Laser alignment

[Chris Clayton]

Ok back to square one. Here is what I have done:
*Gantry and laser tube rail are 90 degrees to Y rails
*Y Rails are perfectly level, shimmed to correct twist, and co-planar
*laser tube is perfectly level

At this point, I understand the mirror alignment part fairly well and think this is an issue with something bent somewhere.
Here is what it's doing:

Y-axis is aligned and x-axis is aligned at furthest points from tube (closest to me), moving to back right corner the beam hits .5" high
Y-axis aligned and x-axis is aligned with gantry closest to tube, move to front right corner and beam hits .5" lower

I'm going to re-check to make sure the master rail is not slightly twisted, but last I checked it was level. I can see where the beam starts to angle higher when I run the laser head closest to the master rail and it's spot on until getting closer to back of machine and the spot hits slightly higher. 4 feet later and it's .5" off. The only thing that's not perfect right now is the gantry being slightly bowed in the middle but I don't see how that would affect anything when laser head is at the same position closest to master rail and the opposite side.

Assuming tube is level, rails level and coplanar, Y-axis aligned, what could possibly be off?

[Chris Clayton]

scratch that. The master rail IS twisted slightly off-center. I wasn't looking for perfection when I initially shimmed for twisting a few days ago. I'll mess with that tomorrow morning and hopefully I can report back that it's fixed.

[Rich Harman]

Actually, the tube being level is not important for alignment. The tube could be in any position, as long as it strikes the first mirror the beam can be steered where it needs to go. My tube is intentionally non-level, the far end is slightly lower to help air bubbles work their way out.

[Chris Clayton]

Very interesting Rich, thank you for sharing that! I'm assuming an air bubble would leave a small spot un-cooled or a different temp than the rest of tube and it could cause a crack or something?

[Mike Lysov]

Y-axis is aligned and x-axis is aligned at furthest points from tube (closest to me), moving to back right corner the beam hits .5" high
Y-axis aligned and x-axis is aligned with gantry closest to tube, move to front right corner and beam hits .5" lower

It looks like the bottom part(closer to you) of the right Y rail is lower than the same part for the left Y rail and the farthest part(closer to the tube) of the right Y rail is higher than the same part for the left Y rail.

Do you have a digital angle gauge? If you do, put the gauge on the left Y rail and on the right Y rail and you should see the difference between angles each of them is sitting at.

The rails may be perfectly parallel to each other and square to the X rail but two rails of Y axis may not be running along the same horizontal plane. If the left one is sitting at one angle and the right one at another you will get something similar to what you are getting.

And I agree with Rich, it does not matter if the tube is leveled. You are controlling the beam with the first mirror to send it along required plane. Technically the tube can even be installed in a vertical position and it will still work for the beam alignment.

[Bill George]

My thought for the day..... I do not know how big this machine bed is.... but a laser level like used for construction but a small one. Put it in the bed, in the center and no the machine does not need to be level but all the rails need to be on the same plane. Does it make sense? I have something almost like this and I use it a lot. Mine is an older Stanley without all the add on rulers.

There are a lot more expensive, professional grades ones also.
> https://www.amazon.com/Qooltek-Multi...ds=laser+level

[Jerome Stanek]

My thought for the day..... I do not know how big this machine bed is.... but a laser level like used for construction but a small one. Put it in the bed, in the center and no the machine does not need to be level but all the rails need to be on the same plane. Does it make sense? I have something almost like this and I use it a lot. Mine is an older Stanley without all the add on rulers.

There are a lot more expensive, professional grades ones also.
> https://www.amazon.com/Qooltek-Multi...ds=laser+level

That won't doesn't always work as the bed could be out of level and the rails could then be level. I had a lot of problems when I first went to align my laser as I could not get all the dots to hit the center first my tube was on an angle and then I found out that 1 mirror was higher than the rest. after I solved those problems it was easy to get the beam to hit center.

[Bill George]

What I said : and no the machine does not need to be level but all the rails need to be on the same plane

If his machine frame is not square and the rails are not on the same Plane you can be aligning mirrors all day and when they move it will be off. That is why I suggested the laser level to get one fixed point to work off of, like Mike was suggesting above.

[Rich Harman]

...I'm assuming an air bubble would leave a small spot un-cooled or a different temp than the rest of tube and it could cause a crack or something?

Depends upon the design of the tube. Some tubes have the water coming in in such a way that an air bubble can cause the end to overheat, the Reci tubes that I use are a little different, not as sensitive to an air bubble because the only place a bubble can form is away from the end - assuming the tube is installed right side up. With the tube at a slight angle any air bubbles that do appear can slowly march their way to the other end and out of the tube. It probably does not absolutely need to be angled, but it helps.

[Ian Stewart-Koster]

When we had similar problems with the beam hitting M2 in the same spot, front & back, and hitting M3 in the same place all along the front edge, but way out in the remaining back corner, I fixed it by packing up under the laser feet on the floor, under that back corner, to bring the two Y axes parallel and level (coplanar) again.

It took some initial adjustment to get the beams parallel to the gantries.
I now have a different issue that I'll start a fresh thread on- a weird shaped dot.

[Chris Clayton]

Mike, I appreciate your thoughts. I did buy a digital level but when I placed it on a 4ft level on top of the y-rails, one side said 0.0 and the other said 0.1. That may confirm what you're saying and I'll adjust the offending rail soon, but I think it's so close that my problem lies somewhere else.

UPDATE:
A few fun things I learned:

*The issue of the beam moving around after alignment was a simple and embarrassing fix. I was thinking so much about the rails and beam alignment that I over looked the actual mirror mount for M2. The threaded disk behind the mirror was loose. I tightened it up and fixed that problem.

*The laser head/M3 was not 100% level. I put a few shims underneath the back side of it and leveled it out. Not sure if that helps anything but I'll pretend I accomplished something.

I really think my last issue is the rails being twisted. I initially shimmed the y-rails to correct for twist and had them fairly level (at least according to a small line level placed on top of rail). Now they are WAY off. On the master rail, the bubble is touching the line on bottom left corner and going a little past the line at top left. Angled down towards middle of machine. It WAS very close to level, albeit very slightly off. The other side is just as bad, I think angled the same way...IIRC.

QUESTION: Could I be dealing with stability/movement issues with the tubing because the shop isn't climate controlled? It's rectangular aluminum tubing. I've been looking at some of the info on epoxy leveling etc.

[Doug Fisher]

I don't have time to read back through three pages of posts but one thing came to mind - have you leveled your machine itself at the wheels/casters and then never moved it since that time? If you have an unlevel floor and you move your machine even slightly then you very likely could be chasing your tail. Just a thought.

[Chris Clayton]

I don't have time to read back through three pages of posts but one thing came to mind - have you leveled your machine itself at the wheels/casters and then never moved it since that time? If you have an unlevel floor and you move your machine even slightly then you very likely could be chasing your tail. Just a thought.

Everyone has given great tips but nothing has been resolved besides the two fixes I posted earlier, so you didn't miss anything. Before I started, I leveled the machine. Then the fun began with finding the rails not level, twisted, bowing, x and y slightly out of square etc etc. It's been great fun. Honestly though it's a great learning experience and I hope to just buy my own rails when the time comes for a 4x8 machine of my own.

Tell me this, would you (or anyone else) know the proper search term for different kinds of leveling designs? I mean, my neck hurts from constantly being under the laser and removing the 4 rail bolts....over and over again. I was thinking of using bolts/nuts to make it so I can twist and raise/lower the rails from the top or something. Forgive my ignorance...something like "leveling screws"?