950 Palladium: Laser Welding Techniques

According to Frank McAllister, the quantity of individual pieces of jewelry made from 950 palladium has surpassed the same for platinum products in the recent months. McAllister, CEO of the Stillwater Mining Co. calculated this based upon the number of ounces used globally for each alloy.

It won't be long before light, bright and white 950 palladium products find their way into your store, either as merchandise from your customers' jewelry taken in for service or alteration or work required to customize 950 palladium jewelry from your own inventory.

The equipment settings and technical procedures for laser welding 950 palladium products differ from those specified for products made from platinum. This installment features research results and techniques used for successful laser welding of 950 palladium products in the following three most requested bench tasks:

1. Filling voids and pits
2. Minor assembly
3. Ring sizing

Laser Welding 950 Palladium

Brenda Warburton, Austin & Warburton in Ann Arbor, MI 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. For this research, Warburton used a Rofin StarWeld Laser machine with pulse forming capabilities. It is 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 affect 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 950Pd. Further, they appear in milled, machined or die struck stock products. To repair these irregularities with a laser, Warburton selected 2 wax models from her design collection and had them cast by Hoover & Strong using their TruPd, a 950 palladium alloy. In this image, Warburton uses 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 ms, 1.3HZ with a beam or focus of 5 to 15. (The variables depend upon the size and depth of the void.)
	99% pure argon was used.The void in the ring was hit with a few pulses of energy from the laser to open and shape it. 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. Photo by Craig Warburton
	Tip: When filling voids and pits with a laser, start by directing pulses of energy directly into the void. This will melt the bottom, exposing fresh metal from which to build upon. Photo by Craig Warburton

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 3 partial bezels and a jump ring. 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 ms, 1.3HZ with a beam or focus of 5 to 15. (The variables depend upon the size of the components being joined.)

99% pure argon was used. When tacking only, it is not necessary to use weld-filling wire. This procedure included pulse shaping.

Tip: According to resources at the Rofin website, laser welding success with any alloy depends both on material properties like temperature dependent reflectivity, heat conductivity or viscosity as well as specific laser parameters like pulse energy, spot diameter or 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 over-heating of 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 6 incremental steps.

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

Ring Sizing

In the case where 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 this Tanzanite and diamond 950 palladium ring to achieve the best results for laser welding. The equipment settings were 290 volts, 10ms, 1.3HZ with a beam or focus of 15. 99% pure argon was used with its dispenser about 1 centimeter away from ring. A "v" shaped joint was filed and 30 gauge TruPd dead soft wire was used for filling. Pulse shaping techniques were used. The ring was polished and inspected under 10X magnification. There were no visible cracks, pits or other irregularities found. Tip: The MS setting was set high to spread the energy throughout the metal so it would not get excessively hot in a small concentrated area making 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.

For sizing rings, it's best to fill an open "v" shaped 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.

Research is continuing regarding the best options for using the laser with 950 Pd products. Watch this article series for continued information.