October 2007 Edition

flexible production

Creating top scopes for rifles calls for high-precision turning

Leupold & Stevens (L&S), Beaverton, OR, is the premier U.S. designer and manufacturer of sport optics and tactical optics. Its hand-assembled rifle scopes typically have more than 60 parts each, including the lenses. When the scopes leave the factory, they look like jewels and carry a lifetime warranty.

A typical array of the rifle scopes machined by Leupold & Stevens

Customers typically own seven L&S products.

To create such a masterpieces, the 100-year-old company invests in machines as well as people. (Most of its 675 employees have been with the company for more than 10 years.) With regard to successful precision machining, L&S operates more than 30 INDEX machines, primarily multifunction turning machines used to produce the bodies and tubes for the scopes from aircraft-quality aluminum.

L&S bought its first INDEX in 1957, a cam-operated turret machine, to make scope tube parts. Since 1989, 90 percent of its machine inventory has become CNC, including four INDEX CNC multispindle machines. L&S also has on its floor INDEX ABC turning machines, G 200, G250, and G300 multifunction turn-mill machines. It is a sea of INDEX blue-green turning, milling, drilling, and tapping more than 1,000,000lb of aluminum each year. Tolerances in some applications are less than 0.0005"; most always at least ±0.002".

Leupold's partnership

"There is a technological partnership between INDEX and Leupold that has helped both sides develop their respective products," observes John Karge, manufacturing engineering supervisor at L&S. Employees on both sides work together in a mutually respectful and productive way, according to both companies. That forms a foundation for many improvements in the machines and processes. And with literally hundreds of products and variants, the challenge to improve is always there.

'We provide the means to help our customers provide high volumes of precision parts with the least lost time possible, going beyond the machine to include parts, service, tool management, rapid changeovers, and efficient tool layouts,' points out Olaf Tessarzyk, INDEX chairman and CEO.

Nearly 600 different parts go across the 30 INDEX machines. Average setup time is 4hr, including time for the CNC multispindles. Each machine produces about 20 different parts. Typical runs require a machine to be set up once or twice a week, sometimes four times, so L&S has worked hard to pare changeover times to a minimum.

Typically, the large end of the scopes are machined, then a special chuck swallows the large end of the workpiece, and the back end of the scope is milled and drilled with tools from the counterspindle.

"Our WIP turns have increased and our inventory has decreased, so we have very few parts sitting around. One of our goals is to keep the machines cutting, not sitting idle while they are being setup" says Dave Sonsteng, L&S parts manufacturing manager.

One way Leupold keeps the machines producing good parts is through the INDEX Tool management system and preset tooling. A Zoller presetting system is used to measure all tooling. Tool data and programs are then downloaded directly to each of the machines on the floor.

The tool management system keeps a library of up to 200 tools at each machine and maintains all the relevant tool data, including measurements. Once the tools are though the tool crib, they typically don't return. Inserts are maintained by the setup people and storage remains at the machine in preparation for the next run.

Above: The INDEX G300s have the capacity to turn lengths up to 49" (1,250mm), allowing L&S to machine a range of 7" to 13" scope bodies in one cycle.

Another key to keeping the machines producing parts at L&S is through the use of the INDEX P200 Programming System. This system organizes programs and tooling for each machine on the production floor. Programming and tool preparation is done offline well prior to shutting a machine down for setup, minimizing downtime.

Once set up, the P200 System manages the operation, and automatically provides the dialogue programs for the machine setup.

To setup each part, the operator presses "cycle start" and looks at the tool list on the screen, reaches into a drawer, chooses the correct preset tool, and inserts it into the machine spindle or turret. It takes only 15min. This way, the machine is ready to turn perfect parts the first time. There is no time wasted in trial cuts.

Process control on the machine is also evident at L&S. The reliability of the process on each machine is monitored closely, so unacceptable parts are not produced.

Creating the process

Right: Parts being gently removed from the machine

When a unique part or ­process idea comes to Karge, he ­begins to think about how best to make it. He consults with INDEX engi­neers, gets their input, and adds his considerable experience to the mix, including at times adjusting the part design to get the most cost-effective method. It takes a partnership to develop a process that is cost-effective and that is user-friendly, Karge observes.

"In 1995, we went to INDEX to test main tube machining methods on different machines," says Karge. "That led to the purchase of four G300's. They have been doing the job for 12 years now. That got us into the one-piece main tube production." L&S is still successful in creating robust, high quality two-piece main tubes using other INDEX machines as well.

Today, L&S has honed its expertise at machining long, thin-walled parts, and it has become one of the company's most valuable capabilities. But not without the development of the process with the INDEX RatioLine G300 multitasking turn-mill center.

The INDEX G300s, with the capacity to turn lengths up to 49" (1,250mm), have allowed L&S to machine a range of 7" to 13" scope bodies in one cycle. Identical main and counterspindles with up to three turrets permit simultaneous machining of several features of the aluminum workpieces, resulting in minimum cycle times. A Y/B axis permits inclined, off-center drilling and milling. Typically, the large end of the scopes are machined, then a special chuck swallows the large end of the workpiece, and the back end of the scope is milled and drilled with tools from the counterspindle.

The INDEX G300s, with the capacity to turn lengths up to 49" (1,250mm), have allowed L&S to machine a range of 7-13" scope bodies in one cycle. Identical main and counterspindles with up to three turrets permit simultaneous machining of several features of the aluminum workpieces, resulting in minimum cycle times. A Y/B axis permits inclined, off-center drilling and milling.

"The INDEX part-handling system and the fact that the parts can be removed gently from the machines is a very important factor for us," Karge insists.

The six independent spindle motors of the INDEX Multispindle CNC machine allow optimum cutting speeds for each tool. Two CNC tool slides work with each spindle and can use quick change pre-settable OD, ID, or live tools.

The INDEX RatioLine CNC turn-mill machines are considered models of capability. In addition to the identical main and counterspindles with up to three tool carriers, the machines include a milling spindle with its own tool magazine. A gantry workpiece receiving attachment for workpiece loading and unloading makes automated handling practical.

According to INDEX, the turn-mill centers allow extremely efficient and flexible low volume production of simple to complex parts. The modular design enables the use of customized manufacturing configurations, resulting in lower investment costs and efficient machine utilization.

The combination of the INDEX machine capabilities and the processing expertise of the engineers at L&S are two major factors in the success of optics manufacturer. But there is one more important factor. Both companies benefit from having a similar culture, according to Sonsteng.

"The culture of the two companies is similar in our dedication to providing quality products and service to the customer," Sonsteng says, "and that has helped to strengthen our relationship and provide an advantage to us."

"We provide the means to help our customers provide high volumes of precision parts with the least lost time possible, going beyond the machine to include parts, service, tool management, rapid changeovers, and efficient tool layouts," points out Olaf Tessarzyk, INDEX chairman and CEO. "It is gratifying to see an American manufacturer make good use of all these tools to become a world leading producer in its space." INDEX Corporation, www.rsleads.com/710tp-152

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