Very often, mechanical designs for workpieces include specifications for defined parameters such as roughness or ripple. Polytec white-light interferometers acquire entire 3D profiles in just seconds, where tactile methods would require much longer measuring times. Such parameters – take the percentage contact area or frequency distributions, for example – can be determined quickly and easily. Roughness can be optically determined too, but the values can deviate from the results of tactile measurements to which the drawing dimensions and standards often refer. However, new guidelines for calibrating white-light interferometers give the user the assurance that the measured values can be traced back to calibration standards. Optical measurements also make roughness parameters available. Often, for instance, it is sufficient to decide whether the surface of e.g. dynamic sealing surfaces is too rough – which would lead to high friction losses – or too smooth, which could result in excessive adhesion.
Determining parallelism, flatness, radii, steps, angles and other parameters with nanometer precision are typical tasks. The areas to be examined are often situated in subjacent holes or differ a great deal in terms of height. But this is an easy task for Polytec’s systems in contrast to other optical measuring methods, such as coherent interferometry. In many cases, the complete topography of a workpiece or object has to be checked. Ceramic components, imprints, safety features and even forensic evidence can be analyzed with nanometer accuracy using white-light interferometry. Also, the demands placed on the warping and deformation of components such as printed circuit boards are forever growing as dimensions continue to shrink.
Flatness and parallelism
Flatness often plays a major role for functional surfaces, with examples including components with sealing surfaces used in pressure and vacuum technology, as well as transparent films for displays, semiconductor elements, metal surfaces and ceramic surfaces. Determining percentage contact areas is a simple and reliable process too. In this context, the TopMap systems allow you to measure entire surface areas with a large field of view and thus get fast, complete characterization of a workpiece.
Heights and steps
A large vertical adjustment range is often the key to determining parallelism, height differences or angles between several surfaces. The TopMap series offers adjustment ranges of up to 70 mm, or 50 mm that can be used to measure surfaces that are separated from one another by large steps or are situated inside holes. The TopMap surface metrology systems use a telecentric light beam path that avoids shadowing effects, allowing to reach all areas even in deeply recessed holes.
In research, development and production, the exact and repeatable measurement of surface roughness is often decisive for maintaining required tolerances and for smooth production processes. Also durability, reliability and functional fulfillment of final products directly depend on surface roughness. The determination of surface roughness is decisive for the characterization of the surface condition, like in dental implants, sealing surfaces or surfaces for certain painting and coating processes. Some applications even depend on the simultaneous determination of form deviation and roughness.
Microstructures are very small structures, which are very often limited in their functionality even with the smallest damage. Physical effects on the microsystem measurement objects should be avoided. Therefore, another important aspect of surface characterization in the field of microsystems technology is the contactless and thus non-destructive testing of surfaces. Polytec's topography measurement systems are the optimal choice for measuring microstructures due to the optical measurement method without wear and tear and without the resulting scrap.
Tribology and wear
Determining the amount of material removed plays a key role when it comes to wear measurements. In this situation, the surfaces are often very jagged and the light reflected back shows great intensity differences. The innovative Smart Surface Scanning technology incorporated into the TopMap systems guarantees optimum results in such cases, too. Wear and tear studies are also traditional tasks for topography measurements. Examples of such tasks include performing a root cause analysis when brake disks have suffered wear and tear.