Design and evaluation of pneumatic impact‐twisting combined walnut fixed posture shell‐breaking mechanism

Abstract

The traditional walnut shelling methods, involving single‐stage or secondary processes, face challenges such as increased costs, uncertainties in shell positioning, and irregular crack expansion. To address these issues, this article introduces an innovative pneumatic impact‐twisting combined shelling method based on walnut fixed posture. The shelling mechanism design and orthogonal test were conducted, optimizing parameters like spring wire diameter (A), pressing head rotation angle (B), and cylinder locking air pressure (C) using evaluation criteria such as superior‐grade rate, intermediate‐grade rate, broken kernel rate, and shelling rate. Results indicate that the optimal shelling effect is achieved with a 3.5 mm steel spring wire diameter, a 100° downward pressing head rotation angle, and a 0.6 MPa cylinder locking air pressure on the pressure arm. The corresponding rates are as follows: superior‐grade rate 29.49%, intermediate‐grade rate 52.54%, broken kernel rate 10.14%, and shelling rate 91.04%. This study demonstrates that the pneumatic impact‐twisting combined walnut fixed posture shelling method improves post‐shelling quality, offering new design concepts for walnut shelling equipment.Practical ApplicationsThis introduces an innovative method that combines impact with twisting, and a pneumatic impact‐twisting combined walnut fixed posture shell‐breaking test device has been developed. Mechanical analysis was conducted for each stage of shell‐breaking. The research indicates that the pneumatic impact‐twisting combined method can enhance the production quality of walnut kernels after shell‐breaking. The test results indicate an improvement in the yield of 1/2 and 1/4 kernels compared to existing shell‐breaking methods. The inventive design of this shell‐breaking module contributes to the walnut kernel quality in the shell‐breaking production line, offering new methods and concepts for the design and advancement of walnut shell‐breaking devices.