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AXIOMMOLDS

Gas Release Straight Ejector Pins

Built-in venting channels allow trapped air to escape during injection, preventing burn marks and diesel marks in deep cavities and blind ribs. Also known as vented ejector pins. 14 product series in M2 and H13 steels.

Products (14 Series)

Gas Release — M2 Steel, Single Groove
Gas Release — M2 Steel, Single Groove

Single longitudinal vent groove for standard venting.

Gas Release — M2 Steel, Multi-Groove
Gas Release — M2 Steel, Multi-Groove

Multiple grooves for enhanced venting capacity.

Gas Release — H13 Nitrided
Gas Release — H13 Nitrided

For high-temperature resins (PA+GF, PPS, PEEK).

Gas Release — Flat Type
Gas Release — Flat Type

Flat ground along shaft for maximum vent area.

About Gas Release Ejector Pins

Venting Mechanism: As the resin front advances through the cavity, air ahead of it must escape or it compresses, heats (adiabatic compression can exceed 400°C), and ignites the resin — creating diesel/burn marks. Gas release pins provide an escape path through grooves along the pin shaft, routing trapped gas from the cavity face through the ejector plate to atmosphere.

Groove Design Parameters: Groove depth is critical: too shallow (below 0.015mm) and venting is insufficient; too deep (above 0.06mm) and resin flashes into the groove. The sweet spot is 0.02-0.04mm depth for most unfilled resins. Glass-filled resins can tolerate 0.03-0.05mm due to higher viscosity.

Placement Strategy: Position gas release pins at the last-to-fill locations in the cavity — these are where air collects. Common locations: blind rib ends, boss bottoms, weld line areas, and gate-opposite surfaces. Complement with standard venting at the parting line.

Application Scenarios

Deep-Rib Structural Parts

Automotive structural parts with reinforcement ribs 15-30mm deep where parting-line vents cannot reach rib bottoms.

Why gas release fits: Pins placed at rib bottoms vent trapped air directly. No need for complex side venting or vacuum-assisted molding.

Recommended: Multi-groove, H13 nitrided for glass-filled PA

Boss Features in Consumer Electronics

Mounting bosses in phone cases and laptop shells where burn marks at boss bottoms cause customer rejection.

Why gas release fits: Single-groove pins at boss bottoms eliminate trapped air without adding venting complexity to the mold design.

Recommended: Single-groove, M2 steel, ø1.5-3.0mm

Frequently Asked Questions

How does a gas release ejector pin vent trapped air?+
Gas release ejector pins feature precision-machined flat cuts or grooves along the pin shaft that create a controlled air channel between the pin and the bore wall. During injection, trapped air between the advancing resin front and the pin tip escapes through this channel to the vented side of the ejector plate. The venting gap is typically 0.01–0.03mm — small enough to prevent resin flash but large enough for gas evacuation. Two main designs exist: (1) flat-cut (single or dual flats along the shaft) and (2) collar-type with circumferential grooves. The flat-cut design provides 2–5× the venting area of standard pin-bore clearance.
What venting capacity (area) do gas release ejector pins provide?+
Venting area depends on the design: flat-cut pins typically provide 0.5–2.0 mm² of venting cross-section per pin (compared to 0.01–0.05 mm² for standard bore clearance). Collar-type gas vent pins offer 1.0–3.0 mm² through circumferential grooves. For reference, a ø5mm flat-cut gas release pin provides approximately 1.2 mm² of venting area — equivalent to adding 20+ standard pins worth of venting capacity. The required venting area depends on shot volume and resin viscosity; as a rule of thumb, use 1 mm² of venting per 50 cm³ of cavity volume for standard resins, or 1.5 mm² per 50 cm³ for low-viscosity resins prone to gas trapping.
Can gas release pins be used in high-temperature resins?+
Yes — gas release pins are available in H13 nitrided (SKD61, HV 900+ surface) specifically for high-temperature engineering resins like PA66+GF, PPS, PEEK, and LCP that process above 280°C. The nitrided surface resists thermal fatigue and abrasion from glass-fiber-filled compounds. For extreme temperatures (above 350°C), PROVA400 or TAVAX ESR materials offer superior hot hardness retention. Note: high-temperature resins generate more decomposition gases, making gas release pins especially critical — without adequate venting, burn marks (dieseling) are almost guaranteed in deep-cavity or multi-gate molds.

Engineering Resources

Technical Guide

Gas Venting Calculation for Deep-Rib Molds

Vent area sizing, groove depth selection, and placement strategy.

Troubleshooting

Burn Mark Prevention: Gas Release Pin Selection

Root cause analysis and pin selection by resin type.

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✓ 14 series✓ M2 + H13 nitrided✓ MOQ 1 piece