Invalid Topology Optimazation

[henriqueoliveirapsiva9]

Hello ANSYS Community, I'm working on a university project involving topology optimization of a 3D-printed PLA support structure. The goal is to minimize material usage while achieving a specific displacement (1.5 mm in -y direction) under a static load from a 3 kg mass, with stress constraints based on PLA yield strength and a safety factor of 1.5.
The Constraints: Max von Mises stress < PLA_yield / 1.5
Minimum wall thickness: 1 mm (in-plane)
Constant out-of-plane thickness: 4 mm
Design space: 120×120×4 mm block with some excluded regions (hole in the middle and squares on the bottom) also with Frictionless Support on two lateral faces and an mandatory shape in the middle






Issue: When setting up the Structural Optimization in ANSYS Mechanical (2025 R1), I encounter an error of" Optimization Region Error: text "Invalid Optimization Region" This occurs even after carefully defining: Design Region and Exclusion Regions, idk what to do really, if someone have any advice to give to me i would gladdly accept.