Structural stability study using thermal and structural analysis of a bimetal cylinder in an injection molding machine

There are two sections in an injection molding machine: the injection unit and the clamp unit. Solid plastics are melted in the injection unit using heat from a band heater and from frictional heat between the resins and between the resin and the inside surface of the cylinder or screw surface. When the melted resin is injected into the mold, which has a unique geometry, high pressure is developed at the fore-end of the cylinder, which can cause damage to the cylinder. The bimetal cylinder consists of two layers and is manufactured to sustain the pressure inside the cylinder and prevents abrasion. This study was conducted to analyze the structural stability of the bimetal cylinder. Computer simulation has been performed through structural analysis coupled with thermal analysis using a commercial FEM program. Thermal analysis showed that a temperature distribution occurred within the bimetal cylinder. Structural analysis was used to obtain stress and deformation occurring at the fore-end of the bimetal cylinder in relation to heat and injection pressure, and showed that the stress in the bimetal cylinder is influenced by the injection pressure more than the high temperature. However, the deformation of the bimetal cylinder was found to be dominated by thermal expansion in relation to high temperature, more than by injection pressure.