[Jewelry making - Article 00008] - Re: [Orchid] Button or No Button

[James Binnion]

========[ Invite a Friend - http://www.ganoksin.com/invite.htm  ]========

Hi Charles,

>         I would however caution people not to assume that 'feed' in
>     spruing does not matter. Feed of material to the casting to my mind
>     has to do more with supplying material for shrinkage, and I know
>     that shrinkage reservoirs, thick short sprues to thicker areas, and
>     other planning for 'feed' during cooling all seem to matter when
>     used. 

    The ideas about "feeding" from the button and shrinkage reservoirs
    are all valid if your casting is behaving like larger foundry
    castings this is called progressive solidification. The problem with
    progressive solidification theory is that it proposes that at one
    point in time the whole mold , shrinkage reservoir, sprue , button
    system is filled with molten metal. The reality in most jewelry
    scale castings however is that the model is solidified before the
    sprue is even partly filled. The most interesting thing from the
    paper at this years symposium and a paper presented a few years ago
    by some folks from Stuller is how fast the metal solidifies. All of
    us had thought that the here was for at least a brief period of time
    a situation all the mold cavities were filled with molten metal that
    then solidified from the outside in with the thinnest sections
    freezing first  but it appears that solidification happens much
    faster than we had thought with the model being almost totally solid
    before the sprue feeding it is filled so we need to rethink  how we
    design our metal feed systems to make sure we produce as little
    turbulence (which slows down metal feed) as possible and work on
    getting the metal into the mold as rapidly as possible because the
    solidification times are in milliseconds. 

    I am not saying that the sprue designs we are using are wrong, you
    still need to feed the largest section on the model with a sprue of
    thicker section than the heaviest section of the model and that
    should attach to a sprue or pouring cup of  even greater cross
    section. But the reasons for this are not to control progressive
    solidification but to speed the flow of molten metal into the model
    cavity. 

Warm regards
Jim

Jim Binnion

James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160
http://www.mokume-gane.com
jbin AT mokume-gane.com
Member of the Better Business Bureau

____________________________________________________________________
T h e   O r c h i d   L i s t
Open Electronic Forum for Jewelry Manufacturing Methods and Procedures
____________________________________________________________________
Orchid FAQ:
~ http://www.ganoksin.com/orchid/faq.htm
Orchid Archives:
~ http://www.ganoksin.com/orchid/archive
Orchid Galleries:
~ http://www.ganoksin.com/orchid/gallery.htm
Invite a Friend:
~ http://www.ganoksin.com/invite.htm
____________________________________________________________________
Tips From The Jeweler's Bench - Article Archive
~ http://www.ganoksin.com/borisat/tip_sear.htm
The Jeweler's Selected Bibliography List
~ http://www.ganoksin.com/jewelry-books
Buy Orchid Jewelry:
~ http://www.ganoksin.com/shop
____________________________________________________________________
-Unsubscribe:
-Email: orchid-request AT ganoksin.com Body=unsubscribe subject=blank
____________________________________________________________________