Research On Surface Properties Of Conformal Cooling Channel In Injection Mold Co-Manufactured By Laser Additive-Electrochemical Polishing

With the increasing demand for plastic products in the market,injection mold with conformal cooling channel,which is characterized by tight structure,high thermal control efficiency and uniform cooling,is widely used in daily necessities,automobile,aerospace and other fields.The emergence of Selective Laser Melting（SLM）technology provides a new manufacturing process for the injection mold of the following cooling channel.However,due to the unique forming mechanism of SLM,the surface quality of its formed parts is poor,which seriously affects the fluid flow in the channel.In order to further improve the surface integrity of the conformal cooling channel,the injection mold of the conformal cooling channel is manufactured by"laser additive-electrolytic polishing".Through the experimental study of SLM process"precision"and electrolytic polishing process"precision",the relationship between"laser additive-electrolytic polishing"collaborative manufacturing process parameters and surface integrity characterization parameters is explored.（1）Based on the SLM forming mechanism,the influence of different process parameters on the morphology of molten pool was investigated by single factor test,when the line laser energy density was between 0.21～0.38 J/mm and the scanning spacing was between 100～120μm range,the forming quality of single layer molten channels is better.The influence of laser power,hatching space,scanning speed and scanning strategy on the surface roughness Sa and densification of SLMed specimens were analyzed by response surface methodology.The optimal process parameters are determined as follows:laser power is 190 W,scanning speed is 690 mm/s,hatching spaceis 105μm and Strip scanning strategy,the surface roughness Sa value is 9.430μm.The density is 99.189%.（2）Based on the mechanism of SLM forming the horizontal channel,the inner surface of the horizontal channel is taken as the research object,and the channel is partitioned.To explore the influence factors and formation mechanism of the surface quality of the step zone and the overhang zone,the contour remelting strategy is adopted to improve the surface adhesion phenomenon of the step zone and the strategy of reducing the surface laser energy density is adoptedto deminish the slag defect in the overhang zone.The optimal combination of process parameters:the step area laser power is 80W,scanning speed is 700 mm/s and contour offset is 60μm.The overhang zone laser power is 100 W,the scanning speed is 1000 mm/s and the hatching space is 50μm.The surface quality of the inner wall of the channel was significantly improved.（3）Based on electrolytic polishing process,surface polishing of SLMedchannel specimen was carried out.The content ratio of sodium chloride to ethylene glycol was 45 g/L,and the content of triethanolamine was 180 ml/L as the polishing base solution.The optimal electrolytic process parameter combination was determined by orthogonal analysis method and single factor test method:Current density 0.55 A/cm²,polishing temperature 40℃,polishing time 10 min,replacement times3.The surface roughness Sa value of the specimen is 0.436μm,and its surface integrity is better.（4）By comparing the surface performance of the injection mold for the"laser additive-electrolytic polishing"collaborative manufacturing of the conformal cooling channel,the results showed that the surface morphology of the cooling channel after electrolytic polishing is significantly improved with green,environmentally friendly and safe salt-alcohol base solution,and the surface roughness Sa varies from 8.445μm reduced to 0.485μm,corresponding to 94.26%reduction;The surface residual stress decreased to 108.19 Mpa,with a reduction of 62.32%;The corrosion current of cooling channel is lower(1.148×10^-7 A/cm²).and the average contact angle is increased by 43.1°.The collaborative preparation process greatly improves the Causative performance of the injection mold for the random cooling channel.