The Importance and Key Factors of Clamping Force in Injection Molding
Introduction
With global companies actively promoting ESG sustainable business practices and the rapid rise of the electric vehicle industry, the demand for plastic components—such as lightweight automotive parts, composite material interior trim components, and smart optical automotive lights—has increased significantly. These components are being designed with greater precision and complexity, and the trend toward small-batch, diversified production has made the performance requirements of injection molding machines increasingly stringent. In particular, under the dual demands of product quality stability and production efficiency, the uniformity and accuracy of clamping force have become critical influencing factors.
Figure 1: FCS’s Commitment to ESG Sustainable Development Goals
The Correlation Between Injection Molding and Clamping Force
During the injection molding process, the mold must withstand high-pressure injection. Therefore, an appropriate clamping force is essential to maintain mold closure, prevent flash, and ensure product dimensional accuracy. The most important factors are the stability and uniformity of the clamping force. The magnitude of the clamping force affects the mold support and venting behavior. A reasonable and stable clamping force not only maintains dimensional stability during melt filling but also prevents mold damage; at the same time, the uniformity of clamping force on the four tie bars directly affects product quality. If the clamping force is unevenly distributed, it can easily lead to mold misalignment, flash formation, and even tie bar breakage and mold damage, which in turn may cause production interruptions and increased maintenance costs.
Causes of Clamping Force Deviation
During the injection molding production process, the clamping force may deviate due to several factors, mainly including:
- Increase in Mold Wall Temperature: During production, the high temperature of the melt is transferred to the mold wall via heat conduction, thereby affecting the stability of the clamping force.
- Variation in Hydraulic Oil Viscosity: As the temperature changes, the viscosity of the hydraulic oil in the system will change, influencing the force transmission of the clamping mechanism.
- Tie Bar Fatigue: Prolonged operation can lead to material fatigue in the tie bars, reducing their rigidity and causing uneven clamping force distribution.
- Environmental Temperature Changes: Changes in the ambient temperature within the factory can also affect the stability of machine operations.
- Mechanical Friction Heat and Mold Heat Conduction: The friction heat generated during mechanical operation and the inherent heat conduction of the mold further affect the performance of the clamping force.
Methods to Improve Clamping Force Uniformity
To ensure the quality stability of injection molded products, it is necessary to improve the uniformity and stability of the clamping force. This can be achieved through the following methods:
- Increasing Mold Wall Rigidity: Strengthening the mold wall structure can reduce deformation under load and improve the uniformity of clamping force distribution. However, merely increasing the mold wall thickness to enhance rigidity will only slow down the machine’s response; therefore, enhancing rigidity through material selection and structural design is the best approach.
- Improving the Clamping Structure: Changing from the traditional inward toggle design to an outward toggle structure helps improve the distribution of force flow, ensuring that the clamping force is applied more uniformly to the mold.
- Real-Time Monitoring and Feedback Control Systems: By using sensors to monitor in real time the clamping force changes on the four tie bars and automatically adjusting for compensation, the clamping force can be maintained consistent with the set value.
The Impact of Clamping Force Settings
The clamping force setting must be precisely adjusted based on the product characteristics and mold design. If the clamping force is set too low, the mold may be forced open under high-pressure injection, leading to flash (excess material) issues; conversely, if set too high, poor venting can cause defects such as burn marks at the end of the fill, and may even cause template deformation.
| |
| (a) | (b) |
Figure 2: Product Defects Caused by Poor Clamping Force: (a) Flash (b) Burn Marks
Figure 3: Analysis of Template Deformation
In addition, the design of the machine’s clamping structure has various impacts on the clamping force settings. For example, in an injection molding machine with an inward toggle design, since the toggle locking point is located on the outward side of the mold wall, the direction of the force flow tends to cause higher pressure on the periphery of the mold than at the center. If the clamping force is set too high, it is more likely to result in mold deformation and cavity wall distortion. In contrast, the outward toggle design with a centralized clamping mechanism allows for a more uniform distribution of clamping force, effectively reducing flash issues and is particularly suitable for older molds.
Advantages of the FCS SA Series Outward Toggle Injection Molding Machines
FCS has been promoting ESG principles from the beginning of its product development, focusing on high performance, high efficiency, and high flexibility, which led to the development of the SA series. This series covers outward toggle injection molding machines ranging from 100 to 3200 tons. Through optimized force flow analysis, the uniformity of applied force is enhanced and mold wall deformation is reduced. Additionally, with optimized mold plate design, the rigidity of the mold plate is increased by 30% while its weight is reduced by 11.5%, thereby improving the machine’s responsiveness.
The SA series offers an optional automatic feedback control module for tie-bar clamping force. This module automatically calibrates and adjusts during production without the need to stop the machine, ensuring optimal performance at all times. In addition, the module is equipped with a clamping force deviation warning function that can provide an immediate alert when deviations exceed the risk threshold, effectively reducing downtime risks.
The combination of the SA series outward toggle injection molding machine and the automatic feedback control module for tie-bar clamping force is the best solution for ensuring clamping force uniformity. It is particularly suitable for high length-to-width ratio products such as automotive optical components and bumpers, as well as for multi-cavity bottle preform products.
Figure 4: SA Series Outward Toggle Injection Molding Machine
Outward Toggle Injection Molding Machine (SA Series)
| Introduction It is a newly-released servo hydraulic energy-saving model with outward toggle clamping unit. The applicable industries include houseware, stationary, automotive, 3C and home appliance, especially for multi function printers, laptop or computer parts. Its larger clamping stroke is also suitable for deep barrel type products. With clamping force ranging from 100 tons to 3,200 tons.
|
