Re: W.E.T.??: [CAD_CAM_EDM_DRO] Re: motor sizing vertical slide EDM

Hi Wayne and Bill:
Jon's proposal was to hang the weight from a spring to keep tension on
the chain or cable when the direction reversal is high frequency low
amplitude and high acceleration.
The concern implied, was that the briefness of the motion event was likely
to leave the counterweight unable to keep up since it would be able to
accelerate only under the influence of gravity, whereas the head is driven
by a ballscrew and could be driven at higher acceleration rates than 1G,
thus hammering the drive chain or cable to pieces.
The difficulty I potentially forsaw was the spring beginning to function
much like a trampoline, resulting in ever increasing amplitude of vertical
motion of the counterweight dangling from it.
Damping the system in oil would reduce the responsiveness of the
counterweight even more, so I cannot see the combination of spring, oil and
counterweight resulting in the goals of high response speed with reduced
screw loading (which was the objective of the counterweight)
I'd venture that the best outcome would likely be to just engineer a motion
system that's robust enough to handle the mass of the slide unaided, or
accept a simple counterweight and limit system acceleration to below 1G.
If it was me, I'd build it beefy and simple, and that sounds much like what
Tom (the original poster) intends to do, especially since his stated goals
require high accelerations.
Cheers

Marcus

----- Original Message -----
From: "Wayne Weedon" <wayne@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, May 14, 2006 5:43 AM
Subject: Re: W.E.T.??: [CAD_CAM_EDM_DRO] Re: motor sizing vertical slide EDM


> wthomas@... wrote:
>
>>Hi Jon, Marcus and All:
>> This is a very interesting discussion to me as I was thinking of
>>putting such a counterweight on the head of a bed mill and the effect
>>that it would have when pick drilling. What would happen if the
>>counterweight had through holes in it and set in a container of 90
>>weight oil? Do you think the oil would dampen it enough or am I
>>dreaming?
>>
>>
>
> Bill. My vmc (also a bed mill) has a large counterweight hung on two
> roller chains, and passes over two sprockets for each chain on the
> column. True under certain conditions (especially peck drilling) it
> does oscillate and knocks against the tunnel it's in. It never gets
> violent! and I just ignore it.
>
> Wayne...