Turning microparts demands the most productive machine tools possible
by Jim Barnes
Microparts turning is a fluid, changing business and you have to keep an eye on margins to succeed. Stay aware of the technology options open to you. In this demanding environment, Swiss machines are earning renewed attention and finding wider application as they evolve.
“With so much Swiss technology out there, it’s hard even to say ‘Swiss’ anymore. But those small, Swiss-style sliding headstock machines have got so much capability,” says Ron Gainer, regional sales manager, Tsugami/Rem Sales, Windsor, CT.
Today’s machines are faster and provide more capability, including additional axes. “Years ago, parts required a secondary operation to be completed. You had to take the part off one machine and put it on another capable of milling or off-centre drilling,” says Bill Papp, regional sales manager, Hanwha Machinery America, Inc., Franklin, WI. “Now, the first machine has the capability of doing
all of that.”
The machines bring considerable sophistication to the table. One machine from DMG MORI ELLISON in Canada has up to 10 axes and more than 46 tool stations available, notes Roberto Colombo, application manager, Mississauga, ON.
Big small parts
Swiss machines are renowned for handling small parts. Today, there is a growing demand to apply the technology to larger, small parts due to its flexibility and productivity.
“The smallest diameter machine we have is 3 mm,” says Papp. Typical parts of this size include medical and dental implants. “We go up to 38 mm,” he adds, noting a growing demand for parts between 32 and 38 mm.
Gainer estimates the biggest segment of the market is 20 mm, but the machines go up to an inch and a half. Colombo notes that DMG MORI Swiss machines have a bar capacity of as much as 42 mm.
However, Swiss machines really shine on smaller parts. “There are a lot of miniature parts out there, where people are working with 1/16 and 1/8-in. dia. stock,” says Gainer. “You can’t run that kind of stock on a regular lathe.”
“In general, a Swiss lathe is 30 to 35 per cent more productive than a conventional turret lathe,” says Colombo. The machine’s size gives you higher speeds and reduces positioning time. The machine layout, with gang tool racks, allows very fast chip-to-chip time. These factors combine to make a Swiss lathe a solid choice for medium-to-high volume production, according to Colombo.
Some new users are surprised by a Swiss machine’s ability to remove stock in one pass. For example, a cross-drilling operation may well require a little more rigidity. “You might start with a quarter-inch stock, even though you’re making a part of an eighth-inch diameter,” says Gainer. “We’re often making a really small part of larger stock, just because we need a little more rigidity in the setup.” A Swiss machine will take the extra material off quickly.
Tooling alternatives are expanding, too. “In the past, sometimes you had to go to a turret machine to get the number of tools you needed,” Gainer adds. “You don’t need to do that anymore. The machines are evolving to where they have higher capabilities.”
Work-handling requirements for Swiss machines are low. “They are designed for production, so more than 90 per cent of applications require a bar feeder so the work handling is very low,” says Colombo.
In fact, the machines are well-suited to lights-out manufacturing. “Just make sure the bars are loaded in the automatic bar loader. If anything goes wrong, the machine shuts off and can notify someone that it is down,” says Papp.
ROI obviously depends on the part and the programming. Swiss machines are usually more expensive than other turning machines and there might be costs beyond the purchase price. “You can add high-pressure coolant if the part needs it, possibly an automatic bar loader, a shift conveyor and a mist collection system,” says Papp. That total investment could easily be in the $200,000 range.
But as Papp explained to one customer, “every time you’re cutting off a part, you’re making $75. Add up the parts to calculate your return on investment.”
Three-year paybacks are not uncommon, notes Colombo.
Tooling and programming
It is possible to use almost the same tools and collets available for a conventional lathe in a Swiss machine, says Colombo.
“You’re not necessarily using the chip breaker of the insert that was designed for fixed-head machining in the same fashion,” says Gainer. “We are generally going to stay with sharper tools and peel that material away. Our surface footage is roughly based on the bar diameter.”
The machines offer higher spindle speeds than some users may be accustomed to. “Because of the size of the lathe, our Sprint line can reach 10,000 r.p.m. This speed is nearly impossible to get with a conventional lathe,” says Colombo.
Another difference with a Swiss machine is that the part is moving. “As you’re moving the bar, which is the Z axis, you might have another tool chasing that part around and doing a separate operation,” says Gainer. “The process is different, but the programming is very similar. The difference is where you have multiple programs running at the same time. But that’s happening in the multi-axis world, too. Programming-wise, it’s not that different.”
“Programming is always the same,” says Colombo. “The difference consists in having more options and functions available in a sophisticated machine.” He suggests that CAD/CAM software can simplify programming and simulate the process.
“The Swiss market is a growing market. We’re still educating new customers who want to get into this technology. If they don’t invest, somebody else is going to take that small parts business away from them,” says Gainer. SMT
Jim Barnes is a contributing editor. [email protected]