Re: [CAD_CAM_EDM_DRO] Novice Timing Belt question

Here's a quick sketch of a third alternative:
http://homepage.mac.com/johnatl/PhotoAlbum23.html
Both motors are mounted to the frame, so the beam and head are very
light.

Regards,
JJ

On Friday, November 21, 2003, at 12:05 AM, robertokx wrote:

> I have pretty much given up on trying to economically source a ball
> screw for the long axis and am looking at timing belts.
>
> From the CNC machines on the web it appears that the most popular
> configuration to use is the fixed belt method ie "....the driving
> axis, idle rollers, and platform proceed as a unit along a length of
> belt that's held fast at both ends. Belt and drive sprocket impel the
> load while linear bearings support it"
>
> My question is why isnt the method where the belt is stretched around
> a driving and idler sprocket used more often? ie "....The driving
> pulley pulley and idler pulley of equal diameter are offset. The
> load is linked to the belt and moved parallel to the span between the
> pulleys. This system contains a platform or slider that moves on
> linear bearings"
>
> For diagrams of both systems see:
> http://apps.mectrol.com/applications/doc/linear_day2.pdf
>
> The reason I ask this question is that with the fixed belt method the
> weight associated with the motor, idler rollers etc must all make the
> trip around the table meaning bigger motors may be required, more
> inertia etc and also the fixed belt method appears to require more
> parts. I'm assuming that there are advantages of the fixed belt
> system over the closed belt which more than offset these
> disadvantages.
>
> Thanks for any responses, in advance.
>
> Robert
>
>
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