Types of injection molding side core pulling mechanisms
In the injection molding process, when plastic products contain lateral holes, lateral bosses, or lateral grooves, they must rely on a lateral core pulling mechanism to achieve demolding. The proper selection of a lateral core pulling mechanism has a crucial impact on the molding quality, production efficiency, and mold life of the plastic product. Depending on the power source, injection molding lateral core pulling mechanisms can be mainly divided into three categories: manual lateral core pulling mechanisms, hydraulic (pneumatic) lateral core pulling mechanisms, and mechanical lateral core pulling mechanisms.
Manual side core pulling mechanisms achieve lateral core pulling through manual operation. While their structure is relatively simple and their cost is relatively low, they suffer from low production efficiency and high labor intensity, making them typically suitable for small-batch production or trial production. Manual side core pulling mechanisms can be further categorized as those for threaded cores, those for movable inserts, and those with inclined guide rods. For example, manual core pulling for threaded cores involves unscrewing the threaded core from the part after mold opening using a specialized tool. Manual core pulling for movable inserts involves manually removing the movable insert embedded in the part’s lateral area after mold opening. Manual core pulling with inclined guide rods involves manually turning a handle to move an inclined guide rod, achieving lateral core pulling. While manual side core pulling mechanisms are more cumbersome to operate, their flexibility makes them suitable for the production of complex plastic products that are difficult to automate with automated core pulling.
Hydraulic (pneumatic) side core pulling mechanisms utilize power provided by a hydraulic or pneumatic system to drive the core pulling action. These mechanisms offer significant advantages, including high pulling force, long pulling stroke, smooth operation, and precisely adjustable pulling speed. They can be easily integrated with the injection molding machine’s control system, enabling automated production and significantly improving productivity. They are widely used in the injection molding of large plastic products, or in applications requiring high pulling force and precision. For example, they are often employed in the production of products such as automobile bumpers and large plastic cases. Their operating principle is that a hydraulic pump or air compressor delivers pressurized oil or compressed air to a hydraulic or pneumatic cylinder, pushing a piston, which in turn drives a connected core-pulling slider to complete the core pulling action.
Mechanical side core pulling mechanisms utilize the mold opening force of the injection molding machine, converting it into a lateral core pulling force via a mechanical transmission device to achieve lateral core pulling. There are many different types of mechanical side core pulling mechanisms, including the inclined guide pin side core pulling mechanism, the inclined slider side core pulling mechanism, the bent pin side core pulling mechanism, and the rack and pinion side core pulling mechanism. The inclined guide pin side core pulling mechanism is the most commonly used and primarily consists of an inclined guide pin, a slider, a guide chute, and a wedge block. During the mold opening process, the inclined guide pin drives the slider to move laterally within the guide chute, thereby achieving core pulling. During mold closing, the wedge block compresses the slider to ensure stability during the injection molding process. The inclined slider side core pulling mechanism is suitable for applications with low core pulling force and short core pulling strokes. Its inclined slider not only performs the molding function but also slides laterally along the inclined guide chute during mold opening to achieve core pulling and demolding. The bent pin lateral core pulling mechanism is similar to the inclined guide pin lateral core pulling mechanism, but the bent pin has greater bending resistance and can be used when the core pulling force is high. The rack and pinion lateral core pulling mechanism uses the transmission of the rack and pinion to convert the linear motion of the mold opening into circular or linear motion for core pulling. It is suitable for plastic products that require high core pulling force and special core pulling direction.
Different types of injection molding side core pulling mechanisms each have their own advantages, disadvantages, and applicable scopes. In actual mold design and injection molding production, it is necessary to comprehensively consider multiple factors, such as the structural characteristics of the plastic product, production batch size, cost requirements, and equipment conditions, to rationally select the type of side core pulling mechanism to ensure efficient and high-quality production of plastic products. With the continuous advancement of injection molding technology, various new side core pulling mechanisms are constantly emerging, providing more options for optimizing and innovating the injection molding process. For example, some intelligent side core pulling mechanisms can automatically adjust the core pulling action based on real-time parameters such as pressure and temperature during the injection molding process, further improving the molding quality and production efficiency of plastic products.
