Why Stack Disc Springs?
An individual coned disc spring exhibits immense load-carrying capacity but inherently modest deflection travel (typically 0.2 mm to 3.0 mm). By combining individual discs into multi-disc spring columns (stacks), mechanical engineers can adjust total stroke, total load, and curve linearity independently to suit exact operating requirements.
DIN 2093 and DIN EN 16984 define strict mathematical guidelines for stacking disc springs in series (opposing coned orientations), parallel (nested identical orientations), and mixed combinations, enabling high-performance actuation in heavy clamping, valve seating, and pipeline shock absorption.
4 Primary Stacking Configurations
1. Series Stacking (Opposing Orientation: ><><)
Discs are stacked with alternating cone directions contacting along their outer and inner edges. Total deflection equals the single disc deflection multiplied by the number of discs (s_total = i × s), while load capacity remains identical to a single disc (F_total = F).
Free Stack Height: L₀ = i · h₀ + i · t | Application: Long-stroke thermal compensation, pipe supports, valves.
2. Parallel Stacking (Nested Orientation: >>>>)
Discs are nested in identical cone orientations nesting inside one another. Total load capacity equals single disc load multiplied by the disc count (F_total = n × F), while deflection remains equal to a single disc (s_total = s).
Free Stack Height: L₀ = h₀ + n · t | Application: Ultra-heavy bolted joint preloading, heavy press dies.
3. Mixed Stacking (Series-Parallel Combination: >><<>><<)
Consists of multiple parallel packs (each containing n nested discs) stacked in series across i groups. Combines the benefits of high load capacity and extended stroke: F_total = n × F and s_total = i × s.
Application: Machine tool power drawbars, oilfield downhole jars, subsea drilling equipment.
4. Progressive Stacking (Stepped Thickness or Asymmetric Packets)
Assembled using discs of varying thicknesses, or varying packet quantities (e.g., single discs in series with double-disc parallel packs). As axial compression proceeds, the softer single discs deflect fully first, after which the stiffer parallel packs engage, yielding a rising progressive stiffness curve.
Application: Vehicle suspension bump-stops, progressive brake actuators.
Interlayer Friction & Hysteresis per DIN 2093
When disc springs are nested in parallel, sliding contact between adjacent conical faces generates Coulomb friction. During compression, this friction resists displacement, raising the effective loading force; during release, friction delays rebound, reducing the unloading force.
DIN 2093 Friction Correction Factors:
Loading Force: F_loading = n · F · (1 + w · (n - 1))
Unloading Force: F_unloading = n · F · (1 - w · (n - 1))
Where w is the empirical friction coefficient (typically 0.02 to 0.03 for lubricated discs, 0.05 for unlubricated). For n > 4 discs in parallel, friction hysteresis becomes excessive, so DIN 2093 strongly advises limiting parallel nested discs to a maximum of 3 to 4 discs per pack.
Guide Rod & Housing Clearance Specifications
Because coned disc springs tilt and expand radially under axial load, stacks must be guided either internally by a center mandrel/rod or externally by a cylindrical housing bore:
- Internal Guide Mandrel: Preferred in most machinery. Guide rod clearance: (d_disc - D_rod) should equal 1%–2% of the disc ID.
- External Guide Bore: Preferred in heavy punch tooling. Housing bore clearance: (D_bore - D_disc) should equal 1%–2% of the disc OD.
- Surface Hardening: Guide surfaces must be case-hardened to HRC 55+ and polished (Ra ≤ 0.4 µm) with adequate grease or MoS₂ lubrication to prevent galling.
- Stack Slenderness Ratio: To prevent column buckling, the total free length of an unguided stack should not exceed 3 times the outer diameter: L₀ ≤ 3 · D. For longer stacks, intermediate floating guide washers should be incorporated.
Need Custom Disc Spring Stack Engineering?
Provide your available cavity envelope, target load, and stroke requirements. TOSTA engineers provide verified DIN 2093 calculation reports, assembly diagrams, and prototype stacks.