THE EFFECT OF ADDITIONAL VARIATIONS OF FLY ASH & BENTONITE ON THE PROPERTY AND DEFECTS OF GASHOLES ON THE RESULTS OF ALUMINUM METAL CASTING

Abstract

The objectives of this study to describe: (1) The effect of adding fly ash and bentonite to the permeability of molding sand. (2) The effect of adding fly ash and bentonite to the moisture of molding sand. (3) The effect of adding fly ash and bentonite to gas holes defect on aluminum metal casting. This study is conducted at Polytechnic of Manufaktur Ceper, Klaten. The method used is the pre-experimental design which one-shot case study design. The compositions of the molding sand are varied is fly ash and bentonite. The Sample variations are divided into 4 types based on fly ash and bentonite concentration. The comparison of fly ash and bentonite concentration are: variation A are 0%:9%, variation B are 1%:8%, variation C are 2%:7%, and variation D are 3%:6%. The tests which are done in this study such as permeability test by using permeability tester, moisture test by using moisture tester, and holes defect test by using visual observation and calculation of gas holes defect. The results showed that: (1) adding fly ash and bentonite can decrease the permeability values of molding sand. The lowest permeability values occur at variation D that is 85.34 cm3 /min. (2) Adding fly ash and bentonite can decrease the moisture of molding sand. The lowest moisture values occur at variation D that is 5,26 %. (3) Adding fly ash and bentonite can improve the quality of castings. The results of castings at variation B which adds fly ash and bentonite have fewer gas hole defects compared with a variation which no adding fly ash that is 3,15 cm³.