| Cavity Insert | Forms the external surface and visible details of the moulded part. | Pre-hardened tool steel, hardened tool steel, or corrosion-resistant mould steel. | Approximately 28–52 HRC, depending on production volume and wear requirements. | Usually ±0.01–0.05 mm for precision features; project requirements may vary. | About Ra 0.05–1.6 µm, depending on polishing, texture, or machining requirements. | Visible housings, covers, containers, automotive trim, medical components, and consumer products. | Prioritise cosmetic quality, venting, cooling uniformity, steel corrosion resistance, and repairability. |
| Core Insert | Forms the internal surfaces, cavities, holes, walls, and functional geometry of the part. | Pre-hardened or hardened tool steel; corrosion-resistant steel is often selected for demanding environments. | Approximately 28–52 HRC, with higher hardness used for abrasive materials or long runs. | Usually ±0.01–0.05 mm for critical internal dimensions and alignment features. | About Ra 0.10–1.6 µm; polished surfaces can improve part release and internal appearance. | Internal bores, ribs, bosses, threaded features, fluid channels, and hollow moulded parts. | Check draft angles, ejection clearance, core cooling, alignment, deflection control, and accessibility for maintenance. |
| Forming Insert | Creates a local feature or replaceable detail such as a rib, logo area, texture, slot, or undercut. | Tool steel, stainless mould steel, powder metallurgy steel, or carbide for highly abrasive details. | Approximately 40–62 HRC, selected according to wear, impact, and moulding material. | Usually ±0.005–0.03 mm for replaceable precision details. | About Ra 0.05–1.6 µm, including polished, machined, etched, or textured surfaces. | Interchangeable details, serial-number areas, special textures, thin ribs, inserts, and high-wear regions. | Evaluate interchangeability, locking method, thermal expansion, spare-part availability, and ease of replacement. |
| Slide or Lif ter Insert | Produces side actions, undercuts, lateral holes, and features that cannot release in the main opening direction. | Pre-hardened or hardened tool steel with wear-resistant sliding surfaces. | Approximately 38–54 HRC. | Typically ±0.01–0.04 mm for mating and functional features. | About Ra 0.20–1.6 µm on sliding and forming surfaces. | Snap-fits, side holes, hooks, handles, undercuts, and complex external geometry. | Review stroke length, lubrication, wear plates, locking strength, timing, and risk of flash at shut-off surfaces. |
| Gate Insert | Controls the entry of molten plastic into the cavity and helps define the gate mark. | Hardened tool steel or wear-resistant steel. | Approximately 45–60 HRC. | Typically ±0.005–0.02 mm at the gate and sealing interface. | About Ra 0.10–0.80 µm in the melt-flow area. | Hot-runner systems, cold-runner systems, precision parts, and applications requiring controlled gate appearance. | Confirm gate type, resin compatibility, shear sensitivity, maintenance access, and replacement procedure. |
| Wear Insert | Protects high-wear or high-impact areas and allows damaged sections to be replaced without rebuilding the full mould. | Hardened tool steel, powder metallurgy steel, carbide, or other wear-resistant alloys. | Approximately 50–65 HRC, depending on the selected material and heat treatment. | Typically ±0.01–0.03 mm for mating and forming surfaces. | About Ra 0.10–1.6 µm. | Glass-filled plastics, abrasive compounds, repeated shut-offs, thin edges, and high-cycle moulds. | Compare wear resistance, toughness, brittleness, coating compatibility, replacement cost, and expected service life. |