So far OT it's over the horizon: Anyone into 3D modelling?

Well, more techniques for converting an industry stabdard 3d model file into
a 'real world' object. Preferably the material for the model should either
be re-useable or cheap enough to be disposable. Creation time should be <2
hours. Size of model, roughly 2mx1mx1m. Cost of machine, preferably as
cheap as possible.

Anyone involved in anything like this, or can give some pointers as to
search terms?

TIA
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www.arttopart.com springs to mind. Never actually gone as far as using
any such service myself though. You'll need to send out an stl file, I
can do that conversion if you need. Making stuff at 2 meters long is
gonna cost a small fortune though, most sensibly priced machines give
hand held sized stuff. Cane could probably point you into a rough
direction for industrial machines, his snazzy one does ~3x3m stuff but
only up to a few cm deep. (add sexual innuendo as required)

If you actually want something modeling in virtual 3D space, thats as
far as I go www.3dfluff.com

 

Interesting, ta. That might well be ideal
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Needs to be done in house. Sending out is too time consuming, and too
expensive (from what I've seen) We need each model to cost ~£10

He was the first place I tried, actually. Having seen it in action as it
were

Well, we need to scan and reproduce at a remote location

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Except it's not big enough. Cheers
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Jeez mate.

The closest thing I've seen is rapid prototyping which fires a laser
through a gel.The gel hardens to produce a replica from the original
CAD prog. Handy when you want to check a complicated part before
spending many thousands on and injection mould tool.

Unfortunately, from my experience, the process is expensive, the part
is weak and the size limited to ...errr much smaller than what you're
after.

The real expert is my brother, who is a design engineer. He's currently
teaching in Holland but will be back mid week. I'll ask him when he
gets back.

 

Cool innit?

Yep. Looking at some of those earlier. Way too small, costly and
slooooowwww

Cheers mate
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Yeah, but sod all depth. Needs to be 2mx2mx2m, shaped in all axes.
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What you're looking for as others have pointed out is rapid
prototyping. I used to be involved in this and have a mate who runs his
own consultancy. However, it's not that rapid and I don't know of any
machine with a build platform that big. The process Cane is referring
to is steriolithography but the biggest volume on those machines is, I
think 500x500x500mm or thereabouts (http://www.3dsystems.com). For
cheapness (of machine and material) 3D printers are best but their
precision isn't that good as they're really designed to build 'space'
models, and again they're nowhere near that build envelope
(http://www.zcorp.com). Then there's LOM (Laminate object modeller).
Probably the biggest RP machines available but not sure how big they
went. The company that made the machines folded but there are still
plenty of machines around. For example:
http://www.warwick.ac.uk/atc/rpt/Facilities/lom2030.htm

We would quite often split CAD files in order to build customers' parts
in pieces like a giant 3D jigsaw puzzle. Maybe that's an option but
unless things have changed dramatically in the last year or so you
wouldn't get anything that size built using any of the current
technologies in less than about a (24 hour) day.

You could try subscribing to the RP mailing list which you'll find at
http://rapid.lpt.fi/rp-ml/ for people who will know what's currently
available.

 

and for a tenner a pop???

you have LOTS of problems here.......

1/ x + y + z axes of _any_ precisions use something known as ball
screws, 2.5 metre ball screws have a certain minimum cost, even if you
cut out ALL the middle men you'll be looking at IRO 500 quid per axis
per rail, and you'll get a precision of the order of a thou for
that....

yes, you could use precision threaded bar and a couple of nuts to
eliminate backlash, but it's gonna wear quickly, take more power to
drive, and "finesse-ing" it so it works well is going to put the cost
beyond a cheap ball screw

2/ while the "screw" bit provides movement, that movement needs to
slide along something, so you'll need some sort of rails, again you can
use the pukka stuff and spend about 500 quid an axis and not destroy
your precision, or you can try and DIY from stock sections and spend
the same money getting it to work and destroy your precision...

any machine with axes of the order of 2.5 metres is going to have
issues with thermal expansion affecting precision

3/ motive power, cheapest option here is stepper motor and driver
boards, your machine is fairly beefy so these need to be fairly beefy
too, say 100 quid a stepper and up to the same again for the driver
circuitry

only gotcha here is stepper is no feedback, eg "move x amount"
instruction is sent out, there better be enough servo power to overcome
any loads induced or that movement won't happen, but the machine will
simply carry on as if it has.

you can get around this with feedback loops and servos for a closes
loop system, but lots more money an not necessary as long as you don't
try to "drive" it too hard

4/ control, this is the easiest bit, any old PC and a copy of EMC which
is linux with real time extentions designed especially to control CNC
machinery

5/ "work" material and "tool" is difficult, say your material is
aluminium of some grade, a one horespower tool driving motor driving
say a 6mm end mill is gonna take FOREVER to chew through a 2 metre a
size block or work, you want faster production then before you know it
you have a 40 bhp 3 phase motor, and your gantry just had to get 3
orders of magnitude heavier to accomodate it, and so on and so forth...

I can put you in touch with people who have made 2 metre by 2 metre by
not that much machines to do things like router wooden doors and
panneling, which will get you part way there, but....

off hand the only materials I can see you getting and man handling in 6
cubic metre blocks are "man made" foams like polystyrene, the "oasis"
stuff flower shops use, and stuff like that

right away your precision is down to something like 1mm

the size makes me thing you're trying to model something like
motorcycles, life size?

will you want to paint them when done? if so this affects material
choice too...

certainly a tenner a pop means you aren't going to be using anything
more structural than something like a ploystyrene compound

you could go the "add" instead of "remove" material route with a nozzle
instead of a router but that is going to slow you down even more and
make even 1mm precision real hard ("hard" is another way of saying
"expensive and / or slow") to do

let's assume you are wanting to make motorcycles, accurate
dimensionally to 1mm, to be finished by painting...

a/ I'd say you'd be right to be very pleased with yourself to build the
CNC machine for 5000 pounds excluding work head, whether this be router
or extrusion or hot wire or whatever

(you prolly have 200 hours work assembling such a machine and setting
up too)

b/ I'd say you'll be looking at making your own blanks on site from
some sort of foaming plastic, so blanks are prolly gonna cost 30 quid a
pop

c/ I'd say you make about 5 models before you figure out how to make
one properly, just pray this doesn't entail a fundamental machine
redesign, I mean here mebbe cut two female half moulds (if the model
has appropriate symmetry) and vaccum from a thermoplastic in there

d/ I'd say your finished models are still going to come out nearer 100
quid a pop in materials than ten, and they will still need extensive
hand finishing, and labour ain't free

e/ I'd say you might get one model in 24 hours of machine time (you
aren't going to get any "rapids" with axis movements when you've
mastered "roughing" and so on and so forth, so that's 24 hours of
machine attendant watching it.

f/ NOWHERE in this have we gone anywhere near ancilliaries, such a
compressed air of vacuum for chip removal, lubrication, which all
requires significant amounts of power, thermal management, which can be
a bitch and very expensive, and most overlooked, power consumed by the
machine itself and machine maintenance in between runs, which could
scare the crap out of you

------------------------------------------

Don't let me convince you what you want cannot be done, it can be, but
commercially it is vastly expensive, so if you want to cut the cost
down you'd better be prepared for backbreaking work and ingenuity and
sacrificing a lot of functionality here and there, and approaching a
compromise solution, if you do not accept this them you will fail and
waste a lot of time and money doing it, and be turned off the whole
thing CNC wise, which would be a shame.


HTH etc

 

Thanks for this. Most usfeul, in a negative kind of way
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Yes, but can we stick to the topic?

*more* than sufficient.

TBH precicsion ~1mm would probably be sufficient....

Oh aye, unless you stick an optical encoder (for example) on it

That would be ideal. And it was a typo 2x1x1 would be fine

That's convenient, then

No. Nothing like. Much *much* simpler.

No, raw state is fine Doesn't even need to be particularly smooth, though
it would be nice.

Heh. We were wondering if it might be possible to create a mould then fill
with polyurethan foam, or similar. That woul suit our purposes.

Well we could probably go to 5-10 times that amount, although we'd rather
not

Not really an issue

OK, that we can probably accept

Sounds good

Not acceptable

Nah. I'm not funding it

Well, the thing is that the technology we want to use does seem to exist,
but can I damn well find it?

Very much, ta
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Google for Instapack. or similar spelling. We use it at work for boxing
up odd shapes etc. email me if you get stuck.


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Yep, I know the stuff. The problem is making the mould.
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LOL, you're a million miles away, add some more zeros, seriously. the
material for a 2x1x1meter model will cost more than £10. The time and
equipment, you'd have to leave it running 24/7 for years to get back the
investment and break even if you want it for £10 per item and thats
assuming you manage to get the material for free. Hell, you couldnt get
a 2x1x1 block of polystyrene for a tenner what material are you
expecting to cut into for that price?

 

your work area is 2 metres x 1 metre x 1 metre yes?

turn it so we're looking at the 1 x 1 end

the "tool" will cover that in strips up and down one mm apart up 1 m,
across 1 mm, down 1m, across 1mm, up 1 m etc

that gives you 1001 metres if travel in those two axes

and your third axis is 2 metres long

2000 x 1001 = 2,002,000 metres

24 hours = 86,400 seconds

2,002,000 / 86,400 = 23.171

that 23.171 is metres per second

you are suddenly a world away from a DIY CNC machine and into quarter
million pound plus "linears"

ok, real world your tool path ain't gonna be that long, say in the real
world your toolpath is only 1% of this, you end up with 23 centimetres
a second, which is just about at the limit of what you'll do on a DIY,
if you're careful.

ONLY way you're going to cut this down is shed the bulk of the work
blank by slicing off large chunks with hot wire passes and / or
multiple custom tools, eg hot wire custom made end mills in a variety
of sized up to mebbe 6cm dia, you budget just went up because of the
custom tooling

unless you're cutting something like a sofa, you're still going to have
a time issue, the hot wire has to cut clean and not clog, no second
chance...

if you need 3 items a day then use 3 machines.

hard to be more use without knowing what it is you're doing

HTH etc

 

Well, polystyrene would do very nicely, in fact. How does it cost per cubic
meter?
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Not yet, no
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That may well happen. I have some other leads, but thanks for the effort.
It is helpful

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Can you not get a pattern maker to make a replica of your finished
product and then make a mould using carbon fibre or similar?

Part of my job is designing one-off machinery but it doesn't sound as
if that's what you want. If you want to send me a sketch or dwg of the
finished article (or at least a rough idea) then I might be able to
give you some pointers.