Using Silicone Molds to Make EPS Patterns For Lost Foam

Discussion in 'Pattern making' started by rightbug, Sep 5, 2019.

  1. rightbug

    rightbug Copper

    Thanks for all of the feedback everyone! Lots of great stuff to digest and incorporate into my next pour. I'm away next weekend so I've got two weeks to prepare!
  2. rightbug

    rightbug Copper

    Okay, I've been super busy so there was a delay but the second and third pours went perfectly! Thanks for everyone's advice.

    I got rid of the pouring basin but kept the riser, just in case of shrinkage. I also used the soup can over the sprue.


    I put a half handle in the form for these later patterns but I still had to keep the other side open to let steam into the mold.

    Here's the first hammer straight out of the sand...


    And after initial cleanup:


    And here are some shots of the finished hammer:




    And here's one final shot showing the stages of development:


    Thanks again for everyone's guidance. I'm looking forward to my next casting project!
    BattyZ, Al2O3, Tobho Mott and 2 others like this.
  3. Al2O3

    Al2O3 Administrator Staff Member

    Great result. Well done rightbug.

  4. PatJ

    PatJ Silver

    Those turned out quite nicely.

  5. Jason

    Jason Gold

    Looks great. When do I get one?:D
  6. Tobho Mott

    Tobho Mott Gold Banner Member

    That is super cool!

  7. Sparkproof bronze hammers aren't exactly cheap either, there may be a niche market for the oil and gas fields. That could be easily made into an (ahem) "Tobacco Pipe" with a hollow handle and casting that would be an innocuous object :rolleyes:.
  8. Tobho Mott

    Tobho Mott Gold Banner Member

    "Tobacco" has been legal up here for just about a week short of a year now, and nobody seems to be trying to be innocuous about using it anymore.

    This is on the front door of a nearby federal government office building:


    However, I still haven't even tried to sell one of the aluminum bronze pipe tomahawks I made a pattern for last year.

    I'll leave it for you guys to speculate about why I have been so lazy. :D

    Really though, I've just been too busy with the day job, family, etc, honest...

    (Proof: I haven't even drilled out a smoking handle for my own pipe hawk yet either.)

    Hope I/we haven't derailed the thread with this. We should be focused on the fact that a home hobbyist has finally succeeded in creating their own styrofoam patterns for lost foam casting! Without having to carve them, that is. We haven't ever seen any other home gamer manage to get it working before now, I don't think, though IIRC one or two have tried and failed. Truly amazing!

  9. I'll have to get the rest of the foundry set up before I see if I can get some beads from a local polystyrene manufacturer, but it is a very interesting process. I think I mentioned before that my Toyota light truck has an aluminium intake manifold with a pronounced styrofoam texture.
    dennis and Jason like this.
  10. Tobho Mott

    Tobho Mott Gold Banner Member

    Just ran across a different video showing more monkey business using pre-expanded polystyrene beads, although these molds aren't silicone. Looks like fun:

  11. rocco

    rocco Silver

    That looks like a very stout mold which makes me wonder how much pressure it needs to be able to withstand and if silicone would be up to the job.
  12. mytwhyt

    mytwhyt Silver

    That first mold [pink]does look like one of the softer silicone rubbers.. May be something like this epoxy resin would be better..
    EpoxAcast® 670 HT High Temp Castable Epoxy from Reynolds Advanced Materials ( Looking to make a plaque about 6.5"x6.5"x1/2"out of foam of aluminum casting.. Want an easy alternative to lost wax casting.. Flat 1/8" plate of aluminum for both side to clamp on.. Back plate as bottom.. It's high temp resin so boiling water to expand the beads wont effect it.
    Last edited: Oct 30, 2021
  13. mytwhyt

    mytwhyt Silver

    Well I was impressed enough I spent 18$ on a 10 oz condiment bottle with 8 oz of expandable pellets.. I think my mold for wax will take the heat.. It's a hard urethane.. If not, I'll move on to the epoxy I linked.. If I can make a eps part to cast I'll give up 0n the wax... Up until now I was thinking I'd need to cast an aluminum mold to do eps parts..
  14. Al2O3

    Al2O3 Administrator Staff Member

    Remind me, what part are you wanting to cast?

  15. DavidF

    DavidF Administrator Staff Member Banner Member

    Where did you get them from??
    I've been wanting to try them for some time now.
  16. Smoking Shoe

    Smoking Shoe Silver

    Yes, and please let us know how they work out. I just ordered a bunch of small bean bag pellets last night, but for a different casting project. I don't know if they will expand or not. A lot of the material sold for bean bags is just old stock that will no longer 'pop' due to loss of expanding agent during long storage.

    My first attempt at applying Halliburton light cement methods for low density IFB indicated a need for a different 'witches brew' or ........ a completely different path. Small un-expanded Styrofoam beads may be another path.

    My driving reason for getting back into casting is the need for some castings that are best done with lost wax or better, lost foam. I don't, yet, have any way of making the detailed/complex foam for lost foam. AL2O3's* methods, as good as they are, would be far too time consuming compared to lost wax.

    * Does this software automatically subscript text it thinks is a chemical formula?
    C2H5OH Looks like it does.
  17. mytwhyt

    mytwhyt Silver

    I got it on eBay, Long time seller,100% rating, it was the last one.. I know the stuff has a shelf life, and this one being the last, it could have aged badly.. It was the only one I could find, so I took that chance.. The product relates to other things like making floating lures, I'm thinking they may restock if there are inquires... Maybe if a few members are interested and asked about it.. oahetackle on eBay
  18. mytwhyt

    mytwhyt Silver

  19. Al2O3

    Al2O3 Administrator Staff Member

    What's the approximate density of the bonded perlite shown? The link says the perlite itself can be 2-15lb/ft3 which is quite a range but also low density. 1260c/2300F melting point so service temp will be considerably below that. 2300F is typical service temp of most common ceramic fiber. Ceramic wool is typically 6-8lbs/ft3. Just wondering how the density increased with the addition of SS.......but, I like it for a low mass low/moderate refractory level insulating structure.

  20. Smoking Shoe

    Smoking Shoe Silver

    Actually the other way around. I plan to use brick to support my heating coils with the blanket as the backup for insulation. Low mass is my goal.

    I bought enough perlite thinking it would work to make light weight brick but after more study I've come to the conclusion it's melting point is too low.
    Some of the patents I've read for making IFB do use perlite but the density/particle size looks to be critical to keep the service temp of the resulting brick high.

    If my DIY attempts to make light weight IFB fail I'll probably punt and just carve commercial IFB or do like AL2O3 did for his.

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