[Jewelry making - Article 00202] - Re: [Orchid] Vacuum casting vs. centrifugal casting

[Jeffrey Everett]

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>         I have to agree on the melting technique and alloy but by
>     vacuum assist, do you mean vacuum assist as like in setting a
>     solid walled flask on a silicon pad and having the vacuum drawing
>     on the end of the flask? Or are you referring to using perforated
>     flasks, I never could get decent results with what I was told was
>     vacuum assist, (using a conventional flask and sitting it on a
>     silicon pad) I tried straws, wax web, all sorts of (remedies)
>     however, I swear by perforated flask vacuum casting. 

    I'm just using a silicon pad and only casting one-offs recently. I
    no longer cast commercially. However, I always had good luck with
    both wax web or bent rods hung over the side of the flask. Now I'm
    just casting into small flasks. I've always used hydrogen and oxygen
    for torch melting. I seem to get better results with it. I've used
    the Aurum induction machine (going back a few years) and resistance
    melting (Thermotrol and hand held melters). I don't know why you
    didn't get good results, maybe your investment mix? I'm sure someone
    more knowledgeable than me can answer. 

>         Do you recall in which issue of the Symposium the article was
>     published?. I certainly miss many technical issues being out in
>     the middle of the swamps of the Natchez Trace. Of course, I suppose
>     I could just buy the Symposium books each year (DUH) but then I
>     could be intelligent and that would scare my friends and family.
>     Not to mention the few customers I have left <grin> (the ones not
>     learning 2nd or 3rd languages) <not grinning>! 

    Sherman and the professor enter the WayBack machine... Enter the
    year 1985... give or take a year. I'm at the MJSA New York show
    looking at vacuum casting machines and reading literature given to me
    by a salesman in which microphotographs (from an electron
    microscope?) are featured. The photos show the molecular structure,
    in a side by side comparison of centrifugally cast and vacuum cast
    cross sections. The vacuum cast example is clearly more dense, the
    centrifugally cast example exhibiting voids on a microscopic scale. 

    I remembered the above while looking for the Symposium book. The
    only book easily found was from 1987 and the did not contain the
    information I had hoped to find, at least at a quick run through. I
    may have been wrong about the source. (grimace) I'm going to go out
    on a limb here and state that AJM magazine may have also had an
    article about differences in density between vacuum and centrifugally
    cast pieces. 

    I'll keep looking for the other volumes, but can make no promises.
    They may have been loaned out permanently, if you know what I mean... 

>     I have been using the Neutec flask bases and tapered sprue wax
>     though, very good concept I like the idea of being able to gently
>     remove the base, and the sprue holder is easy to fit in a swivel
>     vise. Makes spruing so easy, Also the material has a very fast
>     dwell time, so you don't have to hold the piece in place while the
>     sticky wax sets. Just for an experiment, I cut part of the bottom
>     off one of the sprues and used sticky wax to attach it on a
>     conventional sprue base and cast some Brass findings today on my
>     large centrifugal, very nice castings. The taper helps keep the
>     mass and weight down, so think I'll cut the ball shape down on some
>     bases and use the Neutec sprue wax for everything just glue it down
>     with sticky wax. I would like to see or find out about some of the
>     equipment coming out of Germany and Israel; I have heard some
>     incredible stories of how thin they can cast pieces. I've heard
>     down to 28 to 30 Ga. Over a 1.5 to 2 sq in. area. I'm sure that
>     will be the next criteria customers will be looking for before
>     heading for a developing nation!! 

    Maybe you're referring to the over-pressure casting machines. Nice
    machines! 

    I'm curious how you melted the brass. I use my old Thermotrol for
    casting brass and for casting large thin pieces. I don't like to
    torch melt brass. 

>         Do any Orchidians do "flask less or Paper Flask casting"?. I'm
>     curious if this is a viable alternative for small, as in very
>     small shops? 

    I used to used a ringless casting system back in the 80's when I was
    doing a lot of photopolymer burnout. The investment had to be mixed
    in a vacuum and only had a 4 minute working time. Came out of the
    oven hard as ceramic and required a hydrofluoric acid substitute
    (anyone crazy enough to use real hydrofluoric acid?) to dissolve the
    investment. Pain in the rear! 

>     Is Orchidians actually a suitable term or would Orchidites be more
>     acceptable.
>
>     Kenneth Ferrell Enjoying not having any Tornado warnings today. (but
>     wait till tomorrow) 

    Tornados always freak me out. One day I found myself looking up into
    about a 300 foot vortex opening a few hundred feet above me. The
    tornado had just torn up the town just west of us and was easing off.
    The clouds can do some truly amazing things (read either awesome or
    scary) in tornado weather. Darn tornados sound and feel like a
    speeding freight train 3 feet away... If I never see another one
    that's okay with me! 

I think Orchidians is more appropriate. :)

Jeffrey Everett

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