November 2012

These papers were presented at 9th International Conference MATAR 2012, Prague

INTEGRATED MODELLING OF AXIAL MOTION ERROR SOURCES FOR 5-AXIS PRECISION MACHINING CENTRE WITH DIRECT DRIVES

Modern Machinery (MM) Science Journal, November 2012
J. Jedrzejewski, W. Kwasny
Wroclaw University of Technology, Wroclaw, Poland
Abstract

This paper discusses machine tool modelling, comprising the design process, degradation and repair processes and accurate identification, aimed at the effective improvement of machine tools. The importance of the holistic approach to modelling for the accurate identification of machine tool errors and the ways in which they arise and for their minimization, taking into account thermal and dynamic interactions, is highlighted. Models of the sources of errors (power losses) occurring in rotary direct drive motors and in rotary tilting table bearings are presented. Also the modelling of power losses in linear direct drive motors and in rolling guideways is described. Mostly original relations, supported by the results of studies on the modelling and computing of errors in the controlled axes of a 5-axes machining centre carried out by the authors, are used in the modelling.

Keywords: Holistic model, machining centre, direct drive, power losses, error
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THREE-AXIS TOOL-PATH B-SPLINE FITTING BASED ON PREPROCESSING, LEAST SQUARE APPROXIMATION AND ENERGY MINIMIZATION AND ITS QUALITY EVALUATION

Modern Machinery (MM) Science Journal, November 2012
Changya Yan1, Chenhan Lee1, Jianzhong Yang2
1Wuhan Huazhong Numerical Control Co., Ltd, Wuhan, P. R. China, 2National NC System Engineering Research Center, Huazhong University of Science and Technology, Wuhan, P. R. China
Abstract

Current state-of-art CAM systems generate piecewise linear (G01-based) tool paths that lack G1 and G2 continuity. This paper presents a systematic solution of tool path B-spline fitting for improving the continuity and quality and a tool set to evaluate the quality of either G-Code commands or CNC-interpolated axis motion commands. The core of the solution involves a preprocessor and a cubic B-Spline fitting algorithm. The preprocessor identifies feature points (Hard Break Point Identification) and uses a point smoothing algorithm to improve the quality of the data points by minimizing the length sum subject to shape preserving and tolerance constraints. A B-Spline fitting algorithm based on least square approximation and energy minimization is used to ensure fair (shape-preserving) tool-paths with G2 continuity and stable curvature transition. The evaluation tool set computes quality criterions, such as G2 discontinuity locations, curvature, inflexion, jerks and torsion in the G-code or CNC-interpolated axis motion commands. All above algorithms are integrated into a software package. The validation of the effectiveness and efficiency of above solutions is performed by comparing tool-paths with and without the preprocessing and B-Spline fitting.

Keywords: B-spline fitting, shape preserving, point smoothing, tool path quality evaluation
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IMPROVING 5-AXIS MILLING OPERATIONS USING PROCESS MODELS

Modern Machinery (MM) Science Journal, November 2012
E. Budak
Manufacturing Research Lab, Sabanci University, Istanbul, Turkey
Abstract

5-axis milling is a technology used in many industries such as aerospace, automotive and die/mold for machining of complex surfaces. Cutting forces, form errors and chatter vibrations are among the most important limitations in these operations. Process models can be used for predictions and optimization in 5-axis milling. In this paper, the process models and their applications are presented. These methods are implemented in simulation software, and applied in machining of industrial parts where productivity increase for example cases is demonstrated.

Keywords: 5-axis milling, process modeling
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A MACHINE VISION APPROACH FOR AUTOMATED RAW PART ALIGNMENT IN MACHINE TOOLS

Modern Machinery (MM) Science Journal, November 2012
A. Mendikute, M. Zatarain
IK4-IDEKO, Elgoibar, Spain
Abstract

Large raw parts require a long time consuming process of alignment into the machine, before the machining process starts. Alignment process requires two steps: first, characterization of geometry, and second, alignment. Important skills are necessary, and, besides the time consumption of workforce and machine, the risk of getting into shortage of material is high. The paper presents a machine integrated 3D vision approach based on stereo-photogrammetry able to autonomously verify the alignment and calculate the required raw part set-up corrections. The potential of the solution to reduce the alignment process time of raw parts in machine tools is demonstrated in two milling pilot cases.

Keywords: 3D Vision, alignment, raw part
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