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Thread: The Bucket Foundry

  1. #4006
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    Quote Originally Posted by oxracer View Post
    Ha! I wish. ������
    Thats alright me still have Mike Moore Ex NZ prime minister and chair of WTO framemaker plus a fairly famous Hollywood film producer



    Kinky is using a feather. Perverted is using the whole chicken

  2. #4007
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    Finally a concrete expert turned up at my place. Furnace is poured, now we wait, three weeks to dry apparently. Concrete mixer was my father's, father's mixer, older than me! It's been sitting in Claire's garden as a feature for more than ten years. Pluged it in and away it went, built old days proper.
    A 240V winch with a pendant turned up a few weeks ago, free, so it's starting to happen. At last!
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  3. #4008
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    Quote Originally Posted by Flettner View Post
    Finally a concrete expert turned up at my place. Furnace is poured, now we wait, three weeks to dry apparently. Concrete mixer was my father's, father's mixer, older than me! It's been sitting in Claire's garden as a feature for more than ten years. Pluged it in and away it went, built old days proper.
    A 240V winch with a pendant turned up a few weeks ago, free, so it's starting to happen. At last!
    So what was the castable refractory you ended up using Neil.



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  4. #4009
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    This stuff.
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  5. #4010
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    I was watching a green sand casting the otherday for ductile cast iron with greensand just before they put the cope and drag and core together they sprayed on a coating which was then set on fire to be burnt off it was claimed to improve the surface fnish i suspect it also added carbon to stop it sticking a bit of searching leads me to believe the ingredients are mainly alcohol some bentonite ?
    Anyone know what it is?



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  6. #4011
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    Some sort of ceramic paint on stuff. Paint on then set fire to it, burns off leaving a smooth surface behind. Not really nessasary I think for what we do.

  7. #4012
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    Quote Originally Posted by Flettner View Post
    Some sort of ceramic paint on stuff. Paint on then set fire to it, burns off leaving a smooth surface behind. Not really nessasary I think for what we do.
    Yip but this one was spray, burns like a good-un



    Kinky is using a feather. Perverted is using the whole chicken

  8. #4013
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    managed to get the inner mold out. Take the spacer out and shrink the ring with a giant vice grip. Two weels and five days to go.
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  9. #4014
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    Quote Originally Posted by Flettner View Post
    managed to get the inner mold out. Take the spacer out and shrink the ring with a giant vice grip. Two weels and five days to go.
    Looking good! - Inner former done the same way mine was, except mine was slightly more puny!

    Very impressive job!
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  10. #4015
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    Quote Originally Posted by Flettner View Post
    managed to get the inner mold out. Take the spacer out and shrink the ring with a giant vice grip. Two weels and five days to go.
    https://www.kiwibiker.co.nz/forums/s...w-bike!/page15



    Kinky is using a feather. Perverted is using the whole chicken

  11. #4016
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    An observation.

    So, with an FDM 3D printer, basically one is limited to plastic printing. Fair enough. So, if one wanted to make cores using 3D printed coreboxes, one is essentially limited to coldbox curing methodology, eg sand with CO2 , resin bonding etc, mainly cos the common plastics used for printing, eg PLA or ABS start melting around 200 deg C. Now, if one wanted to make really complex intricate type cores, you’d be chasing something stronger then these sand based systems.

    Enter casting plaster (aka plaster of paris). Relatively strong, nice finish and reasonably easy to fill moulds and cavities due to its pourable nature, prior to quickly setting, is cheap and accessible. Good so far. So, we make a casting using a plaster core. All good until the plaster has to be removed down some long intricate blind passage. How to break it out or at least soften the plaster?

    Well Googling tells me that acetic acid (a component of vinegar) might be the go. Could be others, even better, but that’s where I stopped at. Vinegar is 5% and cleaning vinegar is 6% and can be readily bought.

    Let’s give it a try. As an aside my (good) wife does glass slumping

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    so I grabbed some pieces she uses to slump the glass over. Been through as heat cycle, up to 650/700 deg C. Stuck these in cleaning vinegar in an ultrasonic cleaner and, after a while, they became soft and could be easily blown away.
    I then made some more shapes and retried them as per above (no heat cycle) and no effect at all, still hard. So, then made up 6 more: 2 @ plain plaster, 2 @ 50% plaster and 50% sand and 2 @ the same plaster sand mix with around 10% chopped fibreglass strands. Then, with one of each, these were placed on edge of furnace crucible during a piston cast, the melt being at 760 deg C.

    The non-heat cycled shapes are on the right, with plain plaster at the bottom, 50/50 mix in middle and the fibreglassed shapes at top. You have to view the pics as if rotated by 90 deg clockwise....dunno why it does this. The heat treated ones might look a bit shitty cos they fell into the melt, so came out with aluminium stuck to them, which slightly damaged them on its removal.
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    The 6 (plus another 2 bits from the glass process) were then given the vinegar and ultrasonic process. Pics tell the story. Of the furnace fired 3 off, the 50% sand/plaster shape really broke down. Clearly some form of chemical change occurs with the plaster after a heat cycle.

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    While just a “rough as guts” exp’t, it gives me the confidence to go ahead with a trial printed mould and a sand/plaster mix which will be given a heat cycle before casting. Good news is that the aluminium wasn’t affected by an immersion in the vinegar.

    It might be that the heating due to the casting process is enough to soften the plaster without having to go through the preceding heat cycle.

    However, if someone can suggest anything else, I'm all ears. Also make the point that this is not a volume production process at all, maybe just suitable for almost bespoke bits.
    "Perfection is the enemy of progress"

  12. #4017
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    Ken, in his "Complete Casting Handbook" Campbell mentions making cores for investment casting from a slurry of ceramic and wax, apparently with the core then fired to melt out the wax and leave a core behind which is easier to remove from the casting.

    I wonder if you could buy very small wax beads to mix in to the plaster?

    He also mentions the Shaw Process (Clifford and Noel Shaw, 1938) investment two-part block molds. This is conventional cope/drag molds with a ceramic slurry "prepared as a colloidal suspension of silica in alcohol, to which are added various ceramic fillers to make a smooth cream . . . after the mold is nearly set, but retains some flexibility as a gel, it is stripped from the pattern and placed on a board to dry and develop its green strength. At this stage the alcohol is flamed off, causing the surface of the modl to develop its characteristic micro-crazed structure, conferring essential permeability and thermal shock resistance to the mold."

    https://en.wikipedia.org/wiki/Cerami...g#Shaw_process

    cheers,
    Michael

  13. #4018
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    Fletto's flying high.....dunno if he got to a mile up though...

    Here's an article on his gyro powered by the engine he made, much of which he divulged here on Foundry. Well done Neil/Fletto...hope the orders roll in...

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    Still got his steel caps on...think of how much faster it'd go if he just wore thongs...
    "Perfection is the enemy of progress"

  14. #4019
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    That's a fantastic article. Really enjoyed that, thanks.
    Although...as a Brit, talk of thongs conjures up quite a different picture to the one you're thinking of!

  15. #4020
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    Indeed well done Neil and good to have seen progress here.
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