The injection molding booster clamping unit is an advanced device that uses a boosting mechanism to increase clamping force. It is widely used in the production of large, precision plastic parts, particularly when high clamping force is required but the base tonnage of the injection molding machine is insufficient. Its core principle is to add a booster cylinder or force-increasing mechanism to a conventional clamping unit. This hydraulically or mechanically amplifies the clamping force, increasing the actual clamping force to 1.5-3 times the base tonnage. For example, an injection molding machine with a base clamping force of 1000kN equipped with a booster clamping unit can output a clamping force of 1500-3000kN, meeting the molding requirements of large parts such as automobile bumpers and appliance housings. Compared to traditional clamping units, booster clamping units offer advantages such as a wide adjustable clamping force range, low energy consumption, and fast response speed. They can effectively reduce defects such as flash and dimensional deviation caused by insufficient clamping force, thereby increasing product qualification rates by 20%-30%.
The structure and operating principle of the booster clamping device embody the ingenious design of force amplification. The device primarily consists of a fixed platen, a movable platen, tie rods, a main clamping cylinder, a booster cylinder, and a control system. The main clamping cylinder is responsible for driving the platens to open and close rapidly, achieving mold opening and closing. The booster cylinder, mounted on the movable or rear platen, provides additional pressure during the clamping phase, transmitting force to the platens via a mechanical lever or hydraulic amplification mechanism. Depending on the boosting method, it can be categorized as either hydraulic or mechanical. The hydraulic booster utilizes the difference in area between the large and small pistons within the booster cylinder to amplify pressure, with the amplification factor equal to the piston area ratio (typically 3-5 times). The mechanical booster utilizes the lever mechanism of mechanisms such as toggle levers and wedges to amplify force, achieving a factor of 5-10. The operating process is divided into four phases: rapid clamping (main cylinder operating, low pressure and rapid movement), slow clamping (deceleration upon approaching the mold to prevent impact), booster clamping (boost cylinder operating, providing high clamping force), and mold opening (main cylinder reverses, decompression of the booster cylinder). For example, in the clamping stage of the hydraulic booster device, the booster cylinder increases the system pressure from 16MPa to 40-60MPa. After the area ratio is amplified, the clamping force is significantly improved.
The design parameters of the booster mechanism directly impact the performance of the mold clamping device and require precise calculation to balance force and speed. The piston area ratio of the hydraulic booster cylinder is a key parameter. An excessively large area ratio (exceeding 5:1) shortens the booster cylinder stroke, affecting clamping stability. A low area ratio (less than 2:1) results in ineffective force enhancement. For example, if the system’s maximum operating pressure is 20 MPa and a boost pressure output of 40 MPa is required, the area ratio should be set to 2:1. The toggle length ratio of a mechanical booster is typically 3:1-5:1. The toggle should be made of high-strength alloy structural steel (such as 40CrNiMo) with a hardness of HB280-320 after quenching and tempering to ensure deformation resistance under high loads. The booster response time must be controlled within 0.5-1 second to avoid boost lag, which can cause mold play under injection pressure. Furthermore, the booster stroke must be compatible with the mold thickness, typically 5-15 mm, to fully compensate for elastic deformation. For example, a large mold will produce 2-5mm deformation under the action of clamping force. The boost stroke must at least cover this deformation to ensure tight clamping.
Control systems and safety features ensure the stable operation of a pressurized clamping unit. The control system must utilize a proportional pressure flow valve to achieve stepless adjustment of boost pressure and speed, allowing precise parameter settings based on part characteristics and mold requirements. For example, when producing thick-walled parts, a higher boost pressure (40-50 MPa) and a longer hold time can be set; when producing thin-walled parts, the pressure can be appropriately reduced (30-40 MPa) to shorten the boost time. The system must include pressure feedback, using a pressure sensor to monitor clamping force in real time. Automatically trigger an alarm and adjust the system if the actual value deviates from the set value by more than 5%. Safety features include overload protection, travel limits, and an emergency stop button. The overload protection automatically relieves pressure when the clamping force exceeds 10% of the maximum value, preventing equipment damage. The travel limiter ensures that mold plate movement does not exceed a safe range. The emergency stop button shuts off power in an emergency, ensuring personal safety. For example, a company’s pressurized unit, utilizing an intelligent control system, manages clamping force fluctuations to within ±3%, significantly improving part dimensional stability.
The installation, commissioning, and maintenance of the pressurized mold clamping unit must comply with professional standards. During installation, ensure that all four tie rods are evenly loaded and that the parallelism error does not exceed 0.1mm/m. Failure to do so will result in uneven mold loading, affecting the pressurization effect. During commissioning, the clamping effect should be gradually tested at different pressurization pressures. Test molds should be used to observe defects such as flashing and deformation in the plastic parts to determine the optimal parameters. For example, if the initial pressurization pressure is set to 30MPa, if flashing occurs on the plastic parts, increase it to 35-40MPa. If deformation occurs, reduce the pressure and check the parallelism. During routine maintenance, regularly inspect the seals on the pressurization cylinder and replace them every 5,000 molds to prevent oil leaks. Clean the hydraulic oil filter and replace the hydraulic oil every 1,000 hours to prevent impurities from entering the pressurization mechanism. Grease the toggle joints of the mechanical pressurization unit weekly to reduce friction and wear. Through scientific maintenance, the service life of the booster clamping device can reach 8-10 years, and the failure downtime rate is controlled below 2%, providing stable guarantee for the production of high-demand plastic parts.
