Has anyone built a 100w+ 4x8 laser?

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Has anyone built a 100w+ 4x8 laser?

Postby lumberjack_jeff » Wed Aug 22, 2012 4:18 pm

We make model boat kits from 3 and 4mm ply. I currently make them on my 4x8 mechmate, but holding the parts is a problem. Additionally, a laser would enable us to do more things that we currently can't.

I built the mechmate very inexpensively so I'm not intimidated by cost control, welding and motion control aspects, but I'm completely ignorant of the laser optics.

I've considered buying 2x4 from china, but $1200 in import fees ticks me off.

Can I use EMC and g-code, or should I buy a laser controller box?
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Re: Has anyone built a 100w+ 4x8 laser?

Postby bdring » Wed Aug 22, 2012 4:38 pm

Virtually everyone I have known who tried to build a conventionally designed 4x4 or larger DIY laser has failed. The squareness and alignment issues were too much to handle. The tiniest bit of vibration or warp would cause problems.

If I were to try this, I would put the tube on the gantry to remove one moving mirror, but a 100w CO2 is pretty huge.
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Re: Has anyone built a 100w+ 4x8 laser?

Postby lumberjack_jeff » Wed Aug 22, 2012 5:02 pm

bdring wrote:If I were to try this, I would put the tube on the gantry to remove one moving mirror, but a 100w CO2 is pretty huge.


Good point, a 100w laser is almost 5' long. I need to do some sketching.

One of the other problems that occurs to me is keeping the work table flat relative to the lens. On a cnc machine, one just surfaces the table to make it planar.
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Re: Has anyone built a 100w+ 4x8 laser?

Postby Tesla » Thu Sep 13, 2012 2:42 am

What about a 40W 2X4 table ? what would need to be done to assure accuracy of the cut...besides a stable table and alignment of the square rails.
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Re: Has anyone built a 100w+ 4x8 laser?

Postby Enraged » Thu Sep 13, 2012 3:20 am

The only change I want to make to my 2.x build is increasing cutting area so I can cut off the shelf 12" x 24" sheets of plywood or acrylic.

If you get into anything as large as a 4x8 machine, you have to start looking at serious linear motion hardware, ie ground ways and ballscrews. I build a 5x10x3 CNC router, and it uses a lot of expensive hardware (luckily most was purchased through eBay). At least with the router we can machine the table flat or shim it level, but I would imagine with a laser that size you would have some serious alignment issues.
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Re: Has anyone built a 100w+ 4x8 laser?

Postby Tesla » Thu Sep 13, 2012 7:30 am

If you go to a big size would you have to increase the 40W to more ?
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Re: Has anyone built a 100w+ 4x8 laser?

Postby TLHarrell » Thu Sep 13, 2012 3:53 pm

40w is enough for even a larger machine. It depends entirely on what you want to cut. Balsa and basswood, light ply, paper and acrylics are good up to about 1/4" thickness. Sounds like he's using 1/8" stock, so that's easily in the range of a 40w laser, and there's no real need to go higher wattage with the extra cooling needed. The only issue here is adjustments of the beam path along such a large machine. Difficulty in aiming and focusing increases exponentially with longer beam paths. Certainly the way to go is to place the tube in a moving gantry, so the beam path is aligned along the X axis only. I would not recommend an 8' long gantry though. Something more like 24"x48" is feasible, making a 24" gantry (X axis) and traveling on a 48" table (Y axis).
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Re: Has anyone built a 100w+ 4x8 laser?

Postby Tesla » Thu Sep 13, 2012 8:52 pm

So how would that work, would the laser beam that's stationary have to become mobile ? I'm looking for a 2x4 table. Circled in red.
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Re: Has anyone built a 100w+ 4x8 laser?

Postby peter_ » Fri Sep 14, 2012 4:45 am

Tesla wrote:So how would that work, would the laser beam that's stationary have to become mobile ? I'm looking for a 2x4 table. Circled in red.


Basically the idea is that you'd mount the tube along the length of that top axis so that it'd move when the top axis moves. On the end the beam emerges from, you'd place two 90° mirrors to make the beam turn 180° and move beside the laser tube (but in the opposite direction). The Z mirror and lens would look the same.

I tried making one with a little more than 3'x3' travel, and like Bart said above, I could never get it square, even after a bunch of design revisions. The smallest vibration, tilt, or skew makes it impossible to align. It's even hard finding a table actually flat enough to have it aligned on, and if you ever move the unit, you have to align it again. I wish I'd done the moving-tube-on-the-top-axis initially, it'd have saved a bunch of work and heartache.

best of luck!
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Re: Has anyone built a 100w+ 4x8 laser?

Postby Tesla » Fri Sep 14, 2012 8:08 am

How do the machines do it , their are bigger tables..same way as peter described ?
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