Removing ceramic shell

Discussion in 'Investment casting Ceramic shell method' started by KC M@, Jan 1, 2021.

  1. KC M@

    KC M@ Copper

    Since the ceramic is so brittle, while it’s hot couldn’t you give it a quick dunk in water to shock/shatter it off? Not sure if the metal would crack as well. Online search only came up with waterjet as the preferred method for quick removal.
    Giving it some more thought it may be better to freeze the entire thing and dip it in boiling water that way the shell expands as is shatter vs contracting. It would definitely be safer. Thoughts?
     
  2. Jason

    Jason Gold

    Not really. I've tried it and water doesn't do what you would think it should. The best thing to get it to come off easily is give the metal a chance to shrink. The shell will not and it sometimes cracks.
    Personally, I don't really mind removing the stuff. It's kinda like christmas, you don't know what you'll get until you unwrap it.

    Remember, shell's number one attribute is it is dimensionally VERY stable at all temperatures! Heating or cooling only affects the metal and not the shell. I still like having a seat and grabbing a hammer and a pointed chisel and going to town. Once 98% of it's off, into the blast cabinet it goes. Now I will say, someone on one of my videos recommended some acid bath to dissolve the SHELL. What it was, I don't recall, but I wouldn't be surprised if it wasn't something like hydrochloric acid. I'm more interested in preserving the bronze and less on time. Maybe it would be helpful for areas where you can't point a bead blaster at or inside cavities.

    When shell is 7 or 8 layers thick, I can tell you it is anything but brittle! You have to beat it pretty damn hard. Impressive stuff that's for sure!
     
    Last edited: Jan 1, 2021
  3. Tobho Mott

    Tobho Mott Gold Banner Member

    The wax or the shell? Asking because of the context.

    Jeff
     
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  4. Jason

    Jason Gold

    Shell.. I'll fix it. thanks
     
  5. Zapins

    Zapins Silver Banner Member

    Yeah sand blaster is the way to go after hammering most of the shell off.

    Pneumatic hammers (air impact hammers) also work with chisel bits.
     
  6. KC M@

    KC M@ Copper

    Ok. I was worried about damaging the face accidentally but I guess you just be extra careful in those area’s.
     
  7. Jason

    Jason Gold

    That's what chasing is for. Every time I release a video, some einstein tells me I should be using a brass hammer or brass punch.:rolleyes:
    I love guys that have never cast a thing, but are experts at everything!? An impact gun would be the fastest if you forge the end of the tool maybe blunt?
    Use it to beat the hell out of the sprue and cup and it usually will knock a bunch of the shell off.

    When I did these flowers recently, it took me almost an hour standing at the vise with a small punch. 5 dogs each with 8 petals.

    20201216_202704.jpg
     
  8. dennis

    dennis Silver Banner Member

    Dogs? Would this kind of bronze work for lathe dogs?

    (No, no joke. Commercial lathe dogs are either rubbish for quality, or are priced fit for deep-pockets collectors. I'm wondering if this kind of bronze would work at least as well as the grade-c cast iron in the commercial offerings...)
     
  9. Jason

    Jason Gold

    shutter dogs. I cant see why it wouldnt work for lathe dogs. I have a lathe but havent used a lathe dog. Shaping it would certainly be easy. Make in wax the rough shape you want and machine the rest when it's in bronze.
     
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  10. dennis

    dennis Silver Banner Member

    Turning between centers is one instance where one desires a suitably-sized lathe dog - say, you want an unusual-sized buffer or three to better polish an unusually-shaped shell-mold casting. You need a special shaft for that buffer. You put a dead center in the headstock, a live center in the tailstock, and a lathe dog on the end of the shaft you put in the headstock.

    Turning between centers allows you to remove the shaft from the lathe and then return it - say, you've swapped drive ends, or checked the fit of your bearings, or something like that - and not lose your centered aspect.

    (Center-drill each end, first. The center points go in those.)

    Nice thing about a bronze lathe dog is it will not mangle your just-turned shaft. Just use a lead-tipped bronze screw, and perhaps rub a little solder on the nice warm lathe dog to make certain...
     

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    Last edited: Jan 2, 2021
    Jason likes this.
  11. Jason

    Jason Gold

    Nice collection of lathe dogs ya got there. A clever chap could probably make a tidy profit making these and chucking them up on fleabay!
    I say GO FOR IT! And don't forget me on the way to the top!;)
     
  12. dennis

    dennis Silver Banner Member

    Those are Not mine. I have one I made 20 years ago, and it's quite the crudity/oddity.

    I'd like to make some bent-tail dogs, and most likely will in the future.

    Perhaps I could make (the usual kind of) pattern(s), and let you pull silicone molds off for waxes? Say a range of four? Only "machining" that would be needed would be the usual cleanup, followed by drilling and tapping for your choice of binding screw...

    Really strange thought: could the original part be made out of balsa wood and the like instead of wax? Sort of like making lost wax nuts/seeds/insects?
     
    Last edited: Jan 2, 2021
  13. Jason

    Jason Gold

    Organics like balsa would burn out easily. check your pm inbox.
     

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