Laser accuracy

General discussion of laser machines

Laser accuracy

Postby dark_helmet » Tue Feb 07, 2012 4:43 pm

Wondering if anyone can tell me what kind of tolerances you can hold with a well built laser cutter. Main job I'm looking at right now is 1/2" acrylic and need to cut shapes that fit into an aluminum jig with a hole though it. A slip fit is desired, just so it doesn't rattle around to much.

So once you determine you beam size/cut kerf, and adjust for that, is say a +-0.003" tolerance achievable or would it be more like +-0.005" or not even that?

For sake of argument lets say a laser built with thk rails and linear encoders.
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Re: Laser accuracy

Postby TLHarrell » Tue Feb 07, 2012 6:22 pm

Depends on your drive mechanics. If you've got 1000 steps per inch, theoretically you're at 0.001" accuracy. Of course the laser kerf, machine vibration, power settings and other things will vary the accuracy slightly. It is entirely possible to make an adjustment to your drawing of .001" and see a difference in fit of a part. I can do the same, and I'm running a basic 40w Chinese laser.
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Re: Laser accuracy

Postby dark_helmet » Tue Feb 07, 2012 8:44 pm

Ok, thats kind of what I wanted to hear I guess. So it should be cable of decent accuracies on smalish parts.

On larger parts (thinking a machine with gantry mounted tube and maybe 4'+ in X) is there a difference in kerf width as you get farther from the beam source due to divergence? Does different focal length mirrors affect this difference? Or is it not noticeable?

I guess what I'm getting at a bit, is if I have an array of smaller parts nested on a sheet, do the parts farthest from the mirror end get smaller than the parts near the mirrors due to a wider kerf width?
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Re: Laser accuracy

Postby trwalters001 » Tue Feb 07, 2012 8:53 pm

If your part-to-focus lens distance doesn't change, your focused spot size won't change. So - your kerf width will stay the same.
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