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Topic: CNC with servos-is it even possible? (Read 1 time) previous topic - next topic

thegoodhen

Hi guys, this might be an utter nonsense, but do you think, in theory, it would be possible to do a servo rig for high power laser and then let this laser cut into, say, wood? I mean, rig it like shown here: http://www.youtube.com/watch?v=fyFRor6cVTI&feature=player_embedded Also, although I already sort of know answer to the following question, the urge to ask it is too hard to resist: Do you think DVD burning laser would do the trick? Because I've seen a dvd laser cutting balsa. And if so, would I need any fancy adjustable optics? If it is possible, I'm gonna make myself a cute pocket cnc ^^. Thanks for all answers!

johnwasser

If you have the rotating laser close to the sheet-goods being cut you will have problems with cutting at an angle.  If you have it far away you will have problems with resolution: hobby servos have about 1,000 steps on each axis.
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PeterH

To avoid parallax issues you would be better off using a pantograph or moving beam type of mounting so position the laser over the spot you want to cut. With a little ingenuity and work it would be quite practical to put the laser in an position you want. Whether it will do anything useful to your balsa once it's there is another matter.

Perhaps, rather than thinking of it as a cutting tool you could think of it as a drawing tool - just keep the laser pointing at each spot long enough to discolour the surface rather than try to burn though it. It might work on paper etc too if you get the right combination of time and laser power. In that case you could ignore parallax issues.
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thegoodhen

#3
Apr 28, 2012, 03:52 pm Last Edit: Apr 28, 2012, 04:38 pm by thegoodhen Reason: 1
Hey, that's what I call an idea! I could probably paint the sheet of paper with some lemon juice and then burn  it so that it turns brown. CHEAP PRINTING FTW! :D Btw I didn't even realize that cutting through the material under angle would be an issue, shame on me. :X Thanks so much, guys!
Edit: but... the laser doesn't seem powerful enough to burn anything but black plastic. Stupid. :(

Grumpy_Mike

I would say a servo is a bad idea because it is difficult to control the speed of movement of a servo. Where as a stepping motor allows you to control the speed.

cr0sh


Edit: but... the laser doesn't seem powerful enough to burn anything but black plastic. Stupid. :(


That's because diode lasers (well, the ones you can generally get without a bank loan) don't have enough power; for a homebrew diode laser cutting system, I wouldn't even think of any laser under 1 watt of power.

Most laser cutters use CO2 water-cooled gas lasers outputting around 25 watts or more. It is possible to build such a laser (although the end mirrors won't be cheap; everything else though is fairly inexpensive), but they aren't small (even commercial tubes are about a foot long or so - homebrew would be larger), so you can't mount the tube and cooling system to the moving gantry. Instead, you must use mirrors to steer the beam. Since the output of such a laser is IR, you can't use just any mirrors, either - you have to use special mirrors that can reflect (instead of absorb) IR. Like the end mirrors for the laser, these mirrors (and lenses) won't be cheap. You could easily spend several hundred dollars on the optics alone.

Then you're left with putting it all together, and aligning/focusing everything so it works. Here's the final problem: You're messing around with a 25 watt, invisible beam of light, to which your eye has no blink response. Any reflection into your eye is going to cause damage. This is really true of any laser over a milliwatt or so, but when you get into the 10's of wattage range and beyond; well, let's just say you're going to want some eye protection. So now you need a pair of wrap-around filter glasses that filter the IR band you are likely in. Those aren't cheap, either.

In the end, you would be better off just purchasing an inexpensive laser cutter off ebay.
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