cutting thick plywood

I have a Chinese 50 watt laser. I have just changed the laser tube to a 55 x 1250mm tube (it originally came with a 50 x 800mm tube) that the manufacturer claims to be 80 watts. I did not replace the power supply because I don't have money to buy a power supply but I will change it shortly as well. Initially the tube wasn't outputting much power but after showing the seller he told me to rotate the tube so the water inlet is facing down. For some reason this fixed it. I plan to get a 150 watt power supply in the future...

I tried cutting thick, 12mm plywood. However while it cuts anything up to 9mm easily (with the new tubes), I find anything thicker just burns no matter how many passes I take. In fact I did a test with plywood where I would just cut very slowly, and what happens is the wood always burns. Is there an upper limit to laser cutting plywood?

I tried with plastic and I can even cut 19mm thick plastic either with multiple passes or very slow speeds (65% power, 1mm/s) and while the cut quality isn't great, it cuts.

So what's the deal? how can I cut thick plywood? more power?

I asked a steel supplier with a hefty laser and they said 1/2 to 5/8 was thickest wood they could cut before it burns instead of cuts. They can kind of cut 3/4 stainless with the same laser.
I know not really an answer but seems to be a laser thing. No idea of gases they use.

Cut thinner sections, glue up.

It might be a "char layer" situation, where the carbon buildup insulates and traps heat the further into the wood you try cutting.

So it sounds like even if you have a 400 watt laser it still won't cut much over 9mm? The char layer seems to be the issue because I could move fast at 30mm/s and 30 passes and after the 15th pass the wood is actually on fire, and air assist actually fanned the flame! Glad I did not walk away or else I'm going to have a fire.

I wonder if anyone ever add fire suppression to a laser? I can think of one way where if the machine detects excess smoke it dumps laser cooling water onto your work.

Can anyone tell me if a 55*1250mm tube can be 50 watt? The manufacturer says it is and tested the tube to 80 watt with a Max of 86 watts. He said its a high efficiency catalyzed laser tube. I know RECI makes a 90 watt tube that's 60*1100mm rated to 90 watts so it must be possible?

Wood is a complicated material, with dramatic changes in properties when burned. If you really need to cut thicker sections and don't want to glue layers together, consider getting a CNC router. It might be a better choice for you over a laser, especially if fire safety is an issue.

A router would also give you the option of 3D carving, something the laser won't (easily) do.

What are the costs for a CNC router compared to a laser? Say something that allows a working area of 600x400mm and I can mount a dremel, router, or air die grinder into?

I can't find any low cost options for this.

You're right next door to the land of cheap CNC routers, do a bit of searching and see what might work for you. I wouldn't bother with anything but a proper router motor/spindle, a Dremel or die grinder kludge would be money wasted.

Actually I kind of want to make a low cost CNC cradle. You know I can stick a router spindle on it, a plasma cutter, or whatever to allow me to cut a variety of materials. The expensive part is the controller unfortunately... I can't find anything less than 1000USD.

I was even wondering, those laser DSP controllers, some of them can support 5 or 6 axis. Do they only work for lasers or can they be made to work for CNC everything else including mills? One of these days I'm going to use a big stepper motor on my Bridgeport as a power feed... then eventually turn it into a CNC by adding a controller.

Is 20,000 USD a lot for a VMC? Someone is offering one in excellent condition for that much. It's a Bridgeport GX710.

taiwanluthiers said:

So it sounds like even if you have a 400 watt laser it still won't cut much over 9mm? The char layer seems to be the issue because I could move fast at 30mm/s and 30 passes and after the 15th pass the wood is actually on fire, and air assist actually fanned the flame! Glad I did not walk away or else I'm going to have a fire.

I wonder if anyone ever add fire suppression to a laser? I can think of one way where if the machine detects excess smoke it dumps laser cooling water onto your work.

Can anyone tell me if a 55*1250mm tube can be 50 watt? The manufacturer says it is and tested the tube to 80 watt with a Max of 86 watts. He said its a high efficiency catalyzed laser tube. I know RECI makes a 90 watt tube that's 60*1100mm rated to 90 watts so it must be possible?

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Try nitrogen as an assist gas, or even CO2. If you are using air you will make a fire.
I have 1000 watts of fiber. Was wanting a deep etch on a piece of 10 gauge so I lowered the power and did a test with oxygen. Nice deep etch that would easily show through paint. So I ran the program and at some point I saw that the laser had burned right through the part. Silly me. The etch was a detailed cad drawing of my competition car, right down to detailed hex wheel bolts. With so much detail in a small area the metal got too hot and oxygen burned through.

You can try increasing your pierce time. On mine, if the laser doesn't get all the way through the part when it pierces, it won't cut through the whole part.

taiwanluthiers said:

What are the costs for a CNC router compared to a laser?

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You could look at the sign-making machines, there's tons of them cheap and they do pretty nice work, but ...

Say something that allows a working area of 600x400mm

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If you went bigger, say 1 meter in X, you could make guqins, which might bring in more money where you are. You'd want a full 3 axis mill for that, though. $20k sounds like too much to me.

I can't find any low cost options for this.

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Coping saw and a plane and maybe a spindle sander

I did pierce tests on my laser and I guess it takes about 1 second to pierce. I do not know how to set this with the moshi board however. I do not think it's possible. Maybe when I can find money to do a DSP upgrade this could be an option...