New materials and torch shapes increase range of plasma cutting applications

Every new technology, from automobiles to televisions, goes through an evolutionary period where the design develops from the early, rudimentary concept to modern, refined, and user-focused. If you think back to your first computer or cell phone, it bore little resemblance to the advanced tablets and smart phones of today.

The torches found on today’s plasma cutting systems are no different. The first torches were squared-off, clunky hunks of plastic that looked more like a child’s toy hammer than high-tech cutting equipment. These torches did the trick when plasma cutting was in its infancy, but as plasma cutting and gouging evolved, it became clear the torches needed to change to withstand harsher conditions and meet a wider variety of needs.

Many people think that the torch is only important as a holder for the consumables. After all, it is the consumables in the torch that make a plasma system work: the electrode carries the charge necessary to create the plasma from the power supply; the swirl ring forces the flow of the resulting plasma into a vortex; and a nozzle constricts and directs the plasma until it is focused enough for cutting. Indeed, most of the early technology development centered around improving consumable design for increased ease of use and efficiency. For example, in the late 1980s, the introduction of blowback torch technology eliminated the need for high-frequency starts and the advent of shielded nozzles enabled the operator to drag the torch directly on the metal being cut (now commonly called drag-cutting).

Operators saw immediate benefits from these technological improvements. Contact-start systems eliminated interference with other shop equipment, while drag-cutting resulted in smoother, easier cuts that allowed users to follow a straight edge or template. Other improvements focused on safety, like the addition of a safety trigger to eliminate accidental torch firing and a “parts-in-place” circuit to ensure consumables were properly installed before firing the torch. The addition of quick-disconnects, like Hypertherm’s one-button FastConnect™ found on the company’s newer Powermax systems, gave operators the ability to quickly swap torches or to remove the torch when transporting the power supply. But even after all these improvements, the shape and bulk of plasma torches remained the same, limiting their use to certain applications. Making radical changes to this traditional design, would require a whole new engineering approach.

That new approach came from a group of plasma engineers at Hypertherm. The company’s engineering team was determined to re-think torch design. And they knew the best way to understand the challenges their customers faced, was by visiting them and watching them work. Over the next year, engineers and product managers logged hundreds of hours on the road, talking to numerous customers during visits to scrap yards, ship yards, and any other high-use cutting environment they could find. Their goal was to find out how well current plasma torches performed in tough conditions and to see firsthand what operators wanted to do with plasma but couldn’t because of current design limitations.

What they heard and observed is that plasma torches, especially hand torches, take a lot of abuse. It wasn’t uncommon to see torches accidently falling off scaffolding, getting banged against metal plan, or seared by the heat of cutting and gouging. During their visits, the engineers also learned that there were a lot of jobs that operators couldn’t do with a standard 90-degree plasma hand torch or full-length mechanized torch.

Although Hypertherm engineers had plenty of ideas, they focused on three areas: creating a torch that was more robust than anything on the market, improving handle ergonomics while also improving gouging and cutting access for tight locations, and developing a shorter torch for robotic and pipe cutting applications. Everything, from the materials to the consumable design to the guts of the torch, was up for review. Hypertherm engineers spent two years prototyping torches, and then conducting heat, impact, and cut tests. With testing complete, the engineers set out to find the right material for the torch body.

They knew they wanted to stick with plastic because it is light and easily molded, but they weren’t sure exactly which plastic they would use. With hundreds of different brands and compositions to choose from, the task of narrowing down the choices wouldn’t be easy. One thing that helped was the decision to turn to quantifiable measures, like the standards set by the American Society for Testing and Materials for heat deflection, impact resistance and environmental friendliness. Based on that, the team was able to zero in on several different plastics, which had the best balance of properties. Those choices were then evaluated on actual performance, before a winning plastic was selected.

“The challenge with designing plasma torches is that we are cutting metal with a plastic object,” said Jesse Roberts, one of the engineers on the project. “Ideally, the torch handle should be made of brick and rubber at the same time. A brick to take the heat and rubber to take the day-to-day abuse.”

With a material settled on and the durability objective met, the next challenge was to create a torch better shaped for gouging and cutting in tight places. Oxyfuel users have long had an array of torch angles and lengths available to them. With plasma, though, the shape has traditionally been limited by the need for an internal plunger to bring the electrode in contact with the nozzle and start the arc. The plunger, and wires attached to it, needed room to move within the torch shell, restricting the choice of shapes and angles available to the engineers, and therefore limiting plasma’s usefulness for certain applications.

The solution was to work from the inside out. The engineers knew they had to figure out how to remove the plunger before they could even begin to think about making a meaningful change to the torch’s shape. More months of work followed until the team agreed upon a solution: an entirely new consumable design that replaced the plunger in the torch with a blowback spring in the electrode. This breakthrough technology, dubbed Spring Start™, is what enabled Hypertherm engineers to design a nearly straight torch that angles down just 15 degrees at the tip. Additionally, this allowed engineers to narrow the neck of the standard hand torch for greater visibility and to change the shape so that it could be held at either a 75-degree or 90-degree angle to the plate.

Now that the team had successfully met their first two challenges (create the most robust torch on the market, and design a torch better shaped for gouging and cutting in tight places), they turned their attention to the third objective. That objective—to provide mechanized plasma users with the same level of innovation and flexibility that handheld plasma users now had—was driven by observations during end user visits. During those visits, the Hypertherm team noticed that the standard length mechanized torch was often cumbersome for pipe cutting and robotic applications. Their solution was to replace the one-piece mechanized barrel with a modular design that could easily and quickly convert from a long torch to a short one. Users could either work with the standard 15-inch torch or remove a section from the barrel to create a 6-inch mini torch, better suited for robotic applications, pipe saddles, track burners, and other applications where the extra barrel length was a problem.

So far, the new torches, which arrived on the market late in 2010, are getting rave reviews. Plasma users report the straighter profile of the 15-degree torch makes cuts in corners, overhead, and in tight spots much easier. And for plasma gouging, it is truly revolutionary; providing the user with more visibility and better control of the arc while keeping the operator’s hand away from the high heat generated by the gouging process. As Roberts notes, “a fundamental change had to take place in order to advance plasma torches to the next level of reliability and versatility.” And this change is just one step on the evolutionary process. As operators find new uses for plasma cutting and gouging, plasma engineers will keep innovating right along with them.