The Deflection and Heat Transfer Analysis of Injection Mold Cavity with SLA Cooling Channel Insert

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 for the metal and plastic respectively. Simple calculation was used to estimate compressive and deflection at different injection pressures 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 calculated 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 27MPa and 45MPa estimated using Autodesk Advisor. Finally, the temperature differences of coolant were 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 measured using an infrared temperature reader. Taguchi L12 orthogonal array was used for design of experiment (DOE). Two levels of diameter, the pitch of the cooling channels, and the core thickness were used. 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 higher 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 accounted for the largest heat removal rate about 1.59KJ. It confirmed the higher the flow rate, the higher the heat removal. The higher the core thickness, the lesser the heat removal. The maximum heat removal of 1.59KJ is recorded with 7.5mm core thickness, 8mm cooling diameter and 12mm pitch. The Deflection and Heat Transfer Analysis of Injection Mold Cavity with Stereolithography (SLA) Cooling Channel Insert justified a simple use of easily available SLA to generate conformal cooling for molding conditions and specify workable conditions adoptable for further usage. The cost is relatively cheap compared to a SLM produced part. There is a significant cost reduction up to four times when a hybrid design is adopted