Studying the surfaces of parts and materials provides a lot of information about how the overall product will behave, work, resist wear, etc. By studying these surfaces in 3D, researchers and engineers get more comprehensive information as these 3D datasets reveal detailed, unbiased information about surface features such as roughness, step heights, and curvature. As a result, 3D surface measurements provide a more complete picture of a surface's real variations and functional nature than is otherwise possible using subjective naked eye- or fingertouch-based judgments or 2D surface measurement methods.
Continue reading to learn more about 3D surface measurement parameters, techniques, and available instruments. You can also download our 3D Surface Measurement Knowledge Pack for instant, all-in-one access to our most popular 3D surface measurement application notes, webinars, and demos.
Surface profilometry extracts quantitative topographical information—surface roughness, step height, form, and morphology—by measuring surface height (Z) as a function of lateral coordinates X and Y. Common questions that surface profilometry can be used to answer include:
How flat is the sample?
How high are distinct features?
What is the surface roughness over an area?
What is the distribution of defects, voids, or particles?
Each input of surface height data can be a single point, a line scan, or a full 3D area scan. Single-point methods are always probe-based and are commonly seen in coordinate-measuring machines (CMM). Line-scan methods can be either stylus- or optically based. Area-scan methods are always optically based.
Surface profilometry (or surface profiling) methods can be segmented into two main categories: contact and non-contact.
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Surfaces with similar or even identical average surface roughness values (Ra) might have vastly different surface topographies. Three-dimensional standards enable better quantification and differentiation of these types of surfaces.
3D surface parameters also have helped to improve communication and allowed a process control that traditional R parameters could not do alone.
Though there was initially some resistance to using the techniques of 3D surface measurement, this was eventually overcome as R&D engineers took the time to fully understand the advantages of three-dimensional surface analysis and a shift became apparent as these S parameters were employed on more and more drawings and suppliers were being held to those specifications. Modern 3D surface measurement has given engineers, process designers, and quality control professionals a significantly improved toolkit for describing surfaces since three-dimensional measurements uniquely differentiate not only surface shapes but functionalities as well. All of which, ultimately, results in better surface performance.
Worldwide 3D surface measurement parameters (S parameters) were defined in 1991 by the attendees of the first European Consortium Workshop and have since been developed in accordance with ISO standards to complement the traditional 2D metrology R parameters.
3D surface measurement parameters can be divided into four general categories: amplitude, spatial, hybrid and functional.
There are a few techniques that provide a 3D surface representation from a microscope image, including the two key techniques of white light interferometry (WLI) and confocal microscopy, also known as laser scanning confocal microscopy (LSCM).
The principle of operation for each method provides different advantages and disadvantages, yet there are critical advantages to using Bruker's WLI-based 3D optical microscopes over confocal microscopes for certain applications. Key to these advantages is the ability to maintain subnanometer vertical resolution and 0.1 nanometer RMS repeatability, regardless of magnification or field of view.
3D surface measurement (three-dimensional surface measurement) is used by both the industrial sector and scientific community to drive the success of critical research projects, crucial developments, and fundamental productions and process controls.
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