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.