Recently my team got a Thunder Laser Nova51 130W laser cutter. We are excited to use it to improve our prototyping capabilities as well as provide accessible manufacturing options to our students. We have set up the machine and have begun trying to develop appropriate material speed, focus, and power profiles for cutting and engraving in a variety of materials, but have run into some issues with plywood.
So far, we have been unable to cut through plywood without charring and igniting the wood, and often get inconsistent cut depths throughout the profiles we’ve been cutting. The parts that do get cut out have a terrible surface finish that makes them far from dimensionally accurate. We have been testing with 1/2" and 3/4" thick plywood we had laying around in our shop. We have the 4" head that helps cut thicker materials. From our research online, our current cutting strategy has been high power, high speed, multiple passes, so we run the machine at around 80% - 90% power and between the range of 200 mm/s to 800 mm/s, and end up needing a few dozen passes to get through the material. I believe we’re running the laser head about 6mm above the part.
We’re pretty new to this and going in blind, so any help would be appreciated.
With thick material like this, it can help to adjust the Z height between passes so that you’re cutting at optimal focus on every pass, not just the first one.
Air assist makes a world of difference, make sure that’s on.
Also, lasers can struggle with cheap construction-grade plywood that has inconsistent internal voids and generous amounts of adhesive. It can do it with a brute force approach, but you get much better results on cabinet grade/aircraft grade high quality stuff.
We have a ~100W co2 laser. A lot depends on the type of plywood. Typical flooring / roofing plywood cuts terribly. Expensive Birch plywood cuts wonderfully up to 3/8" thick. I think a lot has to do with the glue that each use.
1/2" to 3/4" thick seems to me like you are pushing it for thickness on a CO2 laser
Do you have air assist? that helps a lot with avoiding fires. Otherwise thinner plywood so you can cut with less heat.
like andrew said, we were trying to cut plywood with a 4" head, but it would not cut. we tried 2mm/s at 90% power as well as 200mm/s 90% and upwards of 150 passes, but neither seemed to cut well. however, when we cut a 3/4" wide section off a 2x4, it cut it fine. in addition to this, it seemed to not want to cut through the seems of the plywood, but the actual wood was ok. I think it is having a hard time cutting the epoxy holding the board together, and instead the wood smolders through it and once the smolder has cleared the epoxy it continues to cut, but that just a guess, we are open to any suggestions and thanks in advance for the help!
Emphasizing again Brendan’s point that wood quality is a huge deal. Air assist is a close second. Focus height third.
With a decent 3/8 and 1/2 Baltic birch, we get great dimensional prototypes with about 70% of 140W. Random shopwood sometimes works. I have never had the guts to try OSB. When Shopping… Look for a lot of layers of wood, to make sure that there’s minimal epoxy thickness (and resulting minimal inconsistency).
Do you have a strong enough compressor attached to it to keep up with air demand?
When everything’s tuned in, expect two to three passes at most. Might need to play with your height, 6 mm sounds high but definitely varies by machine.
If you have ever cut without air, your focus lens or mirrors may now be dirty from smoke and need cleaning before you can access the full power of the machine again. Worst case, a dirty lens will pick up heat from the laserbeam and crack.
Wet air can also contribute to this - we run a filter on our air input but it’s definitely not perfect and I’ve seen mist collect inside there in the wet season.
(Definitely not speaking from experience here Definitely never rode to Sacramento first thing on a Saturday morning to pick up a new focus lens at lightobject…)
I forgot to mention: we will often do two passes and then bash it out from the plywood stock with a dead blow hammer for 1/2, when there’s a layer of char at the bottom of the laser path that is being stubborn about achieving consistent full beam penetration.
Even with nice Baltic, we’ve struggled to get full penetration with the laser in 3/4. Same hammer trick kind of works, especially if you follow the “dotted line” outline on the bottom of the part with a chisel first. 3/4 isn’t necessary for most prototyping anyway. We do the majority of our fit up and brainstorming work at 4 mm, then battle test at 3/8.
The correct way to do this is to “just” get the laser settings right with high quality wood.
I don’t know the answer but I’d just like to point out that there is a pretty active Thunderlaser User’s group on Facebook that might be able to help.
+100 to everything said here about clean lenses, air assist, and adjusting the Z height between passes. But the glue is likely the culprit.
You can test this by running a series of cuts at different speeds and power levels, then cut the board in half to inspect the cuts. With most plywood you will find that the cuts stop at the glue layers. The glue used in a lot of plywood does not absorb the laser energy, so doesn’t cut. Charring will ensue.
The same thing happens with MDF. I’ve bought the same SKU from Home Depot and had some sheets cut like butter and others that resist and make a smoky mess.
Even a lot of “hobby grade baltic birch” plywood does not use a laser-friendly adhesive. You really want to find a good source for “laser-compatible” plywood.
If your laser truly is 130W you should be able to cut 1/2" baltic birch ply in one pass with no issue. We have a 120W Trotec with 2" focal length and can cut 3/4" thick home depot/lowes baltic birch with no issue (same stuff you’d probably be buying in the bay area). 3/4" is very slow. 1/2" works pretty well.
I don’t know what our settings are offhand, as Trotec uses a stupid metric that’s a “percent of full speed” for linear speed. but we cut at 100% power
You’ll want a Z offset into the part and you’ll want air assist. You may need to adjust the pulse frequency of the laser as well.
If you’re not exhausting to the outside and you’re filtering your air, the glue from the plywood is going to destroy your filters almost immediately. You’ll need a special setup for that.
Any idea what the specs are on your air supply? (Cfm, pressure)
You’re getting better cuts than we are. I’m on a 60 gallon 3.7hp home Depot compressor that struggles to keep up with our cuts - datasheet says that’s 11cfm.
I also don’t like running at 100% power - lightobject has advised against it.
Our trotec has a 1/4" air line supplying our air assist. At 100 psi that’s somewhere in the range of 6 CFM. Our compressor does 38 CFM at 100 psi but we run it to… 130 or 140 psi I think, so it probably outputs somewhere around 30 CFM.
So I think there’s a decent amount of people that argue if this is a feature of RF CO2 tubes, DC Glass tubes, or both. I was never able to find a concrete answer to if you should change the PWM frequency of your standard glass tube from China (there’s a setting in the advanced tab of your layer settings for those using light burn). I think it also requires your tube to be hooked up as PWM and not analog from the controller to the LPSU, and from what I’ve read you get better performance from an analog signal then a PWM one.
Now I have no idea if any of this is true, I’ve tried a bunch of different setups with my Rudia controller and 60W tube, so if anyone has a definitive answer on the “correct” way I’m all ears.
Definitely never rode to Sacramento first thing on a Saturday morning to pick up a new focus lens at lightobject…)