Differences in precision of wax molds made of portland cement and silicone rubber in investment casting process for economic efficacy

Abstract

The investment casting method has several advantages, namely the ability to mold complex objects, create products smooth surface and high precision. This is closely related to the wax pattern used, if the wax already has a precision geometry with a precise shrinkage estimation during the casting process, the product will be in accordance with the plan, and vice versa. This study compares the level of roughness and precision of wax molds made of Portland cement and Silicon Rubber. The first step was making a product design with CAD, the product pattern to be made was the origami crash box with a thickness of 3 mm. The second step, converting the CAD file to .stp/.step then printing the design with 3D Printing. The third step, duplicating the 3D printing results with Portland cement material on the first mold and silicone rubber on the second mold. The first mold was designed with the assembly method, the assembly will be carried out after the first part and the second part have been finished. The fourth step was pouring wax that has been mixed with dammar gum (Shorea javanica), onto each gate that has been designed. The study found that the percentage difference between design and cement was 14.7% while the difference between design and RTV Silicon Rubber was 2.7%. This proves that RTV Silicon Rubber can form more precise patterns than cement. RTV Silicon Rubber mold is able to form complex patterns. The surface roughness adjusts to the imitated pattern, if the pattern is smooth then the surface produced by RTV Silicon Rubber mold is smooth, and vice versa.