Design and Experimental Evaluation of a Corn Ear Core-Splitting–Threshing Device for High-Moisture Maize

To address the high kernel breakage rate and incomplete threshing of high-moisture maize ears, a low-damage core-splitting–threshing method was proposed, and a maize-ear core-splitting device based on the internal expansion action of a splitting cone was developed. During operation, the splitting cone was screwed axially into the cob, and a radial splitting load was applied to the cob interior through thread-induced self-feeding and conical wedging, dividing the intact ear into several block-like segments and thereby weakening the kernel–cob connection and the supporting constraints among adjacent kernels. The main structural parameters of the splitting cone and clamping and conveying mechanism were determined through theoretical analysis. The discrete element method was used to investigate the core-splitting process at different splitting-cone rotational speeds, and core-splitting and subsequent threshing tests were conducted at kernel moisture contents of 25–30%. As the splitting-cone rotational speed increased from 150 to 650 r/min, the simulated and measured cob fragmentation degrees increased from 5 to 11 and from 6 to 11, respectively, while the measured kernel damage rate remained below 1.0% under all core-splitting conditions. In the subsequent threshing tests, the mean kernel breakage rate and unthreshed kernel rate of the core-split treatment group were 4.75% and 1.55%, respectively, representing reductions of 44.0% and 15.8% compared with 8.49% and 1.84% for the unsplit control group. Analysis of variance showed that threshing-element type had highly significant effects on both the kernel breakage rate and unthreshed kernel rate, while drum rotational speed and cob fragmentation degree had significant effects on both responses. Type C movable spike teeth exhibited good compatibility with core-splitting pretreatment, with mean kernel breakage and unthreshed kernel rates of 3.52% and 1.30%, respectively, corresponding to reductions of 48.6% and 18.9% relative to the corresponding unsplit controls. Increasing the cob fragmentation degree reduced both response indices, whereas increasing drum rotational speed reduced the unthreshed kernel rate but increased kernel breakage. Multi-objective optimization identified the optimal parameter combination as the Type C threshing element, a drum rotational speed of 1000 r/min, and a cob fragmentation degree of 11. Under these conditions, the predicted kernel breakage rate and unthreshed kernel rate were 3.30% and 1.18%, respectively, with an overall desirability of 0.939. These results provide a reference for pre-threshing core-splitting pretreatment of high-moisture maize ears and for the design and parameter matching of low-damage threshing devices.