Mechanism of low damage rate maize ear pre-threshing based on cob internal expansion cracking

Abstract

During mechanical threshing of maize, the connection forces between the kernels and the cobs, along with the mutual support forces among the kernels, are crucial factors determining the applied force by the threshing elements, impacting the extent of kernel damage. Currently, solutions aimed at reducing or eliminating the mutual support forces among kernels to minimise threshing damage have not been found. Thus, this study proposes a novel pre-threshing method involving the cob's internal expansion to split the maize ears into fragments to achieve partial threshing and diminish the mutual support forces among the kernels. A detailed analysis is conducted on the impact of kernel arrangement, position, and support quantity on both intact maize ears and maize ear fragments concerning stripping forces. Furthermore, based on the comprehensive force analysis on the process of fragmenting the maize ear from the internal, we have designed and fabricated a new test device. Experiments were performed on comparing three types of maize ears through 4-, 6-, and 8-bulging wedges on the expanding rod, respectively. Results indicated that the number of maize ear fragments ranged from 13 to 18 for TK 601 maize ears. As the number of wedge elements increased, fragment size decreased, with the average number of kernels per fragment reducing from 38 to 15. The proportion of individually detached kernels increased from 18.16 % to 55.89 %, while the kernel damage rate had a slightly increase from 0.08 % to 0.96 %. Similar trends were observed in the other two types of maize ears. This study provides a new solution for achieving low-damage threshing of maize.