I’m getting a bit discouraged with camera alignment. I have an 8mpw-120 Lightburn camera mounted 12.5 inches above the bed. Windows 10 computer. I have tried doing the lens calibration myself as well as the lightburn one for my camera. Camera is mounted solidly above center of the workspace. Not on a hinged door, it is mounted directly to the top of my enclosure.
I get terrible drift. I again did a camera alignment using the largest space I could get with the standard Lightburn lens calibration. I drew a cross and burned a circle, square and x centered on the cross I drew and got the best alignment I’ve ever had. I did a bit of corrections for offset in the camera control panel and was able to do this.
This was taken with the lightburn camera after that burn.
This is the same burn. It was repeatable.
Very first project after that I get this.
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Not even close, so I again drew the cross with the same pattern. This was done right beside the project burn.
Lightburn was not closed the only changes were thickness of project, cardstock vs 1/8" plywood. I did shutdown the laser and restarted between the first tests after the calibration and the beginning of the projects.
Is the distance between the lens and the material changing due to the thickness? If so, you will get drift. The Camera alignment is only good for one distance between lens and material.
Distance is usually maintained by having a movable bed that raises and lowers to achieve focus.
Here is the results of 11 more tests on the same cardstock as the original good results were done on. Numbers are the order that I did the tests. There seems to be some correlation on where I started each test from. All laser movements were done with the move tool. Most of the time the laser won’t go home from origin without making one jog toward home first.
This is the view from Lightburn camera faint lines are the burn.
Here is the same thing with external camera showing offset better.
Further testing I have found that if I burn something, starting from home position, somewhere near the center of the bed alignment is pretty much dead on. It seems the farther I get from the center of the bed, the farther off it is. If I start from any other position, including origin, it will be off in varying degrees. Is there some solution for this?
You didn’t address the question of changing distance to lens. Is distance from material to lens ever changing?
If I’m understanding you correctly you should be able to address this with the width/height adjustment in Camera window. First correct for scale, then use X and Y shift to better align.
I thought I addressed the lens distance by doing all of the tests on the same thickness of material. I wouldn’t think that 3mm should make that much difference.
I don’t think that will but, I’ll do some tests with it.
Ah. I didn’t realize that’s what you were attempting to do. In that case, be aware that you’ll be dealing with 2 discrete and different issues: base alignment, and alignment issues from material height differences.
Depending on current distance to lens 3mm could make a surprising amount of difference. Note that this is a fundamental problem and won’t go away no matter how much alignment you do at the base level.
Can you confirm that the last set of tests were done with the same material that your initial cameral alignment was done? If not, it won’t be valid.
Can you elaborate why? I might be missing something.
I think I have it. Main problem was y was not square with x. That showed up when I made a square almost bed size. Using a dial indicator I was able to get the gantry square within .002". Subsequent tests have a 16" square only out .0715" with center being dead on. I can live with that.
I ran the same test on 1/8" thick material. That resulted in a slightly smaller square which, makes sense, when you think about it. Changing height and width to -5 again got things to line up.
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