Instructables
Picture of Cement Skulls!!!
I've been wanting to do some cement sculptures for a while now. I wanted a fairly simple,
yet still cool, design for my first project. After looking through Thingiverse I found
http://www.thingiverse.com/thing:36110 by macouno. It is simplified but has all the major
features that make up a skull. It was also complex enough that I got to learn a little bit
about Autodesk Inventor's Mold Making features to help me figure out the parting lines.
(this is NOT a tutorial for Inventor Mold Design, I only learned a little to get me
through the steps of making my parting lines).

I used:

TechShop San Jose!
Autodesk Inventor
Thingiverse
MakerBot Replicator
Cut3D
ShopBot
MDF
Filler Primer
Lacquer
Silicone Spray lubricant
gorilla tape
Quikrete
Bar clamps
Deadblow hammer
sand paper and files
Durhams waterputty
 
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Step 1: Design the Mold

After I downloaded the .stl file from Thingiverse I opened it in Autodesk Inventor 2013.
Using the mesh enabler (found here: http://labs.autodesk.com/utilities/inventor_mesh)
I converted the skull to a solid. Then I made a cube, totally surrounding the skull with
one side flush to the base (a new solid). Using the combine feature I cut the skull out of
the cube, leaving a hollow cavity. On the base of the cube I did a simple sketch to make
split lines for the 3 part mold. I also made a split line on the back side. And lastly,
the most complex parting ling was made on the side wall. First I split the side to make a
front and back. Then split the back side in half to make the three parts.
Once the three parts were made I used Create Mold Design to analyze each part of the mold
to determine if there were any undercuts. Since I eyeballed the parting line on the side
wall I knew that if any changes needed to be made all I would need to do was edit the
sketch that made that split. In Mold Design, using Adjust Orientation, I selected the face
where the skull will be removed and looked to see if any undercuts were detected (they
apear as blue faces). Once everything was green I was mostly satisfied.

Many thanks to macouno for posting Lisa the skull to Thingiverse.
found here:  http://www.thingiverse.com/thing:36110
I really want one of these. So cool. Unfortunately beyond my crafting abilities =(
J-Five1 year ago
Cool!!!

At least your tring to get a-head in life.
wilwrk4tls1 year ago
I'm not sure how you shook the mold, but if you shook it by hand... Something I saw on TV for getting bubbles out (without actually using a concrete vibrator in the concrete) was to use a sawzall (or a jigsaw may work) without a blade in it, and put the shoe of the saw on the side of the mold and run it. This will vibrate the cement pretty well and help to remove the bubbles.

What version of Inventor did you use that has the mold tools?
TSSJ-ryan (author)  wilwrk4tls1 year ago
using Inventor Professional 2013
BeoWulfe1 year ago
Those pesky kids will think twice before molesting my lawn once I've installed my mountain of skulls retaining wall!! MUAHAHAHAA!!!
odiekokee1 year ago
Do you have STLs available of either size of your mold components?
TSSJ-ryan (author)  odiekokee1 year ago
http://www.thingiverse.com/thing:48134

=D have fun
Thank you!
lsf1 year ago
You should use vibration to remove air bubbles.
correct, and it is as simple as holding a vibrating palm sander against the mold when pouring slowly, or on the mixing container before pouring.
An easy way to remove the air bubbles when fulling mold is to use a palm sander, without sand paper, against the side of the mold. Nice project. Cheers!
TSSJ-ryan (author)  Lectric Wizard1 year ago
thanks! will have to try that next time
togo19191 year ago

Rocky sure is a quiet guy...
You've made some good looking "background" skulls. I think you might be able to use these as an edging for a lawn or embedded into a fireplace.
dreamberry1 year ago
i MUST make a concrete skull for my yard. i WILL make a concrete skull for my yard. I am so serious about this.