Lost Foam Sprue Tree Techniques

Discussion in 'Lost foam casting' started by Chassy, Dec 2, 2022.

  1. Chassy

    Chassy Copper

    Can anyone recommend resources for best practices in creating a lost foam sprue tree? Or are these no different from doing that for a lost wax process? I really haven't found anything across these forums, YouTube or the internet in general. I keep going down a mental rabbit hole of thinking about optimizing flow rates down branches, sand collapse, and cooling before the molten aluminum fully replaces the foam.

    This comes from having taken my furnace and other equipment out to a couple of events where I was letting people create their own little patterns, which I then cast later in the day. Last time around, it was overwhelmingly popular and I found myself having to do dozens and dozens of little pours for individually sprued parts - 7-8 items in a single 3 gallon bucket of sand. If I'm going to do this again, I need to make that part of the process a little easier for myself, and I think that treeing things together will help. I'm also planning on casting some trinkets as holiday gifts, and I think that working with a sprue tree rather than lots of small items will be the best approach. It seems to be the preferred method for jewelers, and I've seen Al203 post some impressive pictures of their sprue trees here.

    315101357_816836452915481_1435004049233728999_n (2).jpeg
     
  2. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    That's a pretty broad question, sort of like asking: "Can you fellas recommend how to arrange a sprue, runner, and gate system system for multiples of anything?"

    In lost foam casting, the lines between what's a gate and what's a runner can blur a bit, but If I was to try and generalize, I'd probably say to keep the sum of the crossectional areas that feed the plurality of parts comparable to the cross section of the sprue, and attach them on the tree oriented so as to avoid blind overhangs that sand wouldn't naturally gravity flow into (like you would any single LF casting).

    Leaving enough room to brush coating on or making them strong enough to withstand the buoyant forces of dip coating as well as ease of degating the casting would also be considerations.

    I was going to point you at a few of them but if you've already seen them......

    Here's one example with a 32-on tree. If you scroll back up the thread you'll find more examples of larger 8-on, 4-on, and 2-on.

    http://forums.thehomefoundry.org/index.php?threads/two-barrel-carburetor.947/page-5#post-23727

    Best,
    Kelly
     
  3. Chassy

    Chassy Copper

    Thanks for humoring my broad question :) I think one of my earlier mistakes was making my runners horizontal (and also keeping them the same size as my sprue), whereas I see you're keeping everything at a downward angle. I think it will be a while before I have the confidence to possibly ruin 32 items in one pour, but I'm feeling better about my next try.
     

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