Device for direct screwing of structural components, in particular for flow hole screwing

Abstract

A method for direct screwing, in particular flow hole screwing, includes producing a hole in a first stage in a structural component without cutting and forming a thread with a flow hole screw in a second stage. A feed and feed force are produced by a non-pneumatic feed drive and transmitted to a screw shaft rotated by high feed force and high rotational speed in the first stage and at a defined switchover point with penetration of the structural component a switchover is made to the second stage with lower feed force and slower rotational speed. A drive parameter correlated to the feed force, especially a motor current of an electric motor of the feed drive, is monitored and a characteristic change of this parameter is defined as switchover point. A rapid switchover with process stability is attained and damage to the flow hole screw thread is avoided.

1 . A device for direct screwing or flow hole screwing of structural components, the device comprising:
 a rotatably drivable screw shaft configured to be moved in an axial direction to exert a feed;   a non-pneumatic feed drive for generating a feed and a feed force and for transmitting said feed and said feed force to said screw shaft; and   a control unit for controlling a flow hole screwing procedure, said control unit setting a high rotational speed of said screw shaft and a high feed force produced by said non-pneumatic feed drive in a first process stage and switching over to a lower feed force and a slower rotational speed at a defined switchover point for a second process stage; and   said control unit monitoring a parameter correlated at least with said feed force and defining said switchover point upon reaching a characteristic value or upon a characteristic change of a value of said parameter.   
     
     
         2 . The device according to  claim 1 , wherein said control unit is configured to define the switchover point immediately with penetration of the structural component and before starting formation of the thread. 
     
     
         3 . The device according to  claim 1 , wherein, following the switchover, a cylindrical passage is formed in a sub-step before the thread is formed. 
     
     
         4 . The device according to  claim 1 , wherein said parameter is a drive parameter of said feed drive. 
     
     
         5 . The device according to  claim 1 , wherein said feed drive comprises a first electric motor. 
     
     
         6 . The device according to  claim 5 , wherein said parameter is a motor characteristic. 
     
     
         7 . The device according to  claim 6 , wherein said parameter is a motor current of said first electric motor. 
     
     
         8 . The device according to  claim 1 , wherein said feed drive has a predefined maximum feed rate. 
     
     
         9 . The device according to  claim 1 , said feed drive has a predefined maximum feed force. 
     
     
         10 . The device according to  claim 8 , which further comprises:
 wherein said feed drive has a predefined maximum feed force; and   at least one of the maximum feed force or the maximum feed rate are parameterized.   
     
     
         11 . The device according to  claim 1 , wherein said control unit is configured to automatically carry out a switchover a number of times between the first process stage and the second process stage under predefined conditions during a flow hole screwing procedure. 
     
     
         12 . The device according to  claim 11 , wherein said control unit is configured to:
 define a further switchover point with a characteristic rise of the feed force in the second process stage; and   switch over again into the first process stage with the high feed force.   
     
     
         13 . The device according to  claim 1 , wherein said screw shaft is rotated by using an additional screw drive having a second electric motor with a controller for a controlled screwing procedure. 
     
     
         14 . The device according to  claim 1 , wherein:
 the first process stage is defined with a feed force of greater than 1000 N and a rotational speed for the screw shaft in a range from 5000 rpm to 8000 rpm; and   the second process stage is defined with a feed force in a range of up to 500 N and a rotational speed in a range from 500 to 2500 rpm.