Programming Swiss Lathe

[Concordia Zentner]

Whois using CNC Swiss-type lathes? The answer has been changing. While medical and electronics applications accounted for large shares of investment in this type of machine tool in past years, more recent adopters have been more evenly spread across various industry applications. As shops come to discover the value of CNC Swiss-types, many are installing this type of machine for the first time.

Groth Manufacturing is an example. The contract manufacturer in Carpentersville, Illinois, has 35 CNC machine tools, including horizontal and vertical machining centers as well as CNC lathes. Its most recent machine purchase is a B0124 CNC Swiss-type from Tsugami.

Company President John Groth says the components used to be machined on a more conventional CNC turning center. A box tool turned the precise diameter. However, when the customer asked to be able to order parts in smaller quantities and with shorter lead times, the shop had to begin carrying inventory to accommodate the request. Stocking the inventory created extra expense, so Mr. Groth had to find an offsetting cost reduction. The efficiency gain from turning the pins more quickly on a CNC Swiss-type delivered the needed savings.

A Swiss-type lathe is a variety of turning machine that feeds the stock through a guide bushing. This means the OD turning tool can always cut the stock near the bushing, and therefore near the point of support, no matter how long the workpiece. The machine feeds the work out of the spindle and past the tool as it goes. This makes the CNC Swiss-type particularly effective for long and slender turned parts.

Relative to other CNC machines, he says the biggest adjustment with this machine has probably been the programming. The machine moves in ways that are foreign compared to other CNC lathes. Some M codes and waiting commands are also different. For the sake of learning the machine and developing proficiency with it, Mr. Groth is forgoing CAM software for now in order to program the machine by hand at the control.

Douglas Paoletta knows something about that learning curve. A programmer of CNC Swiss-types who recognized the increasing popularity of these machines, he founded a business aimed at helping machining facilities become proficient with them. Encompass Swiss Consulting, based in Richmond Heights, Ohio, provides both contract programming and instructional services related to these machines.

Compared to conventional CNC turning, CNC Swiss-type machining is a different experience, he says. Machinists and programmers shifting from one to the other have to adapt their thinking about the machining cycle in various ways. He cites the following differences:

The order of cuts in the cycle also changes with a Swiss-type. On a conventional lathe, it is typical to rough turn and finish turn the work, then machine features such as OD grooves or threads to complete the part. Not so on a Swiss-type.

But at the same time, batch sizes are not large. Although his screw machines are not directly comparable to the Swiss-type, they are also productive for precision machining of small turned parts. Indeed, he still quotes new jobs for them. However, these machines are not effective for the small production quantities his customers increasingly require, because their setup times are too long. Thus, the CNC Swiss-type machine is perhaps uniquely suited for small and delicate parts with both tight tolerances and small production quantities.

His shop will get another CNC Swiss-type, he says, because he sees considerable opportunity in parts that fit this very description. However, the next Swiss-type he buys will be different. The current one was chosen for a particular family of parts; it accommodates a maximum bar size of 12 mm. Barstock up to 20 mm is the size he would choose next. In addition, he says his next CNC Swiss-type will feature live tooling, in order to fully realize the range of parts that a machine such as this can produce.

These military rifle components (this photo and the next one) have tolerances of 0.0005 inch on diameter. Cutting the parts gingerly on conventional lathes resulted in a machining cycle that was much less productive than what the CNC Swiss-type can now deliver.

A Swiss-style lathe is a turning machine that feeds the stock through a guide bushing. The tool cuts the stock near the bushing, which is the support point, no matter how long the workpiece. This makes Swiss machining a good choice for long and slender turned parts, such as needles.

Though not restricted to use with Swiss-type machines, tool presetters have become increasingly popular with Swiss machine users over the last couple of years, according to Ed Garber, national sales manager for Star CNC Machine Tool Corp., Roslyn Heights, N.Y., which makes Swiss-style automatic lathes.

Besides looking at how others can make things easier for them, shops that perform Swiss machining can take actions to make things easier on themselves. For one, they can resist the urge to buy the cheapest Swiss machines.

According to Miguel Aponte, application and service engineer for Swiss machine-tool manufacturer Tornos Technologies US Corp., Des Plaines, Illinois, a lot depends on how much shops are willing to spend for their machines.

On the other hand, he noted, if these customers had bought a multi-spindle machine for high-volume production, they could have had one operator running the equivalent of eight less expensive machines. High-end multi-spindle Swiss machines can also run lights-out without any operator, he added.

According to Carlisle, Index is working with a couple of tooling manufacturers on this type of technology. In addition to relieving newer operators of some responsibility for machining conditions, Carlisle believes the technology will improve surface finishes and tool life in Swiss machining operations.

In addition, Garber sees graphics coming to control screens that are similar to what CAM programmers see on their screens. These graphics will be simulations of what is happening inside the machine during cutting operations.

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