[HomerSimpson]

I bought a G.Weike 80W laser machine last year and love it but I have a job I can't seem to run with it. I need to cut some structural insulated panels (SIP), which consist of two panels of 3/4" oriented strand board (OSB), which sandwich a 4, 8, or 12 inch layer of polystyrene or polyurethane foam. They are used in constructing residential homes.

I think there are three parts to solving the problem:

1) lens focal length
2) laser power
3) laser cutting area

I exchanged my standard 50mm lens for my 190mm lens, which requires the lens be 190mm away from the surface of the material (if I understand it correctly), and allows the laser beam to be in focus over a much longer distance. This distance appears to be OK, at least for some thinner sections of foam I tried to cut. However, the laser power appears to be inadequate, using this lens, to even cut through the first layer of OSB. Also, I will eventually need to place 4'x8' sheets of SIP on the laser, and my machine has only a 2'x3' cutting area.

My question for the forum is what I'm doing even possible with a standard laser cutting machine? #3 is easy. G.Weike has machines this big, for example. As for #2, I'm sure one can get a laser that is powerful enough, however, can it be done for a reasonable cost. Again, G.Weike sells a 200W laser I think. Is this enough? #1 is the biggest question for me, not only to know if I can get a lens that will do the job, but can I get a machine that would then allow for that much distance between the lens and the material surface. Based on the picture on Weike's website, the large machines all appear to be fairly close to the material surface and they don't appear to have much, if any, z height adjustment.

Your thoughts are appreciated.

[Exsecratio]

Not a hope in hell, a 7KW isn't going to cut through that much, to cut a 10" depth straight you would need a 70 foot focal length!!

You are using 2 dissimilar materials (wood + polystyrene) so burn back will be a problem as well as core fires.

A laser of ANY kind is the wrong tool for the job, even 3/4 OSB along is going to be a struggle for a 200 watt machine.

Have a read of this

OPLaser support forum ? View topic - Understanding Depth Of Field (DOF)

Multipass cnc routing "could" do the job but being honest a bandsaw would probably be the best way.

The thickest material you will cut with an 80 watt is 9mm, (it will be slow and look aweful) so 6mm is the realistic top limit for 80 watts. (yea I know somebody will be along and say how they cut 1 inch steel with their special 2 watt diode etc etc etc but unless the laws of physics have changed in the last 10 minutes that simply isn't going to happen))

cheers

Dave

[DareBee]

You need a waterjet

[HomerSimpson]

I was afraid of that. Thanks for the candid advice. I had thought of a waterjet, and have access to one at work, but I am worried that as soon as I submerse the OSB in water, it will start to break down the glue which holds the strands together, eventually causing structural failure. For my prototype, I machined the OSB on my cnc router and cut the foam with my laser and then just glued them together, but that's a time consuming process long-term.

[Gweikelasers]

Hi, Yes, i agree with your three points.
For common Chinese lasers, the cutting ability limit of 130W/150W machine with at least 100mm focial length is around 20-25mm acrylic. The 200W machine uses British GSI tube, and it has large price difference with common co2 lasers. With that budget, you can also have other choices.

[Exsecratio]

8 to 10mm Mel or 8 - 10 inches? and 4 inch focal length (100mm)

best wishes

Dave

[Exsecratio]

Yup pretty much, OSB isn't going to like being soaked with water (well not if you want it to hold together)

High speed bandsaw or router is going to be about the only affordable option.

Be careful lasering some of the styrenes, they can on occasion contain chlorides and will give off highly toxic gas.

best wishes

Dave

[Sho409s]

A vertical foam rubber table saw without a stripper guide, running an offset blade might cut that nicely. Still have to load/unload the table, would be cool to set one up with rollers for panels that large. They are pretty much a large table saw with a rolling table, look up edge-sweets, trucut, etc., have made them. Blade speed is high they cut fast like a skilsaw, you can set up a vacuum in the bottom to catch much of the dust. They will eat 2x4s laid across the table like nothing. They take up a lot of floor space. Offset blade will cut the wood, not leave a nice cut on the foam, but with wood you don't have much choice. Unless you need a finish cut, maybe you could finish it off with something else.

[Winks]

Experiment with the waterjet. Cutting on top of a piece of sacrificial material keeps the bottom pretty dry and use air to blow off puddles as they form on top. The edge can stay surprisingly dry. Sandwiched material of that thickness can present a problem with taper, but fiddling with cutting speed and garnet feed can minimize it.

[Gweikelasers]

Hi, Dave, thanks for your reminding.The conversation between mm and inch is headache to me. My math is not good

[ozstockman]

I do not know what OSB is but I can do straight cut at 600-900mm/m and 90% power through 18mm thick MDF or even 20mm thick oak with my 280W CO2 laser. It uses 2 x 140W GSI tubes and 3" lenses. I do not think anything thicker than 25mm will produce straight angle of cutting.

It was not cheap though considering that GSI 140W tubes cost 6K each. However it is still a bit cheaper than I have paid for my LaserPro Spirit GX 100W.