At present, the production efficiency of spiral gear processing method in China is low, and the accuracy of processed gear is poor, which has a great impact on the quality of related products. Therefore, it is of great significance to study the manufacturing technology of precise and complex spiral surface and develop new equipment to improve the manufacturing level of high-grade CNC machine tools and meet the market demand. In 2010, Shaanxi Hanjiang Machine Tool Co., Ltd. successfully designed and developed the first CNC screw rotor grinder sk7032 in China, which can grind the screw rotor, worm, spiral gear, etc., filling in the domestic blank, breaking the monopoly position in the field of high-precision complex spiral surface grinding and the dilemma of long-term dependence on imports of such machines.
Because of the complexity and diversity of workpiece surface, the key of forming grinding technology is the dressing of wheel profile . The common dressing methods of grinding wheel include turning dressing, grinding dressing, extrusion dressing, diamond roller forming dressing, online electrolytic dressing, etc. Generally, the turning and dressing tool is a diamond pen, which can finish the sand profile by the movement of the tip along the required path of the workpiece profile. The advantages of turning method are smooth surface, high efficiency, low size and precision of grinding wheel, and poor grinding performance. It is suitable for the dressing of silicon carbide and alumina grinding wheel. The roller forming extrusion method is to extrude and contact each other between the roller and the grinding wheel to roll, and to extrude or crush the sand particles so as to trim the profile of the grinding wheel. Generally, high carbon steel, cr-w-mn steel and high speed steel are used to make rollers, which have short service life. During extrusion, if the roller is active, the grinding wheel motor stops; if the grinding wheel is active, the rotation speed of the grinding wheel should be reduced to the speed required for extrusion. During the shaping and dressing of diamond roller, the roller rotates at high speed, the wear is even and the amount of single particle dressing is very small, which reduces the friction heat and friction and prolongs the service life of diamond. The manufacturing accuracy of diamond roller has been greatly improved with the development of manufacturing technology, and its contour accuracy has reached 0.002mm. The on-line electrolytic dressing method is mainly used in the dressing of grinding wheel with metal bond super hard abrasive. This method has the advantages of simple process, high efficiency, small dressing force and high dressing quality.
Before the popularization of numerical control technology, the researchers mainly studied the profiling of grinding wheel. China Machine Tool Works has developed a kind of wheel dresser and designed a model curve for grinding spur gears, but it is very inconvenient for grinding. Han Qingyao proposed to use an imaginary involute to approximate the theoretical profile of the wheel, improve the manufacturing accuracy of the model and reduce the grinding error. The smaller base circle involute is used to replace the involute of the gear to be ground, that is, to replace the involute grinding method, It is used to realize grinding wheel modification and improve grinding accuracy. At this time, there are many problems in the grinding wheel dressing, such as the low accuracy of the sample curve, the complex structure design of the wheel dresser, the low grinding efficiency and high cost. With the development of numerical control technology, grinding wheel dressing has gradually stepped into the stage of numerical control dressing. For example, in 1979, the former West Germany M. week and others first developed a numerical control grinding wheel dressing device. By using mathematical model and interpolation program, the computer-controlled servo system drives the diamond pen to move to repair the cutting shape of the grinding wheel to achieve the dressing of the grinding wheel; the former West Germany Kapp company’s vag and vas CNC forming grinding machine, SRS series CNC large plane grinding machine of Hult company, gs-36n CNC forming plane grinding machine of Japan Da Yu iron works Institute, etc. are all equipped with CNC Grinding wheel dresser; n. Nishida et al. Based on the spatial meshing principle of the spiral surface of the workpiece and the turning surface of the grinding wheel, derived the contact line equation of the workpiece and the grinding wheel in the grinding process, and studied and analyzed the influence of the installation error of the grinding wheel on the profile accuracy of the workpiece; h. Yoshino et al. Proposed the compensation method for the profile and position of the grinding wheel; domestic research is devoted to the formation grinding of the internal gear sand In the process of wheel dressing, we have successfully designed a diamond wheel dressing device and developed a dressing program to realize NC wheel dressing; Nanjing University of technology has carried out optimization research on contact line in the grinding process; at present, there are still deficiencies in wheel dressing, many problems have not been analyzed and tested, and further research and development are needed.