Views: 0 Author: Site Editor Publish Time: 2022-09-14 Origin: Site
Medical mold mainly consists of casting system, temperature control system, molded parts and structural parts. Among them, the sprue system and the molded parts are the parts that are in direct contact with the plastic and change with the plastic and the product. They are the most complex and changeable parts in the mold and require the highest quality of workmanship and precision.
How to control the temperature of medical mold?
How to control the injection pressure when using medical mold?
How to control the injection time when using medical mold?
The temperature that must be controlled while using medical mold includes cylinder temperature, nozzle temperature and mold temperature. The first two temperatures mainly affect the plasticization and flow of plastics, while the latter temperature mainly affects the flow and cooling of plastics. Each plastic has a different flow temperature. For the same plastic, its flow temperature and decomposition temperature are different due to different sources or qualities. This is due to the difference in average molecular weight and molecular weight distribution. Also the plasticizing process in the machine is different, so the choice of cylinder temperature is also different.
When using the medical mold, the injection pressure is provided by the hydraulic system of the injection molding system. The pressure of the hydraulic cylinder is transferred to the plastic melt via the screw of the injection molding machine. Under the pressure of the plastic melt, it enters the vertical flow channel of the mold through the nozzle of the injection molding machine (in some molds also the main flow channel), the main flow channel and the secondary circuit. The process is called injection molding or filling process. The presence of pressure should overcome the resistance in the melt flow process, or vice versa, the resistance in the flow process must be balanced by the pressure of the injection molding machine to ensure a smooth flow of the filling process.
The injection time for the medical mold mentioned here refers to the time that the plastic melt needs to fill the cavity, without idle times such as opening and closing the mold. Although the injection time is very short and has little influence on the mold cycle, the adjustment of the injection time has a great influence on the pressure control of bleed, sprue and cavity. Appropriate injection time helps to fill the melt optimally and is of great importance for improving the surface quality of the product and reducing dimensional tolerances.
The injection molding time of medical mold is much shorter than the cooling time, which is about 1/10 to 1/15 of the cooling time. This rule can be used as a basis for predicting the total mold time of plastic parts. In mold flow analysis, the injection time in the analysis result is equal to the injection time set in the process conditions only if the melt is completely driven by the screw to fill the cavity. If the screw retaining pressure switch is made before the cavity is filled, the analysis result is greater than the setting of the process conditions.
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