SLM成形打印件振动辅助磁力研磨试验

Experimental on Vibration-assisted Magnetic Abrasive Finishing of Printed Workpiece Formed by SLM

目的研究使用振动辅助磁力研磨去除选区激光熔化(SLM)成形打印件表面的未熔融粉末时,各加工参数对试样表面粗糙度降低率和表面形貌的影响。方法结合波导管工件,采用SLM成形打印AlSi10Mg试样,并利用自行研制的振动辅助磁力研磨装置进行加工间隙、磁极转速、振动频率、加工时间等4个因素各5个水平的单因素试验,以表面粗糙度降低率为评价指标,探究各加工因素对试样表面粗糙度降低率和表面形貌的影响规律。结果对于采用选区激光熔化成形的试样来说,当加工间隙从3 mm增大到7 mm时,试样的表面粗糙度降低率显著降低,最大降低率为84.7%,最小降低率为6%。当加工间隙为3 mm时,试样表面的未熔融粉末基本去除,表面较平整。当磁极转速从200 r/min增大到1000 r/min时,表面粗糙度降低率先增大后趋于稳定,在转速为200 r/min时表面粗糙度降低率最小(24.3%)。当转速达到400 r/min甚至更高时,表面粗糙度降低率趋于稳定,表面粗糙度降低率保持在80%左右。表面粗糙度降低率随着振动频率增大的变化情况较为复杂,但是总体呈现先增大后减小的趋势,并且在振动频率为15 Hz时,表面粗糙度降低率最大(84.7%)。当加工时间从10 min增大到50 min时,表面粗糙度降低率呈现先增大后减小的变化趋势,在加工时间为40 min时,表面粗糙度降低率最大(81.7%)。结论加工间隙、磁极转速、振动频率和加工时间对表面粗糙度降低率都有不同程度的影响,SLM成形的试样经过振动辅助磁力研磨之后,表面粗糙度显著降低,表面未熔融粉末得到有效去除。

The forming and inner surface polishing of workpieces with complex internal cavity structures has always been a problem that troubles the academic community.Complex parts can be formed by metal additive manufacturing technology,but unfused powder remainsand the surface is very rough,which seriously affects the workpieces'performance.In this paper,the influence of vibration-assisted magnetic abrasive and polishing parameters on the processing results during polishing is studied for the polishing of irregular waveguide internal surfaces with complex internal cavities formed by selective laser fusion coagulation.Based on the basic theory of vibration-assisted magnetic abrasive finishing,a single-factor experiment was carried out using a self-developed experimental device for vibration-assisted magnetic abrasive finishing.To restore the machining conditions of the waveguide as much as possible,the object of the single-factor experiment is the profiled AlSi10Mg sample and the size of the polishing area is the same as the size of the inner cavity of the waveguide.A special fixture is designed for the samples,and the machining gap can be adjusted flexibly.To improve the polishing efficiency and obtain good polishing results,steel balls are used as magnetic abrasives,and surface roughness reduction rate is used as an evaluation index.The experiment explores the influence of four factors of machining gap,magnetic pole rotating speed,vibration frequency,and machining time at five levels each on the surface roughness reduction rate and surface morphology.The results of the vibration-assisted magnetic abrasive finishing based on steel balls are as follows.For samples formed by selective laser melting,with the machining gap increasing from 3 mm to 7 mm,the surface roughness reduction rate is significantly reduced,the maximum reduction rate is 84.7%,and the minimum is 6%.When the machining gap is 3 mm,the unfused powder on the surface of the sample is almost completely removed at this machining gap,and the surface is relatively flat.When the magnetic pole rotating speed increases from 200 r/min to 1000 r/min,the surface roughness reduction rate increases firstly and then tends to be stable.When the magnetic pole rotating speed is 200 r/min,the surface roughness reduction rate is the smallest,which is only 24.3%.When the magnetic pole rotating speed reaches 400 r/min or higher,the surface roughness reduction rate tends to be stable,and the surface roughness reduction rate remains at about 80%.When the magnetic pole rotating speed is 800 r/min,the surface roughness reduction rate reaches a maximum of 85.3%.The change of the surface roughness reduction rate with the increase of the vibration frequency is more complicated,but the overall trend is that it first increases and then decreases.When the vibration frequency is 15 Hz,the surface roughness reduction rate reaches the largest,which is 84.7%.When the machining time is increased from 10min to 50 min,the reduction rate of surface roughness showed a trend of first increasing and then decreasing.When the machining time is 40 min,the reduction rate of surface roughness is the largest,which is 81.7%,and the unfused powder is almost completely removed,and the surface roughness reduction rate will decrease due to the over-polishing of the steel balls.The results show that the machining gap,magnetic pole rotating speed,vibration frequency,and machining time all have different degrees of influence on the reduction rate of surface roughness and surface morphology.After vibrationassisted magnetic abrasive finishing,the surface roughness of samples is significantly decreased,and unfused powder on the surface is effectively removed.