From: snidelyd@netscape.com   
      
   Craig Fink  wrote:   
      
      
   > I've never built any hardware, so from my point of view I'm somewhat   
   > ignorant of the real world problems. That said, I would think that a 3-D   
   > metal printer would really free up or eliminate some of the design   
   > considerations wrt to just being able to manufacture something.   
   > Multi-part objects can become one because there is no longer the   
   > requirement to fit   
   > the manufacturing tool in to produce it.   
      
   A quick scan of the Pro-Metal pdf indicates that it may be early to make   
   this claim.   
      
   For instance, it appears that voids in the part either require good old   
   drilling out, or making the part in 2 pieces, each with half the void.   
   When a variation on "lost wax" casting gets included with this, that issue   
   may disappear.   
      
   I would think the sintering process would also have some negatives for   
   critical-dimension parts -- how much shrinkage would the part undergo, and   
   can it be predicted accurately enough to maintain tolerances?  The obvious   
   answer is to finish up with machining, but that may negate the "no need to   
   fit the manufacturing tool in" advantage.   
      
   Also, can grain production be controlled appropriately with this process?   
   Many parts with severe service requirements require precise control of the   
   grains ("tempering").   
      
   I think the print-a-part scheme currently wins only for low volume or   
   prototype production where making jigs or molds would be prohibitive.   
      
      
      
   > [...] I would think that the process could even be   
   > stopped in the middle of producing a part. That way, internal areas of   
   > the> part could be machined if necessary to meet tolerance requirements.   
   > Then   
   > restart the 3-D building process to finish the part. Or print head   
   > changes, like changing colors, print different metals or transition   
   > slowly   
   > from one metal to another. A transitional alloy. Or, build internal   
   > stress  relief areas to isolate thermal stress to one or two dimensions.   
      
   This may be possible, but it would require being able to accurately   
   recalibrate the positioning mechansism to the part after each change.   
   Probably within fidiciual art these days, but do the current print-a-part   
   machines have that capability?   
      
   /dps   
      
      
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