Bearings for Medical Applications and Devices

Medical devices or medical robots that have moving parts will need some type of bearing or bushing to facilitate motion. The types of bearings and applications are many and varied. Once the type of bearing is selected then other issues concerning the operating environment must be addressed.

In some applications the bearings need to operate where human body fluids are present. In some cases they must operate while submerged in blood.

Materials

Human body fluids and especially blood are very caustic to steel bearings. Most steel bearings are manufactured from AISI 52100 chrome or 440C stainless steel. These standard materials are not always suitable for certain medical applications. 

Quick Material Comparison

Pacific International Bearing Sales offers a complete line of Hybrid and Ceramic bearings suitable for use in most medical applications.

As an alternative to AISI52100 chrome bearing steel, PIB offers Cronoduir X30CXrMoN15-1 bearing material as standard in a number of bearing sizes. Cronoduir is an excellent material to use in combination with ceramic balls creating a hybrid bearing capable of higher performance for speed and loads as compared to standard bearings. 

The use of Cronouduir in medical applications provides an ideal solution for bearings coming in contact with biofluids. I cannot emphasize enough to the designer  how use of this material is a major advancement for use in medical devices especially where they operate in a corrosive environment. Now that being said of course there are many components used in all types of medical robots and other medical devices where AISI 52100 chrome or 440C stainless bearing steel can be used with no problem.

Biocompatibility & Regulatory Notes

• If any bearing component can contact the patient or fluid path, assess biocompatibility (cytotoxicity, sensitization, irritation) on the finished device.
• Keep material traceability (heat treatment certs, lot numbers) and document supplier changes.
• Record sterilization compatibility test results alongside measured starting torque and acoustic/noise before/after cycles.

As in most applications the Design Engineer should specify the shields or seal types needed. Often in the selection of enclosures starting and running torque must be considered. If the environment cannot allow for grease or oil seepage from then full contact seals can be specified. TPI offers a Full Contact rubber seal for standard series radial ball bearings which is waterproof and is perfect for use on bearings used in medical applications. The LLU seal keeps lubrication inside the bearing and prevents the ingress of dirt and contaminants while being impervious to water spray. The LLB black seal is a non-contact seal and can be specified for standard service and is a good choice where starting and running torque is a consideration.

Bearing types for medical applications

Pacific International Bearing supplies numerous medical bearing applications with miniature bearings, normal duty radial ball bearings, angular contact bearings, plain spherical bearings, rod ends, needle bearings, double row ball bearings, and tapered roller bearings.

Any bearing or bushing can be applied successfully in many medical applications. Pacific International Bearing Company works with many medical companies and can offer insights for your medical bearing application specific requirements.

Medical Device companies such as Medtronic, Intuitive Surgical, Johnson and Johnson, and Stryker are among the companies successful in manufacturing robot assisted surgery medical robot devices.. Robot assisted surgery devices require precision bearings. Striker’s Mako Robotic arm assisted surgery system shown here is a good example of a medical robot using multiple axis bearings.

FAQ 

Q: What bearing materials work best in contact with blood or saline?

• X30CrMoN15-1 (Cronidur® 30) or high-grade 440C stainless rings resist pitting/crevice corrosion better than AISI 52100.
• For motorized joints and current paths, use hybrid bearings (Si₃N₄ ceramic balls + stainless rings) to add electrical insulation and reduce wear.
  

Q: Can thin, sealed bearings survive steam autoclave (121–134 °C)?

• Yes. Specify stainless/X30CrMoN15-1 rings, FKM full-contact seals (LLU), and PFPE grease; verify starting torque and noise drift after 100–200 cycles.
  

Q: What seals should I choose for medical devices — LLU vs LLB vs LLH?

• LLU (full-contact): best fluid exclusion/grease retention; highest torque.
• LLH (light contact): balance of protection and torque.
• LLB (non-contact): lowest torque; only in clean, secondary-sealed housings.
  

Q: Which lubricants are compatible with repeated sterilization?

• PFPE-based oils/greases (PTFE thickener) are chemically inert and compatible with steam and VHP.
• Typical fill for sealed bearings: 20–35 % of free volume. Run-in at 30–60 % operating speed for 10–20 min.
  

Q: Are bearings compatible with VHP (vaporized H₂O₂) or EtO?

• VHP: use FKM or FEP-encapsulated seal lips; confirm cage polymer (PEEK/PPSU) compatibility.
• EtO: broadly compatible; allow aeration time; watch for additive extraction in non-PFPE greases.
  

Q: What about gamma/e-beam radiation sterilization?

• Use radiation-stable cage and seal materials; PFPE oils generally tolerate dose better than hydrocarbon greases. Validate torque after the qualified dose.
  

Q: When should I specify hybrid bearings (Si₃N₄ balls)?

• In motorized axes (to block inverter-induced shaft currents/EDM), for higher speed, or where non-magnetic rolling elements are helpful. Rings still define corrosion limits.

Q:  Which precision class should I pick for surgical robots or imaging tables?

• Start with ISO P5 (≈ ABEC 5); upgrade to ISO P4 (≈ ABEC 7) for very low runout/noise. Precision helps only if mounting fits/flatness are controlled.

If your company requires medical bearings or medical robotic bearings, please contact Pacific International Bearing Sales. You can send your questions or inquiries to [email protected] , and their team will be happy to assist you. Visit us at www.pibsales.com