The Development and Evaluation of a Four-roller Flour Mill with Parallelogram Configuration

A roller mill was designed and evaluated using four equal size cylindrical rollers with their centers on vertices of a parallelogram. The relative speeds and opposite direction of rotation of the rollers allowed the discharge of the materials on them, and splitting took place in between the first pair of corrugated rollers. The broken seeds were directed towards the second and third nips where adequate size reduction was accomplished consecutively by smooth rollers. The milled products were separated into three fractions: chaff, flour and size larger than flour. The chaff and the flour are collected at different outlets, while the particles with sizes larger than flour are blown back into the hopper for further reduction. The mill was evaluated using three grains: maize, beans and soy beans at different combinations of evaluating parameters. The machine was able to mill grains to flour size without any leakage at the nip points. For all the grains, a wide gap set produced higher throughput than narrow, as well as fast feeding in smaller particle size and higher throughput. The results obtained from the evaluation showed that the machine is very capable of three-stage size reduction to produce flour, avoiding the feeding problems in three high roller mills. Sieve analysis of the milled product for each experiment showed uniform particle size.