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    [HELP] Making molds?

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    I'm planning on building a Thomas helmet in the end of year holidays, and so far I'm pretty sure I've got everything planned out except the molding/casting part. I've been researching a lot but I still find it hard to understand and would like some help with it.
    What I've got so far:


    1. Glue helmet to a base.
    2. Apply silicone rubber thingamabobs.
      How many layers? How to put alignment pieces?
    3. Put clay to separate helmet into 2 halfs?
      REALLY don't understand what this part does.
    4. Apply some sort of hardener over it and screw in holes?
      What hardener?
    5. After everything cures, cut the bottom.
    6. Unscrew, remove "master" mold/cast(?).
    7. Screw it back in, and fill in with liquid plastic.
    8. Slush around for 3 minutes, repeat until desired thickness is reached.
    9. Take it out.


    Is this all?

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    Re: [HELP] Making molds?

    Volpin does a great job of covering the steps here

    The video at the bottom of step 8 is great for the silicone. Make sure you have maybe four cheapo brushes and multiple cups to mix and brush materials for later. The clay is a divider so that you can mold one half of the shell at a time. Most people use fiberglass or a plasticpaste shell. The drill holes are so you can put bolts with wing nuts through them to secure the shell for casting. Once everything is cured, you can remove the shell, the silicone, and then the master sculpt (what you have now). Put the silicone back in shell and press the rubber back into the keys you made earlier in the brush on stage (those hemispherical pucks that volpin puts in his instructable).

    Really if you follow Harrison's instructable word for word, you should get all the info you need. Also he makes his silicone mold in two parts, but it isn't entirely necessary. Good luck!

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    Re: [HELP] Making molds?

    Thanks for the quick and helpful reply! But I have a few questions to Volpins instructable. In step nine, he puts three dividers even though he said it's going to be a two part mold, and then later he breaks it into three different pieces and then theres an image of a two part mold? I don't understand.

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    Re: [HELP] Making molds?

    Talk about good timing, I just put together a photo set of my last Thomas mold a few weeks ago. If you have any questions, just ask.

    http://www.flickr.com/photos/leprops...7635404510738/
    For the latest updates on my props, visit my Page on Facebook!

    http://www.facebook.com/L.E.Props

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    Re: [HELP] Making molds?

    The nomenclature can get tricky here. The mold is 2 part; that's referring to the silicone, which is the soft rubber we all use in making our molds. The 3 part piece you're looking at is called a "jacket" or "mother mold" - this holds the silicone in shape because without it, it would just flop over like a wet noodle. The reason the mold jacket may be 3, 4, or many more parts all depends on how you're planning on removing it from the soft silicone mold. I have some 2 piece molds with 6 part jackets.

    As to your other questions:

    (silicone) How many layers? How to put alignment pieces? - silicone should be at least 1/4" thick. Thicker molds will generally hold up through more uses, so if you're doing a larger run then you'd want somethting like 3/8"

    Put clay to separate helmet into 2 halfs? REALLY don't understand what this part does. - Namely, it makes the cured plastic helmet easier to remove from the soft rubber mold. With a front and back half, the rubber can be peeled away in sections. Without this you'd have to try to pull the whole helmet out of the hole at the neck area, which is probably too small an opening.

    Apply some sort of hardener over it and screw in holes? What hardener? - this is the mother mold, I generally use Smooth-On's Plasti Paste, though plaster, fiberglass, and many other materials will also work.

    "master" mold/cast(?). - yes, the piece you're molding is generally referred to as the "master" or "sculpt" - The rubber and jacket thing is the "mold" and the things that come out of it are "castings"

    Slush around for 3 minutes, repeat until desired thickness is reached. - careful here, many resins take longer to cure. Also, subsequent coats will cure faster due to the build up of heat. Small batches are best when you're first starting off, like 1/2-3/4 cup of mixed resin at a time. As you get more used to it you can step up to larger batches.

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    Re: [HELP] Making molds?

    Hi all,
    Could somebody clarify what keeps the second half of the mold from sticking to the first when you remove the clay. Wouldn't the rebound 25 bind to the first half of the mold and make it impossible to remove?

    http://www.flickr.com/photos/leprops...57635404510738

    Above is the step I'm referring to in RAMs photos. Do you apply ease release or something else between the two parts?

    Also good job RAM and Volpin your work is top notch!

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    Re: [HELP] Making molds?

    They add some sort of release wax that will stop the silicon from sticking together.

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    Re: [HELP] Making molds?

    Thats good to know. Now that you say that I see it on Volpins supply list in his instructable.

    I'm making my mold tomorrow and gonna try this method.

    http://www.oreillyauto.com/site/c/de...rd=release+wax

    Would something like this be safe to use?

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    Re: [HELP] Making molds?

    I was thinking to use the same thing, since this is the only one that I found in New Zealand, I would like to also hear if it can be used.

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    Re: [HELP] Making molds?

    Make sure you don't make your mold too thick. I am making a thomas mold right now as well . here are some pics that I took.


    but this is my first ever thomas mold, but I've made a couple of guyman molds before.
    I don't think there is a big difference when we are talking about thickness.
    My first mold for guy was really thick. I think it was about 3/4 inch- 1 inch thick which is very thick considering what Volpin said. I've made around 18 casts out of it and then it fell and the jacket mold broke and I did not want to remake the it because it literally took me and my friend together to get one helmet out of the mold! Silicone was way too thick!
    Next I've made a guy mold that was about 1/2 inch thick and it worked much much much butter and I've made around 68 helmets out of it, however I should say after helmet #55 I had to do some work on the helmets because of dents here and there. I've made my third guyman mold just recently and I didn't even cast 10 helmets out of it but it works just fine and it is around 7/16 inch thick.
    The only problem is that it is very hard to tell how thick the mold is, if there are any tips then please share, it would be nice to know.
    Today I am finishing the back part of the thomas mold and starting on the front tomorrow... hopefully it will turn out good

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