| Core | Forms the internal side of a moulded part and occupies the negative space inside the product. | Internal walls, holes, ribs, bosses, channels, and other recessed features. | Transfers its machined, polished, textured, or coated surface to the inside of the part. | Pre-hardened tool steel, hardened tool steel, stainless tool steel, or aluminium for lower-volume tooling. | Must allow adequate draft, support cooling requirements, resist wear, and maintain alignment with the cavity. |
| Cavity | Forms the external side of a moulded part and defines the outside envelope. | Outer contours, raised features, decorative details, logos, and visible part surfaces. | Usually determines the appearance of the visible surface, including gloss, texture, and pattern definition. | Tool steel for production moulds; aluminium may be used for prototypes or shorter production runs. | Requires careful control of polish, texture, parting lines, venting, cooling, and shrinkage allowance. |
| Replaceable Insert | Creates a removable section within the core or cavity for a local feature or a high-wear area. | Small pockets, ribs, lettering, holes, undercuts, shut-offs, and complex local details. | Allows a specific area to receive a different polish, texture, coating, or repair treatment. | Hardened tool steel, stainless steel, copper alloys for thermal performance, or wear-resistant tool materials. | Should be accurately located, securely retained, easy to remove, and designed to avoid visible mismatch lines. |
| Interchangeable Insert | Permits selected geometry to be changed without manufacturing an entirely new mould base. | Product variants, cavity identification features, alternative logos, and model-specific details. | Supports consistent finishing across product versions while allowing individual inserts to be refinished or replaced. | Pre-hardened or hardened tool steel, selected according to production volume, wear, and surface requirements. | Interface dimensions and datum locations must be repeatable to prevent steps, gaps, or mismatch at the part surface. |
| Slide or Side Core | Forms features that cannot be released directly along the main mould-opening direction. | Side holes, transverse slots, hooks, snap features, and undercut geometry. | Maintains the required finish on side surfaces while controlling witness marks at the sliding interface. | Hardened tool steel or wear-resistant steels, often with treated sliding surfaces. | Needs reliable guidance, lubrication, wear control, correct shut-off angles, and sufficient clearance for movement. |
| Texture or Pattern Insert | Applies a controlled decorative or functional pattern to a selected mould surface. | Grain patterns, fine textures, grip areas, matt zones, and visual contrast features. | Directly establishes the replicated texture; the final result also depends on mould temperature, filling, and material behaviour. | Tool steel or stainless tool steel with chemically etched, laser-textured, blasted, or chemically treated surfaces. | Texture depth, draft angle, cleaning access, and alignment must be controlled to prevent distortion or gloss variation. |
| Cooling Insert | Improves heat removal near thick sections, deep cores, or geometrically difficult areas. | Does not normally define visible geometry; it supports the moulding of surrounding features. | Helps reduce uneven cooling, sink marks, warpage, and local gloss differences when properly designed. | Tool steel, copper alloys, or other thermally conductive mould materials selected for the application. | Channel location, sealing, corrosion resistance, pressure capability, and cleanability are important factors. |