Mold Design Guide

Mold design quality directly determines part quality, cycle time, and production efficiency. This guide covers the essential principles of injection mold design.

Gating Systems

Gate Types

Gate Type	Best For	Application
Edge gate	General purpose	Most part geometries
Pin gate	Three-plate molds	Multiple cavities, automatic degating
Submarine gate	Automatic degating	High-volume, simple geometry
Fan gate	Large, flat parts	Panels, covers
Valve gate	Hot runner systems	Cosmetic parts, sequential filling

Cooling System Design

Cooling typically accounts for 50-70% of cycle time. Effective cooling design is the most impactful way to reduce cycle time:

• Cooling channels should follow part contour (conformal cooling for complex geometries)
• Channel diameter: 8-16 mm typical
• Distance from cavity surface: 1.5-2x channel diameter
• Channel spacing: 3-5x channel diameter
• Turbulent flow (Reynolds number > 4,000) for optimal heat transfer

Ejection System

Ejector pins — most common, simple but may leave witness marks. Sleeve ejectors — for thin-walled parts or bosses. Stripper plates — for large flat parts, distribute ejection force evenly. Air ejection — for deep-drawn containers, no witness marks.

Mold Materials

Material	Hardness (HRC)	Application
P20	28-32	Low-volume production, prototype molds
H13	48-52	Medium-high volume, abrasive materials
S7	54-58	High-impact, high-wear applications
420 SS	48-52	Medical, food-grade, corrosion-resistant
NAK80	37-43	High-polish surfaces, optical parts