Re: [CAD_CAM_EDM_DRO] Re: noob laser question

Cristi wrote:

> Hi guys,
>
> thank you for your answers, my question - can I use a lathe cut tool
> to make this balance ( so I can avoid buying and using that laser )? I
> intend to balance the disc ( which has a shaft in the center ) by
> suspending it on a ball bearing connected with 3 springs at 120 grads
> perpendicular on the axis of rotation. I hope this is a correct way to
> balance it... the disc should go up to 30000 rpm - can I do it without
> the laser?

Sure. The traditional "electronic balancer" uses a dual-trace
oscilloscope, a magnet moonted on each bearing and a coil of
wire to pick up the motion of the magnets. It also has some
optical system to shine a spot of light on the shaft and sense
a black dot there as an index mark. This mark triggers the scope.

You get the thing spinning, and raise the speed until the
vibration becomes strong enough to make a clear wave on the
scope. If both traces of the scope are roughly equal in
magnitude and in phase, then you have a "static imbalance", ie.
the unbalanced weight is roughly between the bearings. If the
traces are in phase but one is much larger, then the excess
weight is nearer on bearing. If they are out of phase, you
have a dipole, with the weights on opposite sides rotationally.

Depending on how the thing is set up, you have to learn how to
interpret the scope traces as to where to remove metal. You do
this with a Dremel or similar tool, and just grind off a little
material at the periphery, then spin it again.

Jon