APPLIANCE PRODUCTION HIGHLIGHTS
©DANA CHASE PUBL. • APR '93

The process of charging compressors with refrigerant is typically a labor intensive, unclean process that seems inconsistent with automated production lines typical of the appliance industry. Appliance producers, however, are beginning to take notice of the benefits of ultrasonic metal welding systems.

The introduction of ultrasonic welding to the compressor line at Armstrong Air Conditioning, Inc., streamlined the process and provided various production, ergonomic, and environmental benefits.

A typical refrigerant charging procedure involves installation of a Hansen valve, which allows air and moisture to be removed from the system and refrigerant to Be installed. Producers usually crimp the copper fill tubes, using a vise-grip or similar device, so the Hansen valve can he removed after the refrigerant is installed. Subsequently, the copper tube is cut and brazed to permanently seal it.

The Stapla Ultrasonics Tube Sealer installed at Armstrong is designed to crimp, weld, and cut the copper process tube lines in a single operation, enabling the company to reduce its direct labor cost 63 percent.

Other improvements were realized in ergonomic areas, with the elimination of vice grips and side cutters, and in environmental areas associated with the elimination of the brazing process. Cost savings were also generated from reduced material and natural gas usage at the brazing station.

Ultrasonic welding is actually a cold-phase, friction joining/bonding technique. The process subjects the surfaces to he joined to high frequency mechanical oscillations while under controlled static force. As a result, molecules of both surfaces begin to intermingle and a lasting bond is achieved. So complete is the metallurgical bond that a photo micrograph of the cross-section barely reveals the weld line.

The Stapla system utilizes a microprocessor that monitors all of the process variables and, ultimately, weld quality. As a result, the OEM also reports that its leak rate has been reduced to less than one percent.

One appliance producer, performing burst tests on 1/4-in tubes sealed with a system from the supplier, found the seals withstood 5.100 psi on average.

Using ultrasonic welding to seal copper tubes required several tooling changes before acceptable tool life could he achieved.

Workers adapted quickly to the ultrasonic process and were supportive of the producer's effort to eliminate the crimp, cut, and braze methodology in favor of ultrasonic welding. Training of maintenance personnel enabled them to feel comfortable making tooling and set-up changes.

Ultrasonic welding provides manufactures with a cost-effective alternative to sealing copper tubes on refrigerant systems. The technology is proven and the productivity increases, combined with 100 percent quality assurance and fast payback, provide significant incentives for change.