Development of a semi-automatic macadamia cracking machine

Abstract

Macadamia is the king of nuts and popular around the world. Cracking is vital to extract the whole nut and increases the commercial value of the product. Therefore, a semi-automatic macadamia cracking machine was designed and assessed. It was modified from a manual nut cracker. Such a machine was expected to have a higher throughput and produce a higher quality output. The key part of this machine consisted of a drive blade set and a nut discharge set, which were both upgraded so that they were driven by an electric motor. In extant machines, both these tasks are manual. We tested blade speeds of up to 22 rpm, macadamia nut diameters from 21 to 27 mm and the method to feed the nuts into the cracking section. The optimum cracking condition was found to be a 19 rpm blade speed or 19 cracking strokes per minute. The feeder handled 99% of the nuts successfully leading to a nut throughput of 10.6 kg/h, with 88% whole kernels. The best cracking performance was found on nut diameters in the range of 25 to 27 mm with a blade compression depth of 2.5 mm.