Re: [CAD_CAM_EDM_DRO] Re: noob laser question

Cristi wrote:

> Hi,
>
> this is one of my questions - and this is why I kept posting the
> method I intend to use for balancing. I feared the spring will somehow
> "oscillate" and the cutting tool won't get the heavy little part that
> needs to be removed.

Well, it is a lot worse than that. because the rotor has mass,
the unbalanced weight applies force to the whole system, which
then accelerates in that direction. It keeps accelerating until
the weight is now on the other side, dragging it back the other
way. In effect, the mass if the rotor is integrating the force
applied to it, inevitably causing the motion to follow the force
by a 90 degree lag. If I understand the physics, it HAS to lag
the mass by 90 degrees at all speeds, and the springs have
nothing to do with it! (They could add additional resonances to
confuse you, of course.)

This is the condition below first critical speed. Once you get
above that speed, then the imbalance becomes totally dominant,
and the rotor rotates about its center of mass, no matter WHAT
forces the bearings apply to it. (Stiffer bearing support and
stiffer rotor, of course, cause the fisrt critical speed to
increase.) If I understand the physics in this condition, the
heavy spot will run LOW, and taking material off the high spot
will INCREASE the imbalance, not correct it!

You might want to check a book or online resources for "high
speed rotating machinery" or "turbomachinery" as they have to go
through extensive design work to put these resonances and
critical speeds where they will do the least harm.

Jon