Vaccuum and extreme temperature duty bearings

“Material selection is a key factor in this ready-made system," says HepcoMotion's Chris Rees. "The reason our system works in a vacuum or high temperature environment is down to two things, material selection and some bespoke design.

"Vacuum environments will cause any porous materials to outgas and therefore fail. This effectively rules out the use of any polymers, plastics and some sintered materials. Stainless steel is the default choice for a vacuum because it doesn’t outgas, is inherently clean and non-corrosive and therefore suitable for vacuum applications which require a high level of cleanliness. Stainless steel also doesn't melt in high temperature environments.”

All of the bearings’ moving contact surfaces are made from hardened stainless steel, which is beneficial in a high vacuum environment. The quality of this carefully-selected steel ensures that performance is optimised, and wear-generated debris is eliminated so avoiding the possibility of contamination. Outgassing, is eliminated as all free spaces within the VACSS bearings are connected to a vent hole in the bottom of the retaining screw.

Another advantage of the Hepco system is that a six bearing carriage system, unlike a re-circulating ball rail system, has the ability to traverse a large gap in the rail. This design allows the carriage plate (and component placed upon it) to move from the outside into the vacuum chamber and act effectively as an automated feed-in system. The gap in the rail is essential in order to allow the door of the vacuum chamber airlock to be opened and closed but the Hepco system facilitates this movement with ease.

Grease selection is another key area of the Hepco system and it can, if the application demands it, work ‘dry’. All other bearings can be lubricated internally with grease suitable for their temperature application. The VACSS vacuum and high temperature types use Krytox LVP grease, which is rated from -15°C to +210°C, while the LTSS low temperature bearings are lubricated with AeroShell Grease 22, rated from -50°C to +150°C. The VACSS bearings can also be supplied with alternative grease or without grease if required.

The bearings are available as both concentric and eccentric, which extends the life of the system as when wear/play starts to develop in the system, it can simply be eliminated by adjusting the eccentric. 

The bearings are available in sizes from 18 to 54mm in diameter, with a broad range of fixing styles and load capacities from 180 to 4,200N. They have the same dimensions as the bearings in the HepcoSL2 range and can be supplied ready-mounted onto an SL2 or PRT2 carriage plate, or as components that users can mount onto their own carriage assemblies.