Need Advice on Mold Making and Casting

Discussion in 'General Modeling' started by 1zzy, Aug 16, 2005.

  1. 1zzy

    1zzy New Member

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    So I have finally ventured into the world of scratch building and made a small sculpture out of sculpy. I baked it already and now am ready to make copies of it. I have a couple problems to work out first before I can do that though:

    1) How to Make a 2 Part Mold - My sculpture is a helmet for a 12" figure. If it was a sealed helmet it wouldn't be an issue, but the helmet will be wearable by a doll, so I need to figure out how to make a mold of it. Never made a mold of anything in my life. Is there a link to a how to?

    2) Orientation - Since the helmet is open, I am assuming that I will have to do a 2 part silcone mold, but I am unsure how to orient the piece to get a proper pull and make it so the mold doesn't get destroyed. I am not looking to get a ton of pulls from it, but would like to get more than 4 if possible. There are a few negative angles, but I assume that a silicone mold will flex enough to let the pieces out.

    3) Mold / Resin Material - Not sure what would be the best material to use. Is there one that someone could recommend to me for a small run? What is a good resin to get as well for something that I want to be able to be played with?

    If anyone can help me out I would be very thankful.

    Scott S.
     
  2. gladus63

    gladus63 Active Member

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    Silicon is the best for the mold and polyester resin should be good for the casting,
    hope this will help you

    Cédric


     
  3. BB43MAN

    BB43MAN Well-Known Member

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    :) Try looking at the Polytek line of casting rtv's and resins. They cost a little more (what doesn't with oil prices the way they are) but, they are worth it. You can get some rtv's with a higher tear strength so you can work more with undercuts, if they are not too much of a negative space.
     
  4. cobywan

    cobywan Sr Member

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    I try to make sure that the cavity fills from the bottom to the top somehow. The "right" way to define your part line is to imbed your pattern in "clean" clay abd sculpt it where you want your mold line. I would imagine right along the lip of the helmet would be best. Make sure to press dimples into the clay to make alignment work easy.

    After the first half sets clean off the clay and put some sort of release agent on the mold mating surface and pour the other half.

    There should be a site or two that illustrate the process for you though.
     
  5. 1zzy

    1zzy New Member

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    Thanks all. Now I just have to get some to play with and see what happens. I was thinking along the lip of the helmet but I will see I guess. BTW - Here is what I am trying to cast - http://scott.the-strongs.net/show_portfolio.asp?ID=58
     
  6. cobywan

    cobywan Sr Member

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  7. badger

    badger Well-Known Member

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  8. 1zzy

    1zzy New Member

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    Cool. So in looking at my images, do you think I would need to do a 3 part mold? If someone could give me an idea of where to divide the mold up along with orientation of the piece I would greatly appreciate it.

    Right this second I am thinking the dividing lines would be along the sides and over the top for the two halves with another dividing line along the bottom edge of the helmet. That way, the helmet can be hollow and the third mold pour will fill in the helmet with silicone. I am thinking that the pour hole can be at the top (although it would have to be small so as to not detract from the pulled pieces. I don't think I need vent holes, but I would like someone with more experience to guide me if they can. :)
     
  9. cobywan

    cobywan Sr Member

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    I see no reason at all to have a mold split across the outside of the helmet. Just make the parting line along the bottom of you helm. You could even get away with "squash molding. You just pour some resin into the top half of the mold and press the bottom into it and the excess will be squashed right out.
     
  10. punisher

    punisher Sr Member

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    for a really cheap (and HIGH QUALITY) resin and silicone kit. go to smooth-on.com ill post a more specific link later. but you need to get the silicone starter kit,its around $24 and is actually $45 worth of materials but its a one time offer so... get it now. with casting small items, it should last a long time.
     
  11. BarryZ28

    BarryZ28 Well-Known Member

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    DonÂ’t you hate it when you find a great tutorial on just this subject and you can never find it again?
    ThatÂ’s my problem, even when you bookmark it you still seem to lose it.
    Well I just copy it into Word and save it as a word document and Viola, I have it in a location where I can always find it.
    IÂ’ve learned to do this with sites that I know I can make use of sooner or later.
    Please note that I am not taking credit for writing or creating such tutorials.
    If I pass on any material that belongs to others, please realize that originators of these materials deserve all the credit for said tutorials.

    Having said that, I have a great tutorial that may help you, it's saved in “Word” format.
    If you want the tutorial please email me and I will forward it on to you.

    Thanks Barry.
     
  12. Trallis

    Trallis Well-Known Member

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    while this thread is here.. i figured id ask a simple question.
    what resin from smooth on is best for small(1 square inch) to medium sized parts and high detail.
    and whats the most populat silicone?
     
  13. cobywan

    cobywan Sr Member

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    Smoothcast 300 for general use. Moldmax 30 for general use.

    I have been using SC305 for the extra time to allow bubbles to move out of my castings. And I personally like Moldmax 40.
     
  14. clonesix

    clonesix Sr Member

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    If I can add a nickel's worth of free advice here: It is always good to have a picture to see what is being discussed. Can you post a pic of what you want to mold?

    This is a doll helmet? GI Joe size?

    I think you ought to be able to do this in one piece silicone mold. Mount the helmet to a flat surface at the bottom (neckline) Surround the part with a box or plastic drinking cup. fill with silicone RTV.

    Pour a small amount of resin into the finished mold and rotate it to cover the interior walls. Keep rotating until the resin sets. You will have a hollow helmet.

    If the helmet is more complicated, please post pic for reference.
     
  15. badger

    badger Well-Known Member

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    do you use a fast set resin for that? the resin I got with my kit sets in 30-40 minutes.

    I assume yours must set faster than that.
     
  16. clonesix

    clonesix Sr Member

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    Yes, I use resin that sets in 3 minutes.

    For the purpose described above, a doll's helmet, theres no reason to use anything more.

    I also use the 3 minute resin in my 1:1 helmets without any problem.
     
  17. 1zzy

    1zzy New Member

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    Look at the link - http://scott.the-strongs.net/show_portfolio.asp?ID=58
     
  18. 1zzy

    1zzy New Member

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    So the negative cuts in the cheeks won't be a major issue. Also where is the link to the kit I should get from smooth-on? Thanks all.
     
  19. 1zzy

    1zzy New Member

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    Is this the kit - http://www.smooth-on.com/Getting%20Started.asp:
    Silicone SuperSampler™
    Each Silicone SuperSampler™ contains working samples of OOMOO™ 30 silicone mold rubber and Smooth-Cast™ 300 liquid plastic, Ease Release™ 815 release agent for silicone, SuperSeal™ , and the "How to Make Molds & Castings" booklet.
    $25.00

    How much material do you get in it (ie. a pint of each bottle)? Just wondering if it is a good deal or if I should just get a pint of Smooth-Cast 300 and Mold Max 30.
     
  20. saberlover

    saberlover Well-Known Member

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    I just got this kit in the mail today... IT IS WORTH IT.......lol. I was expecting something smaller... There is a lot of material to play with. I reccommend it. You even get two small little sample pieces to show the quality of the finished materials...
     
  21. 1zzy

    1zzy New Member

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    There is sample pieces in the box? I didn't even get that far yet. Pulled out the instructions and the mold liquid and already started poured the first half of my mold. Interesting that the Part A is Pink and the Part B is blue. Also interesting that Part A is really thick and sorta sticky and Part B flows like water. Guess tomorrow morning I will get to see how the first part turned out and flip it over for the second half.

    Have to see what pieces I got in my box....
     
  22. 1zzy

    1zzy New Member

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    Finally got everything done and started casting helmets. Thanks all for your help. Here is a recent pic...
    [​IMG]

    BTW - if anyone wants one or a set PM me.
     
  23. 1zzy

    1zzy New Member

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    Made the helmets more like the game:

    [​IMG] [​IMG]
    [​IMG] [​IMG]

    Did the guns too (click for bigger view):

    [​IMG]

    [​IMG]
     

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