The PUK Welder
The PUK Welder
The German pulse-arc bench welder that displaced the torch in many fine-jewellery workshops
The PUK welder is the trade name for the pulse-arc micro-welding system manufactured by Lampert Werktechnik of Werneck, Germany, and it has become the de facto generic term for benchtop pulse-arc welding equipment in the international jewellery industry. The system delivers precisely controlled, short-duration high-energy electrical pulses through a tungsten electrode, producing a localised fusion weld in precious metal without the use of solder, flux, or filler. It has reshaped the way fine-jewellery workshops handle setting repairs, sizing, and assembly of pieces with heat-sensitive gemstones — work that previously required either dis-assembly and re-setting around a torch, or the careful application of a laser welder.
Operating principle
A PUK weld is generated by passing a high-current electrical pulse through a tungsten electrode held a fraction of a millimetre above the work surface, with the workpiece grounded. The resulting electric arc melts a small volume of metal directly beneath the electrode tip, and surface tension and rapid cooling fuse the metal into a homogeneous weld bead. The pulse duration, current, and energy are controlled through a programmable bench unit, with settings that the operator selects according to the metal being welded — yellow gold, white gold, platinum, palladium, sterling silver, or various alloys — and the work being done. The argon shielding gas delivered through the electrode handpiece prevents oxidation of the molten metal.
Compared to a goldsmith's torch, the PUK delivers heat over an extremely short duration (milliseconds rather than seconds) and over a small area (sub-millimetre rather than millimetre to centimetre), with very limited heat conduction into surrounding metal. This is the property that makes the system useful for repairs near heat-sensitive gemstones — emerald, opal, tanzanite, peridot, organic materials such as pearl, ivory, and amber, and heat-treated corundum, all of which can be damaged by the sustained heat of torch soldering even with shielding compounds.
Comparison with laser welding
The PUK is one of two principal micro-welding technologies in modern fine-jewellery use, the other being laser welding (typically Nd:YAG). Both deliver localised heat without solder, but they differ in important practical respects. Laser welders can deliver smaller spot sizes and even more localised heat, and they work better on highly reflective metals such as silver and platinum at certain wavelengths. They are, however, considerably more expensive — often four to ten times the price of a PUK system — and require greater operator training in safe use. The PUK has become the standard benchtop choice for small to medium jewellery workshops worldwide, while laser welders remain more common in high-volume production settings, in stone-setting houses serving the larger ateliers, and in certain specialist disciplines such as watch case repair.
Applications in the workshop
Standard PUK applications include sizing rings without removing settings, repairing broken prongs in claw-set rings, reattaching findings such as bails and jump rings, building up worn metal at high-wear points, repairing chains, and joining dissimilar metals where a soldered joint would be problematic. The system is also used for tack-welding components in fabrication, allowing the smith to fix parts in position before final soldering, and for cosmetic repairs to laser-weld scars and porosity defects in cast pieces.
The system is widely used in repair work on antique, period, and inherited pieces — Edwardian, Art Nouveau, and Art Deco jewellery, where original solder joints can be fragile and original gemstones may have been heat-treated using methods that make them more susceptible to thermal damage than modern equivalents. PUK repairs allow such pieces to be returned to wearable condition without the trauma of full dis-assembly.
Limitations
The PUK is not a replacement for all torch and laser work. Welds are typically small in volume per pulse, so building up larger areas requires multiple passes and skilled hand control. The cosmetic finish of a PUK weld is harder than the surrounding metal, which can cause polishing inconsistencies; experienced operators learn to anneal and finish PUK joints with techniques specific to the system. The system also requires regular maintenance of the tungsten electrode, the gas supply, and the bench unit's electrical components.
In the trade
For Skyjems and the broader fine-jewellery and bespoke trade, the PUK welder has become standard bench equipment in any workshop handling repairs and modifications to pieces with heat-sensitive Mogok ruby, Madagascan or Sri Lankan sapphire, Colombian emerald, opal, pearl, or other vulnerable gemstones in situ. The system has effectively eliminated a previous category of repair refusal, where a piece with an irreplaceable stone could not safely be sized or repaired by torch. The Lampert PUK is the dominant brand by market share; competing systems include the Orion pulse-arc series and various Asian-made alternatives. Pricing for a current-generation PUK bench unit is in the low to mid four-figure range, placing it within reach of independent jewellers and small workshops worldwide.