Finding the optimal tool measurement method

Repeated measurements of various tools have yielded unimagined insights. 

“For example, we had been measuring the surfaces on the shanks of milling tools using a probe. Despite optimal values for surface roughness R_a, there were repeatedly tools that were pulled out of the hydro-expansion or shrink-fit chucks due to cutting forces. We then measured these visually and arrived at astonishing results,” says Dr. Fuentes. 

The tool manufacturers discovered the measurement results from probing are highly direction-dependent. This applies primarily to the tool shanks and the resulting transferable clamping forces. 

The measurement results obtained by probing are not always comparable with one another and cannot be consistently used to assess roughness. “There are significant differences in tool behavior, even though the averaged and measured roughness depths R_z of several tools match," says Dr. Fuentes. "Based on our experience, we can only adequately assess the relationships between roughness depths and surface behavior in terms of clamping forces and transmissible torques in detail using optical measurement methods and ZOLLER’s »mμFocus« inspection systems.”
 

Unlocking far-reaching benefits 

Optical measurement with the ZOLLER »mμFocus« provides Hufschmied specialists with unprecedented insights into the properties of tool surfaces. For the first time, it is possible to measure and assess roughness over an entire surface, not just along a single line and in a single direction, as is the case with contact measurement. 

The »mμFocus« inspection system uses a light beam to capture an area measuring 1.0 x 0.8 mm at a resolution of 1.3 million pixels. The image of the surface on the color screen displays the height profile at a resolution of 0.3 μm using different colors. This allows the operator to assess the captured and measured surface holistically. For example, on some surfaces, such as the tool shank, a clear directional orientation of the roughness can be identified. “This may be caused by the grinding of the tools,” reports Dr. Fuentes. 

Similar results are also obtained with coated tools using the optical, microscopic measurement method. While the commonly measured arithmetic mean roughness value R_a is uniform across the coating, significant differences are visible in the surfaces measured using the »mμFocus« tool inspection machine. This pertains to both the nature of the height structures and to the roughness depths. Little is currently known about the actual geometric properties of specially coated tools. 

Additionally, microgeometries can only be assessed in general terms using conventional measurement methods. In contrast, the innovative optical measurement method using the ZOLLER »mμFocus« opens up significant opportunities for assessing surfaces with much greater precision and detail.

Driving development forward

Hufschmied is always open to innovation and welcomed ZOLLER’s offer to work with the »mμFocus«. For ZOLLER, the collaboration offers the opportunity to receive feedback on functionality, operation, and measurement results from a tool manufacturer with hands-on experience.

“Together with ZOLLER, we have consistently found suitable measurement methods for our tool production for over 20 years," says Ralph Hufschmied. "For example, we have been working with the »genius« measuring devices for several years. Here, too, our experience and feedback have helped optimize the measuring devices in terms of their features and operation for practical use.” 

Ralph Hufschmied, managing director of the tool manufacturer Hufschmied Zerspanungssysteme GmbH in Bobingen, reports that his company primarily produces custom-optimized tools. “Starting from a standard design, we develop drilling and milling tools that are precisely tailored to the machining conditions, the materials to be machined, and the economic requirements of the manufacturing companies. In this way, we make a significant contribution to optimizing processes,” he explains, outlining the tool manufacturer’s concept. 

Thirty years ago, he and his father founded the company with this idea. Currently, nearly 130 employees at Hufschmied produce high-quality drilling and milling tools on this basis, primarily for materials that are difficult to machine and for unusual machining operations. This includes, for example, trimming and high-precision machining of components made of glass- and carbon-fiber-reinforced plastics for the automotive industry. The tool manufacturer also develops and implements productive and efficient processes and tools for machining high-strength, tough metals, such as titanium-aluminum alloys in medical technology.