Rotational Measurement Using 3D Profilometry

High resolution profilometry provides accurate surface topography, roughness, and step height measurement. It detects tiny surface features which may not be discernable by the naked eye. Unlike other techniques such as touch probes, the NANOVEA 3D Non-Contact Profilometer measures the surface features without touching the sample. The profilometer analysis software offers a wide range of studies applicable to the unique surfaces.

Surface roughness and texture of the mechanical parts is vital to its end use. Conventional surface profilometry usually scans the sample surface from just one direction. A precise 360° surface inspection of parts with a cylindrical shape is needed to measure detailed surface features from different angles. Such 360° 3D inspection ensures the narrowest tolerances in quality control of manufacturing processes. Moreover, during the service time, wear creates dents, cracks, and surface roughening all over the cylindrical part surface. Surface inspection on one face of the sample may miss important information hidden on the backside.

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The false color view and 3D view of the surface profile of the hose fitting sample are shown in Fig. 2, providing users a tool to easily observe the surface features of the cylindrical sample at different angles.

A line profile is extracted along the longitudinal direction to show a cross-sectional view of the hose fitting contour in Fig. 3. The size of the peaks of the surface shape is fairly uniform. By setting up a tolerance limit value, the analysis software can automatically determine the quality of the hose fitting, allowing users to make a quick and accurate fail/pass decision on the part.

The roughness and uniformity of the part surface play an important role in ensuring its quality and functionality. Fig. 4 presents the local surface morphology of the sample at a high magnification. The surface roughness values and texture direction are calculated and summarized in Table 1. Directional machine marks were created during the sample manufacture. A dent is detected on the sample surface as a local defect.

Conventional profilometry scans sample surfaces from a single, fixed direction. This is only appropriate for measuring sufficiently flat samples, as opposed to cylindrical shapes that require a precise 360° rotation. For an application such as characterizing the helical cutting edge of a tool, a conventional machine would need multiple scans from different angles of the entire part, as well as significant post scan data manipulation. This is often too time consuming for QC applications that only require measurements from very specific regions.

NANOVEA’s rotational stage solves this problem with simultaneous motion control of the lateral and rotational axes. This technique eliminates the time consuming need of measuring the entire part and continuous realignment. Instead, the full circumference of the entire cutting edge can be determined in seconds. All desired angles and features can be directly determined from the scan, with no need for the extensive stitching together of multiple files.

NANOVEA’s chromatic confocal technique offers far greater resolution, down to 2.7 nm, and accuracy than Focus Variation competitors. The raw surface height is measured directly from the detection of the wavelength focused on the surface, with none of the errors caused by Interferometry techniques, no field of view limitations, and no need for sample surface preparation. Materials with extremely high or low reflectivity can easily be measured and very high wall angles are accurately characterized without any issue.

Coupled with NANOVEA’s line sensor, a bar of data up to 4.78mm wide can be captured in a single pass, while moving linearly for up to 150mm in the scanning direction. Simultaneously, the rotational stage can revolve the sample at the desired speed. Put together, this system allows for the creation of a continuous 3D height map of the entire circumference of a cutting edge, with any pitch or radius, in a fraction of the time when compared to other technologies.

In this application, we comprehensively studied the 3D surface features of a hose fitting sample using a NANOVEA ST400 3D Non-Contact Profilometer. We showcase that the NANOVEA 3D Non-Contact Profilometer equipped with a rotation sample stage can accurately characterize the 360° 3D surface morphology of samples with a cylindrical shape. The detailed and precise 360° surface scan provides an ideal tool for quality control and part inspection.

The data shown here represents only a portion of the calculations available in the analysis software. NANOVEA Profilometers measure virtually any surface in fields including Semiconductor, Automotive, Aerospace, Metallurgy, Machining, Biomedical, and others.