Geometrical deviation induced measurement error of freeform surfaces for coordinate measuring machines

Liu, M. Y., Cheung, C. F. and Yang, S. M. (2017) Geometrical deviation induced measurement error of freeform surfaces for coordinate measuring machines. In: The 13th International Symposium on Measurement Technology and Intelligent Instruments (ISMTII).

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Geometrical deviation induced measurement error of freeform surfaces for coordinate measuring machines
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Abstract

The measurement error of the coordinate measuring machine (CMM) is affected by many factors such as the accuracy of the hardware of the machine, and measurement strategy, etc. The properties of the workpiece can also influence the measurement result such as the form error and surface roughness, especially in the situation of measurement of complex surfaces such as freeform and structured surfaces. Generally, a computer aided design (CAD) model of the designed surface is much desirable for the measurement of a freeform surface with a CMM by using the most commonly used touch trigger probe. The normal vectors of the designed surface are usually calculated by the software of the CMM from the CAD model as the probing directions. However, in the presence of the machining form error during the measurement process, the actual surface is deviated from the CAD model and this introduces associated measurement error. The measurement error influenced by the form of the workpiece which are geometrical errors induced by the workpiece itself which is independent to the CMM machine and the measurement environment. In other words, even if the CMM machine and the measurement condition are perfect without having any errors, the measurement result has certain amount of deviation from the true surface since there exists the geometrical error. There is little research to quantitatively determine such kind of error. In this paper, the influence of the geometrical error is studied theoretically. Moreover, a software tool has been developed to determine the measurement error affected by the geometrical error of the workpiece. With the developed software tool, the measurement error influenced by different factors such as different levels of errors and different probe radii can be derived and visualized in detail. A series of simulated experiments were conducted to demonstrate the effectiveness of the proposed error model.

Keywords:freeform surface, coordinate measuring machines, measurement error, machining error, precision metrology, geometrical deviation
Subjects:H Engineering > H700 Production and Manufacturing Engineering
Divisions:College of Science > School of Engineering
ID Code:53950
Deposited On:29 Mar 2023 09:54

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