CNC Machining versus 3D Printing
254 views
Skip to first unread message
Alex Sims
Nov 15, 2012, 3:24:51 AM11/15/12
to hackerspac...@googlegroups.com
I was pointed to "Guerrilla guide to CNC machining, mold making, and
resin casting" from Hacker News (http://news.ycombinator.com/)
http://lcamtuf.coredump.cx/gcnc/ The article
http://news.ycombinator.com/item?id=4679939 Comments from Hacker News
which makes the case that we should not be 3D printing, where a
substrate is built up but instead be 3D machining where substrate is
removed, so a negative rather than a positive process. I've read through
the article a couple of times and it seems to me at least persuasive. I
was really impressed by the super-tiny very-colourful planetary gearbox
the author of the article made. Also a choice of matt or gloss finish on
your articles being made at print time, no sand-paper required. I
haven't done any 3D printing but would seriously like to do some
machining, particularly where I can use a variety of substrates.
Is anyone thinking of going down this path? Could the Innovation lab be
persuaded that they really should buy a CNC machine? Maybe a laser
cutter? Sydney has one, Canberra does, should Adelaide be next?
Alex
resin casting" from Hacker News (http://news.ycombinator.com/)
http://lcamtuf.coredump.cx/gcnc/ The article
http://news.ycombinator.com/item?id=4679939 Comments from Hacker News
which makes the case that we should not be 3D printing, where a
substrate is built up but instead be 3D machining where substrate is
removed, so a negative rather than a positive process. I've read through
the article a couple of times and it seems to me at least persuasive. I
was really impressed by the super-tiny very-colourful planetary gearbox
the author of the article made. Also a choice of matt or gloss finish on
your articles being made at print time, no sand-paper required. I
haven't done any 3D printing but would seriously like to do some
machining, particularly where I can use a variety of substrates.
Is anyone thinking of going down this path? Could the Innovation lab be
persuaded that they really should buy a CNC machine? Maybe a laser
cutter? Sydney has one, Canberra does, should Adelaide be next?
Alex
Andrew Helgeson
Nov 15, 2012, 3:37:59 AM11/15/12
to hackerspac...@googlegroups.com
With CNC machining or "subtractive printing", you need a lot more skill.
It is not as easy as 3D printing, milling is way more of an art.
It makes 3D printing look easy, there is way more "stuff" you need to know/be aware of.
Andrew
It is not as easy as 3D printing, milling is way more of an art.
It makes 3D printing look easy, there is way more "stuff" you need to know/be aware of.
Andrew
Alex
--
You received this message because you are subscribed to the Google Groups "HackerSpace - Adelaide, South Australia" group.
To post to this group, send email to hackerspace-adelaide@googlegroups.com.
To unsubscribe from this group, send email to hackerspace-adelaide+unsub...@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/hackerspace-adelaide?hl=en.
Alex Sims
Nov 15, 2012, 3:49:38 AM11/15/12
to hackerspac...@googlegroups.com
I've just read about Fab Lab Adelaide
http://fablabadelaide.org.au/
They have a laser cutter and a milling machine, I need to start thinking
up things to make...
http://fablabadelaide.org.au/
They have a laser cutter and a milling machine, I need to start thinking
up things to make...
Andrew Helgeson
Nov 15, 2012, 4:47:45 AM11/15/12
to hackerspac...@googlegroups.com
Machining history 101
question, if you need a lathe to make a lathe, where did the first lathe come from?
Think about the first steam engines or trains.
Stevenson's "Rocket" was built with "file technology".
The clearances on the cylinder/piston must have been huge.
From there to here we have made things, to make things to make things, to make things, etc.
If you stop to think about it for a bit, it's pretty daunting
Andrew
question, if you need a lathe to make a lathe, where did the first lathe come from?
Think about the first steam engines or trains.
Stevenson's "Rocket" was built with "file technology".
The clearances on the cylinder/piston must have been huge.
From there to here we have made things, to make things to make things, to make things, etc.
If you stop to think about it for a bit, it's pretty daunting
Andrew
Jamie Mackenzie
Nov 15, 2012, 4:56:28 AM11/15/12
to hackerspac...@googlegroups.com
I recently came across that site too. I was rather excited by it.
Just downloaded the evaluation version of Rhino 3D to get some CAD practise :)
To post to this group, send email to hackerspac...@googlegroups.com.
To unsubscribe from this group, send email to hackerspace-adel...@googlegroups.com.
Damien P
Nov 15, 2012, 6:56:43 AM11/15/12
to hackerspac...@googlegroups.com
On Thursday, November 15, 2012 7:19:43 PM UTC+10:30, Alex Sims wrote:
They have a laser cutter and a milling machine,
Don't get too excited about their milling machine - it's tiny. The laser cutter is cool.
Damien P
Nov 15, 2012, 7:00:29 AM11/15/12
to hackerspac...@googlegroups.com
On Thursday, November 15, 2012 10:26:43 PM UTC+10:30, Damien P wrote:
Don't get too excited about their milling machine - it's tiny.
That's probably a bit unfair, since firstly I know hardly anything about milling machines and secondly I'm sure there's plenty that can be done with even a small machine.
Steven Pickles
Nov 15, 2012, 7:05:53 AM11/15/12
to hackerspac...@googlegroups.com
No, it's fair. It's "cute".
When I get time to fix the svg->toolpath code, I'm thinking of housing the Hackerspace mill (much less "cute") in the FabLab.
pix
--
You received this message because you are subscribed to the Google Groups "HackerSpace - Adelaide, South Australia" group.
To view this discussion on the web visit https://groups.google.com/d/msg/hackerspace-adelaide/-/E4IC0CMfp9kJ.
Jonathan Wheare
Nov 15, 2012, 7:15:07 AM11/15/12
to hackerspac...@googlegroups.com
I am going to take a slightly contrarian stance on this contrarian
article. ;)
The article does underestimate the capabilities of the current printer
models somewhat. The positional accuracy of the Huxleys printhead is in
the order of ten microns - but the practical accuracy is limited by the
size of the extruder, misalignment of the frame and the vagaries of
printing material. That said I have produced parts with dimensions
within three hundredths of a millimitere of the expected value. The
last 20mm ABS test cube I printed has dimensions of 20.06mm x 19.9mm.
This I find quite impressive considering that ABS in *not* known for its
dimensional stability. Feature size of the printed parts are
significantly larger than for a mill though, since the nozzle is 0.5mm
across and you cannot extrude *part* of a stream.
An advantage of additive methods over subtractive is also the ability to
do complex internal structures. In subtractive manufacture you
generally start off with a solid piece and finish up with a smaller
solid piece. The plastic printed parts we produce are hollow (10-20%
infill) with a reinforcing structure to increase stiffness. This allows
parts to be very light while reducing material costs. This can lead to
some interesting issues about internal stresses and failure modes, but
again for most desktop printing users I don't expect too many issues.
The material costs he is quoting seem to be for a full on Resin
stereolithography printer which is a very different (and far more
accurate) beast than a Makerbot or RepRap filament printer. Getting
good filament can be tricky, but will tend to last a long time.
The comments about speed are dead on though. Printing is *slow*.
In the end it is horses for courses. Pick your technology for your
task.
J.
article. ;)
The article does underestimate the capabilities of the current printer
models somewhat. The positional accuracy of the Huxleys printhead is in
the order of ten microns - but the practical accuracy is limited by the
size of the extruder, misalignment of the frame and the vagaries of
printing material. That said I have produced parts with dimensions
within three hundredths of a millimitere of the expected value. The
last 20mm ABS test cube I printed has dimensions of 20.06mm x 19.9mm.
This I find quite impressive considering that ABS in *not* known for its
dimensional stability. Feature size of the printed parts are
significantly larger than for a mill though, since the nozzle is 0.5mm
across and you cannot extrude *part* of a stream.
An advantage of additive methods over subtractive is also the ability to
do complex internal structures. In subtractive manufacture you
generally start off with a solid piece and finish up with a smaller
solid piece. The plastic printed parts we produce are hollow (10-20%
infill) with a reinforcing structure to increase stiffness. This allows
parts to be very light while reducing material costs. This can lead to
some interesting issues about internal stresses and failure modes, but
again for most desktop printing users I don't expect too many issues.
The material costs he is quoting seem to be for a full on Resin
stereolithography printer which is a very different (and far more
accurate) beast than a Makerbot or RepRap filament printer. Getting
good filament can be tricky, but will tend to last a long time.
The comments about speed are dead on though. Printing is *slow*.
In the end it is horses for courses. Pick your technology for your
task.
J.
Damien P
Nov 16, 2012, 2:38:11 AM11/16/12
to hackerspac...@googlegroups.com
So why do hobbyists like 3D printing? You don't need to read a 55000 word article to get started...
This article seems pretty detailed. Could I get a lump of clay, mill a negative out of it (even the fab lab's mill can do that), pour in resin, then smash the clay back into a lump for next time?
This article seems pretty detailed. Could I get a lump of clay, mill a negative out of it (even the fab lab's mill can do that), pour in resin, then smash the clay back into a lump for next time?
Jamie Mackenzie
Nov 16, 2012, 3:03:10 AM11/16/12
to hackerspac...@googlegroups.com
I don't think the clay would make a very good negative. I imagine it would very easily deform especially when the resin becomes hot (over 60 degrees I think) as it cures. But in theory there is nothing stopping you doing that
On 16 November 2012 18:08, Damien P <ath...@gmail.com> wrote:
So why do hobbyists like 3D printing? You don't need to read a 55000 word article to get started...
This article seems pretty detailed. Could I get a lump of clay, mill a negative out of it (even the fab lab's mill can do that), pour in resin, then smash the clay back into a lump for next time?
--
You received this message because you are subscribed to the Google Groups "HackerSpace - Adelaide, South Australia" group.
To view this discussion on the web visit https://groups.google.com/d/msg/hackerspace-adelaide/-/p5JNNRMQkFcJ.
Scott B
Nov 16, 2012, 3:21:56 AM11/16/12
to hackerspac...@googlegroups.com
I think printing is just the flavor of the month (decade)... people have been making hobby CNC mills for many years now so its not talked about as much.
Each has it's own advantages.
Hobby Mills are great for cutting out a flat stuff - as clamping & accuracy are not as much of a problem, once you start doing billet 3D stuff it gets a bit harder, it has to be done in a number of steps and you need to think ahead to work out how you are going to hold it for each step (and know exactly where it is each time you re-position it). You also often need to change tools for different tasks, this can be a pain if you don't have automatic tool change.
Mills can also be noisy and messy compared with 3D printers.
Hobby type printers are great for prototyping - they can make very complex shapes reasonably accurately, and you don't need a massive stock-pile of material on hand to suit what ever you happen to want to build at the time. But the parts they produce generally are very lacking in strength and surface finish compared with something you machine (where you have far more flexibilty over the choice of material to suit your application (alloy, plastic, FRP, wood, steel, etc)
If I could have only one I would choose a mill over a printer as it is ultimately quicker, stronger and has a better finish - if designed to suit the process.
Andrew Helgeson
Nov 16, 2012, 6:03:34 AM11/16/12
to hackerspac...@googlegroups.com
If you want to get into CNC milling, you really need to know how to use a lathe or mill manually first.
3D printing doesn't really need as much of a knowledge base.
When we saw the 5 axis machine at TAF the other week I finally realised what my friend had said about the desktop lathe/mill I had been using.
It basically boiled down to how much you can cut in a single pass.
With a honkin' great 3 phase powered machine you can remove chips, with a small single phase powered desktop machine you can only remove a few thou' in a single pass.
It takes longer to mill something but the results are the same, eventually!
With a desktop CNC lathe/mill it is NOT as simple as putting a billet of material in the machine and hitting "Print".
That being said, manually operating a lathe/mill isn't that hard.
Realistically your first project won't be a scale V8 or something equally complex.
You start with simple projects, get the feel for feed rates, lubricants for materials.
Andrew
3D printing doesn't really need as much of a knowledge base.
When we saw the 5 axis machine at TAF the other week I finally realised what my friend had said about the desktop lathe/mill I had been using.
It basically boiled down to how much you can cut in a single pass.
With a honkin' great 3 phase powered machine you can remove chips, with a small single phase powered desktop machine you can only remove a few thou' in a single pass.
It takes longer to mill something but the results are the same, eventually!
With a desktop CNC lathe/mill it is NOT as simple as putting a billet of material in the machine and hitting "Print".
That being said, manually operating a lathe/mill isn't that hard.
Realistically your first project won't be a scale V8 or something equally complex.
You start with simple projects, get the feel for feed rates, lubricants for materials.
Andrew
--
You received this message because you are subscribed to the Google Groups "HackerSpace - Adelaide, South Australia" group.
To view this discussion on the web visit https://groups.google.com/d/msg/hackerspace-adelaide/-/W1n0Jz5uStoJ.
Reply all
Reply to author
Forward
0 new messages