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Home / How Do Ejector-Following Control and Servo Torque Detection Protect Ejector Pins?

How Do Ejector-Following Control and Servo Torque Detection Protect Ejector Pins?

2026/11/09 By le zhan

How Do Ejector-Following Control and Servo Torque Detection Protect Ejector Pins

During part removal on an injection molding robot, poor coordination between the robotic arm, mold ejector pins, and the part-removal sequence can cause collisions, leading to bent ejector pins, mold damage, or product deformation. Topstar effectively mitigates these risks through its “Ejector-Following Control” and “Servo Torque Detection” features, enabling the robotic arm to respond flexibly to external forces rather than mechanically executing preset movements. By adjusting joint torque in real time, monitoring abnormal loads, and adding an interlock between the ejector pins and the core-pulling mechanism, Topstar’s injection molding robots ensure reliable part removal while protecting critical mold components.

Ejector-Following Control: How Does a Torque-Based Protection Mechanism Prevent Mechanical Collisions?

During automated part removal, the injection molding robot must enter the mold cavity and coordinate its movements with the mold ejector pins. If positioning deviations or unexpected contact occur and the robot continues along its original trajectory, it can cause excessive mechanical stress. With flexible joint control and servo torque monitoring, the injection molding robot can detect abnormal contact and adjust its response before excessive force damages the mold or ejector pins.

How Does a Torque-Based Protection Mechanism Prevent Mechanical Collisions

How Does the Flexible Motion Enabled by Ejector-following Control Protect the Ejector Pins?

Traditional injection molding robot motion strictly follows a preset trajectory. If the robotic arm contacts the ejector pins due to positioning errors or timing discrepancies, it may continue applying force instead of adapting to the contact situation.

Ejector-following control technology enables the robotic arm to respond flexibly to external forces by adjusting joint torque in real time. Specifically, when the robotic arm comes into contact with the ejector pin, the system monitors the resulting torque; once the detected force exceeds a preset threshold, the system activates the “flexible floating” function, allowing the robotic arm to adjust accordingly based on the contact situation rather than forcibly executing the originally planned motion.

This controlled motion cushions unexpected contact and reduces forces transmitted to the ejector pins and the mold.

Its key advantages include:

  • Reducing the risk of collisions during mold insertion and part removal.
  • Preventing excessive mechanical stress on the ejector pins.
  • Reducing the likelihood of mold damage caused by positioning deviations.
  • Facilitating installation, commissioning, and maintenance through smooth, manual movement.

How Does Servo Torque Sensing Detect Abnormal Contact?

Flexible motion protects contact; equally important is the robot’s ability to detect abnormal mechanical loads during commissioning and production.

Therefore, Topstar has integrated servo torque sensing technology into its Cartesian robots to identify abnormal contact conditions by monitoring changes in servo torque. For example, if the operator sets an incorrect robot position, or if the gripper approaches the mold at an unexpected angle, the robotic arm may encounter resistance that exceeds the normal operating range.

When the detected torque exceeds a preset threshold, the protection mechanism triggers a flexible response, thereby reducing excessive forces acting on the gripper, mold ejector pins, and other mechanical components.

Servo torque detection is particularly effective in the following scenarios:

  • During initial robot installation and mold debugging.
  • When adjusting grasping and removal positions.
  • During automated operations where positioning deviations may occur.
  • During repetitive high-speed movements requiring precise stopping positions.

Excessive robot torque can damage molds, ejector pins, and molded products, increasing scrap rates and causing unplanned downtime.

How Does Servo Torque Sensing Detect Abnormal Contact

How Does Machine Interlocking Prevent Damage to Ejection and Core-Pulling Mechanisms?

Torque protection alone cannot resolve all ejection-related issues. Some failures occur because operations between the injection molding machine and the Cartesian injection molding robot are improperly sequenced. For example, the mold ejection mechanism may retract before the robot has fully removed the product, or the core-pulling action may begin while the part is still engaged with the mold. Topstar ensures all mechanical actions follow the correct production sequence through signal coordination between the robot and the injection molding machine, along with precise control of ejection and core-pulling motions, effectively mitigating the risks above.

How Does Machine Interlocking Prevent Damage to Ejection and Core-Pulling Mechanisms

How Does Ejection and Core-Pulling Interlocking Protect the Mold?

During demolding, the robot, ejector pins, and core-pulling mechanism must operate in the correct sequence. Topstar’s injection molding robots support ejection synchronization (linking ejection forward and reverse movements), keeping their actions highly synchronized with the injection molding machine.

If the molded part has not yet been successfully removed, the corresponding ejection or core-pulling actions should not be executed prematurely. This effectively prevents the ejection pins from squeezing residual material, avoids robot-mold collisions, and stops the robot from crushing the part during demolding.

The principle is simple: before executing the next mechanical action, first confirm that the preceding operation has been completed. This mechanism adds a layer of sequence protection beyond torque-based collision protection.

How Does Ejection and Core-Pulling Interlocking Protect the Mold

How Do These Protective Functions Work Together?

These protective technologies are designed for different stages of the product removal process. Their effectiveness comes from coordinated cooperation across multiple functions, rather than relying on a single protective measure.

The specific protection process is as follows:

Before removal: Before the robot enters the mold area, it first verifies that the mold is open and the ejection mechanism is in the correct state. During contact: When abnormal contact exceeds a preset threshold, the ejector pin follow-up control function adjusts the joint torque and activates flexible floating mode.

When abnormal load occurs: The servo torque detection function identifies excessive resistance and helps prevent the continued application of destructive forces.

After product removal: The interlock function between the ejector pins and the core-pulling mechanism verifies that the operational sequence meets requirements, ensuring the process is error-free before the next mold cycle.

During debugging, engineers should verify parameters such as torque thresholds, robot entry positions, ejector pin signals, and product removal confirmation based on the actual mold and fixture configurations.

Overall, the ejector-following control enables compliant motion, “servo torque detection” identifies abnormal contact, and the interlock function between the ejector pins and the core-pull mechanism prevents conflicts between mechanical movements. Together, these functions protect the ejector pins, reduce the risk of mold collisions, and ensure reliable injection molding production.(For more information on Topstar’s injection molding robot technologies, please visit: Injection Molding Robot Technology)

 

 

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