Development of an Integrated System for the Automatic Viscosity Correction of a Ceramic Slurry for the Investment Casting Process

Background: Starting from a wax model of the mold, which is later discarded, investment casting is used to make almost finished metal cast parts. The term "investment casting" is derived from the use of a ceramic liquid mixture (slurry), in which the model is repeatedly immersed (invested) to form, layer by layer, the shell which has to be filled with molten metal. The liquid of the slurry tends to evaporate so that the viscosity of the former increases and a correction is needed. Objective: The study aimed to investigate the simplest way to measure slurry viscosity and automatically correct it. Methods: Numerical and experimental tests have been implemented to correctly assess the proposed method. An integrated system for the automatic correction of slurry viscosity is realised which comprises: a reservoir of slurry including means for mixing it; a transducer which continuously measures the slurry viscosity; a pump that gradually feeds the diluent into the slurry to keep its viscosity constant; and a device, governed by the continuous viscosity measurement, that operates the pump. Results: It has been proved that the developed system is able to integrate the slurry viscosity continuous measurement with gradual addition of diluent into the slurry, so as to have a fully automated operation that can make corrections, whenever necessary, on the basis of the transducer output. Conclusion: The developed system works properly by keeping the slurry viscosity within a fixed range. A patent has been recently deposited to protect the integrated system for the automatic correction of slurry viscosity.