Method and apparatus for production of helical springs by spring winding

Abstract

A method produces helical springs by spring winding with a numerically controlled spring winding machine, a wire is fed, controlled by an NC control program, through a feed device to a forming device of the spring winding machine and is formed with the aid of tools in the forming device to form a helical spring. A measurement time is defined which occurs in a final phase of an overall manufacturing time for the helical spring at a time period before the end of the overall manufacturing time. A position of a spring end which is formed by an end surface of the wire is measured at this measurement time to determine an actual angle position of the spring end. A remaining distance for the wire feed is then calculated to achieve a nominal angle position of the spring end, as intended for the helical spring, at a reference time which occurs at a later time and the wire is fed through the remaining distance. The method allows the relative angle position of the spring ends of a helical spring to be set very precisely.

1 . A method of producing helical springs by spring winding with a numerically controlled spring winding machine comprising:
 feeding a wire controlled by an NC control program through a feed device to a forming device;   forming the wire into a helical spring in the forming device;   defining a measurement time which occurs in a final phase of an overall manufacturing time for the helical spring at a time period before the end of the overall manufacturing time;   measuring a position of a spring end formed by an end surface of the wire to determine an actual angle position of the spring end at the measurement time;   determining a remaining distance for the wire feed required to achieve a nominal angle position of the spring end, as intended for the helical spring, at a predefined reference time which occurs at a time after the measurement time; and   feeding the wire through the remaining distance.   
     
     
         2 . The method according to  claim 1 , wherein the reference time corresponds to the end of the overall manufacturing time. 
     
     
         3 . The method according to  claim 2 , wherein an opposite spring end is produced immediately after reaching the reference time by separating the helical spring which has been produced from the fed wire. 
     
     
         4 . The method according to  claim 1 , wherein the reference time is an intermediate time which occurs at a time before the end of the overall manufacturing time, wherein, after passage through the remaining distance, a predefined final part of the manufacturing time passes to the end of the overall manufacturing time, and the helical spring which has been produced is then separated from the fed wire. 
     
     
         5 . The method according to  claim 1 , wherein a camera with a two-dimensional field of view measures the position of the spring end, and the camera is arranged such that an end section of the helical spring with the spring end lies within a field of view at the measurement time. 
     
     
         6 . The method according to  claim 5 , wherein the camera is arranged alongside a path of the helical spring such that an observation direction is aligned transversely to a longitudinal direction of the helical spring. 
     
     
         7 . The method according to  claim 6 , wherein the actual angle position of the spring end is determined from data from the field of view by determining a distance value for a distance, which is measured transversely to a longitudinal axis of the helical spring, between a tangent to an external contour of a turn on a circumference of the helical spring and a projection of the spring end in the field of view. 
     
     
         8 . The method according to one  claim 1 , wherein a relative orientation of the spring end is determined at the measurement time with respect to an observation direction, and the measured distance value is corrected as a function of the orientation. 
     
     
         9 . The method according to  claim 1 , wherein the measurement time is selected as a function of geometric data of the helical spring such that, in a remaining time interval required to move through the remaining distance, at least one turn of the helical spring is produced. 
     
     
         10 . The method according to  claim 1 , wherein a feed movement of the wire is interrupted to carry out measuring the position of the spring end. 
     
     
         11 . The method according to  claim 1 , wherein at least one further measurement is carried out after the end of the overall manufacturing time and before cutting off the helical spring from the wire fed through the feed device. 
     
     
         12 . The method according to  claim 11 , wherein an overall length of the finished helical spring is determined on the basis of the further measurement. 
     
     
         13 . A spring winding machine that produces helical springs by spring winding under the control of an NC control program according to the method of  claim 1  comprising:
 a feed device; and 
 a forming device that receives wire from the feed device and comprises at least one winding tool which controls the diameter of the helical spring at a predeterminable position, and at least one pitch tool whose action on a helical spring being produced controls a local pitch of the helical spring. 
 
     
     
         14 . The spring winding machine according to  claim 13 , further comprising a camera positioned at a distance from the forming device such that a free spring end section runs into a field of view of the camera in a final phase of production of the helical spring. 
     
     
         15 . A computer program product stored on a computer-readable medium or in the form of a signal, wherein the computer program product results in the computer carrying out the method according to  claim 1  when the computer program product is loaded in the memory of a computer and is run by a computer of a spring winding machine.