What Is Backlash in Gears? And why every maker should know this

Hi makers! How are you doing? Hope you are doing great. In this post, we learn one of the most important yet underrated characteristics of gears — “Backlash.”
Backlash is a tiny gap between meshing gear teeth. It is very small, but it makes a big difference in gearboxes.
If you have ever observed gearboxes, there is a small play in the output shaft of the gearbox. It may be small, but it is still there. It’s common in spur or planetary gearboxes. In the case of worm gearboxes or cycloidal gearboxes, backlash may not be present. This play occurs because of the backlash in the gears of that gearbox. Now you may think backlash is not good as it introduces play in the gearbox output shaft. But no! In most cases, it is intentional.

Why backlash is Important?

When gears transmit motion, if there is no gap between gear teeth, it may cause some issues. Such as jamming, broken teeth, overheating due to excessive friction, etc.
There is another reason: when gears rotate at high speed, friction produces heat, and due to that heat, gear teeth become subject to thermal expansion. This expansion can cause gearbox jamming. That’s why introducing backlash is very important in gears for smoother operation.

Impact of Backlash

If the backlash is introduced correctly in gears, it causes a smoother gearing experience.

Too much backlash causes:

• Vibration
• Inaccuracy (very bad for robotics and CNC applications)
• Poor repeatability

Too little backlash causes:

• Overheating
• Jamming
• broken gear-teeth
• gearbox failure

so, backlash is not your enemy. If utilise correctly it’s makes your Gearing system smoother. Just like life!

Quick tips

1. Preloaded gears — to cancel out unwanted shaft play due to backlash, you can use split gears or springs that preload the gears to reduce the play.
2. Lubrication matters — always use grease between gear teeth to reduce friction and noise, and to provide a smoother experience.
3. Check Shaft play– From my personal experience I can say its not always Backlash responsible for bear box jamming. Some time loose shaft or loose bearing cause misalignments that causes difficulties. So, check twice before power the motor.