Comparative Analysis of Three Welding Systems

AJM Magazine asked me to perform a comparative analysis of three welding systems' performance in several different precious metal welding applications. I was to analyze the PUK 2 spot welder, which was developed by Lampert Tools USA Inc. and supplied to me by SEP Jewelry Tools of Chicago; the Mini Pulse III from Aelectronic Bonding Inc. (ABI) in Cranston, Rhode Island; and a laser welder. (I used my Starweld by Rofin-Baasel, which I purchased from Manufacturing Technologies in San Diego , but the results presented in this article are accurate for most laser welders used in the jewelry industry.)

AJM challenged me to decide which machine was best for various applications. But like our hero Kirk, I had to change the original rules of the assignment to accomplish my goal.

I had a Kobayashi Maru experience writing this article. Star Trek aficionados, or Trekkies (which I don't claim to be, really), will remember this as the conundrum offered to Starfleet Academy matriculate potentials — a double-bind situation with no clear or correct solution. Captain James T. Kirk managed to be the only cadet to outmaneuver the test by hacking into the test console and changing the rules…and I followed his example in my comparison of the practical application of three different welding tools for findings attachment, general assembly, and repair. Please allow me to beam up my results.

Photo by Gary Dawson

My initial attempt to determine which tool might be more useful for specific welding applications led me to the conclusion that, in many cases, one machine was not distinctly "the best" for performing an application. In fact, there are so many crossovers in the valuable use of these machines that it would be difficult to actually approach the topic just that way.

In addition, deciding which system is best for your shop depends on economic factors such as your overall cash flow, margin per unit, cost of labor versus that of the technology, time management, and training expenses. Therefore, I decided to explain the advantages and disadvantages of how each machine performs in specific applications, as well as provide the technical specifications available for each. It is my hope that this data will enable you to better weigh the pros and cons of each system and decide which is best for your needs.

The Technology

Of the three welding systems I tested, the PUK 2 and Mini Pulse III use similar pulse-arc technologies. An arc is formed between a non-consumable tungsten electrode and the metal being welded, forming a molten pool. If filler material is used, it is fed separately into the molten pool. The use of an argon shielding gas can considerably reduce oxidation and facilitates a smoother transfer of filler material.

This is very similar to GTAW (Gas Tungsten Arc Welding), which is often referred to as TIG (Tungsten Inert Gas) welding — the method of choice in steel fabrication shops where high quality precision welding is required. The biggest difference between the pulse-arc systems I tested and TIG welders is that the latter use a continuous arc, allowing for an uninterrupted seam as the electrode is moved across the weld interface. Pulse-arc welders do just what they say — pulse an arc in a burst of electrical energy.

Laser welders, on the other hand, use Nd:YAG laser beams generated by flash lamps. Although a laser welder's high pulse frequency may lead you to believe that it produces a continuous weld seam, it too is actually producing single, overlapping spot welds just like the pulse-arc welders, only much more rapidly.

Welding Applications

When the two pulse-arc welders arrived at my shop for testing, I could hardly wait to get started. Both were very easy to set up, and after a few weeks of research and preliminary testing, I was ready to begin comparing them. The following are the results of several applications tests.

1. Continuous Seam Weld: Installing a clasp on a bracelet and performing a dovetail sizing.

A semi-continuous seam can be achieved by any of these machines using overlapping spot welds, but it can be a tedious task if a long weld seam is re-quired. Speed is certainly an advantage in this application.

If multiple pulses are required to complete a job, a laser is the quickest tool for the task. Most can pulse up to 20 times per second — warp speed compared to the pulse-arc welders, which require a much stronger electrical pulse to create the welding arc and thus have a longer capacitor refresh rate. The Mini Pulse III has a faster refresh than the PUK 2, providing two pulses per second compared to one pulse per 1.7 seconds, respectively. Due to its slightly faster pulse rate, the Mini Pulse III may be a better choice than the PUK 2 for welding applications that require a continuous weld seam.

Interestingly, the incredibly rapid refresh rate achieved by the laser, which also allows for extremely fast metal build-up and overlay, considerably heats up the work piece. In my shop, we routinely use tweezers, pliers, or insulating gloves to hold objects that require multiple, high energy pulses. Occasionally, we have to put the piece down for a cool-off period before continuing the weld process, which can cost valuable shop time. We did not experience this problem with either of the pulse-arc welders, as the slower pulse rate prevents rapid heat-up in most components.

2. Welding in Tight Spots: Attaching a four-prong head to a freeform cluster ring.

One of the greatest advantages of the laser is its accessibility to just about anywhere on a piece. Basically, if you can see it, you can weld it with a laser. Operating through a high power binocular microscope, you can place the crosshairs of the laser in the most recessed and hidden areas of a piece. This allows for extremely tricky assembly and repairs, such as the project shown here in which I am attaching the base of a four-prong head to a freeform cluster ring.

Unlike laser welders, both pulse-arc welders rely on a handpiece with a tungsten electrode and a separate ground to deliver the arc. Both have some limitation in reach due to electrode length, but the PUK 2 offers some advantage in that it uses an extremely thin, exposed electrode. You touch the electrode to the area to be joined, and then the electrode is electronically retracted by the handpiece, drawing the arc in an automatic cycle. The thin electrode allows for very precise placement of the arc, enabling greater precision and control than the Mini Pulse III for fine detail work. One drawback to this system is the potential for tungsten contamination, since the electrode actually touches the work.

The Mini Pulse III differs because it uses a foot-pedal-activated system that shields the electrode in a ceramic collar. The unit comes with three electrode/collar tips. In each, the electrode is slightly recessed (about 1.5 mm) into the ceramic collar that, depending on the chosen electrode size, measures from 1.58 mm to 3.23 mm in diameter. Although the collar eliminates the potential for contamination by the electrode, it can preclude welding in extremely tight areas. To combat this problem in some circumstances, you can grind the collar into a specific shape to extend its reach, provided the recession of the electrode is maintained.

3. Attaching an earring post to a head.

Although attaching an earring post to a head is a quick and simple task with any of the three welding units tested here, you may want to stop and think twice before you pulse. Sometimes, old-fashioned soldering may be your best bet.

According to Bob Lynn of Lynn 's Jewelry in Ventura , California , a laser welder is one of the worst tools for this job. "The problem with a laser welder is it will partially anneal the post, so the post bends more easily right above the weld," he says.

Operator error or difficult alloys (nickel white golds, for example) can further complicate matters for laser welders or pulse-arc welders in this application. These systems can actually cause brittle welds that simply don't hold up well for such tiny attachments.

When installing earring posts, particularly on a production basis, other technologies may be better suited than those researched in this article. A fusion welder such as the Sparkie II manufactured by Triad Inc. in Charlton , Massachusetts , seems to be a very useful tool for this application. Small shops with limited production may want to stick to old-fashioned soldering for a solid weld.

According to Wayne Lenkeit, a Temecula, California-based Certified Master Bench Jeweler and owner of a PUK 2, a well-joined and filleted solder joint is best for this application. "A solder joint is extremely strong, relatively quick to do, and requires no clean up other than polishing," he says. "It's time-consuming to fillet such a joint with the PUK, and it's not very strong without the fillet.

"For applications where the torch can't be used, I make a post with a small pad on the end, and then weld the pad to the piece with the PUK," he adds. "The larger circumference of the pad provides for a greater weld area and hence a stronger joint."

4. Applications That Require a Particularly Steady Hand: Retipping prongs next to gemstones that are particularly sensitive to heat or a stray pulse.

Both pulse-arc machines I tested for this article provided a variety of grounding options, including a ground pad upon which the piece may rest during welding operations, as well as grounded tweezers and grounded pliers. The tweezers and pliers make both of these welders more flexible to use, but by virtue of its operational design, the PUK 2 requires a greater amount of operator skill in applications that mandate a particularly steady hand. As the electrode retracts away from the work piece, there is a tendency for the operator to push toward the piece. If the electrode hasn't properly retracted, there is a greater chance for electrode contamination or a poor weld. The PUK manufacturers acknowledge the tool's sensitivity to touch in their instructions for use, which emphasize a braced, steady hand position: "always support both hands on the base (work table), as trembling hands will distort the parameter of the device."

The Mini Pulse instructions condone freehand work. In fact, the recessed electrode and foot-pedal operation allow you to simply rest the ceramic collar against the work piece and activate the pulse, making it somewhat easier to work in this fashion.

Once again, the laser provides for ultimate positioning options, as it is foot-pedal-operated, and the piece can be manipulated with both hands.

Conclusions

Ultimately, I think it is fair to say that a laser welder is more useful and convenient for a variety of applications than the pulse-arc systems I tested in this article. But is this surprising for a technology that costs about 10 times more?

That said, the pulse-arc systems can hold their own in many welding applications, and, for the price, may be an attractive alternative. It is not difficult to visualize that production assembly of relatively accessible parts, such as bracelet hinges or findings, might be more easily and economically addressed by the rapid refresh rate of the ABI Mini Pulse III machine. In this scenario, I believe the ABI machine would excel and provide a fantastic cost-to-weld ratio. Conversely, if you need extremely precise weld control in areas that are consistently more difficult to reach, such as those found in certain custom fabrication jobs, and you are not overly concerned with pulse refresh rate, the PUK 2 might make more sense for you.

While there are advantages and disadvantages to all three systems, all have proven themselves as valuable additions to the jewelry maker's tool repertoire. This is a pleasant contrast to an article I wrote for AJM nearly 10 years ago, in which I mentioned that the jewelry industry is "steeped in tradition." A lot has changed since then. Like Captain Kirk and his Starship Enterprise, we are now "boldly going where no man has gone before" — into some very cool areas of tool innovation.