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 Post subject: $600 DIY 3-Axis CNC Mill
PostPosted: Fri Mar 06, 2009 2:19 pm 
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http://www.oomlout.com/cnc1.html

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 Post subject: Re: $600 DIY 3-Axis CNC Mill
PostPosted: Fri Mar 06, 2009 5:12 pm 
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I saw that today as well, looks like it still pending.


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 Post subject: Re: $600 DIY 3-Axis CNC Mill
PostPosted: Mon Mar 09, 2009 1:52 pm 
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Really more of a 2.5 axis foam router as the vertical travel is limited by the carriage design to only a few inches. Cutting anything tougher than foam will be a problem due to structure being made of wood and lack of closed loop position control. This is the project that won the first Instructables laser cutter contest if I recall correctly. A cool project with plenty of uses, but milling metal is not one of them.


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 Post subject: Re: $600 DIY 3-Axis CNC Mill
PostPosted: Mon Mar 09, 2009 4:13 pm 
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Build one of these, use it to carve foam molds, then use the foam to cast parts in aluminum
using the 'lost foam' process.
Use the aluminum bits to build a beefier version that can cut metal
...
Profit!


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 Post subject: Re: $600 DIY 3-Axis CNC Mill
PostPosted: Mon Mar 09, 2009 5:53 pm 
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The "dot dot dot Profit!" part might be silly, a la South Park, but that's not a bad mental progression. Could even maybe start with a reprap, eh?
Two things still needed, though: 1) drill press, and 2) workshop. Y'know, to put these machines in.

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 Post subject: Re: $600 DIY 3-Axis CNC Mill
PostPosted: Mon Mar 09, 2009 7:50 pm 
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What's the obsession with CNC machines?

I've never used one, but I have used a regular milling machine, and I'd rather have a full-sized, quality milling machine than a half-pint low-power CNC version, and I think I'd rather have a Reprap than either.

A CNC mill is not a magic device where one pops in a block of material, walks away, and comes back to a fully articulated model AT-AT complete with underhanging Luke Skywalker- that's more akin to the capabilities of a Reprap (or other rapid prototyper). I'd like a laser or water jet cutter- the ability to cut pieces of sheet metal which could then be folded and riveted into useful shapes is quite appealing as well.

Just my two cents.

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 Post subject: Re: $600 DIY 3-Axis CNC Mill
PostPosted: Tue Mar 10, 2009 11:20 am 
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oh i just want a nice 7 axis mill.

rapid proto typing as very slick for certain things, but barring a few type of $$$ machines it doesn't give you a truly workable part. it gives you a GREAT prototype, but once you know all the parts fit, you need to cast, machine or otherwise fabricate a "real" version.

lost foam will do that at a coarse scale (driven by resolution of foam cel density) recasting of sintered models will do that, but they tend to need support stucture, sprues, and a lot of clean up, resin based will be very detailed, but not structural, composite printing can give you various properties depending on binder and filler properties, but you're limited to materials, and deposition modeling is limited in resolution by nozzle accuracy.

if you want a block of wood, or plaster, or metal to be *exactly* what you called out, and retain it's inherent properties, you want to mill or laser it out.

and yes, the big boys, you do spend a while programming, and then you put your block in, allign it, and come back in a few hours or days to find your part sitting there shiny and bathed, and accurate to several thousandths of an inch. and with a 5 or 7 axis, you can get luke literally hanging from a chain cut from a solid block.

that said, i think a ~4'x4' table with laser, rotary tool mill, and deposition head and 3 (maybe 4 or 5) axis will give us absurd ammounts of flexibility.

in short: we build say 3 tables, with indexed sockets for different heads, and could do a laser cut sheet of ply in one bay while a block of foam is cut in another, and a teacup is dropped in the third. you need to cut a BIG foam sign, the mill goes in the big table....


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 Post subject: Re: $600 DIY 3-Axis CNC Mill
PostPosted: Tue Mar 10, 2009 11:17 pm 
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im with the mikes on this one.
a good bridgeport will outmachine any CNC at comparable price. but a fancy mill (of any variety) is not worth shit unless you know how to fixture the damn thing youre trying to cut. thats why machinists get paid.
(on CNC, they also learn toolpath programming)... i digress.

I doubt many of us require tolerances better than .005". (tray inertia makes higher tolerances a little exorbitant, and xyz tolerance stacking becomes more of a pain if you dont have temp and lube control in your machining head)
that said, i think a decent 3 indexing CNC table with is all we really need. (5 axis would be for bonus points - but i think we can work up to it from a 3)
in true rep-rap style - options are like bunnies with em.
we can: mill(obviously), FDM, wireEDM, EDM, lasercut, laserweld, selective UV curing (like SLA), ... the limitations are our ideas and intent.

i guess our choices here are:
-what materials do we want to be able to cut and to what precision?
-would we have one for small scale superfine work, and another for sculptural mastheads?
-do we want a moving machine head (like a laser printer) or a moving workpiece (like a bandsaw?)


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 Post subject: Re: $600 DIY 3-Axis CNC Mill
PostPosted: Wed Mar 11, 2009 1:07 pm 
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movable bed is really best suited to a limited number of applications. you can go a LOT bigger with it, but its much messier to control that much mass.

i'm still leaning towards several movable head machines with interchangable heads.

on the high end cnc machines they now include tool pathing and choice ai's that are distressingly accurate, including forming rough in, on the fly realignment and finish tools. that, we probably don't need, but we'd be looking at more than a nice mortgage anyway.

adding axises 4 and 5 isn't too bad, it's 6 and 7 where you get into precision issues due to alignment errors magnifying via multiple compound angles

realistically .005 precision is more than we'd ever need, as once you start getting into those fine tolerances you need to be finish machining the fit, or doing final surface prep anyway, and i'm not seeing any of us to much of anything that'll require 1/256th inch precision...


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 Post subject: Re: $600 DIY 3-Axis CNC Mill
PostPosted: Wed Mar 11, 2009 2:59 pm 
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Location: Minneapolis, MN
i was wondering about the open source nature of the rep-rap and g-code software.
most of the nice g-code software i know is PRICEY. the free stuff i've seen do a pretty piss poor job at automated toolpath generation. ESPECIALLY if you want to work with non-uniform rational b splines.
if you dont care about nice tangents and surface continuity - then why CNC? might as well mill the damn thing and call the planes good.
if we had the option - i'd like something that doesnt count steps but runs on a "smarter" encoder. amplifying error is always extra fun right? anyone know about g-code generators?

here's the reason i was asking about possibly two options:
if someone is etching/edm'ing/whathaveyou a tiny piece, it'll be far more effective having a low mass moveable tray/workpiece than moveable head.
working on a car styrofoam sculpture (or a giant spoon lets say?) then moving the head is more effective and accurate.

root question - what is the primary purpose (what will we build) with a CNC subtractive/additive machine?
small scale (pun intended), it makes sense to start out small platform.

we can build the parts to make a large scale cnc out of a small scale cnc. heh.


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