Need Help!- Edge quality cutting polycarbonate with 80 watt co2

[lswonger]

I am trying out an 80 watt co2 laser cutter for 0.060 inch thick polycarbonate flat sheet. Initially I had quite a bit of charring at the edge, but then went to a nitrogen blow off instead of the air compressor which came with the unit.

I can get rid of the charring if I turn the nitrogen supply pressure up to about 60psi, but it leaves a fuzzy edge on the back side of the cut piece. I believe the laser is melting the plastic which is blowing through the back side and solidifying into the "fuzz". At 60 psi i have a pretty intense jet of nitrogen blowing onto the spot being cut.

I have tried different combinations of cutting speed, power, and nitrogen pressure, but cannot seem to get a nice clean edge without either charring (at low nitrogen pressure) or fuzz (at higher nitrogen pressure to get rid of charring).

Is it possible to get a nice clean edge on PC? Any suggestions on what to try?

[Tweakie]

If you could use acrylic instead of polycarbonate then it would be problem solved.
At the best of times poly is a pain.

Tweakie.

[lswonger]

It needs to be polycarbonate.

[Ken_Shea]

Having just ordered a laser and having done much reading, read repeatedly that laser cuting PCV or Polycarbonate gives off very dangerous and toxic hydrochloric acid fumes as well as setting up corrision anywhere these fumes go.

I do not know the level of danger or practical precaution just putting it out here for thought.

Ken

[lswonger]

I have all of the proper ventilation set up. My Only problem now is the dried/fuzz left on the back side of the cut caused by material blowing out the back side.

[samco]

It has been a while since I have done any of this. I think what we found out worked best was running almost no air. You get a golden brown edge then. Don't remember what kind of power. iirc - you ran just enough power to get it to burn through.

(again - it has been a while)

sam

[lswonger]

High power and faster speed seem to give the best edge. It leaves a little bit of debris on the back side which wipes off fairly easily

I switched from Nitrogen back to air and it did not seem to make a difference, so I am now just using air.

The best parameters I have found so far are 95% power (100%=80watt), 2.3 meter/minute, and a 40psi air supply to the cutting tip.

The spot stick I have on it to protect it while handling seems to be a little bit of an issue. If I cut the stock piece with the manufacturers spot stick on it there is no problem, the type I was using seems to leave a black edge instead of the yellowish brown edge. I am going to try some experiments with different types and see which is the best. Any suggestions out there?