3D printing as alternative to traditional metalworking

Now we're gettin somewhere as far as being practical for creating pieces of hardware. I'm no CNC/NC control or software writing geek, but with all aspects being open source, actual introduction to 3D printing probably won't get much easier than this approach.

You still need to know mechanical engineering principles to design parts that bear a load.
Since I built prototypes I tend to look at everything through the filter of 'how would I make one?', and for most moving and stationary machine parts the answer is that they need the precision of machine tools for hole alignment, parallelism and surface finish, unless they are toys (or demos) not expected to last. Only the outer packaging shape really lends itself to less precise 3D forming.
And if the part has to be clamped for drilling it's easier to start with parallel-sided stock than to support, clamp and locate an irregular shape.
At Segway I saw stressed moving parts successfully made by 3D printing but I don't think that was the best choice, just the quickest and easiest.
I don't like injection-molded plastic shafts and bearings either. I've replaced them on my extension-arm lamps with metal pins. jsw

"Wild_Bill" on Thu, 5 Dec 2013 07:40:00 -0500 typed in rec.crafts.metalworking the following: For prototyping yes. But there are still some areas of production where "additive manufacturing" is going to have results less optimal than "traditional subtractive manufacturing."
-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

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More info on metal 3D printer
Has a bunch of links

I seen this thing where they make a small model, then they spray liquid steel at it, it hardenes in less than a millisecond. It grows to any size in seconds. then they heat it up and the core melts away.

You're correct Jim, and creating the files for parts, or learning how to, isn't something that I'd want to be doing. A CMM machine or laser scanner would be handy for others like myself, who don't have the capabilities to create files.. not practial for a home shop though.
For myself.. a sketch, measurements and conventional metalworking machines would be more practial.
Having a shop filled with metalworking machines makes the metal 3D machine less useful, but I'm fairly certain that building it would be enjoyable, and having it available would likely lead to more possibilities for using it.
The writer of one article George offered, used a brake drum as a hypothetical use.. which seems to be a poor example to me

Me too. But that has a learning curve and requires space and investment.
It seems to me that the 3D printer makers are trying to stir up a market among non-machinist hobbyists and crafters. I've acquired a wide range of fabrication skills from glassblowing through circuit board design and don't see many places where 3D printing is superior to the traditional methods of producing non-geometric shapes like sand or lost-wax casting. I wouldn't trust a home-made 3D hydraulic valve body or a high-speed pump impeller without a LOT of testing. jsw

software to create g code from stl files is in the public domain. download one at
about stl files
many existing cad/cam programs can create/export .stl files.
There are lots of powerful, free, and open source design tools to choose from. Our favorites include 3dtin.com, Tinkercad.com, Sketchup, OpenSCAD, Wings3D, Scupltris, Autodesk 123D, and the outstanding, open source Blender project. {live links on site -- UG}
POV-ray (excellent tutorials here), FreeCAD, HeeksCAD, and Art of Illusion also have serious fans in the 3D printing world, too, but we haven't done much experimenting with them yet.