© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of IWPDF 2021 Chair, Tuncay YalçinkayaMicroscale forming operations have become popular due to miniaturisation which focuses on micro scale design and manufacturing of devices, components and parts, e.g. in RF-MEMS. In such processes when the component dimension becomes comparable with the grain size, considerable size effect is observed. Recent experimental studies on micron sized sheet specimens have shown that the ratio between thickness (t) and grain size (d) has a significant influence on the mechanical behavior of materials which cannot be explained merely with the intrinsic (grain) size effect. Even though the grain sizes are similar, remarkable differences in mechanical response is obtained for cases with different thicknesses. In this context the aim of the current study is to address this extrinsic type size effect through crystal plasticity simulations. A series of local crystal plasticity finite element simulations are conducted for different values of t/d ratio in tensile specimens. Different granular morphologies of polycrystalline samples are generated using Voronoi tessellation and tested under axial loading conditions. The macroscopic influence of varying t/d ratio is studied in detail and compared with the experimental findings in the literature.