The further development of hot runner injection molding equipment and the continuous improvement of product quality requirements have put forward higher requirements for the hot runner injection molding process. Correctly selecting hot runner injection equipment, and reasonably setting the hot runner injection molding process and optimizing process conditions, are key to improving product quality.
The performance of a hot runner injection molding machine directly affects the quality of the injection molded products. Different specifications and performance requirements of injection molding machines vary greatly in price. When selecting the specifications of a hot runner injection molding machine, the first factor to consider is the production status of the hot runner mold, because the same injection molding machine often needs to meet the production requirements of multiple hot runner molds of different sizes. The specifications of the injection molding machine, including the maximum clamping force and maximum injection volume, should be determined based on the weight of the parts and the size of the hot runner molds. Then, choose the appropriate model based on the specifications provided by the injection molding machine manufacturer. Most manufacturers provide customized services, which greatly facilitates the purchase of injection molding machines. Additionally, one should consider whether special configurations are necessary.
Comparing the melting point and allowable residence time of PA66, the temperature of the barrel should be set according to the properties of different plastic materials. The barrel temperature is generally set 10℃-30℃ higher than the plastic melting point. It is important to note that the melting point and allowable residence time in the barrel provided by different manufacturers may vary due to different synthesis methods or the types of additives. When setting the temperature of the hot runner mold, circulating water cooling is generally used. However, in the production of precision-sized parts or products with high surface quality requirements, a mold temperature controller capable of accurate control should be used according to the requirements of the hot runner injection molding process.
The injection time, holding time, and cooling time should be set based on the product thickness, hot runner mold temperature, material properties, etc. The injection time is usually set to be slightly longer than the time required for the screw to complete the injection stroke. Excessively long injection times can cause mechanical wear, increased energy consumption, and extended molding cycles. The holding time should be set based on the product thickness. Thin-walled products may not require holding time during molding. When setting the holding time, ensure that there are no visible dents on the product surface. The best holding time can also be determined by weighing, gradually extending the holding time until the product quality no longer changes. The cooling time should also be determined based on the product thickness, hot runner mold temperature, and material properties. Generally, amorphous polymers require a longer cooling time than crystalline polymers.
The injection pressure should follow the principle of being as low as possible while still providing enough power to achieve the required injection speed and allowing the melt to smoothly fill the cavity. Excessive pressure can induce internal stress in the product. For products requiring high dimensional accuracy, high pressure injection can be used to minimize shrinkage after demolding.
In the hot runner injection molding process, in addition to the main parameters such as molding temperature, pressure, speed, time, and multi-stage injection switching positions, there are many other process parameters, such as back pressure, screw speed, screw retraction, and anti-jetting settings, which should not be overlooked.
When changing parameters, make sure that the computer confirms the input parameters before proceeding to the next parameter change. Avoid changing more than two parameters simultaneously. During stable production, all parameters should be kept as consistent as possible, and detailed records should be kept. If there is a significant change in the parameters, the cause should be promptly investigated. Additionally, the hot runner injection molding process should be standardized each time the mold is put into production to facilitate quality control of the finished products.
English
français
Deutsch
Español
italiano
русский
português
العربية
Türkçe
dansk
Svenska
