Which flasks do I need?

Discussion in 'Foundry tools and flasks' started by Bill W, Jul 22, 2021.

  1. Bill W

    Bill W Copper

    I have some ultracast ordered. Now, I need to buy some flasks. Seems the perforated flanged flasks is the way to go.

    The parts I place to cast have the following dimensions.

    part 1. 1 in wide, 2.75 in long, hollow with lot's of internal shapes.

    Part 2. pin 1/4 inch wide, 3 inches long

    Flanged flasks come in all sorts of shapes and sizes. for part 1, I doubt I could cast more than one parts at a time, Part 2 could be cast with multiple parts in one flask.

    How much free space should there be from the part to the inside wall of the flask?

    Thanks, Bill
     
  2. theroundbug

    theroundbug Silver

    Perforated flasks are used with vacuum casting machines to assist in pulling vacuum through the investment. Unless you have a machine like that there's no point in getting them; in fact it adds the unnecessary step of taping around the holes so your investment doesn't leak out.

    If you have a retail steel supplier near you you can get scrap cut-offs of steel tubing for like 20c/lb. That's what I did for all my flasks.

    You can use anything you want for the flask as long as it fits the part with some space between the walls and top. I like to have at least half an inch of space. There's a formula somewhere if you google it, I haven't had to remember it yet. If you're gravity pouring you'll want the sprue to be a little longer/thicker to add some pressure to the pour so keep that ion mind when choosing how high the flask is. This type of disposable flask obviously has to be removed before burnout so handle the invested mold carefully.
     
  3. DavidF

    DavidF Administrator Staff Member Banner Member

    Horse shit!!
    We make our own vacuum casting set ups on the cheap. It's easy to do and the benefits of using a vacuum casting set up far outweighs the time it takes to tape up the flask.

    A 4"x7" flask should do what you need. Typically you want 1/2" of investment between each part and the wall of the flask, and keep atleast an inch off the bottom to avoid blow outs.
     
  4. theroundbug

    theroundbug Silver

    Alright then, OP add making your own vacuum chamber that accommodates a commercial perforated flask to your to-do list then, because you know, gravity is horseshit and unless you are vacuum casting you shouldn't be making things. :rolleyes:
     
    Last edited: Jul 23, 2021
  5. Tobho Mott

    Tobho Mott Gold Banner Member

    To use gravity to accomplish what we've seen vacuum assist do for casting very small detailed castings in these small flasks, would you need to use much taller flasks for added head pressure? Curious because I would like to try lost wax casting some day. I own 4 pallets of firebricks and 2 big kiln burners but no vacuum pump. o_O

    Here's a video showing how to build a vacuum chamber fwiw. This guy makes it look reasonably easy:

    ;)

    Jeff
     
  6. DavidF

    DavidF Administrator Staff Member Banner Member

    Don't take offense man, but there is a huge difference especially with light weight alloys..
     
  7. Bill W

    Bill W Copper

    Thanks for your insight
     
  8. Bill W

    Bill W Copper

    Excellent! Thanks DavidF. I plan to make a vacuum table as I see a lot of benefits to removing all air from the investment.
     
    DavidF likes this.
  9. Bill W

    Bill W Copper

    Gravity has it's places in the world but it has it's shortcomings in making a mold from silicone (my experience so far). I'm new to this whole world of casting, molding etc. What I have seen is, silicone makes much better molds with vacuum over just gravity. The improvement is obvious. It stands to reason that vacuum will make better molds in investment too. I believe in doing what works and keep it simple. I got my box of investment today. I might get some disposable cups out and give gravity a try. I don't have a burnout kiln or a furnace yet so I won't be able to determine it I can get away with gravity just yet.
     
  10. Bill W

    Bill W Copper

    That's what I'm looking for. Simple, easy to make and doesn't take up much space. Thanks for posting the video
     
  11. DavidF

    DavidF Administrator Staff Member Banner Member

    If you do go strictly gravity, be sure to gate into the bottom and vent the top. I cut my teeth doing it this way, but vacuum assist is where it's at.. vacuum assist minimizes the gating and venting required. It also minimizes surface imperfections in the casting...
     

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