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.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This is a continuation of application Ser. No. 60 / 038,332 filed Feb. 27, 1997.[0002]The present invention relates generally to a control system for use on friction welding machines for controlling the final angular orientation of two workpieces relative to each other that have been welded together using the friction welding process.[0003]This application is a continuation of U.S. Pat. No. RE 39,019 filed Jan. 12, 2001, which is a reissue application of U.S. Pat. No. 5,858,142 filed Dec. 9, 1997 as U.S. patent application Ser. No. 08 / 987,493 which claims priority under 35 U.S.C. §119(e) from U.S. Provisional Application Ser. No. 60 / 038,332 filed Feb. 27, 1997. The above-identified applications are incorporated herein by reference in their entirety.<?insert-end id="INS-S-00001" ?>APPENDIX[0004]A software computer program forming an appendix consisting of 5 pages is included as part of the specification.IDENTIFICATION OF COPYRIGHT[0005]...

AI Technical Summary

Benefits of technology

"The present invention is a control system for friction welders that allows two workpieces to be welded together with greater precision and accuracy than previous methods. The system constantly monitors the angular orientation of the spindle at any given point in time and compares it with a predetermined desired spindle orientation. The computer calculates the desired orientation of the rotating spindle at any given moment during the weld process, including during the acceleration phase, the burn-off and weld phases, and through the deceleration phase until the spindle stops at the predetermined desired final angular orientation. The motion controller constantly compares the actual spindle orientation with the desired spindle orientation and makes the necessary corrections to ensure that the actual orientation conforms to the desired orientation. The control system employs a proportional-integral-derivative controller (“PID controller”) which allows for very quick responses to changes in friction between the two workpieces as they heat up during the weld process. The system can thus precisely control the angular orientation of the rotating spindle and the speed of the drive motor. The technical effects of the invention are improved precision and accuracy in friction welding, as well as greater responsiveness to changes in friction between the workpieces."

Problems solved by technology

Inertia friction welding has a number of inherent drawbacks which makes it unsuitable for many applications.

First, the flywheel bearings gradually heat up, which depletes the available kinetic energy because energy is lost through increased friction.

Second, due to the very high forge pressure required, inertia welding is unsuitable for thin walled tubes and many soft metals, such as aluminum.

In general, the quality and uniformity of inertia friction welds are hard to control.

Unfortunately, the final orientation of the rotating workpiece relative to the stationary workpiece is not easily controlled.

For example, the yoke at one end of an automotive drive shaft must be perpendicular to the yoke at the other end of the drive shaft; otherwise, the drive line components will be prone to premature failure.

Usually however, due to variations in the braking mechanism and other variables, the deceleration of the spindle is not uniform.

Thus the rate of deceleration, as well as the final angular position of the rotating workpiece, is relatively uncontrolled.

Unfortunately, in each instance the spindle has slowed significantly and the weld has already begun to cool and the material has begun to harden.

Any subsequent accelerations and rotation of the spindle cause microfractures in the crystal structure of the material, resulting in a lower quality, high risk weld.

Furthermore, the defined braking method is not accurate enough for many applications.

In general, the defined braking method is unsuitable for applications in which the final angular orientation is critical and is also unsuitable for many aluminum welds, aircraft quality welds, air bag welds and other safety related welds.

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