Speeeeed Casting

Discussion in 'Investment casting Ceramic shell method' started by Jason, Oct 13, 2017.

  1. Jason

    Jason Gold

    So the job is to replace a leaking seal on a turboprop. We dig up the hydraulic press, all the weird custom funky tools and press plates. WHOOPS. One half of one of the custom made press plates decided to go for a walk. One thing I hate more than anything else in this world is a THIEF! It's 530 on a thursday afternoon when we discover we are seriously screwed. Attempted to borrow one from another outfit that works on these turbines and NOPE, they told us to get lost. I have one plate and that's good enough. Some sections of it are critical, but most of it is not. The goal is to blast a pair of these out in bronze with a quickness. Getting a machinist to start a job and finish it the same day is a pipe dream. Whats sad is any of you with a lathe could easily make this out of some 1 inch steel plate in about 2 hrs.

    Off to work I go! The goal here is FUNCTIONAL, working by monday AM and NOT PRETTY! There isn't much draft on it either, but who cares with shell. I do have a thickness issue, but that will be dealt with under the NOT PRETTY requirement! lol

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    Step one, LUBE her up real good! Goodwill junk silicone to the rescue. Too bad it had a hole in it I didnt see. Pissed a little. Silicone sealed her up. That is clay following a pin which is not needed. Thanks to Tobho Mott for teaching me this lesson or else it would have gotten stuck in the PoP.
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    Step 2. Mix PoP and dump it in.
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    Step 3, Eat a midnight breakfast while the PoP cures.
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    Step 4, pop it out and hope it works. Glad I made this block 2inches thick, I had to beat it against the bench to get it out. The wax should remove much easier even with zero draft. (I hope)
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    Off to bed! Wax, sprue and first shell in the morning. I'm thinking 3, MAYBE 4 layers and pour this animal a little cold... Artopsy?????? Got a suggestion for a pouring temp??? 1900 maybe? This CANNOT fail. There will not be enough time for another pour. Deadline is Sunday late afternoon. That may seem like a lot of time to you sand guys, but shell is a different animal and I'll need every minute.
     
  2. Artopsy

    Artopsy Copper

    Ooh, rush jobs!!! Love em. Theres nothing like the thrill of the chase when theres no second chance.

    Ok, so my first thoughts. I would probably have done it a bit differently, cutting out a few steps.

    If it was me i would have taken the metal plate and added wax strips to it in the areas that need a dimensional tolerance to compensate for the large amount of shrinkage you are going to encounter. I would then have created an open faced mould of sand and PoP mix the same way you have done for your wax mould (i would probably do a couple of these as back ups.) Burn out for a few hours, being sure not to go over 700 degrees C. Pour with fingers crossed.

    As you are going down the wax/shell route you will still have to be super careful of shrinkage and avoiding shell cracking. That plate is pretty thick so shrinkage and the casting flaws that can come with it will be the issue here. You can add extra wax strips to your waxes to compensate for the shrinkage if its important. You will need a BIG runner and cup to feed all that space. Reinforce all the shell where the sharp edges are as this is where it will crack. pouring with the shell supported with sand would be good in case of a leak. If you can, wrap some ceramic wool around the pour cup/runner after pouring to keep the feed metal liquid as long as possible.

    You are right, pour as cool as you can. Its thick so no problems getting it to fill.
    Good luck and thanks for documenting while up against it!
     
    Last edited: Oct 13, 2017
  3. Tobho Mott

    Tobho Mott Gold Banner Member

    Sounds fun, and a bit stressful... Good luck! Rootin' for ya.

    Jeff
     
  4. Jason

    Jason Gold

    Here is the first wax pull. Came out easy. A little trim and she'd be ready for shell.

    Now for the bad news. We will not get to see this get poured. I was actually able to get a machine shop to jump on this
    job TODAY! The first shop I went to, told me a MONTH. But that's nothing.... The current wait in Midland/odessa area is 6 months!!!!
    The problem is manpower. No one does old school stuff anymore. These boys can pretty much name their price out here in the oil patch.
    It will be cut out of thick plate on a lathe and then cut in half so I'll have two identical pieces. Sorry boys, but I really didnt think I was going to
    get someone to jump on it. But I'm glad in the end and now I can have the weekend off. PLUS, I met an awesome local guy that does machine work
    out of his house. Perfect for those last minute oh shit jobs on a saturday night that always seem to haunt me.

    Art... You are right, this thing is stupid thick... I was going to solve that by carving half of this wax pattern away. Remember the NOT PRETTY part? lol
    Thanks for the tips man, you guys are a wealth of knowledge and worth the $30 bucks thats for sure!:D:D:D:D:D


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  5. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Could have cast it in lost foam in 2-3hrs starting from scratch with no pattern to quenched aluminum casting. -Maybe an hour if I didn't mud coat it and had to wait for it to dry.....just sayin oh wizard of wax.

    Best,
    Kelly
     
    Last edited: Oct 13, 2017
  6. Jason

    Jason Gold

    DONE... problem solved. Now I can enjoy my weekend!

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  7. Artopsy

    Artopsy Copper

    Oh......... that was so much simpler if not a bit of an anticlimax. Wheres the scream of the furnace? the engulfing flames? the rush to cap the geyser of spurting metal? the dramatic tension building music? The cold beer and back slapping?
    Glad you found an easy solution and can chill over the weekend. I feel cheated but as long as youre alright!

    John
     
  8. Jason

    Jason Gold

    I was looking forward to the challenge, but this is the easiest solution. Sorry gang. next time.
     

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