What ply to use

Hi
I have a beambox pro , the specs say I can cut 8mm, yesterday I bought some 4 mm ply , in order to cut it I had to make 2 passes of fairly high power and the edges ended up so burnt the job was no good .
My question is , do I need to buy special ply if I am going to laser cut it???

Yes, maybe (isn’t that “always” the answer? “Yes”, “Maybe”?). Sorry, levity, but not at your expense. Start at the beginning:

  1. Did you run all the mirror alignment and focus adjustments. What you describe more likely indicates mirrors out of align (and you are likely to have to do it 2 or 3 times before you really get into the ‘swing’ of how to do it well) and the final adjustment for focus.
  2. Is the bottom of the focus ring on tight, with the focus lens oriented correctly, and you start it at exactly 12 mm between the bottom of the lens casing and the top of your plywood? (I’ve also use 10 mm before to just as good and sometimes better results).
  3. Is your platform level for a larger project? If you have a, say 3mm difference in height between one side of your cut and the other side then your 8mm cut capability becomes 5 (actually, probably more like 4mm)
  4. Did you purchase, use, QUALITY plywood and preferably a softwood plywood. Lots you can be told here and you should read a lot about it but suffice it to say, soft wood, all of similar density, with even plys, and MOST IMPORTANTLY a quality, laser friendly glue evenly spread between the plies makes all the difference. Yes, lots in there but don’t fret it… find a reliable laser plywood source and let them fret all these details.
  5. Make sure your “graphic” sent to cut/burn is in “black” (different colors can mean different speeds/power levels if not careful), and ensure you pick the correct speed and power level for the job. BUT don’t be afraid to experiment. Me, I have a half dozen different layers of ellipses, squares, phrases, that I insert before the layer(s) of my real work that will be cut outside or on the trash parts of my project. First time or two I let it cut or engrave nonsense in the trash (throw-a-way) parts before it gets to the stuff I care about. Because EVERY piece of plywood is a little different, its good practice to make sure “these” settings are right for “this” plywood. So, if I have a circle I cut out and discard, I first have it cut a couple ellipses or squares inside that circle to make sure they actually cut and drop free before I let it get to the layers of my actual project. Sure is a better feeling to know that what I want to happen will happen before I get to the “money” job.
  6. Something I do that helps me, but I’m not exactly sure I should recommend it, but I tend to prop my workpiece above the bed with a few 6mm (height is not really important) shims. This way when I cut something, it drops below the surface when the cut is complete. Much easier than guessing if I cut all the way through. It also seems to help with the underside not scorching so bad since the laser/flames go through to the table instead of stuck between my project and the table. Finally, it gives a clear place beneath my work for the smoke to be drawn out to the back instead of getting caught up in the honeycomb just below my project. Of course, you need to be careful with your shim placement so its not on a cut line, your shims must be all identical heights (not really a problem if you cut them from the same material), and you need a bunch because you will cut them and need to discard them at some point. Why do I hesitate to recommend this? Because I’ve never seen anyone else recommend it and so I’m not sure there isn’t something I’m missing. JUST BE SURE to do your engraving (at the right height) before your cutting and the project drops and now you’re not focused for engraving. ALSO, be sure your material is not so large/flexible, that you introduce bend and different focus heights across your project. I usually place shims at the 4 corners, and a few at points where I am not cutting through the material and which also is not part of the project (because remember, I want my project to drop down freely when cut through. I’ve yet to have problems with that last little bit of cut bending or distorting before I cut that last few mm and it drops… maybe its because I’m using light-weight materials and generally smaller projects. But it works when cutting 12” x 16” solid pieces out of 1/4” MDF.
    Hope this helps… I’m just a tinkerer so please use your common sense before adopting any of these ideas but Yes, you should be able to cut 6-8mm quality plywood (try maybe MDF) in one pass with minimal charring.

I should add for the sake of #1, above… no machine arrives with mirrors perfectly aligned and the focus exactly right. Oh, it may be close but I can almost guarantee you that if you carefully run the adjustment routines you WILL find that you adjust something. Now, the first time or two you may find you didn’t do it “just right”. This is something I find you must get a “feel” for… practice and familiarity are big factors. My personal recommendation… Get the machine out in the middle of a room so you can get to all sides. Get a soda, lots of tape, a couple different wrenches and screwdrivers (better than what they give you), a stool so you are comfortable… and go through the process step, by step, by step. When you are done experiment with an engraving or three and a cut or two. Then go back and do the whole thing all over again. Yes, I believe this wasted 3 hours of your life will pay off in a much more quality work product and you will learn tons about the machine.

I should also clarify that for my money… start by getting the bed dead level based upon the bottom of the laser focus casing. That took me 90 minutes the fifth time I did it… its not easy, not fast, but critical. Aligning the mirrors now takes 45-60 minutes and I’m really practiced at it now (I think). Cleaning the focus lens last adjustment and making sure I have a reliable 12mm focus measurement between the bottom of my lens and the workpiece takes another 45-60 minutes.

I abandoned the acrylic 12mm measurement between the project and bottom of the lens they provide. I took a 12mm thick rectangular block of wood and from 2/3 or the length to the end cut it at an angle so it went from 12mm thick to 6mm thick parallel to the table. I put the cut/angled end under the lens case and raise the table until the other end just raises of the workpiece. Back it off 1/16th of a turn and I’m at the right height. The real magic is I can get this exact height by cranking the table up or down until the solid end raises/rests on the work piece. Much, much easier than the old acrylic and ‘am I mashing it into my project’ while cranking the difficult to crank table. Within reason, the longer your rectangular piece the more sensitive is your measurement.

I had this same problem and how I solved it was to experiment with faster speeds, lower power and more passes.

With one pass, running full blast and slow will set the wood on fire, while moving it faster will become less precise but also won’t cut all the way through.

On a job I ran today I believe the settings were 45% / 35mm / 30 passes. (I ran it yesterday at 45% / 30 / 25 but didn’t quite get it) It still didn’t cut all the way through, but enough to release it and then sand. On my next run I’d likely try 45% / 35 / 35.

Reading the other reply I realize I could be recommending a totally wrong solution, but I’ve also never adjusted my mirrors or basically done anything to the unit out of the box.

I’d love to run the adjustment routines… how do you find out how to do that? I’ve seen the calibration screen but there’s no documentation and it doesn’t seem to do any good when I guess.

See

https://support.flux3dp.com/hc/en-us/categories/360000121176-Beambox-Guide

And look under maintenance and optical alignment. A general search of the flux site now (not two years ago) provides lots of good info. Recommend you spend a day reading it all. And once you do that, keep a list of items you want to follow up with on the web… but the most recent BeamBox user manual and the helpful videos are not bad… not always great, but if you pay attention to the details it’s not bad.

Again, I’ma tinkerer… not an expert. But I’ve dealt without almost every problem I can imagine so there is experience and hard earned knowledge informally gained/learned under fire I suspect.

cheers,
Jim

Something I found helpful… place one piece of tape (longer than wider) vertically on the mirror in position 1 and label it on the excess tape (e.g., M1; P1) and take the shot. If successful (a hole in tape) leave it in place, move to position 2, place a new tape over the first oriented horizontally and label it (e,g., M1; P2) again on the excess tape tab. (I doubled over the tabs so no sticky on the excess). Take the second shot. You now have a perfect reference of one hole v the other and if necessary, you can separate them and study for fine detail overlap. I then removed the two tapes, leaving them together, and tapped them to the underside of the BBP glass… I could see them from above and underneath. I might end up with several tapes side by side for each mirror and each set of test shots as I zero’d in on a perfect overlap. I found this progression, labeling and history of all tests very helpful. I could also separate the tapes and ascertain position 1 from position 2 if it weren’t obvious. Getting my press if the laser pulse fast (small holes) tool a bit of practice. And be sure you actually pushed the button… sometimes I thought I did when I didn’t… of course, no laser pulses. My issue… not the machine’s. Frankly, this is the sort of REAL WORLD experience/best practices I wish Flux would publish. So in the meantime, we have to do it ourselves.

I’ve also done Aaron’s high speed many passes routine but observed that my cuts weren’t quite as crisp when I got above 3-5 passes. I assumed there was a little bit of “backlash” (think minimal slop when going from one direction of each step motor to the other) that over several runs made my 0.3mm width laser act more as a non-precise 0.6mm laser cut/engrave. And I was surprised in my case, maybe because my settings weren’t right for that method of engraving/cutting, that there was more charring/burning of edges than I hoped. I blamed it on that slight variance from cut to cut. I’m not against Aaron’s proposed solution but I experienced downsides with the settings I used. I never made as many passes as he has and that could make a difference I suspect.

I still recommend EVERYONE go through through the 1) bed leveling (I’m not aware of a bed being less than 1mm level from side to side, top to bottom as measured from the bottom of the lens casing); 2) mirror alignment; 3) laser focus adjustment; and 4) what was for me the most difficult, ensuring the laser beam was vertical and centered above the focusing jewel. Note, just because the beam comes through the focusing lens (jewel) and doesn’t touch the side of the housing… doesn’t mean its vertical. If trying to cut something of any real thickness, failure of the beam to be vertical (perpendicular to the workpiece) is a significant issue. To be honest, I’m not sure there is much guidance on making it ‘vertical’ or better, perpendicular to the workpiece. That requires the laser beam to be aimed by the last mirror to not be in the center of the focusing lens casing, but actually be vertical, in the center of the jewel (for proper focusing), and through the center of the lens case opening. If you think carefully through the instructions given they don’t “really” do anything to ascertain perpendicular to the workpiece (which is vertical if your bed is level and your workpiece is flat). What they do have you do is make sure the beam exits through the center of the lens housing (that is not necessarily vertical), and that it doesn’t touch the sides of the housing but exits full force through the bottom of the lens housing (also, not vertical). Think about this… if your beam doesn’t hit the workpiece perpendicularly then and 8mm thick workpiece may actually requires something more like 9mm or more of cutting length and doesn’t produce perpendicular cuts through the workpiece which can significantly effect “mating” pieces. It also may not align with what the software indicates on the computer where the beam will hit the workpiece by some amount.

Thanks Merge — I honestly dont know where you get any of this info on tuning the mirrors or laser since the only documentation Ive ever seen out of Flux are some pretty worthless unboxing videos. My concern is that running as many passes as I am is wearing out the unit prematurely. “There’s got to be a better way!” as the old infomercial goes. :slight_smile:

Ahhh … didnt see this reply before asking. That page held maybe 3 items last I looked at it. Will definitely give it a second chance!!

yeah see this is what Im talking about: https://support.flux3dp.com/hc/en-us/articles/360001360455-Control-Panel-Maintenance-Mode

Labels the icons, doesnt say anything about how to run the tests!!

I can’t speak for Beambox Pro, but when I got my Beamo it had a very detailed paper manual. All the details on laser path alignment, replacing mirrors, etc. was clear.

The alignment was spot on when I received it too, so I don’t know that every unit shipped is perfect, but I’d like to think that most of them are also fined well enough for everyday use.

Over the year that I’ve had my Beamo, the biggest improvement I found was choosing wood made for laser cutting. The more layers of wood in the ply, the more layers of glue. Glue is the hardest part to cut through, so you want fewer layers, less glue, and laser friendly glue at that. But the strangest thing I heard, was that some companies put metal flakes in their glue so they can identify their wood! That’s no good for laser cutting.

I wish I could find the link I read that detailed some recommendations for what I think was called aviation plywood. You can often find companies that will custom make it and you can tailor the quality to meet your needs. I’ll hunt around for it again.

Oh, found it:

It’s kinda next level stuff if you want to go big, but it’s still good to be aware of some of the details.