950 Palladium Laser-Welding Tips and Techniques

According to Frank McAllister, chief executive officer of Stillwater Mining Co., the quantity of individual pieces of jewelry made with 950 palladium recently surpassed that of platinum products. McAllister calculated this based on the number of ounces used globally for each alloy. Retailers can expect to see 950 palladium products in their stores, including their own inventory—which may need to be customized—as well as customers’ jewelry taken in for service or alteration.

The equipment settings and technical procedures for laser welding 950 palladium products differ from those specified for platinum products. This installment features research results and techniques used for successful laser welding of 950 palladium products in three bench tasks: filling voids and pits, minor assembly, and ring sizing.

Brenda Warburton, Austin & Warburton, Ann Arbor, Mich., conducted the research, and Hoover & Strong provided the examples for this overview. Related details for the research were provided by Tyler Teague of Jett Research and Stewart Grice of Hoover & Strong.

Warburton used a Rofin StarWeld Laser with pulse-forming capabilities for all three techniques (see Figure 1). It’s important to remember that laser-welding equipment varies by manufacturer, so the settings listed in this reference are specific to the equipment being used. Overall maintenance of equipment can also have an effect on the settings and final outcome.

FILLING VOIDS AND PITS

Voids and pits most often result during the casting process with all jewelry alloys, including 950 palladium. Further, they appear in milled, machined, or die-struck stock products. To repair these irregularities with a laser, Warburton selected two wax models from her design collection and had them cast by Hoover & Strong using their TruPd, a 950 palladium alloy. Fig- ure 2 shows Warburton using 30-gauge dead soft TruPd palladium wire to fill the voids. The following procedures were used to obtain the best results for laser weld/filling voids:

  • The equipment settings were 250 volts, 5 to 10 milliseconds, 1.3 hertz with a beam or focus of 5 to 15 (the variables depend on the size and depth of the void);

  • 99 percent pure argon was used;

  • To begin, the void in the ring was hit with a few pulses of energy from the laser to open and shape it. This technique melts the bottom, exposing fresh metal from which to build upon (Figures 3 and 4);

  • The tip of the wire was held in direct contact with the palladium piece, within the void, and a pulse of energy melted 950 palladium from the wire into the void;

  • Each void was overfilled with 950 palladium and then filed even with the surface of the ring for finishing.

MINOR ASSEMBLY

For assembly of palladium pieces, the most efficient manner was to tack the parts using a laser. This procedure was then followed by torch soldering to complete the process. In the example, the top portion of the earrings consists of three partial bezels and a jump ring (Figure 5). These pieces are tacked for temporary joining. The pieces are then checked for proper alignment and adjustments are made before the final arrangement is torch soldered. The following procedures were used to obtain the best results for laser tacking prior to torch soldering and final assembly:

  • The equipment settings were 250 volts, 5 to 10 milliseconds, 1.3 hertz with a beam or focus of 5 to 15 (the variables depend upon the size of the components being joined);

  • 99 percent pure argon was used;

  • When tacking only, it is not necessary to use weld-filling wire;

  • This procedure included pulse shaping.

Warburton prefers the binocular optics with her laser welder (Figure 6). At a glance, she can look up at the blue panel to determine the settings and review the related detail. For nonmagnified viewing of the actual piece, she can look down and see it though the amber-color work window.

  • Tip: According to resources at the Rofin Web site, laser-welding success with any alloy depends both on material properties like temperature-dependent reflectivity, heat conductivity, and viscosity as well as specific laser parameters like pulse energy, spot diameter, and temporal pulse intensity. Pulse shaping calls for a series of settings used in progressive pulses. Each setting factors both the duration of the pulse of energy and the total amount of energy used, for optimal control.

The pulse-shaping technique can be used to avoid overheating the material, because the series begins with high laser intensity and then incrementally reduces laser power once the melting point has been reached. Pulse shaping can also reduce cracking in the metal, which can occur during quick cooling of a weld, important for 950 palladium alloys.

Pulse shaping for 950 palladium alloys used for this research included six incremental steps:

Step # Pulse Dursation Total Energy
1 0% 90%
2 20% 100%
3 40% 100%
4 50% 70%
5 80% 30%
6 100% 20%

RING SIZING

For sizing rings, it’s best to fill an open V-shape seam. Some laser technicians use a double V while others start at the bottom with a closed seam and fill upward using 28- to 32-gauge dead soft palladium wire.

When heat-sensitive gemstones are part of the design, it is not always safe to size palladium rings with a torch. The following steps were taken in sizing a tanzanite and diamond 950 palladium ring (Figure 7) to achieve the best results for laser welding:

  • The equipment settings were 290 volts, 10 milliseconds, 1.3 hertz with a beam or focus of 15;

  • 99 percent pure argon was used with its dispenser about 1 centimeter away from the ring;

  • A V-shape joint was filed (Figure 8) and 30-gauge TruPd dead soft wire was used for filling;

  • Pulse-shaping techniques were used;

  • The ring was polished and inspected under 10× magnification. There were no visible cracks, pits, or other irregularities found.

  • Tip: The MS setting was high to spread the energy throughout the metal so it would not get excessively hot in a small concentrated area and make the metal brittle. Use of the pulse-shaping technique caused the metal to appear brighter, and it was more fluid. During the process, the ring became hot to hold. Warburton suggests using a dampened paper towel to avoid burning fingers.