Research On Pulse Laser Assisted Micro Machining Of ZrO₂ Ceramic

To meet the material diversification, three-dimensional structure, complicated function and batch flexibility of the micro mechanical parts, micro cutting technology for the following advantages: the high machining accuracy, low manufacturing cost, high processing efficiency, three dimensional processing ability and wide application scope of workpiece materials, has developed rapidly in recent years, and gradually becomes the important means of micro machining. However, for the difficult-to-machine materials, such as high temperature alloys, ceramics and composites, as machined by micro cutting, the low processing efficiency, poor surface quality and serious tool wear have been found. With the rapid advancement of laser technologies in recent years, laser assisted machining(LAM) has begun to emerge as a viable industrial option for machining of difficult-to-machine materials. In LAM, a laser provides intense localized heating to the workpiece. The higher temperatures created by the laser lead to a reduction in strength in the heated regions, thus leading to a reduction in tool wear, an increase in machining quality and efficiency. This paper mainly combines the laser assisted machining with the micro cutting, to carry out the basic research on pulse laser assisted micro machining, the main work and achievements as follows:(1) Based on the heat transfer control equations and the corresponding theory of heat transfer, the quasi steady state heat transfer model in laser assisted micro machining is built. Using finite difference method, the quasi steady state heat transfer model of LAM is solved, and the finite difference equation of the quasi steady state heat transfer model is established. The finite difference equation is solved, and the temperature field created by laser simulation software is designed.(2) Based on the designed temperature field simulation software, the surface temperature field, cross-section temperature field and longitudinal-section temperature field of the Zr O2 ceramic heated by pulse laser is simulated analyzed, and the influence on the surface temperature field and internal temperature field of the Zr O2 ceramic by the single pulse energy, laser spot diameter, laser scanning speed is studied. With the infrared temperature measurement method, the highest surface temperature of the Zr O2 ceramic heated by pulse laser under different single pulse energy and scanning speed is measured, and the relationship between the simulation value and actual value is comparative analyzed. The results show that the measured temperature value and simulation value basically trends, but the actual measured value is slightly lower than the simulation temperature value.(3) Based on the two axes ultra-precision micro cutting experiment platform and the pulse laser heating system, the pulse laser assisted micro cutting system is set up. According to machining conditions and requirement, the CBN cutting tools is selected. According to the simulation results and measured results, the selection scope of process parameters of pulse laser assisted micro cutting Zr O2 ceramic is determined.(4) The experiments of pulse laser assisted micro cutting Zr O2 ceramic are conducted. The cutting force, tool wear, surface roughness and surface by the conventional micro cutting and pulse laser assisted micro cutting quality are comparative analyzed. Moreover, the influence on the cutting force and surface roughness by the single pulse energy, cutting speed, cutting depth and feed rate is studied. According to simulation and experimental results when machining Zr O2 ceramic by LAM, it is concluded that the optimal parameters are: laser spot diameter is 0.75 mm, single pulse energy is 0.06~0.08 m J, cutting speed is 0.063~0.126m/s, cutting depth is 0.005~0.01 mm, and the feed rate is 0.01~0.02 mm/r.