Re: All Round Machining

Date: Mon, 15 Nov 1999 10:41:24 +0100
From: Andrew Werby <drewid@...>
Subject: Re: All Round Machining

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

Andrew,

Like Patrick, I also divide the surface into segments usually 180deg,
and rotate my tool cords to suit, then generate the toolpath. Only
issues encountered is need to ensure u rough down enough to allow the
ball nose finishing tool to have room to work. This is especially
relevant with a 180 deg split. Have done many elliptical in cross
section balloon formers using this approach.

[Yes, I can see this could be a problem. 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? Are balloon formers molds (or
positive forms) used to make balloons, or is this a blow-molding term?]

{{ 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.
Would need to be very careful grinding the 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.
Balloon formers, being positive, are dipped in latex, which is then
immersed in a coagulant solution to make it form the balloon.}}


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. 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.}}


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. 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


Andrew

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