Advice for plywood cutting

[Marc Nicoloudis]

Hello All,
I always appreciate all of the help I receive on this site, Thanks!

Ok, Here goes,

I have two products that I have been using 6mm baltic birch for, but cutting has been inconsistent, and I am left with alot of waste and frustration by the end of each day. I have a 30 watt laser, 2" focal length, and have tried as many different ways as I can come up with for repeatable cuts. In focus, out of focus, double passes, focusing half way in, frequency adjustment, etc.

At this point, I believe I am just too close to the maximum output threshold for repeatability. I see a couple of different options,

3/16" Birch plywood- Seems a bit hard to come by, and I am at at least 3 times the cost of 1/4 inch

Purchase a planer to bring the 1/4" down a bit

Use LDF and veneer my own stuff

Find some Italian Poplar ply in 3/16"( not sure if it exists)

What would you do in my situation?

A new laser is not an option!

Thanks, Marc

[Henri Sallinen]

The problem with cutting plywood is probably the glue. Most of the plywood sold has what's called exterior grade plywood (black glue) and you should be using interior grade (white glue). The exterior grade glue is very hard to cut with a laser and leaves a very black cut line. If you can find interior grade plywood, then you might be getting better and more consistent cuts.

[John Bion]

Hi Marc,
to be honest, I would have thought that cutting 6mm BB ply with a 30w would be more frustrating than watching paint dry. The Poplar Ply is great, depending on what sort of product you are making; it neither as strong as BB nor as pleasant to the eye, it also can 'lift' sometimes when painted with water based paints, which means an extra bit of sanding. Poplar will cutt very mich quicker and cleaner.
I cut a lot of BB ply and even at 100w I get waste due to resin spots etc in the board, this has to be budgeted for.
the previous poster is correct that you need to get the correct glue.
where in the world are you?
kind regards, John

[Mike Null]

And if you really want to pull your hair out try planing plywood.

[Bert Kemp]

Yea your not going to plane plywood, also your going to have a real difficult time with a 30 watt trying to cut 1/4 BB my 40watt can't do it consistently I almost always have to use an exacto to cut out some of it.

[Matt McCoy]

Marc: You are probably at the limits of your laser to be able to consistently cut 1/4" BB plywood. As mentioned, the adhesive plays a part in the ability to pass through the material as does dense spots (knots) lurking in the ply layers. Depending on the complexity and size of the shape you are cutting as well as the amount of work you intend to do, it may be worth considering a small CNC to mill your project.

I use 40 W CO^2 lasers to cut 1/4" BB plywood which can be tricky and requires the trifecta of knowledge of your material, a clean and properly aligned laser, and luck to make it happen.

Hope this helps.

[Mike Audleman]

And if you really want to pull your hair out try planing plywood.

Rofl! I was just thinking the same thing. The veneer on plywood is the quality surface. If you plane it down sufficient to make a difference on the laser, I suspect he will already be thorugh the veneer layer and into the first glue layer. And its gonna look ugly and splinter all over the place.

I have planed it. Its a challenge and I found that if the knives are not extremely sharp, it will frequently lift the veneer layer in splinters, especially if you cross plane it which is generally a no-no but may be the case depending on length vs width of the piece and which direction it was cut from the sheet.

Not knowing the project, I offer a possible solution....

Can you cut the pieces twice from 1/8" (3mm) play? And then glue up the pieces to make them 1/4? You will actually end up with twice the ply layers that way but you will have to pay attention to cut direction so that when you glue them up you are gluing cross grain pieces. You would need to cut one piece lengthwise from the sheet, the other crosswise is what I mean.

[john passek]

Have you looked at the Hardwood Collection Rowmark has, it's pretty nice stuff, not sure it will suit your application, might be too pricy but if you need quality material you can charge more.

[Michael Kowalczyk]

Mike Null.... on that plywood planing...Sanding would be a tough one also.

Marc, I have a 60 watt Trotec and 6mm is not that easy but I charge accordingly when doing it. On my system I have to cut at 100% power, .55% speed and 5000 htz. Some of the 6mm ply has some knots in the middle core aka the "Black pooof of death" even an exacto won't work .

Your 30 watt may not be pushing 30 watts any more. How old is it? have you had the power level checked? As someone above mentioned, is your material interior or exterior glue? Is it Genuine Baltic Birch Plywood or Chinese or some other type?

Hey John,
What settings do you use for 6mm BB?

[John Bion]

Hi Michael,
I assume it was me you were asking, but perhaps it was John Passek?
Having a Chinese laser (100w Recci), I am a little different from your settings. I use 95% power and 22 speed. I used to be at 40 speed, however with a combination of tube deterioration and trying to get more consistent results I have dropped right down. Sometimes I will have to go as low as 16 speed if the board is warped (I tape almost every board down as a matter of course) and perhaps high on the moisture content. Because of time I seldom cut more than 3mm on my 60w.
I only use quality wood from a reliable source.
I seldom use a craft knife, if it has not come cut out fully in the laser then it is almost always firewood; very occasionally, I will use a knife or even scroll saw if the job is worth it; wood is cheaper than labour in many circumstances.
I have tried sanding whole sheets of ply in my thicknesser sander when I have had a complete board not come out right, this takes time, joints will not mate correctly, the internal glues will not take wood dye correctly (patchy finish), the drum sanding scores require sanding out with a ROS.......all resulting in combo of grey/no hair and a pile of firewood after all the effort.
I do sometimes cut, say, 6mm and glue back to back to get 1/2", especially if both sides require perfectly matched up engraving and my laser is hard pressed at something like 1/2".

Sorry - long answer. Sort of touching on a few posts in this thread.
Kind regards,
John

[Kev Williams]

Question: Any advice for plywood cutting?

Answer: Yeah, get one of these--




--honest!

My BIL who works with me, he has a Gravograph LS800 30w laser at his house, and he just bought a nice scrollsaw, an Excalibur 30k-- He's only had it a month, he never used one before he got it, and he just said to me as I'm typing this "I love the it!"

With very little practice he made up the pieces in the pic. He used the laser to draw the cut lines, and to etch the surface of the wood, and did all the cutting with the new saw...

[Marc Nicoloudis]

Ok,
Thanks for all of the replies. Laser has just been recharged and is @ 42 watts nominal(?), 50 watts peak. Not quite sure what they meant by this, but that is what the data sheet said. I guess planing is out of the question. So far I think my best bet is to laminate 1/8" together. With all of the wasted time with the 1/4", I could have easily done a bunch of glue ups. I guess the good part about it is that the sizes will not change, and I can plan ahead.

What was not touched on was the LDF(Light density Fibreboard). Is this the same thing as ultra lite? This is not a structural project, so even if the LDF that has been laminated, isn't as strong, it would still be aesthetically pleasing. What do you think?

[Kevin Gregerson]

Doing that stuff I'd recommend pushing minimum 75 watts on the universal tubes 150 watts works better with cleaner edges and maxes out at 3/8s with the unfriendly to laser glue. Usually it's a higher silicon content glue that does this as the glue absorbs the heat really really well before it finally ablates away. I've had to do a fair amount of testing with that ply and I agree with the poster above, the glue being used makes a big difference. Try to stay away from the outdoor ply's if you can help it. They use them for the nicer woods because they keep the wood straight when cutting it.


-Kevin

[Larry Robinson]

Try going to HD and get some "SandyPly" it cut very nicely, but not as strong as BB.

[Marc Nicoloudis]

Larry,
Can you comment on the engraving aspect of Sandeply? Looks like I will have to buy a 4x8 to test. Thanks, Marc