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Where To Get Plastic Injection Molded?

Discussion in 'Builds and Fabricators Forum' started by Jeff Bromberger, Oct 18, 2019.

  1. Oct 18, 2019
    Jeff Bromberger

    Jeff Bromberger Quarantined in the Garage 2020 Sponsor 2019 Sponsor

    Dallas Metroplex...
    Jun 28, 2019
    So, I've got a fabrication question.

    I have a pair of front fender turn signals on my DJ-5C, and the amber has all but been bleached out of the plastic lenses. These are the square lenses that have the wire cage/support on them.

    While the front pieces are still available, the rear ones (which are different and have a slightly different outside profile) are not. I'd like to know if there is a place that will take my complete but non-amber lens and can make a small-volume mold from it, so that they can cast me a small number (say under 20) for use.

    If this was for gold/silver, I've had this done before. Never tried it for plastic, though, so I am looking for guidance here.

    Thanks in advance!
  2. Oct 18, 2019

    PeteL Member 2020 Sponsor 2019 Sponsor

    Hills of NH
    Aug 3, 2003
    Regarding the "small number" I'm not sure that matters.

    Years ago a cast iron foundry offered a quote to my boss by saying, "The first one is $1000. The next 100 are free..."
  3. Oct 18, 2019

    Alan28 Well-Known Member 2020 Sponsor 2019 Sponsor

    Châtillon en...
    Oct 21, 2012
    it will cost a lot. Easier maybe to make the part in a piece of zinc or plastic. I use zinc. It is possible to make parts with polyester fabric and epoxy putty. Take time to study you'll get the good cheap solution.
  4. Oct 18, 2019
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

    Tantallon, Nova...
    Nov 22, 2003
  5. Oct 18, 2019

    Keys5a Sponsor

    Florida Keys
    Jan 23, 2014
    A friend of mine tried molding Lucas tail light lenses for our British cars. The lenses came out great, but the color didn't, translucent red in this case. They were either too light, too dark, too opaque, etc. Some even looked good until they were installed, with the bulb lighted.
    Do your lenses have any manufacurers nane/part numbers? I guess you know there is a Postal Jeep specialist out there?
  6. Oct 18, 2019

    Twin2 not him 2020 Sponsor 2019 Sponsor

    Virginia Beach, VA
    Apr 28, 2011
  7. Oct 19, 2019
    Jeff Bromberger

    Jeff Bromberger Quarantined in the Garage 2020 Sponsor 2019 Sponsor

    Dallas Metroplex...
    Jun 28, 2019
    OK - after a bit of research, maybe the way to do this is to go whole-hog and cast them myself. For $250 in supplies and tools, I should get a permanent silicone mold to keep, plus 3 or 4 of the lenses at the end of the day.

    Thanks to Mr. Eisenhauer and his suggestion for Smooth-On. They actually have a YouTube video on how to make a replacement auto lens! How much better can that be?

    Sure, it seems like a lot of money. At the end of the day, it'll be exactly what I want and for a lot less than paying somebody for the work. FWIW: The most expensive single piece will be a Harbor Freight pressure tank - casting of resin is done under pressure (whereas investment casting for gold and silver are done in a vacuum).

    I've now got a road map of where I need to get to. Thanks to all!
  8. Oct 19, 2019

    Hellion Banned

    Eastern TN
    Dec 25, 2016
    Maybe you don't have to go to the trouble of reinventing the wheel. You could paint or re-tint them with a translucent amber/orange color. For example:

      Tamiya Polycarbonate Translucent Orange Spray Paint PS-43
      Krylon Stained Glass Aerosol Paint Tangerine Orange K09034000
      DecoArt Glass Stain - Orange GLS04-30

    DecoArt Glass Stain

    Pretty good results in this video, from using just a squeeze bottle...

  9. Oct 20, 2019

    supertrooper Member

    moreno valley, ca
    Nov 12, 2007
    What about 3d printing?
  10. Oct 20, 2019

    Jw60 Recovering Jeepaholic

    Sedalia MO.
    Oct 5, 2018
    I don't think you would be able to get a good transparent part with 3d printing. it would still require finishing on the outside and you would have issues with replicating the inside textures. With a good sample the mold is the way to go.
    Hellion likes this.
  11. Oct 20, 2019

    maurywhurt Member 2020 Sponsor 2019 Sponsor

    Western North...
    Dec 12, 2009
    This video shows a method of reproducing automotive lenses that's pretty involved, requires equipment that not everyone has (including me), and is probably rather expensive - but it is interesting to know that it can be done:

    Here's another video illustrating a similar but simpler process...not sure about the relative quality of the results, but they appear to be good:

    Last edited: Oct 20, 2019
  12. Oct 21, 2019

    Mcruff Earlycj5 Machinist

    Albertville, AL
    Sep 22, 2002
    I build plastic injection molds for a living, 38 years worth of them. Even if I built you a low volume all aluminum tool it would be around $10,000 and molding machine set up would be around $200 and then around $110 an hour afterwards. Lens like that would take about 30 minutes to run around 50-60 of them. Your plastic material would cost around $50-$75 for a 50lb bag. There are prototype shops that might get a mold down to around $4500 that will be good for maybe a 1000 parts at best.

    3d printing it with a resin machine versus a filament would work. All you would then have to do is polish the parts like you do headlights.

    Also as mentioned above there are a lot of people changing the lens color with tinting agents. They seem to work pretty good.

    Oh and the postal Jeep place is about 5 miles from my house, I have bought from them several times over the years, if it’s still owned by the same people there good guys to deal with.
    Last edited: Oct 21, 2019

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