Lateral core pulling mechanism of the slider hydraulic cylinder
The lateral core-pulling mechanism of the slider hydraulic cylinder is an efficient solution for achieving lateral forming with large core-pulling distances and high core-pulling forces. Its core consists of a hydraulic cylinder, slider, guide device, and control system. It is suitable for applications with core-pulling distances of 50-300mm and core-pulling forces of 30-200kN, such as lateral holes in automotive door panels and boss forming on large appliance housings. The hydraulic cylinder serves as the power source, rigidly connected to the slider via a piston rod to achieve reciprocating motion. The cylinder’s bore and stroke are calculated based on the core-pulling force and distance. For example, for a core-pulling force of 100kN, an 80mm bore cylinder is selected (approximately 100kN thrust at a working pressure of 20MPa). The stroke should be 10-20mm greater than the core-pulling distance to ensure proper core pulling. There are two installation methods for the cylinder: flange type and trunnion type. The flange type has good rigidity and is suitable for core pulling in a fixed direction. The trunnion type can swing around the axis and is suitable for situations where the core pulling direction needs to be fine-tuned, such as lateral core pulling of complex curved plastic parts. The trunnion type cylinder can compensate for slight angular deviations.
The guidance and positioning design of the slider’s hydraulic cylinder’s lateral core-pulling mechanism must ensure accurate core-pulling. Precision guide rails or T-blocks are typically used. The clearance between the slider and guide rail is 0.03-0.05mm, and the guide rail parallelism error does not exceed 0.02mm/m. This ensures that the slider’s linearity error is ≤0.05mm/100mm. Limit switches and mechanical stop blocks are installed at the slider’s core-pulling and reset endpoints. The limit switches are contactless proximity switches with a repeatability accuracy of ±0.1mm. The mechanical stop blocks are made of hardened 45# steel (HRC40-45), with a contact area of at least 100mm² with the slider to withstand the slider’s inertial impact. For example, for a mechanism with a core-pulling distance of 150mm, a stop block is installed at each end of the slider. The stop block at the core-pulling endpoint is 20mm thick, and the stop block at the reset endpoint is 15mm thick. These two stop blocks, combined with proximity switches, achieve dual positioning, ensuring a slider position accuracy of ±0.1mm. The connection between the oil cylinder and the slider adopts a floating joint, which allows an angular deviation of ±1° and a radial deviation of ±0.5mm to compensate for installation errors and avoid additional bending moment on the oil cylinder piston rod.
The design and commissioning of the hydraulic system are crucial for the stable operation of the slider’s hydraulic cylinder’s lateral core-pulling mechanism. It must include a power source, control elements, and actuators to achieve precise control of pressure, speed, and direction. The system’s operating pressure is typically set between 10 and 25 MPa, adjusted based on the required core-pulling force. For example, for a core-pulling force of 50 kN, the system pressure is adjusted to 15 MPa (approximately 47 kN thrust for a 63 mm cylinder diameter). Proportional pressure and flow valves are used to control the cylinder’s pressure and speed, enabling multi-stage speed regulation during the core-pulling process. For example, a low speed (50 mm/s) is used during the initial core-pulling phase to avoid impact, a high speed (150 mm/s) during the middle phase to improve efficiency, and a low speed (50 mm/s) during the final phase to ensure precise positioning. The system requires a pressure-holding circuit to maintain a certain pressure (approximately 80% of the operating pressure) after the core is pulled into position to prevent the slider from retreating under the influence of injection pressure. The pressure-holding period is synchronized with the injection cycle. The cleanliness of the hydraulic oil must reach NAS level 8 or above and be filtered through a precision filter (filtration accuracy 3μm) to avoid valve sticking caused by oil contamination. The oil tank must be installed with an oil temperature controller to control the oil temperature at 30-50℃ to ensure stable oil viscosity.
Safety protection is essential for the slide’s hydraulic cylinder’s lateral core-pulling mechanism. This prevents malfunctioning of the slide due to hydraulic system failures, ensuring mold and equipment safety. Bidirectional hydraulic locks are installed on the cylinder’s oil supply and return lines to ensure the slide remains in its current position in the event of a power outage or pressure loss, preventing movement due to weight or external forces. For example, in vertical core-pulling mechanisms, the hydraulic lock prevents the slide from falling. Pressure and position sensors are installed in the system to monitor the cylinder’s operating pressure and slide position in real time. If the pressure exceeds 10% of the set value or the position deviates by more than 0.5mm, an alarm is issued and the mold is stopped. Mechanical bumpers, made of high-strength alloy steel (such as quenched 40Cr) and at least 20mm thick, are installed in the area where the slide interferes with other mold components. These bumpers prevent the slide from overtravel, preventing direct collision. For example, a bumper is installed on the side of the slide closest to the ejector pin, with a minimum distance of 5mm. This ensures that even if the slide deviates, it will first contact the bumper, protecting the ejector pin from damage.
Maintenance and commissioning of the slider hydraulic cylinder’s lateral core-pulling mechanism must follow standardized procedures to ensure long-term stable operation. Regularly check the hydraulic oil level and quality, and replace the hydraulic oil every 500 hours of operation. Clean the oil tank and filter to prevent oil aging and contamination. Check the cylinder seals for wear and inspect the piston rod seal every 1000 mold cycles. If leaks are detected, replace the seal (such as a polyurethane U-ring) promptly to ensure a reliable seal. During commissioning, manually operate the cylinder to confirm smooth slider movement without binding. Then, perform a no-load mold trial to test the positioning accuracy of the core pulling and reset. Once normal no-load operation is established, perform a live mold trial, and gradually adjust the pressure and speed parameters until the core pulling effect meets the requirements. For example, in the hydraulic core-pulling mechanism of a certain automobile bumper mold, by increasing the core pulling speed from 100 mm/s to 150 mm/s and the holding pressure from 12 MPa to 15 MPa, the problem of flashing on the plastic part after core pulling was resolved, increasing production efficiency by 20%. Through scientific maintenance and debugging, the average trouble-free operation time of the mechanism can reach more than 10,000 modules.
