Injection molding inclined slider side core pulling mechanism
The lateral core-pulling mechanism for injection molding, featuring an inclined slider, combines the features of an inclined top and a slider. It is suitable for use in plastic parts with internal or external undercuts (such as oblique side holes and inclined bosses). It achieves this by utilizing the oblique motion of the slider. This mechanism offers advantages such as compact structure, high core-pulling accuracy, and reliable operation, making it widely used in the production of precision plastic parts and those with complex structures. The mechanism primarily consists of an inclined slider, guide slot, inclined guide post, push plate, and return spring. The coordinated operation of these components ensures a smooth core-pulling process.
The inclined slider is the core component of the lateral core-pulling mechanism. Its shape matches the inclined undercut of the plastic part and directly participates in the part’s molding and core-pulling process. The slider is typically constructed of alloy tool steel (such as Cr12MoV or S136), hardened to HRC50-55 after quenching to ensure sufficient strength, wear resistance, and polishability. The slider’s forming surface must perfectly align with the part’s inclined undercut, requiring high machining precision, with a surface roughness Ra below 0.8μm to avoid machining marks on the part. A guide boss is typically located at the bottom of the slider, which mates with a guide groove to ensure the slider’s movement along the predetermined oblique trajectory. The clearance between the guide boss and the guide groove is typically 0.01-0.03mm, with a mating accuracy of H7/h6 to ensure smooth and accurate movement.
The guide chute and guide post are key components for guiding the movement of the inclined slider. Their design precision directly impacts the performance of the core-pulling mechanism. The guide chute is typically located on either the movable or fixed platen. Its angle matches the angle of the undercut of the plastic part, typically ranging from 10° to 30°. The guide chute features a T-shaped or dovetail cross-section, matching the guide boss of the inclined slider and capable of withstanding the lateral forces generated by the slider during core pulling. The guide post is fixed to the fixed platen, with the same angle as the guide chute. It passes through the guide hole in the inclined slider. During mold opening, the guide post and guide hole cooperate to drive the slider along the guide chute, achieving core pulling. The diameter of the guide post is determined based on the core-pulling force, typically ranging from 10-20mm. The clearance between the guide post and the guide hole is 0.02-0.05mm, ensuring that the guide post can flexibly drive the slider while avoiding excessive clearance that could cause the slider to wobble.
The working process of the inclined slider’s lateral core-pulling mechanism can be divided into four stages: mold closing, injection molding, mold opening and core pulling, and reset. During the mold closing stage, the inclined slider is reset under the action of the inclined guide pin and reset spring. Its molding surface fits tightly with the mold cavity, together forming the molding space of the plastic part. During the injection molding stage, the melt fills the mold cavity and cools and solidifies. The inclined slider remains stationary to ensure the shape and dimensional accuracy of the plastic part. During the mold opening and core pulling stage, the mold begins to open, and the fixed plate drives the inclined guide pin backward. The inclined guide pin cooperates with the guide hole of the inclined slider to push the inclined slider to move diagonally along the guide groove, gradually disengaging from the inclined undercut part of the plastic part, completing the core pulling. During the reset stage, when the mold is closed, the inclined guide pin is re-inserted into the guide hole of the inclined slider, pushing the inclined slider to move in the opposite direction along the guide groove, returning to the initial position, and preparing for the next injection molding. Throughout the entire working process, the movement of the inclined slider must be smooth and smooth, and the core pulling and reset actions must be accurate and in place to avoid interference with other mold parts.
The design of a lateral core-pulling mechanism with an inclined slider requires consideration of multiple factors to ensure reliable operation and excellent performance. First, the core-pulling distance and motion trajectory of the inclined slider must be determined based on the size and angle of the plastic part’s tilted undercut. The core-pulling distance should be greater than the height of the undercut to ensure that the plastic part can completely detach from the inclined slider. Second, the size and shape of the inclined slider must be rationally designed to reduce its weight, reduce motion inertia, and improve the mechanism’s response speed. Third, a reliable locking device must be provided to lock the inclined slider during mold closing and injection molding to prevent injection pressure from causing the slider to shift. The locking device typically uses a wedge block with a locking angle 2°-3° greater than the tilt angle of the inclined guide post to ensure reliable locking. Finally, the lubrication and cooling of the mechanism must be considered. Grease should be applied to the mating surfaces of the guide groove and the inclined guide post to reduce friction and wear. For large inclined sliders, cooling water circuits can be provided to reduce their operating temperature and prevent thermal expansion from affecting motion accuracy. By comprehensively considering the above factors, a high-performance lateral core-pulling mechanism with an inclined slider can be designed to meet the core-pulling requirements of complex plastic parts.
