Views: 0 Author: Site Editor Publish Time: 2026-02-02 Origin: Site
Two-Plate Mold:
Structure: It has only one main parting line, splitting the mold into a moving half and a fixed half. The runner system and the part cavity are on the same side (typically the moving side).
Opening: A single, direct opening motion. The part and the solidified runner are pulled out together and then ejected as one piece.
Three-Plate Mold:
Structure: It features two parting lines, splitting into three plates during opening:
Opening: A two-stage sequence, controlled by limit rods or springs.
Stage 1: The A and B plates separate, mechanically pulling and shearing the pin-point gate, causing the runner to drop away.
Stage 2: The B and C plates (main parting line) separate, allowing the part to be ejected from the core side.
The "A" plate (fixed, holds the runner).
The "B" plate (floating, holds the part cavity).
The "C" plate (moving, holds the cores).
This is the primary reason for choosing one over the other.
Two-Plate Mold:
Gate Type: Uses edge gates (submarine gates), direct sprue gates, or fan gates.
Characteristic: The gate has a larger cross-section. The runner remains attached to the part after ejection, requiring secondary operations (manual clipping, die-cutting, or robotic trimming). This leaves a more noticeable gate vestige.
Three-Plate Mold:
Gate Type: Designed for pin-point gates.
Characteristic: The gate is very small (typically Ø0.5-1.5mm). It shears off automatically during the first stage of opening, leaving only a tiny, cosmetically acceptable mark on the part. No degating is required.
| Feature | Two-Plate Mold | Three-Plate Mold |
|---|---|---|
| Complexity | Simple, robust, reliable. | Complex. More components, extra plates, and mechanisms. |
| Tooling Cost | Lower. Less steel, simpler machining. | Higher (often 20-30% more). More steel, complex build. |
| Cycle Time | Potentially faster. Shorter opening stroke. | Slightly longer. Two-stage opening, longer stroke. |
| Degating | Manual/Secondary process required. | Fully automatic. Runner and part fall separately. |
| Gate Vestige | More visible. Affects cosmetics. | Minimal. Superior surface finish for appearance parts. |
| Gate Location | Restricted. Typically from the part edge or side. | Highly flexible. Can gate on any flat surface, even the center of a part. |
| Maintenance | Easier, longer service life. | More frequent. Small rods, bolts, and plates are wear points. |
| Best For | High-volume, cost-sensitive parts where gate appearance isn't critical. | Appearance-critical parts, center-gated items, multi-cavity family molds. |
Use this logic for your next project:
Choose a TWO-PLATE Mold when:
The gate can be hidden on a non-appearance surface.
The part design allows for easy filling from the edge.
Tooling budget is a primary constraint.
You need maximum mold rigidity for large parts.
Choose a THREE-PLATE Mold when:
The part surface is cosmetic (e.g., consumer electronics, lenses, transparent parts).
You need center gating for symmetrical flow (e.g., round covers, gears).
You're running a high-cavitation mold and need balanced runners.
Your goal is full lights-out automation with no manual degating.
Think of it as a fundamental trade-off:
Two-plate molds prioritize simplicity, speed, and low cost.
Three-plate molds prioritize aesthetic quality, gating flexibility, and automation.
By understanding this core distinction, you can make informed decisions that optimize both the performance of your mold and the quality of your final product.
