Sprue a bracelet Help

Discussion in 'Lost wax casting' started by Scv, Dec 26, 2020.

  1. Jason

    Jason Gold

    Head pressure would certainly help. Fatten up the main sprue if you can too.
     
  2. Zapins

    Zapins Gold

    Yes it probably would give more head pressure but may also let it cool longer. I think option 2 is worth a shot first.
     
  3. Scv

    Scv Copper

    With option 2 would I have to worry about trapped air?
     
  4. Zapins

    Zapins Gold

    I always give the air a path to escape through out if habit but I doubt it would cause an issue with trapping in that orientation. Usually vacuum assist sucks out all the air without too much trouble
     
  5. Scv

    Scv Copper

    I don’t think I will ever get it. So this happened. Blew out the bottom of the flask.
     
  6. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Hopefully your casting rig has a basin to contain the spill.....?

    Best,
    K
     
  7. Scv

    Scv Copper

    Yes it has a basin. This is what I’m left with. I pickled it and cleaned it. Do you think I can re use it? CC4D0C0B-FE6A-4E05-97E5-69BCA7A2557B.jpeg
     
  8. Zapins

    Zapins Gold

    Yeah man of course reuse it. Or at the very least post it to me if you don't want it :)

    Make like 3 of them and keep trying. Sometimes it just takes a few tries to get it right. The number of times I've had to recast really complicated sculptures is painful to think about. You're not alone.
     
  9. DavidF

    DavidF Administrator Staff Member Banner Member

    Ahhh, I know that "slurp" sound all to well.
     
  10. Jason

    Jason Gold

    Yes, you can reuse that. There is a casting company in the north east we send the platinum work to. You want the info? You just send them the cad or your wax.
     
  11. Scv

    Scv Copper

    Well I’m tenacious and will probably go to my grave trying to cast this. Her birthday is at the end of the month so I have a couple of weeks. I’m not sure why the flask blew up. I had about 3/4 of an inch of investment on the bottom. It looks like the silver was ejected out of one of the air holes. My biggest problem with this whole project has been timing the burn out to coordinate it with my work. Does anyone know How long I can leave a flask at casting temperature in the kiln?
    Jason please send me there info just incase I reach my breaking point....lol
    Thanks for all the help everyone!
     
  12. DavidF

    DavidF Administrator Staff Member Banner Member

    Forever, as long as it never drops below 500f.
     
  13. jkahn

    jkahn Copper

    Forgive me for jumping in, but, it seems the whole sprue system should be redesigned. You essentially have the metal running down a tunnel (the sprue) and slamming into a wall then asking it to split to the left and right and turn around and climb a hill.
    After of 50 years of casting I have found spruing to be one of the most challenging and important parts of casting. The smoother you can let the metal enter and flow around the piece the more successful the casting will be. This is much more important with vacuum casting and gravity pour as opposed to spin casting..
    If you were to turn the bracelet 90 degrees and create a sprue system so the metal is flowing from one end of the piece to the other I think you would have a little more luck. Generally with this type of casting there is no need for vents, especially with vacuum assist. I would connect my main sprue about 1/3 of the way down the bracelet, on the edge so the metal would flow smoothly in and not hit a wall, then another branch sprue above that to insure the top is fed and finally one last branch about 2/3 down the bracelet, all connected to the edge to help the metal flow easily and allow easy removal.
    I realize metal entering at 3 locations is not ideal but you will have a much better chance of all 3 sprues supplying a smooth flow of metal with less turbulence and hopefully a complete casting.
    I would be happy to make a mockup if you think it would help.
    Happy casting
     
  14. Jason

    Jason Gold

    Yes, running uphill is definitely a problem here. I still havent seen the face of this, but if he flips it over instead of trying to feed the back would work.
     
  15. Scv

    Scv Copper

    Yes please I would appreciate it. I’ve been messing with flask temps too, any ideas on that. Thanks
     
  16. DavidF

    DavidF Administrator Staff Member Banner Member

    This whole problem is temperature.
    Both the mold and melt temps are too low and its freezing before it fills.
    Silver melts at 1750 or so and will appear quite liquid, but will quickly freeze when poured. You need to be at 2000 or 2050 on the metal and 1100 to 1200 on the flask.
    Venting is not necessary when using vacuum assist.
    The end! :p
     
  17. jkahn

    jkahn Copper

    I don't know if this will help, It's only another opinion.
    As was mentioned by DavidF temperature is very important, however not everything. I used to work as a model maker in New York at Karbra Co. one of the largest casting houses in NY. If we were working on waxes, we would hand them to the casting dept. and by the next morning our castings would be on our bench. They would always get a complete cast, but, it might take a few hours to fill all the porosity, as a model, you could ignore the fire scale. I suspect it was high temperatures that caused these problems.
    I have a couple potentiometers I used in my bronze foundry that could tell the metal temp to a couple degrees however I have never been able measure the metal temp in a small jewelry sized crucible, instead I judge temp by jiggling(not technical term) and stirring the metal with a carbon rod, when it feels about like water, I cast. I very seldom get porosity and never get fire scale, probably just lucky.
    For flask temp I go from 900 for pretty thick pieces to about 1150 for things like natural orchids and bumblebee wings.
    Having gone to many casting seminars over the years I learned casting is a bit of an art in itself, not being up on the latest technology, I can't say if that still holds true.
    IMG_1792.jpeg IMG_1795.jpeg IMG_1794.jpeg
     
    DavidF likes this.
  18. Scv

    Scv Copper

    Wow thanks I appreciate it. My last attempt I had a flask temp of 1075. I will up it 1150. I have been heating the silver and stirring with a graphic rod, when there are no more solids I heat it for another min. I’m using 2 mapp gas torches. I thought that I Might be overheating the silver. Do you think I should bump that time up to 2 minutes or more after it’s liquefied?
     
  19. Scv

    Scv Copper

    Also I’m using a 4x5 flask
     
  20. jkahn

    jkahn Copper

    If you’re using sterling silver it should get very thin like water when you stir it with the carbon rod. my website is jeffkahnsculpture.com if you want to look and find my email and or phone number. A phone call might help
     
    Nick Lazenby likes this.

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