Idea to assist with aligning the beam.

[John Barton]

Well, after spending many hours today aligning the beam I had an idea on the way home.

I thought about making a pad of stick notes which are exactly the right size to fit on my mirrors with circles and cross hairs on them.

I am guessing most of you do the masking tape method - I do.

I thought wouldn't it be better if I had an exact visual aid?

A copy shop can make a pad of these fairly cheaply and of course we could all make our own anyway.

Is this idea worth anything, any one done anything similar? Anyone got any better tricks to align the beam?

[Larry Bratton]

Epilog supplies a round plastic target that fits in a hole on the lense carriage. The idea, of course is to get the beam to hit the bullseye on the target. I suspect you could fabricate something similar out of acrylic for your Chinese machine. Just a thought.

[James Jaragosky]

Epilog supplies a round plastic target that fits in a hole on the lense carriage. The idea, of course is to get the beam to hit the bullseye on the target. I suspect you could fabricate something similar out of acrylic for your Chinese machine. Just a thought.

I cut mine out of 3mill BB ply. I don't use cross hairs, However this would be simple to add.
Tape targets leave residue on the mirrors that I don't like.

[John Barton]

Ok cool - so people are using targets - that's good. I was thinking of the paper replaceable ones because of the burn marks and being able to toss a new one on after the marks from firing made it too hard to see where the beam is hitting.

I think I will make a couple out of a clear wood and see how that works. I will say that for sure the difference in performance between being a "little off" and being dead on is huge.

[Larry Bratton]

Well, I will say that I have found precise alignment to be critical to good cutting capability. I don't know how much it affects raster. Best practice is for it to be dead on.

[John Barton]

Well, I will say that I have found precise alignment to be critical to good cutting capability. I don't know how much it affects raster. Best practice is for it to be dead on.

I hear you and agree. I just want to find a really easy way to quickly get to dead on. Obviously I am completely ignorant of what is involved in building a laser. Well not completely as I own two of them and it's fairly obvious as to how they are built.

But, as I spent time on the alignment yesterday I found myself getting more and more frustrated with the idea of having to adjust three mirrors by feel alone and not finding that magic spot.

So I thought about it and at some point I am going to try and write a tutorial on how to get the alignment done perfectly in the shortest amount of time.

Today I thought about making acrylic shields for the mirrors, then making the paper targets to go over that. This way I can protect the mirrors from residue and yet use the target with crosshairs to get dead center in each mirror.

Theoretically once you are dead center on the first then you set the refection angle to get to dead center on the second and then to the third right? Meaning that if the beam is pointing to dead center then no matter which way the mirror is tilted the beam is still hitting dead center right?

So the method is center first angle second?

Sorry to sound like a clueless newbie but honestly with our ULS we rarely had to realign and when we did it went quickly. But with this Chinese laser it just seems all a bit more cumbersome than it was with the ULS. So for some reason I find myself being more frustrated with this one even though I am probably choosing to not remember being frustrated doing it on the ULS as well.

But five hours is totally ridiculous. I think that this job should take less than an hour at best. Even that is way too much IMO.

What I finally did which is probably like DUH for most of you is take all the mirrors to their zero unadjusted point. Then I went to center on each one first then angle. Finally we got them all dead perfect (or nearly so it seems) and cutting power magic was restored.

I am half tempted to make my disks and targets and zero it all out again and see if I can align it in under an hour.

Someone slap me. We need the machine and I won't be so self-indulgent. But next time I am definitely going to see if those things help.

[James Stokes]

What I do is take poster board and cut 3/4 inch circles out of it. Then just drop it on top of your lens.
I agree 100% that alignment can be a real Bi**H. I got a new tube for my laser and worked for over 2 days trying to get perfect alignment. I could get it close but never perfect. I could adjust one screw a 16th of an inch and it would move the beam a half inch, then turn it back that 16th of an inch and the beam would not move. I finally got it as close as I possibly could and glued the setscrews, sent back the alignment tool, have used it for two weeks and think it is out of alignment now. I tried to engrave the laserlight material and over an 8 inch square the engraving goes from barely marking to cutting all the way through. I aligned the lens on my old tube about 3 times in 5 years and never had a problem. Something is not right some where.

[John Barton]

Alignment theory -

Correct me if I am wrong.

Laser is set and hits center of mirror. The angle of the mirror can then change but the laser is still hitting the center right?

Does the laser bean need to hit dead center on a flat mirror?

Isn't any point on the flat mirror the same as any other point?

Is it then most important to get the beam aligned to the center of the lens for maximum focus on the energy?

I have been thinking about this for a while and it seems that the critical step is the line from mirror3 to the lens. This would seem to be the one which is critical to get dead center through the lens.

On the Chinese laser that mirror 3 is adjustable. IF I remember correctly the Universal's 3rd mirror is fixed and not adjustable. It's been a while since I used that machine.

Soooo - here is the problem as I see it.

If the angle of the 3rd mirror is perfectly fixed so that any reflection is going straight down through the lens then the only thing that needs to happen is to get the beam hitting THAT mirror dead center so as to get it through the center of the lens.

The 1 and 2 mirrors don't matter if the beam is hitting dead center because the beam doesn't lose any power since it's a perfect reflection no matter where on the mirror the beam is hitting.

Sorry if this is a rehashing of basic laser alignment but I am trying to get it straight in my head so as to develop a way to get this process done quickly. I honestly believe that this should be like a five minute job and not same arcane thing that relies on tremendous feel and touch and takes hours and days.

Now though the question comes in of what happens when the only moving mirror #2 moves from the front to the back. In theory the angles of the mirrors should NOT change giving you the same focus and power in all four corners.

So the variable here is obviously the quality of the construction of the rails and whether it and the frame are perfectly aligned. And also the stability of the mirror brackets and whether they maintain the mirror position once set or not.

Is my theory then correct that the only really critical alignment for maximum focus/power is the beam to mirror3 through the center of the lens?

If so then that is the hardest part on these chinese lasers due to the way the carriage/mirror/lens housing is made.

[Mike Null]

I would question that theory relative to the plane of the beam.

[John Barton]

I would question that theory relative to the plane of the beam.

The plane being the angle that it's coming out of the tube?

I am not exactly sure what you mean here can you elaborate?

[Rodne Gold]

Before one starts any beam alignment , check that your X and Y axis are square to each other and are square to the engraving surface ad that all belts and bearings are clean and lubed and have no play

The ideal in terms of alignment is to get the beam centred on the final optic all the time all over the table. You align the optics closest to the tube outwards to the final optic.
Final mirrors on most lasers are generally fixed (IE the one on the flying head finally bending the beam to the lens)

The first thing to do is to align the red beam pointer with beam itself - most red beam pointers diodes are close to the source before either it or the laser beam itself hits any mirrors - the way to do this is to use "distance" - allow the laser source and the red beam to fire at a target on a wall 6 ft from the laser (most lasers will have an opening in the casing alowing you to do this)- align these.
If you cant do this , then align the red beam to the laser beam with the best precision you can get at the first mirror they both strike.

Thereafter the red beam can be used for actual beam alignment and you can then almost dispense with the fire/burn/adjust way of seeing where you actually are in respect of the laser beam , just look at the red dot and where it hits the next mirror instead.
You normally only have one "moving" mirror - that is the one on the end of the gantry that goes down the Y axis of the machine - the flying head mirror moves too - but generally has no adjustment.
The critical adjustment is on this moving mirror.
You need to make sure that the mirror BEFORE this one is adjusted so the beam hits the moving mirror dead centre when the gantry is at the top and the bottom of its Y travel.
You then start on the "moving" mirror and adjust it to centre on the flying head mirrror at all extremes of the flying heads travel (when the gantry is at the top and the bottom of the table)
This is a ton easier to do when you have the red beam pointer as a visual aid.
The issue with most laser engravers that lose alignment is the poor implementation of the adjusting method (3 grub screws) and less than stellar mirror housings/mountings.
The first thing to do is to try beef up the housings if one can - add some stiffening battens or cut glue on acrylic pieces that will actually give some support to housings or brackets. Make sure the actual thubscrews that hold the mirror in position have a nice flat surface where they contact the actual mirror so that at a certain tension the holding power isnt concentrated to a point - always tighten these screws to the same "tension" when cleaning and replacing mirrors.
When adjusting , make sure your grubscrews run real easy in their threaded holes , best is to back em right out and lube em up and reinsert. This allows small adjustments to actually be implemented. If these grubs screws are sticky in their holes , then adjustment is like an earthquake , you twist the screw and then it "breaks free"" and moves - not by the amount you wanted- very frustrating to adjust that way. When you have alignment perfect , use something like locktite to stop the grub screws moving.
I have wanted to redesign my mirror housings from pressed steel to something like a solid block of aluminium with vernier type adjustment screws , never got round to it tho. Im surprised the laser mnfgrs havent actually fully addressed alignment issues i respect of better housings , finer adjustment procedures or even an add on auto alignment feature ( I would buy any laser that can guarantee me optimal power via an auto alignment and would consider that a vital feature - it would be a deal breaker feature - rather than silly rubbish like "3d" etc)

[Dan Hintz]

Laser is set and hits center of mirror. The angle of the mirror can then change but the laser is still hitting the center right?

Yes...

Does the laser bean need to hit dead center on a flat mirror?

Yes...

Isn't any point on the flat mirror the same as any other point?

No...

Imagine a mirror 8 feet wide. If you're pointed at the center with the mirror at a 45 degree angle, your beam takes a 90 degree turn. Now aim the beam at the edge of the mirror (without changing the location the beam comes from, you)... to do so requires you to change the angle at which you point the beam at the mirror. Instead of a 90 degree angle, the beam will be something greater than 90 degrees.

What if you take a few steps to the side so you hit the mirror at a 45 degree angle again, also making the beam angle 90 degrees? The reflected beam is now several feet farther away from you.

Draw it on a sheet of paper to make it a little more clear. In a nutshell, though, every beam should hit dead center on each mirror/optic, as well as at a 45 or 90 degree angle. Anything less will cause a mis-alignment that will continue to grow over distance.