Optical metrology for the smallest balls

Palettenmessung kleinster Kugeln mit dem Messmikroskop MarSurf CWM 100 von Mahr

Palette measurement of the smallest balls with the measuring microscope MarSurf CWM 100 from Mahr

The smallest steel balls are a challenge in quality assurance: The super smooth surface reflects and the edges of the ball are hard to detect. To ensure the production quality of the balls, Mahr provides the high-precision optical measuring device MarSurf CWM 100. The 3D measurement system combines a confocal microscope and a white light interferometer with a fully automatic positioning system for palette measurements.

Scratches and unevenness on ball surfaces must be avoided in order to prevent abrasion and rough running, and to minimize frictional resistance. As an application specialist, Mahr offers the optical 3D measuring station MarSurf CWM 100 for the quality assurance of the smallest balls of steel. The high-precision, computer-controlled optical measurement device detects the surfaces of the spheres with sub-nanometer resolution. The 3D measuring system combines a confocal microscope with a white light interferometer. The dimensional assessment of the non-contact optical measurement technology according to DIN EN ISO 25178 provides 2D surface analysis as well as topographical 3D surface analysis. The entire measurement of the area to be measured takes a few seconds to a few minutes, depending on ball size.

In addition to the surface finish, the measurement system also determines the shape or form of deviation such as the effective radius of the sphere. The high-resolution confocal and interferometer lenses, as well as the optics calibrated by Mahr, reliably detect flaws in the surface up to dimensions of approximately 4 nm. The optical measurement technology adapts to the strong reflections of the ball. The confocal microscope of the measuring device also detects a wide range of sloping ball surfaces.

The measurements are evaluated with Mahr software MarSurf MfM: It reproduces the spherical surface corresponding to the measured data. Three-dimensional deviations from the ideal surface can then be determined. The determined parameters Rz, Ra, Sa, Sz, Sp and Sv give all the necessary information on the nature of the surface. These make it possible to optimize and control the production process.

In addition to individual measurements, palette measurements allow ten, twenty or even more balls to be measured fully automatically and very efficiently. Assembly by robot arm (in the sense of the "Smart Factory" Industry 4.0) is also possible. To ensure that the measurements are truly precise, the measuring station rests on a heavy granite base plate but can also be placed on the active vibration damping table MarSurf ADTV 150. This reliable table reduces disturbances arising from moving people or building vibrations, and even enables the measurement accuracy of a measuring room to be reached when located close to production. With the measuring system MarSurf CWM 100, producers increase the quality of their balls and expensive rejects are reduced.


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