Application Note | Large-Area Profilometry
Fast & High Resolution Large Surface Measurement with 3D Profilometry
A Full 3D Scan of a 300 mm Metal Strip in Two Minutes for In-Line Quality Control
Research & Experimental Testing
Duanjie Li
Visual Design & Editorial
Andrew Shore
Introduction
Metal fabrication constructs raw metal materials into machines and structures via various processes, such as cutting, forming, welding and machining. Flatness, roughness and texture of a large metal surface is vital to its end use. Quantitative measurement of the surface texture, consistency, directional patterns and others is critical in improving the fabrication processing and quality control measures.
Importance of Fast 3D Non-Contact Profilometry for Metal Fabrication
Fabrication shops and machine shops often handle large quantities of metal for fabrication. Therefore, a fast and precise measurement of the 3D surface morphology on a large surface is needed to ensure the narrowest tolerances in quality control. It also makes it possible to implement the NANOVEA 3D profilometer in the production/fabrication line to monitor the surface quality of the metal parts in situ. High resolution 3D scans can quickly detect and report any defects such as pits, cracks or extrusions created during the fabrication processes. In addition to metals, virtually any kinds of surfaces fabricated from different materials such as ceramics, plastics and glasses can be measured in a timely fashion by the NANOVEA 3D non-contact profilometer, making it an ideal tool for surface inspection in manufacture/fabrication lines.
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Measurement Objective
In this application, we showcase that the NANOVEA ST500 High-Speed Profilometer equipped with an optical line sensor finishes a full 3D surface scan of a large metal strip (300 mm × 42 mm) in two minutes.
NANOVEA ST500 Large Area
Optical 3D Profilometer
Results and Discussion
As shown in Figure 1, the optical line sensor generates a bright line composed of 192 light spots that scan the sample surface at the same time. This significantly increases the scan speed and enables a detailed 3D scan of a 300 mm × 42 mm Al strip in two minutes. Such a fast speed makes it possible to implement the NANOVEA 3D profilometer into the production line for quality control of the metal strips in situ.
As displayed in Figure 2, the False Color View exhibits the general morphology of the whole Al strip. It possesses a slightly lower center and elevated edges. Fine parallel machine marks exist along the longitudinal direction. Figure 3 shows the False Color View and 3D View of the Al sample at a larger magnification, which provides users an ideal tool to directly observe the surface morphology from different angles in detail and to evaluate the shape, flatness and roughness of the Al strips for the purpose of quality control.
Using the powerful analysis software, we can easily obtain 2D profiles of the metal strip at different locations and directions as shown in Figure 4. It allows further investigation on the shape, texture and possible defects, e.g. cracks and pits, of the metal strip. Figure 5 and Table 1 show the roughness and texture isotropy analysis on the metal strip as examples. Close monitoring of the evolution of the surface roughness, texture, consistency, directional patterns and other values ensures quality processing and control measures. Quantifiable and reliable surface inspection reports failing products in a timely fashion once the threshold values such as roughness are exceeded.
| Parameter | Value |
|---|---|
| Sa | 4.17 µm |
| Sq | 5.21 µm |
| Sp | 80.9 µm |
| Sv | 20.1 µm |
| Sz | 101 µm |
| Ssk | −0.0812 |
| Sku | 3.89 |
| Isotropy | 0.400 % |
| First direction | 0.288° |
| Second direction | 5.22° |
| Third direction | 175° |
Table 1: Roughness (ISO 25178) and texture isotropy of the Al strip (from Fig. 5).
Conclusion
In this application, we showcase that the NANOVEA 3D Non-Contact Profilometer equipped with an optical line sensor finishes a high resolution 3D profilometry scan of a large metal strip in two minutes. The axial chromatism technique allows measuring the sample surface without touching, making it possible and simple to implement the NANOVEA profilometer in the metal production/fabrication line so as to monitor the surface quality in situ. The analysis software provides useful measurement tools such as roughness and texture analysis.
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, Microelectronics, Solar, Fiber Optics, Automotive, Aerospace, Metallurgy, Machining, Coatings, Pharmaceutical, Biomedical, Environmental and many others.
Frequently Asked Questions About Large-Area Surface Measurement
Why measure large metal surfaces quickly?
Fabrication and machine shops handle large quantities of metal; fast, precise 3D measurement of large surfaces keeps tolerances tight and makes in-line monitoring possible, detecting pits, cracks or extrusions as they occur.
How long did the scan take?
The line sensor projects 192 light spots at once and finished a detailed 3D scan of a 300 mm × 42 mm aluminum strip in two minutes.
What did the scan reveal?
The strip had a slightly lower center and elevated edges, with fine parallel machine marks along its length; profiles along and across the strip characterize shape, texture and defects.
What roughness did the strip have?
Sa 4.17 µm and Sq 5.21 µm (ISO 25178), with a texture isotropy of 0.400 % and a main direction of 0.288°, following the machining marks.
Can roughness thresholds trigger rejection?
Yes. Quantifiable surface inspection reports failing products in a timely fashion once threshold values such as roughness are exceeded.
Which materials can be measured?
Metals, and virtually any surface of ceramics, plastics or glass, without contact.
