Extruded Plastic Light Fixture Injection Molding Process Steps

First, choose the right plastic raw material, such as impact-resistant polycarbonate (PC). Before use, the raw material must be dried because moisture will affect the performance and molding quality of the plastic. The raw material is generally placed in a drying device and dried at an appropriate temperature (for example, for PC, the drying temperature is about 120°C) and time (usually 3-4 hours) to remove moisture from the raw material.

Install the designed mold on the injection molding machine to ensure that the mold is firmly installed. The design of the mold is crucial to the anti-extrusion performance of the extruded plastic profile. Structures such as reinforcing ribs and wall thickness changes should be set in the mold. After installation, debug and check whether the opening and closing of the mold are smooth and whether the ejection mechanism works properly. At the same time, preheat the mold so that the mold temperature reaches the appropriate range, generally between 40-80°C, which helps the plastic fill the mold cavity better.

Injection volume

According to the size and weight of the lamp, the required plastic injection volume is accurately calculated. This can be controlled by the metering device of the injection molding machine to ensure the accurate amount of plastic injected each time to avoid problems such as lack of material or flash.

 

Injection pressure and speed

The injection pressure is generally between 70-150MPa. For lamp parts with complex structures and thin walls, the injection speed should be appropriately increased to ensure that the plastic can completely fill the mold cavity; but the speed should not be too fast, otherwise cavitation or burning may occur.

At the same time, a multi-stage injection method should be adopted, and different pressures and speeds should be set at different injection stages, such as using higher speeds and pressures at the beginning of filling and reducing speeds at the end of filling to reduce internal stress.

 

Holding pressure and cooling time

The holding pressure stage is important for the density and dimensional accuracy of the lamp. The holding pressure is generally 50% - 80% of the injection pressure, and the holding time depends on the wall thickness and size of the lamp, usually between 5 - 20 seconds. After holding pressure, it enters the cooling stage, and the heat of the plastic is taken away by the cooling system of the mold to solidify the plastic. The cooling time should be long enough to ensure that the lamp is completely formed, generally between 15 - 60 seconds.

Start the injection molding machine, and the plastic raw material is plasticized and molten into a molten state through the rotation and push of the screw through the heated barrel. Then, the screw injects the molten plastic into the mold cavity. During the injection process, closely observe the changes in the pressure, speed and other parameters of the injection molding machine, as well as the filling of the mold. If insufficient filling or other abnormal phenomena are found, adjust the parameters in time.

After the lamp is cooled and formed in the mold, the lamp is ejected from the mold by the ejection mechanism of the mold. After demoulding, the lamp may have some flash or gate residue, which needs to be cleaned. It can be processed by manual trimming or using special trimming equipment. Then, the lamp is inspected for quality, including appearance inspection (to see if there are cracks, deformation, etc.), size inspection (to ensure that it meets the design requirements) and performance testing (such as anti-extrusion test). Qualified lamps can enter the next assembly process.