The Deflection and Heat Transfer Analysis of Injection Mold Cavity with SLA Cooling Channel Insert
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Fast cooling in injection molding is the critical in the process economy. Among many different cooling channel designs available, conformal cooling offers the best and the most efficient cooling. However, limited awareness, accessibility, complexity, cost, knowledge, and experience limit the use of conformal cooling channels to be used into the mold in a molding process. Typically, SLM(Selective Laser Melting) method is used to create cavity inserts with conformal cooling channels, however, due to the difficulties listed above, applications of conformal cooling channels are very limited. For an inexpensive alternative SLA (Stereolithography Apparatus) can print cavity inserts with conformal cooling channels. However, due to the material properties, use of SLA printing is very limited. To overcome this limitation, hybrid design of metal cavity inserts with SLA cooling channels has proposed. In order to validate proposed design can withstand harsh injection molding conditions, the Deflection and Heat Transfer Analysis of Injection Mold Cavity with Stereolithography (SLA) Cooling Channel are studied. A cup-like cavity geometry was created using SOLIDWORKS and Autodesk Adviser was used for a flow analysis. The cavity insert design was modified to accommodate an SLA conformal cooling channels inserts made from Formlabs SLA 3D printer. P20 tool steel and a FormLabs resin type Grey Pro V1 were selected for this experiment. ABAQUS was used for numerical analysis to estimate compressive/bending forces and compared with simple calculation using formulae. Cavity deformation at different injection pressure were calculated to determine workable injection pressure ranges for the selected core thickness that is structurally viable for injection molding conditions. The deflection and stress of core thickness of three selected samples, 5, 7.5, and 10mm, were measured and compared to 456MPa of the P20 tool steel fatigue strength. 5mm core thickness failed and is not viable, 7.5mm and 10mm were able to accommodate a wide range of injection pressures of 50MPa and 90MPa. Finally, the thermal efficiency was measured by a simple heat gain and heat loss experiment. The hot water was passed to the mold inlet, placed in ice-laden water, and routed back to the hot water reservoir. The temperature difference between the mold inlet and outlet was evaluated and measured using an infrared temperature reader. Taguchi L12 orthogonal array was used for design of experiment (DOE). The diameter, the pitch of the cooling channels, and the core thickness are the factors. At the same time, the flow rates (laminar, transitional, and turbulent flow) and temperatures are varied (60, 70, and 80℃) to carry out the thermal analysis in the experiment setup. It showed that the lower the flow rate, the lower the cooling diameter, and the lower pitch, the better and the higher the thermal efficiency of the mold because it gave more time for coolant flow and lengthy surface contact engagement. The Deflection and Heat Transfer Analysis of Injection Mold Cavity with Stereolithography (SLA) Cooling Channel Insert was able to justify a simple use of easily available SLA to generate conformal cooling for molding conditions and specify workable conditions adoptable for further usage