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The trade-off between payload and speed of the injection molding robot

2025/06/20 By Topstar

injection molding robot 20-3

The key to selecting the right injection molding robot for your injection molding machine is to strike a balance between payload and speed. Payload refers to the maximum weight that the injection molding robot can carry, while speed refers to the speed at which the arm moves along its axis. Both factors directly affect cycle time and output, and therefore, balancing payload and speed is critical, especially when integrating these high-speed injection molding robots into complex production lines. As payload capacity increases, robot speed typically decreases due to increased inertial loads and the need for more powerful drives. Conversely, ultra-high-speed robots normally have lower payload ratings to maintain precision and position accuracy under high acceleration.

Impact of the Mechanical Design of Injection Molding Robot on Payload and Speed

The mechanical structure of an injection molding robot fundamentally determines its payload and speed capabilities. Inform manufacturers to adopt linear robots or three-axis robots for part extraction in plastic molding. Linear robots excel at horizontal movement, providing high-speed performance with payloads typically up to 10 kg, making them ideal for small and medium-sized injection molding machines. However, their vertical payload capacity decreases at maximum reach, so speed is naturally limited when carrying heavier parts over long distances.

Bringing stable torque and high-speed capabilities to the injection robot

On the other hand, 3-axis robots offer linear motion on three axes, supporting heavier payloads (sometimes up to 50 kg) but at the expense of acceleration and top speed. However, linear robots sacrifice payload when fully extended, while three-axis robots trade speed for payload and stability. Engineers often use lightweight aluminum components to reduce the robot arm’s inertia, enabling higher speeds without payload compromise.

Control systems and dynamic performance of the injection molding robot

In addition to mechanical design, control systems, and motion algorithms can also balance payload and speed. Topstar’s injection molding robots are controlled by servo drives that continuously adjust motor torque and position in response to load changes. For example, adaptive acceleration profiles automatically adjust speed during start-stop cycles to prevent overshoot and ensure gentle handling of heavy parts. For example, when lifting a 15 kg automotive part, the control system reduces peak acceleration by 20% to maintain position accuracy and avoid mechanical stress.

Additionally, we can optimize trajectory planning for the jerk, enabling the injection molding robot to exceed speed limits while maintaining smooth motion. Minimizing mechanical vibration and cyclic fatigue, these control strategies extend service life and maintain precision while also fine-tuning the injection molding robot to deliver the payload capacity and speed required for various molding applications.

Application-Driven Payload and Speed ​​Considerations

Different manufacturing scenarios require injection molding robots to make different trade-offs between payload and speed. In high-volume consumer product production, such as plastic bottle caps or miniature electronic product housings, high-speed injection molding robots with payloads of 2 to 5 kg are typically capable of maximizing throughput and achieving cycle times under 5 seconds. In contrast, in automotive or aerospace applications, parts can weigh more than 20 kg and require secondary assembly, so the robot must prioritize payload over top speed, even if that means extending the cycle time to 10 to 15 seconds.

Plastic bottle caps or small electronic product housings

Additionally, multi-step processes, such as insert molding, add further complexity. The injection molding robot must handle heavy metal inserts or reposition parts between mold cavities. Hence, it needs a strong payload capacity and sufficient speed to keep up with the injection molding machine cycle. Therefore, interlocking between the machine clamping unit and the robot axis synchronization ensures safe, collision-free operation, reducing downtime and preventing damage to sensitive parts.

Innovations in Payload Speed ​​Optimization

Recent advances include the use of harmonic drive gearboxes, which enable robots to lift heavier parts without sacrificing acceleration. Similarly, torque vectoring technology borrowed from automotive engineering can distribute motor torque to multiple axes, allowing higher payloads to be handled at faster speeds in diagonal or compound movements.

Additionally, the design of injection molding robots is now modular, enabling customers to add or remove extension links to adjust arm length and payload capacity for specific tasks. In addition, injection molding robots equipped with torque sensors can provide safe and adaptable payload handling in shared human-machine workspaces.

Effectively balance load and speed.

Balancing load and speed is a complex interaction of multiple factors, including mechanical design and control systems. We can make trade-offs by understanding how the robot architecture affects inertia, how the servo drive control optimizes motion, and how the actual use case determines performance priority. Ultimately, we must combine the specifications of the injection molding robot with your production goals to ensure that each cycle achieves maximum throughput without compromising reliability or safety.

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