by Noelle Stapinsky
Advancements in high definition plasma cutting
When it comes to the variety of cutting technologies available on the market today, it’s not so much about one technology over another, it’s more about which process will efficiently achieve the desired results.
Plasma technology has been used widely in the metal fabrication world for many years. But recent advancements in high precision plasma systems are carving out a refined position for the technology when it comes to edge quality, surface finishing and sleek contour capabilities.
“The technology has evolved and there are several benefits for fabricators,” says Phillip Parker, marketing manager for Hypertherm’s Heavy Industrial Business. “Reducing consumable costs, improving cut quality so that you don’t have to do a secondary finishing operation, and just being able to take it directly from the cutting machine to the fabricating or welding bay is the goal. The new generation X-Definition plasma takes it to the next level.”
The demand is coming from the industry. To be competitive in the market, automation, quality, complexity and repeatability are imperative. “When you’re talking about complexity, a human can do so many things but not repetitively or with the same accuracy. And automation can either make everything wrong or everything right when it’s controlled,” says Kal Shergill, president of Microstep Canada.
Such increased automation is taking operator error out of the equation, a request that most suppliers are hearing from their customers on a regular basis. “Hiring and training operators can be a challenge. We get a lot of requests for making the system simple to use,” says Jon Ames, director of engineering for Hypertherm’s Heavy Industrial Business team. “There are a lot of options and a lot of ways to set up a plasma and run it, so guiding the user is an important fact for a lot of shops.”
High definition plasma software actually creates the cutting program and the controller delivers a graphical interface for the user. For Hypertherm, it’s about reducing the number of settings and automating as much of the process as possible. “For those that don’t have a current technology controller or want another display on the side, we also use wireless technology to present the operator with another interface where they can choose a cutting process and see what’s happening on the machine live,” says Ames. “We’ve been trying to incorporate things like smart phones, laptops and tablets to take advantage of productivity for the user.”
Past issues such as setting height control or selecting amperage and material types, which were left to the operator, are addressed with offline programming.
“When it comes to standard cutting, operators don’t need to be as skilled as they once needed to be with a plasma system,” says Rodney Plowe, an engineer at Koike Aronson Inc. “Really, it’s the programmer’s responsibility now, rather than the machine operator. Today it’s a little more difficult for the operators to get in there and change things. There are presets in the power supply and controller, so the operator really can’t override that data. The reason why that’s done is because there are plasma manufacturers that have proved what the best parameters are for cutting certain materials.”
According to Plowe, what fabricators are looking for is higher accuracy in the part and overall consumables life.
“The technology in the actual power supply has evolved. Hypertherm has done a lot of development in consumables; they designed a new torch, and have several improvements and patents on their consumables,” he says. “It’s about how smoothly the power is delivered and the gas flow. For mild steel your cut gas is usually oxygen. But then nitrogen was used to save on consumable life. And it used to be that the solenoid valve that turns on to deliver the gas to the torch was six to eight feet away. What they [Hypertherm] have done is the solenoid turns on right in the actual torch body to deliver the oxygen, so it’s immediate. That’s what is giving the extra consumable life.”
Some ease-of-use features that have been added to the software and plasma system are focused on cutting holes. But with plasma, when you get into cutting narrow holes, the ratio tends to decrease in terms of material thickness and the diameter of the hole being cut. “With plasma, you would see the hole start to taper. The top of the hole would have a larger diameter than the bottom. And that was just because of the nature of the plasma arc in the cutting process,” says Parker. “With high precision plasma, you have a much more tightly constricted arc, which helps.”
This is where Hypertherm’s True Hole technology comes in. It’s automatically applied by the nesting or CNC software to improve hole qualities in material thicknesses up to 25 mm (98 in.). It dictates the gas mixture, the speed and acceleration of the torch through the hole. Parker explains, “the customer can set it at a certain diameter, the material and the thickness of the hole from 2:1 down to a 1:1 diameter-to-thickness ratio and it will come out very predictably untapered. Before, the operator would have had to have the skill to figure out all of that and somehow save those settings assuming they might have to do that same job again in the future.”
Beveling is also becoming a more common practice on plasmas. “Again, defining the degree of bevel, how much of the material you want to bevel and how much you want to leave as a flat surface was a very intricate process between the operator and the programmer,” says Parker. “What we’ve done is develop what we call True Bevel. We developed the equations, so if you’re trying to create an angle of 45º on half inch plate, there are settings you can use to automatically angle the torch at the proper height and get the bevel you’re looking for.”
Beveling and dome cutting is a process MicroStep has been focused on. With its mScan software, MicroStep plasma machines have the ability to do 3D cutting on domes, a process aimed at the pressure vessel and tanker manufacturing industries. “We utilize a laser scanning technology that quickly and very efficiently knows exactly what the characteristics of the dome are and is able to cut into it. And we can cut a myriad of different domes with non-uniform profiles very quickly,” says Shergill. “But when you talk about beveling and going at 45º, you’re no longer cutting half inch and you may be closer to an inch when you’re hitting at that angle.
“So you need the power capacity of a high definition plasma to do a wonderful job, fast and with a good edge quality. That’s why we developed this technology,” he adds.
Shergill recently visited a customer in the US that was manufacturing domes manually. “It was not a small company by any means, but it was taking them over eight hours to make one dome end. With our technology, we’re able to cut that time down to one hour, allowing them significant production capabilities.”
Of course, plasma technology really shines with thick materials —typically 6.35 mm (0.25 in.) to 38 mm (1.5 in.). Once 50.8 mm (2 in.) material and beyond needs to be cut, plasma is often accompanied by an oxyfuel torch. Plowe says, “we have a process now that uses oxyfuel exactly like plasma. It’s a one button press. The operator sets the gas pressure, lights the torch and moves away. It even does a hole cutting routine. Oxyfuel is now totally automated just like plasma.”
Shergill agrees that when you get beyond that two inch limit, oxyfuel works very well on thicker material. “And it’s faster than a waterjet. It depends on what you’re trying to achieve. But for heavy fabrication, oxyfuel is here to stay.”
In terms of material type, Hypertherm is noticing a shift from mild steel to non-ferrous cutting. “Stainless is a very important part of what a lot of people work with. It’s a minority, but an important one and a profitable one for metalworking and fab shops. So improving our performance on stainless and aluminum has become a very obvious need to us. And in our latest generation of plasma cutting, the XPR family with X-Definition technologies has really stepped up its capabilities in this area,” says Parker.
Plasma has proven to be a very flexible technology. Whether you’re cutting a lot of thick plate material or for a small job shop cutting a little of this and a little of that, plasma is probably a sweet spot for an entire operation. And, according to suppliers, if the main focus is on edge quality, outside contours and perimeter cuts, high definition plasma technology has a great story to tell versus other cutting technologies. SMT