Preparation work before starting injection molding
Preparatory work before starting the injection molding machine is crucial for ensuring smooth production and product quality. This includes equipment inspection, raw material preparation, mold installation, and other aspects, requiring meticulous attention to detail. First, the operator must conduct a comprehensive inspection of the injection molding machine, including ensuring that the power supply voltage is stable within the rated range (typically 380V ± 10%). Excessive voltage fluctuations may cause abnormal motor operation or control system failure. The hydraulic system’s oil level and temperature must also be checked. The oil level should be maintained between 1/2 and 2/3 of the gauge’s reading. The oil temperature should be no lower than 25°C before starting the machine. If the oil temperature is too low, preheat the machine with a heater to prevent excessive hydraulic oil viscosity from affecting system operation.
Raw material preparation and processing are another critical task before starting the injection molding machine. Operators must verify that the raw material brand and specifications are consistent with the drawings based on the production order requirements to avoid using the wrong materials. Highly hygroscopic raw materials, such as PA, PC, and PBT, require pre-drying. The drying temperature and time vary depending on the type of raw material. For example, the drying temperature for PA66 is generally 120-140°C, and the drying time is 4-6 hours. Ensure that the raw material’s moisture content is below 0.05%. Otherwise, defects such as bubbles and silver streaks are likely to appear in the molded parts. During the drying process, the dryer’s temperature and air volume must be regularly checked to ensure effective drying. Furthermore, the raw materials must be screened to remove impurities and particles to prevent nozzle clogging or screw damage. Raw materials that require the addition of masterbatch or additives must be mixed according to the specified ratio, typically for 10-15 minutes, to ensure a uniform mixture.
The installation and inspection of the mold are essential steps before starting the injection molding machine. Before installing the mold, it is necessary to clean the dust and oil on the mold surface, and check whether the mold cavity and core have defects such as scratches and cracks. If there is any damage, it must be repaired in time. At the same time, check whether the guide pins and guide sleeves of the mold are well lubricated and whether the ejection mechanism is flexible and reliable. When installing the mold, it is necessary to clean the movable platen and fixed platen of the injection molding machine, then align the mold’s positioning ring with the positioning hole of the injection molding machine, slowly close the template, and fix the mold steadily on the template. Then tighten the mold with bolts, paying attention to the uniform tightening force of the bolts to avoid deformation caused by uneven force on the mold. After the mold is installed, it is necessary to manually operate the injection molding machine to check whether the mold opens and closes smoothly and whether the ejection distance is appropriate to ensure that the mold does not get stuck during the production process.
Setting and adjusting process parameters is a crucial prerequisite for ensuring product quality. Operators must initially set injection molding process parameters based on the raw material characteristics, mold structure, and part requirements. These parameters include barrel temperature, nozzle temperature, injection pressure, injection speed, holding pressure, holding time, and cooling time. For example, for PE materials, the barrel temperature is generally set between 180-220°C, while for PC materials, the barrel temperature should be set between 260-320°C. When setting the injection pressure, adjustments should be made based on the complexity of the part and the mold’s runner length, typically between 50-150 MPa. Furthermore, the cooling time should be set based on the part’s thickness, typically between 10-60 seconds. After the settings are complete, a test shot should be conducted to observe the material flow and part molding. Based on the test shot results, the process parameters should be fine-tuned until the desired molding effect is achieved.
Safety checks and environmental cleanup are also essential tasks before starting the injection molding machine. Operators must check that the machine’s safety devices, such as safety doors and emergency stop buttons, are intact and effective, ensuring they provide protection during production. They must also check that the workshop’s ventilation equipment is functioning properly to maintain air circulation and reduce the risk of harmful gases to operators. Furthermore, the work site must be organized, with raw materials and tools neatly arranged and the floor cleared of debris and grease to prevent slips and trips. Before starting the machine, operators must also wear personal protective equipment, such as hard hats, safety glasses, and gloves, to ensure proper personal protection. Only by completing these safety checks and environmental cleanup tasks can a safe and orderly working environment be created for injection molding production.
