I always enjoy casting, and on my birthday in November 2024 I decided to try making some aluminum bronze for an espresso funnel. This is the sand mold, with a 3d-printed ring-shaped pattern pressed into it.

And the pour, at night in the backyard. You can see the glowing crucible, the furnace and the molten metal in the mold's pour opening.

It looks like it was a success: here's the casting freshly shaken out of the sand.

A couple of days later I started cleaning it up on the lathe. The aluminum bronze looks amazing as it cleans up. It's just 90% copper and 10% aluminum, and one application is propellers. It's really pretty.

A few days after that, I'd gotten in a bit of machining over lunch. Plenty left to do. The top is faced and the inside is bored, with some casting pits still remaining.

In January 2025 I finally finished turning the espresso funnel. It's totally ridiculous, but I wanted to make something out of aluminum bronze, and the 3D printed one I'd been using was unsatisfying. This one weighs like three pounds, which is very satisfying.

Here it is next to the purple 3D-printed one it replaces. I really should thin it down some more, but it's amusing me as it is.

A quick 3D print project: an add-on steam handle for the espresso machine, clamped to the steam knob with a small socket screw.

First, the pattern for the casting I hoped to do that weekend: a tree of a dozen small open-frame pieces on a central sprue.

And a single piece, which is what each keychain will be.

A partially successful casting on the morning of April 27th. This is the robot part in the crucible, melting.

Breaking the investment flask open to see what came out.

And the aluminum tree itself. I only got 8 out of 12 pieces to come out, so I need to do another. I think maybe the graphite gasket I made didn't give a good seal, and I didn't get as much vacuum as I could have.

After fettling, the pieces got powder coated, and here they are curing in a toaster oven.

I finished the senior gifts on May 15th. I still have a largish brick of the aluminum left over from the melted-down part, since I didn't use much of it. It's a part we removed because we were over weight, and I plan to bring it in to show people just how much aluminum it was.

The plan was to melt down some of the broken parts from that year's robot and cast keychains in the shape of the game piece, and maybe laser something onto them if there was time. This project was way more of a pain than I thought it would be, but I learned a fair amount, so I'll call it a win.

here's the finished keychain, presented to the seniors at the wrap-up banquet on May 19.

First I had to peel off the insulation. The lathe made a convenient way to hold the spool.

Then I realized I could wind the bare wire on a mandrel on the lathe and get a tighter winding for less effort.

The coils went into a graphite crucible, and were poured into a sand mold that was not, unfortunately, packed tightly enough.

A little turning cleaned it up a lot. I have been using one of the two as a drift, for tapping things down into the vise. The other one will probably get melted down again to make something at some point.

Here's my casting setup under the deck on the night of August 16, 2023: the propane furnace with its lid glowing, the tongs, and a wooden sand flask ready for the pour.

And the result, still sitting in its sand mold.

It's about 2" long. It's okay, with a few minor defects. I may try again.

I didn't get any video of the pour itself, because I was busy managing a crucible full of very, very hot, very heavy liquid metal.

Here's the crucible glowing hot, sitting on firebricks in a box of sand. The muffin tin next to it has a glowing ingot in it.

A few days later I decided to machine the cast iron blob I'd cast, just to see how it went. I didn't take it all the way past the defects, just enough to make it more or less square. It machined very nicely!

A few casting voids remain, and the edges are a little rough. I will definitely have to try this again.

My daughter was about to turn 18, and she really likes Infinity Train, which is a bit obscure: a surreal animated series. I'd wanted to do more jewelry, and I'd done a few rings, so I designed these earrings based on One-One.

Here I'm placing the sprue in the middle of the 3D printed pattern. I wish I'd remembered to make some marks to help me center it, so that I could use it to grip the casting on the lathe.

With the sand packed, I separated the two halves of the flask so I could remove the pattern. The bottom half still has the pattern half-embedded in it, and the top half has the matching impression, with the hole for the sprue.

After the pour, I dug the casting out of the sand. It was looking good so far: you can see the disc, the pillar, and the spoon-shaped sprue coming out of the sand.

Success! It's super rough, though. I think I should have sieved my sand. But every surface is going to get machined, so it should be fine.

The next morning I started cleaning it up on the lathe. One face took a cut nicely and came up bright, with the rough sand-cast rim still around it. There were going to be some voids and inclusions in the finished part. Tim said that was fine, as long as it held the thing and conducted heat.

Flipping it around to do the other side meant gripping the faced rim with the chuck's outside jaws, with the sprue stub sticking out toward the tailstock.

It was loads easier to cut most of the sprue off on the bandsaw than to machine it away.

And done. The front face, up top, has a raised center step. This is the back: a shallow recess, with a bit of rough casting skin left on the rim. That's as far as I could take it down without running out of material. I should have allowed more room in the casting, so I'm calling the rough edge artistic. A few of the pits made it through, too.

It shipped off to Tim shortly afterward.

Here's the wax pattern cast from the 3D print, in blue. Oh hey, it worked.

Then I tried again, with what I thought was a better sprue design. This one is printed in grey resin.

That earring is slightly convex, like a contact lens. I failed many times to cast it in brass and aluminum bronze, but I learned a lot doing it. In the end I just printed it and spray-painted it.

The next year, my younger daughter had another Pi Day earring concept in mind: a sphere made up of the digits of pi. I worked through the math for it in OpenSCAD.

This was the prototype, printed in white resin and coming together a few days before Pi Day. The design is hers.

The finished earrings were done just under the wire on March 14th. I'm not sure why she wanted black, but they are as ordered.

Here's a better picture, after she highlighted the numbers.

Another look at the prototype.

Here's the design iteration from late November: dark walnut body, a granite-looking curling stone on top, and a brass band and handle.

By the third week of December the top was made and waiting on paint.

The first route was a silicone mold. Here's the 3D-printed resin bust of Leonardo da Vinci, the blue silicone mold, and a yellow wax copy made from it. Next stop was going to be a plaster cast of the wax figure.

You can buy two-part casting silicones, but they're expensive and go bad quickly once opened, which makes them a poor choice for occasional home use. So I tried hardware store caulk as a casting medium. Straight out of the tube it's too thick to work well, but I finally hit on a recipe that is thin enough to flow around a model, cures quickly, and uses only easily available, relatively safe stuff.

The cutaway block shows that I could get it to set without voids by using a vacuum chamber. The complete mold shows that it takes detail well.

Amazing Remelt is a good product for this, but I think a homemade version costs about a fifth as much. It's just glycerin and gelatin. Here's the first experiment: the printed mold halves, with a translucent red gelatin casting between them.

And a demold success, with a teal gelatin block holding the impression of the bust next to the resin bust it came from.

The mold parted cleanly along the layer lines. There are some voids from bubbles, so I might need to refine my technique there.

Pouring the wax in stages did the trick. There is one very small area, down at the bottom, where the heat of the wax melted the mold where it was thin, but otherwise it came out great.

I think I'm done with this line of experimentation.