Angular orientation control system for friction welding

Abstract

A method of friction welding first and second parts together at an angular orientation relative to each other includes the steps of mounting the first part in a spindle for axial rotation and the second part in a non-rotatable holder. The spindle is then rotated and the angular orientation of the first part relative to the second part is determined at any specific time. The holder is moved toward the spindle to bring the second part into frictional contact with the first part at a selected one of the specific times that the angular orientation is determined. Accordingly, due to frictional contact, the respective contacting surface of the parts are melted. The speed of the rotation of the spindle is then decreased and the holder is moved toward the spindle to forcibly urge the first and second parts together at the contacting surface. Rotation of the spindle is stopped at a specific determined angular orientation of the first part relative to the second part while continuing to forcibly urge the parts together to allow cooling and fused solidification of the contacting surfaces.

1. A method of friction welding first and second parts together having a specific axial orientation relative to each other in which said first part is mounted to a spindle for axial rotation said second part is mounted to a non-rotatable holder moveable toward said spindle along the axis of rotation of said first part, comprising the steps:
 a. causing said spindle and mounted first part to be rotated at a desirable speed while determining the angular axial orientation of said first part relative to said second part at any specific time,    b. moving said holder toward said spindle to bring said second part into frictional contact with said first part at a selected one said specific time to cause heating of said first and second parts and the melting of the respective contacting surfaces thereof,    c. then decreasing the speed of rotation of said spindle and mounted first part and simultaneously moving said holder towards said spindle to forcibly urge said first and second parts together at said contacting surfaces, and    d. stopping rotation of said spindle and mounted first part at a specific determined angular axial orientation of said first part relative to said second part while still forcibly urging said first and second parts together to allow cooling and fused solidification of said contacting surfaces.    
     
     
       2. The method of  claim 1  wherein step b includes bringing said first and second parts into frictional contact at a first pressure force with the combined axial length of said first and second parts being reduced a specific distance followed by a second pressure force greater than said first pressure force with the combined axial length of said first and second parts being further reduced a second specific distance while maintaining said first desirable speed. 
     
     
       3. The method of  claim 2  wherein step c also includes applying a third pressure force greater than said second pressure force to said first and second parts with the combined axial length of said first and second parts being reduced a third specific distance. 
     
     
       4. The method of  claim 3  including monitoring the angular axial orientation of said first part relative to said second part during steps a, b, c, and d. 
     
     
       5. The method of  claim 4  wherein step d includes applying a forge force to said first and second parts for a specific dwell time. 
     
     
       6. The method of  claim 1  including determining responsive to one or more material characteristics of said first and second parts said desirable speed, said one specific time, and amount of force utilized to so force said first and second parts together during rotation of said spindle and mounted first part. 
     
     
       7. The method of  claim 1  including monitoring said angular axial orientation of said second part of said first and second parts relative to each other and adjusting the rotational speed of said spindle to arrive at said specific determining angular axial orientation of said first part relative to said second part. 
     
     
       8. The method of  claim 1  including adjusting the rotational speed of said spindle during steps b to effect said melting of the contacting surfaces of said first and second parts. 
     
     
       9. An apparatus for controlling a friction welding machine, comprising:
   a motion controller operatively coupled to a motor for rotating a spindle;        a position sensor operatively coupled to the motion controller and the spindle, the position sensor arranged to determine an actual spindle position and further arranged to communicate the actual spindle position to the motion controller;        a computing device operatively coupled to the motion controller, the computing device arranged to calculate a set of output parameters from a set of input parameters and to generate a spindle profile based on the set of output parameters, the computing device further arranged to communicate the spindle profile to the motion controller, the spindle profile indicative of a desired spindle position and a desired spindle angular velocity;        the motion controller further arranged to measure a first deviation between the actual spindle position and the desired spindle position, the first deviation measured at a first time point on the spindle profile, the motion controller further arranged to adjust an angular velocity of the spindle to reduce a second deviation measured at a second time point.     
     
     
       10. The apparatus of  claim 9 , wherein the set of input parameters includes at least one of a material constant, a geometric constant, a desired final spindle position, a material type, a workpiece weight, a workpiece geometric property, a first workpiece length, a second workpiece length, and a desired finished workpiece length. 
     
     
       11. The apparatus of  claim 9 , wherein the output parameters include at least one of the desired spindle position, a desired total number of spindle rotations, a desired number of spindle acceleration rotations, a desired number of spindle pre- heat rotations, a desired number of spindle heating rotations, an actual number of spindle forge rotations, a desired spindle rotational speed, a desired time at a pre - heat spindle force level, a desired pre - heat distance, a desired heat distance, a required time at a forge force level, a desired forge distance, a rotational moment of inertia, a target upset distance, a desired pre - heat force level, a desired heat force level, and a desired forge force level.   
     
     
       12. The apparatus of  claim 9 , wherein the computing device is arranged to compare the desired spindle position to the actual spindle position and to calculate a deviation, the computing device further arranged to compare the deviation to a threshold deviation and to calculate a replacement spindle profile if the deviation exceeds the threshold deviation. 
     
     
       13. The apparatus of  claim 9 , wherein the spindle profile includes an acceleration phase, a pre- heat phase, a heating phase, and a forge phase.   
     
     
       14. The apparatus of  claim 9 , wherein the computing device is further programmed to send a force command to an actuator, wherein the actuator is arranged to move a tailstock a desired distance relative to the spindle based on the force command. 
     
     
       15. The apparatus of  claim 14 , wherein the force command is indicative of a desired force level applied to the workpiece. 
     
     
       16. The apparatus of  claim 14 , wherein the computing device is arranged to calculate a force profile indicative of a desired force applied by the actuator over a force application time period. 
     
     
       17. The apparatus of  claim 16 , wherein the force profile includes a pre- heat force phase, a heat force phase, and a forge force phase.   
     
     
       18. The apparatus of  claim 16 , wherein the force profile is indicative of a desired travel distance of the tailstock. 
     
     
       19. The apparatus of  claim 18 , wherein the force profile includes a pre- heat distance, a heat distance, a forge distance, and a target upset distance.   
     
     
       20. The apparatus of  claim 14 , wherein the computing device is arranged to measure an actual travel distance of the actuator. 
     
     
       21. The apparatus of  claim 20 , wherein the computing device is arranged to measure a deviation between the actual travel distance and a desired travel distance, and further arranged to determine whether the deviation is greater than a threshold deviation. 
     
     
       22. The apparatus of  claim 16 , wherein the computing device is arranged to change the force profile in response to changes in the spindle profile. 
     
     
       23. The apparatus of  claim 14 , wherein the computing device is arranged to calculate a new spindle profile in response to changes in the set of input parameters, and is further arranged to change the force command in response to calculation of the new spindle profile. 
     
     
       24. The apparatus of  claim 9 , wherein the spindle profile includes an acceleration phase and a forge phase. 
     
     
       25. The apparatus of  claim 16 , wherein the force profile includes a single forge phase. 
     
     
       26. The apparatus of  claim 14 , wherein the motor is arranged to apply a reduced force to the spindle. 
     
     
       27. The apparatus of  claim 26 , wherein the motor is arranged to apply a force only when the spindle profile requires acceleration of the spindle. 
     
     
       28. The apparatus of  claim 27 , wherein the computing device is arranged to calculate an actual spindle angular velocity of the spindle based on the spindle position over time, the computing device further arranged to calculate a replacement spindle profile when the actual angular velocity falls below the desired spindle angular velocity by a predetermined threshold. 
     
     
       29. The apparatus of  claim 28 , wherein the computing device is arranged to control the spindle position and spindle angular velocity by adjusting the force command and wherein the motor is arranged to apply a reduced driving force. 
     
     
       30. A control loop for use on an angular orientation control system of a friction welder, the control loop comprising:
   a motion controller operatively coupled to a computing device;        a power amplifier circuit coupled to the motion controller;        a rotatable spindle driven by a motor, the motor operatively coupled to the power amplifier;        a tachometer arranged to determine the rotational speed of at least one of the motor and the spindle;        a position sensor operatively coupled to the spindle and the motion controller and arranged to determine the rotational position of the spindle;        the motion controller arranged to:      receive a command set indicating at least one of a desired spindle speed and a desired spindle angular position;        receive a signal from the position sensor indicating an actual spindle angular position; and        send a motion command to the power amplifier circuit, the motion command indicative of a speed change based on the desired spindle speed and the difference between the desired spindle angular position and the actual spindle angular position;          and        wherein the power amplifier circuit is arranged to adjust the motor based on the motion command and the actual spindle speed.     
     
     
       31. The system of  claim 30 , wherein the power amplifier circuit is arranged to:
   receive a motion command from the motion controller indicative of the desired angular velocity of the spindle;        compare the actual spindle angular velocity to the desired spindle angular velocity at a specific time point and generate a difference signal;        wherein the difference signal is amplified and sent to the motor.     
     
     
       32. The system of  claim 30 , wherein the computing device is arranged to generate the command set. 
     
     
       33. The system of  claim 30 , wherein the motion controller is arranged to send a status signal to the computing device indicative of a difference signal. 
     
     
       34. The system of  claim 33 , wherein the computing device is arranged to calculate a new command set when the difference signal exceeds a threshold. 
     
     
       35. The system of  claim 30 , wherein the tachometer is coupled to the power amplifier. 
     
     
       36. The system of  claim 30 , wherein the motor controller is a proportional- integral - derivative controller.   
     
     
       37. An apparatus for controlling a friction welding machine, the friction welding machine including a rotatable spindle and a non- rotatable tailstock and further comprising:      a motor for rotating a spindle, the motor arranged to engage the spindle;        a motion controller operatively coupled to a motor, the motion controller arranged to adjust an angular velocity of the spindle;        a computing device operatively coupled to the motion controller;        a position sensor operatively coupled to the spindle and at least one of the motion controller and the computing device, the position sensor arranged to determine an actual spindle position and further arranged to communicate the actual spindle position to the at least one of the motion controller and the computing device; and        an actuator operatively coupled to the computing device, the actuator arranged to apply a force to the tailstock and thereby move the tailstock relative to the spindle;        wherein the computing device is arranged to calculate a set of output parameters from a set of input parameters and to generate a spindle profile and a force profile based on the set of output parameters, the computing device further arranged to communicate a portion of the spindle profile to the motion controller and arranged to communicate the force profile to the actuator, the force profile indicative of the force applied by the actuator.     
     
     
       38. The apparatus of  claim 37 , wherein the spindle profile is indicative of at least one of a desired spindle angular velocity and a desired spindle position at a point in time. 
     
     
       39. The apparatus of  claim 37 , wherein the force profile is indicative of a force command at a point in time. 
     
     
       40. The apparatus of  claim 39 , wherein the force command is indicative of at least one of a desired force applied to the tailstock and a desired travel distance of the tailstock. 
     
     
       41. The apparatus of  claim 40 , wherein the computing device is arranged to measure a first deviation between the actual spindle position and the desired spindle position, the first deviation measured at a first time point on the spindle profile, the computing device further arranged to adjust the force command to reduce a second deviation measured at a second time point. 
     
     
       42. The apparatus of  claim 37 , wherein the computing device incorporates a proportional- integral - derivative controller.   
     
     
       43. The apparatus of  claim 37 , wherein the motion controller is integrated with the computing device. 
     
     
       44. The apparatus of  claim 37 , wherein the computing device is arranged to measure a deviation between the actual spindle position and the desired spindle position, the deviation measured at a first time point on the spindle profile, the computing device further arranged to calculate a new spindle profile if the deviation exceeds the threshold deviation. 
     
     
       45. The apparatus of  claim 44 , wherein the computing device is arranged to change the force profile in response to a change in the spindle profile. 
     
     
       46. The apparatus of  claim 37 , wherein the motor is arranged to apply a reduced driving force to the spindle once a predetermined angular velocity is achieved. 
     
     
       47. The apparatus of  claim 46 , wherein the computing device generates a new spindle profile when the actual angular velocity falls below the desired angular velocity by a predetermined threshold, the new spindle profile achieving the same final angular position as the previous spindle profile. 
     
     
       48. The apparatus of  claim 47 , wherein the computing device is arranged to decrease the actual spindle angular velocity to match the desired spindle angular velocity of the new profile curve by increasing the force of the actuator. 
     
     
       49. A method of using a friction welding machine to weld a pair of workpieces together at a desired final angular orientation relative to each other, the friction welding machine including a rotatable spindle and a non- rotatable tailstock, the method comprising the steps of:      calculating a set of weld parameters used to control the friction welding machine, the set of weld parameters including a desired spindle position;        mounting a first one of the pair of workpieces to the rotatable spindle and a second one of the pair of workpieces to the non - rotatable tailstock;        rotating the rotatable spindle;        applying a force to press the pair of workpieces together;        measuring at least one of an actual spindle speed and an actual spindle position to produce a measurement;        comparing the measurement with at least one of the desired spindle speed and desired spindle position;        adjusting the applied force so that the actual spindle position is substantially similar to the desired spindle position.