Production of small metallic periodic structures by investment casting: Investigations of the technical limits

The development of additive manufacturing (AM) has led to a wider range of applications for traditional investment casting (IC). This work seeks to at studying the castability of metals using additive manufacturing assisted investment casting (AM-IC). Cast tests with designed 2D and 3D patterns of aluminum (Al), copper (Cu), and stainless steel were initially conducted to investigate the factors affecting the castability of these metals, aiming to produce very small parts with wall thicknesses of less than 1 mm. Then, more complex periodic foam patterns were produced using AM-IC. Several experimental limitations, such as printing file size, printer accuracy and mold and casting temperatures, were considered to successfully reduce the unit cell size of the Cu foam. Results show that the casting infiltration distance is improved when metal casting temperature increases and when the temperature difference between the mold and the metal decreases. Optimizing unit cell geometry and parametric modeling are potential pathways to reduce the 3D printing digital file size of foams with small unit cells. The foam printed accuracy varies depending on the 3D printing machines. The infiltration efficiency is improved by optimizing the cast tree geometry. Finally, periodic Cu foams with a unit cell size of 2 mm, in a part with a 30 mm diameter, 30 mm height, wall thickness of less than 100 μm, and a metal-to-porosity ratio of 10/90 by volume were successfully cast via AM-IC. • Investigating castability of aluminum, copper and stainless steel in fine structures • Strategies considering 3-D printing and casting to produce Cu foams with small unit cell size by investment casting • Controllable manufacturing of copper foams with micro strut thickness and high porosity