Injection pressure-stabilizing mold clamping device
The injection molding pressure-stabilizing clamping device is a core component of the injection molding machine. Its main function is to provide stable clamping force during the injection process, ensuring that the mold is tightly closed and preventing the plastic melt from overflowing from the parting surface. At the same time, it drives the mold to open smoothly and reliably during mold opening, allowing the product to be smoothly demolded. Compared with traditional mechanical or ordinary hydraulic clamping devices, the pressure-stabilizing clamping device monitors changes in the clamping force in real time through a closed-loop control system and dynamically adjusts it through the hydraulic system to ensure that the clamping force always remains within the set range, effectively avoiding problems such as product flash, material shortages, or mold damage caused by fluctuations in clamping force. For example, when molding large, thin-walled products, the pressure-stabilizing clamping device can accurately control the clamping force to prevent flash due to insufficient clamping force or mold deformation due to excessive clamping force.
The hydraulic system design of a pressure-stabilized clamping device is key to achieving this pressure-stabilizing function. The system primarily consists of a variable displacement pump, a proportional pressure valve, a servo valve, a hydraulic cylinder, and a pressure sensor. The pressure sensor collects the clamping force signal in real time and transmits it to the control system. Based on the deviation between the set value and the actual value, the control system adjusts the flow and pressure of the hydraulic oil entering the clamping cylinder via a proportional pressure valve or servo valve to achieve dynamic stabilization of the clamping force. For example, when the mold undergoes slight dimensional changes due to temperature fluctuations, the pressure sensor detects the clamping force fluctuations, and the control system immediately adjusts the hydraulic oil pressure to restore the clamping force to the set value. The hydraulic system’s fluid must be kept clean, and the filter and hydraulic oil must be replaced regularly to prevent impurities from clogging the valve block or wearing out the hydraulic cylinder seals, potentially affecting the system’s response speed and control accuracy.
The mechanical structure design of the mold clamping device must match the hydraulic system to ensure uniform transmission of the clamping force. The mechanical structure mainly includes a movable mold plate, a fixed mold plate, a pull rod, an elbow mechanism or a direct pressure hydraulic cylinder, etc. The pull rods must be evenly distributed around the mold plate to ensure that the clamping force is evenly distributed on the mold plate to avoid deformation of the mold plate due to uneven force. For the elbow-type pressure-stabilizing mold clamping device, the hinge point of the elbow must be precisely machined and heat-treated to improve its wear resistance and load-bearing capacity, ensuring that there will be no excessive gap or breakage during repeated movement. The direct pressure-stabilizing mold clamping device directly drives the movable mold plate to move through a hydraulic cylinder. It has a simple structure and fast response speed, and is suitable for occasions where high precision control of the clamping force is required. The material of the mold plate must be made of high-strength cast iron or steel plate welded structure, and aging treatment must be performed to eliminate internal stress to ensure that the mold plate is dimensionalally stable and does not deform during long-term use.
The control system for a pressure-stabilized clamping unit requires high precision and rapid response. It typically utilizes a PLC or industrial computer as the core control system, equipped with a touchscreen human-machine interface (HMI) that allows the operator to easily set parameters such as clamping force, mold opening speed, and clamping position, while also displaying the system’s operating status and fault information in real time. The control algorithm must be optimized, employing advanced algorithms such as PID control or fuzzy control to enhance the system’s dynamic response speed and interference resistance, ensuring that clamping force remains stable despite changes in the injection molding machine’s load or external interference. For example, when a pressure surge generated during the injection phase of the injection molding machine is transmitted to the clamping unit, the control system must react within milliseconds, adjusting the hydraulic system pressure to offset the resulting clamping force fluctuations. Furthermore, the control system must include fault self-diagnosis capabilities. If problems such as pressure sensor failure or hydraulic system leaks are detected, an alarm signal will be issued immediately, halting the machine to prevent further damage.
The performance parameters of the pressure-stabilized mold clamping device need to be reasonably selected according to the characteristics of the injection molded product. The main parameters include the maximum clamping force, tie rod spacing, maximum mold opening stroke, template size, etc. The maximum clamping force needs to be calculated and determined based on the projected area of the product and the molding pressure of the plastic. It is usually 1.2-1.5 times the projected area of the product multiplied by the plastic molding pressure to ensure that there is sufficient clamping force to prevent overflow. The tie rod spacing and template size must meet the installation requirements of the mold to ensure that the mold can be smoothly installed on the template and leave enough space for operation and maintenance. The maximum mold opening stroke must be greater than the sum of the height of the product and the ejection distance to ensure that the product can be smoothly demolded. In actual applications, it is necessary to select a pressure-stabilized mold clamping device with appropriate parameters based on the type of product produced and the size of the mold. At the same time, by regularly calibrating the pressure sensor and hydraulic system, the control accuracy of the device can be guaranteed to be stable in the long term, thereby improving the quality consistency and production efficiency of the injection molded products.
