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Solve the problems of ejection failure and mold sticking of hydraulic injection molding machine

2025/05/21 By Topstar

Hydraulic injection molding machine10-10

Ejector failure and mold sticking are common problems when using hydraulic injection molding machines, which often lead to production downtime, manual part removal, and increased material waste. And these problems are particularly serious in South American manufacturing environments, where high humidity and temperature changes can exacerbate resin adhesion to the mold surface. The main reasons include insufficient ejector force, poor mold opening stroke, large temperature differences in the mold, and uneven clamping pressure. Topstar will comprehensively solve this problem by combining the causes of the problem and leveraging the advantages of the hydraulic injection molding machine.

Enhanced hydraulic injection molding machine ejector thrust for reliable demolding

One of the most common causes of hydraulic injection molding machine ejector failure is insufficient ejector force, causing the molded part to stick to the core or cavity surface. To solve this problem, Topstar’s hydraulic injection molding machine will increase the ejector thrust by 20%, using a large-capacity ejector cylinder driven by an oversized piston and reinforced seals to achieve consistent, repeatable, and powerful ejector force. The upgraded ejector assembly contains hardened steel rails and precision linear guides to minimize friction and deflection under load, ensuring that the mold ejector plate moves at a perfect angle. This improvement is particularly beneficial when working with high-shrinkage materials, such as nylon or glass-filled polymers, which are common in the automotive sector and electronics manufacturing. The result is cleaner part demolding, fewer mold interventions, and significantly reduced scrap and downtime.

Ejection force

Extra-long stroke opening accuracy for the hydraulic injection molding machine

Reliable part demolding also depends on the mold opening completely and accurately to prevent part ejection and residual clamping. With extra-long mold opening strokes, Topstar’s hydraulic injection molding machines can easily handle even the largest and most complex multi-cavity molds, ensuring mold opening position accuracy within ±1 mm. At the same time, high-response proportional valves regulate the hydraulic flow to the tie rod cylinders for smooth, vibration-free movement. This extended mold opening stroke ensures that the part has ample space to drop by gravity or be picked up by an injection robot, reducing the risk of damage. Fast, controlled mold movement reduces cycle times because the system avoids the dwell time required by traditional hydraulic units, thereby increasing overall output.

Extra-long stroke opening accuracy for hydraulic injection molding machines

Angled five-point tether design for greater stability

The angled five-point tether design maintains platen parallelism at maximum clamping force, which avoids uneven cavity pressure that causes sticking. Hydraulic injection molding machines use an angled five-point tether design that combines angled links and spherical bearings into a compact, highly rigid frame. This configuration provides excellent load-bearing capacity and evenly distributes clamping pressure across the mold surface, maintaining parallelism within 0.05 mm. The compact linkage minimizes deflection and optimizes space efficiency on the factory floor. In addition, high-strength steel platens and sturdy tie rods resist bending under cyclic loads, maintaining long-term alignment. This structural integrity makes it easier and ensures efficient generation of large-volume production.

Angled five-point tether design for greater stability

Fast, stable platen movement for increased throughput

High-speed mold opening and closing without overshoot or vibration maintains hydraulic injection molding machines’ cycle time and part quality. Topstar solves this problem by using high-flow proportional servo valves to control the clamping and injection circuits, combined with large-diameter tie rod cylinders for fast platen acceleration. Oil accumulators complement these valves, providing instant hydraulic oil during the acceleration phase to meet peak demands and ensure smooth deceleration. The result is a mold opening and closing time of less than 1.2 seconds and minimized mechanical shocks that could cause part deformation or mis-ejection. This ensures high throughput production, reduces wear on injection molding machine components, and improves part consistency in every cycle by providing consistent, controlled platen movement.

Thermal and mold maintenance considerations

Even with optimized mechanical structures, mold sticking can occur if mold temperature control and maintenance programs are inadequate. Topstar’s hydraulic injection molding machines integrate seamless interfaces with mold temperature controllers to precisely regulate cooling circuits and maintain constant cavity temperatures. At the same time, thermocouples embedded near critical areas provide real-time feedback to the machine to adjust process parameters to eliminate cold spots and reduce resin sticking. In addition, the system features an automatic lubrication program for guide rails and ejector components that is scheduled according to cycle times to maintain smooth operation. These maintenance alerts, combined with modular hydraulic power units, allow technicians to quickly make repairs without extended downtime, ensuring that the entire line in injection molding can be maintained in optimal condition and virtually eliminating mold sticking incidents.

Ensure consistent demolding performance

From the 20% increase in ejector thrust, the ultra-long mold opening stroke with an accuracy of up to ±1 mm, to the stability of the inclined five-point machine twist design, and the high-speed servo-driven platen movement, the hydraulic injection molding machine works together to provide consistent demolding reliability. For South American plastics manufacturers facing strict production targets and quality requirements, Topstar’s hydraulic injection molding machines can minimize scrap, reduce manual intervention, and maintain high production.

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