This is rather an extreme example (The small bits in the center burned ayay completely and part did not cut through at all.) Some folks hsve shown lights through the wood to find such places but I have not had a light capable of the job for the wood I have had. If I had that problem I do not buy it a second time from that source. And if not specifically sold for laser then the question can be considered open. Even as bad as that piece was, I did get a bit of work done if awful still managed to not get the worst bits in important places.
So not sure if anyone will see this but picking this topic backup. I realize the cut issues remain from all diff kinds of materials, but something I didn’t mention in the original post was that there is a hell of a noise coming from the glowforge when the gantry moves up and down (not the print head part) like a bad vibration of sorts. I am 99.9% certain this noise is new and probably started the same time the material cutting issues arose. Not sure what to investigate, the y axis belts on each side?
Why don’t you post a picture of the window under the left edge, and a video of the noise (upload it to YouTube or Vimeo or equivalent and post the link here). That way we can help based on actual data, not our assumptions based on your words.
Attached are the images of the windows. Attached is example of it not cutting through, this is on draftboard now. So I do not believe still it is a material issue. Three different types of material (1/4" walnut plywood meant for lasers, 1/8" cherry wood and now 1/8" draft board. ). All materials were flat and or/pinned flat and usually cut success happens by slowing the speeds down a tad which I have never had to do before.
This is after cleaning every lens and trying a cut too.
The noise was still there slightly after I tightened the belt on the right. I couldn’t get a good vid of it because it was far less prominent. It sounds like a rattling, vibration almost. By hand moving the turned off glowforge gantry I can hear a noise that is new, similar to the vibration I was hearing when running. Did post that vid to vimeo here: Glowforge sound on Vimeo
I have not, I have taken the print head and assist fan off before…not the other gantry though since it has the laser tube on it I was nervous to do anything about it to investigate. Not sure how I would safely do that, could that be causing the no cut through issues?
I have seen a mess far less than those two dots stopping a complete cut through. I had the cut through issue and those windows were my first thought. Looking, I could not see the slightest crud, but as I had the lens wipe out and opened rubbed it down just for luck and was surprised to see it slightly brown , so I wiped both windows and the cut through issue vanished.