Uneven Laser Power

I have been using my beamo for about 5 months and overall it is great. that is if I put my item near the top left corner.

If I try to do something larger that spans the entire inner honeycomb (see pictures), it is clear that the power setting is not the same at the top left vs. the bottom right. You can see that the lines are getting thicker so this leads me to believe that the lenses are not well aligned???

I did try to calibrate the lenses as per the manual and from what I can tell when I do the laser pulse, the dots do align well on the tape.

I would really appreciate it if people can point me in the right direction.

Try measuring the distance between the laser head and the bed or workpiece. You might find that it’s not equal across the entire bed, which easily results in uneven cutting.

Playtester is correct… your bed is not level with respect to the travel of lens. That doesn’t add anything to what Playtester said… however: 1. You can remove the bed and with quite a bit of work, remove the chain and adjust each of the 4 corner posts to adjust the bed height; tedious. Or 2. Using NON-flammable shims (metal washers, metal shims, etc.) glue them on the lifters or on the bottom of the bed at the four corners to level the bed with respect to the lens. I followed the tedious route until I read someone (to whom I’m grateful), somewhere on this site mentioned the far easier method.

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… AND, make sure your media is flat… there is always the chance your sheet of plywood is not flat/level causing variance in distance from the lens. Just a thought.

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… AND there is some chance that your mirrors are not aligned such that the laser is not hitting the same spot on the horizontal focusing lens as your lens moves across the field. I would try leveling the bed first… but if still not satisfied with the results you need to align your mirrors from beginning to end in order to ensure at every point across their travel, the laser hits the same point (hopefully the center) of the horizontal focusing lens. You will definitely get different results if your beam hits the center (thickest part) of the focusing lens at the top left yet hits nearer the edge of the lens/lens opening at the bottom right. Same effect, only more pronounced, than a not-level bed.

Hi, Thanks a lot for your reply!

I did some experiment to try to determine whether the poor cutting is caused by the uneven bed or the mirror alignment.

I took the same small piece of wood and put it in all 4 corners. Each time re-adjusting the laser height for that corner of the bed.

TL = top left, TR = Top Right, BL = Bottom Left, BR= Bottom Right
You can see that the bottom right is the only one that has issues. At least this led me to think that the leveling is not the only issue.

I tried to do the mirror alignment, and i follow the instructions, firing the laser when its close then when its far along the different axis and they seem OK.

However, when I do the following test, the laser doesn’t hit the same point on the mirror.

I put tape on the opening above the laser head, then put the the laser in position 1 (middle left). Then do a pulse. then move the laser to position 2 and do a pulse, the two dots line up almost perfectly.
But if I place the position (1) then pulse, then move to position 3, they don’t line up and the 2nd dot is 2mm lower.

I did of course try to align the other mirror by only moving the head along the y-dimension and those line up very nicely as well…

I thought i would post this incase anyone has any other ideas on what i can check. Or maybe can point me in the right direction with the symptoms i am experiencing.

One thing i will say, in my screenshots, you can see that the vertical lines of the laser are not as sharp as the horizontal lines… Not sure what that means either.

Anyway, thanks a lot for your reply.

You did not indicate if the initial tests at the four corners required height adjustments and, if so, how much for each corner. But it sounds to me that you have both bed height adjustments and mirror alignment issues to resolve. Consider the following: if the mirrors aren’t aligned such that the pulses on the tape are 2mm apart; and let’s assume that the last mirror that redirects the laser from horizontal to vertical adds another 1 mm of variance. You more have 3mm off beam variance at your bottom right corner where the beam is trying to come out if an 4mm hole… doesn’t take much for part of your beam at the bottom right to be obstructed by the lenses holder as well as the lenses being less focused, as well as your beam having slightly different travel distances at the bottom right after exiting the final mirror and lens. I fought all this and did bits and parts of all adjustments several times until I understood that with lasers, there is no “getting it close”. If you remember, you do all this (bed leveling/mirror adjustments) just to find out if your laser tube is “level”. So you level the tube and then have to start it all over again. I finally invested the 4-5 hours and ended up with far superior results. First leveled bed; then aligned mirrors, then determined/adjust tube to be level with the path of the laser beam, then recheck bed height, then align mirrors (again), paid particular attention to that last mirror and the lens to get a perpendicular beam path to the bed with the beam exiting the center of the lens shroud so it doesn’t contact the side. As a quick check you can measure table level at top left/bottom right; put tape on mirror at top left and compare with tape at bottom right, and then take a pulse on some scrap at bottom right and without letting lens go home use a square and estimate if final beam was vertical AND exited through center of lens shroud. Any variance anywhere will cause your problems. I wish Flux would be this thorough and direct. Leveling the tube is a matter of shins, leveling the bed can be the same, aligning the mirrors is simply tedious.

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Hi Shayansh. I have the same problem. Did you finally find a solution? Thanks.