Optical probing for CNC machining of large parts made from fiber-reinforced polymer composite materials

In machining of large fiber-reinforced polymer (FRP) composite parts, the part must be precisely located before machining. The exact location and shape are usually determined by the probing systems employing a touch probe integrated with a CNC machine. When measuring a large number of points, touch probing consumes a significant amount of time and adversely affects the utilization of the CNC machine in serial production. In order to increase the probing speed and acquire additional details, a new optical probing operating on the laser triangulation measuring principle is developed. The paper describes the measuring principle, system integration, neural network as the measuring system transfer function, and the calibration process. When measuring polyester or epoxy resin-based materials, the laser light penetrates into the part and reflects back inside of the part. This interference is successfully neutralized by the calibration body made from the same FRP material as the measured part. Verification of the calibration body and the machine coordinate system alignment is demonstrated by comparison of corrections determined with the optical and touch probing.

[1]  H. Ding,et al.  Optimal Design of Measurement Point Layout for Workpiece Localization , 2009 .

[2]  A. Weckenmann,et al.  Probing Systems in Dimensional Metrology , 2004 .

[3]  Mozafar Saadat,et al.  Dimensional variations during Airbus wing assembly , 2002 .

[4]  Aristides A. G. Requicha,et al.  Accessibility analysis for planning of dimensional inspection with coordinate measuring machines , 1999, IEEE Trans. Robotics Autom..

[5]  William T. Estler,et al.  Measurement technologies for precision positioning , 2015 .

[6]  Tilo Pfeifer,et al.  Optical Methods for Dimensional Metrology in Production Engineering , 2002 .

[7]  John W. Gillespie,et al.  Process-Induced Stress and Deformation in Thick-Section Thermoset Composite Laminates , 1992 .

[8]  André Voet,et al.  Optical measurement techniques for mobile and large scale dimensional metrology , 2007 .

[9]  Mikel Zatarain,et al.  Raw part characterisation and automated alignment by means of a photogrammetric approach , 2012 .

[10]  A. Mendikute,et al.  Automated Raw Part Alignment by a Novel Machine Vision Approach , 2013 .

[11]  Steven D. Phillips,et al.  Laser trackers for large-scale dimensional metrology: A review , 2016 .

[12]  Farid Najafi,et al.  Prediction of geometrical variations in Airbus wingbox assembly , 2007 .

[13]  Edward C. De Meter,et al.  An analysis of the effect of datum-establishment methods on the geometric errors of machined features , 2000 .

[14]  Morten Lind,et al.  A flexible 3D object localization system for industrial part handling , 2012, 2012 IEEE/RSJ International Conference on Intelligent Robots and Systems.

[15]  S. J. Gordon,et al.  Real-time part position sensing , 1988 .

[16]  F. Chang,et al.  Volume shrinkages and mechanical properties of various fiber-reinforced hydroxyethyl methacrylate-polyurethane/unsaturated polyester composites , 2007 .

[17]  W. Chiu,et al.  Residual Stresses Introduced to Composite Structures due to the Cure Regime: Effect of Environment Temperature and Moisture , 2016 .

[18]  Aitor Olarra,et al.  Traceability of On-Machine Tool Measurement: A Review , 2017, Sensors.

[19]  Olav Egeland,et al.  Robotic Assembly of Aircraft Engine Components Using a Closed-loop Alignment Process☆ , 2014 .

[20]  William T. Estler,et al.  Advances in Large-Scale Metrology – Review and future trends , 2016 .

[21]  Tonny Nyman,et al.  Prediction of Shape Distortions for a Curved Composite C-spar , 2005 .

[22]  Drago Bračun,et al.  Spectral selective and difference imaging laser triangulation measurement system for on line measurement of large hot workpieces in precision open die forging , 2017 .

[23]  L. Hollaway.  Advanced fibre-reinforced polymer (FRP) composite materials for sustainable energy technologies , 2013 .

[24]  Yasuhiro Takaya,et al.  On-machine dimensional measurement of large parts by compensating for volumetric errors of machine tools , 2016 .

[25]  Richard A. Wysk,et al.  Automatic part localization in a CNC machine coordinate system by means of 3D scans , 2015 .

[26]  Krzysztof Okarma,et al.  The 3D scanning system for the machine vision based positioning of workpieces on the CNC machine tools , 2012, 2012 17th International Conference on Methods & Models in Automation & Robotics (MMAR).

[27]  M. Saadat,et al.  Measurement systems for large aerospace components , 2002 .