Advanced Upset/Length Control: Torque Modulation of Inertia and Direct Drive Friction Welds

MTI has developed a revolutionary control technique that significantly reduces the variability in loss of length (upset) in both Inertia and Direct Drive Friction Welds; we call this Torque Modulation (patent pending). Prior to this development, upset/length control was only possible in Direct Drive Friction Welding. In the Direct Drive weld cycle, upset/welded length is typically controlled by the transition from second friction phase to forge/brake phase. However, once the forge/brake phase is initiated, upset occurs in an uncontrolled and unpredictable manner leading to variations in the final upset and/or final part length. In the Inertia Welding process, the final upset was the result of careful selection of starting parameters with even more variation.

In traditional Inertia and Direct Drive Friction Weld cycles, there is no feedback of the actual upset archived and, thus, no dynamic control of the process to account for the unpredictable variations in metallurgy, part geometry, and other factors that affect final upset. Torque Modulation monitors the actual upset that occurs during the deceleration phase of the friction weld cycle (both Inertia and Direct Drive) and applies minor adjustments to spindle drive motor torque to adjust for variations in upset formation.

Torque Modulation uses a profile, actual weld data from a good weld (same parts and weld cycle parameters), to reproduce the characteristics of deceleration and upset formation. The goal of Torque Modulation is to make torque adjustments during the deceleration of the spindle in order to precisely duplicate the upset defined in the profile weld. MTI has applied for a patent for this technique.

Upset and Final Part Length control in Direct Drive Friction Welds has been available for some time, but it has always had limitations due to incoming part variations. Now, MTI is able to offer a technique that not only is able to control upset during an Inertia Weld cycle, but is also a drastic improvement over the traditional Direct Drive Weld cycle. Since we are reproducing the natural upset formation of an Inertia Weld, there are no negative effects to weld quality. In fact, any application that can be welded with the Inertia Welding process can now be accomplished with length control.

Torque Modulation can also be applied to the Direct Drive process. Therefore, MTI is able to offer friction welding machines that are able to control upset with either type of weld cycle which allows MTI to offer the customer the ability to choose the type of weld cycle that best fits the application.

Torque Modulation is robust enough that it can overcome incoming material and part length variations that have plagued the Direct Drive length control ability of yesterday. In fact, this technique allows friction welding machines to produce length tolerances that are approaching finished length tolerances.

Advantages of Length / Upset control with Torque Modulation

• pset Control in Inertia welds that surpasses traditional Direct Drive capability
• Improved Upset Control and final welded part length control even in Direct Drive welds
• Either friction welding process can be used to control leg nth/upset