Injection molding inclined top, hydraulic inclined slider core pulling
Injection molding inclined ejector and hydraulic inclined slider core pulling are two important core pulling methods used in molds for molded products with undercuts or complex structures. They are widely used in the production of complex products such as automotive parts and home appliance housings. Inclined ejector core pulling relies on the mechanical movement of the mold when it is opened, and the core pulling is achieved through the tilting movement of the inclined ejector rod. It is suitable for occasions with shallow undercut depths and small core pulling forces. Hydraulic inclined slider core pulling uses hydraulic cylinders to provide power to drive the inclined slider to complete the core pulling action. It is suitable for complex structures with large undercut depths and high core pulling force requirements. Both have their advantages. Inclined ejector core pulling has a simple structure and low cost, while hydraulic inclined slider core pulling has the characteristics of large core pulling force, stable movement, and strong controllability. The appropriate core pulling method can be selected according to the structural characteristics of the product.
The inclined ejector core-pulling mechanism primarily consists of an ejector rod, a guide slider, and an ejector plate. Its operation is linked to the mold opening process. When the mold opens, the ejector plate moves upward, driven by the ejector mechanism of the injection molding machine. The ejector rod, constrained by the guide slider, rises vertically and contracts horizontally inward, freeing it from the inner undercut of the part. The tilt angle of the ejector rod is a critical design parameter, typically controlled between 15° and 20°. Excessive angles can easily cause the ejector rod to bend or break due to excessive stress, while smaller angles require a longer ejector rod, increasing the mold height. For example, for a part with an inner undercut depth of 5mm, a 15° ejector angle requires the ejector rod to rise vertically to approximately 19.3mm to complete the core-pulling process. This design should be appropriately determined based on the part dimensions.
The hydraulic inclined-slide core-pulling mechanism consists of a hydraulic cylinder, an inclined slide, guide rails, and position limits. The core-pulling action is independently controlled by the hydraulic system and is not limited by the mold opening stroke. The hydraulic cylinder, via a piston rod, drives the inclined slide along the guide rails to tilt and reposition the core. The pulling force can be controlled by adjusting the hydraulic system pressure, while the core-pulling stroke can be precisely controlled by adjusting the cylinder stroke or position limits. This core-pulling method is suitable for large products or applications requiring long core-pulling strokes. For example, when molding automobile bumpers with deep grooves and undercuts, the hydraulic inclined-slide core-pulling mechanism provides sufficient force and stroke to ensure smooth demolding. Furthermore, the hydraulic system enables delayed core-pulling control, facilitating adjustment of the core-pulling timing based on the cooling conditions of the part and minimizing deformation.
The structural design of the inclined ejector and hydraulic inclined slider core pulling systems must fully consider the demolding safety of the product and the service life of the mold. For inclined ejector core pulling, a wear-resistant plate and a guide sleeve must be installed between the inclined ejector rod and the template to reduce friction and wear during movement. The inclined ejector rod should be made of high-strength alloy tool steel such as Cr12MoV, which reaches a hardness of 50-55HRC after quenching to ensure sufficient strength and wear resistance. For hydraulic inclined slider core pulling, the fitting clearance between the inclined slider and the guide rail must be strictly controlled between 0.02-0.05mm. The guide rail surface must be quenched and ground to improve wear resistance. At the same time, a dustproof device must be installed to prevent plastic debris or oil from entering the fitting surface and affecting the movement accuracy. In addition, both core pulling methods require a limit device to ensure that the core is pulled and reset in place to avoid collision with other parts of the mold.
In practical applications, inclined top and hydraulic inclined slide core pulling can be used in combination to cope with more complex product structures. For example, when molding products with multiple inner undercuts in different directions, inclined top core pulling can be used to handle shallow undercuts, while hydraulic inclined slide core pulling can be used to handle deep undercuts, giving full play to the advantages of both core pulling methods. After the design is completed, the coordination of the core pulling action needs to be verified through 3D modeling and motion simulation to check whether there are any interference or poor movement problems. During the mold trial, it is necessary to pay special attention to whether there are defects such as strain and deformation on the undercut parts of the product. According to the mold trial results, the core pulling speed, stroke or angle and other parameters should be adjusted to ensure that the core pulling mechanism is stable and reliable and meets the requirements of mass production.
