Design and Development of Walnut Cracking Machine

Abstract

A motorized walnut cracking machine was designed and developed to overcome the drudgery and huge time involved in traditional walnut cracking and the prototype was evaluated under three different levels of shell moisture content (db) (25-30%, 15-20% and 8-12%) and three different levels of roller speeds (25 rpm, 43 rpm and 69 rpm) of the cracking unit. The main components of machine involves motor, frame, hopper, conveying tray, cracking unit, conveying chute and collecting bin. The working principle of cracking unit is based on the compression of the walnut between two rollers rotating in opposite direction. Sphericity coefficient for soft shelled, medium shelled and hard shelled walnut were 0.850, 0.845 and 0.857, respectively. The geometric mean diameter and mean angle of repose of different categories of walnut was observed as 32.95 mm and 52.66°. The rupture force was observed minimum (90.16 N) along Z-axis (suture line) and at 8-12 % (d.b) shell moisture content while it was found maximum (200.90 N) along X-axis and at shell moisture content of 25-30% (d.b). The throughput capacity of the machine significantly increased with rotational speed of the rollers. The cracking efficiency was found highest (82.1 %) at 43 rpm and 15-20%   shell moisture content, while it was lowest (70.9 %) at 63 rpm and 8-12% (d.b) shell moisture content. The kernel damage increased linearly with the rotational speed of roller and found highest (21.8 %) at 69 rpm and 8-12 % (d.b) shell moisture content, while it was lowest (11.7 %) at 25 rpm and 15-20 % (d.b) shell moisture content. At standardized speed of operation (43 rpm) and shell moisture content (15-20%), the throughput capacity of the machine was recorded as 56.1kg/h with cracking efficiency of 82.1% and kernel damage of 13.8%. While throughput capacity observed with traditional method was 2.5 kg/h with cracking efficiency of 85.9%, and kernel damage of 8-9 %.