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Several practical TPE/TPR injection molding process know-how(Raw material: SEBS)

Tiid: 2022-01-26 Hits: 104

● If the surface of the product is strictly required, it must be dried before injection molding. Generally, it is hopper drying at 70~80℃/2h or tray drying at 80~100℃/1h. For tray drying, it should be noted that the thickness of the material layer is generally not more than 50mm. Pallet drying is recommended. If there are bubbles on the surface of the injection-molded strip, or if the strip is cut, and voids are found in it, or if the surface of the product is found to have scattered silver threads, it can be determined that the TPE/TPR raw material contains too much water.

● Second, try to use low temperature injection molding. On the premise of ensuring the quality of plasticization, the extrusion temperature should be reduced as much as possible, and the melt viscosity should be reduced by increasing the injection pressure and screw speed to achieve the purpose of improving fluidity. When the surface of the strip injected from the nozzle is smooth and shiny, it can be determined that the plasticization quality is good. If the sliver injected from the nozzle is very bright, you can be sure that the barrel temperature can still be lowered. The use of low temperature injection molding as much as possible can reduce the cooling time, thereby improving the customer's production efficiency.

● Upper parabola temperature setting. The temperature in the middle area of the screw is the highest, the feeding section is slightly lower, and the nozzle is slightly lower. Typical temperature settings are 150~170°C (feed), 170~180°C (middle), 190~200°C (front), 180°C (nozzle). This temperature setting is only for reference data, and the specific temperature can be adjusted appropriately according to the specific physical properties of different TPE and TPR materials. If it is found that the content of the product is bulging (the gas is contained in it), and the gate is easy to break during demolding, you can refer to the second trick for adjustment.

● Fourth, the holding pressure should be as small as possible. Generally, the holding pressure is smaller than the injection pressure. The holding time can be determined by weighing the product, and the weight of the product will no longer increase, or the shrink mark accepted by the customer shall prevail. If it is found that the gate is easy to break during demolding, and the second trick cannot be used, it should be feasible to reduce the holding pressure.

● If it is several levels of injection, the speed is from slow to fast. Because of this, the gas inside the mold is easily discharged. If there is gas inside the product (internal bulge), or there are dents, the second trick is ineffective, and this method can be used to adjust.