Zero backlash refers to the state of a mechanical system in which there is no play between coupled components. In the case of screw drives, this means that there is no axial play between the screw and the nut, and changes in the direction of movement are transmitted without delay.
Zero backlash is crucial for:
- High positioning and repeatability accuracy
- Direct power transmission without dead travel
- Stable control in servo drives
- Prevention of jerking and vibrations
Achieving Zero Backlash
Backlash-free designs are usually realized through preloading, e.g.:
- Preloaded ball screw nuts
- Double nut systems
- Adjustable nuts (e.g., KMT or split nuts)
- Spring or spacer ring solutions
Advantages & Disadvantages
Advantages
- Highly precise movements
- High rigidity
- Good repeatability
Disadvantages
- Higher frictional torque
- Increased wear
- Greater drive requirements
Distinction
Axial play: present: not backlash-free
Zero backlash: play reduced to zero or eliminated by design