Adding a 4th rotary axis?

[bfredo123]

Hi all,

I have just found this forum, and this is my first post on it.

I have built a small 3-axis CNC machine, which works pretty fine so far.
You may have a look at pictures and videos here:
http://fredericbaumann.free.fr (CNC section)

I would now like to add a 4th axis, with a rotary table, controlled by a stepper engine. My problem is that I don't know how to make it move.
- I can definitely not directly plug the engine to the table axis, the resolution would be way to low (48 steps/round).
- I could use a belt, with a small whell on the engine, and a big one on the table axis
- ...

Could you please let me know what is the best practice for doing this? I could find no example of DIY rotary axises, I could only see linear axises moved by a screw, but this does not fit with a rotary axis.

Hope my question is clear, please let me know otherwise! :-)
Thanks,
bfredo123

[daedalus]

Hi,

Most people buy off the shelf rotary tables and mount the stepper where the drive handle goes, using the gear ratio of the table to get the resolution they need. Heres an example:

YouTube - CNC Rotary Table Conversion

YouTube - CNC Rotary Table Conversion

Tom

[jalessi]

Bfredo123,

This is a good read.

http://www.cnczone.com/forums/showthread.php?t=15078

Welcome to the Zone.

Jeff...

[bfredo123]

Hi,

Many thanks to you both for your prompt answers! :-)

These are definitely useful ideas for what I want to do.
bfredo123