No guide bushing? No problem with new Swiss turning machine

For a company to remain competitive in the United States, it must stay in the technological lead, and this is especially true in metalworking and machining.

Many manufacturers still employ old cam systems; the work, but are they running smart? To become more profitable, American shops should invest in technology that will not only produce better parts, but do it faster, and with less downtime.

One area of machining where an immense leap in productivity can easily be achieved is the field of turned parts. Generally made from bar stock – though occasionally crafted from coil – parts produced on so-called Swiss turning machines have medical, automotive, and precision applications, among others.

Tornos is a  leader in the Swiss turning industry. Established in 1880, the Moutier, Switzerland-based company has extensive US operations, including three Centers of Excellence in Connecticut, Illinois, and California. These facilities have been constructed with the sole purpose of keeping Tornos in closer contact with its customers. Because of their central locations and extended hours of operation, the Centers for Excellence provide customers with faster parts delivery times, more responsive customer service, and increased access to training and application specialists and local machine demos.

“These facilities represent the values of the Tornos brand worldwide,” says Scott Kowalski, president of Tornos US. “They are Centers of Excellence in terms of performance, productivity, and teamwork.”

The pursuit of excellence also goes into the design and manufacture of Tornos machines, which are on the cutting edge of technology. One of Tornos’ goals is to keep its partner companies on the cutting edge as well.

But one look at Tornos’ sliding headstock Micro 8, and it is apparent that something is very different, especially the bar feeder.

Unlike most Swiss turning machines – including those in Tornos’ own line – the Micro 8 has a left-hand feeder. In itself, this might not seem all that unusual. But then, something else is missing: the Micro 8 does not have a guide bushing, which ordinarily acts as a chuck to keep the bar stock on the proper path.

“Many of the old cam-operated Swiss machines allowed an operator to remove the guide bushing to produce short, tight-tolerance parts,” says Tornos US national product manager Leonard Lanute. “Many parts being turned today can be machined faster, cheaper, and with tighter tolerances on a non-bushing machine.”

The Micro 8 is remarkably precise, boasting tolerance results of 1.4 µ in production. That’s because while it might lack a guide bushing, its spindles and tools move along rather rigid guide rails to guarantee machining stability.

Built to turn parts up to 8 millimeters in diameter – hence Micro 8 – the single-spindle machine respects the traditional 3:1 length to diameter ratio of the short, tight-tolerance parts made by the cam-operated machines it is intended to replace, and does so while operating without clearance. This makes it ideal for any number of precision parts – especially those with medical or dental applications – that need to be competitively priced. But it can also turn a 3/8-in. diameter part that is up to 12 in. long. That’s a 32:1 depth-to-diameter ratio.

“To turn longer parts,” Lanute said, “you have to think differently. You want to get creative and make the machine as productive as possible.”

With bigger parts or the precision ones needed for an application like watchmaking, a portion of the increase in productivity is the direct result of the shorter bar remnant that results when guide bushing is removed. According to Tornos, the average remnant on a conventional Swiss turning machine is 7 in., as opposed to just 2 in. on the Micro 8.

“Just think of how many more parts you can make,” Lanute says, before pointing out that having to change bars less frequently will save time and money. “If it takes 45 seconds to do a bar change, over the course of a week, month, or year, that’s a lot of idle time.”
Of course, convincing watchmakers and the medical and dental set that using a non-bushing machine could increase their productivity and the quality of their parts takes some doing, says Lanute. That a guide bushing can be eliminated, and tolerances still made tighter, is a difficult concept to grasp.

“But we worked with a few of our watchmaking customers and had them try the nonbushing machines, and on the short parts these machines fit such a niche in the watchmaking industry that they’re becoming the standard now,” says Lanute. “The watchmakers looked at the process and realized the value, saying, ‘We should have done this years ago.’”

The Micro 8 has two entirely independent and identical tool systems, enabling workpieces of the same complexity to be machined simultaneously on front and back working tools. With 20 total tools, five simultaneous axes, and a maximum rotational speed of 15,000 rpm, cycle times on it can be as quick as six seconds for shorter, simpler parts.

“Bushingless machines don’t require ground stock and they are a lower capital investment as well,” says Lanute. “And because bushingless design reduces accumulated error due to fewer moving parts, we’re able to hold microns.”

And holding microns will help any company grab hold of new business, which is exactly what Tornos had in mind for its customers when it designed the unorthodox Micro 8.