Maximum Torque

Description

The maximum tightening torque achievable with an automatic screwdriver mounted on a Universal Robot without triggering a protective stop or a force limitation error depends on several factors, including:

  • Tool mounting

  • Robot programming

  • Safety settings

  • Robot poses

  • Payload

  • Others not directly related with the robot, e.g., the tightening setup in the controller of the screwdriver that determines the strategy, torque, speed, angle, etc.

 
Torque Evaluation

The joint positions and payload determine how much torque from the joints is required to maintain the robot position, and subsequently how much of the torque generation capacity of the joints (its maximum torque values depend on the different joint sizes) is remaining and available to complete the task. Robot tool positions and force limits can also further restrict how much of the remaining joint torque capacity is allowed to be used. The way the tool is mounted to the robot changes the amount of force from the tightening process that the robot is impacted by and must counteract. If the robot is steady (standing still with zero target velocity) the torque restrictions can be less tight and the allowed joint position deviations before triggering a protective stop larger, which would be more favorable to the robot in the process.

 

Taking all of this into account, the screwdriving torque withstanding capabilities for a UR10/UR10e (the most frequent robot in high torque screwdriving applications) can be categorized as follows:

 

  • < 30 Nm – basic application, not considered high torque

  • 30 – 60 Nm – advanced, requires consideration of some of the above factors

  • 60 – 100 Nm – expert, requires consideration of all the above factors

  • > 100 Nm – not extensively researched, most likely requires innovative technologies or additional hardware