06/05/2018

Process control in the production of artificial leather skins

For the process control during the production of artificial leather skins, the exact transfer of the leather pattern to the artificial leather skin should be ensured. The forming tools have metal surfaces, artificial leather skins are soft and very soft silicone imprints should also be taken. Not only the rough leather structure should be measured but also the microstructure on the nubs and in the scars. All measurements should be carried out with the same sensor.

Conventional stylus tools scan the surface mechanically. They cannot measure the soft surfaces without interaction and they are too slow to take 3D measurements. In non-contact autofocus systems, a lens in the sensor follows the height of the object being measured. The highly structured artificial leather surfaces can only be measured very slowly.

Artificial leather surfaces for car interiors should not be reflected in the windshield of the car. This means that they absorb incident light to a high degree. An optical sensor must be very sensitive in order to be able to reliably determine the topography from the small amount of light scattered on a black artificial leather surface.

The MicroProf® uses a confocal, chromatic distance sensor. The CWL sensor focuses white light on the measuring object and determines the height of the measuring object in the measuring spot from the spectral distribution of the light scattered on the surface. Different measuring heads with measuring ranges of up to 10 mm and a height resolution from 3 nm are available for different measuring tasks. The system can be used to measure the entire spectrum of materials used (leather, metal, silicone, plastic).

For measurements with the MicroProf® the full resolution (2 μm lateral, 3 nm in height) is available for every possible measuring field size.

The SLS is an optical line sensor for extremely fast measurements. It also works according to the principle of chromatic distance measurement. Instead of a single measuring spot, this sensor generates 192 measuring spots, which are equidistantly lined up along a line. In this way, a distance value with a resolution in the nm range is generated for each measuring point. Due to the line arrangement of the measuring points, it is possible to generate a 3D measurement immediately while scanning along a measurement direction perpendicular to it. At measurement rates of up to 2 kHz, the scanning of a measurement object is thus possible in a fraction of the time required for point sensors.

The Mark III software, which is used in MicroProf® to evaluate the measured data, determines the height of the nubs, the width of the scars and the slope of the flanks. The roughness of the surface is determined in small areas between the scars.

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