Author Identifier (ORCID)
Abstract
Additive Friction Stir Deposition (AFSD) is an additive manufacturing technique used to fabricate large-sized components layer-by-layer in a solid state, below the melting temperature. Poor interlayer mixing between subsequent layers results in a lack of mechanical interlocking, leading to low-strength components. The role of pin design plays a crucial role in fabricating high-strength components, requiring a comprehensive understanding of thermo-mechanical behaviour and flow pattern in the deposition zone. In this study, five different pin geometries are presented and investigated using a three-dimensional (3D) computational fluid dynamics (CFD) model. A user-defined function (UDF) was used to calculate strain- and temperature-dependent viscosity. To obtain the optimum pin configuration, various parameters, including mixing index, velocity vectors, thermal gradient, flow patterns, required torque, and required transverse forces, have been evaluated at a constant deposition speed of 300 mm/min and a deposition rate of 9 kg/hr. Moreover, four different tool rotational speeds (380, 640, 840, and 1050 RPM) and six diameter ratios (1.75, 2, 2.25, 2.5, 2.75, and 3) were used to evaluate their effect on inter-layer mixing and material flow behaviour. The numerical results obtained in this study are validated by the available literature and show good agreement. A pin profile with three flat faces (3FP) showed a 90.9% enhancement in vertical material flow velocity. This resulted in better interlayer mixing, with a mixing index of 35.5%, compared to the circular pin (CP), which was approximately four times lower (6.7%). Furthermore, better mixing was achieved with 1050 RPM and a diameter ratio of 2. The torque and transverse force required by the tool with a 3FP pin profile were, respectively, 7.23% and 17% lower than those of a tool with a circular pin (CP). This paper suggests that a triangular (3FP) pin profile with a diameter ratio of 2 and a rotational speed of 1050 RPM yields better interlayer mixing and reduced power consumption during the AFSD process.
Keywords
additive friction stir deposition, additive manufacturing, AFSD, AFSD tool design, AFSD tool optimization, metal 3D printing
Document Type
Journal Article
Date of Publication
10-1-2026
ISSN
17555817
Volume
69
Publication Title
CIRP Journal of Manufacturing Science and Technology
Publisher
Elsevier
School
Mineral Recovery Research Centre / School of Engineering / Centre for Advanced Materials and Manufacturing
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
First Page
84
Last Page
94
Recommended Citation
Habib, N., Vafadar, A., & Guzzomi, F. (2026). Numerically evaluating the effect of pin geometries on interlayer material mixing and thermo-mechanical characteristics during additive friction stir deposition (AFSD). CIRP Journal of Manufacturing Science and Technology, 69, 84–94. https://doi.org/10.1016/j.cirpj.2026.05.012