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Thread: Casting Alluminium the myths and facts....

  1. #1
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    Default Casting Alluminium the myths and facts....

    I Have often seen on many outboard forums about how bad the Lost Foam casting process is v the other types including
    Sand-Casting , Die-Casting and Perma Mold.
    Far too many myths going around about Lost Foam being inferior to other molding types.

    it realy is just another one of those things about " it was better in the old days" well it actually was not.

    Is Lost foam cheaper when doing mass production work ? NO
    Is it is cheaper if doing very short run of say 20 to 50 ? possibly YES

    As for being a more porous and weaker casting then it is actually the die casting that is the weakest process for casting aluminium.
    There will be some die hards who will not be able to take that in as they believe lost foam is the bad boy because they got told it.
    They have obviously never realy looked into the complete process of casting and found out what strengths certain types of casting have.

    Just because so and so down the road who makes a few parts says his old school way is best, the myth grows and grows.
    It is just like " the old cars were far better than the new ones" yeah I suppose those new ones that do 5 times the mileage and dont
    rust away inside 5 years are crap. and those new cars are definitely not as strong, except drivers and passengers walk away from
    30mph accidents totally unmarked 99% of the time, unlike back when the cars fell to bits and killed everyone in the car..
    We like to think old fashioned stuff was better all the time, well that is not true, some things were infact realy bad, but our memory is
    often shrouded by silver clouds and rose tinted glasses.

    Here is a small passage from the link at the bottom, there are graphs too in the link showing many things about casting.

    "Permanent mold has demonstrated the best internal metal soundness. The Lost Foam process has smooth
    metal flow characteristics resulting in less gas entrapment during pouring and producing results comparable
    to Permanent Mold.
    The lack of cores or sand bonding media in the Lost Foam process eliminates gas absorption from the mold during solidification.
    By contrast, die castings are noted for air and gas entrapment and can be expected to demonstrate the most porous metal characteristics."


    a good bit about the aluminium casting can be found here, it will open a few eyes and cause many to understand a bit more about why
    many companies use lost foam and not for it being cheap, far from it...

    http://www.lostfoam.com/assets/conte...numcasting.pdf

    .
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  2. #2
    Team Member R Austin's Avatar
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    Very good read.

    Lost foam has become a very widely used process. OMC I believe had the patent rights to the process. I was told during a visit to the Saturn plant that they had purchased the rights to produce their engine block with the lost foam process from OMC. They did their castings in house. Someplace in my many boxes of "things" I still have a few sets of V6 foam sets, pre-glueing, that I was going to glue up in a block for running the crank in a horizontal position. Things were not going well with OMC at the time, so did not get completed. Thats when I just cut, welded and made the horizontal shaft 115 Eagle for the Fling.

    I do believe that one of the down sides of lost foam is the production of heavy castings. No fault of the process but that of design for better production runs with thicker walls and less cold shut problems.

    I find it funny / strange that I made my first lost foam cast aluminum part in 1978 by carving the needed part out of a piece of old styro-foam and gently packing in sand to not distort. Much to my amazement, the foam burned out and I had a part.

    Arconic aka Howmet of Whitehall Mi, 40 miles south, had a open house plant tour last Saturday. They produce jet turbine blades.

    They use the investment cast process of wax as describe in your piece. An absolutely amazing process, unbelievable tolerance control, with what is refereed to as a single crystal titanium pour. Pictures attached of a blade that I had purchased on year ago on E-Bay. You can get an idea of the coring by all the air bleed passages visible in the part. Cooling air enters the xmas tree end of the part and is core to the outlets.

    Yup, made by Howmet. Documented by its serial number. A very modern state of the art facility. Indescribable quality control and lifetime part traceability

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  3. #3
    BRF Team Europe Member Per's Avatar
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    Used to work with turbines, miss it from time to time...
    Beutiful blade, and that is only on the outside, sometimes they have qiute complicated sandwich structure inside aswell.

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