I'm using Dremel 3000 along with a diamond wheel which is not cheap either at around 20EUR. It does the trick for about 30-40cm and then goes dull. It only cuts when the dremel is at it's highest setting. Anything less and it barely scratches the surface. It seems as if when the resin is heated while cutting, it sticks on the wheel and dulls it. I don't know if that's whats happening but I can see that the dimond wheel is covered with thick black stuff. I can sand it down with some abrasive paper but that doesn't seem to improve anything. Can anybody help me with that? Any methods for cleaning/sharpening the diamond wheel? 

Remember that when cutting the sheets with a rotary tool that the heat can get quite high causing the resin to begin to melt/burn and hence come off on the cutting wheel.

This can happen on all kinds of discs albeit the more coarse the disc, the more capacity for resin to stick. 

We usually recommend tungsten carbide cutting discs (such as the Perma-Bond range) and we use one in daily use in our workshop.  Yes they can get a bit of carbon build up but not usually a problem and often our discs last a good 6 months of daily use where they could be cutting 10-20 medium sized items every day during the week.

We do use one of the more powerful Fortiflex range dremel tools as they can be located clear of the carbon dust and use a foot pedal. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant