Online Monitoring of Surface Quality for Diagnostic Features in 3D Printing

Abstract

Investigation into non-destructive testing and evaluation of 3D printing quality is relevant due to the lack of reliable methods for non-destructive testing of 3D printing defects, including testing of the surface quality of 3D printed parts. The article shows how it is possible to increase the efficiency of online monitoring of the quality of the 3D printing technological process through the use of an optical contactless high-performance measuring instrument. A comparative study of contact (R130 roughness tester) and non-contact (LJ-8020 laser profiler) methods for determining the height of irregularities on the surface of a steel reference specimen was performed. It was found that, in the range of operation of the contact method (Ra 0.03–6.3 µm and Rz 0.2–18.5 µm), the errors of the contactless method in determining the standard surface roughness indicators Ra and Rz were 23.7% and 1.6%, respectively. Similar comparative studies of contact and non-contact methods were performed with three defect-free samples made of plastic polylactic acid (PLA), with surface irregularities within the specified range of operation of the contact method. The corresponding errors increased and amounted to 65.96% and 76.32%. Finally, investigations were carried out using only the non-contact method for samples with different types of 3D printing defects. It was found that the following power spectral density (PSD) estimates can be used as diagnostic features for determining 3D printing defects: Variance and Median. These generalized estimates are the most sensitive to 3D printing defects and can be used as diagnostic features in online monitoring of object surface quality in 3D printing.

Vapor Overproduction Condition Monitoring in a Liquid–Vapor Ejector

“…To verify the reliability of the results experimentally obtained by condition monitoring [28], the authors of the work performed additional mathematical modeling in the Ansys CFX Academic software package.…”

Editorial for Special Issue “Advances in Computer-Aided Technology”

“…The article shows how it is possible to increase the efficiency of the online monitoring of the quality of the 3D printing technological process using an optical contactless high-performance measuring instrument. The research results are applicable to 3D-printing machines [4]. The study of the authors Ivanov et al describes the production of flexible fixtures with modern machining technologies capable of machining similar shapes and sizes of parts with complex geometries [5].…”

On-Machine LTS Integration for Layer-Wise Surface Quality Characterization in MEX/P

“…Although particularly popular in metal AM [21][22][23], layer-wise monitoring has also been applied in MEX/P, primarily through three different sensing technologies: thermal sensing [24], 2D vision [25,26], and 3D vision [16,23,[27][28][29][30][31][32][33][34][35][36][37][38][39][40]. Monitoring the 3D layer topography offers distinct advantages over thermal and two-dimensional sensing, as it allows for direct measurement of layer features, like layer height [27,28], or in-plane defects [16,23,30,31].…”

“…The analysis of previous research efforts in LTS-based layer-wise monitoring of MEX/P part quality leads to the definition of several key aspects, like the integration strategy, the vertical repeatability, or the objective quality characteristic. The summary in Table 1 shows how most authors decided to integrate commercial LTS models [16,[28][29][30]35,37,38], although there are also examples of built-in-house sensor arrangements [27,36]. The layer-wise inspection could take place using pure on-machine solutions, where the LTS has been fully integrated into the manufacturing equipment [16,27,30,31,36] or has been attached to actuated [28,37,38] or fixed [29,35] off-machine arrangements.…”

“…The summary in Table 1 shows how most authors decided to integrate commercial LTS models [16,[28][29][30]35,37,38], although there are also examples of built-in-house sensor arrangements [27,36]. The layer-wise inspection could take place using pure on-machine solutions, where the LTS has been fully integrated into the manufacturing equipment [16,27,30,31,36] or has been attached to actuated [28,37,38] or fixed [29,35] off-machine arrangements. The scanning strategy and the relative movement between part and LTS are conditioned by the type of integration used.…”