Re: X-Y Table, Rotary Table for CNC INFO

Hello,

Although I'm in agreeemnt with DaveM about using the EXISTING z axis,
as a "thought experiment", here goes:

First eliminate two columns and regain structural integrity lost by
using heavier plates. This the setup used in many portable
woodworking planers (you may even be able to use
exisitng "replacement parts" for same!); and raw metal is cheaper
than linear motion parts. You also now have only two ball/leadscrews
(and all their attendant stuff). OR...

Think scissor lift table. A couple of accurately placed pivots; ONE
screw, lots of force. Problem: Stability in the direction perp. to
the scissor. Fix that with a vertical guidepost (or two. Note that
these DON'T need to be heavy duty linear motion component quality;
they are just keeping the structure stable in one axis(resisting only
side loads). I'd let the guide rod hang from the top plate, and
extend below the BP mill table at full down position. But...

What have you actually gained here? You don't have large travels...
For a similar cost(IMO), you can have a maxNC, or Taig, or
Sherline... So it seems you only have the advantage of using your
existing "large mill" tooling; most of which will likely overload any
table built inexpensively anyway!

But as a thought experiement...

Hope this helps,

Ballendo

P.S. The CLISBY lathe and mill are similar in size to the Proxxon Tim
recently mentioned. They are made in Australia by (I think) Ron Sher,
who invented the Sherline lathe. Prices are VERY reasonable; and
either would make an okay learning platform for cnc.


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Marcus & Eva" <implmex@a...>
wrote:

> Hi Les:
> Sounds a bit like a screw that has been unrolled from around its
> shaft!!! : )
> Best way for this approach might be a pair of wedges mounted on

linear ways

> tipped up at an angle.
> Kind of like a ballscrew unrolled from around its shaft.
> Do you think four linear ways and one ballscrew would be cheaper

than 4

> ballscrews, nuts pulleys and timing belt?
> What about rolling it uphill on wheels (bearings)?
> This thought experiment is starting to show some promise!!
> Cheers
>
> Marcus
>
> ----- Original Message -----
> From: "Les Watts" <leswatts@a...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Thursday, January 16, 2003 2:11 PM
> Subject: Re: [CAD_CAM_EDM_DRO] Re: X-Y Table, Rotary Table for CNC

INFO

>
>
> > Dave,
> >
> > You're right about stubby ballscrews being very expensive.
> >
> > Most of the real cost the nut, end machining, and end bearings.
> >
> > So a 5" ballscrew might cost almost as much as a 5 foot one!
> >
> > You mentioned punch dies.
> >
> > What if you used 3 or 4 sliding bearing columns like many
> > die sets but performed z axis with 3 or 4 corresponding
> > sliding wedges (actually linear cams)? The wedges would
> > translate a single horizontal motion into an accurate
> > "parallelogram" type vertical motion. Perhaps using cam
> > follower bearings with strong spring preload. I have seen
> > some machines made this way.
> >
> > Just trying to think of how to get the cost out of something
> > that you could just bolt on and go... or optionally bolt
> > on a simple fixed spindle structure later.
> >
> > Les
> >
> > Leslie Watts
> > L M Watts Furniture
> > Tiger, Georgia USA
> > http://www.alltel.net/~leswatts/wattsfurniturewp.html
> > engineering page:
> > http://www.alltel.net/~leswatts/shop.html
> > Surplus cnc for sale:
> > http://www.alltel.net/~leswatts/forsale.html
> > ----- Original Message -----
> > From: <david_mucha@y...>
> > To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> > Sent: Thursday, January 16, 2003 8:36 AM
> > Subject: [CAD_CAM_EDM_DRO] Re: X-Y Table, Rotary Table for CNC

INFO

> >
> >
> > > Hi Les,
> > >
> > > I think a simple adapter on the fine feed of most mills would

be very

> > > easy. just mating gears with a slip connector, like a reverse

ring

> > > gear. I think there are similar units for shaft alignment.
> > >
> > > remove for easy manual. all it would need is one mount for

torque

> > > and then just software home setting.
> > >
> > > Seems much easier than a rising table.
> > >
> > > My punch dies with ball screws are EXPENSIVE in short strokes.

I

> > > think the ridigity would make a power Z better tan a power

table.

> > >
> > > imho.
> > >
> > > Dave
> > >
> > >
> > >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Les Watts"

<leswatts@a...>

> > > wrote:
> > > > Hi Marcus
> > > > Hmmm I guess 4 short ballscrews with timing belt or something.
> > > > Kind of like my wood planer.
> > > >
> > > > It would have to be rigid, but it might be so small that it

would

> > > not
> > > > be too heavy.
> > > >
> > > > Just daydreaming really... people often ask if I can design a
> > > > small cnc with good accuracy for an arbitrarily low price...
> > > > but the price usually turns out high. Manufacturing even small
> > > > machine tools in the US is a pretty rough proposition....

consider

> > > > Bridgeport, South Bend, et al. But one can do it for a hobby
> > > > with no problems! As a business I only build machine tools
> > > > for internal use and that has worked out ok. Of course I do
> > > > design some production machine tool components, but
> > > > the development cost is pretty high for my customers.
> > > >
> > > > Les
> > > >
> > > > Leslie Watts
> > > > L M Watts Furniture
> > > > Tiger, Georgia USA
> > > > http://www.alltel.net/~leswatts/wattsfurniturewp.html
> > > > engineering page:
> > > > http://www.alltel.net/~leswatts/shop.html
> > > > Surplus cnc for sale:
> > > > http://www.alltel.net/~leswatts/forsale.html
> > > > ----- Original Message -----
> > > > From: "Marcus & Eva" <implmex@a...>
> > > > To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> > > > Sent: Wednesday, January 15, 2003 11:10 PM
> > > > Subject: Re: [CAD_CAM_EDM_DRO] X-Y Table, Rotary Table for

CNC INFO

> > > >
> > > >
> > > > > Hi Les:
> > > > > Were you thinking of a four poster bed type of setup

with a

> > > central
> > > > > screw?
> > > > > Or maybe four timed screws with encoders or steppers slaved
> > > together?
> > > > > I suppose you could chain drive them or belt drive them

from one

> > > stepper
> > > > > too.
> > > > > That could work pretty well I think, if you used good hunky
> > > frictionless
> > > > die
> > > > > bushings and pins.
> > > > > I'm thinking of the kind that have sleeves with balls in

them;

> > > the ones
> > > > > that are used for big punch dies.
> > > > > You could make the base wide enough that the pins hang over

the

> > > edges of
> > > > the
> > > > > mill table as they come through the base plate.
> > > > > That way you wouldn't lose too much height under the

spindle nose.

> > > > > Gonna be a pretty heavy accessory unless you make the base

out of

> > > > aluminum.
> > > > > Cheers
> > > > >
> > > > > Marcus
> > > > >
> > >
> > >
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> > If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com to

reach it if

> you have trouble.
> > http://www.metalworking.com/news_servers.html
> >
> > http://groups.yahoo.com/group/jobshophomeshop I consider this

to be a

> sister site to the CCED group, as many of the same members are

there, for OT

> subjects, that are not allowed on the CCED list.
> >
> > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY

POSTING THEM.

> DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> > bill
> > List Mom
> > List Owner
> >
> >
> >
> > Your use of Yahoo! Groups is subject to

http://docs.yahoo.com/info/terms/

> >
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