Design Process Control for Improved Surface Finish of Metal Additive Manufactured Parts of Complex Build Geometry

Mikdam Jamal,Michael Morgan

doi:10.3390/inventions2040036

Abstract

Metal additive manufacturing (AM) is increasingly used to create complex 3D components at near net shape. However, the surface finish (SF) of the metal AM part is uneven, with surface roughness being variable over the facets of the design. Standard post-processing methods such as grinding and linishing often meet with major challenges in finishing parts of complex shape. This paper reports on research that demonstrated that mass finishing (MF) processes are able to deliver high-quality surface finishes (Ra and Sa) on AM-generated parts of a relatively complex geometry (both internal features and external facets) under select conditions. Four processes were studied in this work: stream finishing, high-energy (HE) centrifuge, drag finishing and disc finishing. Optimisation of the drag finishing process was then studied using a structured design of experiments (DOE). The effects of a range of finishing parameters were evaluated and optimal parameters and conditions were determined. The study established that the proposed method can be successfully applied in drag finishing to optimise the surface roughness in an industrial application and that it is an economical way of obtaining the maximum amount of information in a short period of time with a small number of tests. The study has also provided an important step in helping understand the requirements of MF to deliver AM-generated parts to a target quality finish and cycle time.

Highlights

The surface finish of non-machined complex near net shape metal additive manufacturing (AM) components is rough and uneven, having a relationship with build orientation, machine build parameters, material and powder size
The results show that each of the finishing processes improved the starting workpiece morphology by progressively cutting the peaks and obtaining a smooth surface based on the setting of the operational parameters
The surface roughness profile (Figures 8 and 9) shows that the valley surfaces remain largely unaffected by the finishing process, this may be attributed to the media size, which cannot reach these regions except in stream finishing where fine spherical Al Oxide media was employed

Summary

Introduction

The surface finish of non-machined complex near net shape metal additive manufacturing (AM) components is rough and uneven, having a relationship with build orientation, machine build parameters, material and powder size. This is an increasingly challenging problem as AM components are frequently of high complexity, rendering them even more difficult to finish, which deleteriously impacts on post-processing time and labour, driving costs upwards. A review of the literature shows that only limited scientific research has been published with respect to mass finishing, associated with AM, and few mathematical or process models exist. Further important publications [2,3]

Objectives

Methods

Results

Conclusion