Re: [CAD_CAM_EDM_DRO] Re: Knee for z-axis control?

Both my series I and series II Bridgeports that were factory CNC's had the z
axis on the knee. They both also had air/oil actuators on the quills for
drilling etc, but the precision z axis was the knee. IIt was slow, but very
accurite.

----- Original Message -----
From: "doug98105" <DougR@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, September 16, 2004 1:27 PM
Subject: [CAD_CAM_EDM_DRO] Re: Knee for z-axis control?


> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "pondindustrial"
> <pondindustrial@y...> wrote:
> > Hi all,
> >
> > I will be retrofitting my Bridgeport mill soon and know that some
> > have used the knee for z-axis control. Does anyone here have any
> > experience with this method? If so, what should I take into
> > consideration if I decide to go this route? The mill has a 9" X
> 48"
> > bed.
> >
> > Is a counterweight to offset some of the lifting load preferable?
> > Did you use the original acme screw/nut, or retro with a ballscrew?
> > What would be a reasonably sufficient drive in terms of motor
> torque
> > and gear reduction?
> > What are the pros & cons of using the knee opposed to the quill?
> >
> >
> > Thanks, Eric
>
> To my knowledge there are no commercial CNC knee mills (B'port clone
> types) with the Z on the knee. Ever wonder why? You would think
> that at least a few builders of CNC machines might use this method
> if it had some merit.
>
> In spite of the apparent success of some conversions mentioned here,
> to me it seems like total nonsense to have that much mass jumping up
> and down at traverse rates we normally expect of a CNC mill.
>
> Just my $.02,
>
> Doug
>
>
>
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