Cored casting advice

Discussion in 'Sand Casting' started by DaveZ, Jul 14, 2022.

  1. DaveZ

    DaveZ Copper

    I am attempting to cast this part in aluminum. It is an ambitious undertaking for me as a novice, most of what I've cast so far are flat plaques. This is my first core and split pattern. The part is from a railroad caboose stove, originally cast iron. I copied the original to the best of my ability. The actual part is 10" high, 10" at its widest point, the bottom, and a 5" opening on top. Wall thickness 1/4". My core is epoxy bound sand. Its been a lot of work up to this point and am getting close to pouring, but I'm looking for some advice as to gating, risers etc. Any and all advice is greatly appreciated.
     

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  2. Chazza

    Chazza Silver

    Nice job Dave.

    HRT1 put me onto the US Navy foundry manual; it is absolutely brilliant. Everything that I knew was important in moulding – but that was all I knew – is explained concisely. Read the relevant paragraphs and then read them again. I think I finally have a good idea now, where the best place to put risers is and what size they should be.

    Because it is an online resource, I open it in two tabs so that I can refer to the referenced diagrams, whilst I am reading.

    https://maritime.org/doc/foundry/index.htm

    Happy studying,

    Cheers Charlie
     
  3. DaveZ

    DaveZ Copper

    Thanks Charlie. I do have a copy of the Navy manual. I've read the gating/riser chapter. I guess I was looking for some first hand experience.
     
  4. Chazza

    Chazza Silver

    The trouble is you will get hundreds of different answers, some of them not even related to your question.
     
  5. DaveZ

    DaveZ Copper

    True Charlie, I dove back into the Navy foundry manual like you suggested. Even there, all isn't so crystal clear. They talk about gating small and large castings, what constitutes small and large? Small may be 50 lbs. Who knows. Thanks for your input. I'll just study some more and then go with my best guess. Seems like a lot of this is trial and error anyways.
     
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  6. Chazza

    Chazza Silver

    I couldn't agree more!

    I had an order for a long, thin, car part in aluminium earlier this year; one I had made in the past, which while useable, had small shrinks around internal bosses.

    This time I deleted my "wrong" method of pouring with a very large sprue and small gate and used chills on the bosses. Six-times later, using a pouring-basin, a small sprue and a riser, all I can make is cold-shuts! At least the shrinks have gone.

    I think a larger sprue might help – very frustrating. The Navy manual, I think, has some answers.
     
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  7. Melterskelter

    Melterskelter Gold Banner Member

    The Navy Manual is a superb resource, agreed. But it will not likely have information that clearly speaks to this part. You asked for an opinion. So, here goes realizing that my opinion is a best guess.

    First, since this is a rather thin-walled casting throughout, risers probably will not be needed.

    I guess, I would try gating it so metal flows into the lowest point and fills upward. So gate left and right on the large end at the parting line. I think I would tilt the mold small end up as much as was practical given my mold depth. A deeper than ordinary cope might allow for more tilting.

    Then I would just give it a try and see how it went. Based on that, make subsequent adjustments. Chances of this method working perfectly on the first try? Maybe 10%. And yes, there may be a fairly wide spread of ideas offered here. That's OK. The OP can read them, the reasoning behind them , and then go the direction that makes them most sense to him. I guess that is the way most of us decide how to proceed.

    Denis
     
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  8. DaveZ

    DaveZ Copper

    Thanks Denis, sounds like a good starting point. I appreciate your input.
     
  9. Melterskelter

    Melterskelter Gold Banner Member

    By the way, that was some nice lathe work and an excellent looking pattern. Was this the classic paper glued between two halves of the glued-up block, turned, and then split using a chisel on the paper seam method? My only suggestions would be to apply a glossy slick finish to make the pattern slip out of the sand better and then wax it with a floor wax like Johnson's or Minwax and then hand rub graphite onto it.

    Denis
     
  10. Melterskelter

    Melterskelter Gold Banner Member

    And another thing ;-)

    If you oriented the mold part line vertically, you could gate into the flange on the large end. To be clear, I am suggesting ramming the mold conventionally and then rotating it 90 deg along it long axis. That would allow filling from the bottom up without tilting the flask. I'd be very tempted to try that on this particular mold as that would allow a nice organized fill from the lowest point up.

    Just use screws or clamps to close the mold. I would simply put cleats along the lips of the cope and drag and screw from cope to drag to securely close the mold. I'd also use a piece of plywood screwed to the bottom of the drag and top of the cope prior to turning it onto its side for pouring. The cope and drag would have to have a window centered on the part line that could be removed to allow cutting a pouring basin and making the pour. A bit unconventional---yes. But a method that seems suited to the situation. Using a nice curving sprue as FishbonzWV did a while back might be a good idea here. He made his from a piece of heavy guage wire. Soft copper tubing carefully annealed and bent might make a nice curving sprue as well.

    https://forums.thehomefoundry.org/index.php?threads/exp-styrofoam-followers.1254/

    Denis
     
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  11. DaveZ

    DaveZ Copper

     
  12. DaveZ

    DaveZ Copper

    Thanks Denis, yes that's how I did that. Actually there was more hand work than lathe work. The top where its concentric I completed on the lathe and only minimal shaping could be done on the lathe to the rest of it due to its oval shape. Lots of hand work. Using contour gauges, large calipers and lots of sanding.
     
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  13. Tops

    Tops Silver Banner Member

    Agreed, nice work on the patterns. Will we get to see the caboose and stove?
     
  14. DaveZ

    DaveZ Copper

    Thanks. Yes I'll be sure and post a picture.
     
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  15. DaveZ

    DaveZ Copper

    I considered that Denis, because I had read Fishbonz post about the vertical pour. It does look as though that would work. But I think I'm going ahead with the horizontal pour. I spent time today on the runners and gates. If I have issues that I can't resolve then vertical is certainly a viable option that I will try. Also your tip about using wax I've used in the past, but I've yet to use graphite. I know Ht1 promotes using it and I'm going to ad it to the "tool box". Thanks again.
     
  16. DaveZ

    DaveZ Copper

    Finally got around to trying to pour this part. Life has a habit of getting in the way. I was bummed out, ran out of metal. What came out looks great. Will give it another shot. 20220910_131903_HDR.jpg 20220910_131652.jpg
     
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  17. Tops

    Tops Silver Banner Member

    So far so really good, too bad you ran out of juice. Do you have enough crucible to support the extra metal needed to complete the whole part?
     
  18. DaveZ

    DaveZ Copper

    Thanks. Yes I do just need to make a lifter for the crucible.
     

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