investment casting

J-F. Charmeux (a), R. Minev (a), S. Dimov (a), E. Minev (a)
(a)Manufacturing Engineering Center, Cardiff University, Cardiff, CF24 3AA, UK

Abstract

Producing micro-castings trough vacuum investment casting is known to be associated with high cooling rates due to small scale of the castings. High cooling rates together with alloy composition might be the main factors affecting the final metallographic structure of castings’ alloys during the solidification process. When using Al-Si-Mg casting alloys, the size of the dendritic structure can be used for a non-destructive test to assess the mechanical properties and overall quality of the castings. Also the ability of the alloys to be structured by different mechanical and energy assisted processes is highly dependant on their metallographic structure. Based on earlier experimental results, this paper proposes an empirical model describing the degree of dendrite cell refinement in cast microfeatures as a function of their AR and mould pouring temperature. Additionally, the paper reports the strong correlation between the DCS refinement and the changes in the mechanical properties of the castings through MHV measurements following a Hall-Petch equation type.

J-F. Charmeux (a), R. Minev (a), S. Dimov (a), E. Minev (a), S. Su (a), U. Harrysson (b)

a Manufacturing Engineering Center, Cardiff University, Cardiff, CF24 3AA, UK
b Fcubic, Kallarlyckevagen 6, 42935 Kullavik, Sweden

Abstract

The paper investigates the capability of a new technology, ‘Fcubic’, for a faster and less expensive production of investment casting shells directly from CAD data for the manufacture of micro-components. The technology utilises high resolution 3D printing heads for building shells using zirconia ceramics.

The capabilities of the ‘Fcubic’ process are compared to those of classical two-stage lost wax processes to produce metal micro-components. The tests are carried out on a machine incorporating units for centrifugal and pressure/vacuum casting specially developed to facilitate the replication of components with small features. In particular, this comparative study involved the manufacture of test parts in aluminium/zinc alloys and stainless steel with micro-features in the range of 250 to 700 μm and aspect ratios up to 2.4. The dimensional accuracy and the surface quality of the produced parts were measured. In addition, the production cost of the two different manufacturing routes was assessed to determine the economic viability of the ‘Fcubic’ direct shell technology for casting components incorporating micro-features.