Thicknesses

Thicknesses refer to the measurements of the distance between two parallel surfaces of an object, often expressed in units such as meters, millimeters, or inches. It is a fundamental dimensional parameter in engineering, manufacturing, and quality control, and can describe a single uniform value or a spatial variation across a part. In practice, thicknesses may be specified as nominal, with tolerances indicating allowable deviation, and as minimum or maximum values for critical regions.

Common measurement methods include contact devices like calipers and micrometers for simple parts, and specialized thickness gauges for coatings. Non-contact and non-destructive techniques are also widely used, such as optical profilometry, ultrasonic thickness measurement, eddy current testing, and X-ray radiography. The choice of method depends on the material, surface condition, thickness range, and whether the part is hollow or opaque.

Applications span metal sheets and foils, plastics, glass, coatings and paints, films and laminates, printed circuit boards, and semiconductor wafers. For coatings and protective layers, thicknesses are critical for performance and must conform to specified tolerances in drawings and standards. Thickness uniformity affects mechanical fit, sealing, optical properties, and structural integrity; large or systematic variations can indicate processing faults, wear, or improper calibration.

Factors influencing thicknesses include manufacturing processes (rolling, extrusion, casting), finishing operations, wear and corrosion, and thermal expansion or contraction. Standards organizations such as ISO, ASTM, and DIN provide guidelines for measurement procedures, tolerances, calibration, and reporting. Accurate determination of thicknesses relies on proper instrument calibration, appropriate method selection, and routine verification.