SLM增材制造微流道内表面磨粒流抛光工艺与机理

Polishing Process and Mechanism of Abrasive Flow on Inner Surface of Microchannel by SLM Additive Manufacturing

目的解决SLM增材制造复杂流向微流道粗糙内孔表面精加工难题。方法采用磨粒流抛光技术对SLM增材制造微流道内表面进行抛光,研究不同抛光压力下,磨粒流对微流道表面质量以及内孔形状精度的影响。利用FLUENT软件对磨粒的流动轨迹进行模拟,探究磨粒对微流道壁面的作用机理。结果在相同的抛光时间内,抛光压力增大,微流道的表面粗糙度随之减小,且趋向于收敛到一个最小值。直管处粗糙度可达0.23μm,弯管外侧为0.24μm,抛光效果明显。微流道内孔的最大内切圆直径与最小外接圆直径也随之增大,且直管处变化趋势相对平稳。在微流道弯管处,当抛光压力小于5 MPa时,最大内切圆直径与最小外接圆直径变化趋势较为平稳;抛光压力大于5 MPa时,最大内切圆直径与最小外接圆直径变化趋势较大,此时微流道内孔形状变形较大。结论在抛光时间为20 min,抛光压力小于5 MPa时,SLM增材制造微流道不仅具有良好的表面质量,而且微流道的内孔形状不会发生较大变形,形状精度较高,在此工艺条件下,能够符合加工要求。

Selective laser melting(SLM)technology provides an effective solution for the fabrication of microchannel heat exchanger.However,the polishing post-treatment of the inner hole surface of the microchannel with complex orientation has always been a technical problem which restricts its wide application.Abrasive flow polishing technology was applied to polish the inner surface of SLM additive manufacturing microchannel.The influence of abrasive flow polishing on the surface quality of microchannel and the shape accuracy of inner hole under different polishing pressure was studied.The flow trajectory of abrasive was simulated by FLUENT software to explore the mechanism of abrasive flow polishing on the wall of microchannel.In the same polishing time,the surface roughness of the microchannel decreases and tends to converge to a minimum value with the increase of polishing pressure.The roughness of the straight pipe can reach 0.23μm,and the outside of the elbow is 0.24μm.The polishing effect is obvious.At the same time,the maximum inscribed circle diameter and minimum circumscribed circle diameter of inner hole of microchannel increase,and the change trend of straight pipe is relatively stable.When the polishing pressure is less than 5 MPa,the change trend of the maximum inscribed circle diameter and the minimum circumscribed circle diameter is relatively stable.When the polishing pressure is greater than 5 MPa,the change trend of the maximum inscribed circle diameter and the minimum circumscribed circle diameter is large,and the shape of the inner hole of the microchannel changes greatly.When the polishing time is 20 min and the polishing pressure is less than 5 MPa,not only has microchannel good surface quality,but also its inner hole shape will not be deformed greatly,and the shape accuracy is better.Under this processing condition,it can meet the processing requirements.