In the injection molding process of PET preform molds, every step is crucial as it directly affects the quality of the final product. With rich experience and professional knowledge, Heyan Mold provides you with the following key precautions for PET preform mold injection molding.
1, Pre treatment of plastic materials
Due to the strong hygroscopicity of PET plastic material, it must be thoroughly dried before processing. The recommended drying temperature is 150 ° C for at least 4 hours, or 170 ° C for 3-4 hours. To ensure complete drying of the material, air injection method can be used for inspection. In addition, the proportion of recycled PET bottle preforms generally does not exceed 25%, and the recycled materials should be thoroughly dried before use.
2, Selection and matching of injection molding machines
When choosing an injection molding machine, special attention should be paid to the match between its injection weight and the total weight of the product. Due to the multi cavity design and heavy weight of PET preform molds, the total weight of the product should be 2/3 of the injection weight to ensure smooth injection molding process.
3, Optimization of Mold and Gate Design
In the design of PET preform molds, Heyan Mold pays special attention to the application of hot runner molds. This design not only improves production efficiency, but also ensures the stability of product quality. At the same time, insulation boards should be installed between the preform mold and the injection molding machine template to withstand high pressure and ensure stable operation of the mold. Exhaust design is also crucial, ensuring sufficient exhaust to avoid local overheating or fragmentation. However, please note that the depth of the exhaust port should generally not exceed 0.03mm to prevent flying edges.
4, Accurate control of melting temperature
Melting temperature is one of the key factors affecting the quality of PET preform molding. The recommended melting temperature range is 270-295 ℃, and for enhanced GF-PET, it can be set to 290-315 ℃. The joint research mold ensures precise control of the melting temperature through an advanced temperature control system, thereby ensuring the quality and performance of the product.
5, Reasonable setting of injection speed
The injection speed is crucial for preventing premature solidification and improving production efficiency. It is recommended to use a faster injection speed for the joint research mold, but too fast may result in excessive shear rate and make the material brittle. Therefore, the injection speed should be set reasonably while ensuring product quality, and it is generally recommended to complete the injection within 4 seconds.
6, Appropriate adjustment of back pressure
The setting of back pressure is of great significance for preventing wear and extending the life of the mold. The joint research mold suggests adjusting the back pressure to the lowest possible level, generally not exceeding 100 bar. In most cases, back pressure is not even necessary.
7, Strict control of detention time
Prolonged detention may lead to a decrease in molecular weight and affect product quality. Therefore, prolonged stays above 300 ° C should be avoided as much as possible. If the machine shutdown time is less than 15 minutes, it is recommended to only perform gas injection operation; When it exceeds 15 minutes, viscosity PE should be used for cleaning, and the barrel temperature should be lowered to PE temperature until it is turned on again.
Following the above key precautions, combined with the professional technology and high-quality service of HeYan Mold, you will be able to easily cope with various challenges of PET preform mold injection molding, and achieve high-quality and high-efficiency production goals.
