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4272Fwd: [traintools] Re: DIY Injection Molding vs 3D Printing

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  • Mike Bauers
    Jun 10, 2013
      For now, forwarding some of the interesting stuff I see here and there.

      Maybe I can liven up the place a bit?

      Best to ya...
      Mike Bauers
      Milwaukee, Wi, USA

      Begin forwarded message:

      From: "dcyale" 
      Subject: [traintools] Re: DIY Injection Molding vs 3D Printing
      Date: June 10, 2013 11:42:16 AM CDT

      I have been playing with 3d printing- although the DIY injection molder
      perks my interest, too.  I have to agree about the difference in 3D
      printing doing thing you cannot with injection molding.

      The model I created that gets the most attention is an HO Scale
      port-a-pot (go figure).  I did one with interior detail.

      Port-a-pot <http://www.dcyale.com/shapeways/portpot02.jpg>

      Unpainted it's hard to see the detail, but it shows clearer in a
      computer render:

      Computer render <http://www.dcyale.com/shapeways/portpot01.jpg>

      Although you could make it close by molding the sides separately and
      assembling them post molding, with 3D printing it comes out ready to

      This is made with the cheap nylon material which is a little rough, not
      the more expensive resin.   With cheap acrylic paint a lot of the
      roughness is smoothed out, though.

      I suspect the cost of producing a custom mold would overshadow the lower
      price per unit cost of injection molding, as the market for my
      port-a-pot is most likely fairly limited.  And my main intent is to make
      them for myself, anyway.  This is an item that will not often be seen on
      another layout.

      Now I need a guy walking out with an HO Scale TP tucked into his pants
      leading back to the paper dispenser inside AKA Jackie Gleason walking
      out of the restaurant in Smokey and the Bandit.

      --- In traintools@yahoogroups.com, Tom & Judy Bank wrote:

      DIY injection molding and 3D printing each have their own set of
      potentials and problems.

      With 3D printing the main problems are roughness and the learning
      curve on the software. The roughness goes down as the equipment price
      goes up – or as time goes by. And I guess the learning curve
      improves as the new generations grow up with hardware/software
      familiarity. I'm 75, so you can guess which side of the fence I am on,
      and that's in spite of having a long career as a computer applications
      systems analyst. But the real advantages with 3D printing are the
      ability to one-off samples and improve the product through program
      modification until you get it right. The plastic thread that is the raw
      material for the process is relatively expensive ($5.00 a spool), but
      that will soon change. There is a machine in the works that converts
      ("recycles") milk jugs and soda bottles into the required thread, that
      is expected to be on the market next year.

      Beyond that, 3D printing also has the unique ability to include blind
      or inaccessible spaces in the design. Not sure how that potential would
      be put to use by model railroaders, at least at this point, but I do
      remember that John Allen had a boxcar with a large ball bearing on a
      "rocking chair" track inside. If an operator got careless with his
      consist the bearing would roll up and off the end of the track, short
      out the block the train was in, and light a red light to call attention
      so everyone knew what had happened. With 3D printing, the same thing
      could be done with a hidden space in a load with a little blob of
      mercury fed in through one of several holes that were then plugged with
      wires that were part of the detector circuit.

      With DIY injection molding, the product is as smooth as the mold that
      produces the part. But since you are making an item scaled from a real
      piece, making refinements is limited. If you make a mistake you likely
      have to toss out the mold and start over from scratch. Also, the mold
      requires machining, which involves an investment in both machinery and
      the time necessary to learn to use it. Make no mistake, I bought a lathe
      and mill fifteen years ago to enhance my model railroading. The projects
      that I was working on for which I thought I needed that machinery are
      still sitting on my model railroad work bench in the same state as the
      day my lathe arrived. I've had fun, but it has been with learning to be
      a machinist, not with my model railroading. And I'll add that I took
      prizes for my models at regional and national NMRA meets before I got
      side tracked. So figure out what your hobby priorities are carefully.
      There's a limit on lifespan, and I'm finding out that some of the things
      I postponed to learn skills I thought would aid my modeling will never
      get done.

      Tom Bank