Strange alignment problem...

[Vicente Ferrando]

Hi everyone!

I'm unable to solve this alignment problem. I'm using a laser level to adjust the machine, but something happens in the middle of the machine. Both sides are perfectly levelled,  within them and with the floor, but when the laser is in the middle right part of the bed, it looses the focus. Could be the left guide twisted?

20210607_175019.jpg

These are a couple of videos I made moving the gantry. Any ideas?

https://youtu.be/C0Nccl97EaY

https://youtu.be/jDChfL5veQc

Thank you!!!

Edit:

Left side:

20210608_164500_1.mp4

[Vicente Ferrando]

Left guide is perfecty horizontal. See attached video.

This is what I get:

16231651762436211288578669501050.jpg

Any ideas?? Kind regards!!!

[Vicente Ferrando]

New test XD

To check if the left guide is twisted, I just did the following test:

Test.jpg

And I didn't get any movement at the end of the pole. So, the left guide is not twisted...

20210608_182312_1.mp4

[Jeffrey Aley]

Interesting. You've done some pretty thorough testing. I am a bit confused by the configuration of your laser. Can you provide an "overview" photo showing the rails and gantry, and where the tube and mirrors are located?

Also, I am unsure what your photo of the 9 pieces of paper are trying to show. You later show a piece of paper with 6 burns on it; how were those burns created?

Thanks,

-Jeff

[Vicente Ferrando]

Hi Jeffrey, thanks forvyour answer!

I'll show you:

20210610_095829.jpg

20210610_095829 (1).jpg

20210610_095829 (2).jpg

I hope this helps to figure out what I was trying to explain.

Kind regards!

[Jeffrey Aley]

Thanks for posting the photos - they help me understand a bit more.

From the videos, I think I see that the left rail is level, and the right rail is level, but I can't tell if they are at the same height because your video shows different targets. Have you confirmed that if you move the head to the left side, the red line strikes the head at the same spot as it does when you move the head to the right side? In other words, the rails are level; is the gantry both level and straight? Might the gantry be slightly curved?

What I still don't understand is the 9 pieces of paper and the 6 burn marks. You very clearly showed WHERE those locations are (thanks!), but I don't know what you did to produce the burns. For example, were the 9 pieces of paper located on the bed, or were they taped to Mirror 3? Why is there a white "X" of un-burnt paper on each of the 9? How did you produce them?

Similarly, you have a piece of paper with 6 burn marks from 6 places on the laser (again, thanks for the photo!). How were those marks produced, and what do we learn from looking at them. The 2nd mark from the left is slightly higher than the others. Is that significant? I don't know because I don't know where in the path of the beam you placed that piece of paper, nor how precisely you placed it. I imagine you placed the paper very carefully, but that's just an assumption, and assumptions will not lead to a solution

Thanks,

-Jeff

[Vicente Ferrando]

Hi Jeff, thanks for your answer!

Sorry, I'll try to explaint better The nine pieces are shots using this in front of the third mirror:

Captura de pantalla 2021-06-11 085917.png

so, in some places laser seems to hit to the head higher than in others.

The six burns shows the same. I put the paper before third mirror, very carefully and, as you can see, at the front and the rear of the machine they are at the same height, but somewhere in the middle is pretty higher, specially on the right.

I also checked if the gantry is level and it seems to be. Maybe at the middle of the gantry it lowers half milimeter, but not at the beginning or the end.

I'll check if the gantry is curved, just in case, thanks for the idea!

Thanks you very much for your time. I hope I've explained all the burns a bit better now

Kind regards!!

[Gene Uselman]

Hi Vicente- I am just back to my machine after a fairly long road trip. I am working on a 1800x1300 machine after having a 1300x900 machine for 5 years and find that the large machines have a lot of, and different problems. I have a similar problem on this machine- I have checked and double checked everything, as I am sure you have. Have you checked your right hand rail for absolute straightness- they are normally shimmed in the middle and it appears the middle of your might be low/sagging? Russ [SarbarMultimedia videos] talks about a fourth corner problem with alignment in one video and that is closer to the problem I have. Gene

[Jeffrey Aley]

Thanks for the photo of the apparatus with the copper wires - I've never seen a device like that.

It appears from the photo of the 9 pieces of paper that the right rail has an upward bow in it (higher in the middle; lower at the front and back).

I know you posted a video of the right rail moving with a laser level projecting a plane; that video does not clearly show (to me) the accuracy of the motion of the head when it is all the way to the right (the left-rail video is much clearer). If your right rail is shimmed as Gene stated, then perhaps it needs to have a shim removed. Or is it possible that the right rail is flexible, so you get different results each time?

Regards,

-Jeff

[Martin Overberg]

There is something like a light source mounted on the head. The weight of that part may twist the gantry when the head is in the middle of the gantry, which is the weakest position. I recommend to repeat the test with the light source removed.
Of course the gantry itself can be warped, too.