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Exothermic- insulating sleeves are used to increase the yield in foundry practice. Function of the sleeve is predominant to enhance the effective casting modulus by increasing feeding efficiency. This is represented by a modulus extension factor (MEF) and shrinkage porosity of the casting. The use of an exothermic - insulating sleeve as a substitute for sand feeder can increase efficiency by up to 60%. However, exothermic-insulating sleeve in use today is imported and has limited range of shapes and sizes so that the cast steel products is limited. The research is intended to produce a variety of shapes and know about the effect of that to casting yield of C8000 cast steel. For this research the exothermicinsulating sleeve make use local and imported resource material. The research starts with the study of shape variations which are widely applied. The constant modulus will be used as a basic for the further design of the sleeve. Molten metal is poured for trials with and without the test sample (the casting) which is followed by feeder cooling rate measurement to find the value of modulus extension factor (MEF). To analyze the effect of efficiency other testing plate test is applied involving shrinkage cavity visual testing, and yield calculations. These results show that the dome - shape performed the best efficiency in the holding time, temperature above the solidus temperature (above 1360 °C) for 360 second, the shape of the cavity shrinkage apparently, highest MEF (2,02 times larger than sand riser), 90% in yield. These results which performed was accepted for exothermic-insulating properties of Indian standard