Lost PLA processes, products, knowledge.

Discussion in 'Home Foundry & Casting Projects' started by Jack3M, Dec 25, 2018.

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  1. Dec 28, 2018 #21

    kadora

    kadora

    kadora

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    Hello
    ABBY thank you for your excellent explanation of casting process but you know people will always TRY to find new easier way for making anything under the sun.
    I have found this video Portland cement mould
    RAVIV do you have two spare cylinder head castings for sale ? I would like to build V twin engine .
     
  2. Dec 28, 2018 #22

    abby

    abby

    abby

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    I guess that if you live in a place where the real thing is unavailable or hard to get then you will try all the possibilities , genuine Mansfield moulding sand is dug from a quarry not far from me and it is much cheaper than cement...............and it works !
    Dan.
     
  3. Dec 29, 2018 #23

    Richard Carlstedt

    Richard Carlstedt

    Richard Carlstedt

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    Thank You Dan !
    You are the first person I've heard to state what really happens
    "The plaster component contains water of crystallization which will only be driven off at 550°C.:"
    You will see in my post ( #5) that temperature is critical. Even the two gentlemen that taught me Lost Wax used the wrong term .."Burn-out", ....its not, its conversion of molecules that release water. Had a two piece mold ( no wax) that was dried in a oven for 3 days at 200 C then immediately raised to 590 C in 2 hours and due to the shop closing rushed to pour Bronze and it blew apart-- I should have known as I saw spirals of water vapor leaving the Sprue and condensate on the Kiln Door when removing the mold. Sorry for the rant , but I wasted months on a failed project before discovering the error in terms and think Newbies deserve the truth, and not fairy tales.
    Rich

    And yes, I now only pour at 1300 F ( 700 C) even with "no Wax paterns"
     
  4. Dec 30, 2018 #24

    abby

    abby

    abby

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    Rich , I only use Goldstar Omega investment cement which I have found to be the most reliable for my way of working.
    My burn-out kiln holds 4 x 6" dia flasks 12" deep which is around 12 lbs each in weight of investment powder and can mean between 4 and several hundred castings.
    The heating cycle starts with a five hour soak at 180°C , the moulds are upside down for most of this time and the molten wax runs out into a collection tray.
    Near the end of the 5 hours the moulds are turned upright.
    Over the next 90 minutes the temperature is ramped up to 350°C and soaked for an hour before ramping to 550°C over the next hour and again soaking for an hour.
    These temperature transitions are not fanciful , they are actually needed.
    The first soak is to do with a change in state of the refractory component , the second is the water of crystallisation.
    At this point there should be no water present either free or combined but there may still be wax and soot.
    The final ramp is to 725°C and the soak can be from 2 - 5 hours , I have found that some of my moulds have still had traces of wax after 3 hours soak.
    Good ventilation should help any soot to disappear.
    Final casting temperature will depend upon the metal and the thickness of the castings.
    For aluminium I allow the moulds to cool to 150°C or less , for copper based alloys I cast at 400-500°C.
    Casting wax has no inert fillers and residue is less than 0.1% , presumably the new "lost plastics" are the same.
    I have "burned out" insects , cloth , wood and even Airfix model kits, these can leave ash residue so a catchment area should be made in wax and attached to the pattern.
    Molten metal can flush the ash out of the mould and into the catchment.
    You may find more information on my website http://www.unionsteammodels.co.uk/
    Dan.
     
    aonemarine, worksengineer and Jack3M like this.
  5. Dec 30, 2018 #25

    Raviv

    Raviv

    Raviv

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    Hi kadora
    i can cast a few more and have them available.
    if you need a specific head volume, let me know, currently these are design to have approx 6-6.5cc in order to achieve a static compression ratio of approx 8.5:1 (50cc for each cylinder).
     
  6. Dec 30, 2018 #26

    kadora

    kadora

    kadora

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    Excellent I have sent you personal message.
     
  7. Dec 31, 2018 #27

    Richard Carlstedt

    Richard Carlstedt

    Richard Carlstedt

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    DAN
    You had more valuable information in your last posted paragraph than most any book or article
    Thank You !
    I have done wax, pine cones and permanent (aluminum patterns ) split molds and have only poured in Brass, Bronze and Silver
    Rich
     

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