Backlash is a term that is often heard in the automation world. However, many are not aware that the definition of this word can change depending on the manufacturer of a product.
In today’s post, we will go over the general concept of backlash, as well as the definition of backlash that Nabtesco uses to explain some of the characteristics of our gearboxes.
Standard Backlash Definition
Backlash is typically defined in a set of meshed gears as the amount of free travel (sometimes called lost motion), or “play” that is present in the teeth. In other words, the amount that one gear can move around without coming in contact with and moving the other gear.
There are several reasons why this occurs, one of which is due to manufacturing imperfections and having to account for them.
However, there are also cases where a small amount of backlash is desired in a system when considering things such as:
- ease of assembly
Nabtesco Backlash Definition
Nabtesco’s definition of backlash includes not only the mechanical gap between parts, but also takes into account the amount of angular displacement that occurs due to loading the gearbox, which can be thought of as energy lost to friction.
This value, along with other specifications shed more light on how the gearbox will behave and position under actual conditions.
We test this on every gearbox by fixing the input side of the gearbox, then loading and unloading the gearbox in both directions. This creates a closed loop called a hysteresis curve which can be used to describe a lot of the gearbox behavior. The backlash that Nabtesco uses is the total torsion angle (angular displacement) at zero torque.
So how are other gearboxes “zero backlash”?
Many gearbox manufacturers choose to use the standard definition of backlash, which is just the amount of free travel between parts. By preloading the gear, or using a different type of gear (such as strain wave gearing) the mechanical backlash is essentially zero as there are little or no gaps between teeth.
However, if tested under Nabtesco specifications, there is no type of gearing or setup that would be zero, as any product will have some sort of friction loss.