Joining parts to existing cast

Discussion in 'Lost foam casting' started by Nick Lazenby, Dec 15, 2020.

  1. Nick Lazenby

    Nick Lazenby Copper

    (Apologize for the terrible title)

    Has Anyone attempted (or know the proper term for) casting a piece that’s already attached to an existing metal piece?

    I have a sculpture that was an incomplete cast and I was wondering if I could install some anchor points and/or holes and a fix a piece of foam so that the newly poured metal bonds adequately with the previously cast piece.

    i’m also thinking of applications for multi metal pieces. Any thoughts or ideas around this topic would be greatly appreciated!
     
  2. DavidF

    DavidF Administrator Staff Member Banner Member

    It typically does not stick together...
    Your best bet is to cast a repair section then weld or braze it together.
     
  3. rocco

    rocco Silver

    I'm pretty sure David is right, I've only attempted to pour molten metal on to solid metal once and it didn't bond at all. If you don't want to weld your sculpture and don't mind a visible seam, maybe try cutting something like a dovetail shape into your cast piece so that that the new metal has something to key into and hopefully that will create a solid mechanical connection.
     
  4. Tobho Mott

    Tobho Mott Gold Banner Member

    It won't likely bond as perfectly as a brazed joint and there would probably a visible seam and it's not really the "right" way to do it, but depending on the situation and how solidly you need the parts attached, you might get away a joint that is only anchored mechanically in a pinch.

    I lost foam cast an aluminum plug into one end of a piece of exhaust tubing using a method similar to what was suggested when I built one of my oil burners. (Posts with pictures and video starting here: http://forums.thehomefoundry.org/index.php?threads/larger-moya.780/page-3#post-17707 )

    I drilled some holes through the tubing at the end where the foam was and filled the holes with hot glue (which in thin layers will also burn out and fill with metal like styrofoam) to give the metal a place to lock into. I haven't really tried very hard to make it loosen, but the end is plugged very tightly with aluminum and it certainly would be a chore to remove the plug or get it to wiggle a bit. I don't think it's all because of the holes allowing the aluminum to lock in there, but I would certainly drill them again just to be safe if I had to do it all over again. It only has to support the weight of the end of the oil line when being used as intended.

    As it happens, this came across my feed earlier today as well. This guy had issues with sand float and ended up doing more cutting and grinding than I would be happy witho_O, but he did get the two pieces stuck together in a way that seemed solid enough:



    YMMV

    Jeff
     
  5. Nick Lazenby

    Nick Lazenby Copper

    That's exactly what I was looking for Jeff! I figured if I had enough "anchors" or areas for the metal to grab the piece it would stay. Not super concerned with any joining lines.

    I have some metal pins w/t some branches welded on. Was planning on tapping them directly into the piece, while also boring some open holes for metal to flow into. Then I was going to gently heat the piece just enough so that the foam molds around the piece when I press down on it.

    Prototype 3.3.jpg


    Lots of potential ideas around mixed alloy pieces - so many plans, so little time ha
     
  6. rocco

    rocco Silver

    I can envision some pretty cool looking effects with contrasting metals, if this works for you, it certainly would open up some interesting opinions.
     
  7. Nick Lazenby

    Nick Lazenby Copper

    I found some discarded mosaic tiles in the trash that should make for a good proof of concept around this. The metals will be poured directly onto the tile in three pours, with sand borders to keep everything in place.

    Prototype 4.2.jpg
     
  8. HT1

    HT1 Gold Banner Member

    What Jeff is describing is called Intercasting , I have done it to Make dive Knives take a stainless blank with a hidden Tang drill holes entirely through the tang you make a pattern for the desired handle ram up the knife blank and the pattern in the mold,

    the Knife blank is basically a core that will remain in place, the molten metal pours through the holes in the Tang mechanically locking it together , you can then finish off the knife

    there are other artistic aplications something like the Epoxy pencil tables. but molten metal is the epoxy , there has to be a significant difference in the two metals melting point, the non-molten part has to well cleaned, preheating and casting while it is still hot helps, different contraction rates are involved in how tight joints are, it is very much an art, not a science


    V/r HT1
     
    Nick Lazenby likes this.
  9. rocco

    rocco Silver

    Judging by what he's shown us, that's seems like it'd be right in his wheelhouse.
     
    Nick Lazenby likes this.

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