Design of a human powered maize mill

Abstract

The process of milling corn into flour in many rural communities of East Africa has remained a traditional mortar and pestle process for centuries. Milling machines have failed in these communities largely due to poor performance, as well as high cost, and as a result the incredibly labor intensive process continues. This study seeks to design and manufacture a prototype mill that will address the needs of the communities in question. Initial testing on existing milling equipment generated a quantitative understanding of the strengths and shortfalls of the available machines, and informed the design of a new mill. Once the design specifications were determined, a two stage, "twinmill" incorporating a stock low cost mill performing an initial coarse grind and a second identical mill that used modified grinding plates to produce finer flour was built. As expected, the two stage solution outperformed the existing machines by a significant margin: the acceptable flour yields rose from the 30-40 percent range, to consistently in the mid 60s. After subsequent modifications to the fine pass machine grinding plates, yields rose even higher, to an average of about 80 percent.