Via material erosion in wire electrical discharge machining(WEDM),recast layers form on the surfaces of workpiece.In addition,ultra fine Wire-EDM can be usually cut once.To reduce the thickness of the recast layer as ...Via material erosion in wire electrical discharge machining(WEDM),recast layers form on the surfaces of workpiece.In addition,ultra fine Wire-EDM can be usually cut once.To reduce the thickness of the recast layer as much as possible,the wire electrical discharge-electrochemical machining(WEDCM)method was proposed,which is based on the micro conductivity of the dielectric and microelectrolytic characteristics by adjusting the no-load rate of the pulse in the machining process.Furthermore,a state discrimination and servo control system based on discharge current was designed.The experiment results of different no-load rates show that the electrolytic effects increase as the no-load rate increases,and the main machining process is spark discharge erosion with a no-load rate in the range of 10%to 80%.At 90%no-load rate,the amount of recast layer formation in the forward direction of the wire electrode is almost the same as that of electrolytic dissolution,and it can be practically processed without a recast layer.Compared with10%no-load rate,the kerf width only increases by 7.5%.展开更多
Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone.However,a detailed comparison betwee...Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone.However,a detailed comparison between nanosecond and picosecond laser drilling techniques has rarely been reported in previous research.In the present study,a series of micro-holes are manufactured on stainless steel 304 using a nanosecond and a picosecond laser drilling system,respectively.The quality of the micro-holes,e.g.,recast layer,micro-crack,circularity,and conicity,etc,is evaluated by employing an optical microscope,an optical interferometer,and a scanning electron microscope.Additionally,the micro-structure of the samples between the edges of the micro-holes and the parent material is compared following etching treatment.The researching results show that a great amount of spattering material accumulated at the entrance ends of the nanosecond laser drilled micro-holes.The formation of a recast layer with a thickness of;5μm is detected on the side walls,associated with initiation of micro-cracks.Tapering phenomenon is also observed and the circularity of the micro-holes is rather poor.With regard to the micro-holes drilled by picosecond laser,the entrance ends,the exit ends,and the side walls are quite smooth without accumulation of spattering material,formation of recast layer and micro-cracks.The circularity of the micro-holes is fairly good without observation of tapering phenomenon.Furthermore,there is no obvious difference as for the micro-structure between the edges of the micro-holes and the parent material.This study proposes a picosecond laser helical drilling technique which can be used for effective manufacturing of high quality micro-holes.展开更多
基金the National Natural Science Foundation of China(Nos.51575271 and 51975290)。
文摘Via material erosion in wire electrical discharge machining(WEDM),recast layers form on the surfaces of workpiece.In addition,ultra fine Wire-EDM can be usually cut once.To reduce the thickness of the recast layer as much as possible,the wire electrical discharge-electrochemical machining(WEDCM)method was proposed,which is based on the micro conductivity of the dielectric and microelectrolytic characteristics by adjusting the no-load rate of the pulse in the machining process.Furthermore,a state discrimination and servo control system based on discharge current was designed.The experiment results of different no-load rates show that the electrolytic effects increase as the no-load rate increases,and the main machining process is spark discharge erosion with a no-load rate in the range of 10%to 80%.At 90%no-load rate,the amount of recast layer formation in the forward direction of the wire electrode is almost the same as that of electrolytic dissolution,and it can be practically processed without a recast layer.Compared with10%no-load rate,the kerf width only increases by 7.5%.
基金Supported by National Basic Research Program of China(Grant No.2011CB013004)National Natural Science Foundation of China(Grant No.51005130)Research Fund of State Key Laboratory of Tribology,Tsinghua University(Grant no.SKLT12B06)
文摘Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone.However,a detailed comparison between nanosecond and picosecond laser drilling techniques has rarely been reported in previous research.In the present study,a series of micro-holes are manufactured on stainless steel 304 using a nanosecond and a picosecond laser drilling system,respectively.The quality of the micro-holes,e.g.,recast layer,micro-crack,circularity,and conicity,etc,is evaluated by employing an optical microscope,an optical interferometer,and a scanning electron microscope.Additionally,the micro-structure of the samples between the edges of the micro-holes and the parent material is compared following etching treatment.The researching results show that a great amount of spattering material accumulated at the entrance ends of the nanosecond laser drilled micro-holes.The formation of a recast layer with a thickness of;5μm is detected on the side walls,associated with initiation of micro-cracks.Tapering phenomenon is also observed and the circularity of the micro-holes is rather poor.With regard to the micro-holes drilled by picosecond laser,the entrance ends,the exit ends,and the side walls are quite smooth without accumulation of spattering material,formation of recast layer and micro-cracks.The circularity of the micro-holes is fairly good without observation of tapering phenomenon.Furthermore,there is no obvious difference as for the micro-structure between the edges of the micro-holes and the parent material.This study proposes a picosecond laser helical drilling technique which can be used for effective manufacturing of high quality micro-holes.
