Method for controlling an intermittently operating screw tool
In the method for controlling an intermittent screw process first a torque mode (DMM) is applied in which the torque is continuously measured. Upon attainment of a pre-torque (M F ) a rotation angle mode (DWM) is carried out in which the rotation angle is measured. Proceeding from the rotation angle α=0 (corresponding to the pre-torque (M F )) the rotation angle (α) is counted up during each stroke. In this connection that torque (M HE ) is stored which has been reached at the end of the stroke. During the next stroke the angle (α) is continued to be counted only when the torque (M HE ) at the stroke end of the previous stroke has been reached again. Upon attainment of a target angle (α z ) the screw process is terminated.
1. A method of automatically controlling a screw tool which carries out intermittent rotating strokes and includes a torque sensor ( 23 ) and a rotation angle sensor ( 33 ) comprising the steps of:
carrying-out intermittent reciprocal strokes to rotate a screw tool while measuring the torque (M D ) in a torque mode (DMM),
upon attaining a predetermined pre-torque (M F ) transitioning to a rotation angle mode (DWM) and thereby count-up the rotation angle (α) up to the end of the current stroke, and storing the rotation angle (α HE1 ) and torque (M HE1 ) values attained at the end of the current stroke,
performing subsequent intermittent reciprocal strokes and during each continuing counting-up the rotation angle (α) when the torque (M D ) has reached a value corresponding to the torque (M HE ) at the end of the previous intermittent reciprocal stroke, and storing the rotation angle (α HE ) and torque (M HE ) values attained at the end of each subsequent reciprocal intermittent stroke, and
terminating the screw process when the counted-up rotation angle has reached a target angle (α Z ).
2. The method of automatically controlling a screw tool as defined in claim 1 wherein the rotation angle mode (DWM) is started only when the pre-torque (M F ) is obtained.
3. The method of automatically controlling a screw tool as defined in claim 1 wherein after attainment of the pre-torque (M F ) during a stroke the counted-up value remains below a predetermined limit value, the attained pre-torque (M F ) is not utilized and the utilization of the pre-torque (M F ) is shifted to the next stroke.
4. The method of automatically controlling a screw tool as defined in claim 1 wherein before attaining the pre-torque (M F ) the differential quotient (Q) of the interdependence of torque (M D ) and rotation angle (α) is determined and stored, and on the basis of the respective measured torque and the differential quotient (Q) a determination is made whether the pre-torque (M F ) will be reached at the end of the stroke.
5. The method of automatically controlling a screw tool as defined in claim 1 wherein the differential quotient (Q) of the interdependence of torque (M D ) and the rotation angle (α) is determined and stored, and the screw process is discarded when during counting-up of the rotation angle (α) an out-of-tolerance deviation of the differential quotient (Q) from the stored value is detected.
6. The method of automatically controlling a screw tool as defined in claim 5 wherein a narrower special tolerance range is defined in an angle range before attaining the target angle (α Z ) with the screw process being discarded when the special tolerance range is exceeded.
7. The method of automatically controlling a screw tool as defined in claim 1 including the step of measuring the individual strokes and discarding the screw process when the duration is too long.
8. The method of automatically controlling a screw tool as defined in claim 2 wherein after the attainment of the pre-torque (M F ) during a stroke, the counted-up value remains below a predetermined limit value, the attainment of the pre-torque (M F ) is not utilized and the utilization is shifted to the next stroke.
9. The method of automatically controlling a screw tool as defined in claim 2 wherein prior to the attainment of the pre-torque (M F ), the differential quotient (Q) of the interdependence of torque (M D ) and rotation angle (α) is determined and stored, and on the basis of the respective measured torque and the differential quotient (Q) it is predetermined whether the pre-torque (M F ) will be reached at the end of the stroke.
10. The method of automatically controlling a screw tool as defined in claim 3 wherein prior to the attainment of the pre-torque (M F ), the differential quotient (Q) of the interdependence of torque (M D ) and rotation angle (α) is determined and stored, and on the basis of the respective measured torque and the differential quotient (Q) it is predetermined whether the pre-torque (M F ) will be reached at the end of the stroke.
11. The method of automatically controlling a screw tool as defined in claim 2 wherein the differential quotient (Q) of the interdependence of torque (M D ) and the rotation angle (α) is determined and stored, and the screw process is discarded when during counting-up of the rotation angle (α) an out-of-tolerance deviation of the differential quotient (Q) from the stored value is detected.
12. The method of automatically controlling a screw tool as defined in claim 3 wherein the differential quotient (Q) of the interdependence of torque (M D ) and the rotation angle (α) is determined and stored, and the screw process is discarded when during counting-up of the rotation angle (α) an out-of-tolerance deviation of the differential quotient (Q) from the stored value is detected.
13. The method of automatically controlling a screw tool as defined in claim 4 wherein the differential quotient (Q) of the interdependence of torque (M D ) and the rotation angle (α) is determined and stored, and the screw process is discarded when during counting-up of the rotation angle (α) an out-of-tolerance deviation of the differential quotient (Q) from the stored value is detected.
14. The method of automatically controlling a screw tool as defined in claim 2 including the step of measuring the individual strokes and discarding the screw process when the duration is too long.
15. The method of automatically controlling a screw tool as defined in claim 3 including the step of measuring the individual strokes and discarding the screw process when the duration is too long.
16. The method of automatically controlling a screw tool as defined in claim 4 including the step of measuring the individual strokes and discarding the screw process when the duration is too long.
17. The method of automatically controlling a screw tool as defined in claim 5 including the step of measuring the individual strokes and discarding the screw process when the duration is too long.