Methodology for GD&T verification in an innovative benchmark part for contactless scanning systems

This paper presents an innovative method to investigate the accuracy and capability of contactless laser scanning systems in terms of geometrical dimensioning and tolerancing (GD&T) control. The current work proposes a standard benchmark part with typical features conforming to different families of GD&T. The benchmark part designed consists of various canonical features widely used in an engineering and industrial applications. Further, the adopted approach includes the methodology for comparison of geometry using a common alignment method for contactless scanning system and a CMM. In addition, proposal of different scanning orientation methods for contactless system is also realized. Surface reconstruction of the benchmark model is achieved using different reverse engineering software, and results are analyzed to study the correlation between different geometries of contact and contactless system. Considering the contact based measurement as a reference, different models developed were analyzed and compared in terms of geometrical and dimensional tolerance. The proposal of standard benchmark part and methodology for GD&T verification will provide a simple and effective way of performance evaluation for various contactless laser-scanning systems in terms of deviations.

A Particle Swarm Optimization Approach for Minimizing GD&T Error in Additive Manufactured Parts

This paper presents a particle swarm optimization (PSO) approach to improve the geometrical accuracy of additive manufacturing (AM) parts by minimizing geometrical dimensioning and tolerancing (GD&T) error. Four AM process parameters viz. Bed temperature, nozzle temperature, Infill, layer thickness are taken as input while circularity and flatness error in ABS part are taken as response. A mathematical model is developed for circularity and flatness error individually using regression technique in terms of process parameters as design variables. For the optimum search of the AM process parameter values, minimization of circularity and flatness are formulated as multi-objective, multi-variable optimization problem which is optimized using particle swarm optimization (PSO) algorithm and hence improving the geometrical accuracy of the ABS part.

Three-Dimensional Optical Measurements of Porous Foams

The optical, noncontact stereovision system and data analysis procedure are developed for the measurement of porous foams. The stereovision measurement system has demonstrated the capability to capture both the micro-scale features and the macro-scale shape of both the open-cell and closed-cell porous foams. A computational procedure, denoted as the grid method, is developed to identify representative planes on the porous foam surface using the stereovision measured data points. The relative positions between planes can be used to calculate the angles and distances between porous foam surfaces. A SiC open-cell and an aluminum closed-cell foams are used as examples to validate the grid method and demonstrate its computational efficiency. This research enables the form measurements and geometrical dimensioning and tolerancing of porous foams for quality control and assembly and contact analysis.