I’m making ornaments on 1/4 BB and they’re cutting fine. The problem is they have a lot of very tiny cuts and require two passes but my masking keeps flying off of the cuts resulting in a lot of yellowing and even charring on the top of the wood. Is there any way to prevent the masking from coming off? I have it set to do the inside with all the cuts first and then the border of the ornament last. I just don’t want to spend hours upon hours cleaning them up because I have an order of 100.
Are you using something to apply it? You should be pressing the masking on with a brayer or something to get good adhesion.
Also, previously:
And maybe relevant:
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Thanks! I am using a spray adhesive and I always sand. Maybe with these intricate cuts it’s as good as it’s going to get as far as yellowing?
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A spray adhesive? Can you elaborate?
You can salvage that piece with 30 seconds and a sanding block. I’d go for about 300 grit but anything 220+ would work fine. You can just sand the top layer down a bit and all the smoke marks go right with it.
You don’t want to do it all the time of course but if you have just a few that are being difficult, sanding can save you.
You’re also up against a tough situation using 1/4” wood and double passes. Many adhesives lose some tackiness as they heat up, it’s possible that the extra passes are contributing to your issue (due to heating the material). Flyaway masking isn’t just an annoyance, it’s also a fire hazard — the flyaway bits can blow into the lasers path and ignite. Be careful.
If it were me I’d do two things: I’d switch to 1/8” ply and I’d use a purpose built masking material applied with a tool.
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I’d LOVE to use 1/8 but my test piece on it seemed so fragile along the scroll work. I’ve never worked with 1/4 before so I was really hoping 1/8 would work. Maybe I’ll play with it a bit more on the 1/8 and see if there’s anything I can do. The guy said he doesn’t mind if it’s breakable, he just doesn’t want it falling apart.
Just eyeing your design, it doesn’t look like it’d be too fragile with 1/8 BB. Hardwoods, yeah, that would break in a second, but ply should be ok.
It’s also not a bad candidate for proofgrade, the finished surface might be worth the cost.
If I were to make one strengthening suggestion, I would very slightly beef up the spot where the tree comes into the ring to make it tougher, you could possibly also thicken that ring if you want to be double sure. Overall though, seems like a reasonable design.
So, about that spray adhesive, I’m curious about your process if you’d care to share.
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I used the tape for vinyl masking because it’s meant for heat and has the grid which kind of helps and just some Elmers spray adhesive for extra insurance. I have to say, I adjusted my settings on the last batch and it came out a lot better but didn’t cut all the way through. I used what I normally use for 1/4 oak so I’m adjusting it slightly from there and seeing if it turns out and then I’ll run another test piece on the 1/8 with your suggestions. I’d much rather use 1/8 because it’s easier to work with and, more importantly, less expensive!
And good idea on the PG material. Maybe I’ll give him an option. I wish they had PG in passthrough size! He wanted a couple that were 3ft tall. That would help a lot!
They do for several materials.
That didn’t seem right, so I just went and looked – they do have it in maple and cherry. Maple is out of stock, but I would imagine it’ll be back in stock soon.
I wonder if your spray adhesive is actually interfering with your masking adhesive? I’d try sanding and then using straight masking material, it should stick quite thoroughly. The smoother the material is, the more it’ll grab on, I mean try taking medium-tack masking to acrylic, it holds almost too well. Sanding your ply and getting all the dust off will make a huge difference.
This is what I use, and I have very little trouble:
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If you can damp a terrycloth rag with hand sanitizer that yellow will come right off with barely a wipe, even if you do not use masking. Spraying the masking or material with adhesive will just make the places with adhesive a magnet for the gunk.
If you use 
plywood you need to be very careful not to get it on the MDF middle as it will dissolve the glue that holds that together as well.
Your spray adhesive is cancelling out the adhesive on your masking. Masking is pressure sensitive and designed to work in a very different way than spray. The solvent in the spray destabilizes the masking adhesive and, as Elmer’s spray isn’t particularly sticky in the first place, the spray particles act more like dust making what’s left on the masking even less sticky.
Ditch the spray, make sure your surface is free of dust/oils and just burnish the masking down well, an old credit card works great.
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Okay so the 1/8 was a little to frail imo but I’m going to give him the option. I broke the tiny part under the B while removing the masking but it doesn’t feel like it’ll fall apart. Just looks a little cheaper. With that said, I think I figured out the 1/4. I used masking tape which is a pain to remove front and back. I’m going to see what the price difference is for PG and offer him all the options if I can figure out the math involved. 
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You can use gorilla tape to help remove the masking quickly, but with something so fragile, you’ll want to make sure it only sticks to the masking and not the wood.
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It looks like you already have your answer, but I have no problems with masking coming up using two passes on 1/4" hardwood. I use a cheap masking material from Sign Warehouse.
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