Search results

This paper aims to present a methodology for volumetric error compensation. This technique is applied to an Objet Eden350V 3D printer and involves a custom measurement strategy.

The kinematic model of the printer is explained, and its error model is simplified to 18 independent error functions. Each error function is defined by a cubic Legendre polynomial. The coefficients of the polynomials are obtained through a Levenberg–Marquardt optimization process. This optimization process compares, in an iterative algorithm, nominal coordinates with actual values of the cloud of points. The points are built in the faces of a gauge artefact as conical sockets defining one unique point for each socket. These points are measured by a coordinate measuring machine self-centring measurement process.

Most of the errors of the 3D printer are systematic. It is possible to obtain an improvement of 70 per cent in terms of global mean error reduction in single points within a volume of 120 × 120 × 40 mm. The forecast of the final error compensation fully matches the actual final error.

This methodology can be used for accuracy improvement in additive manufacturing machines.

Unlike the calculation of geometric errors, the proposed parametric determination through optimization of the error model allows global error reduction, which decreases all sort of systematic errors concurrently. The proposed measurement strategy allows high reliability, high speed and operator independence in the measurement process, which increases efficiency and reduces the cost. The proposed methodology is easily translated to other rapid prototyping machines and allows scalability when replicating artefacts covering any working volume.

An approach is presented for the development of a predictive maintenance system for rotor‐dynamic pumps, which focuses on the diagnosis of abnormal events related to fluid‐dynamic operating conditions. This methodology is based on an experimental characterization of the dynamic response of the pump under different loads and operation anomalies. The procedure has been put into practice on a medium‐sized centrifugal pump. The results obtained show that a simple spectral analysis of the pressure signals captured at either the inlet or the outlet of the pump can provide sufficient decision criteria to constitute the basis for a diagnostic system. This was not true however when analyzing signals of acceleration at the pump casing.