Clamp Force Control


DEPRAG CFC – constant clamp force despite fluctuating driving torque!

DEPRAG Clamp Force Control (CFC) produces a consistent clamp force when prevailing torque values fluctuate; this innovative adaptive screwdriving process works by recognizing the head contact (seating point) and customizing the screw assembly applying differential torque or a defined angle.

DEPRAG Clamp Force Control minimizes the impact of material and joint variations that would otherwise result in failed joints. When precision and performance matter, DEPRAG CFC is a gamechanger.

This adaptive screwdriving procedure ensures a constant clamp force when drive-in torque values are fluctuating. The whole screw assembly consists of the head contact recognition and a screw assembly to differential torque or a specific angle.

The specific area of application is direct screwdriving into plastic and metal. The new screwdriving procedure for DEPRAG EC servo screwdrivers, with the AST40, is used for hugely varying tightening torques.

These fluctuations may result from alterations in the geometry of the screws or hole, the component's material structure, variations in the screw thread's surface quality, the elasticity of elements or seating processes. The positive recognition of head contact results in a constant clamp force.

  • Improved constancy of the pre-load force
  • The Calculation takes into account coincidental fluctuations in the torque during the process, which is not caused by head contact
  • Minimal parameter adjustments
Method of Calculation:

The main element is the head contact recognition: based on the torque flow; a mathematical valuation function is continually generated. Head contact is deemed to be recognized as soon as this function exceeds a fixed limit value. Torque and angle are calculated backward to the moment of head contact.

Screwdriving Procedure:

clamp force control graph 2

Torque procedure example – parameter head contact recognition screw template The upper torque limit serves as the shut-off criteria for the screwdriving step. The OK window for seating recognition can be monitored using the seating point torque upper/lower limit. The end values of the screwdriving template seating recognition provide the reference for the following program section.

clamp force control graph 3

Screw assembly to differential torque relating to head contact recognition Screw assembly to the angle can follow instead of screw assembly to differential torque.

Please contact us for more information.