Holes can be created in several ways, using:
• Through pins
• Cores
Care must be taken to provide the necessary draft angles and an adequate heat transfer. To improve the heat transfer the core must be produced with half on one section of the mould and half on the other section. Where ever possible a hole should be included inside the core to further improve the air flow.
• Insulation panels
These are used to thermally insulate areas of the mould and create colder areas where the material does not adhere to the surface of the mould. To obtain this, a sheet of PTFE (Teflon) or a mineral wool layer is usually used. They are designed smaller than the required hole since the immediately surrounding area will have a thinner wall (which will be removed).
• Knife edge