Inconsistency in cutting with same setting and material

Im cutting lettering out of 1/4 inch birch plywood purchased at lowes. Calipers puts thickness at 0.2 with masking tape. Setting : Cut. Speed 145. Full power. 1 pass. I finally got the thickness of uncertified material at 0.3. SO 0.3 in comes in setting for focus height. The first 2 words cut out so perfect. Amazing. Now the same setting and same piece of plywood will not cut through. I have this happen on other occasions. Ill reboot the glow forge. Cancel print> reload the design> manually re enter the manual settings and have a correct cut. This time not cutting through x3.

No particles under board. Crumb tray clear. I have cleaned the lenses and mirror.

What am I doing wrong to cause this inconsistency

It is not you or the Glowforge. Regular birch plywood is not made to the same standards as real Baltic Birch. I tried kicking up the power just to get through and got this…

If you are cutting and get a bad cut just let that piece go and try again at a different place, some places may well be laser proof.

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Yeah, it’s more likely your plywood than your GF. As @rbtdanforth suggests. Sometimes there’s a void, glue spot, whatever weirdness. Big box store material that isn’t specifically for lasers is just not very consistent.

You can avoid some agony by gently checking to see if your piece cut all the way through without moving the cutoff part. If your piece doesn’t lift clear, close the lid and run the cut again. It’ll cut in the same spot even if the camera view tells you otherwise.

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A good idea in some cases, however in big box birch plycarp you could toss it all on a bonfire and some would not be scorched.

Support can’t help with non-Proofgrade materials. I’ve moved this to an appropriate forum.

This is one reason they have their materials available, for consistent results.

Your settings aren’t far off what I use for 3/16 underlayment plywood I get from Lowes, so it’s not surprising to me that it doesn’t cut 1/4" reliably.

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Yeah and you would expect more out of a $6000 40w laser.

The problem isn’t the machine. It’s your material.

My machine is almost three years old and cuts proofgrade material using default settings perfectly, every time.

It also cuts non-proofgrade material just fine as well, with settings I refined over time. Most recently, 0.59" pine pickets in a single pass.

Let’s just say. Same piece of birch plywood. 2x4 ft. I cut down and get 4 pieces out of it. On 2 pieces with same settings cut perfect. Them the other 1-2 pieces will not even reach the bottom layer. Not certain different places or voids in material. It does not even score the bottom layer.

Oh and something else that makes me curious and makes me wonder what I’m doing wrong. Is I’ll load the same piece or plywood in and able to cut a smaller design in the unused part or the board.

Yup. Material can vary that much even just over a few inches.

The first reply to your post shows the kind of stuff you can encounter - although I’ve never had it that bad.

My experience with Birch from Home Depot is pretty spotty. Baltic Birch I get from my local Rockler is much more reliable/consistent. There are many other sources online, but I don’t use enough to warrant ordering from them.

I did this all over in the 4x8 sheet I had cut down. As I mentioned some perfectly good places were ruined because someone used that area to empty the brush. I kicked the speed way down to the point it burned away the small details in the center of that piece, and still it did not cut through. In another piece the carp was the size of a dime and I managed to cut it but it popped off leaving a crater and ruining an otherwise good piece.

I have used real Baltic Birch since and it is like not even a related wood.

And some not

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Ok. Thanks for all responses. I really appreciate it. Settings that work are 0.3 thickness. Speed 140. Full power. Seems to be my magic numbers.

I think most of my issues was when I had to refresh the bed and manual focus the camera. Seems to happen Everytime. Until I learn another way. Cutting the same job, same settings, same materials I have to shut the forge off for my bed to refresh and the auto focus to work. The refresh bed option is unselectable after the j oh is completed. It takes more time. But I’ll figure it out

What browser are you using? The fact that you can’t select refresh bed image or set focus after a completed job is not normal in my opinion. The only time those options aren’t available to me is when my machine is offline.

Latest version of chrome. I have Mozilla also but haven’t thought maybe a browser issue. I’ll look into that

Chrome works best for me. If you lift the lid of the Glowforge does it go into scanning mode and refresh the bed image?