The Institute of Hydrodynamics in cooperation with the Department of Production Engineering, Faculty of Technology, Tomas Bata University in Zlin, Czech Republic and the Department of Chemical and Food Engineering, University of Salerno, Italy, developed a model for prediction of viscosity of highly concentrated suspensions used in production of fine metal or ceramic parts applied in transport, arms and electrotechnical industry, medicine appliances or clockmaking. The research results were published in the renowned journal Ceramics International.
Technique for production of highly precise parts with excellent surface quality
Powder injection (nano-/micro-particles) into moulds - PIM (Powder Injection Moulding) -represents a modern technique for production of fine metal or ceramic parts, where nano- or micro-particles from various materials, either metal-based - MIM (Metal Injection Moulding) or ceramics-based (Ceramic Injection Moulding), are compacted by polymer binders as a source material. The produced parts exhibit top quality of their surface and particularly, shape complexity. Moreover, production costs are non-negligibly lower in comparison with the classical methods of machining and casting. In addition, a final part of complex shape is produced in one step contrasting to the classical methods assembling the geometrically simpler individual parts.
The PIM process is composed of four consecutive steps: 1) even distribution of entry feedstock components containing nano- or micro-particles, polymer binder of organic origin (paraffin, poly(ethylene glycol)) and surfactant contributing to higher packaging (45-75 %) of a feedstock; 2) injection moulding of plasticized suspensions; 3) debinding; 4) sintering. It is valid generally that every defect in a production line is consequently propagated and there is no way how to suppress it in the consequent steps.
Knowledge of suspension viscosity is fundamental
Correct simulation for every suspension with the given composition is necessary for successful injection moulding, i.e. a simulation of the second basic step. Here, viscosity plays a crucial factor. Its determination is usually expensive and time consuming. Moreover, with any (negligible) change of suspension composition it is necessary to carry out a new experimental determination. Hence, a possibility of viscosity prediction makes the PIM process much easier and cheaper.
The objective of the published research is a presentation of continuous prediction of viscosity of suspensions composed of metal nanoparticles (Al2O3) in the range 0-50 % and surfactant in the range 0-5 %. The mean deviation of prediction attains 6 %, the value comparable with an experimental inaccuracy.
Source: P. Filip, B. Hausnerová, C. Barretta - Master flow curves as a tool to modelling ceramic injection molding. Ceramics International 2019, in press.
Capillary rheometer Göttfert for viscosity measurement
Ceramic parts made by CIM
Metal parts made by MIM
Source: Pan Taiwan Enterprise Co., Ltd.