The Research On Conformal Cooling Die Formed By Selective Laser Melting

The cooling system of die is the main factor affecting the quality and production efficiency of forming parts.The traditional water cooling system of mechanical processing can’t guarantee uniform cooling,and forming parts are prone to cracks,pore,uneven shrinkage and other defects.Therefore,it is urgent to find new technology or process methods to solve this industry problem.At present,selective laser melting（SLM）metal powder forming technology has been used to print die with complex internal runner structure conformal cooling channels abroad,and the cooling effect has been improved to a certain extent.However,due to the poor surface roughness of the conformal cooling channels in printing process,poor fluidity of cooling water and even turbulence and void effect will occur,resulting in uneven cooling.The desire to use SLM technology to shorten the processing cycle and improve the quality of injection molded parts is difficult to achieve.The solution is to immerse the printed parts into the liquid chamber,and perform nano-coating on the surface of the parts and the internal flow path to improve the smoothness of the internal flow path.However,the cooling effect and stability of the internal flow channel by nano-coating method.Therefore,SLM technology for printing die conformal cooling channels needs further study.In this paper,the HANS M160selective laser melting equipment independently researched and developed by Hans Group was used to test 1.2709 die steel powder.Based on the quality of the formed parts,the internal surface roughness of the conformal cooling was improved.The specific research contents and conclusions are as follows:（1）The standard sample is printed with the pre-basic process parameters,and the deviation between the formed part and the standard sample is measured by ZEISS coordinate measuring instrument.The field mirror of the equipment is compensated according to the deviation to ensure the dimensional accuracy of the formed part.The effect of laser power（P）,scanning speed（）and scanning distance（D）on the quality of forming parts was studied by single factor test method.According to the test results,the optimum technological parameters were analyzed and determined:P=150W,=1150mm/s,D=50μm,powder layer thickness（H）is 30μm,input energy density is86.96%.The hardness of the part is 328HV_0.1,side surface roughness is 17.04um,density is 96.58%.（2）The influence of repeated scanning times and scanning bias on the surface roughness of SLM forming conformal cooling channels was studied by single factor test method.The results show that when P=150W,=1150mm/s,D=0.05mm,H=0.03mm,the number of contour scanning（n）is 1,and the scanning bias（F）is 0 mm,the input energy density is 86.96%.The best result is that the hardness is 367 HV_0.1,the side surface roughness is 5.69 um,and the density is 98.61%.（3）Based on the experimental results of SLM technology,the effects of different inclination angles and diameters on the surface roughness of circular holes were studied by single factor test method.The results show that the surface roughness16.08 um when the forming inclination angle is 35°.When the diameter of the circular hole is larger,the precision of the forming dimension is higher,but the forming quality is worse,and the roughness of the lower surface is obviously greater than that of the upper surface.Similarly,when the diameter of the forming round hole is small,the forming dimension accuracy is lower,and the forming quality is better.However,when forming small holes,the forming quality is poor or even unable to form.The dimensional accuracy and forming quality of longitudinal forming are better than those of transverse forming.Laser 3D printing was carried out on the finished die by synthesizing the optimum process parameters.The die with high precision,high finish and high quality was obtained.