Experimental Research On Micro-drilling And Ultra-precision Grinding Applying Machining Apparatus With Turbine-driven Air Spindle

With the rapid development of national defense,aerospace,microelectronics and precision instruments,higher requirements has been put forward on the micro holes and small diameter optical components.How to realize the high efficiency machining of micro holes and small diameter optical components is an important topic in the field of precision machining.Among which,micro-drilling and ultra-precision grinding have the advantages of high efficiency,high accuracy and good practicability.They are the effective processing methods to micro holes and small diameter optical components.Turbine-driven air spindle is supported by air bearing and driven by pneumatic turbine.It is suitable for micro-drilling and ultra-precision grinding because of its high speed,high accuracy and little thermal deformation.In order to verify machining performance and reliability of a homemade precision turbine-driven air spindle spindle,micro-drilling and ultra-precision grinding were carried out by using the spindle.And the influences of process parameters on machining quality were studied to optimize process conditions.The main contents are as follows:(1)The principle of the air spindle was introduced,the material removal mechanism of micro-drilling was analyzed,and the simulation of micro drill and the test principle of micro holes were ananlysed.Then the removal mechanism of the ultra-precision grinding and the principle of inclined axis grinding were analyzed.(2)A micro-drilling process using a turbine-driven air spindle was developed to improve drilling quality.Some drilling experiments for drilling 00.5 mm holes at magnesium alloy AZ31B sheet were carried out.Influences of rotational speed and feed rate on burr height at the exit of the micro-holes,aperture error and roundness error at the entrance were investigated.The aperture error and the roundness error were obtained by image processing and the least square method.Drilling parameters were optimized synthetically.The results show that performance of the spindle is in a good condition.When the rotational speed is 20000 rpm and the feed rate is 0.4 mm/s,the comprehensive quality of micro-drilling reaches the best.The burr height reaches 51.3μm,aperture error reaches 13.5 μm,and roundness error reaches 15.1 μm.The drilling quality is good,and it is feasible to use the spindle for micro-drilling.(3)Ultra-precision plane grinding experiments for tungsten carbide workpiece were carried out by using the spindle on a four axis ultra-precision machine.Influences of the wheel speed,feed rate and feed depth on the surface roughness by the single factor experiments.The optimum process parameters were obtained,and the parameters were applied to the ultra-precision grinding experiments of aspheric surface.The results show that the PV of the aspheric workpiece is 1.951 μM,and the Ra is 9.6 nm.The grinding quality is good,and it is feasible to use the spindle for ultra-precision grinding.