[Jacala]

Hello!

I've been building my own laser engraver and it works! :cheers:

But alignment of the mirrors is troublesome. The first lens in front of the laser is aligned, machine in Y=0 gives exactly the same mark as machine in Y=650 (millimeters) on the second mirror.

So the first mirror should be fine!

Now to get the second mirror hitting the laserhead:

Y=300 (middle of the Y axis)
put the laser head in x=0, burn, put the head on X850, ajust and there you go, mirrors aligned.

But now it gets weird:

machine Y=0 X=0 burn 1
machine Y=300 x=0 burn 2
machine y=650 x=0 burn 3

Al the 3 markings (on the laserhead!) are in the same location. So thats good.

Here it goes wrong:
machine Y=0 X=800 burn 4
machine Y=300 x=800 burn 5
machine y=650 x=800 burn 6

now the markings on the laserhead are way of, 5 mm each.
Burn 4 is way to the left.
burn 5 is "center" and good to work with.
Burn 6 is way to the right.

You can understand that I'm losing lots of power and I can not find the problem!

Can you guys give any sugestions?

Jacala,
The Netherlands.

[keebler303]

it sounds like your table is twisted. The X=0 side is straight, the X=800 side is at a slight angle so it works out to being about correct in the center, off one way on one end, off the other way on the other end. An accurate level should allow you to set your machine dead flat, then get back to working on the alignment.

Matt

[Jacala]

That would be logical if the deflection would be vertical but the deflection is horizontal. I get 3 dots in a horizontal line.

That the weird thing, on the 800 side the vertical burn mark the same height as everywhere in the work area. So horizontal alignment must be correct (or everything is at a angle what theoretically would not matter)

It is almost like having a bigger timing belt pulley on one side, pulling the arm sideways. Of course that is not the problem.

That is way I can not place the problem, i've got 1 dual shaft steppermoter connected trough a rod with the x 0 and x 800 side. the same pullys on both sides.

I understand a deflection that is the same everywhere, but to the this behavior:
5 mm left on y=0 x=800
middle fine =300 x=800 (but i've aligned the laser in the middle position so that is logical)
5mm right on y=600 x=800

is a mystery for me.

[TechGraphix]

Yes, every axis needs to be exactly horizontal or at least in the same plane.
try to get a digital protractor for a while..
You could contact me (i'm in Den Helder and also on cnczone.nl as Audiomanics)

Kees

[Jacala]

Ha,

You must be Kees with the Käser!

I've talked to you on the dutch version on this site.

Could you explain to me how a deflection in the X=800 linear guide (not being horizontal) could result in a deflection from left to right? A up down deflection is logical when not horizontal but a deflection from left to right?

X=0 no problem

I'm not stupid but I do not understand the horizontal part causing a left to right deflection.

[keebler303]

Jacala

I might be completely lost since I don't understand your machine configuration but with a 45 degree mirror, a vertical displacement of the beam will become a horizontal error. Can you post some pics or a drawing of how your machine is setup?

Matt

[Jacala]

In this link you can see a image of the laser setup, just a normal system. When the delivery mirror is close to the y axis mirror there is no deflection.

When the delivery mirror is far from the y axis mirror there develops a difference like stated in previous posts.

Is this image clear enough?

When it stays unclear I will make a video for you.

Jacala

I might be completely lost since I don't understand your machine configuration but with a 45 degree mirror, a vertical displacement of the beam will become a horizontal error. Can you post some pics or a drawing of how your machine is setup?

Matt

[keebler303]

Yes, that is the standard setup.

Y axis is perpendicular to the laser tube?
X is parallel?
Y=0 x=0 is near the first mirror?

The 5mm errors are in which axis?

[TechGraphix]

Could you explain to me how a deflection in the X=800 linear guide (not being horizontal) could result in a deflection from left to right?

Yes.. i will try..
Your X-bridge moves over two Y-rails.. one on the left and one on the right.
If the left Y-rails is horizontal but the right on is tilted down by a degree or so, the ray will enter the head's mirror in the centre in the middle of X, where you adjusted it..
All in the back this will give you no problem as the X-bridge is horizontal there.. But when you move the x-bridge to the front, your right side is below the left side.
When you move the head more to the left, this mirror will come up a certain distance. The heads mirror will reflect this on a different part of the lens and this will result in a displacement of the focus-point.
If you move the head to the far right, the ray will enter higher on the head's mirror and give you a focus point on the other side..
That's why you should check all rails with a (digital) protractor. If they are within 0.05 degree you shouldn't have any problem..

Kees

[Jacala]

Yes, that is the standard setup.

Y axis is perpendicular to the laser tube? yes
X is parallel? yes
Y=0 x=0 is near the first mirror? yes

The 5mm errors are in which axis?

The 5 mm errors are on the delivery mirror (the mirror that sends the laser trough the focuslens/laserhead. The errors are in the horizontal plane.

Left from the center and right of the center. There is absolutely no deflection up or down.

[Jacala]

Techgraphix, would this protractor be good enough?

Digital Bevel Box Inclinometer Angle Gauge Meter Protractor 360° Magnets Base | eBay

[Jacala]

Techgraphix, i've just ordered this digital protractor.

Laserliner DigiLevel compact | waterpas| PT serie 081.202A | Toolmax Bosch Makita Dewalt

I'll come back when this does not fix the problem!

[daweilaser]

hi, Jacala. This is Jack, form Shandong Liaocheng David Laser Science&Technology Co.,Ltd.
I have realized your problem. the second mirrors should be adjusted,
i will make a video at tomorrow.
Show how to make all the burns on on point.

[Jacala]

Hi Jack,

That would be verry nice of you! I'm looking forward to your video about the problem!

[Jacala]

Hello!

The problem is not solved yet. The alignment is not the problem (I think) I've tested it with a digital level and it was fine. To test a extreme displacement I lifted 1 guide 10 mm to get it way off and this did not change or worsen the problem.

I've made a video about it to show the problem.

laser trouble - YouTube

[TechGraphix]

Oh, this is a bit different from what i understood..
Are you sure all angles are 90 degrees? Both horizontal and vertical?
Does the laserbeam hit all the mirrors in the centre?
Can your tube be positioned in the brackets? try to rotate it in horizontal plane, adjust the mirrors and see what happens..
I remember i has something similar but after the last mirror.. I reversed the adjustment and finaly tilted and rotated the tube a little.. that did it for me..
Kees

[FanFan]

Jacala, Hello. Nice video. Hopefully Jack can posts a video of how to do the alignment. It should be very helpful. I would follow the laser beam as it come out of the laser. Look where the problem shows up. It looks like the laser beam is aligned until it come to the last movement that you make where the 3 shots are progressively "marching" to the right. Have you try adjusting the mirror that the beam comes from just before hitting those two mirrors actually I should have said the mirror in the near and far postion.? Make small adjustments and see how the shots react. Good luck. FanFan

Oohps, I didn't read all of the postings. I missed the intial comments and also the drawing. I was probably on the page 2 and didn't realize that there was another page of posting. I like your drawing. I wish I knew how to do that. It might be easy to illustrate what the laser beam is doing with a drawing. Or a series of drawings. Anyways after reading all the post I think I am still right. You mentioned that the beam is "walking" (or shifting) in the same direction the further y axis is positioned away from Y=0. Say if you could take another shot at y=900 then burn 7 sould be another 5mm to the right of burn 6. That is what I mean by the beam "walking." I am guessing that the mirror that is not aligned properly is not hitting the center of next mirror because it is not squared. Perhaps a way to visualize it is to draw three mirrors ( properly aligned) sitting on three corners of a cube or a square. Now imagine that straight shooting laser beam as it hits each of the mirrors. It would hitting each of the mirror in the center. Now imagine taking one of those mirrors and exaggerate knocking it out of alignment. Imagine where the beam would now being misdirected. Is that clear and easy to understand? Probably clear as mud. I think a drawing(s) would help explain it much better.

[Jacala]

I've found the problem!

For some reason the sideblock that carries the mirror, linear guides and timingbelt tilts a little bit in comparison to the arm that carrys the delivery head.

There must be a minimal difference in the distance between the 2 linear guides that causes this effect. When I loosen the bolts of the linear guides on the mirrorside the effect almost disappears completely.

To solve the problem i'm gonna make a new mirror mount that is mounted to the x guiderail. Then the effect is canceled out.

Thanks for thinking with me!

[TechGraphix]

Great! it had to be something like that. I hope your protractor helped finding it.

Kees