Re: All Round Machining

John Harnedy <machatak@...> wrote:
Subject: All Round Machining

{ Andrew, dont have need of such long access as you, but seem to
recollect hearing of somebody several years ago in Europe doing
prototype cnc work after grinding a long series concrete/masonary drill.}

[Will drills really work like milling cutters? I thought they would be more
likely to flex, since the flutes are so long. Also, don't the flutes have
to be ground differently if they are intended to be used for sideways
cutting? Or did the person you refer to do a complete regrind on the drill?]

Would need to be very careful grinding the insert,

[Are you talking about a cutter with a carbide insert? ]

but worth a try.
Will check with my suppliers if there any extra long but thin ball nose
available around here, have not seen any, but wil check with my
contacts.

[That would be great!]

Balloon formers, being positive, are dipped in latex, which is then
immersed in a coagulant solution to make it form the balloon.}}

[What's in the coagulent solution? I've made latex molds before, but it was
a long process, since one has to wait hours for drying between ultra-thin
coats. Sounds like this coagulent would speed things up. I've seen positive
latex glove-formers, but they were made by electrotyping.]

Another issue is that the cam software must take account of gouging in
ajoining surfaces. Be especially careful of approach and retract macros,
they can easly trip u up.

[What CAM software are you using? Does it let you get in and play with
the
macros?]

{{Andrew, am lucky that i work as technical manager in a CAD/CAM dealer
during
the day, and hence have access to Mechanical Desktop coupled with
hyperMILL
from Openmind. A really high end cam system, lots of customization
capabilities
like macros and strategies, check it out on www.openmind.de.

[Interesting- I'd never heard of this one. It does sound powerful. Have you
tried their NURBS toolpaths? Did it really help smooth things out? It says
it has support for fourth-axis indexing, which is what I'm (still) trying
to do. How does it work in this program- do you simply rotate the part and
it calculates the amount of milling necessary, subtracting the portion
already done in another position? If it did this, it would be more
efficient than what I'm doing, which results in some duplication of
efforts- although I suppose I could estimate and subtract the surface that
should be milled in a previous milling pass and adjust the segments
accordingly. ]

For more
mundane work, use
surfaces part of Mechanical Desktop,(used to be called AutoSurf in
AutoCAD R12 era)
and offset toolpath and convert with maxnc via dxf application.}

[I'm afraid MaxNC's dxf converter is only suitable for 2d dxfs- it won't
convert surfaces.]


Only subscribed to group a week ago and found it useful, especially the
maxnc articles. Must admit whilst maxnc 10, has a few limitations, it is
still a good entry point to many home machinists. Use it for plastics
and some balsa, so my real desire is faster feed like 500mm/min
(20"/min!! Anybody got it up to this speed? Would like to know details?

John

[I think the maximum speed with the supplied steppers (even the bigger
145
oz/in ones) is around 8"/minute. Crank it up much more than that and you
start getting weird behavior. But the good news is that MaxNC has come
up
with a set of servo-motors and controls that are supposed to boost the
speed to around 45 in/min - not impressive by the standards of "big
iron",
but quite a leap in performance from the steppers. Not having to worry
about lost steps would be a boon as well. I've ordered some for my MaxNC
15
mill, and will let you know my opinion when I've got them installed and
running.]

{{ just this afternoon, one of my customers who is an
electrical/electronics guy,
dropped in for some 2D AutoCAD training, and discussed my need for speed
with him, anyway he thinks it is possible to build a more powerful
circuit,
having looked at the MaxNC board, that will run on maxnc software.
Know of a cheap manual 250kg mill for sale, similar in size to CNC
Junior,
so may give it a try with steppers 500+oz-in, if the electronics guy is
still
positive in a few days time.}

[From what I've heard, those steppers might still be a bit underpowered for
the job- it evidently takes some serious "muscle" to push that iron around.
What do you think, Matt?]

{{Will trade him some, probably a lot, of
training hours.
However am still interested in boosting the performance of my MaxNC, so
keep me informed of your testing. 45"/min is really a mega improvement}}
John

[Will do- thanks for the help!]

Jon Elson <jmelson@...> wrote:
Subject: Re: Re: All Round Machining

A.Werby wrote:
[I've been researching the

> availability of extra-long (6"?) but thin (1/8") ball-nosed milling
> cutters, and whether they would have a tendency to whip or snap. Anybody
> used these? Any luck? Carbide is more rigid than HSS, but also more
> brittle- or should I look for titanium?

I would immediately forget this, unless the work material is soft wood,
foam or the like.

[That's what I had in mind, actually. My basic idea is to make prototypes
in as light a material as will maintain decent surface quality, (basswood,
renshape, rayite, etc.) then take rubber molds of these for casting in
other more durable materials.]

I have a couple long end mills. In particular, a 1/4"
diameter, 4-flute end mill with about a 1.5" length of cut is totally unusable
on any metal. If you go for even .001" feed per tooth, and maybe a .050"
length of cut, it starts screetching and giving horrible surface finish. This
is a stellite tool, I believe.

[How long is the whole thing? And what is stellite?]

Solid carbide would be a little better, but there's
no way a 6" long 1/8" diameter tool would work. With light feed, I don't
think it would break, but it would still vibrate horribly.

Jon

[Perhaps the better idea, then, would be to look for a tool that had a
thicker shank, but tapered or stepped down to a fine ball-end? Anybody know
of anything like that? I'd like to be able to carve deeply-indented forms
without jamming my chuck into the work, if possible.]

"Darrell Gehlsen" <darrell@...> wrote:
Subject: Re: Re: All Round Machining

Have you tried a mini extension collet chuck?
Darrell

[No- where would I find one? I've tried drill extenders (not on my mill,
though) and thought they added a lot of slop and error to a drilling
operation. But perhaps these extension chucks are more precise?]

Andrew Werby

Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com