, make sure the moving X-bar is square to the rigid pieces it moves on, loosen the bolts and use a true 90 degree speedsquare or similar that you know is 100% angled to align the gantry.
This piece is pretty often cut bad from factory and it may help filing the edge a bit, or shimming if with paper or thin plastic. Do not bend it by force.

Here is a visual example of the problem when the X-axis dot moves left or right.


Results from Part 2 – Step 3 – test fire 1 and 2
Where the 3rd mirror is at bottom right and bottom left

Test fire 1 – 3rd mirror at bottom right

Test fire 2 – 3rd mirror at bottom left
Explanation and solution:
Identical to the previous example, as the gantry is leaning and is skewed.

Part 4 – aligning your machine

Well, actually this is what you have done in the past three steps and at the same time you fixed the reasons why it would not align properly when you tried before.
You may have to make some smaller adjustments but no sweat, you have conquered the hardest part and aligning now is done with a smile :)

Good luck!

Explanations

Here is some explanations of what the parts in the machine are and how they work.
Y-axis: The movement of the gantry from top to bottom.
X-axis: The movement of the gantry from left to right.

How to square up and level your machine
As the K40 is not one machine, there is different gantrys and solution how they work.
The principal is the same though, if the dot moves down from the furthest position to the closest, the closest position have to come up. And the opposite if the dot moved up.
This applies to both X and Y axis.

When the dot moves left or right you have a squareness issue with the gantry.
If it is on the Y-axis the main parts of the machine bolted to the floor needs to be loosened and squared up.
If it moves left or right on the X-axis, the moving part of the gantry is not square to the main Y-axis.

If you need further help aligning the parts, ask in the Facebook group and post pictures on your results for quicker help!

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HP Persson

Digging up the strange ideas and convert them into useful tools and addons for the lasers.
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10 thoughts on “Mirror alignment – no more sweat and tears

  1. christophe guerbette

    Hakan !! I never saw or read this aspect of a true alignment, bravo to you !!
    Even if the setting steps are scary !!!
    Thank you!!!!

  2. Phil reed

    please hurry with the results bit. my gantry came not screwed down so its like i put thethe together myself. i can get so for but the last but always is off by 1-2mm. its driving me nuts cos no matter what i try it wont setup.

  3. Erik

    Hi,

    Maybe a good idea to include the advice to disconnect the motors to prevent blowing up your drivers when manually moving the laser head ?

    Grtz,
    Erik

    1. HP Persson Post author

      Thank you, good idea, i have added a small warning-box at the top of the article.

  4. Rich Lee

    Excellent tutorial HP, I have been battling with mirror alignment since day one. Your instructions seem straightforward and they’re easy to understand. Thank you.

  5. Doug

    Excellent tutorial that I hope will work for me. My gantry is all made together in a square but I was able to square it pretty much by shifting it a little and then tightening the bolts down. For more adjustments would you suggest adjusting the brackets that attach the mirror assembly to the gantry? Any help you can give to the three screws and what affect each has?

    1. HP Persson Post author

      The alignment screws are pretty simple when you get a hang of it. Top one will move the beam down, lower edge screw will move it up, and the corner screw diagonal (angle). They are not precise, so you may get side-movement from all of them but start off with small small adjustments and a big paper you test fire at, to see more how the mirror holder behaves when moving the screws. Remember to close the lid or look away when test firing!
      Do not touch the brackets until you tested the other solutions, you are increasing possible angles by 10x by moving the brackets :)

  6. Kris

    Great tutorial. I’m having an x axis issue where dot is moving left, my question is where are the bolts that need to be loosened to square the x axis? Thanks in advance!

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