Design-dependent shrinkage compensation modeling and mechanical property targeting of metal FFF

Ilies Ait-Mansour,Sergei Chekurov,Niklas Kretzschmar,Mika Salmi,Joel Rech

doi:10.1007/s40964-020-00124-8

Ilies Ait-Mansour, Sergei Chekurov + Show 3 more

Open Access

https://doi.org/10.1007/s40964-020-00124-8

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Abstract

Metal-fused filament fabrication is gaining traction due to its low cost and high availability compared to metal powder bed fusion. However, the achievable mechanical properties and effects of shrinkage of this process should be understood thoroughly before it can be implemented as a direct digital manufacturing technology. This study investigates the influence of infill levels and different build orientations on the mechanical properties and shrinkage behavior of 3D-printed, debinded, and sintered components made from BASF Ultrafuse 316LX. The final objective of the work is to define a function for multi-directional shrinkage prediction for any given part geometry to achieve parts with a high degree of dimensional conformity by modifying the original designs accordingly. The Design of Experiment includes tensile and compression testing according to ASTM E8 M-04 and ASTM D695-15, respectively. Tensile testing samples are manufactured in three different build directions and compression testing pins are made with six infill levels. Furthermore, a complex part is printed and its dimensional shrinkage analyzed using 3D scanning. Finally, the multi-directional shrinkage behavior is measured for all samples to establish a shrinkage predictability function by applying linear regression models. Results show that material infill levels have no effect on the shrinkage behavior of printed components. Compressive strength increases with infill level and ultimate tensile strength of parts printed flat indicates the highest tensile testing results, followed by flipped and vertically printed parts. A complex part was manufactured successfully for spare part production, which helped to establish a function with moderate confidence levels for shrinkage predictability.

Highlights

Additive manufacturing (AM) of metal components is increasingly gaining traction in the fabrication of prototypes, tools, and end-use products
Most frequently applied AM metal processes are represented by selective laser melting (SLM), electron beam melting (EBM), metal-based binder jetting (BJ), and indirect AM processes such as investmentand sand casting
A potentially cost-effective alternative for small-scale components can be found in the metal-fused filament fabrication (FFF) process, since even desktop FFF printers could be used for this filament-based

Summary

Introduction

Additive manufacturing (AM) of metal components is increasingly gaining traction in the fabrication of prototypes, tools, and end-use products. New commercially available filaments (“Ultrafuse 316LX”) for metal FFF with high metal filler ratios of 80 vol% were introduced [4], allowing it to reduce the volumetric shrinkage and to integrate AM machines into existing metal injection molding process chains using the same catalytic debinding parameters and comparable sintering temperature profiles. This material has been tested and compared to SLM by [5], showing successful 3D prints with x/y-shrinkages of 13–18% and z-shrinkages of 15–23%, reaching yield strength of 167 MPa and an ultimate tensile strength of 465 MPa (as expected, both tensile strength indicators below SLM)

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