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  • Topic: Molds

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    • March 27, 2019 8:09 PM EDT
      • Curmudgeon at Large, Michael survivor
         
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      Some companies do the unexpected. Back in the late 70s I sent a letter to EMD (Electromotive Division GM) requesting a set of drawings for the DD-35 A and B units. I received a set of prints in 3/8" scale (perfect for G Scale) that one would expect to see in MR or RMC. They were huge by 0 Scale standards that I was modeling at the time. I wish I still had them, I lost them in a move between Tennessee and Florida.

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    • March 27, 2019 8:16 PM EDT
      • Burbank, CA
         
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      Hi folks,

      I thought I would step into this discussion and maybe clarify a few things about the mold industry and how a company decides whether to use 3D printing to actually make the part needed OR use 3D printing to form a part and then have it cast. Take a look at this link I have provided here:

      https://www.shapeways.com/shops/backyardtrainco

      This is a 1" and 1.5/1.6" scale vendor who builds ride-on diesels. He also provides 3D printed details for these locomotives. Some of the parts are ABS or other "plastics" materials. Other parts are 3D printed "sintered bronze" or cast bronze that are lost wax impressions made from 3D printed molds. It all depends on the resolution of the printing process. The faster the printing is, then you have a courser (rougher) resolution. Lots of hand work to make it presentable (process is called "Benching"). You make up time in the 3D process AND less cost, but there is added cost to the benchwork it takes to smooth things up. When we did our aluminum castings for the louvered panel doors for our 1/8th scale Baldwin electrics, the part was 3D printed in a "rough resolution". We would have paid quite a bit more for this part to make the mold. The foundry that printed the part did the final bench work by hand and then they used the printed mold part to press into the "sand mold" to make the aluminum sand casting. Scroll down the page on the link above and look at the cost of some of the parts. Most are relatively inexpensive. But take note of the two steam generators.....one is 1-1/2 inch scale and the other is 2-1/2 inch scale. These are NOT cheap mainly because of the fine resolution of the 3D printing.

      We are working with our foundry in Kent, Ohio to make scale model trolley poles. The man I'm working with is using Fusion 360 software (as I am) and we are deciding how best and economically to go forward with combinations of 3D printing and making sand casting molds. So far, it will be much more cost effective to 3D print the parts in a semi rough finish, do the benchwork to smooth the parts and then produce the sand mold for aluminum castings. The cost of these parts to 3D print in a fine resolution would be prohibitive (at least 10-15 times the cost of the castings.

      Also on this Shapeways page, you will find full 3D printed bodies of SD60 shells for HO scale and they are almost $300 each. Multiple that cost for a 1/29th body shell and I very much doubt ANYONE on here will be doling out $700-$800 for a shell. And I also know that those on here using home 3D printers will not have the capacity to print an entire shell, much less a seqment of a shell. These would require 3D printers in the thousands of dollars. All of these devices talked about here whether 3D printers or the software to design the parts needed (also the experience to make any part in the software). 3D Solid Modeling and drawing is not for the faint hearted. Remember you pick the "tools" to use to make your parts that are the most econmical and appropriate. One "tool" won't do everything and some of this discussion above sounds like that is waht is expected of 3D printing. Not necessarily so :).

       

    • March 28, 2019 6:27 AM EDT
      • Pittsburgh, Pennsylvania
         
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      Another point is, have any of you seen an injection molding machine in action? The parts come out of injection molding machines at a rate that no 3D printer could hope to match. So for mass production, injection molding will be the way its done. For small batches of unique parts, that would be the 3D printers niche, at least for now.

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    • March 28, 2019 11:47 AM EDT
      • Shut Up Rooster
         
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      Well, with people paying $1200 for some scarce road names in some locos (go figure) I can see people getting a favorite, never produced (but fits on another chassis) loco.

       

      What would I pay for a Santa Fe E1? A lot.

       

      The issue is clearly the quality level, we are getting pretty close with the latest generation of "hobby printers", the filament printers are clearly not there, the SLA printers are pretty darn good, much less "filling and finishing" and the upcoming SLS printers (see the formlabs web site) might be close enough to print and paint.

       

      I'd love to have one each of all the unusual early Santa Fe diesels.

       

      Greg

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      Be sure­ to visit ­my site, l­ots of tec­hnical tip­s and modi­fications,­ and you c­an search ­for topics­ and key w­ords.


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    • March 28, 2019 12:25 PM EDT
      • Easton , Massachusetts
         
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      Greg Elmassian said:

      Well, with people paying $1200 for some scarce road names in some locos (go figure) I can see people getting a favorite, never produced (but fits on another chassis) loco.

      What would I pay for a Santa Fe E1? A lot.

      The issue is clearly the quality level, we are getting pretty close with the latest generation of "hobby printers", the filament printers are clearly not there, the SLA printers are pretty darn good, much less "filling and finishing" and the upcoming SLS printers (see the formlabs web site) might be close enough to print and paint.

      I'd love to have one each of all the unusual early Santa Fe diesels.

      Greg

      I'm surprised that Mark Demyan  hasn't chimed in...

       

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    • March 28, 2019 1:54 PM EDT
      • Burbank, CA
         
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      David Maynard said:

      Another point is, have any of you seen an injection molding machine in action? The parts come out of injection molding machines at a rate that no 3D printer could hope to match. So for mass production, injection molding will be the way its done. For small batches of unique parts, that would be the 3D printers niche, at least for now.

       

      Yeah, about thirty years ago, the forging industry was taking a hit because of the fall of the Soviet Union and the Berlin Wall coming down. I was laid off and found work in zinc injection mold house with a "captive die shop" (meaning it was a separate entity, but associated with the larger production shop). Zinc is a "kind" of pot metal used for many consumer products. But the finish on the cavities of these molds is usually a polished surface to remove tool marks and grind marks. Just don't want to leave a blemish on the surface of the injection molded product. We even did some aluminum parts. The call boxes along the freeways were made by this company. Even the surface for aluminum products can have a high polish surface on the cavity. But when you start doing plastics, this is an entirely different world. The dies have to be handled with gloves because the acid from the skin of the mold maker can mar the surface of the cavity. The final finish is almost literally chrome plated! NOTHING touches a finished cavity in production or any spot or blemish will appear on the plastic part. This is where the cost of plastic injection dies goes skyward exponentially! 

      Just because a injection molded die is machined exactly to print, DOES NOT mean that it will work properly. There is always the added cost of the "tryout" period before production. Inevitably changes have to be made to the die because of the flow characteristics of the part material or the movement of the die in the injection machine. All machines act differently. It's not "cookie cutter" easy. And like David mentioned, you can produce "bad" parts VERY quickly in these machines. Scrap always seem to go quicker during production rather than an easy "good" part production run. But the injection mold process is by far faster than 3D printing and WILL be far into the future. Definitely not something for the home hobbyist 3D printer unless you have VERY DEEP pockets!

    • March 28, 2019 2:18 PM EDT
      • Shut Up Rooster
         
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      Luckily for us home hobby guys, we can trade time for cost if we are making stuff for ourselves and the machine runs by itself.

       

      I think the biggest challenge is the ability to afford a machine for yourself that has the surface resolution that can be directly painted, not filled and sanded.

       

      Greg

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      Be sure­ to visit ­my site, l­ots of tec­hnical tip­s and modi­fications,­ and you c­an search ­for topics­ and key w­ords.


      ­Click HERE for Greg­'s web sit­e
      PLEASE NOT­E: Please do NOT use private messaging, i­f you have­ a questio­n, feel fr­ee to emai­l me priva­tely, u­se regular­ email onl­y: greg@el­massian.co­m

    • March 28, 2019 2:38 PM EDT
      • West Glocester, Rhode Island
         
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      David Maynard said:

      Another point is, have any of you seen an injection molding machine in action? The parts come out of injection molding machines at a rate that no 3D printer could hope to match. So for mass production, injection molding will be the way its done. For small batches of unique parts, that would be the 3D printers niche, at least for now.

      I never mean't to imply 3d printing would replace injection molding for mass production.  It's my belief that as more folks get access to higher quality 3d printers,  the manufacturers will consider not producing the parts at all and just supplying stl files.  Have you noticed that now if you buy a board game like Stratego, they make you do the work and peel & place all the stickers on the playing pieces?  I'm thinking the next step would be a flat pack with the board, stickers and instructions with links to download and print the pieces yourself.  Imagine how much production cost, shipping, stock space etc. could be saved.  And when you want X-Men or Smurf Stratego they just sell you the files.  See where I'm going with this?

      Let's pretend AML has the CAD files for a GP60 but doesn't get enough pre-orders to commit to injection molding costs...  Hmmm?  How much to rework the CAD files to something printable and offering it in kit form?

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