HepcoMotion is launching VACSS and LTSS linear and rotary guides that have been developed specifically for applications involving extreme temperatures or vacuum. Because these all-stainless-steel vee bearing products are available as standard, off-the-shelf components, they can save considerable time and cost, as well as reducing project risk for specialist machine builders.
Previously engineers wishing to move products within a vacuum or extreme temperature environment were faced with two choices: design their own linear motion concept and, therefore, use an unproven system that carried with it risks relating to timescales and budgets; or adapt from the narrow choice of systems available, with no guarantee that the materials used would meet the application requirements.
A vital feature of the new Hepco system is the use of stainless steel throughout. Chris Rees, the Sales Director at Hepco, comments: "Material selection is a key factor in this ready-made system. 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 does not outgas, is inherently clean and non-corrosive, and is therefore suitable for vacuum applications which require a high level of cleanliness. Stainless steel also does not melt in high-temperature environments."
Guideway component design for extreme 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 to avoid the possibility of contamination. Outgassing is eliminated by virtue of the materials used, and all free spaces within the VACSS bearings are connected to a vent hole in the bottom of the retaining screw. Note that the same design principles are also being applied to complementary products such as Hepco track roller bearings for applications in the same demanding operating environments.
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 enables 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; if the application demands it, the system can even operated '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 to +210degC, while the LTSS low-temperature bearings are lubricated with AeroShell Grease 22, rated from -50 to +150degC. The VACSS bearings can also be supplied with alternative grease or without grease if required.
Vacuum and extreme-temperature bearing options
Hepco's vacuum and extreme-temperature bearings are simple and cost-effective to integrate, and deliver consistently excellent results throughout a long operating life. The bearings are available as both concentric and eccentric types, the latter of which extends the life of the system because wear/play can be removed by adjusting the eccentric bearings.
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 4200N. 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, alternatively, as components that users can mount onto their own carriage assemblies. A further option is to use the bearings to support a circular ring that forms the basis for a turntable.
These products are widely used in applications such as: semiconductor wafer and aerospace component manufacture; vapour deposition processes; manufacture of LCD panels and plasma displays; and in vacuum evaporation equipment. The LTSS (low-temperature, stainless steel) bearings also appear in low-temperature applications such as cold stores and specialised freeze dry equipment.
Chris Rees concludes: "Because of the lack of suitable solutions currently available, users are forced to design their own bearing solutions for vacuum and extreme temperature applications, often at high cost. By contrast, this range of bearings will give customers a quality solution that they can simply fit, with the confidence of achieving high performance."