Grinding on the impact of die life

Author: admin    NewsSource: Site author    Hits:     Updated: 8/10/2009

Workload will die of the total manufacturing time by 25% ~ 45%. China's industrial development of molds made great progress, but still with foreign advanced level have a greater gap between the life in the mold are compared in Table. Building is a continuation of die design is to verify the correctness of the design process. In the modern mold used in the production of advanced, high efficiency, high precision machine tools and automated production technology. Grinding workload will die of the total manufacturing time by 25% ~ 45%. China's industrial development of molds made great progress, but still with foreign advanced level have a greater gap between the life in the mold are compared in Table. The quality of the finished mold and die manufacturing is closely related to accuracy, especially with the mold cavity surface accuracy and surface roughness is closely related.

 

 The actual production, the impact of die failure factors: die structure; Die material; manufacturing process of hot and cold processing (forging, heat treatment, machining, grinding, EDM, etc.); mold working conditions. To improve die life, must lead to mold damage and all kinds of reasons for a careful analysis of the factors affecting the development of methods and measures to overcome.

 

 At present, there are two in the international mold manufacturing process line: First, to improve machining accuracy and the processing power and quality, so that the workload of manual finishing to a minimum, such as high-precision machine tools and high-speed molding machine and its processing technology The development of this technology lay the foundation for the development of the road. The second is focusing on roll forming machine finishing and polishing in the polishing process, the processing time, and mechanical processing, EDM is almost the same time. Mold is a large group with the parts from, the quality of parts with a direct impact on the quality of mold, and ultimately the quality parts to guarantee finishing in turn. Most of the mold in the domestic manufacturing enterprises, finishing stage of the method used is generally grinding, EDM and fitter to deal with.

 

 Grinding of die life of the people did not pay full attention to, as a result of incorrect grinding, resulting in surface burns, grinding cracks, grinding marks and production of grinding stress, resulting in the follow-up process and die in the service during the mechanical fatigue, cold and fatigue crack initiation sources have seriously affected the life of mold.

 

 Study and explore ways to improve the quality of grinding to improve the die service life, extended service hours, promote the use of new technology tool, it is the purpose of this article.

 

 1, die grinding

 

 The essence of the process of grinding the workpiece by grinding the metal surface, abrasive countless moments in the extrusion, the friction generated under deformation, and then to wear debris, and the process of the formation of smooth surface. The entire process of grinding and thermal performance of the role.

 

  In the grinding process, the processing surface in the cutting heat generated under thermal expansion, when the low temperature metal matrix, therefore, the surface of hot-pressing stress. When grinding the end of the workpiece surface temperature decreased, the surface has been generated as a result of hot plastic deformation and are subject to restrictions on the matrix, therefore the surface of the residual tensile stress, resulting in residual compressive stress layer.

 

  grinding, the grinding wheel and workpiece contact for Globoidal, cutting wheels have a plastic deformation of workpiece and grinding wheel and workpiece of the frictional resistance between the intense, grinding wheel and workpiece in forming the same size, the grinding force in opposite directions at the same time as a result of surface plastic deformation when the material so that the internal metal workpiece material relative displacement between the elements, the formation of internal friction and heat, grinding wheel and workpiece also produced friction between the outside heat, such grinding heat in the grinding zone will have up to 1000 partial of the instantaneous high temperature, while the wheel is hard to heat, so 80% of the heat into the workpiece and the wear debris, and metals in the solid-state changes with temperature of a crystal lattice by a lattice into another, the occurrence of changes in microstructure in grinding of hardened steel, cooling sufficient secondary hardening the surface layer, some of the residual austenite into martensite, and martensite in a larger volume, specific volume increased, the surface compressive stress, if the mill cut cooling properly, or do not have the cooling fluid, surface tempering, martensite transformation occurs, the surface tensile stress (such as Fe into Fe, when the volume of iron would grow 1%), the stress (residual stress can be reached 500 ~ 1000 MPa), if more than the material yield limit, they have a grinding cracks, while heat treatment did not die immediately after quenching tempering, quenching temperature is too high, there are mesh carbonation, did not temper tempering Markov or too much residual austenite in the grinding phase change from time to time we have, the occurrence of stress cracks so that the workpiece surface. Grinding crack is a very small surface cracks, grinding cracks are generally three kinds of patterns: parallel lines like, network-like cracks, eight-shaped crack. The occurrence of crack direction and shape of the mold, the direction of development of cracks and the surface of grinding wheel in the direction of the workpiece, and its depth of less than 0.03 mm.