Help me make another attempt at shell casting

Discussion in 'Investment casting Ceramic shell method' started by 01binary, Jul 2, 2018.

  1. DavidF

    DavidF Administrator Staff Member Banner Member

    I get this when I pour into a mold that was pre heated. Pouring into a cold mold gives a much better surface finish especially with aluminum...
     
  2. Zapins

    Zapins Gold

    Interesting. I've never poured into a cold shell before. Will the surface texture be improved with bronze too in a cold shell?
     
  3. DavidF

    DavidF Administrator Staff Member Banner Member

    Ive noticed significantly less fire scale when doing it with brass and bronze with only slight improvement to the surface quality.
    I did side by side testing with aluminum a few years back and even with minimum pre heat of 260C of the mold, the surface finish showed the same crystallization trait 01 just got. When poured cold this defect goes away.
     
  4. Zapins

    Zapins Gold

    I'll definitely have to try that then.

    Very interesting. I've always hated the scale left on my bronze pieces. Anything to get rid of that would be great.

    Any draw backs of pouring a cold shell? Thin parts cast alright?
     
  5. DavidF

    DavidF Administrator Staff Member Banner Member

    There is a trade off when it comes to thin parts. Thats when vacuum assist comes in very handy. But I have cast a 1.5" square only .045" thick repeatably with straight up gravity cast and bottom up fill.
     
    Last edited: Sep 5, 2018
  6. 01binary

    01binary Copper

    This is starting to get really complex :) I will try pouring into one cold shell and one 700F shell and see what happens.
     
  7. DavidF

    DavidF Administrator Staff Member Banner Member

    LOL isn't investment casting "fun" :rolleyes:
     
  8. Zapins

    Zapins Gold

    Good info to know. I look forward to trying cold shells over December when I get back. Until then I'll prep my waxed.

    Binary keep us updated and post a video of you pouring. That's the exciting part!
     
  9. Jason

    Jason Gold

    I wouldn't be in too much of a hurry zap to pour bronze into a cold shell. If ya do, video it for us! I can use a good laugh. I can see a slightly cooler shell working fine. Watch the pros do it and they line up 10 shells before pouring. That takes time and the heat loss has to be pretty big.
     
  10. DavidF

    DavidF Administrator Staff Member Banner Member

    So your saying silicon bronze can not be poured into a cold shell??
     
  11. Jason

    Jason Gold

    I just said video it. You won't catch me trying it. If that shell were to break during the pour for who knows what reason, I think stumpy could end up being someones new name. There is a reason for preheating shells. What it is, I don't care. If it wasn't important, I'm pretty sure we would see the pros not doing it. Monkey see, monkey do is my middle name. ;)
     
  12. DavidF

    DavidF Administrator Staff Member Banner Member

    To my knowledge you have only poured silicon bronze which is probably the easiest of all copper alloys to pour (white bronze being very easy as well).
    Id love to see what happens when you try to cast some yellow brass I think you will see things much differently then...
    Or better yet, try your luck at some cupro :D that stuff can be ignorant!
     
    Jason likes this.
  13. Jason

    Jason Gold

    Yup.. Gold, silver, aluminium and sil bronze. No brass for this guy. Nasty crap.
     
  14. Zapins

    Zapins Gold

    Agree. Try repairing brass without overheating it and inhaling zinc fumes. Pours ok though.
     
  15. That's me!:p Pop cans and window frames!! :eek: I need to get on YouTube. :D

    IMG_3379.JPG

    6" diameter trivets with 1/4"x5/16" spokes.

    And my aluminum hammers

    IMG_3816.JPG

    :rolleyes:
     
    Last edited: Sep 5, 2018
  16. DavidF

    DavidF Administrator Staff Member Banner Member

    Its not that bad, just dont over heat it. There seems to be a pretty fine line between pouring temp and over heated. A small addition of aluminum also seems to cut down on some of the fuming.
    If you dont try the brass at least try the white bronze. Im certain you will love the stuff ;)

    Tig weld it :D
     
  17. Jason

    Jason Gold

    Andy, your trivets look great. It's just with ceramic shell, our expectations are a lot higher than "it filled." We expect near flawless results because it's capable of just that! To give you an idea, I can find my finger prints in my bronze pieces! They were left in the wax and the shell picked them up and turned them into bronze. Yes, the stuff is that good! Binary should be getting much better surface finish. He's just got to dial in the temps.... Hopefully he isn't using window frames.:(
     
  18. When seeing what Binary was making I would assume results with extruded material would actually be acceptable. I could be wrong there, though. He has had a long path and done an exceptional amount of work to get where he's at, and I'm impressed with his tenacity and his results. I truly was not implying that he should be using extrusions.:D

    But, I merely stated, That's Me! I've not progressed far enough that I get better results with known alloys, though I tried a bit, I'm saving them for when I can make sensible use of them.
     
  19. Tobho Mott

    Tobho Mott Gold Banner Member

    +1 for using a real casting alloy at the first sign of any shrink, hot tears, cold shuts, etc. Best thing about using extruded for casting is, it leaves no other choice but to master the use of gating and risers to counteract all manner of casting defects. Once you master (or give up on) that, casting wheelium etc., will be a breeze by comparison.

    Switching from ladderite to wheelium a few months after I got started playing with charcoal and styrofoam was a major lights-turning-on A-HA moment for me. Even my muffin ingots suddenly came out more shiny and with much less shrink on top. Now I am saving my extruded aluminum for... Not sure. Alloying some homebrew 90/10 aluminum bronze to stretch out my C954 for a couple more axes, maybe.

    Jeff
     
  20. Zapins

    Zapins Gold

    I just bought some Al ingots. They went up in price from 1 dollar something per lb to 2.80 a lb. Probably from all the new import tariffs.
     

Share This Page