Basic pointers and advice

Discussion in 'Lost PLA casting' started by Erik CNY, Mar 25, 2020.

  1. Erik CNY

    Erik CNY Copper

    I joined this forum and got interested in casting for a specific project. Making an end cap of aluminum.

    I was hoping to run a very rough outline of my plan by anyone interested here on the forum and hopefully get flaws or pitfalls pointed out.

    1. Build a very basic furnace - charcoal in a steel bucket with a hairdryer kind of thing.
    2. 3D print the part and make a plaster cast.
    3. Cast an oversized shape that I then bring down to size with hand tools.

    Is this a reasonable plan to get a solid chunk without a bunch of voids? What should I consider to be able to pull this off?

    The cap would look something like this.
  2. Al2O3

    Al2O3 Administrator Staff Member

    Hi Erik, what’s the approximate wall thickness L x W x H of that part? How many do you want to make? What does it do?

  3. Jason

    Jason Gold

    Lost PLA in plaster? uh not without some major difficulty. The clowns on youtube will have you to believe this is childs play. It is not. At a minimum, you'll want a commercial investment. Even then, it can be a tough road. Lost foam casting that would be easier for a first timer and you might actually have a usable part or two on your first attempt.

    Looks like you have it drawn up already. Know anyone with a cnc mill? Assuming you don't need 50 of these, that would be an easy job for that method.
  4. DavidF

    DavidF Administrator Staff Member Banner Member

    I think its perfectly castible (by design) using lost pla.
    One thing you will need though is a kiln with a temp controller on it to do a proper burn out.
  5. DavidF

    DavidF Administrator Staff Member Banner Member

    Did you see that square inside corner??
  6. Jason

    Jason Gold

    It looks like a cap to a railing or something. That's probably not important.
  7. Erik CNY

    Erik CNY Copper

    Thank you for getting back to me. I really appreciate it.

    @Al2O3 - The rough size is 1.25" x 1.25" x 2" with a wall thickness of about 5/32". I'm sorry I forgot to add the size. I realize that is crucial information. I'm making the wooden stock that this cap will be fitted on, so the wall thickness could be adjusted to make things easier when casting.

    @Jason - I don't know anyone with a mill which is what made me wonder if I could pull this off by casting the part. I only need one. I definitely see your point, and things like that inside corner does not need to be square like that.
  8. Al2O3

    Al2O3 Administrator Staff Member

    I think it's quite feasible pretty much as you have described with David's caveat about access to a temp controlled kiln to cure the investment and preheat the mold.

    I think the most challenging part is probably burning out the PLA and curing the investment without breaking the mold. You may be better off with a commercial investment for this reason, and it wouldn't cost much for the small amount you need, but I used to cast all kinds of small aluminum and zinc parts in plaster 30 plus years ago, and my Dad was making model teather cars and model engine parts for them with the method in the early 1950s.......It was lost wax not lost PLA but it's not breaking new ground.

    It depends upon your tolerances but for the accuracy of a printed part I think you should expect to cast a net shape part that requires no machining. You will need some coaching and thought on the gating/venting and probably need to have the investment preheated in the 300-500F range when you pour. Slightly increasing the wall thickness increases probability of success.

    Melting aluminum is the easy part. For one piece, and no kidding, you can literally dig a small hole in the ground, place a steel crucible on/surrounded by charcoal on top a grate, and use a hair drier to pump combustion air under the grate and through the charcoal charge. Charcoal is self insulating and this will easily melt a small amount of aluminum. Fill the hole in when you're done, you can always dig another one.

    Just use a scrap casting for metal, not extrusion, pop cans, or non-casting alloy.

    Here's one of Myfordboy's videos that may be of interest to you.

    Jason likes this.
  9. Erik CNY

    Erik CNY Copper

    Thanks for the advice and resources, @Al2O3
    Much appreciated.
  10. Is this to learn how to cast or because you need the part? If you need the part and you only want one you could have it machined for a few hundred dollars. Or 3D printed in metal. Almost any machine shop can make this for you. If you want to learn how to cast it will be an interesting project but will not save you time or money, it will be a labor of love.

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