Application Trends For A Variety Of Swiss Turning Machines

The old perception that Swiss turning machines are designed solely to produce millions of simple, 30-cent parts is changing—just ask the people at Northwest Swiss-Matic Inc. (Minneapolis, Minnesota). This high precision contract manufacturer uses 19 CNC Swiss machines plus an array of more than 70 production line machines. The shop's production system includes both dedicated and semi-dedicated manufacturing cells designed to provide flexibility in producing a variety of parts.

In these cells, CNC Swiss-types, multiple spindles, CNC chuckers, horizontal and vertical machining centers, Escomatic wire machines and other equipment are mixed and matched according to specific part requirements. Each of the various cells can produce approximately 60 varieties of a single part or output complete part assembly groups. The cellular manufacturing approach yields a continuous flow of parts with consistent quality to meet customers' stringent delivery requirements. Northwest specializes in screw machined parts with diameters ranging from 0.010 to 2.625 inches and lengths ranging from 1/16 inch to 3 feet. Some of the shop's typical products include spools, sleeves, pistons, valve assemblies and families of screw machine parts.

Northwest, established in 1962, is a supplier for automotive, motion control, military, hydraulic, pneumatic and electronics manufacturers. It produces parts that range in cost from less than 30 cents up to more than $3 each.

Two main trends have been observed in Swiss turning that seem to correspond to a shop's size. Big shops tend to emphasize unattended operation and consistent accuracy, while small shops need machines that are versatile enough to make any type of part. "Both trends exist," says Northwest's vice president of manufacturing, Terry Haubrich, "but it's all a question of cost. You can't really separate different sizes of shops and say that they want different things. Both seek the same results by using available technology to obtain the best quality at the lowest cost. The difference may be that smaller shops have less capital resources available to purchase the more expensive, higher technology machines."

For these smaller shops, the quest for versatility can be a double-edged sword. Adding more tools to increase a Swiss machine's versatility also adds to the number of tool changes and increases the need for operator intervention. But does this necessarily lead to a "Catch 22" situation?

Not according to Mr. Haubrich. "By combining a series of machine operations—such as by having several bar loaders in a shop—a large amount of operator time can be eliminated," he says. "Because the operator doesn't have to manually load machines, more time is available to change or sharpen tooling. This upgrades the operator's work to a higher and more productive level."

Advancements in metalworking equipment have significantly changed the operator's role, according to Scott Larson, head of the shop's Swiss department. "We use computers right at our workbenches for part layout, machine programming and statistical process control," he says. "This has made the operator a much more integral part of the design and production process," he adds. "Our operators are very skilled technicians, especially in applying math, geometry and complex computer technology."

But what about shops that still prefer older and less sophisticated machines requiring less operator training? "Although that's one option, technology advancements eventually will overtake that approach," Mr. Larson says. "In the long run, upgrading equipment and the skill levels of employees is the best way to achieve high quality at the lowest cost."

Much has been said and written about the difficulty of finding good machine shop personnel. While admitting that staffing represents a problem for almost every shop, Mr. Larson sees light at the end of the tunnel. "We believe that the combination of more highly automated equipment and better-trained operators is a partial solution to the labor shortage," he says.

"Because of the computer, there's really no end to how far an operator can go. The opportunities for beginners in this field are unbelievable. Operators who want to learn advanced skills can integrate computer and software features into their machines and processes. But even operators who don't want to learn the higher level skills can become proficient, because available machine control software is easy to use."

As someone who has personal experience with the transition from conventional lathes to Swiss turning machines, Mr. Larson is familiar with the learning curve that operators face. "A lot of the principles for both types are the same, except that more operations are happening simultaneously on a Swiss machine," he says. "Speeds and feeds are different on a Swiss machine because, in most cases, you don't make separate roughing passes. The main spindle completes roughing and turning at the same time, so you're taking everything off in one pass."

In addition to multiple, simultaneous machining operations, operators must also adjust to Swiss machines' substantially lower feed rates and deeper cuts. The Swiss machines do have advantages, though, including the ability to produce finished parts, thereby eliminating the secondary operations and additional machines that were formerly required. Because each live tool on many Swiss machines is driven by its own servomotor, higher rpm is available, and operations that formerly required the use of a separate machine are now possible with a single setup.

Programming Swiss machines is also easier. "You don't have to buy expensive and complicated CAD/CAM software to program these functions on the new Swiss machines, because this capability is incorporated into their programming software," says Mr. Larson. "When you do need more complex software—such as GibbsCAM for example—to design a part, you can download your design to the machine and operate it using the same software."

Swiss turning machines have had a dramatic effect on screw machine shops' productivity. Mr. Haubrich has observed the impact of this trend in recent years. "I've seen some of our competitors that previously were not Swiss machine houses now buying these machines to produce complete parts without the need for any secondary operations," he adds. "Combined with the improved bar loaders available today, more companies now run production unattended at least part of the time."

If a shop can add an unattended night shift, for example, it immediately gains 8 to 10 more hours of machine usage per day. When handling typical long-running jobs, the combination of Swiss machines and high performance bar feeders represents an investment that pays off in a short period of time. Speaking of the bottom line, Mr. Haubrich says, "Cost, budget and profitability are the main factors we evaluate. If the numbers are right to integrate a better technology, we'll go for it."