Laser cutter

General discussion of laser machines

Laser cutter

Postby Jano » Mon Jun 04, 2012 7:34 pm

Has anyone here made a laser cutter that can cut metal?
As far as I know there are two versions of open source laser cutters but none of them was made to be able to cut steel ( metal). Or am I wrong?
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Re: Laser cutter

Postby canadianavenger » Tue Jun 05, 2012 3:13 am

to cut steel you're talking about LASER power in the kilowatt range... well outside the range of the typical DIY range [which falls in the 20-150W range]. You also won't find tubes in that power range... for that power level you'll need to get a RF excited slab type laser, and it'll cost considerably... probably more than your car!
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Re: Laser cutter

Postby naPS » Tue Jun 05, 2012 3:36 am

I don't think that's necessarily true - it might have been in the past, but I know the last time I had some stainless cut locally, it was on a 200 watt or so laser with oxygen assist. Also, here's some stuff from Kern laser, describing their 150W and 400W laser systems : (from : http://www.kernlasers.com/metal_cutting.htm)

The 150 watt laser will cut up to a thickkness of .090" mild steel and .075" stainless steel. The 400 watt laser will cut up to .1875" mild steel, .125" stainless steel and some aluminum alloys up to .050". The 400 watt laser will also cut thinner gauge brass, titanium and nickel. Please feel free to send us your metal material to determine the feed rate and edge quality the KERN Metal Cutter can produce.

Metals that can be cut with a Kern CNC Metal Cutting Laser are:


Stainless Steel
Spring Steel
Titanium
Mild Steel
Nickel
Carbon Steel


Stainless Steel
Aluminum
Spring Steel
Brass Shimstock
Carbon Steel
Mild Steel
Nickel
Phosphorus Bronze Shim Stock
Titanium
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Re: Laser cutter

Postby loopingz » Wed Jun 13, 2012 2:44 pm

Any idea on the prie of Kern laser? I dont want to bother them with a quote, just for my information...
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Re: Laser cutter

Postby TLHarrell » Fri Jun 15, 2012 10:51 pm

Bother them. It's what they do. Just let them know what your requirements would be, and that you're looking to purchase in the future. They pretty much do quotes all day. It's how they sell their product.
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Re: Laser cutter

Postby loopingz » Wed Jul 18, 2012 10:29 am

I have found out.
About 6 figures.
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Re: Laser cutter

Postby autocrib » Fri Oct 05, 2012 9:11 pm

My friend has brought a laser cutters can cut metal at all are gigantic $125,000 industrial monsters that have 1000 watt lasers and up...they also are not UV lasers like ours.
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Re: Laser cutter

Postby btboone » Sat Oct 06, 2012 3:08 pm

I have built one on a Tormach mill with a fiber laser. A CO2 laser's wavelength is not optimal for cutting metals. Industrial ones do it with the brute force technique, and usually have thousands of watts. They need a continuous supply of nitrogen, CO2, and helium and usually take 460 volt three phase power. Big ones have a radio frequency resonator, and gasses are shot in the vacuumed out chamber at nearly the speed of sound by a compressor running at something like 300,000 rpm. You can cut thin metal with about 400 watts with an oxygen assist, but you are at the lower threshold of being able to cut metal at all.

A fiber laser is a whole different animal. It works similar to a ruby or yag laser in that the laser medium is a solid that's pumped by light. The difference is that the lasing medium is only about 50 microns wide, but is extremely long. This means that is is extremely efficient because all the photons are already traveling in exactly the right direction, but also the pump light is introduced from one end and can only bounce around the fiber core and can't get out due to total internal reflection angles. The light that excites them is done by diodes, and is exactly the right wavelength to get the fiber to lase. The diodes are extremely efficient and are glued to a plate of aluminum. Because the fiber is so long and thin and because the diodes are glued to the plate and their power combined, the laser is extremely efficient, with a wall efficiency of around 40%. This means a fiber capable of cutting through metal plugs into the wall and needs no cooling! Because of a trick of optics, fiber lasers also don't use external mirrors; they are "built in" to the fiber itself! The beam does need to go through a collimator and then focused to a spot. A separate laser head serves this function. The laser head is also plumbed with a high pressure air or other assist gas. I am cutting titanium, so I am using argon. Steel could use nitrogen, oxygen, or air.

My laser is 450 watts continuous, but due to the diodes pumping the fiber, they can be pulsed and the laser can produce a peak power of 4500 watts. I had some trials run, and we went through 7mm of titanium. The piece was a thick ring blank and had a hole through the middle. The beam went through one side and actually went through the opposite side as well. This was a total of 14mm of titanium using "only" 3000 watts. I went with a special laser head with a long and short lens option to be able to do very fine stuff. Theoretical kerf with the shorter lens is 50 microns. That's about .002", which is less than a hair. The longer lens is meant to go through thicker material, and has a theoretical spot size of 100 microns, although I haven't yet gotten that small in practice. I am still doing trials, and have a kerf on .070" stainless sheet in the order of .006". It's a very clean cut from the front, but I still have a little slag on the back. I have a technician coming in next week to help dial it in.

Honestly, for metal applications, fiber will be replacing CO2 in factories everywhere. They have beam switches where several machines can be run from a single laser. One can be cutting while another is welding. It's pretty amazing technology.
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Re: Laser cutter

Postby btboone » Sun Oct 07, 2012 4:13 am

Picture 1983.jpg


Here's a cut I did a few days ago. We just tonight found out that the settings used were not input in the way that we thought the software interprets them (a difference of duty cycle of a pulse versus the period of the pulse.) When the correct numbers were put in, we got a much cleaner cut without as much slag on the back side and a finer kerf.
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Re: Laser cutter

Postby canadianavenger » Sun Oct 07, 2012 7:54 pm

Nice work! How much did you pay for the fiber laser, and where did you get it? Most people here use CO2 because it is more within reach for the DIYer from a cost perspective. I think CO2 is still cheaper from an industrial perspective too, so it'll be some time before it is replaced.
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