Weekend Project: Planter Boxes!

Last weekend I made three huge, turquoise planter boxes for my rooftop deck – check out the quarter for scale.  Naturally, help from other Makerspace members was key, as I relied on JackD and his JAMbulence for help transporting two sheets of plywood (Thanks!).  I safely sliced ’em up on the panel saw, and then glued, screwed and nailed them together.  After applying numerous coats of outdoor latex paint and a bit of sanding, they’re already in use in downtown Milwaukee!


Weekend Project: Kitchen Shelf

I’ve recently heard that the Milwaukee Makerspace has a reputation for only having members who are electronics enthusiasts. Well, in addition to the metal, wood, beerwater, whisky, fire, arduino, weldingoddaudiocasting, and numerous acoustic projects that I’ve worked on at the Makerspace, I’ve finished a few electronics projects here. My latest Makerspace weekend project is a shelf for my kitchen, pictured here with the Sad Bananaand three legged pig®.

Kitchen Shelf

Inexpensive Ceramic Shell: Aluminum Casting with Drywall Joint Compound

We’ve been aluminum casting at the Milwaukee Makerspace since November, and I have cast several things since then.  For simplicity, we started by using a lost foam casting method, wherein the form to be cast is fabricated in Owens Corning Foamular 150 (Styrofoam), and is then tightly packed in a reusable, oil bonded sand called petrobond.  The molten aluminum is poured directly on the styrofoam, vaporizing it.  Because the mold is made of sand, the surface texture on the cast aluminum part has the “resolution” of the grain size of the sand.

Ceramic shell is another technique often used in art casting.  The positive of the form to be cast in metal is first created in wax, which is then dipped repeatedly in a silica slurry, that slowly builds up to the desired ½” thickness.  The surface detail reproducible is much smaller/better, as the silica has a much finer “grain size.”  The piece is then put in a kiln to burn out the wax and harden the silica, thereby forming an empty mold.  Typically the mold is cooled, inspected for leaks, patched, and then is buried in regular sand.  Note that to avoid fracturing the mold, it must be heated before pouring.  With all these steps, this process is relatively time consuming and is also somewhat expensive.

Recently, I read a blog post about a quick and low cost ceramic shell alternative that substitutes one or two coats of watered down “Hamiltons White Line Drywall Texture mix” for the tedious ceramic shell process outlined above.  While I couldn’t find that exact product, 4.5 gallon buckets of Sheetrock brand lightweight drywall joint compound (DJC) are omnipresent.  Note that some bags of quick setting drywall joint compound are actually just plaster, and cannot be substituted. I first assembled all the parts needed to make a quick test of the process.  I decided to make some aluminum packing peanuts:


I hot glued the pyramid shaped sprues to the round cup and to the peanuts themselves:


I removed half of the 43 Lbs of DJC from the bucket, and poured in 10 lbs of water, taking care to mix it thoroughly with a spiral paint mixer connected to a drill.  Then, I just dipped the whole styrofoam assembly into the bucket, let it dry overnight, and dipped it in a second time.  Immediately after the first dip, I took care to brush the surface of any especially undercut areas, to prevent air bubbles from sticking to the surface.  In the future, I may consider pulling a vacuum on the bucket of DJC to de-gas it.  This may help prevent the formation of air bubbles on the surface of the styrofoam parts.  In addition, I could have first dipped the assembly in surfactant. After two dips, the 1/8” thick shell on the assembly looked like this:


It was a week before the next aluminum pour at the Makerspace, during which time I poured a half ounce of acetone into the mold to dissolve the polystyrene packing peanuts and styrofoam, producing an empty mold.  This step is only necessary when casting packing peanuts, as their polystyrene tends to rapidly expand out of the mold and catch fire, while the pink styrofoam (also polystyrene) is made for homes, and so is much better behaved.  I buried the now-empty DJC mold in ordinary sand, and Matt W fired up the Bret’s furnace, melted a #16 crucible of aluminum, and poured it (Thanks guys!).  After fifteen minutes, I pulled the mold out of the sand, and found the DJC was a little darker.  The act of pulling the mold out of the sand an leaving it to cool over night left it somewhat cracked:


The DJC crumbled off so easily that I didn’t even need a brush.  Also, I noticed that there is more yellowish surface tarnish on pieces left in the DJC to fully cool.  I recommend removing the DJC immediately after the aluminum solidifies.


After making a few more, I’m almost ready to safely pack valuables, such as my “Marquis, by Waterford” crystal stemware:


Finally, check out the phenomenal surface detail that this process can reproduce.  For scale, this peanut is 1.5” long.  The surface texture on the front face is about ~0.002”!


Thanks to Jason G for this last photo.  Also, a big thanks to Dave from buildyouridea.com for letting me know that one or two dips will do it!



I’ve updated Robert Indiana’s iconic sculpture “LOVE” for our times!  While “Love” may have been an appropriate sentiment from 1964 to 1970 when the 2D and 3D versions were made, I think that the revised text is more appropriate for the 2000’s and 2010’s. Fear is 8” tall and 4” deep, and while not a monumental outdoor sculpture, FEAR appears fairly sizable on a table top.

Fear, which is solid aluminum and weighs over 7 lbs, was cast last Thursday with quite a few other pieces.  The great thing about having an aluminum foundry at the Makerspace is that the whole thing cost about $7!  – $4 for propane, $1 for Styrofoam, and $3 for some Rotozip bits.  If FEAR were cast in bronze, it would weigh over 20 lbs, which would cost $200 for the metal alone.  As it is, we melted down old heat sinks, stock cutoffs and hard drive frames, so the metal is essentially free.

In the spirit of Indiana who made his own font, I drew FEAR up in Inkscape using Georgia Bold, but I increased the height of the Serifs a bit.  Shane helped me with the file manipulation and G-code generation (Thanks!), so I could use the CNC router to cut FEAR out of styrofoam.  I exported FEAR’s hairline thickness outline as .dxf so it I could bring it into CamBam to generate the G-code. The outer contour of FEAR was selected, and the following settings were chosen:

  • General -> Enabled -> True
  • General -> Name -> Outside
  • Cutting Depth -> Clearance Plane -> 0.125 (inches)
  • Cutting Depth -> Depth Increment -> 1.05 (inches)
  • Cutting Depth -> Target Depth -> -1.05 (inches)
  • Feedrates -> Cut Feedrate -> 300 (inches per second)
  • Options -> Roughing/Finishing -> Finishing
  • Tool -> Tool Diameter -> 0.125 (inches)
  • Tool -> Tool Profile -> End Mill

Identical settings were chosen for the inner contours of FEAR, with the exception of General -> Name -> Inside.   Then, I just selected “Generate G-code.”  Check out the real-time video of Makerspace CNC router running the G-code and cutting out the 1” thick Styrofoam (Owens Corning Foamular 150).

After cutting four 1” thick pieces, they were stacked and glued together.  I buried the foam FEAR in petrobond, and then attached Styrofoam sprues and vents.  For a more complete explanation of the quick lost-styrofoam casting process, check out this post.   Stay tuned for details of our next Aluminum pour, which will be in January in the New Milwaukee Makerspace!


Makerspace Aluminum Casting Foundry

I arrived at the Makerspace on Thursday without an idea of what I would cast in metal, and in less than two hours I was removing my piece from the steaming petrobond! Check out the fruit of two hours of labor cast in metal!

That’s right! The Milwaukee Makerspace had its first (and second) aluminum pour on Thursday! Thanks to the hard work of several members, the Makerspace now has a fully functional aluminum casting foundry.  The custom built propane and diesel powered furnace melted an entire #16 crucible of aluminum in less than 20 minutes.  Check out Brant’s video to see our fearless foundry foreman leading the two pours!

To get the foundry running quickly, we’ve started out by using a lost-styrofoam casting method.  That is, styrofoam is carved into the desired shape and then a sprue and vents are attached with hot glue(!).  This assembly is placed in a wooden form, and is surrounded by tightly packed petrobond, an oil bonded, reusable sand.   Then, the molten aluminum is poured directly onto the styrofoam sprue.  The styrofoam is instantly vaporized by the 1250 degree Fahrenheit aluminum, which fills the void in the petrobond formerly occupied by the styrofoam. The air and perhaps even some of the styrofoam residue escapes from the mold through the vents.  We’ll be phasing in bonded sand and lost wax casting soon, so stay tuned for those details.

Eventually we’ll be having aluminum casting classes; however, we’re definitely going to be having aluminum pours on alternate Thursday evenings for the next few months.  Join our mailing list / google group to get more details.  Metal pours are spectacular to watch, so feel free to stop by to see the action around 7 or 8 pm, or join the Makerspace and participate!