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Views: 0 Author: Site Editor Publish Time: 2025-01-20 Origin: Site
An O-ring is a circular, elastomeric sealing element commonly used in plastic injection molds to prevent fluid or gas leakage. It is a type of extruded seal, meaning it operates by being compressed between two or more surfaces to form a tight, reliable seal.
The sealing performance and service life of an O-ring are determined primarily by:
Compression Ratio: The amount the O-ring is compressed in its groove.
Elongation: The stretching of the O-ring's cross-section during installation.
Proper control of these two factors ensures:
Adequate sealing contact
Reduced wear and friction
Long service life without permanent deformation
Note: The effectiveness of the O-ring largely depends on the accurate fit between the O-ring and the groove, enabling the correct amount of compression and stretch.
When designing O-ring compression for plastic injection mold applications, keep these in mind:
✅ Ensure sufficient sealing contact
Prevents leaks under pressure or thermal expansion.
⚙️ Minimize friction
Especially in cooling channel connections where high flow rates are present.
Avoid permanent deformation
Over-compression leads to flattening or cracking of the O-ring over time.
Many plastic injection mold companies use red-colored O-rings, which are typically made from silicone or fluorosilicone materials. These are well-suited for:
High-temperature resistance
Chemical resistance
Repeated thermal cycling
Proper O-ring groove design is critical for maintaining seal integrity. Here are some general guidelines:
| Design Factor | Recommendation |
|---|---|
| Groove Width (W) | Slightly wider than O-ring cross-section |
| Groove Depth (D) | Designed to achieve 20–30% compression |
| Stretch (ID Fit) | O-ring inner diameter (ID) should be slightly smaller than shaft or groove it fits into (typical stretch 1–5%) |
| Compression Ratio | 15–30% for dynamic seals; 25–40% for static seals |
| Corner Radii | Use small radii to avoid sharp edges cutting the O-ring |
| Surface Finish | Smooth surface: Ra ≤ 1.6 µm to reduce wear |
| O-Ring ID (mm) | Cross Section (mm) | Recommended Groove Width (mm) | Groove Depth (mm) | Material | Max Temp (°C) |
|---|---|---|---|---|---|
| 10 | 2.5 | 3.0–3.2 | 2.0–2.1 | Silicone (Red) | 200–250 |
| 15 | 3.0 | 3.5–3.7 | 2.4–2.5 | Nitrile (NBR) | 100–120 |
| 20 | 3.5 | 4.2–4.5 | 2.8–3.0 | Viton (FKM) | 250–300 |
Final dimensions should always follow ISO 3601 or customer-specified standards.
