Motion force analysis and simulation of dry-cured ham during knead processing

Yunnan Ham is one of China′s 3 best-known brands of dry-cured hams. Over many years, the production of Yunnan Ham has relied on the manual skills of workers. Therefore, the production process is confronted with such problems as inefficiency, extremely high salinity, and instability in quality. Because of the impact of other domestic and foreign ham brands, the market share of Yunnan Ham has been declining every year. Considering this situation, the Yunnan Agricultural University has developed a novel HTRZJ500 ham-kneading machine(hereinafter referred to as HTRZJ500) suited for the production features of Yunnan Ham. The HTRZJ500 operates based on the following principles: while dry-cured pig legs are conveyed on a belt, it is kneaded by a cam gear and pressure-rolling device located below and above the conveyor belt, respectively; the pig leg is kneaded and massaged through a combination of top kneading and roll kneading. Based on the anatomical structure of a Yunnan Ham and the structural dimensions of the kneading device, the pig leg model is divided into 4 kneading sections (i.e., A, B, C and D), and a working position graph for the 7 typical kneading positions used during the process is drawn, from feeding the pig leg onto the kneading area to the complete exiting of the pig leg through the second group of pressure rollers in the kneading area. As shown in the working position graph, there is a phase angle difference of 90° between the adjacent cams. The pig leg is jointly kneaded by 2 groups of cams and 2 groups of pressure rollers throughout the process, from the entry of Section A to the exit of Section D through the second group of cams. The pig leg experiences a wavelike kneading effect under the joint action of top kneading by cams and roll kneading by pressure rollers. Based on the working position graph and design parameters, the pig leg is top-kneaded approximately 36 times by the cams for 12 s. The 2 peak values of kneading force are 609 and 973 N. The Yunnan Agricultural University developed a SolidWorks-based virtual prototype of the ham-kneading device, and employed SolidWorks Motion to simulate the kneading process during which the pig leg passed through 3 groups of pressure rollers. The simulation time was 4 s, and the velocity diagram and acceleration diagram for the pig leg was obtained with the simulated variation curve for the kneading force. The following simulation results were obtained: (1) Both the velocity and acceleration of the pig leg changed in the vertical direction; the acceleration changed uniformly. The continuous up-down vibration of the pig leg helped in fully eliminating the accumulated blood in internal blood vessels, loosed the leg meat and caused rapid penetration and diffusion of salt into the leg meat. (2) The simulated variation curve of kneading force had 2 peak values (677 and 994 N), and the relative errors between simulation and calculated value of the working position graph were 10% and 2.1% respectively, proving the practicality of the kinematics simulation analysis model. This paper provides an in-depth analysis of the kneading process of the kneading machine developed for Yunnan Ham through a combination of diagrammatic method and virtual simulation technology. The research methods and ideas are very novel, and the research contents are significant for improving the mechanized production process of Yunnan Ham. The research conclusions provide theoretical and technical guidance for pilot production and structure optimization of the physical prototype of HTRZJ500 in the future study.