Ultrasonic Energy Welds Beryllium Copper Spring to Copper Frame: Part 2 Ultrasonic metal welding provides a sound solution to a productionproblem with superior performance, improved throughput and reducedmaintenance. W.L. Gore & Associates, Inc. improves its competitiveadvantage by reducing 'Cost of Goods Sold'
The Challenge (An Opportunity for Success)
W.L. Gore & Associates, Inc. (Gore) had been using resistance welding for years on their automated assembly system to join a gold plated BeCu spring to a Cu frame. "Why not? everybody does," stated Gore Machinist Engineer, Jim Nahrgang, "You become accustomed to the weld splatter and system maintenance."
Charged with the goal of improving assembly throughput, Jim began to look at alternative manufacturing processes. He identified ultrasonic metal welding as a potential solution and submitted component material to AmTech for a feasibility evaluation. Immediately identified as an excellent application for ultrasonic metal welding, a 40 kHz ultrasonic welding system was recommended for this small, delicate application - (See Figure 4).
The Solution (Knowledge is Power)
High quality, low cost, tooling was designed for the application and, along with an Intelligent Controller, the production line was quickly equipped and welding assemblies for evaluation. Working with an ultrasonic welding system on an "off line" station allowed side by side comparisons to be made. Upon completion of testing it was determined that the ultrasonic metal welding system provided the superior, high quality results that Gore requires.
The Next Step (A Continuing Partnership)
The next step was to integrate the welder into the automated assembly line. The first challenge, due to the machine design, was to mount the welder in the small restrictive area available. The second, due to the design of the components, was that the weld actuator be able to advance in and out of the weld zone. By mounting the ultrasonic actuator on a precision slide, with switches, Gore was able to move and monitor the weld head's position. In addition, a low cost, four lobe, replaceable welding tip was designed for the application. When reviewing the tip design Jim commented, "I may never have to replace this tip, . . ." (the four lobe tip was designed with approximately eight (8) weld areas per side [8 x 4 = 32 working surfaces].
Quality Results (A Win-Win Success)
By using the system's 'weld-to-energy' mode, differences in the component material's physical properties and or tooling wear does not affect the quality of the joining process. As these factors change the Intelligent Controller ensures the proper amount of energy goes into the work creating the optimum weld joint. A power feedback signal is utilized to monitor the amount of power (P), in watts, required to keep the ultrasonic stack in motion during the weld cycle. In doing so a power curve is generated over time (T) in seconds. The area under the power curve is integrated and energy, in joules, calculated (watts x time = joules). Once weld parameters are determined, weld power and weld time become independent variables producing the joules necessary for the application - (See Figure 5). This illustration shows three possible power and time curves. 1) Clean parts, with normal surface condition variations create a quick rise to desired peak power and a complete weld within acceptable time limits. 2) Unacptably dirty parts or worn tooling will draw low peak power, extend weld time, and trigger an alarm. 3) A missing part will not draw significant welding power and will also result in an alarm condition.
Figure 5 - Typical power curves.
Excerpted from "Ultrasonic Energy Welds Copper to Aluminum", Welding Journal, January 1997
Charged with the goal of improving assembly throughput, Jim began to look at alternative manufacturing processes. He identified ultrasonic metal welding as a potential solution and submitted component material to AmTech for a feasibility evaluation. Immediately identified as an excellent application for ultrasonic metal welding, a 40 kHz ultrasonic welding system was recommended for this small, delicate application - (See Figure 4). 
