Mulling and its Effect on the Properties of Sand-Water-Bentonite Moulding Mixture

Today, foundries are facing increasing demands for greener and more economical production while maintaining or improving the quality of the castings produced. The importance and use of green sand mixtures using bentonite as a binder are thus coming to the fore once again. They have the advantage of both eliminating the chemicalization of production and also allowing the immediate use of the already used mixture, including the binder, after adjustment of the composition and mulling. In order to maintain the quality of the resulting castings, it is necessary to monitor the properties of the moulding mixture through a series of laboratory tests. It is also essential to look at the processing quality of these mixtures, i.e. the combination of good mulling quality and efficient mulling time, which is often neglected. It is the quality of mulling and the effective mulling time that help to develop the bonding properties of the bentonite, improve the properties of the mixture, determine the efficiency of the muller and possibly reduce the time and energy required for mulling. The aim of this work is to present the effect of mulling on the properties of sand-water-bentonite mixtures. The properties studied are mainly the compactability, strength characteristics, moisture content of the mixture and the order of addition of raw materials.