On the role of wet abrasive centrifugal barrel finishing on surface enhancement and material removal rate of LPBF stainless steel 316L

Mahyar Khorasani,Milan Brandt,Amirhossein Ghasemi,Martin Leary,Ian Gibson

doi:10.1016/j.jmapro.2020.09.058

Abstract

Poor surface finish is a primary challenge to the commercial implementation of Additive Manufacturing (AM). To solve this problem, various Material Removal Rate (MRR) processes have been proposed. However, current methods provide sub-optimal outcomes for the complex geometry enabled by AM. Abrasive Centrifugal Barrel Finishing (ACBF) and Wet Abrasive Centrifugal Barrel Finishing (WACBF) can provide an effective surface finishing solution method that is compatible with the geometric complexity of AM components. ACBF and WACBF are commercially robust processes that can economically process multiple components to polish cavities and intricate internal geometry. This research documents the experimental application of WACBF to polish Stainless Steel (SS) 316 L, printed by Laser-Based Powder Bed Fusion (LPBF). The performance of WACBF on volumetric MRR is also examined. To assess the homogeneity of the abrasive process, surface roughness was quantified in directions parallel, vertical and at 45° to the laser scan direction. A Taguchi L8 experiment was devised with three repetitions to assess the influence of WACBF parameters including rotational speed, media size and running time on the measured surface roughness and material removal rate. This experiment confirms that surface roughness and MRR have a non-linear correlation with increasing the rotational speed, and that enhanced surface roughness is achieved with larger media size. An important observation for commercial implementation is that increasing the time of the process provides an insignificant reduction in surface quality, and MRR implying that for commercial applications, high-throughput can be achieved without compromising quality. These experiments confirm that WACBF processing improved the surface roughness for parallel, vertical and 45° surfaces by 62.30 %, 56.33 %, and 56.08 % respectively.

Highlights

Additive Manufacturing (AM) provides numerous technical and economic opportunities in comparison to traditional manufacturing processes: lower material wastage, direct digital design with no custom tooling, high geometric freedom with fewer manufacturing constraints and the opportunity to fabricate highly integrated net shapes with little post-processing and assembly [1,2,3]
The minimum values of the roughness obtained after Wet Abrasive Centrifugal Barrel Finishing (WACBF) were 2.01 μm, 3.3654 μm and 2.78 μm for parallel, vertical and angled measurements respectively. This shows that the WACBF process enhances the surface quality of asbuilt samples by 56.08 %, 56.33 % and 62.30 % for angled, vertical and parallel measurements. This outcome confirms uniform finishing and proves that WACBF is suitable for finishing of AM components
If the very fine surface quality is required, it is recommended to use the fresh media after each machining process. This experiment quantifies the performance of WACBF as a surface enhancement process for Laser-Based Powder Bed Fusion (LPBF) stainless steel 316 L

Summary

Introduction

Additive Manufacturing (AM) provides numerous technical and economic opportunities in comparison to traditional manufacturing processes: lower material wastage, direct digital design with no custom tooling, high geometric freedom with fewer manufacturing constraints and the opportunity to fabricate highly integrated net shapes with little post-processing and assembly [1,2,3]. Technical challenges still exist in the commercial application AM systems like Laser-Based Powder Bed Fusion (LPBF) is a potential for relatively high dimensional varia tion and poor surface finish [4,5,6]

Methods

Results

Conclusion