Design of thermal-invariant metastructures for machine tools via additive topology optimization

In high-precision mechanical systems, such as machine tools, thermal deformation significantly impacts accuracy. This paper proposes a novel concept of additive topology optimization, which embodies a dual meaning: not only “add material” to an existing structure, but also “add functionality” to enhance the thermal performance of the system. In this framework, thermal deformation is mitigated by strategically adding a material with a different thermal expansion coefficient to an existing machine tool structure, thereby enriching its functional properties rather than merely modifying its geometry. The objective is to control thermal deformation by minimizing the relative changes in distance and angle between the tool and the table, while maintaining precision under thermal loads. The proposed additive approach enables the extension of structural functionality without compromising the original stiffness of the base design. The validity and effectiveness of the proposed concept is demonstrated through three-dimensional numerical examples.