application research

Shock Absorbers for Servo-Driven Axes and Robot Transfer Units

How to specify mechanical energy absorption for servo-driven slides, robot transfer units and automated handling axes.

Direct answer

For a servo-driven axis or robot transfer unit, treat the mechanical absorber as a defined stopping-duty component, not as a substitute for motion control. Establish the maximum credible moving mass and approach speed, whether motor torque can continue during compression, available stroke, axis stiffness and the number of normal or abnormal stop events. Then verify energy, force and mounting capacity against the selected absorber.

Questions this page answers

How do I select a shock absorber for a servo-driven axis?
Should a robot transfer unit have a mechanical energy absorber?
What happens if a servo axis reaches its mechanical end stop?

Required inputs

movingMassKgmaximumApproachSpeedMpsaxisStrokeMmavailableAbsorberStrokeMmmotorForceOrTorquecontrolStopBehavioraxisStiffnesscyclesPerHour

Formula logic

Motor-force work

If the drive can keep applying force while the absorber compresses, add that work to the kinetic energy before comparing the model rating.

W = F x s

Unit: N m

Review steps

1
Separate controlled stops from credible contact cases
Servo deceleration normally occurs in the motion profile. Document separately any commissioning, overshoot or fault case in which a mechanical absorber may be contacted.
2
Confirm the load seen by the absorber
Include the moving carriage, tooling, gripper, cable carrier and payload. Check reflected load and compliance in belt, rack or ballscrew systems where it changes impact behavior.
3
Review the installation as an axis assembly
Ensure the striker is guided, the absorber is loaded axially and the mounting bracket can transfer the stopping force without deflecting into the machine envelope.

Common mistakes

Using the programmed velocity limit without verifying maximum approach speed during setup or fault recovery.
Omitting drive force because the servo is normally controlled, even though torque can remain present during contact.
Mounting the absorber where a flexible bracket or belt compliance creates off-axis contact.

Technical notes

Industrial robot installations have remained above 500,000 units annually for four consecutive years, increasing the number of automated axes where mechanical end-stop duty needs clear definition.

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