Achieving the Best Wear Life and Performance

GRW High Precision Bearings engineers recently revealed results from its extensive bearing lubrication testing promising longer life of dental and medical equipment through the optimized use of lubricants. Through its goal of continuous improvement, GRW takes its outstanding performing, corrosion resistant bearings to the next level with this lubricant research.

Miniature ball bearings, used in dental instruments and medical devices, depend on lubrication for optimal performance and reliability. Using extensive laboratory testing of 30 lubricants from different manufacturers, GRW identified five autoclave resistant lubricants most suitable for use in medical applications. These lubricants are already used extensively, in GRW products, for the ever-increasing demands of the dental and medical markets.

According to Robert-Koch Institute guidelines, sterilization (autoclaving) is mandatory for the proper use of medical instruments. The sterilization processes used in these instruments and other medical devices pose a particular challenge to lubricants used in miniature ball bearings. In particular, dental hand pieces must be autoclaved with superheated steam, and no re-lubrication can occur due to contamination risks.

In GRW’s laboratory testing of 30 lubricants, each was subjected to 1,000 sterilization cycles with superheated steam. Initial testing eliminated 11 of the lubricants due to changes that limit functional behavior, such as water retention in the grease samples and thermal expansion during autoclaving.

The remaining 19 lubricants were subjected to analytical and visual testing criteria including weight and optical changes, scanning electron micrographic inspections and infrared spectra. Five of these lubricants were found to be particularly capable of withstanding repeated sterilization. Finally, GRW concluded that the best performing lubricants for medical and dental hand pieces were those consisting of polyurea-thickened greases using a base of mineral oil or PAO (polyalphaolefin).

GRW Dental Test Stand Further Validates Lubricant Performance
High-speed uses, such as in dental turbines running at 500,000rpm, were also factored into the test criteria. Along with the lubricants, the ball bearings were subjected to noise testing (GPR) and starting torque behavior tests using GRW’s in-house dental test stand developed specifically for these applications. The study proved that any increase in starting torque, caused by viscosity changes in the lubricant, resulted in considerable heat generation within each bearing. Infrared spectroscopy and SEM-analysis were the primary test criteria for determining any significant changes or alterations to the grease samples. Visual condition and the loss of mass were shown to be less significant.

Raising the Bar for Bearing Performance
Taking into account all known criteria, GRW’s testing revealed that the best overall results were achieved using greases with a base of mineral oil or PAO. Notably, Greases thickened with special lithium or sodium soap additives are unsuitable for autoclaving. Superheated steam readily permeates these altered greases and has a negative effect on its adhesive properties, thereby limiting adhesion to the functional surfaces of the ball bearing.

GRW’s attention to lubrication testing demonstrates its innovation and market commitment in delivering the best possible solutions for the medical and dental industries. Manufacturers choosing GRW high precision custom bearings for surgical instrument and dental turbines not only receive the proven reduced noise and starting torque benefits, but now can enjoy the economic advantage of prolonged life.