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  1. #1

    Join Date
    Jun 2021
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    17

    CNC to Metal Casting!




    I'd like to present this DIY process for CNC to metal casting.
    If you have a CNC machine and a casting furnace you can do this yourself.
    Feedback and comments welcome.

  2. #2
    Member
    Join Date
    Apr 2004
    Posts
    5402

    Re: CNC to Metal Casting!

    Sorry, Ramakarl, but that's all wrong. First off, the whole plaster step is unnecessary. The wooden carving will make a perfectly good pattern without going through all that. Second, you want to have a contoured pattern of an even thickness, cut on both sides, not just one. This goes in the middle of the flask, which should be divided into two parts (called the cope and the drag). That way, the thickness is controlled as well as the cooling of the metal. You ram the sand, then pull the two parts apart and reassemble the mold with holes cut into the top sand portion for the metal to enter and the air to exit. Pouring an open-faced mold just doesn't work too well, as you demonstrate. Your pouring technique is dangerous; you're not supposed to grip one wall of the crucible with your tongs and pour like that; this risks catastrophic failure, which would pour hot metal all over your tennis shoes (not the right attire for this process). Invest in a proper pair of tongs that grip the crucible on the outside, under the bulge, and a pouring ring that supports it while it's tipped. You can't just pour more aluminum on top of metal that's already cool; it just makes a mess, as you probably noticed. And please, lose the horrible music...
    Andrew Werby
    Website

  3. #3

    Join Date
    Jun 2021
    Posts
    17

    Re: CNC to Metal Casting!

    @awerby
    Rather than only criticizing my methods why not, at very least, ask my *why* I did certain things rather than assume or judge.

    I added the plaster step because it gives me the opportunity to select portions of the large woodwork and make additional pressings/casts into sand without having to cut up or modify the original woodwork. Its also a good skill to be able to cast into plaster, and gives creators more flexibility. This step lets me cast a positive metal relief from a negatively cut wood relief. Not possible the way you describe.

    I am aware that casting typically involves a cope and drag, and have cast this way in the past. I choose an open, one-sided mold because the relief does not require two-part and is therefore simpler to construct and pour - and for others to learn how. I have seen videos of cope-and-drag two part molds poured horribly wrong without gating or venting, or just poured too quickly so that trapped air overheats, vaporizes, and causes a pressure explosion. This is less likely to happen with open-faced molds, since the air from the relief always has a place to escape (upward).

    Pouring an open-faced mold can work well. In this case it didn't (I believe not sufficiently heated). I am still learning how to pour larger, sheet-like, metal work without portions of it cooling before its complete, so cut me some slack or please feel free to describe how you would do it. Ideally I'd like to cast 3 x 3 ft. lacework-like metal or larger. Large iron fence castings are often done as open pours. That is the approach I'm seeking to replicate.

    As to the gripping of the crucible with tongs, you can point to GG-5500 and many other hobby furnaces which ship with these cheap tongs. I have used scissor tongs before, and I agree they are better, but I don't have a pair of those to fit my crucible at the moment.

    You say: "you can't just pour more aluminum on top of a metal that's already cooling.". I can, and I did.. I know that single pouring is the preferred way to cast a complete piece. However, having the incomplete partial cast, and knowing that additional metal would create a visible seam, I decided to do an additional pour both as practice and as visual experiment. I like how the seam appears in the final work.

    Fair point on the music. I am intentionally supporting open source (CC0, CC-BY) via FreeMusicArchive or similar, rather than using copyrighted musicians like most youtube videos (and hoping they pass contentID). However, because of that, the choices are much more limited. I welcome better music selections to fit the work. My work is intentionally in a non-spoken style as I am tired of 'How to DIY..' videos that are too literal. I am combining making with videography and nature. The steps are easily visible, visually, and talking about each is unnecessary when you can see it happen. The videos I post in Natural Making are more creatively edited and intentionally less descriptive. Thus I don't accept your 'get rid of music' statement for how I intend to present my work overall.

    At this point, based on your strongly critical, non-constructive feedback -- if I could delete this entire thread I would. (But cnczone doesn't seem to have a way for a poster to delete their own thread)
    You have pretty much soured any interest I have in participating or contributing to cnczone again. Nice job - or perhaps that was your goal.

  4. #4
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    Apr 2004
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    5402

    Re: CNC to Metal Casting!

    If you don't want to hear what people have to say, don't end your post with "Feedback and comments welcome".

    If I see someone doing things dangerously wrong, the question of "why" you did it that way seems secondary at best. If you were just showing us your process and asking for help, I would probably have taken a different tone. But you were putting your process out there as a model for others to copy, even though it would put them in peril. There's way too many bad examples of this sort of thing on the internet; people have died trying to follow some of the methods being demonstrated, like fractal wood-burning with high-voltage electricity. Molten metal is not something that people with no idea of what it can do to them have any business messing around with. It needs to be treated with utmost respect, or terrible injuries can occur. I feel you owe it to your audience to demonstrate proper procedure and use the correct PPE, and spend at least a little time warning them about the dangers of what you're asking them to do.

    If you want to discuss the fine points of metal-casting we can do that; I can tell you've got a lot to learn about it. But if you're just interested in airing your hurt feelings and going off in a huff - bye.
    Andrew Werby
    Website

  5. #5

    Join Date
    Jun 2021
    Posts
    17

    Re: CNC to Metal Casting!

    > If you don't want to hear what people have to say, don't end your post with "Feedback and comments welcome".

    How did I know you'd come back with that ; )
    My answer is.. I seek out forums like cnczone to connect and discuss with others. Your post above does not seem interested in a back-and-forth dialog whatsoever.
    On a forum, "feedback and comments" to me implies seeking a dialog with a community.
    You present criticisms without asking a single question on my goals or methods. You post above just reads as a litany of gripes.

    > If I see someone doing things dangerously wrong

    As I've hinted, I disagree with your characterization of "dangerously wrong". Metal casting is inherently dangerous, but *all* making has dangers to various degrees. There are places where people cast metal in shorts and sandals. One could argue that a head-to-toe reflective suit is the ideal attire for casting. So there is a chosen degree of risk in how any individual chooses to work. I am wearing a full face shield, full length sleeves, long pants, and welding gloves -- this is much more safety attire than many of the videos you refer to. We could probably have a long discussion on metal casting safety. But honestly, I'd rather not with you.. You've already shown only a cursory interest in my artwork/process itself.

    > If you want to discuss the fine points of metal-casting we can do that

    Yes, I'd much rather talk about that.
    So far you've missed out on many of the things I'm trying to accomplish by not having asked a single question about my work.

  6. #6

    Join Date
    Jun 2021
    Posts
    17

    Re: CNC to Metal Casting!




    To the cnczone community...

    I've replaced the first video in this thread with the newer, edited one here.
    See the new description with the youtube video, which I've copied here:

    "This project shows how to DIY cast in metal from a CNC routed original wood relief. Safety visuals for both CNC and Casting are shown in the video (pause on them). The complete process is wood (negative), to plaster (positive), to sand (negative), to metal (positive), which allows the master wood relief to be saved. I use a plaster intermediate positive so that the final work will be a positive form, and this is a good skill to have. The process shown is a one-part, open mold, which is possible because a relief has no undercuts and thus a two-part mold (cope & drag) is not need. Open molds can also be safer for beginners since air is never trapped inside. The tongs shown are not ideal, and better casting tongs with a side ring and top hold should be used. Metal casting is usually done as a single pour. Here I intentionally did two pours because the first did not complete, and I wanted to experiment. I am pleased with the seam appearance in the final and might try multiple pours again for aesthetic. Experimenting and learning to cast can be a fun and iterative process. Stay safe and enjoy!"

    I welcome real dialog with anyone interested in having a two way discussion.
    You can find me here or comment on youtube.

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