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Metal Casting I—Casting Fundamentals
Published in Zainul Huda, Manufacturing, 2018
Investment casting, also called lost-wax casting, is an expandable mold casting process that involves the use of a wax pattern that melts out (lost) during casting. In this process, first a wax pattern is coated with a refractory ceramic material that is hardened with time, and the internal geometry of the ceramic coating takes the shape of the casting (mold cavity). The mold is then inverted and heated so that wax is melted out of the cavity. Then the mold is held upright and molten metal is poured into the cavity formed due to melting of the wax. On completion of solidification within the ceramic mold, the metal casting is removed.
Evaluation of graphite and TiO2 as susceptors for microwave dewaxing in ceramic shell casting processes of artworks
Published in Journal of Microwave Power and Electromagnetic Energy, 2022
I. Pérez-Conesa, J. Fayos-Fernández, J. A. Aguilar Galea, J. Monzó-Cabrera, R. Pérez-Campos
The main objective of the foundry sector is the creation of metal pieces by pouring liquid metal into refractory molds. In the lost wax casting technique, the wax model that acts as a support of the refractory mold is eliminated, so that the metal can be poured into the space that the wax was occupying previously, as described in (Sias, 2005). Dewaxing is a step previous to melting and casting of the metal and is also the most complicated and delicate action of the process. Davey (2009), explains that its success is conditioned to the removal of the moisture from the mold and any traces of wax, since the gasification of wax, which is combustible, would cause serious damages in the ceramic negative, ruining the whole operation. In ceramic husk technology, dewaxing is the most critical phase, with thermal shock technique being the most efficient, economical and technically safe method of extracting wax, although it involves risks to infrastructures, spaces and, more seriously, to working operators as stated by (Chica et al. 2013).
Investigation of ablation studies of EPS pattern produced by rapid prototyping
Published in Virtual and Physical Prototyping, 2018
Ranjeet Kumar Bhagchandani, Sajan Kapil, Pushkar Kamble, K. P. Karunakaran
Conventional investment casting (lost wax casting) involves a complex stage of de-waxing the consumable wax pattern prior to pouring molten metal. While in evaporative pattern casting (EPC) process, expanded polystyrene (EPS) is used for the consumable pattern, which starts evaporating as soon as molten metal is poured. Guler et al. (2011) proposed a novel approach for eliminating the inadequacy of lost wax casting, where EPS was used as a sacrificial pattern in investment casting and was removed using acetone. Fabrication of complicated functionally bi-metallic castings proves the capability of the EPC process (Jiang et al. 2013, Jiang et al. 2015, Jiang et al. 2016). Conventional EPS pattern forming needs three steps: making a pre-puff of appropriate density via pre-expansion of expandable polystyrene beads followed by stabilisation or aging and finally moulding of the foam beads into the desired pattern shape. The process demands both complicated tooling (i.e. dies), as well as controlling multiple parameters to produce acceptable quality patterns. Rapid prototyping (RP) facilitates exploring unconventional pattern-making, which involves heated wire/ribbon-based cutting tool and is used for EPS carving to achieve very high feedrate with low cutting forces. Wire slicing is fast and accurate enough in production of bulk qualitative EPS patterns. Chen et al. (2013) summarised foaming, moulding, manual cutting, CNC machining and RP in existing processes. Hot-tool cutting is a resolution for rapid manufacturing of EPS patterns with complex geometries, sizes and profiles, facilitating substantial reduction in time consumption and power requirement. The slicing process entails a cutting element (wire), whereby electric current is passed, and thus altering the physical properties of the foam. Characterisation of diverse EPS plastic cutting has been formerly scrutinised by researchers (Mehta et al. 1995, Aitchison et al. 2007). The efficacy of slicing process could be elucidated by the dimensional accuracy of the end product, which successively depends on the kerfwidth, stipulated as the width of the material removed during cutting process. Kerfwidth is directly proportional to the offset given to the tool and is inversely proportional to the accuracy achieved for intricate shape.