posts tagged with the keyword ‘molds’


Concrete Hammer

It’s been nearly a year since I introduced The Ice Hammer to the world, and yes, I’ve been accused of having an obsession with hammers, but I swear this time it’s (mostly) a coincidence.

The gang at BBCM are doing a MakeShift event this week titled Concrete Mixer, which is an adults-only thing at the children’s museum, and the topic is concrete. Instead of just being jealous of what the BAM folks have been up to with casting concrete in foldable paper forms and digging into the concrete/art connection, I decided to get in on the fun as well. John’s been busy casting concrete too, and he gave me a can of concrete to play with.

So how could I not use the vacuum formed hammer mold I made at a previous MakeShift event to create a concrete hammer?

Concrete Hammer in mold

I’ve been traveling a lot for work, and I knew that concrete takes some time to set and harden, so I was in a rush to mix it up and get it into the mold before I left town. I frantically mixed and scooped the concrete into the mold at about 10pm before rushing off to bed for an early morning flight.

Concrete Hammer (Head)

Air bubbles and lumps? I’m sure there’s a few… But the important part was that I got it ready to sit around and dry for a week.

Concrete Hammer

When I got back I took a look at the surface and it looked pretty solid, but I still didn’t trust it was fully set, so I let it sit for another day. Getting it out of the mold proved a bit tricky. I had taped up the cracks in the mold that occurred the last time I made an ice hammer, and that made it a bit more stiff. I did manage to get it out, but I ended up destroying the mold. No more ice (or concrete) hammers!

Hammer Mold

Even though it’s concrete, I’m pretty sure one good swing would destroy it. For now I’m just going to consider it an art object, and not a fully functional hammering device.


If you’re available Thursday, February 4th, 2016 and want to learn more about working with concrete, plan on attending MakeShift. Tickets are $10 and you can get them online. (I hear there will also be “spiked milkshakes” and other refreshments.)


I’ve been digging into OpenSCAD lately and managed to come across this Flickr photo with the most minimal of explanation of how to do a reverse object in OpenSCAD, but it was all I needed…

Space Invader SVG

I started with the SVG file of the classic Space Invader character, sized to the width and height I wanted, and then exported it from Inkscape as a DXF file.

Space Invader STL

Once we’ve got the DXF we can pull that into OpenSCAD and extrude it into a 2.5 dimensional object. (It might be 3 dimensional, but I’m not going to argue 2.5D versus 3D right now.)

linear_extrude(height = 10, center = false) import("spaceinvader.dxf");

After we compile the code we can then export our object as an STL file. We can then pull that STL file into OpenSCAD again for the next step…

Space Invader STL (reversed)

difference() {
		cube([90,70,14.5], center=true);
	# import("spaceinvader.stl", center=true);

You’ll need to tweak those numbers of course, and as for the # at the start of the import line, that’s to show us the object even when we can’t see it, as it were… sort of. It’s an OpenSCAD trick I learned from Mark Finn at BarCampMilwaukee.

So now that we’ve got the object dropped into a block (at the proper height) we can then export it as an STL file, which could be cut on a CNC machine, or 3D printed.

Space Invader G-code

I’ve not yet attempted to 3D print this, and I’ve had not much luck in printing things that are water-tight. I might try getting some silicone to coat the piece which would make it water-tight, and food-safe.


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