A Design And Application Of The Equipment For Cryogenic Cooling

Low efficiency, fast tool wear and poor stability of the processing quality are series of problems in the machining process of difficult-to-cut materials, such as titanium alloys. Cryogenic cutting technology has many distinctive advantages in reducing tool wear and improving surface quality. However, cooling effect of existing cryogenic refrigeration equipment is limited and it is difficult to control the jet temperature. In order to explore the processing results of high feed milling of titanium alloy in different jet temperature, this paper aims to design a temperature-controlled cryogenic internal cooling cutting equipment and both internal cooling and external cooling can be achieved. The technology on cryogenic high feed milling of TC4 alloy is deeply studied by this equipment. What’s more, processing performance of high feed milling of titanium alloy deep cavity is analyzed in cryogenic internal cooling. The main research works are listed as follows:(1) According to the technical defects of the existing cryogenic gas generating devices and actual processing technology needs of difficult-to-machine materials, a cryogenic gas Jet cooling and lubrication system whose temperature is controllable is designed. By controlling the air jet ratio of cryogenic liquid nitrogen and normal-temperature air, a cryogenic gas supply from-196℃ to normal temperature can be achieved and then cooling and lubrication of the cutting zone can be realized by internal and external cooling.(2)The milling experiment of TC4 under different jet temperature is carried out to optimize cryogenic jet which shows good processing properties. The optimized cryogenic jet is then used in high feed milling test of TC4 that will reveal the influence of cutting parameters on cutting force and cutting temperature as well as the effect of milling length on tool wear. Meanwhile, processing effects under the optimized cryogenic jet and traditional emulsion are analyzed and compared. Besides, the study of low temperature performance based on typical parts of titanium alloy is conducted. These tests verified that advantages of high feed milling of TC4 are obvious under optimized cryogenic jet.(3) Based on tests of cutting force, tool wear and surface roughness, processing properties of titanium alloy deep cavity widget are studied under cryogenic internal and external cooling. Results showed that when cryogenic liquid nitrogen internal cooling mode is used in milling of TC4 deep cavity widget, good machined surface quality is got and tool wear is significantly reduced.