Professional Jeweler Archive: Back to Basics: Tack Welding vs. Pulse-Arc Welding

May 2005

Bench | Welding Technologies


Back to Basics: Tack Welding vs. Pulse-Arc Welding

Knowing the differences between tack and pulse-arc welding technologies contributes to higher levels of quality and proficiency for your shop

By Mark B. Mann


Individuals new to tack- and pulse-arc welding often are confused about differences in the technologies used at the jeweler’s bench and wonder why efficient, deformation-free tack welding can’t be done using a pulse-arc-welder. This article reviews the differences between the two technologies and the specific equipment required for each.

TACK WELDING

Equipment

1. A tack weld is a temporary working weld at a joint between two parts. Its holding capability is medium to low. A tack weld is made using a tack-welding unit (pictured at right with optional accessories).

Creating a Circuit

2. The first step in tack welding is to create a circuit. To do this, use tool leads attached to the positive and negative terminals on the tack-welding unit. In this example, the tweezers are attached to the negative terminal and the pliers are attached to the positive terminal.

Discharging Energy Through the Circuit

3. The tack welder discharges electrical energy through the circuit when you depress the foot pedal. As the energy flows through the circuit, the tack weld takes place at the point of greatest resistance (where two pieces meeting have the smallest amount of surface contact). In this example a second head is being tacked to yellow gold earrings.
The Tacked Result

4. The parts are held together temporarily, and there is no surface deformation. For permanent joining, this process is followed by torch soldering, pulse-arc welding or laser welding. Soldering of all units simultaneously is possible when tack welding.

PULSE-ARC WELDING

Equipment

1. A pulse-arc weld creates a permanent joint between components, resulting from an instantaneous pulse of energy from the welder. Several pulses of energy may be required to complete a weld joint. ABI makes two pulse-arc welders, the one featured and the Mini Pulse III.
Creating the Set-up

2. To pulse-arc weld, you first must ground the workpiece by making contact via the negative terminal using one of the wired tools (such as pliers, contact pad, tweezers or another lead). The pulse-arc-welding pencil (with one of its several sized welding electrode tips) is then attached to the positive pole. In this example, the alligator clip provides the ground and is attached to the negative lead; the pulse-arc-welding pencil is attached to the positive lead.
Discharging Energy

3. You discharge electrical energy when you depress the foot pedal. The ABI unit uses high-frequency, self-ignition technology or a forced arc so the permanent weld takes place immediately below the electrode. Several pulses of energy may be required to complete the weld joint. In this example, 14k gold wire is used to fill the permanently welded joint.
The Pulsed Result

4. The parts are permanently held together. There’s some surface deformation requiring minor sanding and finishing. In this example, the cultured pearls and heat-sensitive center gem didn’t need to be removed because the energy discharge is instantaneous and localized to the joint.

For tacking components before soldering or permanent welding, the ABI Tack II provides a superior result without deformation of the surface of the piece. If you’re not satisfied with the alignment of the components after tacking, it’s simple and non-destructive to disassemble the tacked parts and start over.

For tacking components, a pulse-arc welder provides a less-than-desirable result because there will be deformation on the jewelry, requiring clean-up. If the components require realignment, they are difficult to break apart and may require reshaping because of surface deformation.

For permanent joining of components or for filling porosity, the pulse-arc welder is superior. It minimizes possible gemstone damage when a heat-sensitive gem is present and provides a quick permanent weld joint.

ABI offers two types of welding units: one for tack welding and the other for permanent pulse-arc welding. Because of demand, ABI has designed a new unit called the ABI PowerTower™ that contains tack- and pulse-arc-welding technology capable of performing tack, pulse, spot and fusion welding. The new The PowerTower™ has been designed and tested and is going into production.

This installment was sponsored by ABI, Cranston, RI. For information on ABI equipment and procedures or for a list of distributors, call Janet Kirk at (888) 494-2663.

Photographs by Mark B. Mann
Visual Communications Inc. © 2005

This information is provided without warranty, either expressed or implied. The procedures can be harmful if not executed properly and are undertaken at the reader’s own risk. The author and publisher are not responsible for injuries, losses or other damages that may result from use of this information.

Copyright © 2005 by Bond Communications