Evolving From Conventional CNC To Advanced Swiss Technology

Ron Hunt established Hunt Design and Manufacturing Inc. in 1976 in Arab, Alabama, out of his carport. He had one Bridgeport milling machine. Next he purchased a CNC milling machine that allowed the company to compete with bigger shops and earn its share of aerospace and defense industry work available from nearby Huntsville in the mid-1980s. Hunt Design grew to 30 employees, more CNC machines, and larger quarters. But when the defense work fell off, Mr. Hunt knew his company was at a turning point.

He had seen many jobs come across his desk that his company couldn't bid on because it didn't have the right equipment: small, complex parts suitable for Swiss-type machines. In 1999, Mr. Hunt and his management team started comparison shopping and decided to buy a Tornos DECO 2000 single spindle, Swiss-style CNC sliding headstock machine from their distributor, C&S Machine Tool Systems, Inc. At the time the company didn't even have any jobs the machine could be used for, but Mr. Hunt believed there was a need that could be filled with it.

"What sold me on the DECO 2000 was its uniqueness due to the 12 independent axes and counterspindle that allows you to do simultaneous machining operations," says Mr. Hunt. Another reason for the purchase was technology. The technology is a complete system that consists of the machine, the PNC (parallel numerical control) and TB-DECO software. The system is designed to slash as much idle time as possible to minimize overall cycle time. A central clock functions as an electronic camshaft—virtual cams. Just as a camshaft synchronizes operation of individual cams on a cam-operated Swiss automatic, the PNC-DECO controls synchronized the tool movements. Thus, according to maker Tornos Technologies (Brookfield, Connecticut), this is the only computerized Swiss-type machine that can produce parts as fast or faster than conventional cam-types.

Swiss technology was seen as crucial to the company's long-term success. A specific case in point is a family of parts Hunt produces for the semiconductor industry. These are "glands" that have to be of ultra-high purity, and high finish is the name of the game. The parts range in size from ½ inch to 3/16 inch and have various structural designs. There cannot be any scratches or burrs on the inside diameters, no voids or contaminants that could cause damage to the semiconductor chip. The DECO 2000 allows the machine to produce these parts with a high degree of precision due to its centering capabilities. It also makes them competitive with multi-spindle machines because of the independent axes—one-half of the part can be run on the top spindle and the other half can be run on the bottom. According to the company, it has produced between 200,000 and 300,000 of these parts during the past 18 months and has never had a part rejected due to ID finish, the most critical aspect of the job.

Brent Hunt, who runs the Tornos department, explains the process for machining the most complex semiconductor gland, a part that is 1.700 inch long. On the main spindle, the first face is parted off on the center drill, and a small chamfer is left on the front edge of the part. It is then drilled to a 0.167-inch hole, which is a blind hole, then rough reamed to a 0.176-inch diameter. Two different diameters are turned on the OD: 0.251 inch and a 0.346 inch. Both are then roughed and finished. A relief groove is turned on the face and parted off.

Simultaneously, on the counterspindle, the backside of another part is machined. The end is center drilled and turned on the OD to a diameter larger than 0.346 inch. The finish ream is put on (181 ream) to a 5 micro finish. "The finish is the big challenge," he adds, "and it took a lot of ingenuity to get this high a finish." The part then goes to a toroid insert where it is formed and sealed. The tolerance for this part is 0.002 inch.

"The TB DECO programming software has helped increase our productivity and eliminate the need for secondary operations," explains Brent Hunt. All jobs are run on-screen and the program performs a simulation to identify any problems before it downloads. The DECO program also differs from conventional CNC software; it is set up in blocks of programs instead of lengths. Each axis has its own program. It increases productivity because it performs several functions simultaneously, as opposed to conventional programs, which can perform only one function at a time. The program is able to accommodate alternative ways of doing things to make parts run more quickly, or even unattended."

TB-DECO runs on Microsoft Windows. In essence, a programmer selects the required tool for each operation and enters its geometry. Then he or she writes a corresponding machining program for the tools using standard CNC G-codes. The software then calculates and recommends the optimum sequence, enabling the programmer to get the best use of the DECO's several turrets and avoid crashes. The software incorporates canned cycles that speed up the programming process, such as part cut-off and pick-up by the counter spindle, and advancing bar stock. "Then it shows you the production time," adds Brent Hunt.

Particularly for large jobs that run about 250,000 pieces, inventory control can be a challenge. Because Hunt is a small operation, it can buy only 4,000 to 5,000 pounds of material at a time. But with 250,000 piece jobs in the house, the company's financial condition has improved because of the Swiss-style CNC machines.

Buying its (now four) DECO 2000s has enabled Hunt Design to reposition itself among the competition and change its long-term marketing strategy. According to Barry Hunt, the company can attract different types of work, especially high-precision jobs, because of the technology and versatility of the machine. It has increased job size (over 1,000 pieces) and evolved from a job shop into a high-capacity manufacturer of precision parts.