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Surface roughness test measure microscopic peaks/valleys on materials to quantify texture (using contact stylus or non-contact optical/laser methods). Key metrics like Ra (average roughness) and Rz (max height) ensure quality control, compliance (ISO 4287), and performance in automotive, medical, and semiconductor applications.
A surface roughness tester is an analytical instrument designed to quantitatively measure the surface texture and roughness of materials. It is widely used for quality control, process evaluation, and research in fields such as manufacturing, materials science, and engineering. Surface roughness testers provide precise, repeatable measurements of surface irregularities, enabling users to assess the functional and aesthetic properties of machined, coated, or treated surfaces.
The working principle of surface roughness testers (profilometers) relies on tracing surface topography and converting physical variations into quantifiable parameters. Two primary methods are used: A diamond-tipped stylus (2–5 μm tip radius) physically traces the surface. Vertical movements of the stylus are converted into electrical signals via a piezoelectric transducer or linear variable differential transformer (LVDT). As the stylus moves horizontally at a constant speed (typically 0.1–1 mm/s), it detects height deviations (peaks/valleys).
Possibly wrong cutoff (λc). For Ra=0.8 μm, use λc=0.8 mm
Low force stylus (≤0.2 mN). Optical profilometry for 100% non-contact (but avoid reflective surfaces).
Human touch senses Rsk (skewness). Negative Rsk = "smooth" (peaks worn); positive Rsk = "scratchy" (sharp peaks).
Ra: General manufacturing (ISO 1302). Rz: Automotive or gears (ISO 13565). Rq: Optics or lasers (ASME B46.1).
This investigates the effect of different cutoff lengths on the surface roughness measurement of a non-periodic ground sample. The provided image shows the surface profile curves and corresponding Ra values for the same sample (nominal Ra = 0.408 μm) measured at four different cutoff lengths: 0.08 mm, 0.25 mm, 0.8 mm, and 2.5 mm. As the cutoff length increases, the surface profile reveals more detailed features, and the measured Ra value rises from 0.165 μm to 0.410 μm, gradually approaching the nominal value. This demonstrates that the choice of cutoff length significantly influences the roughness results, with larger cutoff lengths providing measurements that better reflect the actual surface characteristics of non-periodic samples.
This examines the influence of different cutoff lengths on the surface roughness measurement of a periodic sample. The provided image displays the surface profile curves and corresponding Ra values for a milled sample (nominal Ra = 0.408 μm) measured at cutoff lengths of 0.08 mm, 0.25 mm, 0.8 mm, and 2.5 mm. Unlike the non-periodic case, the Ra values in the periodic sample fluctuate more noticeably with changes in cutoff length, reflecting the periodic features of the surface. The measured Ra values do not consistently approach the nominal value as the cutoff length increases, highlighting that the selection of cutoff length can lead to significant variations in roughness results for periodic surfaces. This underscores the importance of choosing an appropriate cutoff length to accurately characterize the surface roughness of periodic structures.
