With the continuous development of the economy and the continuous progress of the society, it has provided a wealth of material consumer goods, creating good conditions for improving people’s living standards and pursuing a personalized life, thereby accelerating the demand for material consumer goods, and TPU products are one of them, so what should be paid attention to in the TPU injection molding process? Next, we will introduce it in detail.
1. The injection speed and the position of pressure conversion should be set accurately. Inaccurate position setting will increase the difficulty of cause analysis, which is not conducive to rapid and accurate process adjustment.
2. When the moisture content of TPU exceeds 0.2%, it will not only affect the appearance of the product, but also the mechanical properties will be obviously deteriorated, and the injection-molded product will have poor elasticity and low strength. Therefore, it should be dried at a temperature of 80°C to 110°C for 2 to 3 hours before injection molding.
3. The control of processing temperature has a crucial influence on the final size, shape and deformation of the product. The processing temperature depends on the grade of TPU and the specific conditions of mold design. The general trend is that to obtain a small shrinkage, it is necessary to increase the processing temperature.
4. Slow and long-time holding pressure will lead to molecular orientation. Although it is possible to obtain a smaller product size, the product deformation is large, and the difference between transverse and longitudinal shrinkage is large. Large holding pressure will also cause the colloid to be over-compressed in the mold, and the size of the product after demolding is larger than the size of the mold cavity.
5. The choice of injection molding machine model should be appropriate. Small-sized injection molding products should be selected as small injection molding machines as possible, so as to increase the injection stroke, facilitate position control, and reasonably convert injection speed and pressure.
6. The barrel of the injection molding machine should be cleaned, and the mixing of very few other raw materials will reduce the mechanical strength of the product. The barrels cleaned with ABS, PMMA and PE should be cleaned again with TPU nozzle material before injection to remove the residual materials in the barrel. When cleaning the hopper, special attention should be paid to the cleaning of a small amount of raw materials with other properties in the connection part between the hopper and the base of the injection molding machine. This part is easily overlooked by most technical workers in production.
Post time: Jul-13-2022