Lost Wax Casting Failure

Discussion in 'Lost wax casting' started by IvanAlmighty, Nov 15, 2019.

  1. DavidF

    DavidF Administrator Staff Member Banner Member

    Plasticast is designed to stand up lost plastic casting although there are some limits as to what can be done.

    See post 5 where I told him to bury a shrink bob in the center of the mold.
    No it's not that difficult...
     
  2. IvanAlmighty

    IvanAlmighty Copper

    Ahh, the model itself is wax but the sprue attached to it is made out of pla. I've actually been looking at a couple models of resin printers recently, from what I understand they burn into vapor pretty cleanly? If I pull the trigger on one I'll poke you for your cycle recipes!

    Oh yea, I got those steps down and I've been pouring solid blocks of tanks minus the barrel/soldier. Thanks for the warning about the danger, I actually had that happen when I popped it open just once before and then flames spawned almost instantly!! If I could eliminate most of the wax prior to the kiln that'd be amazing, I'll dig into some steam dewax methods, I think I saw you or someone else mention this on here or AA while digging through old topics. Thanks for the suggestion! I'm loving the journey so far
     
  3. IvanAlmighty

    IvanAlmighty Copper

    I'll scour craigslist/ebay for a bigger kiln since the current one's height might keep me from proper procedure like this. Just to make sure I understand from your vid, a shrink bob would be sort of like this? Although with way more length on the shaft between the pouring basin/shrinkbob
    [​IMG]
     
  4. DavidF

    DavidF Administrator Staff Member Banner Member

    Shrink bob closer to the part as close as you can get and still be able to cut it off with just a small vent. J sprue into bottom of part, a 3/8" sprue is plenty.
    But if your using vacuum assist thow the j sprue out entirely. The j sprue was just to help get the mold to fill without vacuum assist.
    Yes it can help flush out the mold as it fills, but has very little improvement with vacuum assisted castings.
    Also forget the bi film theory for now.

    Screenshot_20191230-223114_Gallery.jpg
     
  5. IvanAlmighty

    IvanAlmighty Copper

    Ahhh thanks for clarification, I'll keep moving forward once the new flask/pipe arrive and scrap those sprue plans.

    If not some bi film stuff, I certainly hope the pitting was just due to my hairbrained attempt..
     
  6. DavidF

    DavidF Administrator Staff Member Banner Member

    LOL Pretty sure that you pulled the air out of the investment and right into the metals surface... Would have been better if you pressurized the chamber the way you did it....
     
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  7. IvanAlmighty

    IvanAlmighty Copper

    lolol yeah actually that makes way more sense
     
  8. Jason

    Jason Gold

    You do have an ally in your corner. It's called solid investment! Invert you flask and take it to about 200f sitting above a shallow pan with water in it. The bulk of the wax will slowly drain out and collect in your water pan. After it quits draining, remove the pan of water and crank the temp up and burn the rest out. Us ceramic shell guys dont have this luxury, the wax expansion would blow the shell apart.

    You could dewax vertically in a kitchen oven. (it's only 200 f ) When you burnout, turn the flask sideways if you have to so it will fit in your kiln. No reason for a big kiln if your flask fits in what you have.
     
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  9. IvanAlmighty

    IvanAlmighty Copper

    oh, giddyup! :D
     
  10. IvanAlmighty

    IvanAlmighty Copper

    Still chipping away on this, these pics are from a couple weeks ago and I’m prepping some more revsions but I figured id toss this up anyhow in case you guys catch something.

    Made a more proper vacuum chamber to rest the flask in and it yielded better results, but I’m still gonna need a new pipe to sit the flask in. This pipe was JUST barely enough room for the flask to drop in to, and after it was heated in the kiln, the metal expanded to be nearly too thick for it (had to basically jam it in). I got alright results the first run but I couldn’t rest it flush the second time and I paid for it later

    Got a bit of deionized water and a better seal for my investment vacuum, so I’m gonna give it another go soon! I’ve been getting a small bit of pits on some areas and I’m not sure what’s causing it, I was gonna try Phosphor Copper to degas but sounds like Everdur doesn’t need it. Also might try lowering the flask temperature down from 288C to 240C, I think someone mentioned that helps with surface quality..

    Lemme know what I’m messing up here!
     

    Attached Files:

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  11. Zapins

    Zapins Gold

    Much better. If you had a tig welder you could make it perfect. Or just keep casting for 100% defect free
     
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  12. Jason

    Jason Gold

    Looking good! You dont need to add anything to your everdur except melt it in the right environment. If in doubt, go rich and pour around 1900 for your lump there.
     
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  13. IvanAlmighty

    IvanAlmighty Copper

    Long time no see!

    Back on this again; got a proper pyrometer and I think the temperature made all the difference with pitting that appeared all around the previous castings.

    One of the main issues bugging me now are the various tiny bubbles clinging to the surface of the wax when I vacuum the investment; I was curious if there's something I could do to the surface of the wax to reduce the chance of bubbles sticking to it? The other issue is (what I assume) debris pooling towards the bottom on the right side where the metal first hits; I was wondering if that was investment left in the flask that I could suck out or if that's just crud from the metal?
    image0wwe.jpg.jpg image1 (1).jpg
     
  14. rocco

    rocco Silver

    To eliminate bubbles, Kelly sprays a little soapy water on his foamies before he coats them, that might work for this application too.
     
  15. amber foundry

    amber foundry Copper

    Did you degrease the wax before investing ?
     
  16. IvanAlmighty

    IvanAlmighty Copper

    I'll give that a shot, thanks!
     
  17. IvanAlmighty

    IvanAlmighty Copper

    I haven't heard of that process before, could you share? 'Preciate it :D
     
  18. amber foundry

    amber foundry Copper

    Before investing or shelling you should degrease with isopropyl alcohol or similar, I often use use methylated spirits. Just a quick mist and work into fine detail with a soft brush. I believe it breaks down surface tension. I've never tried soapy water but I guess that might also work. I actually have a product from Remet in aerosol form for use before shelling but haven't used it enough to gauge its usefulness.
    Do you vacuum the investment before you pour around the wax or vacuum the wax within the investment?
     
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  19. Jason

    Jason Gold

    For shell, I don't do anything to the wax before the first dip. I send it for a dip, and very gently mist it with a light stream of compressed air. No vacuuming, no "wetting"... nothing!
    The air pops any bubbles from the dip and gently pushes the excess slurry off the wax.

    For solid block, vacuuming the just mixed investment is a must. After pouring slowly down the side and not just dumping it in, vac it again.
    Dumb question here... You are using distilled water right??? Everyone's tap water is different, so don't take any chances, use distilled water per the instructions.;)
     
  20. Zapins

    Zapins Gold

    I do the same as Jason. I blow the bubbles out with air or a brush if very stubborn for first layer or two.
     

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