Burr RPM affects grind particle size distribution significantly - Page 3

#21: Post by **Bob_McBob** » March 23rd, 2014, 9:48 pm

pocojoe wrote:Can you please post the link? Thanks
Joe

#22: Post by **indend007** » March 23rd, 2014, 9:57 pm

to quote @papamurgy twit
Robur provides better dose precision in AU than US

Not about particle distribution, but about different Hz, and RPM.

#23: Post by **IMAWriter** » March 23rd, 2014, 11:00 pm

RapidCoffee wrote:As Jim notes, finer grinds cause more bean breakage and generate more fines, leading to increasingly bimodal distributions.

John, I'm confused. Did you mean "faster (greater) rpm", not "finer grinds?"

Thanks.

#24: Post by **RapidCoffee** » March 24th, 2014, 1:01 am

IMAWriter wrote:John, I'm confused. Did you mean "faster (greater) rpm", not "finer grinds?"

No, although the plot suggests that may also be true.

A finer grind setting on the grinder means the burrs are closer together. Beans must break into smaller fragments to pass through the gap between the burrs and exit down the chute. Every time you break bean fragments, smaller pieces (fines) break off as well. Finer grind settings result in more breakage, a finer grind, more fines, and produce a more bimodal distribution.

Typical espresso grinds tend to have the main peak at ~400um diameter, with a fines peak at ~40um. All other things being equal, a grind setting that produces 1000um diameter particles will produce far fewer fines, and appear unimodal on a particle size distribution plot.