Polycarbonate is great stuff to mill but the little gritty swarf gets everywhere. I also find that my 1/16" bits tend to wind up any strings of polycarbonate and eventually build up enough that they form a little puck of fused plastic around the tip that destroys the work surface.

I built this attachment to take the tube from my shop vacuum and apply suction right next to the head on the mill. The photos and MP4 show it in action, it works pretty well (for those who are interested, it's cutting 3 mm polycarbonate with a 1/16" TiCN coated two-flute spiral at 10,500 rpm, feedrate 600 mm / minute).

The polycarbonate sheet is being held in version 2 of my laser-cut fixture, previously posted as http://www.thingiverse.com/thing:20281

Instructions

Print. Clean. Install. Use.

Should click into the T-slot on the right side of the Taig's milling head (slide it up from the bottom until the little lip clicks over the top). The hose from the shop vacuum (2" internal diameter) just slides in and friction-fits (the tube is slightly tapered).

There are some flaws in the mesh but nothing that interfered with the print. This one was done on an Objet 24 as we have one, but I'd be interested to see how it turns out on the DIY machines. It may need some solvent to fuse it together more strongly if printed by FDM. The worst stresses are around the T-slot mount.