Casting Metal With A Microwave And Vacuum Cleaner

Metalworking might conjure images of large furnaces powered by coal, wood, or electricity, with molten metal sloshing around and visible in its crucible. But metalworking from home doesn’t need to use anything more fancy than a microwave, at least according to [Denny] a.k.a. [Shake the Future]. He has a number of metalworking tools designed to melt metal using a microwave, and in this video he uses them to make a usable aluminum pencil with a graphite core.

Before getting to the microwave kiln, the pencil mold needs to be prepared. A 3D-printed pencil is first created with the graphite core, and then [Denny] uses a plaster of Paris mixture to create the mold for the pencil. The 3D printed plastic is left inside the mold and placed in the first microwave kiln, which is turned on just enough to melt the plastic out of the mold, leaving behind the graphite core. From there a second kiln goes into the microwave to melt the aluminum.

Once the molten aluminum is ready, it is removed from the kiln and poured in the still-warm pencil mold. This is where [Denny] has another trick up his sleeve. He’s using a household vacuum cleaner to suck the metal into place before it cools, creating a rudimentary but effective vacuum forming machine. The result is a working pencil, at least after he wears down a few razor blades attempting to sharpen the metal pencil. For more information about how [Denny] makes these microwave kilns, take a look at some of his earlier projects.

38 thoughts on “Casting Metal With A Microwave And Vacuum Cleaner

  1. wow great idea…but who needs to do things safely these day….bare legs, bare hands, wobble table , carpet on the floor furniture and other combustables very near by….does nobody have any comon sense anymore !

    1. As long as the risks are contained to only those knowingly allowing these antics I don’t care and at such small scales while the results can absolutely be nasty for him the odds of any harm to anybody else are low (at least if his building isn’t a multi-occupancy tinder box), just don’t expect any sympathy from me when you do end up with a big medical bill and declined payments from your home insurance…

      Nutters in the basement/living rooms absolutely can and should make stuff, and do so at a minimum as carefully as the danger to others requires – you don’t race the Isle-Of-Man TT because you expect to live forever, you do it because the risk is worth it to you, or you are too stupid to realize it can happen to me… Either way its all on you, and you should be allowed to choose such a path if you want to.

  2. I love this project. So much expertise and skill is put into making such a striking yet useless object! It’s the epitome of what happens when you enjoy making things and just want to see what’s possible.

    1. Curses, walks out to workshop, changes chuck jaw direction in the lathe, chuck up pencil, loosen cross slide and adjust angle for your pencil point, loosen tool holder and adjust tool angle, tighten tool holder….

  3. At some point (80’s) those sharpeners were made of magnesium (or ‘electron’-metal, no big difference). They provided entertainment to kids with nothing better to do or burn…

    From the video it is obvious that they are not magnesium any more. Sad. Was better in ye olden days.

  4. Hm… waitaminute. This is not Aluminium! When he pours the molten metal into the mold you can clearly see the material glowing orange. Aluminium does not do that. It is still silver when molten and looks like a mirror. How do I know? Well, from my own casting experience of course.

      1. Then it would be glowing purple. That’s what nIR looks like through a Bayer filter camera, as the blue filter leaks nIR the most, followed just behind by the red filter.

        This is why dashcams & helmetcams that are exceptionally cheap or ‘low light’ (i.e. omit the nIR block filter) show intense fires as glowing purple before flames are visible.

    1. Many (but not all) pencil sharpeners are made out of a magnesium-rich alloy. I wouldn’t use any old random pencil sharpener as feedstock because i wouldn’t like a magnesium fire of that size on my work bench.
      I have to say, my magnesium sharpeners look much duller than the ‘fresh’ sharpeners. So i’d not immediately think these are magnesium. Still, i’d definitely try and test them.

    2. Aluminium most definitely glows orange, but at a temperature quite a bit higher than it melts. Suspect this is what happened here with the imprecision of the microwave method! Source: I heated up aluminium until it glowed orange, just before a concrete steam fracture cost me some of my eyebrow (thanks to safety specs my eyes are fine!).

  5. For anyone wanting to get into casting, look up building an (waist) oil furnace. It can be gravity fed. You need proper refractory, don’t fall for the YT videos that tell you to use plaster of paris as a refractory. There are books.

    For mould making, look up green sand casting (you can mix the sand yourself). The defects in this cast are deep and he couldn’t have “sanded them away” without seriously shrinking the pencil.

    Also, watch a few videos of safety. This video demonstrates utterly astonishing level of disregard of safety and common sense.

    1. It’s been my experience that it’s a lot easier to make a propane/air burner than a waste oil burner.
      But I have to admit I’m pretty interested in microwave based foundrywork as even the propane ones are kinda fussy.

    2. There is an Irish company called Prince August that makes hobby casting “moulds” for toy soldiers, chess sets and the like. They also sell lower melting point alloys in leaded and lead free varieties. They can be melted on a hot plate. It was a great intro to hobby casting and I have introduced my nieces (<10 yrs at the time). We made marching band figurines. While I would love to cast aluminum, I don't really have the space to do that safely. I have read that aluminum needs to be poured over dirt because if you spill onto concrete will heat up and shatter. Doesn't sound fun.

      1. When I was industrial casting there would be the occasional spill of a few pounds of metal(we mostly did steel and aluminum, the steel at least twice as hot) and I never saw that happen. It looked like normal concrete floor to me?

  6. Ok but making a furnace with some nichrome wire and a thermocouple isn’t really more expensive and it’s easier, more reliable and less labor intensive to use. The problem with this approach is that it’s open loop. You can’t control the temperature of your oven very well. That’s going to make things complicated.

    You can get little cheap metal melting furnaces on Ali express for about the same price as making something like this.

    An accomplishment would be one made in a pressure cooker using tungsten wire, which could melt steel, vacuum and maybe some argon would be needed as tungsten burns.

    There are ovens used for glassworking that might also be usable, idk how much they cost.

    Aluminum is pretty good though, there are some quite tough alloys.

    The insistence on using household items doesn’t make sense unless you can still get good performance.

    1. I agree almost entirely, though there is one way using household items makes sense to me – when your space is limited so the tool has to pull many uses or be indispensable to justify it spot. If that is the case then being able to use the same device for extra things and only have to store a minimal amount of ‘change gear’ might make it worthwhile.

      It may not be hugely smaller than a nichrome wire build, but its certainly smaller than the gas or oil ones – as they need fuel tanks and regulation for the fuel/air mix.

      But as I said on the whole… Lets just say I’d far rather build a thermocouple controlled kiln/foundry using nichrome (or more exotic higher temp materials if required) – if the thermocouple is precise enough (etc) its still multi functional as you have the ingenuity for.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.