폴리머코어 게이트 크기 변화가 두께 방향 수축률에 미치는 영향에 대한 연구

A study on the effects of polymer core gate sizes on thickness shrinkage rate

In this study, the variation of the shrinkage in the thickness direction of the molded parts according to the gatesize of the polymer core fabricated through the 3D printer using the SLS method was studied. The polymer cores arelaser sintered and the powder material is nylon base PA2200. The polymer cores have lower heat transfer rate and rigiditythan the metal core due to the characteristics of the material. Therefore, the injection molding test conditions are set tominimize the deformation of the core during the injection process. The resin used in the injection molding test is a PPmaterial. The packing condition was set to 80, 90 and 100% of the maximum injection pressure for each gate size. Therunner diameter used was 3mm, and the gates were fabricated in semicircle shapes with cross sections 1, 2, and 3 mm2,respectively. Thickness measurement was performed for 10 points at 2.5 mm intervals from the point 2.5 mm away fromthe gate, and the shrinkage to thickness was measured for each point. The shrinkage rate according to the gate size tendsto decrease as the cross-sectional area decreases as the maximum injection pressure increases. The average thicknessshrinkage rate was close to 0% when the packing pressure was 90% for the gate area of 1mm2. When the holdingpressure was set to 100%, the shrinkage was found to decrease by 3% from the standard dimension due to theover-packing phenomenon. Therefore, the smaller the gate, the more closely the molded dimensions can be molded dueto the high pressure generation. It was confirmed that precise packing process control is necessary because over-packingphenomenon may occur.

In this study, the variation of the shrinkage in the thickness direction of the molded parts according to the gatesize of the polymer core fabricated through the 3D printer using the SLS method was studied. The polymer cores arelaser sintered and the powder material is nylon base PA2200. The polymer cores have lower heat transfer rate and rigiditythan the metal core due to the characteristics of the material. Therefore, the injection molding test conditions are set tominimize the deformation of the core during the injection process. The resin used in the injection molding test is a PPmaterial. The packing condition was set to 80, 90 and 100% of the maximum injection pressure for each gate size. Therunner diameter used was 3mm, and the gates were fabricated in semicircle shapes with cross sections 1, 2, and 3 mm2,respectively. Thickness measurement was performed for 10 points at 2.5 mm intervals from the point 2.5 mm away fromthe gate, and the shrinkage to thickness was measured for each point. The shrinkage rate according to the gate size tendsto decrease as the cross-sectional area decreases as the maximum injection pressure increases. The average thicknessshrinkage rate was close to 0% when the packing pressure was 90% for the gate area of 1mm2. When the holdingpressure was set to 100%, the shrinkage was found to decrease by 3% from the standard dimension due to theover-packing phenomenon. Therefore, the smaller the gate, the more closely the molded dimensions can be molded dueto the high pressure generation. It was confirmed that precise packing process control is necessary because over-packingphenomenon may occur.