Re: [CAD_CAM_EDM_DRO] Encoders on the opposite end of the shaft

"Heuver, Brad (B.R.)" wrote:

> My old P&W Tape'O'Matic is set up with the motors coupled 1:1 with
> the ball screws with cogged tooth belts. The tach is on the motor. The
> encoder is on the opposite end of the shaft than the drive cog. Although
> this beast has yet to run for me, it was obviously running this way before
> it went brain dead.

Well, if the screw is belt driven, then I don't see why the encoder couldn't
be put on the motor end.

> It's very likely that the lash/flex in the cogged belt
> was much more than the twist of the ball screw, thereby making the decision
> as to what end of the shaft to sense a moot point.

I have the belt drive setup, with the encoder on the motor end of the screw.
There is a roller that tensions the belt by means of an eccentric shaft,
and it is VERY rigid. They put the belt under a LOT of tension.

> This design might be
> easier to implement than a rigidly coupled motor.

One advantage is motor torque is not transmitted through couplings
this way. A belt can handle the torque a lot better than a servo-class
coupling.

Jon