another_jim wrote:The OP talked about the grounds, not the motor or housing. Grinding heats whatever is ground, since the energy used to break the large bits into smaller bits turns to heat -- even a hand grinder, when turned fast enough, will heat the grinds. The Robur heats grinds no worse than any other grinder.

I'm not so sure about this explanation of why the grounds heat up. If I smash a walnut with a hammer, little or no heat is transfered to the walnut pieces. I believe the energy of the blow goes mostly into breaking up the shell.

I think, rather, that the heating of coffee grounds is caused by friction of the beans, bean particles and grounds against the burr material as the grinder spins,

You're right; but it may be a distinction without that much of a difference: the energy required to overcome the friction between bean and burr is what grinds the beans, and gets turned into heat.

Also, when you hammer a walnut, there's lots of moving air to take up the heat. In the grinder, there is only the burr and the bean. The stainless burrs don't dissipate heat well, so the bean absorbs much of it.

This ties into Eric's and Andy's points about dissipating that heat. C S Lennon, an occasional HBer who owns a robot factory, tried making some water cooled Robur burrs. Apparently, even this didn't do very well. Air cooling suffers from the fact that a cooling airflow is also likely to create an annoying ground coffee flow. Having ground coffee flying out of every gap of the dosing mechanism at high velocities may cool the grounds, but would probably create additional problems

For the home use, I'd think the whole concern would be moot. And it won't affect the flavor, so don't worry about it.