Re: [CAD_CAM_EDM_DRO] Belt reduction questions, Please help!?

n1ych wrote:

>Looking for some help. I'm going to be converting a X-3 Desktop mill
>to Cnc using servo motors. This mill is a little larger then a mini-
>mill and about the same size as a small bench top mill like an RF-25
>or RF-30.
>I'm going to be using a 2:1 belt reduction from the servo to the ball
>screw.
>
>First Question: What belt types are people using to do this type of
>conversion? XL, MXL, etc...... How wide of a belt? 1/2", 3/8", 1/4
>etc???
>
>Second Question: My servo motors will be mounted on plates with
>slots so I can tension the belt. I don't know how much these belts
>strecth, How much adjustement do my motors need in order to tension
>the belt? 1", .5", .100" ?
>I'm a little limited in space in how much I can adjust the motors,
>base upon my current design.
>
>

If your pulleys have flanges (at least one needs them or the belts will
walk off the pulley) then you need more adjustment range. I usually
use about 1/2" of travel. I use 3/8" XL belts on my NC retrofits on
the smaller machines. I also have 3/8" XL belts on my Bridgeport, and
they are too small. I was able to snap a new belt shortly after I put
it together. I had to turn down the acceleration in the software to
keep that from happening again.

You probably want the belts quite tight, at least if you have ball bearings
in the motors and leadscrew ends. You might have to moderate that if
some of the bearings are sleeve type. But, with all ball bearings, you can
tension a 3/8" XL belt to something like 40 Lbs strand tension. That would
be an 80 LB radial load on the shafts.

Jon