Worm Wheel Backlash 1

[Parsnip]

Morning all,
I wonder if anyone can help me.
I have a worm/wheel arrangement driven by a stepper motor and the other end of the shaft mounted in a small (3mm ID) ball bearing. As the application is optical I want to take up as much backlash as possible and am thinking of putting a spring between the worm and the bearing to provide an axial force.
My problem is I am not sure about the end of the spring being located on the bearing - please can anyone provide either a description of how I can do this or point me in the direction of a good web or book resource.
Thanks in advance
Parsnip

 

[MikeHalloran]

You could use a belleville spring. I'm not sure you can get them that small. Or you could make the bearing a slip fit in its housing, and spring load the outer race.

OR

You could shim the wheel a little along its own axis.


I don't hold out a lot of hope for a 3mm ID bearing being hammered by a stepping motor.



Mike Halloran
Pembroke Pines, FL, USA

 

[eromlignod]

I like the Belleville idea except I think you will find that they are too small ID/large OD. Have you considered bearing pre-load springs (basically wave washers). They have OD/ID combinations that are suitable for most standard bearings. Hope this helps.

Don
Kansas City

 

[drawoh]

Parsnip,

I look in the W.M.Berg (

http://www.wmberg.com)

and the Nordex (

http://www.nordex.com)

catalogues for stuff like this. They have tiny springs, bearings and preloaded gears. In your area, Stock Drive Products and PIC might be more convenient. Most of their stuff is interchangeable, so you have a second source for your stuff.

If you using custom gears, tell the fabricator you are preloading them. For spur gears, they can wiggle tolerances around a bit. I am not sure about worm gears. It cannot hurt to ask the experts.

JHG

 

[MikeHalloran]

You can take up all the backlash if you split the wheel and spring- load the halves against each other, just like you do with spur gears.

The usual instrument gear suppliers stock split spur gears. I don't think anyone stocks split worm wheels, but they can certainly make them.



Mike Halloran
Pembroke Pines, FL, USA