OnRobot HEX-E QC User Manual page 202

HARDWARE SPECIFICATION
The hole thread is different from the screw thread
•
The hole thread is not clean (for instance by deburrs from CNC machining)
•
• The friction between the screw thread and the hole thread is too low or too high
The friction between the screw head and the tighten part is too low or too high
•
A torque gradient variable is made available to be checked in the robot program.
The graph below shows a normal Torque/Angle curve. In this case has been made with a M4
screw and 2.4 Nm as target torque.
Torque angle curve Metric
Torque angle curve US Standard
202