Core & Cavity

The master forms that create the part's geometry. The cavity forms the part's outer surface; the core forms the inner surface.

Mold Base

A standardized frame that holds all the custom-machined components. It is typically purchased as a pre-made unit, saving cost and time. It includes plates like the "A" and "B" plates.

Sprue Bushing

A hardened steel nozzle that connects the mold to the injection molding machine's nozzle, channeling molten plastic into the mold.

Runner System

The network of channels that carries molten plastic from the sprue to the part cavities.

Gates

The small, controlled entrance points from the runner into the part cavity. Gate design is critical for controlling plastic flow and part quality.

Ejection System

The mechanism that pushes the cooled part off the core after the mold opens. It includes:
• Ejector Pins: The most common method.
• Ejector Sleeves: Used for cylindrical features.
• Ejector Plates: The plates that actuate the pins.
• Return Pins: Push the ejection system back as the mold closes.

Cooling (Temperature Control) System

A series of channels drilled through the mold plates and core/cavity blocks. Circulating water or oil through these channels controls the mold temperature, which is vital for cycle time and part quality.

Venting

Very shallow channels (often only 0.01-0.03 mm deep) cut into the mold to allow trapped air to escape during injection, preventing defects like burns or short shots.

Guide Pins/Bushings

Precision components that ensure the two halves of the mold align perfectly each time they close.

Two-Plate Mold

The simplest and most common type. The runner system and parts are on the same parting line and are ejected together.

Pros: Simple design, lower cost.
Cons: Manual separation of parts from runners is required.

Three-Plate Mold

Features two parting lines. One opens to eject the runner system, and a second opens to eject the part. This allows the gate to be located away from the part's edge.

Pros: Automatic degating (runners separate from parts), gates can be placed at optimal locations.
Cons: More complex, expensive, and higher maintenance.

Hot Runner Mold

The runner system is heated and remains in a separate, heated manifold plate, so the plastic within it stays molten. No runner is ejected.

Pros: No scrap runners, faster cycle times, fully automated.
Cons: Highest cost, more complex to set up and maintain, potential for material degradation.

Prototype / Soft Tooling

Aluminum, mild steel, 3D printed metal/epoxy.

1 - 10,000 shots

Low-volume production, prototyping, and market testing. Faster and cheaper to build.

Production / Hard Tooling

Hardened Steel (e.g., P20, H13, S7).

1,000,000+ shots

High-volume mass production. Highly wear-resistant but takes longer and costs more to build.

Parting Line (PL)

The visible line on the part where the two mold halves meet. Its location is a critical design decision.

Draft Angle

A slight taper (typically 1°-3°) applied to walls parallel to the mold opening direction. Essential for easy part ejection.

Shrinkage

The reduction in volume of the plastic as it cools. The mold must be built larger than the final part dimension to compensate for the specific plastic's shrinkage rate.

Undercut

A feature on the part that prevents its direct ejection from the mold (e.g., a side hole, a hook). Requires special mold features.

Lifter

A component that moves at an angle to release an undercut as the mold opens or during ejection.

Slide (or Cam)

A component that moves perpendicular to the mold opening direction to form undercuts on the side of a part.

Texture (EDM, Etching)

The process of applying a surface finish (e.g., leather grain, matte finish) to the mold cavity, often via Electrical Discharge Machining (EDM) or chemical etching.

Mold Flow Analysis

Computer simulation software used during the design phase to predict how the plastic will fill the mold, allowing engineers to optimize gate location, cooling, and prevent defects.