Wedge rod-triangular slider type first reset mechanism
The wedge-shaped rod-triangular slider pre-reset mechanism is a key device in injection molds used to prevent interference between the side core pulling mechanism and demolding elements such as the push rod. It drives the triangular slider through the inclined surface of the wedge-shaped rod, causing the push rod to reset in advance, ensuring that the push rod is completely retracted into the cavity before the side core pulling mechanism resets during the mold closing process, thereby avoiding damage from collision between the two. Compared with traditional spring-type or hydraulic pre-reset mechanisms, this mechanism has the advantages of reliable reset, compact structure, and no need for additional power source. It is particularly suitable for molds with limited space and high reset accuracy requirements. For example, when producing household appliance plastic parts with side holes and complex ejection structures, the wedge-shaped rod-triangular slider pre-reset mechanism can ensure that the push rod is reset 0.5-1mm before the side core pulling resets, completely eliminating the risk of interference and reducing the mold failure rate by more than 60%.
The composition and working principle of the wedge-rod-triangular slider pre-reset mechanism are key to understanding its function. The mechanism primarily consists of a wedge-rod, a triangular slider, a push rod mounting plate, a guide slot, and a limiter. The wedge-rod is fixed to the fixed mold side, with its working surface being an inclined plane, typically at an angle of 25°-35°. The triangular slider is mounted within the guide slot of the movable mold and slides horizontally, with one side contacting the wedge-rod’s inclined surface and the other connected to the push rod mounting plate. The guide slot provides precise guidance for the triangular slider’s movement, and the limiter limits the slider’s sliding distance to prevent excessive movement. The working process is as follows: During mold closing, the fixed mold drives the wedge rod downward. The inclined surface of the wedge rod contacts the triangular slider, pushing the slider horizontally along the guide groove. The slider then drives the push rod fixing plate upward, causing the push rod to reset prematurely. When the mold is closed to a certain position and the push rod is fully reset, the triangular slider disengages from the wedge rod, and the side core pulling mechanism begins to reset. After mold closing is complete, the triangular slider returns to its initial position under the action of a spring, awaiting the next cycle. For example, in the production of automotive plastic molds with lateral bosses and multiple ejector pins, the wedge rod drives the triangular slider during mold closing, forcing the ejector pins to fully exit the cavity before the side core pulling resets, avoiding collisions.
The design parameters of the wedge rod and triangular slider directly affect the performance of the pre-reset mechanism and require precise calculation. The wedge rod’s tilt angle α is a key parameter. If the angle is too small, the triangular slider will not move far enough, preventing the push rod from fully resetting. If the angle is too large, the lateral force on the wedge rod will increase, which can easily cause deformation. Generally speaking, the tilt angle should match the tilt angle of the side core pulling mechanism, usually 25°-30°. This ensures sufficient reset travel and reasonable force on the wedge rod. The working length of the wedge rod must be calculated based on the required reset travel. The formula is L=S/tanα, where L is the working length of the wedge rod (mm) and S is the required reset travel of the push rod (mm). The shape of the triangular slider is a right triangle, and the angle of its bevel is the same as the inclination angle of the wedge rod to ensure close contact between the two; the length and width of the slider need to be determined according to the force, generally the length is 30-50mm and the width is 20-40mm. The material is 45 steel, and the hardness reaches HB220-250 after tempering treatment, ensuring sufficient strength and wear resistance.
The installation positioning and matching accuracy of the mechanism are crucial to the reliability of the reset. The wedge rod must be firmly and reliably fixed to the fixed mold, and positioned with screws and pins. The positioning accuracy error should not exceed 0.02mm to ensure accurate contact with the triangular slider when the mold is closed. The triangular slider and the guide groove are matched with H7/g6 clearance, and the matching clearance is controlled at 0.01-0.03mm. The parallelism error of the guide groove does not exceed 0.01mm/m to ensure smooth movement of the slider without jamming. The connection between the triangular slider and the push rod fixing plate should be a movable connection, such as a pin hinge, allowing a small relative movement between the two to avoid jamming due to installation errors. The position of the limit device needs to be precisely adjusted to ensure that the maximum movement distance of the triangular slider just meets the full reset of the push rod, usually 0.5-1mm larger than the required reset stroke to prevent excessive movement. In addition, grease needs to be added to the moving parts of the mechanism to reduce friction and wear and extend service life.
Debugging and troubleshooting common issues with the wedge-rod-triangular slider pre-reset mechanism are crucial to ensuring proper operation. During debugging, first check the contact between the wedge-rod and the triangular slider to ensure there is no misalignment or excessive clearance. The contact area can be checked using a color-coating method, which should be at least 70%. The mold is then manually closed to ensure the push rod resets before the side core-pulling mechanism resets. If reset occurs too early or too late, the wedge-rod mounting height or position of the stopper can be adjusted to correct the situation. Common issues and solutions include: Incomplete push rod reset may indicate insufficient wedge-rod tilt or working length, requiring recalculation and replacement of the wedge-rod. If the triangular slider becomes stuck, check the guideway parallelism and surface roughness and, if necessary, regrind it. Excessive wear of the mechanism requires replacing the triangular slider with a higher-strength material and enhancing lubrication. Through careful design, installation, and debugging, this pre-reset mechanism has achieved trouble-free operation over millions of mold cycles, effectively ensuring mold safety and stable production.
