Re: [CAD_CAM_EDM_DRO] seeking CNC conversion advice

cloutiertom wrote:

>I just ordered a Rong Fu 45 and am dying to convert it to CNC.
>Basically, I know how to spell CNC, but that's about it. I'd like to
>buy parts that are known to work either on eBay or from a surplus
>house, put them together, and start using the mill! I do research
>work all day long and much of the night and would rather not have to
>re-invent the mill. I'm sure my questions have been asked many times
>before, but any help would be greatly appreciated.
>
>I'd like to use servo motors. What size, voltage, drivers, etc? Is it
>feasible to drive the screws directly without belts and pulleys?
>After the mill is CNCed can it still be used manually?
>

Probzably not if you direct drive it. Clearly, that would remove the handle
from the Y axis, and at least one handle from the X. If you use belts,
you can probably keep the handles. With a servo system that wires the
encoders all the way back to the computer, you could also use the CNC
system as a DRO when in manual mode.

> Is converting
>to ball screws a must?
>

No, but you'll get much better accuracy with them. Acme screws start
out with some backlash, and it gets worse as they wear.

>Is the same size motor suitable for driving a
>rotary table? Can a servo-driven rotary table be accurately
>positioned for jobs such as cutting gears?
>

Instead of a rotary table (which is hardly of any use flat, once you
have CNC) you might look at a dividing head. It is more suited to
mounting a chuck or collets for gear cutting work. Generally a smaller
motor will suffice for this. How accurate do you need it? A high-
quality dividing head should be able to get into the arc-second range
of accuracy.

>
>
>

Jon