Recirculating ball screw
A recirculating ball screw consists a screw, a nut and a series of balls.
The main difference between a recirculating ball screw and a power screw is that in former the sliding friction gets replaced by rolling friction.
Since rolling friction is very less than sliding friction recirculating ball screw has very high efficiency of power transfer.
The threads of screw and nut in recirculating ball screw are semicircular so that they can accommodate rolling balls.
Recirculating ball screw is also known as ball bearing screw or simply ball screw.
There is almost no heat generation in recirculating ball screw due to negligible friction and they can be used at very high speeds up to 10 m/min.
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Advantages of recirculating ball screw
Compared to power screw they offer following advantages.
- They have very high efficiency (approx. 90%), compared to power screw (approx. 40%)
- No stick and slip phenomenon which results in durability
- It is virtually wear free
- They require Less starting torque
- No heat generation during operation
- They can be used for high speed operations
- They can be easily preloaded to eliminate backlash
- They have very smooth and noiseless operation
- They have high reliability and durability
- Their load carrying capacity is more than power screw of the same size
Disadvantages of recirculating ball screw
Compared to power screw they offer following disadvantages.
- They are much more costly
- Buckling of screw is serious problem at critical speed
- They require high degree of cleanliness
- They require thin film lubrication for satisfactory operation
- They can have vibrations
- They require periodic overhauling to maintain their efficiency
- They do not have self-locking properties
Applications of recirculating ball screw
- Machine tools controls
- Used in robotics where precise movement is vital
- Hospital beds adjusters
- Aircraft landing gear retractors
- X-Y recorders of CNC machines
- Power actuators
- Automobile steering gears