Robotic Technology

A useful marriage

By Russ Olexa

March 2009 - Bill Kunz, CEO of Applied Robotics Inc., Harwood, Md., makes Torchmate products in Reno, Nev., and felt there had to be a better way to produce his plasma systems. He’d been manually fabricating them, but there were inherent issues with the process.

He needed to produce both holes and bevels on his equipment’s square steel-tube legs, but his flat-bed plasma system couldn’t process them. The cutting head didn’t have enough Z-axis height or the necessary flexibility to be positioned for beveling.

Flat-bed plasma cutting systems are well-suited for cutting flat sheet metal. But for processing a pipe or square tube, they can’t do it without major modifications to the entire system, such as adding a rotating axis. Most plasma systems won’t allow this type of change. A five-axis, 3-D plasma is much more flexible but expensive.

Kunz, however, found a way to handle these complex cuts while seizing a new opportunity to serve his customers.

Starting out
"My dad started the business about 30 years ago by coming up with a pantograph machine that used a torch for cutting shapes out of sheet metal," he says. "For about 20 years, he sold this equipment as a kit that had to be welded together by the end user. By offering a kit, he was able to sell his system at a much more reasonable price than other manufacturers. He also found that shops buying his equipment could weld better than he could.

"As a fabricator, he was always into cars and made parts for them," Kunz says about his father. "He worked with the pantographs for many years. About 10 years ago, I started working with him and introduced him to other ways to market our products. He was conservative. He didn’t want any employees. I ended up hiring my sister-in-law as my first employee about six or seven years ago, and my dad is still mad at me. But he’s 3,000 miles away, so it was easier to ask for forgiveness than permission."

Kunz mentions that the company developed a kit-style plasma system called the Torchmate 1 CNC plasma machine that is still sold today. It takes about 40 hours to build, and the purchaser needs to get a list of steel from the local service center to build it.

It turns out, however, that a lot of companies didn’t want to spend 40 hours putting one together. They wanted a system that could go together faster, and they were willing to pay for the convenience. This need instigated the development of the extruded-aluminum-frame plasma system that bolted together: the Torchmate 2. It takes about 16 hours to build. The frame is still welded together, but the arm that moves the plasma torch, which took much of the time to fabricate, now bolts together.

Then, companies wanted a completed machine. So Kunz’s company moved up to a complete extruded-aluminum machine with a frame. Everything bolts together, requiring about eight hours of construction time.

"Now we also have our Torchmate 4, our X model, which is a finished machine with either a water or a downdraft table to handle the smoke created from cutting," Kunz adds. "We crate it, ship it, drop it on the floor and it’s ready to go."

Production challenges
Originally, all the fabrication for the Torchmate system was done by outside vendors, says Kunz. But with demand increasing, he says, "We brought all the plasma systems in-house for fabrication, and of course, we use our own plasma systems to make the parts for them. We sold a lot of our Torchmate X models, but we stopped pushing them because we had to figure out a better way to produce them in-house. Having vendors build them was getting too expensive.

"Now we’re ramping up the marketing and building a new facility to develop an automated manufacturing system using robots, plasma systems and conveyors to produce them as fast as we can," he says. "We sell between 50 and 100 machines per month, and it varies quite a bit on the models we build. We definitely have specific markets that use the different types of machines. So to produce the various models is a challenge."

Producing the legs for his Torchmate X systems was a headache. The legs had different types of cuts, along with holes. A 3-D plasma or laser cutting system could do them--expensively. Kunz didn’t have either system but wanted to look into new production methods.

A modern technique
Kunz says the company was looking for a way to manufacture all of its products in-house, but without a large amount of labor. Often, up to five people were involved with building each plasma system. With cutting the legs on the Torchmate X and other production challenges, he felt there had to be a better way. "One of our suppliers that we get our aluminum extrusions from invited us to a robotics and vision show in Chicago a couple of years ago," he says. "Seeing what they had at the show, my father and I both realized that robots could be used to do our manufacturing.

"We met with Kuka Robotics Corp., [Clinton Township, Mich.,] and talked to them about robots and their price tags. We found out how inexpensive robots could be and that they were actually easier to program than our plasma systems."

A robot can be taught how to perform a task via its controller or a CAD file, he says. For Kunz, the decision to implement the robots was an easy one.

"At the same time, we realized that there weren’t any plasma cutting systems using these robots," he explains. "Therefore, we could develop this capability and serve the market with it. It took a while because Kuka doesn’t have any experience with plasma equipment."

Thermadyne Holdings Corp., St. Louis, the equipment manufacturer used for Torchmate’s plasma cutters, didn’t have experience with robots either. Kunz provided a bridge to get the two companies working together and has been in the middle, doing R&D for the system.

Robotic challenges
Robots have a long history of doing multi-axis welding in the automotive industry, but it’s not as though they could just pick up a plasma torch and start cutting. "The software had been written for robots to work with welding systems for a long time, but it didn’t exist for robots using plasma cutting torches," says John Gilbertson, automation district manager for Thermadyne

Once programmed, a robot knows where it is in 3-D space within ±0.1 mm, and it’ll accurately repeat this positioning. But when the material it’s cutting begins to grow and move from the torch heat, the robot’s accurate plasma cutting capability might start drifting out of tolerance. A robot can’t see to correct for the growth problem. With a vision system it can, but it’s an expensive option. This was the problem Kunz faced: how to get the robot to react to the material growth and maintain a precise cut.

For a flat-bed laser, this is accomplished by an automatically adjusting height-sensing cutting head, but no one had this feature for a robot at that time.

"You have to deal with a few things when it comes to plasma cutting," Kunz says. "You have to maintain the torch height to get a proper cut without beveling the edge. You have to stay a specific distance from the material. We’ve been fairly strong with height control for our systems for a number of years. The height control we use on our machines is lighter than others available. Our height control is light enough that a robot can handle the weight. You only have to be within 3 in. of the surface, and our height-controlling plasma head will automatically adjust to the proper cutting height.

"For a plasma system, though, it’s not a matter of how far the head is away from the material in distance," he continues. "This distance is actually measured in volts. As the plasma tip is moved further away from the metal, the voltage goes up, and the cut loses quality. There’s also a perfect voltage to be maintained to get a proper cut with the least amount of undesirable bevel and slag on the material’s cut edge."

The challenge for Kunz was to get Thermadyne to work with Kuka to develop software that would allow both the plasma and the robot controllers to talk to each other. This was essential for maintaining the proper voltage and achieving the correct cut height on a consistent basis without the use of Torchmate’s height-control cutting head.

"[Thermadyne] had all the accessories [such as the plasma torch for the robot] for the system, but not the actual plasma power source that would integrate with the robot’s controller," Kunz says. "We had to get the plasma system to talk to the robot. They had welders that did this, but not a plasma system."

"Robots have a problem reading the distance the torch is from the material," Gilbertson adds. "They’d read it one way for plasma and another for welding, which becomes an issue. If the robot can read the voltage, then it can maintain the perfect height, and you don’t have to put in a torch-height sensor on the robotic arm, which adds extra weight."

At one time, Thermadyne didn’t have a power source that could be integrated into a robotic arm. It does now. "We have several that adapt well with a robot," Gilbertson says. "It’s a good marriage for us."

"Another challenge is to make sure the robot moves in the correct way in the 3-D mode," Kunz adds. "If it moves the wrong way, it can cause a problem in certain cuts. This is where the proper programming comes in. There’s software that will do this, but it’s expensive and you’d lose the advantage of what a robot can offer in terms of the extra cost. What we’ve been working on is the ability for the robot to use the plasma cutter without all the added components and expense."

Next step
Now that Kunz, along with Kuka and Thermadyne, has overcome the plasma cutting problems, he says, "We’re stuck in the middle ground between using the robot for our own production, and when it comes up, doing samples for companies that want to buy a robot/plasma system.

"These companies want the system for production, but now we’re struggling with how to handle fixturing and safety for their production needs," he says. "There are certain guidelines you have to use for safety concerns when it comes to robots, but in the end, it’s up to the end user to provide a safe environment." Kunz doesn’t want to provide a robotic solution that requires going out and setting it up for the customer. "The equipment will be delivered, bolted to the floor and run," Kunz says. "We’ll train them and set up the robot here so they can see it. But fixturing is the part that’s unknown because we need to know the customer’s needs to be able to do it. There are companies that just do fixturing, so they might be the answer. We’re waiting to see what customers need."

Kunz’s main reason for working with a robot was for his own production. "The only way to make sure a product is the same every time is to keep human hands off of it, and that’s what we’re trying to do using a robotic solution," he says.

Applied Robotics’ manufacturing system for its plasma products was developed using Kuka’s robotic simulation program, which allows a company to build a manufacturing cell and test it through its software. Applied Robotics’ new 8,000-sq.-ft. space will be one large robotic cell, says Kunz. Realistically, the company plans to have two people running the entire system, as opposed to building the plasma systems by hand with about five people.

Although Applied?Robotics has the space, and the plans were finished as of January, Kunz was waiting on building permits to begin the construction process. The manufacturing cell will use Kuka robots with handling fixtures to put together the parts of the plasma systems. Then, another robot with either a plasma cutter or welder will cut or weld. The robots will have interchangeable end effectors for either of the two processes. Conveyors will be used for material handling for raw material and carrying away finished parts.

"Hopefully, we can put out a product that’s the same every time," Kunz says. "We make a 10-ft.-by-40-ft. table that would take about 12 weeks to make by hand. With the new robotic system, it should be made within several days. Then we can build to order." FFJ


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