Drag to rotate 3D view; slider simulates compression travel. Schematic representation only; refer to technical drawings and load ratings for actual design.
Structure: Continuous Coiling with Opposing Wave Crests
Crest-to-Crest wave springs are wound from a continuous strand of cold-rolled flat spring steel without welds. Each active turn is phase-shifted by 180° so wave peaks contact opposite peaks.
This continuous one-piece construction prevents turn-to-turn shifting, eliminating the instability, friction, and binding risks associated with stacking individual loose washer components.
Differences Between Single-Turn, Plain Crest-to-Crest, and Shim-End Configurations
Plain Crest-to-Crest springs end with open wave crests that contact the mating seat at point contacts (3 to 6 contact points per end depending on wave count).
Shim-End Crest-to-Crest springs incorporate a continuous flat 360° ring turn on both top and bottom ends. This spreads the axial load into a continuous planar surface, preventing point indentations on softer substrates.
- Plain Ends: Most compact solid height; lowest unit cost; ideal for hardened steel seating surfaces.
- Shim Ends (with Flat Ends): Uniform planar load distribution; eliminates wave point gouging on aluminum or polymer housings; slightly larger solid height (+2 x strip thickness).
Understanding Spring Rate, Deflection Stroke & Turn Count
Because each turn in a Crest-to-Crest spring functions mechanically in series:
1. Total Spring Rate (k_total) = k_single_turn / Number of Active Turns (N). Adding turns softens the spring, producing a gentler force gradient.
2. Total Working Stroke (f_total) = f_single_turn x N. Adding turns linearly expands total available deflection travel.
Installation Alignment and Guidance Tolerances
Crest-to-Crest wave springs require concentric guidance during dynamic stroke to ensure wave crests remain aligned along the central axis.
Guidance can be achieved either by piloting the spring outer diameter inside a bore, or by guiding the inner diameter over a shaft. A diametral clearance of 0.3mm to 0.8mm is recommended to allow the flat wire to expand naturally during compression.
Typical Engineering Applications
Crest-to-Crest wave springs dominate applications requiring moderate to large travel in ultra-compact axial cavities:
- Industrial Control Valves: Actuator springs and live-loaded packing glands.
- Automotive & EV Transmissions: Dual-clutch piston returns and torque damper preloads.
- Robotics & Cobot Actuators: Joint backlash elimination in harmonic drive reducers.
- Aerospace Fluid Regulators: Compact pressure relief and check valve assemblies.
Key Selection & Specifying Guidelines
When creating a drawing callout for Crest-to-Crest wave springs, always specify: Outer Diameter (OD) & Inner Diameter (ID) clearances, Free Height (H0), Working Height (H1) with Required Load (P1), and Maximum Solid Height (Hs).
Crucial Rule: Never compress a Crest-to-Crest wave spring past 85% of its total available travel during routine operation, or fatigue life will drop precipitously.
Frequently Asked Questions
- Why don't the wave crests slip off each other during high-frequency cycling?
- Because the spring is coiled from a continuous, monolithic wire strand. The torsional and bending continuity of the flat wire maintains the 180° phase lock between turns, preventing radial slippage.
- How do I calculate the solid height of a Crest-to-Crest spring?
- For plain ends: Solid Height (Hs) = Number of Turns (N) x Strip Thickness (t). For shim-ends: Hs = (N + 2) x t.
- Can Crest-to-Crest springs be manufactured from superalloys like Inconel 718?
- Yes. TOSTA routinely produces Crest-to-Crest springs from 17-7PH stainless steel, Inconel X-750, Inconel 718, and A286 for high-temperature and subsea applications.
- What is the maximum number of turns achievable on a Crest-to-Crest spring?
- Standard CNC coiling machines handle up to 20 to 30 turns for specialized long-travel applications, though most industrial applications use between 2 and 12 turns.
- How does dynamic response compare to helical coil springs?
- Due to lower active mass and absence of lateral surging, Crest-to-Crest wave springs exhibit higher natural frequencies and superior resistance to high-speed resonance.
Related Engineering Guides
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