Plastics Technology

JUL 2018

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1500 BTU/hr/20.6 in.² = 72.8 BTU/hr/in.² This Energy Density value would result in a ΔT/in. value of about 0.18 °F/in. Figures 1, 2, and 3 are based on data generated with a coolant flow rate of 1 GPM and coolant temperature of 75 F. We expanded the studies using new data from our core simulator and standard mold base. The studies were conducted at four different heat inputs and four different coolant flow rates. These results are presented in Fig. 4. We believe the Energy Density vs. ΔT/in. relationship is an important step forward in the pursuit of a science-based approach to cooling-circuit design. It would be interesting to conduct similar studies at elevated coolant tempera- tures, but it is our belief that the Energy Density vs. ΔT/ in. relationship wouldn't change much. Even if the mold and coolant are hotter, heat must still be removed to cool the part. With a substantially hotter mold, more heat will be transferred to the environment by conduction to platens, natural convec- tion, and radiation, perhaps skewing the ΔT/in. value a little lower than the graph would predict. Energy Density also influences mold temperature and is useful in predicting that temperature. In our experiments, mold temperatures responded linearly to Energy Density, but the mold geometry makes a difference in the temperature response. Figures 5 and 6 illustrate this difference and clearly show the importance of managing Energy Density in the design process. In other words, one should design a cooling circuit with adequate area to achieve an Energy Density value that produces the desired mold temperature. We must caution that these studies have been conducted with limited mold geometries. Based on what we have studied we believe the Energy Density vs. ΔT/in. relationship probably applies to a Based on what we have studied, we believe the Energy Density vs. ΔT/ in. relationship probably applies to a broader range of mold geometries. FIG 5 Energy Density vs. Steel Temperature, °F (Round Core with Baffle and DME Square Mold; 75 F Coolant) FIG 6 Energy Density vs. Steel Temperature, °F (DME Square Mold; 75 F Coolant) FIG 7 Energy Density vs. Steel Temperature, °F (Round Core with Baffle; 75 F Coolant) Energy Density also influences mold temperature and is useful in predicting that temperature. In our experiments mold temperatures responded linearly to Energy Density, but the mold geometry makes a difference in the temperature response. 180 170 160 150 140 130 120 110 100 90 80 125 120 115 110 105 100 90 85 80 180 170 160 150 140 130 120 110 100 90 80 Steel Temperature, F Steel Temperature, F Steel Temperature, F Energy Density, BTU/hr/in. 2 Energy Density, BTU/hr/in. 2 Energy Density, BTU/hr/in. 2 0 50 100 150 200 250 300 0 5 10 15 20 25 30 35 40 0 50 100 150 200 250 300 Square Mold, 0.38 GPM Square Mold, 0.71 GPM Square Mold, 1 GPM Square Mold, 1.38 GPM Round Core, 0.39 GPM Round Core, 0.71 GPM Round Core, 1 GPM Round Core, 1.36 GPM Like Fig. 5, this demonstrates the importance of designing a cooling circuit with adequate area to achieve an Energy Density value that produces the desired mold temperature. Square Mold, 0.38 GPM Square Mold, 0.71 GPM Square Mold, 1 GPM Square Mold, 1.38 GPM Round Core, 0.39 GPM Round Core, 0.71 GPM Round Core, 1 GPM Round Core, 1.36 GPM Cooling a core can be a challenge due to a smaller cooling circuit area. For example, our 1.5-in diam. round core simulator with a 7/16 diam.cooling circuit has an effective cooling area of only about 8 in.2. This results in high energy density values and greater difficulty controlling core temperature. This shows measured steel temperatures based on four values of heat input and four different coolant flow rates. 46 JULY 2 Plastics Technology PTonline.com T ips & Technique s

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