The cutting programs at Liechti Engineering operate at their limits. If a toolholding system is used, it must operate flawlessly with maximum efficiency under these specified requirements.

Toolholding Pushes the Limits of Precision Machining

Jan. 26, 2015
Milling machine builder relies on REGO-FIX powRgrip toolholders for precision and performance Liechti’s specialty material expertise Single-clamping profile machining Mechanical clamping in under 10 seconds Understanding predicted behavior

Process reliability is very important to Liechti Engineering, a family-owned designer and manufacturer of milling and machining centers. It also develops CAM software for machining complex, curved aerodynamic profiles. To deliver machines that guarantee reproducibility and help customers to maximize production efficiency and tool life, the company relies heavily on toolholders that can meet the high demands of precision and performance.

Headquartered in Langnau im Emmental, Switzerland, Liechti Engineering has developed a global customer base for its precision flow profiles on turbine components. That success has been based on its expertise in machining materials like titanium, Inconel, Nimonic and high-alloy steels, and Liechti has established a niche offering overall solutions to customers in the power generation and aviation sectors. This includes well-known brands like Alstom, General Electric, Pratt & Whitney, Rolls-Royce, and Siemens.

The test milling tool is a finish milling tool with a 0.7874-in. (20-mm) diameter.

Liechti also is known for developing specific profile machining technology that allow its milling machines to machine complex parts completely in a single clamping operation, including highly dynamic roughing and finishing processes. This single clamping reduces chucking errors, set-up costs, and overall machining times by up to 30 percent. It also means dramatic increases in production efficiency and for of the turbine blades, impellers, and blisks.

The success of this technology and the single-clamping operation hinges on a tool clamping system that operates with maximum efficiency, can tolerate high-speeds, reduces wear and tear on tools, and operates flawlessly, even when cutting programs are pushed to their limits. For years, Liechti has relied on powRgrip, a revolutionary toolholding system from REGO-FIX specifically designed for precision and performance in high-speed machining.

The powRgrip system is unique in that it uses the mechanical properties of the holder instead of heat to generate high clamping force, improving safety and allowing tools to be changed immediately after machining. It takes less than 10 seconds to press in or remove a tool from the holder, and it achieves an extremely high level of vibration damping resulting in less tool wear.

“We recommend to our customers the system that is best suited for constructing a workpiece, and in most cases, it’s the powRgrip system,” said Simon Trummer, senior CAM application engineer at Liechti Engineering. “Not only do the damping characteristics of the powRgrip system ensure a flawless surface quality, but REGO-FIX has been a reliable partner for many years.”

Free-form surface wear on the milling tool with powRgrip System (left); free form surface wear on the milling tool with comparable dimensions (right.)

Trummer also emphasized the importance of understanding the predicted behavior of the tool when manufacturing turbine blades to ensure their quality. As part of its design engineering process, Liechti regularly conducts comparison testing in its lab.

One test compared the powRgrip system with other toolholder systems using a 5-axis dynamic milling machine during the finishing passes on a 420A stainless steel blade.  Each toolholder assembly was 6.25 in. (~189 mm) long, with a constant feedrate of 281 in./min. (~7.1 m/min) with through tool and peripheral cooling for one hour.  Following the tests, the tools were viewed under a microscope.

“Using the microscope, we can precisely determine the behavior of the wear on the tool over the machining cycles, and discovered that the powRgrip system clearly outperformed the other systems we use in-house,” Trummer explained.

Years of experience, reinforced by the results of this test, give the team at Leichti great confidence in recommending powRgrip to its customers, who depend on flawless surface quality to create efficient turbines. Trummer added that in addition to reliability, customers benefit from extended tool life. “When switching to the powRgrip system, our customers always save significant sums of money when purchasing the cutting tools.”

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