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A pilot study to assess an in-process inspection method for small diameter holes produced by direct metal laser sintering

Mariusz Deja (Department of Manufacturing and Production Engineering, Faculty of Mechanical Engineering, Gdansk University of Technology, Gdansk, Poland)
Dawid Zielinski (Department of Manufacturing and Production Engineering, Faculty of Mechanical Engineering, Gdansk University of Technology, Gdansk, Poland)

Rapid Prototyping Journal

ISSN: 1355-2546

Article publication date: 5 December 2019

Issue publication date: 25 February 2020

205

Abstract

Purpose

The purpose of this study is to evaluate the geometric quality of small diameter holes in parts printed by direct metal laser sintering (DMLS) technology. An in-process optical inspection method is proposed and assessed during a pilot study. The influence of the theoretical hole diameter assumed in a computer-aided design (CAD) system and the sample thickness (hole length) on the hole clearance was analyzed.

Design/methodology/approach

The samples are made of two different materials: EOS MaragingSteel MS1 and aluminium alloy EOS Aluminium consisted of straight through holes of different diameters and lengths. Dimensional and shape accuracy of the holes were determined with the use of the image processing software and the computer analysis of two-dimensional (2-D) images. The definition of the equivalent hole diameter was proposed to calculate the hole clearance. Feret’s diameters were determined for the evaluation of the shape accuracy.

Findings

The dependency between the equivalent hole diameter and the theoretical diameter was approximated by the linear function for a specific sample thickness. Additionally, a general empirical model for determining the hole clearance was developed, allowing for calculating the equivalent hole diameter as a function of a sample thickness and a theoretical hole diameter.

Practical implications

Developed functions can be used by designers for a proper assignment of a hole diameter to achieve the required patency. The relevant procedures and macros based on proposed empirical models can be embedded in CAD systems to support the designing process.

Originality/value

The analysis of the geometric quality of the holes in parts printed by DMLS was based on the computer analysis of 2-D images. The proposed method of assessing the shape accuracy of straight through holes is relatively cheap, is widely available and can be applied to the features of other shapes produced by three-dimensional printing.

Keywords

Acknowledgements

The authors of the article would like to thank Dr Piotr Pawłowski from the Department of Intelligent Technologies, the Institute of Fundamental Technological Research, Polish Academy of Sciences, for preparing the test samples. Special thanks to Dr Tomasz Seramak from the Department of Materials Engineering and Bonding, Faculty of Mechanical Engineering, Gdansk University of Technology, for providing digital models of the test samples obtained by a computer tomography. Computations carried out with the use of software and computers from Academic Computer Centre in Gdansk - TASK (www.task.gda.pl).

Citation

Deja, M. and Zielinski, D. (2020), "A pilot study to assess an in-process inspection method for small diameter holes produced by direct metal laser sintering", Rapid Prototyping Journal, Vol. 26 No. 2, pp. 418-436. https://doi.org/10.1108/RPJ-05-2019-0132

Publisher

:

Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited

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