Towards the Determination of Machining Allowances and Surface Roughness of 3D-Printed Parts Subjected to Abrasive Flow Machining

Mykhailo Samoilenko,Greg Lanik,Vladimir Brailovski

doi:10.3390/jmmp5040111

Mykhailo Samoilenko, Greg Lanik + Show 1 more

Open Access

https://doi.org/10.3390/jmmp5040111

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Abstract

Abrasive flow machining (AFM) is considered as one of the best-suited techniques for surface finishing of laser powder bed fused (LPBF) parts. In order to determine the AFM-related allowances to be applied during the design of LPBF parts, a numerical tool allowing to predict the material removal and the surface roughness of these parts as a function of the AFM conditions is developed. This numerical tool is based on the use of a simplified viscoelastic non-Newtonian medium flow model and calibrated using specially designed artifacts containing four planar surfaces with different surface roughnesses to account for the build orientation dependence of the surface finish of LPBF parts. The model calibration allows the determination of the abrasive medium-polished part slip coefficient, the fluid relaxation time and the abrading (Preston) coefficient, as well as of the surface roughness evolution as a function of the material removal. For model validation, LPBF parts printed from the same material as the calibration artifacts, but having a relatively complex tubular geometry, were polished using the same abrasive medium. The average discrepancy between the calculated and experimental material removal and surface roughness values did not exceed 25%, which is deemed acceptable for real-case applications. A practical application of the numerical tool developed was demonstrated using the predicted AFM allowances for the generation of a compensated computer-aided design (CAD) model of the part to be printed.

Highlights

In recent years, additive manufacturing (AM), or 3D printing, became a widely used and rapidly developing technology that simplifies the production of complex parts with reduced weight and improved functionality
Despite the advantages presented by laser powder bed fusion (LPBF), an excessive as-built surface roughness inherent in the process impacts the fluid flow and the heat transfer characteristics of LPBF parts, and alters their mechanical properties
Based on the above considerations, the ultimate goal of this study is to develop a numerical model allowing the prediction of Abrasive flow machining (AFM) allowances and the generation of compensated 3D computer-aided design (CAD) models of LPBF parts as a function of the selected AFM media, process parameters and required surface finish

Summary

Introduction

Additive manufacturing (AM), or 3D printing, became a widely used and rapidly developing technology that simplifies the production of complex parts with reduced weight and improved functionality. Laser powder bed fusion (LPBF) became one of the most mature technologies for the 3D printing of metal parts. Strano et al [1] studied the impact of the LPBF build orientation on the surface topography, while Kruth et al [2] provided a detailed explanation of mechanical limitations associated with the surface finish of LPBF parts. They determined that the bigger the angle between the surface of a printed part and the building platform, the higher the surface roughness. As reported by Urlea and Brailovski [3], if the build angle of a Ti-6Al-4V component increases from 0 to 135◦ , the as-printed surface roughness Ra increases from 4 to 23 μm

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