Petrobond/Green Sand Hybrid Mold

Discussion in 'Sand Casting' started by Melterskelter, Apr 7, 2021.

  1. Melterskelter

    Melterskelter Gold Banner Member

    Today I wanted to make one more mold for aluminum flask parts but ran out of petroband after the last mold was half finished. So, I decided to try a combination mold---petro drag and green sand cope. I thought it would serve two purposes as it would allow me to make that last mold and pour it and it would test out how well petro could be separated from green sand when used together in a single mold. This was partly related to the video we saw of the guy using "loose pieces' of petrobond in an otherwise green sand mold.

    The end result was that it worked quite well. I was able to segregate 99.99% of the petro from the green sand after pouring and there were no problems with molding encountered.

    This also gave me a chance to compare the finish afforded by the green sand and the petro in about as fair a comparison as possible.

    Here are a few pics
    This is the open mold prior to pouring:
    Flask End Mold (1).JPG

    Post pour petro on bottom and still smoking a little.
    Flask End Mold (2).JPG

    The resulting flask ends. You can see I followed someone's advice and made a hot riser at the center of the side and eliminated the risers from center of the flask bosses. This prevented shrinkage. Flask End Mold (3).JPG

    The side seen is the side that was in contact with the green sand. There is a slight difference in that the petro has fewer bubble defects--they actually look worse in the pics than real life--than those seen on the green sand side. For the purpose intended for these parts either surface is more than adequate.

    My conclusion is that petro and green sand can be combined and can be segregated post pour. Petro does give a slightly nicer finish but the green sand gives a very acceptable finish. I will also say that I forgot to slightly incline the mold. Had I done so, the aluminum would have progressed more smoothly from gate to the end of the mold and the finish would have been better.

    One more pour of just two flask sides and I will have my second set of aluminum cope, cheek, and drag flasks to be used in pouring 18" prisms---a pattern I have probably poured 30 or forty times to date and anticipate a good many more pours. The aluminum flasks are a luxury compared to the wood ones.

    Last edited: Apr 7, 2021
    Clay, Chazza and Tobho Mott like this.
  2. Chazza

    Chazza Silver

    Nice work Denis!

    As usual you have experimented and proven a practice in a methodical way, which can be replicated.

    Aluminium boxes are a wonderful thing, my new ones have solved many problems for me,

    Cheers Charlie

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