RE: [CAD_CAM_EDM_DRO] Re: Homemade mill (was Very small miller/engraver)

Thanks Dave for your subdued compliments ;-)

See comments below ***

-----Original Message-----
From: dave_ace_me [mailto:davemucha@...]
Sent: Saturday, March 02, 2002 7:48 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Homemade mill (was Very small
miller/engraver)


wow, you guys are thinking too simple !

what about using expensive precision ground shaft and realy expensive
linear ball bearings ? what are you trying to do ? make it easy ???

One thing that comes to mind is to use a long table for the X axis
and one of those smaller 4"x4" ones for the spindle. only problem I
see is that if you have a center point and rotate the head, the
cutting bit goes way off center. But then if you rotate the column,
it goes off center the other way, (but not as much) and you lose
rigidity. (like the mini-mill)

*** In this case, the advantage of using a tilting milling table for the Z
axis is that you can reposition your cutting bit with the table's
handwheels. And you don't loose rigidity.

For strength, but at the risk of being ugly, you could put a pair of
I beams or Channels from to back, then weld a pair of them as
uprights, and then put in angled bracing from the top to the back.
This would be strong, and simple.

*** I thought about that but you still have a length of un-supported beam
between the vertical frame member and the bottom table. Rigidity will then
depend only on the beam's bending strength. And putting the braces toward
the front will interfere with the work. It has to be kind of a cantilever
arrangement, I"m afraid.

Regarding alignment, you could have it machined or just shim it.
Shimming would be easier and allow you to work out some of the bugs
before sending it out.

/||
/ || table
/ || here
==============

Dave

*** I want to be able to machine steel with this machine, so that's why I'm
aiming for high rigidity and mass.
Your comments are appreciated,

Guy

--- In CAD_CAM_EDM_DRO@y..., "Guy Sirois" <guys@w...> wrote:
>
> Hey Ballendo,
>
> that's almost exactly what I am doing right now !
> After having searched unsuccessfully for an affordable small mill
for the
> last few years, I decided to make one from two small 5-1/2" x 12"
milling
> tables. I bought them from BusyBee in Canada but are the same as
Enco's
> 201-2826. I will mount them as you describe, with one exception,
the
> vertical one will be retained by its center, so it will be
rotatable (5th
> axis). As the mounting base is round, well it will be anyway, after
I put it
> in the lathe, its edge can be graduated in degrees.
>
> As a spindle, I am using an ER-20 collet extension, which is a
precision
> shaft of 1" dia by 6" long with a collet chuck at the end. It will
be
> installed in a steel block of 4 x 4 x 6" bolted to the vertical
table. I
> will use adjustable taper roller bearings. I have two 90V.DC
variable speed
> motors I will (somehow) attach to the spindle.
>
> The base of the machine is not totally defined yet. As I want
something very
> rigid and massive, I have to be sure the back support member can
not flex at
> all relative to the bottom plate. I was thinking of using large
structural
> steel rectangular tubing of 8" x 10" x 1/2" wall. One length is
laid on its
> side and serves as the base, then another length is put vertically
on it to
> act as the back support member. That should theoretically be very
rigid, and
> can even be filled with cement if necessary. I would obviously have
to have
> the end of the vertical piece precisely squared at a machine shop.
>
> The bottom piece could also be made from a H-beam. The rear piece,
however,
> could not, as I will have a large bolt going through it ( the pivot
for the
> 5th axis) and the web of the H-beam is in the way.
>
> The frame could also be made from two thick steel plates, but then
I might
> have to brace them together to reduce flex.
> Anybody has ideas for a rigid L frame ?
> Anybody else done something similar ?
>
> Regards,
>
> Guy
>
>