XPost: sci.space.policy, sci.physics, sci.electronics.design   
   From: jfindley@cinci.nospam.rr.com   
      
   In article , jimp@specsol.spam.sux.com   
   says...   
   > 3D printing requires special raw stock manufactured just for 3D printing   
   > no matter what the print material is.   
   >   
   > 3D printing is slow and expensive compared to any other method of making   
   > parts so only become economical if the part in question is so complex that   
   > 3D printing it is cheaper than any other method.   
      
   Actually if the 3D printed part replaces many other parts (e.g.   
   SuperDraco engines) then it's faster to print than it is to manufacture   
   and assemble all those other parts.  But that does fall under your "so   
   complex" exception because in that case it is cheaper to print than try   
   to use other manufacturing techniques.   
      
   In aerospace, think things like liquid fueled rocket engine combustion   
   chambers with lots of tiny internal cooling passages.  Those are a   
   p.i.t.a. to make using conventional manufacturing techniques, but a   
   breeze to 3D print.   
      
   > The cost and speed of 3D printing will obviously never match that of   
   > stamping out sheet metal, casting, or NC machining.   
      
   For "trivial" parts, that is true.  I installed a new garage door at   
   home a few weeks ago.  Lots of stamped sheet metal parts there, even the   
   hinges.   
      
   > > But progress is being made in the field.  GE is working on producing a   
   > > 3D printer capable of printing 1 meter x 1 meter x 1 meter parts.  This   
   > > is coming from its aircraft engine division.  3D printing is a very hot   
   > > topic these days.   
   >   
   > Yes, for very complex parts that would otherwise have to be made in   
   > pieces then somehow assempled.   
      
   Exactly.   
      
   Also, the other option that 3D printing opens up is more shape optimized   
   parts.  These things are optimized so that "useless" mass is simply gone   
   from the design.  They tend to look "organic" rather than "machined" due   
   to their complex shapes.  I've heard this called "light-weighting" parts   
   from management types.   
      
   Jeff   
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