Automatic digitization of free-form curve by coordinate measuring machines

Chen, Y. D.; Tang, Xin; Ni, Jun; Wu, S. M.

doi:10.1080/00207549408957086

Cited by 5 publications

(4 citation statements)

References 3 publications

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“…In both cases, the inspection of freeform surfaces may be executed with the help of computer aided design (CAD)-based software, where the CAD model may be used as the nominal element [2]. The evaluation relies on the registration of the actual surface with respect to the nominal one and is principally based on local deviation analysis at each nominal point [3,4]. However, the evaluation may be based on the surface reconstruction [5][6][7][8][9] by means of fitting and filtering techniques [10].…”

Section: Introductionmentioning

confidence: 99%

Structural analysis for flexible components with freeform surfaces with the aid of a coordinate measuring machine

Ascione

Polini

2011

Proceedings of the Institution of Mechanical Engineers, Part B:

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A non-rigid part could be subjected to significant distortion after the removal of manufacturing forces. This condition, known as free state variation, is principally due to weight and flexibility of the part and the release of internal stresses resulting from fabrication. The present work deals with the inspection of freeform surfaces belonging to non-rigid parts with the objective of analysing the internal stress and relative strain due to assembly sequences. A manufactured aeronautic component, named Mid Cowling, is considered as a case study. An appropriate fixture equipment has been used in the inspection process to simulate the mating part interface and to locate the part in the coordinate measuring machine (CMM) working volume. In this way the assemblage in the final product has been reproduced. The results of the measurement process are used to evaluate the quality of the real surfaces in terms of deviation from the nominal one. Therefore, these deviations are used as input in a finite element model (FEM) analysis to estimate the stress and strain fields due to the constraint of the assembly.

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Section: Introductionmentioning

confidence: 99%

Structural analysis for flexible components with freeform surfaces with the aid of a coordinate measuring machine

Ascione

Polini

2011

Proceedings of the Institution of Mechanical Engineers, Part B:

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“…In order to better understand the topics aspects of this work, it is opportune to split the entire methodology in three main steps: point digitisation, segmentation and surface modelling. Focusing the attention on "point digitisation" and "surface modelling", it is necessary to highlight some relevant problems associated to the sampling strategy [2].…”

Section: Introductionmentioning

confidence: 99%

Reverse engineering: a selective sampling acquisition approach

Vezzetti

2006

Int J Adv Manuf Technol

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Creation of a CAD model from an hard model is something necessary for design modification, part replication or rapid prototyping and surface inspection. This is reverse engineering. Scientific literature presents many different approaches, even if, actually all the systems, mechanical (contact devices) and optical (non contact devices), work with constant acquisition pitches. This became a great deal in relation with the different object morphologies combinations that the same surface could show. Working in fact with a constant pitch on a free-form surface it is possible to struggle with an insufficient points cloud density, when the acquisition pitch would be a compromise between the complex and elementary features that describe the object to acquire, or with an excessive points cloud density, when the acquisition pitch represents the highest scanner resolution. Referring to this situation, this paper wants to propose, starting from a first raw acquisition, an automatic methodology, directly implemented on the acquisition device, for the selective individuation of surface zones which present sensible curvature. In this approach the curvature of the measured surfaces is analyzed by defining a threshold over which it is necessary to perform a deeper scansion of the surface. In the present paper a methodology for the definition of the threshold value based on the measurement system uncertainty is described. In the current description the method is applied to an algorithm for curvature analysis, but it could be extended to any other approaches. Furthermore, it will be demonstrated that this new methodology is simple to apply and can be easily automated directly in the control scanner software. In the end of the paper a practical example is described in order to give an experimental validation of the method.

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“…A deviation-based distribution which only locates data points at the extremities of the pro®le generally involves a decrease in the sampling size (number of points). A similar technique is used by Chen et al [10] in a predictive scanning routine to inspect a sculptured surface where data points are dynamically thickened in the curvature of the pro®le. However, accurate measurements of roundness cannot be obtained dynamically because the sampling includes an insu cient data set.…”

Section: Introductionmentioning

confidence: 99%

A form of deviation-based method for coordinate measuring machine sampling optimization in an assessment of roundness

Rossi

2001

Proceedings of the Institution of Mechanical Engineers, Part B:

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A method for minimizing coordinate measuring machine (CMM) inspection time in the accuracy measurement of roundness is described. The peculiar feature of the method is to employ a presampling with a strategic distribution of the points, in order to decrease the sample size in point-by-point acquisition. Point distribution is derived from a method for detecting two of the most frequent categories of deviation in the profile: waviness and random deviation. Depending on the actual category of deviation, a subsequent sampling, which locates points near the main features of the profile, is performed to refine the error of roundness. The main goal of the system is to detect an exact roundness error by means of a method for minimizing inspection time for wavy deviation with a fixed level of noisy band superimposed

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Automatic digitization of free-form curve by coordinate measuring machines

Cited by 5 publications

References 3 publications

Structural analysis for flexible components with freeform surfaces with the aid of a coordinate measuring machine

Structural analysis for flexible components with freeform surfaces with the aid of a coordinate measuring machine

Reverse engineering: a selective sampling acquisition approach

A form of deviation-based method for coordinate measuring machine sampling optimization in an assessment of roundness

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