Optical, in situ, three-dimensional, absolute shape measurements in CNC metal working lathes

Abstract

Temperature drifts, tool deterioration, unknown vibrations, as well as spindle play are major effects which decrease the achievable precision of CNC lathes and lead to shape deviations of the processed workpieces. Since currently no measurement system exists for precise, in situ, 3D shape monitoring, much effort is required to simulate and compensate these effects. In this article, we propose an optical measurement principle for first part quality manufacturing. The absolute shape, meaning the diameter and surface profile, of the workpiece is determined from its tangential velocity and the surface distance. In order to allow keyhole access, both measurands are determined simultaneously with a single sensor. Measurements inside a metal working lathe show that the standard uncertainty for the absolute shape measurement is below 1 μm. The measurement uncertainty is nearly independent of the lateral surface velocity and roughness. The in situ measurements are compared to measurements with a tactile coordinate measurement machine for reference.

Full-field modeling and calibration of 3D interference fringe volume with line-shaped Gaussian beam intersection

“…To address this need, a novel laser Doppler distance sensor has been developed. [1][2][3] This sensor offers the advantage of simultaneous axial distance and lateral velocity measurement by utilizing two interference fringe systems that intersect dual-wavelength Gaussian beams, distinguishing it from conventional optical distance measurement techniques. [4][5][6][7][8][9] In this sensor, the velocity and distance are respectively determined by analyzing the Doppler frequency and phase difference of the speckle signals generated by optically rough surfaces or particles passing through the fringe systems.…”

An Automatic Error Surface Diagnostics During Turning Machining Operation Using Laser Sensor

“…Some approaches to in-process dimensional control and measurement were described almost 30 years ago by [Fan 1991], then for example by [Yandayan 1997], [Vacharanukul 2005], [Ko 2007] and [Czarske 2013]. The experiments with measuring in Lathe machines were described, for example, in the works [Jeong 2005], [Kuschmierz 2016], [Zou 2017] and using laser sensors in the articles [Dorsch 1994], [Günther 2009], [Valino 2012] and [Gunther 2013]. New approaches to data acquisition and principles of digital data storage from the production process to industrial Cloud Platforms can be found in the articles [Lu 2019], [Mahmoud 2019], and [Zidek 2020].…”

Use of dual coolant displacing media for in-process optical measurement of form profiles

“…In-process measurement of a workpiece surface y(x, z) (figure 1) is a difficult real-time measurement [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. It is performed in a harsh and complex measurement environment to acquire workpiece surface y(x, z) when the workpiece is being machined.…”

“…In-process measurement could be developed to support a feedback precision control system to reduce the workpiece surface form error during a machining process [3,4]. Without the in-process measurement, the workpiece surface must be measured offline in a laboratory, which would cause a significant amount of re-positioning error together with the re-mounting problem [7,9,15]. For in-process measurement, contact and non-contact measurement have been used.…”