Safety bearings

Magnetic ball bearings are increasingly important in CO2 laser systems and fluid pumps as well as applications in the optics industry.

GMN has led the development and manufacture of safety bearings, so-called ‘touchdown bearings’ since the middle of the 1990s.




Touchdown bearings prevent overloads or failure of magnetic bearings, in which rotating parts could damage the bearing system. Emergency bearings have to carry extreme loads when the shaft crashes and have to adapt to various environmental conditions.


The challenge for safety bearings:

  • Extremely high acceleration from stopped to a nominal RPM (n · dm bis 3,5 · 106 mm/min)
  • Large, bumpy radial and axial forces
  • High number of full runs
  • Small installation space
  • Inadequate lubrication
  • Low system costs
  • Use in aggressive environments


Optimized Engineering

The construction of safety bearings has a significant influence on the dynamic behavior of shafts during emergency runs. 3-bearing systems (a pair of spindle bearings with one grooved bearing) or 4-bearing systems (two pairs of spindle bearings) can be used.


Significant performance criteria are:

  • Arrangement of bearings (rigid, radial and and or axially spring-loaded)
  • Bearing friction
  • The masses which are accelerated
  • Friction between shaft and bearing bore
  • Lubrication
  • Cost-effective and space-saving solution, e.g. 3-bearing system
  • High operating safety due to high load absorption. 4-bearing system

For further data, please refer to our information sheet for touch down bearings.
Request for special bearings

Optimal protection due to no contact

GMN safety bearings are used where other types of bearings reach their limits.

Their advantage:

Support by magnetic forces avoids any contact with materials. Safety bearings have excellent efficacy, and protect expensive components in a magnetic bearing system if there is a disruption of the magnetic field before touching the rotating shaft.


Optimized Engineering


Costs and performance in harmony

Optimized bearing geometry, the use of HNS steels (high-nitrogen steels) and ceramic bearings as well as specific tribology designed for the use case ensure that the user will have a high number of full runs.

A GMN-PVD ball coating allows for the use of steel balls in low-cost systems and provides significant savings potential. On the other hand, ceramic balls can further improve technical performance in high-end applications.


Low-Cost solution

  • Characteristic RPM: 2,2 x 106 mm/min
  • Weight of the rotating parts: < 1,5 kg
  • Atmosphere: Prevacuum
  • Bearing design: Series 618andfull ball
  • Ring material: 100 Cr 6
  • Ball material: 100 Cr 6
  • Lubrication: Ball layer and oil


  • Characteristic RPM: 2,2 x 106 mm/min
  • Weight of the rotating parts: < 3,5 kg
  • Atmosphere: Aggressive gases
  • Bearing design: Series 618 and full ball
  • Ring material: HNS (High Nitrogen Steel)
  • Ball material: Silicon nitride (Si3N4)
  • Lubrication: Oil