February 2008 Edition

WELDING

Murder, Inc.

A TIG inverter helps a manufacturer make wheelchairs strong enough to stand up to the abuse of "Murderball"

It's known as Murderball for a reason: it's not only tough on the quadriplegic comptitors, but it is also brutal on their wheelchairs. Producing chairs that can stand up to the punishment, but also come in tops in quality is the job of Vesco Metal Craft — VMC — of Chula Vista, CA. Since each chair is created for an individual Murderball player, they are almost one-off works of art. When creating such customized products, a company can't waste time and still make a profit. VMC found a welding system that cut welding time nearly in half.

Murderball, also called "wheelchair rugby" or "quad rugby," is played by quadriplegic athletes in wheelchairs — neither term captures the sport's speed or intensity as does its original name.

Nor do the athletes fit the stereotypical image of quadriplegics. Their chairs only bear a resemblance to standard wheelchairs. This, as might be guessed from the name, is a tough sport. The rugby chairs are specialized equipment, designed to withstand full-speed, violent collisions. Some are designed with special "pickers" in the front to hook an opponent's wheelchair, which is designed, in turn, to stop that from happening.

It is a competitive sport and athletes want the lightest, toughest, and fastest chair available. Only a few manufacturers meet the demand for rugby chairs; of these, VMC is one of the leaders. Ten of the 12 players on the U.S. National Team compete in a VMC rugby chair.

VMC is a relatively small company with a reputation for high-quality products. It's owned and operated by Neil Vesco, his father, Tom Vesco, and Paul Richardson. Neil does the welding, as well as fabricating the wings and pickers, and uses his expertise as a mechanical engineer. Tom once did all of the chair fit-up. With a new fabricator on board, Tom splits his time between fit-up and final assembly. Richardson, a quad rugby competitor himself, handles customer service.

A cost savings of between $1,600 and $2,400 was possible

Although a standard wheelchair could be used in the sport, it probably could not withstand the punishment dished out in a wheelchair rugby game. Made from 6061 seamless drawn aluminum tubing, heat treated to T-6 condition after welding, VMC chairs are lightweight and custom-made to individual requirements. They are designed to take a beating.

"There are five-year-old chairs out there almost beat beyond recognition, but the welds show they're our chairs," Neil said. "Ninety percent of our customers first notice our welds. They make our chairs stand out."

"Killer" Chairs

Since switching to Dynasty 350 AC/DC TIG inverters, from Miller Electric, Appleton, WI, and the advanced waveform control the machines offer, VMC decreased welding time by 30 to 50 percent, while improving the appearance, strength, and weight of its chairs. VMC now uses lighter material and welds in places that used to go unwelded. The new welders let the company catch up on back orders and look toward developing other products, such as standard wheelchairs.

VMC specializes in rugby chairs for offense, defense, and mid-point — chairs that have both offensive and defensive features. Defensive chairs feature pickers, which grab an offensive player's chair. Offensive chairs have wings to block pickers.

Each chair is custom-made to suit the individual player's seat — also called a "dump" — angle, width, and depth, rear and front seat heights, inside wheel clearance, camber angle of the wheels, frame length, footrest position, and picker style.

To be legal for competition, chairs must meet specifications set by the International Wheelchair Rugby Federation. Initially, VMC changed the design of its chairs to keep up with changes in the sport and to find better ways to decrease weight.

"For the first two years, I don't think we put out more than five chairs where we didn't make another change," Neil said. "The sport evolved quickly. The faster the guys got, the better they got, the more they abused and occasionally cracked the chairs.

"Chair components needed constant improvisements, such as additional gussets. It got to the point where we were adding more gussets and tubes, trying to make them stronger, but the users were still cracking them and the reinforcements were making the chairs too heavy."

It seemed they would have to trade speed for weight to withstand the rigors of the sport. VMC used 0.095 wall tubes, and the cracks, when they occurred, were in the heat-affected zone — HAZ — so VMC switched to 0.120 wall tube. This helped minimize cracks but added weight to the chairs.

Also, the limitations of the company's former TIG unit technology would not let Neil weld in all the spots he wanted. It was those spots that were often the source of failures.

Making a Stronger Product

To resolve these issues, VMC explored two solutions. Tom decided to heat treat the aluminum. Also, Don Peterson, from Miller Electric, recommended his company's Dynasty 350 AC/DC TIG inverter and arranged for VMC to try a test unit. Both steps had immediate benefits.

"Since we began heat treating, we haven't had one break in the HAZ, and we were able to change the wall thickness from 0.120 to 0.083. That reduced the weight from 38 lb to 35 lb," Neil said. "For someone with limited dexterity and muscle movement, that's a substantial change. The player can definitely feel it."

Miller's test unit worked so well that VMC bought both it and a second unit.

The Dynasty 350 features independent amplitude/amperage control, extended balance control, AC frequency control, and AC waveforms control — advance squarewave, soft squarewave, sine wave, and triangular wave. Operators can tailor the arc to specific requirements and preferences.

"The different waveforms — from welding thick aluminum with a regular advanced squarewave to welding thin aluminum with the triangular wave — is what makes it ideal for us," Neil said. "The ability to set EN and EP current independently, along with the ability to vary the AC frequency between 20Hz to 400Hz gives us better looking, deeper penetrating welds.

"When we first got the unit, it came with factory settings and welded better than any machine I've ever used," Neil said. "Then, I found out how much I could change the characteristics of the arc. By turning the frequency up and the balance down, we're able to get a deeper penetrating weld and put much less heat into the frames."

Reaping the Benefits

By switching to the Dynasty 350, the company increased productivity by 30 to 50 percent. Since VMC manufactures three to four chairs per week, each requiring a substantial amount of welding, the productivity increase meant creating from a chair and a half to two chairs more per week, while improving the quality and appearance of the welds.

The company also saved time switching tungsten electrodes due to balling or different weld requirements.

"With the Dynasty, I weld everything with a 1/8" electrode," Neil said. "I can use it on 0.065 tubing all the way up to the 1/4" plate on the front of the chair. To make the welds aesthetically pleasing and structurally sound with our previous unit, I had to match the tungsten to the weld, which required a lot of electrode changing. Our previous machine demanded use of a 1/16" electrode."

VMC found electrodes last much longer now. Previously, Neil had to dress them frequently because at 230 amps, the tungsten would start melting, leading to balling and a large dispersion arc.

"On our old machine, the cleaning action was so poor that we had to turn the balance down to get proper cleaning. Then we couldn't maintain the correct electrode geometry," Neil said. "Now, I don't have to dress the electrode due to balling. The unit maintains a sharp electrode point."

The machine's ability to maintain a sharp electrode and concentrated arc lets Neil weld in corners he previously could not unless he extended the electrode outside the shielding gas, which exposed the weld to contamination.

"I can keep the tungsten back in the cup and still get the arc way back in the corners. Those spots went unwelded and were a source of cracking."

"Our customers congratulate us on how good the frame looks," Neil said. "We set a new standard on the market and our chairs are better crafted than others."

Time, Money, and Energy Saver

With the increased productivity, improved weld quality, and lower power costs, VMC has seen a large impact on its business.

"Our jobs depend on everyone else getting their work done. If I can get in here and weld more chairs for the week, then everyone else has something to do the following week," Neil said. "If I don't get my job done, Tom can't do his and Paul can't do his."

VMC caught up on its backorders, freeing time to devote to research and development for other products to assist people with disabilities. The company can expand its operation with the addition of another trained welder. Finding someone skilled in aluminum TIG welding proved a challenge, but the Dynasty 350 eased that hurdle.

"The unit lets someone with the right skills weld right away," Neil said. "The person we hired sat down and welded with the Dynasty and smiled from ear to ear."

With the pay rate of $30 per hour for a skilled aluminum TIG welder, and a savings of 30 to 50 percent in welding time due to the Dynasty 350 unit, a cost savings of between $1,600 and $2,400 was possible, paying for a Dynasty 350 in two to five months.

Neil estimates the welding unit paid for itself in the first month-and-a-half of operation, through increased productivity and decreased energy bills. With its low power draw — 26 amps at 230V three-phase for a 250 amp, 30V 100 percent duty cycle, the new units are more efficient than the company's previous single-phase unit.

"With the previous unit, I used to watch how fast the meter would turn when he'd start welding and it looked like a spinning fan," Tom said. "Now power consumption is so low, it's ridiculous. I know Neil likes the way the machine works, but I like the power factor. It's a major savings in power."

But even more than the power, Tom said he likes the increased productivity and what it means for VMC.

"Now we have time to do other things," Tom said. "If we're constantly trying to keep up with orders for rugby chairs, we really can't grow and expand. Now we can devote some time to research and development for other products." Miller Electric Mfg. Co.

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