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Chemical bonded resin sand mould system has high dimensional accuracy, surface finish and sand mould properties compared to green sand mould system. The mould cavity prepared under chemical bonded sand mould system must produce sufficient permeability and hardness to withstand sand drop while pouring molten metal through ladle. The demand for improved values of permeability and mould hardness depends on systematic study and analysis of influencing variables namely grain fineness number, setting time, percent of resin and hardener. Try-error experiment methods and analysis were considered impractical in actual foundry practice due to the associated cost. Experimental matrices of central composite design allow conducting minimum experiments that provide complete insight of the process. Statistical significance of influencing variables and their interaction were determined to control the process. Analysis of variance (ANOVA) test was conducted to validate the model statistically. Mathematical equation was derived separately for mould hardness and permeability, which are expressed as a non-linear function of input variables based on the collected experimental input-output data. The developed model prediction accuracy for practical usefulness was tested with 10 random experimental conditions. The decision variables for higher mould hardness and permeability were determined using desirability function approach. The prediction results were found to be consistent with experimental values.

Currently offered devices for the hardness measuring or indices of the mould strength, are presented in the hereby paper. The presented results allow to compare approximately the indications of individual devices of different types.The description of the author’s own microprocessor tester for the quality assessment of the sand foundry moulds, is shown. On the bases of the measurements results it is possible, to evaluate indirectly, the mould apparent density in the selected points, as well as several other properties.

Currently offered devices for the hardness measuring or indices of the mould strength, are presented in the hereby paper. The presented results allow to compare approximately the indications of individual devices of different types. The description of the author's own microprocessor tester for the quality assessment of the sand foundry moulds, is shown. On the bases of the measurements results it is possible, to evaluate indirectly, the mould apparent density in the selected points, as well as several other properties. [ABSTRACT FROM AUTHOR]

Experimental investigations were carried out to determine the influence of cement-silica ratio on the moulding properties of Portland cement bonded sand. Test specimens, comprising silica sand and additives, namely wood flour and dextrin, as well as molasses, with varying cement to silica sand ratio (RCS), were prepared. The specimens were subjected to tests in accordance with American Foundrymen's Society (AFS) standard procedure to determine properties such as bulk density, mould hardness, permeability, compression strength and shear strength. Findings revealed that RCS and additives have significant effects on all properties developed in the moulding sand. As RCS increases, the bulk density, mould hardness, green compression strength and shear strength increases while permeability and shatter index decreases. However, RCS of 0.105 gives suitable properties for moulding work meant for iron castings. [ABSTRACT FROM AUTHOR]