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

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.

Applications of Additively Manufactured Tools in Abrasive Machining—A Literature Review

“…The knowledge of the optimal process parameters for the fabrication of polyamide or metal matrix composites along with Design for Additive Manufacturing (DfAM) tools and techniques [ 105 ] can be a key issue for wider implementation of AM in the production of grinding tools. Apart from the achievable dimensions of some features such as thin walls or holes [ 37 , 92 ], an effective control of the tool porosity and its micro-structure are the main advantages of AM processes.…”

“…Additive Manufacturing (AM), commonly referred to as incremental or 3D printing technology, refers to the layered construction of objects based on 3D computer models with complex inner [ 36 , 37 ] or outer [ 4 ] geometries. A 3D computer model is created in CAD software used for computer aided design (CAD) or obtained as a cloud of points by 3D scanning [ 38 ].…”

“…The measurements performed with the use of computer tomography and digital radiography confirmed that the DMLS technology made it possible to directly produce holes 3 mm, 2.5 mm, 2 mm, 1.35 mm and 1 mm in diameter under different angles during additive processing. As the prediction of hole clearance is a crucial task when designing the complex internal geometries in mechanical components, Deja and Zieliński [ 37 ] proposed an in-process inspection method for the evaluation of the dimensional and shape accuracy of straight through holes made of AlSi10Mg and MS1 test samples manufactured using DMLS technology. The experiments performed enabled the development of a general mathematical model for determining the hole clearance for the given sample thickness G ∈ [ 1 , 5 ] and the theoretical hole diameter d t ∈ [0.3, 1.5].…”

“… 3D printing process chain for the example of a turbine blade produced by means of DMLS technique with the use of EOS Maraging Steel MS1 in the form of powder; based on references [ 36 , 37 ]. …”

Multi-Criteria Comparative Analysis of the Use of Subtractive and Additive Technologies in the Manufacturing of Offshore Machinery Components

“…According to [19], this industry can be characterised as conservative with respect to change, although DMLS and selective laser melting (SLM) technologies are currently being successfully used to manufacture high-pressure blades for gas and Tesla turbines [7,14,18,20,23,30]. These kinds of parts have complex geometries, including inner features in the form of miniature holes [10] and channels for delivering cooling fluid. The creation of complex inner features by conventional machining methods can be difficult, and in some cases even impossible.…”