the rapid 10 series is a low-speed - just 25 rpm - very quiet granulator ideal for grinding hard, thick-walled and/or brittle injection moulding sprues and rejects at low capacities. the very slow speed helps to minimize ......the rapid 10 series is a low-speed - just 25 rpm - very quiet granulator ideal for grinding hard, thick-walled and/or brittle injection moulding sprues and rejects at low capacities. the very slow speed helps to minimize noise, frictional heat, and component wear and tear.