Investigating Manufacturing Effects on Lattice Shear & Compression Strength in DMLM

This study compares compression and shear properties of a lattice manufactured across a range of additive process conditions. The Direct Metal Laser Melting (DMLM) additive manufacturing process has traditionally emphasized achieving the highest tensile strength. While tensile testing is a quick and straightforward method, it does not accurately replicate the complex failure modes seen in lattice structures. Following an assessment of the fatigue and tensile performance of solid structures, we focused on characterizing lattice samples produced under similar conditions.
To evaluate the shear performance of lattice samples printed and annealed under various conditions, we employed an internally developed lattice punch test. The same conditions were used to manufacture lattice cubes that were subsequently tested according to draft ISO/ASTM 52959, ‘Additive manufacturing – Test Artifacts – Compression Validation Coupons for Lattice Designs’.

Samples were produced on a Renishaw RenAM 500Q additive manufacturing system utilizing Ti-6Al-4V ELI powder conforming to ASTM F3001 and printed at a 60-micron layer height. Laser power and anneal temperature were the processing parameters chosen for investigation in the format of a central composite design (CCD) experimental framework.

Results indicate that laser power and anneal temperature have a statistically significant impact on lattice shear strength, while only laser power resulted in a statistical significance in compression testing. Analysis indicates that in this study, low laser power and low anneal temperature resulted in the lowest lattice shear strength. Low laser power also resulted in the lowest compression strength. Additionally, our analysis revealed that the mass of compression samples correlated more closely with laser power than with any other evaluated property.

Finally, we will compare these results to the tensile and fatigue properties of solid structures produced under the same manufacturing conditions and look for correlations.