Application Note | Leather Surface Inspection
Processed Leather Surface Finish Measurement Using 3D Profilometry
Quantifying Roughness and Dimple Depth, Pitch, and Diameter to Compare Leather Finishing Processes
Research & Experimental Testing
Craig Leising
Visual Design & Editorial
Andrew Shore
Introduction
Once the tanning process of a leather hide is complete the leather surface can undergo several finishing processes for a variety of looks and touch. These mechanical processes can include stretching, buffing, sanding, embossing, coating etc. Dependent upon the end use of the leather some may require a more precise, controlled and repeatable processing.
Why Profilometry Inspection Matters for Leather R&D and Quality Control
Due to the large variation and unreliability of visual inspection methods, tools that are capable of accurately quantifying micro and nano scales features can improve leather finishing processes. Understanding the surface finish of leather in a quantifiable sense can lead to improved data driven surface processing selection to achieve optimal finish results. NANOVEA 3D Non-Contact Profilometers utilize chromatic confocal technology to measure finished leather surfaces and offer the highest repeatability and accuracy in the market. Where other techniques fail to provide reliable data, due to probe contact, surface variation, angle, absorption or reflectivity, NANOVEA Profilometers succeed.
ℹ️ Learn more about non-contact profilometry lab services for leather and textiles.
Measurement Objective
In this application, the NANOVEA ST400 is used to measure and compare the surface finish of two different but closely processed leather samples. Several surface parameters are automatically calculated from the surface profile.
Here we will focus on surface roughness, dimple depth, dimple pitch and dimple diameter for comparative evaluation.
NANOVEA ST400 Standard
Optical 3D Profilometer
Results: Surface Roughness
Sample 1
Fig. 1: 3D view and false color view of Sample 1.
Sample 2
Fig. 2: 3D view and false color view of Sample 2.
| Parameter | Sample 1 | Sample 2 | Unit |
|---|---|---|---|
| Sa | 13.722 | 14.497 | µm |
| Sq | 16.361 | 17.458 | µm |
| Ssk | −0.230 | −0.263 | |
| Sku | 2.302 | 2.418 | |
| Sp | 55.453 | 68.375 | µm |
| Sv | 64.160 | 56.570 | µm |
| Sz | 119.613 | 124.945 | µm |
| Sdar | 18.642 | 18.943 | mm² |
| Spar | 9.000 | 9.000 | mm² |
Table 1: ISO 25178 height parameters and other 3D parameters of the two leather samples.
Results: Dimple Statistics
Depth Comparative
Pitch Comparative
Mean Diameter Comparative
Conclusion
In this application, we have shown how the NANOVEA ST400 3D Profilometer can precisely characterize the surface finish of processed leather. In this study, having the ability to measure surface roughness, dimple depth, dimple pitch and dimple diameter allowed us to quantify differences between the finish and quality of the two samples that may not be obvious by visual inspection.
Overall there were no visible differences in the appearance of the 3D scans between Sample 1 and Sample 2. However, in the statistical analysis there is a clear distinction between the two samples. Sample 1 contains a higher quantity of dimples with smaller diameters, larger depths and smaller dimple-to-dimple pitch in comparison to Sample 2.
Please note that additional studies are available. Special areas of interest could have been further analyzed with an integrated AFM or Microscope module. NANOVEA 3D Profilometer speeds range from 20 mm/s to 1 m/s for laboratory or research to meet the needs of high-speed inspection; can be built with custom sizing, speeds, scanning capabilities, Class 1 clean room compliance, indexing conveyor or for in-line or online integration.
Frequently Asked Questions About Leather Surface Finish Measurement
Why measure the surface finish of leather?
After tanning, leather can undergo several finishing processes, such as stretching, buffing, sanding, embossing and coating, for a variety of looks and touch. Visual inspection varies widely and is unreliable, so tools that accurately quantify micro and nano scale features support data driven selection of surface processing to achieve optimal finish results.
How is leather surface finish measured without contact?
NANOVEA 3D Non-Contact Profilometers use chromatic confocal technology to measure finished leather surfaces. They succeed where other techniques fail to provide reliable data because of probe contact, surface variation, angle, absorption or reflectivity.
Which parameters describe a processed leather surface?
ISO 25178 height parameters such as Sa, Sq, Ssk, Sku, Sp, Sv and Sz, plus the developed area Sdar, together with statistics of the dimples: depth, pitch and mean diameter. Here Sample 1 measured Sa 13.722 µm and Sample 2 Sa 14.497 µm.
Can 3D profilometry tell apart leathers that look the same?
Yes. There were no visible differences between the 3D scans of the two samples, but the statistical analysis showed a clear distinction: Sample 1 contained more dimples, with smaller diameters, larger depths and a smaller dimple-to-dimple pitch than Sample 2.
Can leather inspection be automated on a production line?
NANOVEA 3D profilometer speeds range from 20 mm/s to 1 m/s, from laboratory and research use to high-speed inspection, and systems can be built with custom sizing, speeds and scanning capabilities, Class 1 clean room compliance, indexing conveyors or for in-line or online integration.
Which NANOVEA instrument was used for leather surface analysis?
The NANOVEA ST400 3D Non-Contact Profilometer. Special areas of interest can be analyzed further with an integrated AFM or microscope module.
