PG cuts failing, power seems ever so slightly inconsistent

For a while now my forge has been failing to consistently cut proofgrade material. It also manifests when settings that had reliably been cutting other materials quit resulting in clean cuts.

Since an early failed cutting job, and learning the importance of material being flat, I’ve been using rare earth magnets to ensure all materials are firmly held flat to the tray. I’ve been like Rick in that short where he shows Morty “True Level”, so I don’t think that’s the issue.

The first time I noticed this seemingly inconsistent power was at about twelve hours of use (I’ve loosely tracked the duration of every job on the forge in a spreadsheet). I wondered if it might be dirty interior surfaces, so I went ahead and wiped down the reflectors inside (but not the lens) despite it being nowhere near forty hours of use. At around twenty hours the problem showed up again, I repeated the cleaning job but this time it didn’t seem to work, and even pg cuts haven’t completed consistently since. They’re almost done, to the point I can take a hobby knife and trim them on out, but this is a far cry from the beautiful job the machine was doing earlier on.

Reading about similar issues in the forums, I made sure the tray was correctly seated and did a test cut of the gift of good measure in draftboard earlier today. Again it was very close, but the piece remained in the source material and a picture shows the little spots that didn’t quiiiiiite get cut all the way through.

After that test, a small job in pg medium cherry ply worked, which is what leads me to describe this behavior as ‘inconsistent’.

So it’s at just over 22 hours of use now (I know, still practically unused, I just don’t get to play with it nearly as much as I’d like), again nowhere near the 40 hours recommended for a lens cleaning but I’m wondering, might that help? It also looks like it’s really far off from the 120 hours at which the head mirror might need it, but again maybe something somewhere has just stuck to a critical surface?
I assume the electronics are pretty reliable, are there known issues with the tube that might cause this behavior?

Any guidance from the support team or knowledgeable forgers is appreciated.


Try cleaning the lenses anyway to see if it helps.

There’s also making sure the material is completely flat with either wooden pins(design floating around here), magnets, or other.

Some people also increase all the GF pew settings by 5 pews as their own default tactic.


Be sure to wipe all four optical surfaces down:

The 40 hours of use is a rough guideline; it depends on the material you have been burning. Acrylic hardly puts out any products while draftboard/mdf will dirty up the optical surfaces in no time.

And although you’ve probably already seen it, here’s the official guide to cleaning:


@brucecooner I realized a while back the lens are the key to a clean cut. I had done a 3 Hr 30 min engrave and when it went to cut it out it didn’t go all the way through so had to finish it of from the back side with an exacto knife. Now i clean the lens after I shut the GF down for the day. Haven’t had an issue since, knock on wood…


I had this happen after 10 ish hours. First it was material warp so I pinned the material down. When it still happened, Cleaning the lens and mirror fixed it


I have had the stuff dirty up even in a long cut/ engrave. I did a very small job that went well so I did a big one that involved a lot of engraving and cutting on oak plywood that I know to be very dirty. Buy the end of the 3_1/2 hour cut it was messing up badly.

The head fan had all but quit, it was smoking every where and the lingering smoke/ Now dirty lenses ment that the cut was not only not going through but was charring the top badly as the cut would often burst into flame while at the cut though there was no continued burning.

I am not one of the lucky Snap mark users yet but even then I had to just watch and try to fix later as whatever happened the wood was not going to be usable unless it continued as there is no restart in the middle of a cut.

So do not look at the time taken but at how dirty stuff is. If the top window needs cleaning then probably everything else does too.


Yes, 40 hours is a recommendation. It all depends upon what kind of jobs and materials you are doing. If I do long deep engraves on acrylic, things can get dusty. Some woods seem to smoke a bit more than others.

Not saying that this could be the only reason you aren’t making it through, but it is a possibility.

Other issues are exhaust flow. If the exhaust is blocked up, the removal of smoke and dust can be impeded and that can affect how much power reaches the material. Most of the time you notice it from smelling some back flow during a print, but I’ve noted it can make a difference in ability to cut through materials.


Not cutting through all the way is always my first indicator that my lenses need cleaning. 40 hours is a (very) rough estimate; you have to be proactive with the cleaning if you don’t want to waste materials. I just automatically clean things before starting a new job, now; it saves a lot of frustration.


Thanks everyone for the feedback.

I’m being pretty watchful of the material laying flat. The unit still vents very well, smoke doesn’t seem to linger inside.

But it sounds like others’ experiences indicate less-than-clean reflective surfaces are an issue, and that the recommended cleaning intervals can vary.

I didn’t mention in my original post, but the camera in the lid isn’t reading the qr codes on pg material correctly every time (despite wiping the camera down with each cleaning I’ve done), and that would seem to independently indicate smoke buildup is an issue.

I primarily work with pg plywood, but there is a small amount of mesquite in the mix, so that may be reducing my cleaning interval a bit.

I picked up some lint free optical wipes yesterday, and will try to de-grime everything today.

Thanks again for the info.


You have a good source for Mesquite?

Thanks for the tips everyone.

Thanks for letting us know. I’m sorry that your prints are having trouble cutting through.

You can follow the instructions in the cut-through troubleshooter, to be sure not to miss anything.

Once you’ve inspected and cleaned, please try another Gift of Good Measure on that Proofgrade Draftboard and let me know the result.


Not to get off-topic, but we’re going to need some pics of that in #glowforge-project-examples. I love mesquite either finished or for bbq (just not the dang live tree lol).

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My “source” is mainly the tree in my backyard. :slight_smile:

When it’s time to prune it I set aside the more sizable pieces.

I do keep an eye out for downed branches around the edges of parking lots or along rural desert roads. If you live in the southwest you can probably ask around and find a friend or a friend of a friend will have a mesquite and donate some trimmings when it’s time to prune.


My work with mesquite isn’t very substantial, mostly just producing necklace pendants from trimmings. At first I was woodburning some of them, but the forge does an incredible job engraving in mesquite, so I’ll have to take your suggestion and share some of my results.

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Thanks for the quick feedback. I did have time today to remove the head and I can see some bits of what look like ash or smoke on the lens, but errands and engagements kept me from getting to do any cleaning. Hopefully tomorrow after work I’ll have time to go through the checklist you shared.

I used to live in Tucson, but I was hoping someone was selling 1/4 slabs, If one had the ability to cut wide slabs and plane them I would be grabbing the mesquite firewood and be doing so. Unfortunately in Tampa it is almost all oak. In Miami such trimmings are often mahogany :slight_smile:


Apologies if you already know this, but there’s the fixed lens too along the inner left side of the unit that needs cleaning too. I didn’t realize that at first (duh, I should have), but I only cleaned the lenses on the head unit. Finally I watched a video and realized I needed to clean one more lens and cutting power went back up.


Technically there’s only one lens. That’s the one in the head you need the special tool for. The other two are mirrors. They make the laser beam take a couple of 90 degree turns that result in it going from pointing out the left side to straight down perpendicular to the bed.

The mirrors have windows in front of them to help protect them and makes it easier to clean them without scratching.


Okay, optics then:slightly_smiling_face:


:slightly_smiling_face: old school lasers have an additional mirror. GF’s gantry mounted tube eliminates one of those & the pesky alignment necessay as a result.

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