CVD matching analysis of worm grinding and dressing roller based on sector concentric-ring model

Objectives: As the core component of major equipment, the tooth surface accuracy of gears is ultimately guaranteed by the gear grinding process. The electroplated worm grinding roller is an indispensable precision machining tool for dressing worm grinding wheels, which indirectly plays a decisive role in the machining quality and manufacturing cost of gears. However, the tooth shape of the electroplated worm grinding roller is triangular, which leads to several issues: the adhesion difficulty of abrasive particles at the top of the tooth increases significantly, the distribution of abrasive particles becomes sparse, and the dressing condition deteriorates. The isolated abrasive particles at the top of the tooth resemble a cantilever beam structure and are easily dislodged during the dressing process. As a result, the abrasive particles at the top of the roller tooth fail earlier than those on the sides of the tooth, leading to premature roller wear and scrapping, which seriously affects the manufacturing cost of the gear. To address these issues effectively, this study uses CVD (chemical vapor deposition) reinforced material embedded composite electroplating technology to manufacture worm grinding rollers, guided by the CVD matching theory to improve the grinding stability of the rollers. Methods: First, the equivalent wear model of CVD and diamond abrasive particles is established. Then, the abrasive particle distribution theory model of electroplating worm grinding and dressing rollers is developed using the sector concentric ring model. Next, the CVD matching model is derived through rigorous mathematical formulation. However, since the theoretical model of abrasive particle distribution is complex and difficult to solve, the assignment method is used for more detailed theoretical analysis. Finally, the accuracy of the model is verified through practical applications. Results: (1) The CVD matching quality is closely related to several parameters, such as the relative material properties, electroplating process level, diamond abrasive crystal type characteristics, and roller structure. Among these, material properties, electroplating process level, and abrasive crystal type are relatively fixed. Therefore, in practical engineering applications, emphasis should be placed on the relationship between the number of CVD inserts and the geometric parameters of the worm gear grinding roller structure. (2) When the CVD material is determined, the matching number is primarily influenced by the roller module, with a certain linear negative correlation to the roller module. Additionally, there is a weak negative correlation with the radius R of the CVD arc of the roller, while the relationship with the pressure angle of the machined gear is not significant. (3) When the modulus m_n and the arc radius R are both 0.80 mm, the matching number K of CVD in the roller is most suitable between 40 and 50 grains. When the pressure angle or tooth tip arc is too small, the number of CVD inlays should be appropriately increased. Generally, the change in the number of CVD inserts due to the pressure angle is no more than 10%. At the same pressure angle, when R is 0.50, 0.20, and 0.10 mm, the K value is 1.3, 2.2, and 3.3 times that when R is 0.80 mm. (4) The application verification of the trimming roller shows that when the CVD embedding quantity K reaches ROUNDUP (K_min) or more, the service life of the trimming roller remains largely unchanged with the increase of K. Conversely, when K is reduced, the service life of the trimming roller decreases significantly. When the CVD quantity K decreases by 15%, the service life of the trimming roller is reduced by 17.6%. (5) When dressing the grinding wheel under the same dressing process parameters, the service life of the dressing roller is judged based on the number of dressing cycles after which either grinding burn or tooth profile accuracy deviation occurs. A slight difference of 5% is observed between the actual verification results and the theoretical model results. Based on this, the CVD matching quantity of the roller can be designed according to theoretical calculation results in engineering practice. This ensures proper matching of the tooth tip and side loss of the roller while allowing for a repair margin for failed rollers, effectively reducing tool manufacturing costs. Conclusions: The fan-shaped concentric ring CVD matching model simulates the actual distribution of abrasive particles and CVD inserts in worm grinding rollers and introduces the relative wear performance index between diamond abrasive particles and CVD materials. The established model effectively predicts the top and side wear of CVD grinding rollers, enabling the calculation of the appropriate number of CVD inserts. This helps guide the design of worm gear grinding rollers. The model's accuracy is verified through practical applications, and its results can be applied to optimize the grinding process, reduce tool manufacturing costs, and improve the stability and efficiency of worm gear production.