Tuesday, January 22, 2008

Welding powers world-class cycles: Miller supplies latest technology to Cannondale.

Welding powers world-class cycles: Miller supplies latest technology to Cannondale.

At Cannondale Corp., Bethel, CT, superior performance of its world-renowned aluminum frame bicycles and motorcycles results from welding innovations that help achieve the lightest weight possible while maximizing product performance.

One recent decision to raise manufacturing and cycle performance included a plan to upgrade older Miller Electric AC/DC TIG welding machines to Miller's new Syncrowave 250 DX, which features some innovations of its own.

"We've been using Miller for 18 years, ever since we started manufacturing bicycles in 1983," says Kevin Pahl, engineer and C.W.I., Cannondale. "We're working toward an 81-unit fleet where all machines feature Miller's squarewave technology, either the new Syncrowave 250 DX for our bicycles or the Syncrowave 350 LX for motorcycles and new ATV line."

Although he did not realize it until later, Pahl directly contributed to the improved performance of the Syncrowave 250 DX.

"Miller invited me and five other welding experts to its Appleton [Wisconsin] facility to participate in blind arc tests during product development," says Pahl. "There were three different Miller TIG machines behind a curtain and we had to weld with them and rate their performance. I thought all of the machines welded just fine, but the arc kind of stumbled at the start on two of them."

As a result of this feedback, Miller determined that welding operators would most enjoy working with a machine that featured better arc starts but maintained the arc characteristics of the existing Syncrowave 250.

A classic at work

Miller created a selectable start condition feature. This innovation controls the initial volume of current, regardless of welding amperage, during the first few milliseconds of arc initiation to ensure positive arc starts. Because different applications require more or less initial current for positive starts, Miller lets operators select from "soft," "standard" and "hot" arc starting conditions. Soft start helps with small diameter tungstens or thin metals, while the hot start improves starts with the large diameter tungstens used for thicker metal.

The Syncrowave 250 DX, for example, comes factory set to optimize starts for general use, such as the 1/8 "diameter zirconium electrode Cannondale uses.

In beta testing at Cannondale's Bedford, PA, facility the quick response of the Syncrowave 250 DX was confirmed by welding operator Dale Troutman. "You'd better be ready to weld when you push the pedal down because the Syncrowave 250 DX takes off right away. The arc starts are really good, and the weld puddle forms quickly. It feels like the unit has more heat, so my welds smooth up easier. I don't feel like I have to work as hard compared to my old unit. I also like the fact that it's quieter."

Welding supervisor Terry Crawford adds: "The Miller machines have always worked well for us. They create a nice, soft arc at low amperages and a stiff arc on the high end. This is very important to our application because we use a wide range of amperages due to the 0.028" to 0.125" thickness range of our 6061-T6 aluminum tubing."

Beefy tubing

Any cyclist who has spent serious time in the saddle instantly recognizes an aluminum frame bike because of its oversized tubing. The outside diameter of the head, top and down tubes on a Cannondale bike ranges from 2.5" to 3.75" because doubling a tube's diameter increases its flex resistance by 800 percent. This robust profile ensures that all of a rider's one-half horsepower of pedalling energy gets used to push him or her forward, not toward flexing the frame and wasting energy.

Increasing the diameter also allows Cannondale's engineers to shave more material from the tube walls without sacrificing structural integrity (as diameter increases, wall thickness can decrease yet still yield the same strength). Shaving weight whenever possible further enhances a rider's energy expenditure, providing greater climbing endurance, speed in the flats and overall enjoyment.

Other innovative Cannondale weight-shaving measures include drawn and butted tubing and machining away the front-outer surface of the head tube and portions of the bottom bracket. Both techniques create a thicker wall at the ends of the tube--which absorb the most stress and form part of a welded joint--and a thinner wall in the middle of the tube.

Breaking the rules

While other manufacturers use a fork supplied by a third party, Cannondale chose performance over convenience and developed the technologically superior HeadShok fork. Unlike telescoping-blade forks (picture shock absorbers on each side of the front tire), all travel on the HeadShok fork takes place within the head tube. Bikes with this feature respond better to bumps and provide tighter handling.

Cannondale also uses a different welding technique than other bike manufacturers. "Instead of the traditional stacked-dime TIG weld bead appearance and welding the joint in a single pass, we break the rules a little bit by making two passes," says Crawford. "With our technique, the first pass ensures complete penetration. We then make a second pass that smoothes the weld bead to the point where the joint looks like it was molded." Because the cosmetic second takes the crown off the weld, operators continue to add filler wire to maintain throat thickness.

"Our welding method improves fatigue life," states Pahl. "Our welding method creates a smooth transition from the weld joint to the rest of the tube, and this helps prevent stress risers. Stress risers occur at the outer edge of an unfinished weld where the weld abruptly ends. At that point, the tube wall suddenly gets thinner, so it's more prone to the accumulated stress that builds up with riding. Our technique tapers the walls more gradually, which disperses the stress over a wider area. As a result, our frames last longer." It also allows Cannondale to use thinner wall tubes for a lighter frame.

Building the bike

Except for its one carbon fiber/aluminum model, Cannondale builds all its bikes from 6000 series aluminum tubes. The company feels that the 6000 series can be shaped and machined for more creativity, giving the company more design flexibility than 7000 series or metal matrix aluminum compounds.

Tack-welded frames are moved to finish welders like Dale Troutman, who weld the frame and head tube (all welding conforms to AWS D1.2, Structural Welding Code-Aluminum). Every year, Troutman and the 50 other finish welding operators produce hundreds of thousands of frames. To achieve such high production, operators use an automatic filler wire feeder that draws from 16 lb. spool of 1/16" in. diameter ER4043 filler wire.

"If we had to feed a rod by hand," says Troutman, "it would take a much longer time. But with a feeder, when you need wire, it's there for you. You don't run out after 3 feet, either." While the wire feeder improves the productivity of all the welding operators, Troutman can go faster because of his new TIG machine.

"There's a night and day difference heat-wise between the new Syncrowave 250 DX and our old machines," says Troutman. "As soon as I step on the foot control, 'Boom!' the heat's right there. It also lets me keep a nice, tight bead on my first pass and lets me smooth out the weld on the second pass a lot easier."

Using the Syncrowave 250 DX's digital meters, Troutman limits his maximum welding amperage to 170 amps for the thinner frame tubes and 200 amps for the thicker head tube. He varies his actual welding amperage with the foot pedal control from 30 amps to 200 amps. Because the tubes go through an acid wash that removes oxidation and oils, Troutman can set the machine's balance control for more penetration (8 on a 1 to 10 scale) and less cleaning.

While these welding improvements keep Cannondale current with new technology, the company's success rests squarely in the skilled hands of its TIG welding operators.

Riding the tide of success with its bicycle line, Cannondale started a motorcycle operation in the summer of 1998 and plans to begin production of ATVs in 2001.

As with its bicycles, the company continues its spirit of innovation with motorcycles. The exhaust from the four-stroke, single cylinder 432cc engine comes straight out of the back of the engine (which Cannondale builds itself, from scratch). This bike is also fuel-injected and starts electrically. And naturally, it features a twin-spar, lightweight aluminum frame.

To weld the thicker aluminum on the motorcycles, Pahl brought in 10 Syncrowave 350 LX TIG power sources because of the machine's ability to work long hours at settings as high as 300 amps. "All our Miller TIG machines run 14 to 18 hours because we run two shifts," Pahl says. "That is a testament to how well built the machines are and how long we can count on them to last."

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