We cut a good quantity of various types of rubber, and have not found a way to completely eliminate the burr (well, maybe 'fuzz' is a better description) on the backside of the cut. 

The cut quality itself is quite good, however.

Best results come from using a .007" water only orifice at 30ksi, as it seems a smaller  stream correlates to less fuzz.

But we've found orifices less than .007 don't last, and even the .007s blow out when we try to crank up the pressure to 40-45ksi (so we can go faster).

I find that cutting many types of rubbers or plastics you get this type of a "burr". Most of the time you can run your finger down the side and it just comes off but overall I would say its just nature of the beast. Your orifice blowing out sounds like a seperate problem, i use diamonds (.003 - .007) for most of my water cuts and get hundreds of hours out of them.

This may not be practical but I have actually had luck eliminating the burr by freezing some rubber and plastics. Also, if it is possible to stack the material that will usually eliminate the burr on all layers except for the last. Even the last one will be better though.

So Tim, what type of freezer do you rep? lol We do have good luck stacking the parts we can, however, many of them are formed 3D parts which we cannot stack. And you're right, the burr can be removed with your fingernail, and we bought some small clay working knives to do it. Just a pain is all. We've had terrible luck with diamond orifices (orifii?) on our abrasive head, so all we use are sapphires.... which seem to work well, averaging 30-50 hours per. We concluded that since we change from abrasive to water-only cutting head sometimes daily, the sapphires were much less sensitive to tightening torque than the diamonds. Topend1, what sort of torque are you using for your water-only orifice nozzle nut?

I would agree with you, the diamonds are more sensitive (in my opinion) to the torque. As a heads up, Flow has some things coming out that will drastically improve orifice life across the board (shhhhh!). Next time you buy a freezer, let me know so I can send you a big teal sticker....you can tell all your friends (who probably wouldn't give a darn) that you bought a Flow Freezer!

It also depends on the type of plastic and rubber you cut. We found the thicker the material, the less of a burr we get.