Injection liquid filling and pressurized mold clamping device
The injection molding liquid-filled pressurized mold clamping device is a high-efficiency mold clamping mechanism that is widely used in large injection molding machines or molding scenarios that require high clamping force. It takes into account both the clamping speed and the clamping force through the combined action of liquid-filled rapid mold shifting and hydraulic pressurized mold clamping, which can not only shorten the mold opening and closing time, but also meet the needs of high-pressure molding. Compared with the traditional fully hydraulic mold clamping device, the liquid-filled pressurized mold clamping device has the advantages of low energy consumption, fast response, and stable clamping force. It is especially suitable for the production of large automotive parts, home appliance housings and other products, and can effectively reduce the energy consumption cost per unit product. The core of this device lies in the coordinated work of the liquid-filled circuit and the pressurized circuit, which realizes seamless switching between the stages of rapid mold shifting, slow mold clamping, pressurized mold clamping, pressure holding, pressure relief, and rapid mold opening through logical control.
The structure of an injection molding hydraulic pressure-boosting clamping device primarily consists of a movable platen, a fixed platen, tie rods, a clamping cylinder, a charging valve, a pressure-boosting cylinder, and a control system. The clamping cylinder is responsible for driving the movable platen for rapid mold movement. Its large bore and low operating pressure (typically 10-15 MPa) enable rapid platen movement in a short period of time. The pressure-boosting cylinder provides high-pressure clamping force during the final stages of mold closing. Its small piston area and high-pressure oil (30-50 MPa) generate significant clamping force. For example, a 100mm diameter pressure-boosting cylinder can generate approximately 3927 kN of clamping force at 50 MPa. The pressure-boosting valve is a key component connecting the oil tank to the clamping cylinder. When the clamping cylinder moves rapidly, the valve opens, allowing the oil in the oil tank to rapidly replenish the rodless chamber of the cylinder under atmospheric pressure, reducing oil suction resistance. During the pressure-boosting phase, the valve closes, increasing system pressure and achieving high-pressure clamping. The rigid frame composed of tie rods and templates ensures uniform distribution of clamping force and prevents template deformation.
The hydraulic pressure-boosted mold clamping system operates in five stages. Pressure and speed control in each stage directly impacts mold clamping performance. The first stage is rapid mold opening and closing. The control system opens the charging valve, introducing low-pressure oil into the clamping cylinder. The movable platen moves at a relatively high speed (300-500 mm/s). During this period, the charging valve draws a large amount of oil from the reservoir to meet the flow requirements of the cylinder’s rapid movement. The second stage is slow mold closing. When the movable platen approaches the fixed platen (approximately 50-100 mm away), the system switches to low pressure and low speed (50-100 mm/s) to prevent mold damage. The third stage is pressurized mold clamping. The charging valve closes, the booster cylinder begins operating, and system pressure rapidly rises to the set value (30-50 MPa). Pressure is maintained until the required clamping force is reached. The fourth stage is pressure maintenance and part cooling. The clamping force remains stable, ensuring the part cools and sets under high pressure. The fifth stage is pressure relief and mold opening. The booster cylinder is depressurized, the charging valve opens, and the clamping cylinder reverses the flow, allowing the movable platen to quickly open. The entire process is closed-loop controlled through pressure sensors and displacement sensors to ensure accurate switching at each stage.
Optimizing the performance of a hydraulic-charged, pressurized mold clamping device requires consideration of both the hydraulic system and the mechanical structure. For the hydraulic system, the diameter and response speed of the filling valve must be optimally designed. The diameter is typically 50-100mm, ensuring a flow rate of 1000-3000 L/min during rapid mold shifting. The response time should be controlled within 0.1-0.2 seconds to avoid slowing mold shifting due to insufficient filling. The sealing performance of the pressurized cylinder is crucial, and a combined seal (such as polyurethane + polytetrafluoroethylene) should be used to maintain a good seal even under high pressure, with leakage controlled to below 0.1 mL/min. Mechanically, the tie rod preload should be uniform, with heat preload or hydraulic preload methods used to eliminate tie rod play. This ensures that the platen parallelism error during clamping does not exceed 0.1 mm/m. The guide sleeves between the movable platen and the tie rod should be made of a self-lubricating material (such as a copper-based alloy) to reduce friction and enhance smooth mold shifting. In addition, proportional pressure valves and proportional flow valves can be used to achieve stepless adjustment of pressure and speed to meet the molding requirements of different products.
The application and maintenance of a hydraulic-charged clamping device require careful consideration of several key points. In terms of application, a hydraulic-charged clamping device is particularly advantageous for large injection molding machines requiring clamping forces exceeding 10,000 kN, or for molding engineering plastics with poor flowability and prone to flashing (such as PC and POM). It ensures stable clamping force even under high pressure. During routine maintenance, the cleanliness of the filling valve should be regularly checked to prevent clogging and poor filling. The piston rod of the booster cylinder should be regularly coated with anti-rust oil to prevent corrosion that affects sealing performance. The threaded connections of the tie rods should be regularly inspected to prevent loosening due to vibration. Regarding troubleshooting, insufficient clamping force may indicate a leak in the booster cylinder or a faulty pressure sensor, requiring seal replacement or sensor calibration. A decrease in rapid mold transfer speed should prompt the checking of the filling valve for blockage and the oil level in the tank. With proper application and maintenance, the hydraulic-charged clamping device can achieve a service life of over 10 years, providing a reliable guarantee for efficient injection molding production.
