Study On Abrasive Flow Polishing Process Of Micro Channel Inner Hole In SLM Additive Manufacturing

Industrial grade high flux microchannel heat exchanger has the advantages of small volume,light weight,compact structure and high heat exchange efficiency.It is widely used in high efficiency heat exchange links such as offshore oil platforms,hydrogen fuel cells,nuclear power,ships,large cloud computing and other fields,and has broad market prospects.The appearance of selective laser melting(SLM)additive manufacturing technology provides a new technology for the fabrication of microchannel heat exchanger.However,the surface of the inner hole in additive manufacturing microchannel is rough,which affects the liquid flow and heat exchange,so the inner hole wall needs subsequent finishing treatment.Due to the small diameter and complex trend of the inner hole in the heat exchange microchannel,the conventional machining or sandblasting process can not achieve the finishing of the inner hole.To solve this problem,the abrasive flow polishing technology is used in this paper to systematically study the influence of abrasive flow polishing process on the dimensional accuracy and surface roughness of micro channel in additive manufacturing.Through finite element analysis,the mechanism of abrasive flow polishing is discussed.Firstly,the formation mechanism of micro channel inner hole surface morphology was studied combined with SLM additive manufacturing process.In the additive manufacturing process,according to whether its own entity can be used as the support of the next layer,the formation mode of the inner pore surface morphology of the micro channel can be divided into two kinds: one is the step effect,the other is "slag hanging".The whole microchannel is divided into three regions,and the theoretical value of the surface roughness of zone I and zone II is analyzed;the formation mode of the inner hole surface morphology in Zone III is "slag hanging",so it is difficult to give a mathematical model,so only the formation reason is studied and analyzed.Then,the influence of polishing time and pressure on the inner surface roughness and inner hole shape accuracy of SLM additive manufacturing microchannel in unidirectional abrasive flow polishing process and the influence of polishing time on the inner surface roughness and inner hole shape accuracy of SLM additive manufacturing microchannel in bidirectional abrasive flow polishing process were studied.The results show that: in the unidirectional abrasive flow polishing process,with the increase of polishing time and polishing pressure,the inner surface roughness of the microchannel presents a gradually decreasing trend,and the inner surface quality of the microchannel gradually improves;the diameter of the minimum circumscribed circle and the maximum inscribed circle of the inner hole of the microchannel presents an increasing trend,and when the polishing time and polishing pressure are greater than a certain value,the inner hole of the microchannel increases The results show that the optimal parameters of abrasive flow polishing are as follows: polishing time is 20 min,polishing pressure is 5 MPa,and good surface quality and shape accuracy can be obtained under this condition.In the two-way abrasive flow polishing process,with the increase of polishing time,the surface roughness value of the micro channel gradually decreases,and the surface quality gradually becomes better;the diameter of the minimum circumscribed circle and the maximum inscribed circle of the micro channel inner hole presents an upward trend,but the shape accuracy of the micro channel inner hole is higher;at the same time,the optimal parameter combination of the two-way abrasive flow polishing process can be obtained as follows: polishing pressure When the polishing force is5 MPa and the polishing time is 5 min,good surface quality and shape accuracy can be obtained.Finally,the ANSYS Fluent finite element analysis software was used to establish relevant models to simulate the polishing process of one-way abrasive flow and two-way abrasive flow.Through numerical simulation,the mechanism of one-way abrasive flow and two-way abrasive flow polishing was discussed.The two polishing non-uniform phenomena caused by pressure drop and centrifugal force in one-way abrasive flow polishing process were explained.The two polishing non-uniform phenomena in two-way abrasive flow polishing process were also explained The reasons for the improvement of non-uniformity and polishing efficiency are discussed.It provides a theoretical and technical basis for the further development of abrasive flow polishing technology.