09-11-2012, 05:04 PM
Sliding Contact Bearings
13_Slidingcontactbearings.pdf (Size: 689.76 KB / Downloads: 280)
Outline
• General Characteristics of Sliding Contact
Bearings
• Typical Materials of Sliding Contact
Bearing
• Gib Design
• Configurations for Sliding Contact Rotary
Bearings
• Configurations for Sliding Contact Linear
Bearings
Straight Talk on Ways
• Three basic types of ways exist: plain sliding
(sliding contact bearing), rolling element
and hydrostatic ways.
• In this design, the moving surfaces slide
against each other assisted by a layer of
lubrication which, when operating correctly,
actually produces a hydro-dynamic bearing.
• That is a bearing which guides on a
controlled layer of lubrication created by
motion.
Advantages of Sliding Contact Bearing
• Have a good resistance to wear, fatigue and corrosion
• Have sufficient strength to support the load
• Have a fairly high melting point to reduce the tendency for
creep in use
• Have suitable thermal properties to enable heat to be
conducted away
• As metal to metal contact will be unavoidable in service the
material should be selected to minimize seizure, fretting
(corrosion), scoring and welding
• The bearing should be tolerant to dirt and foreign mattere.
g. soft surface
• Should be tolerant to misalignment
• Should be compatible to lubricant used- e.g should not
corrode if water is used
Dynamic Stiffness
• Many consider plain guides superior because of their high
dynamic stiffness.
• In simple terms, dynamic stiffness equals static stiffness
times damping.
• Plain slides, due to their long surface areas and oil film
lubrication, develop much higher damping than rolling
element bearings, which have very little surface area.
• Rolling element bearings do possess a high static stiffness.
Taking a high static stiffness times a low damping factor
results in low dynamic stiffness.
• Plain slides, on the other hand, have a high static stiffness
and a higher damping, thus resulting in a much higher
dynamic stiffness.
• Plain slide ways experience speed limitations due to their
hydrodynamic nature.