Optical methods for in-process roughens measurement of rotationally symmetric workpieces

摘要

The paper presents innovative optical sensors for inprocess measurements of the surface topography.This instrumentation may readily be integrated into turning machines, achieving three goals: 1)surface quality inspection; 2) determination of the edge gradient or the waviness of the workpiece,and 3) improvement of the instantaneous diameter measurement. Rotationally symmetric workpieces show a surface which can be described in axial directiononly. For a stationary viewer, the surface of a rotating turned workpiece appears to be a wavefunction. Due to a finite exposure time of optical sensors the wave function is slurred depending onfeed motion, cutting speed, and object diameter This effect can be reduced by use of pulse widthmodulated lasers in synchronization with CCD-receivers by an angle incremental transducerFurthermore, two profile intersection samples of the D. U. T are recorded for the determination of thefeed speed. The presented profile intersection scanner captures the stray light reflected by theobject's surface and focused upon a line scan sensor: The following discrete Fourier analysis of thepixel information determines characteristic frequencies corresponding to the periodic surfacestructure. It is possible to acquire the mean groove distance and to localize microstructures. Thearrangement allows additional use of the same sample beam as part of a triangulation sensor which isplaced orthogonally towards the roughness sensor: The advanced Fresnel tracer allows the evaluationof 2D Fresnel diffraction patterns laser illumination of the workpiece edge, captured by an opticalsystem, and focused upon CCD-receivers. Variations of the ambient temperature does not effect theresults since the complete instrumentation is in a housing at stable temperature. High pressure jetsmake sure that the workpiece surface in the measurement areas are blown free from oil, coolingfluids, and chips.