Starting a couple months ago I started getting an issue on my Glowforge where cutting and scoring passes sometimes don’t work at first. When this happens, the laser tube is illuminated with the normal purple glow but I don’t see the laser on the material for the first part of the cut. As the tool head progresses along its path, the laser gradually becomes visible and begins to cut. To me this looks like a focus issue – like the laser is initially out of focus but comes into focus while following the path. But the strange thing is that it only seems to happen during cuts & scores (not engraves). Typically it will apply to only one step in the sequence when I have multiple cuts and scores. If I try again it will usually work.
I’ve cleaned the lens, 2 windows, and mirror and reseated them multiple times with no change to the issue. I’ve confirmed the honeycomb is sitting flat. Since engraves are working reliably it sure seems like a software issue, not a hardware failure. Seems to me like the focus is way off at the start of cuts and gradually gets closer to correct as the cut progresses. I’ve reproduced the issue with both manual focus and auto focus.
Does anyone know what could be causing this? Any ideas what I can try next?
I don’t think it is a focus problem because once the focus has been set, the lens does not move and the focus would not change. More tests are needed since you state that only one operation in a print might be affected, and upon retry, it isn’t affected. Does the same section of the print fail if you reorder the operations? Does this happen in a particular place on the bed? Does this happen on your initial print of the day and then not again? I think software problems would repeat consistently, but a short in a wired connection (hardware) would be more apt to be intermittent.
Last night I started putting all my cut operations before the engraves and didn’t see the issue for my last few prints but that could be luck as the issue doesn’t happen every time. I’ve experienced the issue in multiple parts of the bed.
I haven’t established a definite pattern. A section will fail and I’ll rerun the whole print in the same spot and the second time it will work. Yesterday it happened intermittently all evening (11 prints).
If you don’t think it’s a focus problem what else could cause the cut line to fade in like this? It would have to be power then right? I would expect I would see a power change in the brightness of the laser tube but that’s not been the case – when the issue happens the visible purple light coming from the laser tube maintains the same intensity.
Probably my next step is to disassemble the head and try to look for damage or mechanical problems in the focus mechanism unless anyone has a better idea.
I never look at the laser tube, only the point of the laser beam hitting the material so I can’t comment on the brightness of the tube. It does, however, seem to me that the power is the problem rather than any fault with the focus mechanism. I sincerely believe that disassembling the head would be pointless.
I suggest doing some tests with typing paper elevated to near the max height of .5". If you watch scores and cuts on paper and there is no beam on the paper, a temporary power failure would be proven. There is no way that a failed cut could be a focus issue in this test without leaving some sort of mark on the paper.
I had to run out, but to add to this - the laser is an instantaneous device - capable of being pulsed at thousands of times per second. Although it could possibly be related to the tube, it is highly likely it’s the power side of the electronics that provide the (substantial) energy to it.
Either way, it’s not something you can clean or wiggle. It will almost certainly require replacement.
I extracted the logs from your Glowforge to investigate the problem, and it seems like your unit is running into trouble during the calibration step in which the lens focuses inside the printer head (you may hear this when it’s happening - there’s an audible “ticking” sound as the lens moves up and down in the head).
They had me go through the normal cleaning steps (which I had already done) and then also suggested I disconnect and re-seat the ribbon cable. They also said magnets to hold materials down can affect this (though I wasn’t using magnets for these cuts).
I (rolled my eyes a little bit and) did all these steps again and I can’t reproduce the issue. I’m glad it’s working, and I’m glad to have a little more details as to what was going wrong, but it’s not as satisfying as finding a smoking gun.
