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In manufacturing and mechanical engineering, flatness is an important geometric condition for workpieces and tools. Flatness is the condition of a surface or derived median plane having all elements in one plane. [1] Geometric dimensioning and tolerancing has provided geometrically defined, quantitative ways of defining flatness operationally.
A surface plate is a solid, flat plate used as the main horizontal reference plane for precision inspection, marking out (layout), and tooling setup. [1] The surface plate is often used as the baseline for all measurements to a workpiece, therefore one primary surface is finished extremely flat with tolerances below 11.5 μm or 0.0115 mm per ...
Surface metrology is the measurement of small-scale features on surfaces, and is a branch of metrology. Surface primary form, surface fractality, and surface finish (including surface roughness) are the parameters most commonly associated with the field. It is important to many disciplines and is mostly known for the machining of precision ...
Critical dimensions as step, curvature, flatness are computed from the surface topography. While the historical notion of a profilometer was a device similar to a phonograph that measures a surface as the surface is moved relative to the contact profilometer's stylus , this notion is changing with the emergence of numerous non-contact ...
Therefore, because both surfaces have some irregularities, there are few ways to know the true, absolute flatness of any optical flat. The only surface that can achieve nearly absolute flatness is a liquid surface, such as mercury, and can sometimes achieve flatness readings to within λ/100, which equates to a deviation of only 6.32 nm (632 nm ...
A typical range of surface roughness that can be obtained without resorting to special equipment would fall in the range of 1 to 30 units Ra (average roughness), usually microinches. Surface accuracy or flatness is usually measured in units of helium light band (HLB), one HLB measuring about 280 nm (1.1 × 10 −5 in). Again, without resort to ...
Surface roughness can be regarded as the quality of a surface of not being smooth and it is hence linked to human perception of the surface texture. From a mathematical perspective it is related to the spatial variability structure of surfaces, and inherently it is a multiscale property.
Flatness measurement of granite surface plates, for example, can be performed by measuring straightness of multiple lines along the flat surface, then summing the deviations in line angle over the surface. Recent advancements in applications allow angular orientation measurement of wafers. This could also be done without obstructing lines of ...