Bearings

Question 1

What are the characteristics of ceramic bearings?

Answer 1

~ most typically hybrid systems with Si3N4 balls and steel tracks (racers)

Question 2

What is the result of ceramic (Si3N4) bearings being harder and more rigid than steel?

Answer 2

~ contact area with the bearing racers is significantly reduced

~ up to 80% less friction, less frictional heat generated, 3-10x longer service life

Question 3

Compare Si3N4 and steel bearings

Answer 3

~ Si3N4 has lower density, reducing the dynamic loading at ball-raceway contacts (important for high speed applications)

~ Si3N4 operates better under un-lubricated conditions
~ more corrosion resistantand tolerant of contaminated lubricants

~ retain their hardness to higher temperatures

Question 4

What is done at higher temperatures?

Answer 4

~ a solid lubricant like MoS2 or graphite is used
~ it does not form a complete continuous separating film like liquid lubricants = higher operating temps

Question 5

What is the v-groove plate method?

Answer 5

~ used to form near perfect spheres of Si3N4

~ the upper plate with a spiral v-groove is placed on top of the flat lower plate with balls in between

~ the flat plate rotates while the grooved one is stationary

~ diamond slurry abrades the balls

~ relatively largeballs preferentially grind until all ball sizes match

~ rotation must allow all points on ball surface to have same probability of being abraded

~ diamond grit sizes step from 3.5 to 0.5um

~ plate loading and rotation speed are stepped down with decreasing grit size used