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Chris Clayton
07-24-2017, 1:14 PM
Hey peoples. I hate to ask about laser alignment because I know there is a lot of info out there, but I have a quick question.

I'm trying to help a guy fix up his big Chinese machine. I've made sure the machine is level and attempted to align the mirrors. If the Y-axis is straight (center of 2nd mirror at closest to tube and furthest point), and the 3rd mirror on gantry is aligned at furthest points from tube (closest to operator on left and right side), then shouldn't the two corners closest to the tube also be perfectly centered?

I can get the x-axis straight when closest to me, but as the gantry moves closer to the tube it starts going way off and hitting higher. The previous owner had washers under the rail and I'm wondering if I should start messing with the actual machine or if it sounds like adjusting mirrors could still fix problem.

I'm just thinking of the x-axis is perfect on one end of the machine, it should be the same on the other?

Sorry if this is a stupid question and thanks for any input. I'll try to add photos later if that helps.

Chris Clayton
07-24-2017, 2:10 PM
I'm so lost. Can a co2 beam shoot out at different directions by any chance? I don't know if the mirror adjustment screws are moving or what, but I had the x-axis centered, moved gantry towards tube and the beam hit higher, then moved gantry back closest to me and the beam now hits lower than center. I'm assuming this might be why the previous owner had some kind of white silicone on the back of the screws...

Kev Williams
07-24-2017, 3:42 PM
I haven't done this too many times but what works for me is this procedure---

1- make sure laser is hitting mirror one in the center.

2- move the gantry rail all the way down towards you, and the laser head as far from mirror 2 as possible.

3-check burn for center on mirror two. Move mirror one until beam is centered.

3- now move the gantry all the up, and check mirror 2 again for center. Goal is to have the beam hits the mirror as close to the same spot on mirror 2 with gantry full up as full down. If it's not, tweak mirror one until the beams match. Absolute dead on not necessary, but if you can't get it very close, the tube will need to be adjusted. (hope not :) )

4- Once mirror two is set, repeat for mirror 3 over the lens, adjust mirror 2 until beam hits mirror 3 in the same place from full left as full right.

5- once that's done, set up mirror 3 to hit dead center on the lens.

There should be 2 sets of mirror screws on each mirror, one set of 3 spring loaded for adjusting, which should stay put, and a set of 3 thumbscrews with a jam nut or knurled ring. You don't TIGHTEN the thumbscrews, as they also act as adjusters. When the mirror is where you want it, if any thumbscrew is loose, just turn it in only until it makes contact with the mirror frame, then tighten all the jam nuts.

For what it's worth, on my Triumph some of my thumbscrews are loose, and pretty much none of my jam nuts are tight (I just checked! ;) ) and I've only had to make one minor adjustment to mirror 2 in going on 4 years, and that was right after my broken stepper wire caused some rather violent vibration in the drive train...

Rich Harman
07-24-2017, 5:52 PM
It sounds like either something is loose and shifting, or the two Y axis rails are not lying on the same plane. I had the problem with the rails not being planar. I had to shim up the left rail nearest mirror one in order to get it close. It is still not absolutely perfect. If I put the third mirror at the bottom right, fire a mark, middle right then back right - the middle mark is slightly higher than the other two. That indicates that one of the rails has a slight bow to it.

Rigging up a red dot laser to the output of the main tube so that it passes through all the mirrors was quite enlightening. You could see how the dot wandered around the target as the laser head was moved to various positions around the table.

Something else I did when I first got my machine, I made a small triangle bracket to stiffen up the sheet metal base that the second mirror assembly is mounted to. Light finger pressure on the second mirror would cause it to deflect - didn't think that was a good thing. That was six (?) years ago and it seems to have worked out well. Someday I will take this thing completely apart and rebuild it, without the imperfections.

Rich Harman
07-24-2017, 6:52 PM
...Absolute dead on not necessary, but if you can't get it very close, the tube will need to be adjusted. (hope not :) )

If the beam is hitting mirror one in the center there will be no reason to adjust the tube. The only exception is if mirror one needs to be raised or lowered, then you would have to adjust the tube so that it once again hits mirror one in the center. In other words, if you are having trouble getting the two spots to line up on mirror two - it isn't the tube, it's mirror one.

What I do;



Put two pieces of tape over mirror two on the side facing the incoming beam, move the gantry to be as close to mirror one as possible and fire a mark.
Move the gantry as far away as possible from mirror one (pull it towards you) and using a fine point sharpie, draw cross hairs centered on the mark.
Fire another mark, just enough to be barely visible. If it is off then make a small adjustment and fire again. You can make several adjustments without having to re-fire the initial mark. You can even put another piece of tape on and transfer the cross hairs to the new piece and continue fine tuning. It is much more important that the two spots line up than for the beam to be in the center of the mirror. What we are doing here is steering the beam so that it is exactly parallel to the Y axis rails. If the beam hits the mirror slightly off center you could even consider that an advantage - you'll be able to rotate the mirror in it's holder to expose new parts to the beam, saving having to buy a new one.
When satisfied that you cannot improve the alignment, put new tape on and start the process over. If the two marks are in perfect alignment then you are done with adjusting mirror one. If not then go to step 1. Generally only one round is required. If I have moved the tube or replaced mirror one, then it may take two or three rounds. Each round only takes a few minutes.


I think that getting mirror one perfect (meaning that I can't see a difference is spot position) is very important. If it isn't, whatever inaccuracy it has will be amplified as the beam travels further. If mirror one isn't "perfect" then when you adjust mirror two - that adjustment will only be correct for whatever position the gantry was in when you aligned it. Also, the larger table you have, the more critical alignment becomes.

Adjusting mirror two is the same process. The difference is that it is fairly important to hit the third mirror in the center. If the beam hits mirror three off-center then you would need to adjust mirror three to steer the beam to the center of the lens. Which means that the beam would be entering the lens at an angle, which means the beam will be coming out of the lens at an angle. The amount of this angle will depend upon the distance between mirror three and the lens, shorter distance means greater angle.

To correct for being off centered (left to right) on mirror three you must move mirror two - meaning you must loosen the mirror mount and slide the mirror holder. If the mark is high or low then you must adjust the tube to hit mirror one higher or lower. It may require raising mirror one and two also. This is assuming your third mirror cannot be moved higher or lower, if it can then you would move it instead.

You shouldn't have to resort to moving the mirrors, they should have been set up correctly at the factory, you should only need to align them. However, on both machines I have imported it was necessary to move the mirrors. The setup was so poor it was laughable. On the second machine the beam was literally clipping the hole where it passed through the case after mirror one.

Chris Clayton
07-24-2017, 9:05 PM
Thank you guys for your input. I'll be back in a few hours to write a proper response.

Rich Harman
07-24-2017, 9:30 PM
...I had the x-axis centered, moved gantry towards tube and the beam hit higher, then moved gantry back closest to me and the beam now hits lower than center.

That behavior is perfectly consistent with mirror one not being aligned properly. As the beam leaves mirror one it is on a downward slope. The longer the beam path becomes, the lower the spot goes.

Chris Clayton
07-25-2017, 8:52 PM
Thanks for the assistance Kev!

Chris Clayton
07-25-2017, 8:55 PM
I definitely think the y-axis rails are not on the same plane. Thanks for your thoughts. I was thinking it might be easier to make a new machine as well haha.

Chris Clayton
07-25-2017, 9:05 PM
Really appreciate the time you (and everyone) spent replying to my S.O.S. I had a feeling yesterday that once the beam was aligned on mirror 3 (on left and right sides), I would need to adjust mirror 2 mounts to make mirror 3 centered (because it was aligned on left and right side of machine but not centered). When I first went to help this guy with his machine, the beam was hitting the metal circle thing as well.

Chris Clayton
07-25-2017, 9:08 PM
What confuses me is that mirror 2 was/is aligned and hits the same spot closest to mirror 1 and furthest from it. If the beam is slightly off and mirror 1 is adjusted to be straight with the y-axis, that's all that matters correct?

Chris Clayton
07-25-2017, 9:22 PM
ok so I'm going to see if I can add some images. I have the tube leveled and hitting mirror 1 pretty close to center, not perfect but I'm more concerned with the beam hitting it straight on (so I can see what's happening with the other mirrors). On mirror 2, the beam hits the exact same spot when the gantry rail thingy-ma-bob is closest to the tube and when it's furthest away. So I'm thinking that means the beam is going straight down the y-axis? Even though it's not as perfectly centered as I'd like (in a perfect world). Then I get to the 3rd mirror. When gantry is closest to me (furthest from machine) on the left side and right side, I can get it centered. I'm assuming I'll need to play with the 2nd mirrors mounts and tube height to get it perfect, but I'm not aiming for that yet.

So we have y-axis completely straight and x-axis completely straight when gantry is closest to me. As I move the gantry away from me on the right side (back of tube side), it starts acting really wonky. In the middle, beam hits mirror 3 towards lower left. Keep moving it back about 3/4 of table and beam hits higher. Move it to back right corner and it hits even higher to the left. I'm thinking the y-axis rails are off, but I'm not 100% sure. I'm not a mathematician but if everything (rails etc) was level and on the same plane with each other, I would think the back right corner would be the exact same as the front right corner, correct? The worst part is that when I move the gantry to the back right corner and then move it back to the front right corner, the position changes on the 3rd mirror. Before moving it, the 3rd mirror (x-axis) is perfectly lined up on the front left and front right corners. Then I move it to the back right corner and it comes back hitting way lower. I really hate this thing right now haha

Thanks again guys!364574364575364576364577

Bill George
07-25-2017, 9:29 PM
Big Chinese machine, hmm do you suppose the rails and such are parallel with one another? If you can't keep mirrors aligned properly or to begin with that is what I would check first. Once your assured the machine is level, square and straight then the mirrors should not be that hard to do.

Chris Clayton
07-25-2017, 11:29 PM
Oh and don't get me wrong, I understand the beam going into the 3rd mirror needs to be dead center. For now I just need to figure out what's throwing it off so much when y-axis is aligned (even if off center of mirror slightly) and when x-axis is aligned towards front of table. I'll do some more tinkering this week and please let me know if anyone can make sense of the photo showing the beam hitting 3rd mirror in the center when gantry is towards front of machine, lower when in the middle of table, then jumps higher at back right corner.

*shakes fist at China*

Bill George
07-26-2017, 8:23 AM
The machine needs to be square and rails, gantry parallel before your going to solve the mirror issue.

Bert Kemp
07-26-2017, 5:42 PM
an observation Looks like your pushing the tape into the mirror, if thats the case make sure and dbl sure you clean those mirrors before trying to use the laser or you will be replacing mirrors real quick.

Chris Clayton
07-26-2017, 7:42 PM
Hey Bill, thanks for that. That makes perfect sense. I did check the gantry and rails to make sure they are 90 degrees but I'm going to buy a digital protractor/angle finder to be more accurate and also use a dial gauge to check the basics before I mess with the mirrors any more.

Chris Clayton
07-26-2017, 9:32 PM
an observation Looks like your pushing the tape into the mirror, if thats the case make sure and dbl sure you clean those mirrors before trying to use the laser or you will be replacing mirrors real quick.

Very true. Once alignment is done I'm going to recommend we get new mirrors and a lens. I haven't mentioned yet that we should get a bigger compressor and air dryer to keep the Houston humidity off the lens. Baby steps haha

Bill George
07-26-2017, 11:08 PM
Very true. Once alignment is done I'm going to recommend we get new mirrors and a lens. I haven't mentioned yet that we should get a bigger compressor and air dryer to keep the Houston humidity off the lens. Baby steps haha

Nah, just clean the mirrors with DNA. If you run A/C and keep the shop cool your air compressor will not have as much water in the air lines. I do also have an refrigerated air dryer, but my laser just uses a fish tank air compresser so I don't need.

Joseph Shawa
07-26-2017, 11:38 PM
If you get same tight spots on mirror 3 left and right in different Y positions then your right rail is not level.

Chris Clayton
07-27-2017, 1:31 AM
The thing that confuses me is that x-axis will be centered when closest to me, then move lower left at mid-machine, then jump UP as it nears the back right corner. Then I move gantry back to me and instead of being centered like it was 20 seconds before, it's now lower than center. A gradual up or down I could handle and I'd know the rail just needs to be raised or lowered. I hate this thing but at least after figuring it out, I'll be able to make my own laser in the future haha. I'm looking at ways to make sure the rails are co-planar/on the same plane/whatever the word is. I'll keep checking in and write an update after looking at it on friday. Thanks people

Dave Sheldrake
07-27-2017, 2:19 AM
Align the output of the laser tube optics with the hole in the laser head,making sure it is parallel with the gantry bearing, then work back from the head on the mirrors

Rich Harman
07-27-2017, 5:02 AM
Hey Bill, thanks for that. That makes perfect sense. I did check the gantry and rails to make sure they are 90 degrees but I'm going to buy a digital protractor/angle finder to be more accurate and also use a dial gauge to check the basics before I mess with the mirrors any more.

The easiest way to check for the Y axis being perpendicular to the X axis is to have the laser draw a large square, then measure the diagonals. If they are equal then it is square.

Joseph Shawa
07-27-2017, 6:59 PM
Never mind.

Chris Clayton
07-29-2017, 1:54 AM
I wasn't able to make it to the shop today. When I look at it again, I think I'm ripping off the right rail to see if it's twisted or bowed. Thinking about it, if the rail was higher in the center and then sloped back down, that would cause the beam to hit the 3rd mirror lower in the middle of table and then higher as it goes towards the back right corner. Really appreciate you guys and I'll be back within the next few days. Have a great weekend!

Phil Berch
08-07-2017, 4:57 AM
Hi Chris,
I am about to align up the mirrors on our omnisign plus 50 watt laser. have a look at these two video's they may help
https://www.youtube.com/watch?v=5YvOqH44n6c&list=PLeKaKWOIPgi_XP6Nxzeapp-vUMCLQyVMB&index=65 (https://www.youtube.com/watch?v=5YvOqH44n6c&list=PLeKaKWOIPgi_XP6Nxzeapp-vUMCLQyVMB&index=65)

https://www.youtube.com/watch?v=pl6dAWOkksM&list=PLeKaKWOIPgi_XP6Nxzeapp-vUMCLQyVMB&index=66 (https://www.youtube.com/watch?v=pl6dAWOkksM&list=PLeKaKWOIPgi_XP6Nxzeapp-vUMCLQyVMB&index=66)
Phil

Mike Lysov
08-10-2017, 9:45 PM
ok so I'm going to see if I can add some images.

Thanks again guys!364574364575364576364577


Is it what you have now? I can try to explain what is wrong if you can show me results from the following test

1)fire at the mirror #2 at its closest position to the mirror # 1 (lets call it Y1 burn spot) and at its farthest position from the mirror # 1 (lets call it Y2 burn spot)
If both Y1 and Y2 marks land on the mirror #2 it is good. It does not matter if it lands on the centre of the mirror # 2 or not as long as the Y1 and Y2 somewhere on the mirror # 2
2) using adjustment knobs on the mirror #1 bring Y2 burn spot exactly to the centre of the mirror #2
3) Now if you do another Y1 and show it to us it should be quite easy to tell what you will need to do.

You may have rails unsquare or may be it is just the mirror # 1 holder is in the wrong spot or the mirror # 1 sits in its holder at the wrong angle. It may be even all of these problems together at the same time. However to see what you will need to do to align it you will need to do these three simple steps above first.

Kev Williams
08-11-2017, 4:15 AM
Before I'd tear off any rails to see it they're bowed, I'd measure the rail, then go to Harbor Freight and pick up one of their $4 aluminum rulers that's just a bit shorter (or hacksaw off a longer one, as cheap as they are). The rulers edge will be flat enough to check your rails straightness without removing it...

Mike Lysov
08-11-2017, 8:32 PM
I would not touch rails at all at this point. It is very likely that the mirror #1 holder is just in a wrong position and rails are ok. So if that's true and you start playing with rails you may create a nightmare for yourself where you will have both optical and mechanical problems.

The first mirror that sends a beam from a tube along Y axis is very important for a beam alignment. If it is in a wrong place, has a wrong angle in relation to a beam plane coming from a tube you will never align a beam.

The steps I have described above will help you to see if a beam travels along Y perfectly. If it is not it is most likely to be a problem with the mirror # 1 set up wrong. Adjusting its position by moving the mirror holder you can set it up absolutely perfectly at least for the close end and the far end of Y.
If Y rail is bent it will be obvious once you start to move for the far end to the close end or in other direction but at least you will know it is bent because you can be sure you have aligned both ends of the rail with a beam path.

Bill George
08-12-2017, 11:50 AM
I go along with Kev, check the rails and the frame for square first. Pretty simple, if their off needs to be corrected first. With a normal quality laser its normally not an issue but this a cheap or perhaps damaged machine.

Chris Clayton
08-18-2017, 5:29 PM
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
08-18-2017, 5:35 PM
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
08-18-2017, 8:49 PM
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
08-19-2017, 1:15 AM
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
08-19-2017, 3:32 AM
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
08-19-2017, 10:47 AM
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-Multipurpose-measure-Adjusted-Standard/dp/B00PQ4PJYC/ref=sr_1_4?s=hi&ie=UTF8&qid=1503150304&sr=1-4&keywords=laser+level

Jerome Stanek
08-19-2017, 2:00 PM
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-Multipurpose-measure-Adjusted-Standard/dp/B00PQ4PJYC/ref=sr_1_4?s=hi&ie=UTF8&qid=1503150304&sr=1-4&keywords=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
08-19-2017, 5:06 PM
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
08-19-2017, 8:13 PM
...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
08-20-2017, 8:58 AM
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
08-26-2017, 5:26 PM
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
08-26-2017, 8:00 PM
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
08-26-2017, 8:47 PM
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"?