Understanding Injection Mold Structure in One Article | Essential Tips for Molders
Time：2026-09-01 08:34:51 / Popularity： / Source：
Today, we'll provide a comprehensive overview of structure of common injection molds in an easy-to-understand manner. Whether you're a mold novice or a seasoned practitioner looking for a refresher, this article is worth saving!
▲Figure 1 Mold Structure
I. Basic Structure of Injection Molds
Generally speaking, injection molds consist of several major components: molding system, gating system, ejection system, positioning and guiding, cooling system, exhaust system, and mold base structure.
1. Molding System (Cavity and Core)
This is core component of mold, directly determining shape, size, and surface quality of product.
Front Mold (Cavity/Mother Mold): This component forms product's outer shape and is typically located on fixed mold side. Depending on product's structural shape, options include integral cavity, integral embedded cavity, inlay cavity, and threaded cavity.
1. Molding System (Cavity and Core)
This is core component of mold, directly determining shape, size, and surface quality of product.
Front Mold (Cavity/Mother Mold): This component forms product's outer shape and is typically located on fixed mold side. Depending on product's structural shape, options include integral cavity, integral embedded cavity, inlay cavity, and threaded cavity.
▲Figure 2: Integral Cavity
▲Figure 3: Integral Embedded Cavity
▲Figure 4: Partially Inlaid Cavity
▲Figure 5: Four-Sided Inlaid Cavity
Back mold (core/male mold): forms product's internal structures, such as holes and slots. It is primarily classified into integral embedded and inlaid combination types and is typically located on movable mold side.
Back mold (core/male mold): forms product's internal structures, such as holes and slots. It is primarily classified into integral embedded and inlaid combination types and is typically located on movable mold side.
▲Figure 6: Embedded Core
▲Figure 7: Inlaid Core
Complex products also utilize inserts, sliders, lifters to address features like undercuts and side holes.
Complex products also utilize inserts, sliders, lifters to address features like undercuts and side holes.
▲Figure 9: Lifter
✅ Key Design Points: Optimal parting surface selection, adequate draft angle, and uniform wall thickness.
2. Gating System
Responsible for directing molten plastic from injection molding machine nozzle to individual cavities. Main Components:
Main Runner: The first channel connecting injection molding machine nozzle to mold.
Subrunner: Distributes plastic to individual cavities. Gate: "Entrance" for plastic into mold cavity. Common types include point gates, side gates, and latent gates.
Cold well: Collects cold slugs ahead of mold cavity to prevent them from entering mold cavity and affecting quality.
✅ Key Design Points: Optimal parting surface selection, adequate draft angle, and uniform wall thickness.
2. Gating System
Responsible for directing molten plastic from injection molding machine nozzle to individual cavities. Main Components:
Main Runner: The first channel connecting injection molding machine nozzle to mold.
Subrunner: Distributes plastic to individual cavities. Gate: "Entrance" for plastic into mold cavity. Common types include point gates, side gates, and latent gates.
Cold well: Collects cold slugs ahead of mold cavity to prevent them from entering mold cavity and affecting quality.
▲Figure 10: Schematic diagram of gating system
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