Week 6

Casting and Modeling

Mill it, cast it, mold it - that was the theme of this week! It's time to learn how to make a mold and cast into it.

What am I building?

Well I first wanted to 3D scan a silkworm and then make a mold. That idea failed:

Big surpise. The silkworm moved too much and the scan didn't work. So, instead I decided to make a mold of Grumpy Cat:

Mill the mold

Lucky for me, Thingiverse user, Filopat, recently uploaded a large 3D STL of Grumpy Cat. Check it out here.

The first thing I did was pull the STL into Net Fabb and slice and dice a bit to just grab Grumpy Cat's face.

Next step - milling the mold on the tabletop ShopBot. Pro-tip: if you're using a tabletop ShopBot with PartWorks, use Jin Joo's amazing tutorial.

A couple mistakes I made:

When hot gluing the wax piece to the wooden board, go for a Goldilocks amount of glue. Enough to stick it on but not too much. I used wayyyyy too much hot glue and it was difficult to unstick the wax block from the wood

Handle with care. I broke the side of the mold.

If you break the wax mold, hot glue is your friend.

I figured out later that I should have "extruded" the 3D model a few additional mm's behind Grumpy Cat's face to create a base. You'll see later that the casted ears were very thin.

Making negative molds

Oomoo is magic. I wrote a tutorial on how to cast with Oomoo, which is available here.

I wanted to experiment a bit... so I 3D printed a small version of Grumpy Cat on the Form 1 printer to make a high-temp mold out of MoldMax60. I took a small plastic solo cup and epoxied the Grumpy Cat 3D print to the bottom.

Not bad! It came out better than I expected and was ulta-quick to make.

Casting

First up: Drystone. Which ended up being a big fail.

The ears were too thin for Drystone.

Time to switch to metal. With the help of Sam Calisch and Basheer, I casted babbitt into the mold. A sweet tutorial (not written by me) on how to do this is available here.

To get off all the gunk, Sam helped me use the sandblaster.

The resolution of the babitt cast was low but at least I now have a Grumpy Cat paperweight. I think the sandblasting is partially to blame for the low-res; we also blasted off parts of Grumpy Cat's frowny face!

Last but (definitely) not least! SmoothCast.

BOOM! Now that's what I'm talking about. The SmoothCast was perfect. And with a pot life of 3 minutes and casting time of 5-15 minutes, it's super fast!

I think the SmoothCast Grumpy Cat is a little more angry than grumpy. Alas.