Ejector Pins for Injection Molding: Types, Materials, and Selection Guide
Ejector pins are one of the most critical components in an injection mold. They push the finished part out of the mold cavity after the cooling cycle. Choosing the wrong ejector pin — or the wrong material — leads to part damage, pin breakage, and costly downtime.
Types of Ejector Pins
Standard Ejector Pins: The most common type. Made from H13 or equivalent tool steel, through-hardened. Used for general-purpose ejection in most molding applications.
Shoulder Ejector Pins: Feature a larger shoulder diameter that acts as a positive stop. Used when precise pin projection length is critical.
Blade Ejectors: Flat, rectangular cross-section for ejecting thin-walled parts or ribs where round pins won't fit.
Sleeve Ejectors: Hollow pins that eject around a core pin. Used for parts with bosses, standoffs, or through-holes.
Material Selection
H13 Tool Steel: Standard choice. Good toughness and wear resistance. Suitable for most general-purpose molding. Through-hardened to 48-52 HRC.
Stainless Steel (420 SS): For medical, food-grade, or corrosive environments. Lower hardness (40-45 HRC) but excellent corrosion resistance.
M2 High-Speed Steel: Higher wear resistance for abrasive materials (glass-filled nylon, etc.). Hardness 58-60 HRC.
Nitrided Pins: Surface-hardened for extended wear life. Core remains tough while surface reaches 65+ HRC.
Selection Checklist
- Part geometry — where can pins contact without marking?
- Ejection force — how much force is required to release the part?
- Material being molded — glass-filled or abrasive materials need harder pins
- Cycle time — longer runs require more wear-resistant pins
- Operating temperature — high-temp materials need H13 or better