Research On Heat Dissipation Performance Of Heat Pipe Cutter For Green Machining

To reduce the excessive cutting heat generation in cutting zone and to accelerate the cutting heat dissipation is an important issue needed to be addressed in machining process. The fluid cooling method used in traditional cutting process is not only costly, but also have very negative effect on the ecological environment and health of worker. In recent years, many cooling technologies in cutting process have been developed and, in some extent, proven to have great cooling effect. But the auxiliary equipment and the post-processing procedure used for purification and recycling of cooling medium for these technologies presents a great problem, which led to the reduction of equipment reliability and production cost increase, and, therefore, greatly limiting its application in practical production. In this case, it’s necessary to break through the restrictions of transitional thinking and develop the split-new cooling technology.The concept of heat removal through cutting tool and tool-holder is such an idea that meets this requirement. In recent years a small amount of exploration works about heat pipe cutter was carried out, these studies have proved that the cutting heat can be effectively dissipated, thus the cutting temperature and the thermal expansion of the tool can be reduced by using the heat pipe technology. However, due to the lack of in-depth study on the using parameter optimization of heat pipe, the structure optimization of heat pipe cutter and the quantitative analysis of cooling effect of heat pipe cutter, it is still unknown whether this device can be upgraded and used for practical production.In order to resolve the problems of structure design and the quantitative assessment of heat dissipation performance for heat pipe cutter, this paper focus on the using parameter optimization of heat pipe, the temperature field characteristic of prototype tool, heat pipe cutter design, the quantitative assessment of tool-chip interface temperature and heat distribution ratio for heat pipe cutters. Meanwhile, the design principles of heat pipe cutter were summarized and the effectiveness of heat dissipation for heat pipe cutter in cutting process was also evaluated.As the basis for heat pipe cutter design, the using parameters of heat pipe, such as the heat pipe length, the length of evaporator and the length of condenser were firstly optimized in this paper. With this purpose, the test system for heat pipe performance evaluation was established and the orthogonal experiment design was adopted, and then the maximum heat conduction power, thermal resistance and effective convection coefficient of different types of heat pipe in the force convection cooling condition and water recycling cooling condition were measured. According to the experimental results processed by the range analysis, the heat pipe using parameters was optimized. The researching result indicates that, with the synthetically consideration of the heat pipe performance and the geometry size of prototype tool, the heat pipe length of 150mm, evaporator length of 18mm and heat pipe bending angle of 5°were optimized in force convection cooling condition, meanwhile, the heat pipe length of 150mm, evaporator length of 18mm, condenser length of 20mm, recycling water temperature of 75℃and the heat pipe bending angle of 5°were optimized in recycling water cooling condition.In terms of the temperature field investigation for prototype tool, the effect of temperature on the surface emissivity of P10 carbide insert was firstly investigated. On this basis, the test system of infrared temperature measurement was established, and the temperature fields of prototype tool in the cutting process and the moment right after cutting out were measured. The experimental result indicated that, a steep temperature drop near the area of tool tip was observed, with the cutting speed increase, the maximum temperature magnitude in this area greatly increase. In the other side, the temperature gradient in the area far away from the tool tip is much lower, with the cutting speed increase, the average temperature magnitude in this area has litter change.On the aspect of heat pipe cutter design, the heat pipe cutter design principle was firstly proposed in combined consideration of the cooling performace, practical application, promotion and economy characteristic. Furthermore, a embedded heat pipe cutter, a lateral compressed heat pipe cutter and a slot-embedded heat pipe cutter, which based on the optimized using parameters of heat pipe and the temperature field characteristic of prototype tool, was designed and fabricated according to round micro-heat pipe, flat micro-heat pipe and prototype tool.In terms of the quantitative investigation of tool-chip interface temperature for heat pipe cutter, the inverse heat transfer resolving procedure, which integrated the artificial thermocouple temperature measurement technology, the finite difference numerical modeling and resolving technology, and the optimization solving method, was used for the interface temperature determination. Based on the procedure, the effect of cutting parameters, including cutting speed, feed rate and cutting depth, on the effective heat flux loaded on the tool-chip interface and the interface temperature of heat pipe cutter was investigated. The resolved results indicate that, with cutting speed and feed rate increase, the average heat flux loaded on the tool-chip interface and the interface temperature of these cutters increase correspondingly. With the cutting depth increase, the average heat flux loaded on the tool-chip interface and the interface temperature of these cutters have litter change. In general, under the same cutting parameters, the embedded heat pipe cutter has the maximum average heat flux the interface temperature, while the prototype cutter is has the minimum value.In terms of the quantitative investigation of heat distribution for heat pipe cutter, the dynamic cutting force experiment was first setup, and then the corresponding measured result was used to compute the cutting power, the total cutting heat and the cutting heat generated on the tool-chip interface. Meanwhile, the total heat flowed into the heat pipe cutter, the heat transfer by the heat pipe and the heat conduced into the tool-holder were determined based on the resolved result of the effective heat flux loaded on the tool-chip interface, the solution mechanism of finite difference method and the calorimetric experimental result for the heat pipe condenser. Furthermore, the heat distribution ratio for heat pipe cutter was computed and analyzed. The investigation results indicate that, the ratio between the heat flow into the tool-holder and the heat conducted into the tool is over 0.9 for the prototype tool, in contrast, when the embedded heat pipe cutter is used, this ratio sharply fell to about 0.6. Correspondingly, the ratio between the heat transferred by heat pipe and the heat conducted into the tool is over 0.25 for these three types of heat pipe cutters. In terms of this ratio, the embedded heat pipe cutter has the highest value among three heat pipe cutters, the ratio value range is about 0.38 to 0.42, and increase with the cutting speed increase.