IR Laser for cutting 3mm black plastic?

I'm trying to upgrade my CNC engraver to cut black 3mm ABS.

In that thread it was suggested I look into IR lasers. What kind of power level would I need to slowly (several IPM) cut black 3mm plastic (abs)? I do need accuracy, so I'll need to be able to focus the beam into a small dot at 5" (<1mm diameter)

I've seen the 1W 808 diode, but that appears to be multi-mode, is that correct?

Is there any reason you can't bring the lens and/or laser closer to the work piece?

I read through the other thread.
If you are concerned with the smoke contaminating the optics, you can use a small fan to blow over the surface or a vacuum tube thingy (don't know what to call it) to suck the smoke away.

I would stay away from overdriving 405nm or 445nm diodes and stick with driving a higher power IR diode within specs. The reason being... for something like this I bet you want a long lifetime. If the diode dies because it is over-driven that's money down the drain and time lost resetting the machine.

If you want a clean cut you will need a sharp focal point (as Cyparagon recommends) and you want to cut it as fast as possible. The more time the laser spends on the plastic - and the wider the beam - the more of the surface will melt which could cause messy edges.

$0.02

Use a CO2 laser for most anything. You can get ZnSe Lenses with a 5" FL sometimes from ebay. A neutral purging gas like N2 or even air should protect the lens when injected from the cutting head. For 3 mm (1/8") material, 20 watts should be sufficient.

HMike

I don't think his DIY CNC engraver is quite up for a CO2. heh.

hehe CO2 might be out of my league thanks for the advice though!