Fine particle shot peening is one of the key technologies for high-performance gear manufacturing. In the study of gear dynamics and gear precision manufacturing, one of the important research topics is accurately analyzing the influence of fine particle shot peening on the normal contact stiffness of gear. In this paper, the changes of micro morphology of gear teeth surface before and after the fine particle shot peening were compared and analyzed through characterizing the micro morphology of the fine particle shot peened gear surface. Based on the fractal theory, the normal contact stiffness model of the fine particle shot peened gear was established considering the elastic-elastoplastic-plastic deformation of a single asperity and asperity interaction. It conducted a simulation analysis on the variation law of the normal contact stiffness along with the normal load, the fractal dimension D, the fractal rough amplitude G and the parameter of material property. The influence of fine particle shot peening on the normal contact stiffness of the gear was analyzed by extracting the fractal parameters of fine particle shot peened gear surface with the power spectral density function method. The results show that fine particle shot peening leads to randomly distributed micron or even nanoscale pits on the gear surface, and the decrease of surface roughness. Also, the gear surface roughness increases with the increase of fine particle shot peening strength. The normal contact stiffness increases with the increase of normal load, material yield strength, and fractal dimension D, and decreases with the increase of fractal roughness amplitude G. Fine particle shot peening can change the gear normal contact stiffness by changing the micro morphology of gear surface, and then change the fractal dimension D and fractal roughness amplitude G. Compared with the gear without fine particle shot peening, the normal contact stiffness of fine particle shot peened gears is improved. With the increase of shot peening strength, the normal contact stiffness of gears decreases. The research results provide a theoretical basis for gear dynamics research and high-performance gear manufacturing.

Rapid mold manufacturing can be used to print wax molds for investment casting, shorten the production cycle and improve the production efficiency. However, in the actual forming process, due to the uneven temperature distribution in different positions of the workpiece, the internal stress will be different, which may result in warping deformation, and then have a significant impact on the forming quality of the workpiece. Moreover, due to the constraints of forming parameters such as 3D printing speed and deposition layers’ number, it is difficult to reduce the degree of warping deformation of the workpiece and improve the forming efficiency simultaneously. To solve this problem, this paper establishes a mathematical model for the warping deformation of formed parts, and combines experimental design and mathematical calculation methods to explore the influence mechanism of printing speed on the degree of warping deformation and printing efficiency of casting wax direct writing. Experimental results show that, at a certain printing speed, the warpage value decreases with the increase of the number of deposition layers, while gradually increases with the continuous increase of printing speed; and that the higher the printing speed, the closer the printing time of different samples is to a certain stable value, which means that the impact of printing speed on the forming efficiency decreases with the increase of printing speed. In addition, by assigning weight coefficients respectively to the forming warping deformation and the printing efficiency, a continuous function model for the optimal printing speed of surface contours is established, and the effectiveness of the model is verified. The results show that the continuous function model of optimal printing speed based on the warping deformation of casting wax can simultaneously reduce the warping deformation and improve the printing efficiency.