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Importance of Injection Molding Machine Frame Rigidity

2025/06/16 By Topstar

Frame rigidity

Frame rigidity refers to the ability of the machine’s structural frame to resist deformation under load. When the injection moulding machine applies high clamping and injection pressures, the frame must maintain its shape to ensure the mould is accurately aligned. Any slight deviation can result in flashing, under-injection, or uneven part filling. Additionally, a rigid frame in a plastic injection moulding machine reduces vibration during high-speed injection, thereby improving the surface finish and dimensional accuracy of the moulded parts. The rigidity of the injection moulding machine frame is necessary to ensure consistent cycle performance and part quality.

The effect of frame rigidity on injection moulding machine accuracy

A high-rigidity frame is directly related to the accuracy of injection moulding machines. During the clamping movement, any frame deflection under the clamping force will cause relative displacement between the two halves of the mould, resulting in mould misalignment and a flash on the parting line. Additionally, during injection, the screw barrel converts lateral force into an eccentric load, causing the melt front to progress unevenly. The high-rigidity frame can resist these forces and maintain the parallelism between the fixed platen and the moving platen. As a result, uniform cavity filling and tighter dimensional tolerances can be achieved.

During the manufacturing process, we utilise designs featuring wide support feet to provide stable and dynamic support. Make the mould opening and closing smooth to protect the mould and the machine better. At the same time, we also calibrate the tie rod preload to prestress the frame, ensuring that the operating force can offset the residual stress. Consistent calibration reduces wear on the mould surface, and the rigid frame minimises the need for frequent mould maintenance.

Interchangeable molds for all electric injection molding machine

Enhance mould life through the rigidity of the injection moulding machine frame.

Mould costs account for a considerable portion of the total cost of injection moulding, and the rigidity of the frame also affects the mould’s lifespan. When the frame of a plastic injection moulding machine bends under high loads, the resulting misalignment applies uneven stress to mould components, such as cores, cavities, and ejection systems. When used for an extended period, it can cause premature wear, damage, and even breakage of the mould. On the other hand, a high-rigidity injection moulding machine frame can also evenly distribute the clamping force and injection force across the entire mould surface, thereby eliminating stress concentration.

In addition, the increase in frame rigidity can enhance thermal stability. Because the mould halves are in constant contact, heat transfer between the mould and the machine platen becomes more predictable, which reduces thermal cycling stresses in the mould steel. Therefore, when the frame stiffness is improved, the mould life can also be extended.

Injection molding machine mold

Role in high-speed plastic moulding machine operation

In injection moulding with high speeds and faster cycle times, the operation of high-speed plastic moulding machines pushes the frame stiffness to its limits. During high-speed injection, accelerations can exceed 5 m/s², and the resulting inertial forces tend to bend the frame, resulting in jet or flow marks on the part’s surface. Siemens’ research shows that frames exceeding a stiffness threshold reduce dynamic deflection, enabling operators to control cycle times below two seconds while maintaining part integrity.

Therefore, we will avoid resonance by combining the frame with external reinforcement and high-grade alloy steel while adjusting the acceleration curve to match the natural frequency of the frame. Of course, we will also equip the plastic moulding machine with real-time vibration sensors, allowing operators to detect frame bending anomalies early and adjust parameters dynamically. Operators adjust the frame stiffness to sustain high-speed injection moulding productivity.

injection moulding machine 19-2

Maintenance strategies to maintain frame rigidity

Technicians should regularly check and torque the anchor bolts during maintenance, as loose bolts may cause the machine to shift under load. You should also check tie rod preload annually—if measurements show tie rod slack outside the manufacturer’s tolerance, the tie rods should be retightened or replaced. Next, verify the integrity of the hydraulic manifold, as leaks or pressure loss can reduce the injection moulding machine’s clamping force, which can indirectly cause frame deformation.

Also, monitor the flatness and levelness of the machine floor—uneven support surfaces can cause uneven loading and accelerate frame fatigue. Some plants implement vibration analysis during planned downtime to detect early signs of frame microcracks or weld fatigue. Operators can perform such inspections quarterly and record the results in a centralised maintenance management system. Maintaining frame rigidity through systematic maintenance can safeguard machine accuracy.

Providing precise mold alignment and preventing part deviation

Injection moulding machine frame rigidity is fundamental to every aspect of moulding operations, from part accuracy and mould life to high-speed performance and long-term reliability. By choosing a machine with a highly rigid frame, you can ensure precise mould alignment, prevent costly deviations in part tolerances, and maintain rigidity by proactively checking the foundation and tie rods, thereby guaranteeing consistent cycle times even under the most demanding conditions.

 

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