Re: Novice Timing Belt question - calculations

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "robertokx" <robert.okx@s...>
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

Interesting idea. I have looked at using a belt for a router/plasma
table.

are there some references to the calculations on belt sizes and
torques and such for determining what is needed ?

also, where does one get a decent price on a belt ?

Dave