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The Torch Passes to a New Generation

Aug. 4, 2011
New materials and shapes increase the range of plasma cutting applications
The ideal plasma torch handle must be sturdy enough to endure rough handling, and heat-resistant to withstand its own cutting strength.
Hypertherm’s breakthrough Spring Start technology made it possible for engineers to design a nearly straight torch that angles down slightly at the tip, with a narrow neck for better visibility and a shape that is easy to hold at a 75-degree or 90-degree angle to the plate.
Hypertherm engineers replaced a one-piece mechanized barrel with a modular design that converts easily and quickly from a long torch to a short one. Users 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 is problematic.

Every new technology, from automobiles to televisions, goes through an evolutionary period when the design develops from the early, rudimentary concept to modern, refined, and user-focused. Think of your first computer or cell phone: it bore little resemblance to today’s tablet devices and smart phones.

The torches in place on today’s advanced plasma cutting systems are no different. The first torches were squared-off, awkward 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 emerging, but as plasma cutting and gouging evolved the need became clear for torches that 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 on 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 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 one-button FastConnect™ found on Hypertherm's newer Powermax systems, give operators the ability to swap torches quickly 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 Hypertherm plasma engineers determined to re-think torch design. They knew the best way to understand the challenges their customers faced would be to watch them work. Over several months, engineers and product managers logged hundreds of hours on the road, talking to numerous customers during visits to scrap yards, shipyards, 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 observed and learned is that plasma torches, especially hand torches, take a lot of abuse. It wasn’t uncommon to see torches accidently falling off scaffolds, slammed against metal, 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° plasma hand torch or full-length mechanized torch.

Although Hypertherm engineers had plenty of ideas, they focused their redesign efforts 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 easy to mold, but they weren’t sure exactly which plastic to 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 that had the best balance of properties. Then, those choices were evaluated for 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. “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.

Their solution was to work from the inside out. The engineers knew they had to figure out how to remove the plunger before they could make 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™, helped Hypertherm engineers to design a nearly straight torch that angles down just 15° 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° or 90° angle to the plate.

Having 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), the engineers turned their attention to the third objective: to provide mechanized plasma users with the same level of innovation and flexibility available to handheld plasma users.

During their visits to torch users, the Hypertherm engineers 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 have been commercially available since late last year, are getting outstanding reviews. Plasma users report the straighter profile of the 15° torch makes cuts in corners, overhead, and in tight spots much easier. And, for plasma gouging, it provides 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 noted, “a fundamental change had to take place in order to advance plasma torches to the next level of reliability and versatility.”

This change is just one step in an evolutionary process. As operators find new uses for plasma cutting and gouging, plasma engineers will keep innovating right along with them.

Paula Flanders is a technical writer and marketing specialist with Hypertherm, a designer and manufacturer of plasma cutting systems.

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