A Technique Of Isothermal Extrusion Pre-forming And Optimization Of Mould Structure For Globoidal Indexing Cams Parts

At present, automation equipments made in our country are normally equipped with worm gear mechanisms, which have bigger clearances between the positive and negative directions and worse resisting torque ability at work. Moreover, because of the laggard technical means of manufacturing and assembly, the homemade worm gear mechanisms are much worse than the international high-quality ones in the respects of indexing accuracy, repeated indexing accuracy and loading capacity. Because of the inextensibility of the contour surface of the globoidal cam, Bar preforms mostly are used to be machined on CNC machine tools or shaped milling machine in the conventional cutting technique. Then the remaining material to be removed is great, and the metal streamlines of the bar preforms will be destroyed during the cutting process. thus the components compositive mechanism performance are affected. So the multi-axis NC machines must be used to make a high accuracy globoidal cam, but the technique costs restrict its popularization by a long way. Along with the broad application in the CNC machine tools and the packing mechanisms, globoidal cams have shown its superiority such as high efficiency,high accuracy and high stable performance in the high-speed intermittent mechanisms. Until recent years, the researches and the discussions of the machining technique methods for globoidal cams have further being developed in our country. This paper proposes a technique method called isothermal extrusion to make preforms, and optimize the mould structure by using MSC.Marc FEM software. According to the research on this type of driving mechanisms, the main work of the paper is as follows:(1)Deducing the curve equation of contour surface of the globoidal cam : applying the meshing property between the cam and rollers, and the turn-back principle if the cam is static, the rollers turn back and swing around the cam's axis at the same time, and derivate the globoidal cam mechanisms surface curving equation.(2)Establishing the pre-forming technique of the globoidal cam: use K₃-alloy as the structure material of the Half-mould, and heated the base material as GCr15 to 750±200C so on, then use the Isothermal Extrusion Pre-forming to gain the preforms of the globoidal cam under P = 190t.(3) Using the MSC.Marc FEM software to analyze and certificate the feasibility of isothermal extrusion technique, and optimize the concave mould cavity. The emphases is the effect to the fill performance of the isothermal extrusion technique, and ensure the favorable filling performance by perfecting the size of the mould.