Re: [CAD_CAM_EDM_DRO] Re: Belt tensioners on toothed belts

When I was working on my conversion I assumed that I could order any length of belt that I needed. Well guess what??? Anyway here is what I did to fix the problem with my Y axis belt being too long.

http://ImageEvent.com/tppjr/rf45dovetailmill

Look under CNC conversion then Y axis.

Thomas
http://QualityPartsOnline.com
http://imageevent.com/tppjr (photopage)

----- Original Message -----
From: ballendo
To: CAD_CAM_EDM_DRO@yahoogroups.com
Sent: Sunday, July 30, 2006 8:56 PM
Subject: [CAD_CAM_EDM_DRO] Re: Belt tensioners on toothed belts


Tom,

Thank you for the details and clarification. In that case...

I'd lose the spring immediately and fix the idler in position to keep
the belt properly sensioned!

What DID you ewnd up doing to fix? (besides electronics repair)

Thank you again,

Ballendo

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <thom@...> wrote:
> No, nothing that sophisticated. The encoders are on the motors.
> Toothed pully on motor is belt connected to gantry drive shaft
(rack
> on both sides) with another toothed pully. The idler arm pivot
> point is closer over the motor than the drive shaft pully but not
> directly over it. The arm is held against the belt using a radial
> force type coil spring. Very little spring tension is applied ,at
> least not enough to counter the different forces, so the belt
flexes
> a lot. since the pivot point is not centered over the midpoint of
> the belt span it flexes different distances based on the direction
> of travel. In this particular case the bolt holding the pivot arm
> had worked loose and it was actually binding as the belt moved
> towards the motor. The motors were strong enough to overcome the
> drag but the overload fianlly took out the axis servo drive
> (Rutex). I won't go into the electronics design other than to say
> there was only one large fuse for all of the drives.
>
> I think a rigid idler would probably be a better appoach ( and
> probably be fewer moving parts).
>





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