Effect of Backlash in Worm Gear

[farzadinjast]

Dear Engineers, I am designing a linear drive and intending to use worm gear to drive timing belt drive pulley. I have found some servo worm gear with very low backlash . They are expensive and I can not afford them now. there are many some industrial worm gears with more backlash but much more cheaper. there is no need to precise positioning (1 cm accuracy is OK) and velocity is more important. I am going to use them but I am not sure are there are some questions:

What will be the effect of backlash in dynamic behavior of my drive. the input speed is 1000 RPM at max (very rare occasion) and input torque is 10 N-m. but there are a lot of turns in rotation direction (the application is vehicle simulator). I wonder if this turns, due to excessive backlash, causes shocks or not.

could the industrial worm gear bear continuous service for 5-6 hours? I think that they are used fr very short duration applications like opening gates.

how is their service. does it need a lot of services and lubrication?

 

[bdeuell]

Will the torque your load puts on the output of your worm gear always be in one direction?

If this torque is not guaranteed to be in one direction the backlash will be felt in the output. You will have no control over the motion of your output within this backlash region. Depending on the dynamics of your load this could present all sorts of problems.

 

[Pedalpowered]

He says it is for a vehicle simulator, if it's for some kind of steering drive then the backlash will be felt, if it's for some kind of actuation with weight resting on it then the contact side shouldn't change.

 

[drawoh]

farzadinjast,

A worm gear can work continuously for 5-6 hours if you select one that is rated to do that. Most of the power you put into a high ratio worm gear is given off as heat. That could create several issues for you.

There are two issues with backlash...
[ol]
[li]Any position sensor on the motor side of your drive will have its accuracy affected by your backlash. On a lot of servo systems, the encoders are installed on the driven end of the drive.[/li]
[li]When you start your motor into the backlash, it will accelerate constrained only by its rotor inertia until it hits the end of the backlash. At this point, it will see your driven inertia, multiplied by the gear ratio squared, and slam into it. This is an impact load, you analyse by working out the energy to be absorbed by your motor shaft and drive.[/li]
[/ol]

If you can live with the backlash error or work around it, you have no problem with it.

You can work out the effect of the backlash impact, and either cope with it, or determine that the backlash does not work.

--
JHG