bought an 80w Chinese 70x50cm laser and have an unknown problem with mirror alignment. With another laser never been before any problems. Not the first time aligned the mirrors for the laser.
Tube to Mirror 1 - The perfect dot in the mirror center.
Mirror 1 to Mirror 2 - Also the perfect dot in the mirror center in both positions ( near and far)
Mirror 2 to Head. There is the “fun” part. When the head is in the bottom right position, the beam hits center, in the bottom left, the beam hits the same dot (no vertical and horizontal movement for the beam). If the head is in the top left beam also hits center (the same dot as the bottom left). When the head is in the home position (top right) beam goes up ~3-4mm from the center. And impossible to align mirrors correctly in the whole working area.
Where is the problem and how to solve this? I’m attaching a few photos.
Just speculaing but the simplest explanation is that you have a low spot (by ~3-4mm) along the right side rail near the homing position. Have you checked the laser for tram? Or for at least obvious drop in height at that location or possibly a bend in the rail?
Thank you for your response. I’ve also had this idea. But I’m not sure that problem is here. I measured a gantry from different spots in the whole laser frame. I believe 3-4mm misalignment or bent rail will be visually visible for that much. Both sides of the rails are at the same height. Also, I tried to adjust the right rail, but in the opposite way. Aligned the beam in-home position, and bottom right rail raised up (whole rail), that has no effect for the beam because the whole gantry with head mirrors rises up parallel and bead hits the same dot no matter how much you rise the corner. This way can work when mirror 2 will be mounted separately from the whole gantry. I believe the black magic of this situation is somewhere else. Or maybe I’m wrong.
I’m sure it’s a challenge to build a machine in perfect alignment and ship it long distance while maintaining alignment. Not sure what to do if something is warped but I your willing to spend the time, you can shim up the rails, if they are out of plane.
Keep in mind that the goal of laser alignment isn’t to hit every mirror in the exact center but to allow the beam to exit the head without hitting anything, over the depth and width of the bed.
Not sure of the meaning. M2 has to follow the Y path in sync with the gantry. How could it be separate from the gantry?
You can be sure the beam is ‘flat’. If you move left to right at low power you will see the ‘dot burn’ slide up to it’s final position. Probably not a bent rail or guide.
My only concern is that the ‘upper’ burn on the photo looks like the beam is being clipped or hitting some obstruction.
If the beam doesn’t hit the center of the lens, then it will exit the lens at an angle. You can see the angle in the ‘cut’. Much like when the head is not ‘trued’ vertically to the bed. If that angle is minor, proceed and have fun…
I’ve dealt with a few of these and all of them seem to have a ‘bad’ corner. You would have to look at where the beam hits the material to determine the actual ‘error’ and make a determination of if it’s reasonable. A couple mm on M3 is probably not an issue. Closer is better, but…
Thank you for your response. But shims under the bad corner doesn’t solve the problem, I tried that. But i will try a few more options tomorrow. At this time the beam hitting air nozzle in home position and when cutting there is 2 lines, one is true cutting line, another is like reflection and doesn’t cut thru material.
“Not sure of the meaning. M2 has to follow the Y path in sync with the gantry. How could it be separate from the gantry?”
Yes, M2 is on the gantry. If you adding shims on to right rail, the whole gantry moves a little bit up depends from distance of where you adding shims, and that doesn’t effect the beam.
“My only concern is that the ‘upper’ burn on the photo looks like the beam is being clipped or hitting some obstruction.”
I moved back mirror 2, to avoid that beam hits belt tensioneer, that doesn’t help. The beam doesn’t hitting anything, but i will check for that additionaly…
I don’t know if this makes a big difference but I won’t tape my head like that. I have 19 X 5 wood disks that I use instead of the lens. then you can put tape on the disk for repeated firing.
My take is that the beam is rising up on the third mirror as you go from front to back while at the far right side. Raising the rail doesn’t help. So the angle from the second mirror on the third seems to change from front to back? not easy to fix but you could just split the difference and center on the third mirror as best you can.
just a theory but they make these rails for all kinds of applications and is it possible that they are too tight or too loose? Is it hitting spots of lubrication that cause a small change in the angle? is the belt pulling on it differently. I’m taking about mirror 2.
