Swissline Precision Manufacturing is a job shop with nearly 30 CNC machines, but the shop is missing the most basic job shop machine tool of all. At Swissline, there are no machining centers.

The president and owner, David Chenevert, disdains the sort of work that screw machine shops and other users of automatic machines refer to as "secondary operations"—work such as milling and drilling performed on a separate machine after a high production lathe has done just part of the cutting. Mr. Chenevert prefers to do all of the machining on the lathe. His machine of choice is a CNC Swiss-type lathe—a sliding-headstock machine with an opposing subspindle and rotary-tool capability. Swissline has 23 such machines.

The shop is thriving. In spite of the general downturn, this shop in Cumberland, Rhode Island, has seen little decline in its own business. The machines are busy, even though the shop limits them to work that requires no complex machining on a follow-up machine. A principal reason why the machines are busy is the marketing effort of the shop owner. He aggressively pursues work outside of what is traditional for Swiss-type lathes, and outside of what is typical for the high-volume automatic machine shops that are the most familiar with these machines.

A Swiss-type lathe is a bar-fed machine that achieves Z-axis motion by feeding the work through the headstock instead of feeding the tool. The tool remains close to the bushing supporting the part. As a result, the cut is consistently stable across the part's length. Typical jobs for Swiss-type machines are long, slender parts that would deflect if supported by a center on a standard lathe. Also typical for CNC Swiss-types are complex, tiny parts that not only are prone to deflection, but also would be problematic to set up on multiple machines.

Swissline does run parts such as these. However, just as routinely, the shop also runs parts such as the ones shown at left—parts that would typically be run using a basic chucker lathe, perhaps followed by a VMC.

In addition, the shop takes on small-quantity jobs. Fifty-piece runs are common, and a 15-piece job was run just before this article was written. Even one-piece orders come in from time to time. In making the shop receptive to a variety of part shapes and a variety of order quantities, Mr. Chenevert has pushed the Swiss-types beyond their traditional niche and moved his company beyond its automatic machining roots.

Two Lathes Per Year

A CNC Swiss-type lathe, or sliding-headstock lathe, is typically used for long parts and tiny parts. Swissline also uses CNC Swiss-types for parts such as the ones shown.

Swissline relied on cam-driven Swiss-type machines when Mr. Chenevert bought into the business in 1985. "Back then, we used secondary operations on everything," he says. Common features such as cross-holes and milled flats couldn't be produced economically on the cam-driven machines. As a result, "we had batches of half-finished blanks sitting all over the shop," all waiting for follow-up machining.

Before coming to Swissline, Mr. Chenevert worked in a screw machine shop that primarily used cam-driven multi-spindle machines. He still thinks in the terms of these lathes, he says. In his mind, a multi-spindle automatic defines the level of productivity that he needs to beat today using a CNC Swiss-type machine. A multi-spindle machine's advantage in this contest is straightforward—it lets multiple spindles work on the same part simultaneously. But a CNC Swiss-type can overcome the need for secondary operations.

Mr. Chenevert oversaw the purchase of Swissline's first CNC Swiss-type the same year he bought into the shop. Two years later, he changed his supplier for this type of machine, buying his first CNC Swiss-type from Tsugami. This builder is represented in the United States by Rem Sales (East Granby, Connecticut), and Mr. Chenevert soon told the distributor that he planned to buy two more such machines per year. The Rem Sales representative was dubious. Fifteen years later, however, Swissline has purchased 30 of the Swiss-type machines. The oldest of these machines have been replaced by higher-function models, but most of the machines are still in daily use.

One very useful avenue for finding work for these lathes has been job shop shows, Mr. Chenevert says. The potential customers he meets by exhibiting at these shows often don't know what a Swiss-type machine is. Those who do tend to have an inaccurate perception about what the machines can do.

"I ask them what parts they're running, and what their problems are," he says. Certain machining problems are red flags, alerting him to a job that a CNC Swiss-type could run more effectively. These problems include concentricity error, milling location error, deburring problems and unacceptable finish.

"For a typical job where one of our Swiss-type machines replaces some multiple-setup process, we can reduce labor, increase efficiency and improve tolerances—all at once," he says.

But the shop doesn't realize these benefits for just any part. Swissline may be challenging the perceived limitations of a Swiss-type machine, but this machine type does have certain limitations built in that are very real.

Working Small

One obvious limitation of a Swiss-type machine relates to work diameter. Tsugami offers Swiss-types accommodating work up to 1.5 inch in diameter, and this is very large for a Swiss-type machine. Swissline bought a fixed-headstock CNC lathe just so it could have the capacity to take on parts larger than this.

Horsepower is another limitation. A Swiss-type with 15 hp for the main spindle is a powerful machine. The much smaller rotary tool spindles are light enough that using them to machine hard metals can be a challenge. In fact, the need to drill holes in hard workpieces represents a common reason why Swissline does resort to secondary operations. In these cases, the work is done on a simple milling and drilling machine, often a manual one. (Another example of when Swissline does resort to secondary work is when the fixed-headstock lathe is used to cut the part-off nub left behind by a Swiss-type model that lacks a subspindle. In other words, the shop uses secondary operations only for very simple features, not complex ones.)

Based on the simple shape, this would seem to be a suitable part for an automatic lathe. The need to hold a narrow tolerance on diameter was the reason it was run on a CNC Swiss-type.

And yet, even though horsepower may be limited compared to other types of lathes, the availability of 15 hp machines represents a major improvement over the previous limits of what CNC Swiss-types could do. These machines have steadily improved, and Mr. Chenevert has watched the evolution. He notes that the machines now offer high speed CNCs, linear ways, direct-drive spindles and servo control over the vertical position of the turret. None of these features was available when he was starting out.

As a result of these and other improvements, he says, Swiss-types today perform effectively across a much broader variety of work than they are usually given credit for. They can generate a range of complex features. And they're not limited to aluminum and brass—a common misperception.

"We run 4140 steel all the time," he says. "We run Inconel."

The machines are not particular about the production quantity, either. In addition to large runs, Mr. Chenevert uses the machines to run small batches, even prototype parts. To handle short-run work effectively, the shop relies on employees who are sufficiently practiced and equipped that they can initiate a new job at any time. (See the companion article in the shaded box.)

Recently, a ten-piece order for a prototype part was placed by the customer, then programmed, machined and shipped by Swissline, all in the same day. Mr. Chenevert says, "I wouldn't want to make my living off of jobs like this, but it helps us that the customers know we can do this kind of work when they need it."

Mr. Chenevert (bottom left) oversaw the purchase of this shop’s first CNC Swiss-type machine. Now, the shop now has nearly two dozen.

For more information about Tsugami CNC Swiss-type lathes from Rem Sales, call (860) 653-0071, enter 33 at www.mmsinfo.com to visit Online Showroom, or write 33 on the reader service card.

For more information about CncGcoder from RBR Machine Tools, call (630) 971-8729, enter 34 at www.mmsinfo.com to visit Online Showroom, or write 34 on the reader service card.

For more information about tool dispensing systems from Kennametal, call (724) 539-5330, enter 35 at www.mmsinfo.com to visit Online Showroom, or write 35 on the reader service card.

Empowered Personnel

Swissline lacks not only machining centers, but also CAM software. New jobs coming into the shop are sent to the shop floor before an NC program is available. Company president Dave Chenevert, now a 20-year veteran when it comes to looking at turned parts and thinking about how to machine them, quickly maps out the order of operations for any new part. After that, an employee on the shop floor authors and enters the NC file by working at the lathe's CNC. NC files are moved to and from the Swiss-type machines using a personal data assistant engineered for this purpose. A shop that is new to Swiss-type machines may or may not be able to follow this same procedure efficiently, Mr. Chenevert says. Swissline has formalized the process after years spent working this way. An internal training program moves employees from "loader" through three levels of "operator" and up to three different levels of "setup." The employees in this last category are the ones who author and manipulate NC files, and the shop aims to train as many employees as possible to reach one of the setup levels. The benefit is flexibility, Mr. Chenevert says. A shop that doesn't depend on CAM software also doesn't have to depend on a small number of programmers (probably just one or two people for a shop Swissline's size) to send any job to the shop floor. Instead, with shopfloor personnel skilled at NC programming, any of a variety of employees can begin working on a job at any time. Also, if an NC program has to be changed because there is a problem with the program, or because the customer made a design change, an employee running the job can make that change without delay. The flexibility is particularly important on Swissline's shop floor, which runs round-the-clock in order to meet tight lead times on short-run jobs. With the programming function spread out across the shop floor instead of being centralized in the office, it's less likely that an employee will have to wait until morning before a needed program change can be made. An automated tool dispensing system provides controlled, 24-hour access to tooling. The unit takes the place of an attended tool crib, capturing more detailed information about tool use than a crib could be expected to track. NC programs created at the CNCs are stored off-line in a separate computer, so any appropriate machine can use an existing program the next time that job is run. Thus the NC programs in this shop follow an unusual path. Instead of beginning in a PC and being downloaded to the machine tool, a program begins at the machine tool and moves in the opposite direction. Swissline's file management system doesn't simply send programs to machine tools, it draws them out as well. In the past, shop personnel moved these files by pushing a PC on a cart. Now they use a hand-held personal data assistant (PDA) outfitted specifically for this purpose. This unit is a product called "CncGcoder" available from RBR Machine Tools (Darien, Illinois). It consists of a modified PDA equipped with software for uploading, downloading and editing NC files. The accessory makes Swissline's method of file management easy to carry out. One other important piece of hardware at Swissline isn't related to NC programs, but it does fit with the shop's philosophy of giving employees access to the resources they need to keep working. The relatively small job shop uses a tool dispensing system comparable to what large machining facilities use. The "ToolBoss" unit from Kennametal (Latrobe, Pennsylvania) automatically monitors tool inventory and tracks which jobs and which employees are using particular tools. Mr. Chenevert summarizes why he decided on a tool dispensing system. "I got to a point where I realized I needed a tool crib, and I was going to build a cage and hire a crib attendant," he says. "In the long run, this is cheaper." In addition, the unit also gives him information that would be difficult for a tool crib attendant to track—that is, precisely how much money is spent on tooling for each individual work order.