Heat-Resistant Coil Springs
Round wire and flat wire coil springs for injection mold ejection and stripper plate return. Available in six load grades (SWF through SWY) with deflection ratings from 30% to 65%, all rated for continuous operation at 200°C. SiCr alloy wire (SWOSC-V) and hardened alloy steel options.
Heat-Resistant Coil Springs — 10+ Products
Heat Resistant Round Wire Spring — 60% Deflection (WFH Series)
Extra-light load round wire coil spring with 60% maximum deflection. 200°C rated SiCr alloy wire.
WLH Series Round Wire Spring — 50% Deflection
Light load round wire coil spring with 50% maximum deflection. Continuous service up to 200°C.
WHH Series Round Wire Spring — 35% Deflection
Heavy load round wire coil spring with 35% maximum deflection. 200°C rated for demanding ejection.
WMH Series Round Wire Spring — 40% Deflection
Medium load round wire coil spring with 40% maximum deflection. Reliable force at 200°C.
SWU Series Flat Wire Spring — 60% Deflection
Super-high deflection flat wire coil spring. 20-30% higher force per unit depth than round wire equivalents.
SWY Series Flat Wire Spring — 65% Deflection
Ultra-high deflection flat wire coil spring for extreme force requirements. Maximum available deflection.
SWR Series Flat Wire Spring — 50% Deflection
High deflection flat wire coil spring with 200°C heat resistance. Ideal for space-constrained applications.
SWS Series Medium Deflection Flat Wire — 40%
Medium deflection flat wire coil spring for stable force in demanding setups. Heat resistant to 200°C.
SWN Series Low Deflection Flat Wire — 30%
Low deflection flat wire coil spring for stable force in machinery. Heavy load, minimal compression.
PCS Coil Springs — Heavy Pressure (Inch)
Hardened alloy steel with E-coat corrosion resistance. Gold/Silver color coding. Inch dimensions.
PCS Coil Springs — Medium Pressure (Inch)
Blue/Silver color-coded medium pressure springs. Hardened alloy steel with E-coat protection.
PCS Coil Springs — Med-Heavy Pressure (Inch)
Hardened alloy steel with E-coat corrosion protection. Rated up to 482°F (250°C).
PCS Coil Springs — Extra-Heavy Pressure (Inch)
Green/Silver color-coded extra-heavy pressure springs. Maximum force in inch standard sizes.
Round Wire vs Flat Wire Coil Springs
Coil springs for injection molds come in two fundamental wire cross-sections, each with distinct advantages:
| Dimension | Round Wire (SW-series) | Flat Wire (SWU/SWR/SWS/SWN/SWY) |
|---|---|---|
| Wire Cross-Section | Circular (standard DIN 17223 / JIS G3561) | Rectangular (cold-rolled from round stock) |
| Force per Pocket Depth | Baseline (1.0x) | 1.2-1.3x (rectangular coils nest tighter) |
| Lateral Stability | Good — may buckle if L/D ratio > 4:1 | Excellent — rectangular section resists buckling |
| Cost | Lower (standard wire stock) | 15-25% premium (cold-rolling process) |
| Availability | Standard catalog, same-day shipping | Standard catalog, 1-3 day shipping |
| Best For | Standard ejector/stripper return with adequate pocket depth | Space-constrained applications, high-force in shallow pockets |
How to Select the Right Deflection Grade
Deflection percentage is the maximum safe compression ratio of a spring. A 40% deflection spring with a 50mm free length can be compressed to 30mm (50 × 0.40 = 20mm compression) without permanent deformation.
- 30% (SWN/SWH): Highest load capacity per coil. Use when you have generous pocket depth but need maximum force. Longest fatigue life.
- 40% (SWM/SWS): Best balance of force and stroke. Standard choice for 80% of mold applications.
- 50% (SWL/SWR): Greater stroke in a shorter free length. Use when pocket depth is limited but moderate force is acceptable.
- 60-65% (SWF/SWU/SWY): Maximum stroke from minimum pocket depth. Lower cycle life — use only when space constraints demand it.
Key formula: Spring force at working height = Spring rate (k) × Compression distance. Always verify that the force at maximum deflection does not exceed the spring's rated load.
Application Scenarios
Ejector Plate Return
Pain point: Ejector plate does not return fully or consistently, causing short shots or part damage on the next cycle.
Why it fits: SWM (Red/Medium) round wire springs at 40% deflection provide consistent return force over millions of cycles. The 200°C heat resistance prevents force degradation in heated molds.
Recommended: WMH Series (SWM) Round Wire, 40% Deflection
Stripper Plate Separation
Pain point: Stripper plate requires high initial force to break part adhesion, but limited pocket depth restricts spring size.
Why it fits: SWU flat wire springs deliver 20-30% more force per unit depth than round wire. The 60% deflection rating allows maximum stroke from shallow pockets.
Recommended: SWU Series Flat Wire, 60% Deflection
High-Temperature Resin Molds
Pain point: Springs in PPS/PEEK molds (180-200°C base temperature) lose load capacity rapidly, requiring frequent replacement.
Why it fits: SWOSC-V SiCr alloy wire maintains 95%+ load capacity at 200°C over 1M+ cycles. No load loss compared to standard carbon steel springs that fail at 120°C.
Recommended: WHH Series (SWH) Heavy Load, 200°C Rated
Specification Quick Reference
Standard coil spring dimensions available across all load grades:
| Outer Diameter (mm) | Available Free Lengths (mm) | Wire Types | Load Grades |
|---|---|---|---|
| 5 - 8 | 10, 15, 20, 25, 30 | Round | SWF, SWL, SWM, SWH |
| 10 - 16 | 15, 20, 25, 30, 40, 50 | Round, Flat | All (SWF-SWY) |
| 18 - 25 | 20, 25, 30, 40, 50, 60, 80 | Round, Flat | All (SWF-SWY) |
| 27 - 35 | 25, 30, 40, 50, 60, 80, 100 | Round, Flat | SWM, SWH, SWU, SWY |
| 40 - 50 | 30, 40, 50, 60, 80, 100, 125 | Flat | SWU, SWY |
Materials: SiCr alloy wire (SWOSC-V, JIS G3561) for round wire. Cold-rolled alloy steel for flat wire. Hardened alloy steel with E-coat for PCS inch series. Custom lengths and OD available on request (MOQ: 50 pcs).
Engineering Resources
Frequently Asked Questions
What is the difference between SWM and SWH load grades?+
How many cycles can I expect from a heat-resistant coil spring?+
Can I use these springs in press die applications?+
Do you offer custom spring rates?+
Need a Custom Quote?
Send your specifications and receive a quote. MOQ: 1 piece. Custom dimensions available.