Impact duty punishes springs. Disc springs for machine tools cope because they are largely self damping, deliver high loads from a short stack, and have a long, predictable service life under dynamic load. SCHNORR components are used in stamping machines, spindles, percussion drilling machines and sliding hubs in conveyor drives, where the load arrives suddenly and repeats all day.
A press does not apply load. It hits things. So does a percussion drill, a punch, and any hub that slips to protect a driveline. That changes what you look for in a spring.
Self damping is the property that matters most
Coil springs under repeated impact can surge, where the coils resonate and the spring destroys itself well inside its calculated fatigue life. Disc springs are largely self damping, because friction between the discs and at the abutments absorbs energy inside the stack. Parallel stacking increases that internal friction, which is one reason parallel and combined arrangements turn up so often in press tooling.
Stamping tools: load in the space the die leaves you
In stamping tool springs the space is not negotiable. The die set defines it and the spring fits inside what is left. Disc springs make efficient use of space while providing high spring loads, and stacking sets the character: parallel for force at the same deflection, series for travel at the same force, combined arrangements for a progressive curve where the resistance climbs as the tool closes.
Spindles: preload that stays where you set it
Spindle preload is a precision problem rather than a force problem. The requirement is a known, stable axial load that does not drift with temperature or time. Presetting means there is no setting under static loads, so the installed height holds. Load tolerance also matters here more than anywhere else, and disc spring tolerances are defined for overall height, thickness, load and diameter.
Sliding hubs and torque limiters
A sliding hub in a conveyor drive uses spring force to set the point at which the drive slips instead of breaking. That makes the stack a torque limiter disc spring design: the slip torque follows the axial clamping force, so a repeatable spring load is the whole mechanism. Parallel stacks give the force, and the load deflection curve decides how sharply the slip point holds as the friction faces wear.
Guidance decides whether you get the life you calculated
Impact duty is unforgiving about geometry. Specify it explicitly:
- A guide element is needed to prevent lateral movement.
- Inside guidance on a bolt or shaft is preferred, though outside guidance is acceptable.
- Guides and abutments should be hardened to a minimum of 60 HRC with a minimum case depth of 0.8 mm where possible.
- The guide surface should be smooth and, if possible, ground.
- Unhardened guides are acceptable for static applications only.
And check the fasteners on the machine itself
Press frames, drill housings and conveyor drive mounts are the classic locations for joints that come loose. Serrated safety washers hold those joints through friction and mechanical locking, maintained pretension force after 2,000 cycles in Junker testing, and can be reused two or more times when the machine is stripped for service.
- SCHNORR components are used in stamping machines, spindles, percussion drilling machines and sliding hubs in conveyor drives.
- Disc springs are largely self damping, which suits repeated impact duty.
- Parallel stacking makes forces additive at the same deflection. Series stacking makes deflections additive at the same force.
- Presetting means no setting under static loads, which keeps spindle preload stable.
- Tolerances are defined for overall height, thickness, load and diameter.
- Guides and abutments should be hardened to a minimum of 60 HRC with a minimum case depth of 0.8 mm, with a smooth, ideally ground surface.
- In Junker testing, SCHNORR safety washers maintained pretension force after 2,000 cycles.
Frequently asked questions
Why do disc springs suit impact and press applications?
They are largely self damping, so energy is absorbed within the stack instead of exciting resonance, and they provide high spring loads from a short installation length with a long, predictable life under dynamic load.
How are disc springs used for spindle preload?
They provide a known axial load in a short length. Because presetting means there is no setting under static loads, the preload stays where it was set, and load tolerances are defined by the standard.
Can a disc spring stack be used as a torque limiter?
Yes. In a sliding hub the slip torque follows the axial clamping force, so a repeatable spring load sets the slip point. Parallel stacks are used to reach the required force.
What guidance does a disc spring stack need in a press?
A guide element to prevent lateral movement, preferably inside guidance on a bolt or shaft, with guides and abutments hardened to at least 60 HRC, a minimum case depth of 0.8 mm and a smooth, ideally ground surface.
How do you keep machine frame bolts tight under impact?
Use serrated safety washers, which lock through friction and mechanical locking. In Junker testing they maintained pretension force after 2,000 cycles and they can be reused two or more times.