07 3D Molding and Casting – Experimentation Log — Anna Kaziunas France

Completed TARDIS Cast | Working Light

This project went through many adaptations and in the end, it did not turn out as a blue box, but more like a weathered garden statue. The hydrostone did not turn out completely white, but grime on the urethane molds made little swirls, further enhancing the marbleized look. It is not bigger on the inside, but the wiring and battery did fit nicely within the internal cavity. A switch turns it on and off. Although this endeavor did not turn out exactly as planned, I learned many things about thinking in 3D and many more about construction and molding objects in 3D.

So what makes this model a “TARDIS” not just a model of a British police box that looks like a light-up garden statue? Honestly, nothing but my intent. I set out to make a model of the TARDIS and that is what it will be called.

The process I used to create this model:

1. I designed the TARDIS in Google Sketchup.
> See Previous Post: TARDIS: 3D Modeling

2. I used the Modela to mill out the front, 3 individual sides and roof of the model in machinable wax.
> See Previous Post: TARDIS: Moldmaking

3. I used the block of machinable wax to create urethane molds of each of the pieces.
> See Previous Post: TARDIS: Moldmaking

Laser-Cut The Casting Container:

4. I designed and laser cut an adjustable press-fit box to place the individual urethane molds in order to cast the TARDIS in hydrostone. (I also custom-cut shims to key in the urethane mold edges.)

Putting Together the Casting Container / Aligning the Mold:

5. When casting, I did my best to align the sides and roof together at the appropriate angles and hoped for the best. An additional laser-cut box with an empty pen casing was inserted into the larger mold when pouring the hydrostone in order to create a cavity for the wires to run form the LED on the top through the cast down into the base where the wiring, battery and other components are housed. The inside box then became part of the cast.

Removing the Casting Container:

6. When taking apart the mold, I found that some of the fine details of the windows and the moldings became stuck in the urethane mold or broke off easily. I may not have mixed the hydrostone long enough, or there may have been an issue with the proportions I used. Further experimentation is this matter is needed to determine the source of the problem. This breaking away of the fine detail gave the statuette a weathered appearance, like a tombstone left out in the elements.

Adding the Electrical Components:

7. In addition – I wanted to have a LED light on the top to simulate the police box light, so when cutting the outside casting box, I cut a congruent interior box (see number 4. pictures above.) This small inside box allows for an open area for the wiring from the LED through the top of the hole in the stone to the battery. The wiring consists of:

1 ultra bright white 10 mm LED
1 330 ohm resistor
1 small switch
1 battery connector and a 9V battery
A few lengths of wire

I dedicate this project to David Tennant for his the excellent portrayal of the 10th Doctor, which has just come to an end.

Image © BBC

TARDIS: Moldmaking

I am still working on my Fab Academy 3D Molding and Casting project (a 3D model and cast of the TARDIS. The implementation of my model proved complicated.

The Fab Academy Assignment

Machine a mold and cast parts in it

The Project: TARDIS multi-mold cast

Starting with the cad.py created .rml files (for details on the 3D modeling process see my TARDIS: 3D Modeling post), I carved several molds out a block of machinable wax using the Modela milling machine.

Wax Molds

There were a few mishaps creating these molds. The z-max setting was not high enough on the side mold (you can see where the Modela bit drug through the wax and made lines that were not part of the design.). I learned that it pays to set the z-max close to the max of 1 so that it will clear the edges of the design. However, because this particular design took so long to mill out , 7 hours or so, I opted not to redo it if the damage was minor. Instead, I attempted to repair the damaged areas with wax.

After I made the wax molds, I made casts of each side and the roof using urethane rubber. The door was cast once, but the side needed to be cast 3 times to create the 3D object.

I did not allow for space at the top of the wax molds, so to ensure that the rubber would have enough room to capture the top of the design, I laser-cut some tempered masonite frames in to increase the vertical space for the rubber to fill. These frames also make it a little easier to get the rubber out of the mold.

Creating and Gluing the Frames

Mixing Urethane / Creating the Molds

At Fab Academy Providence, we used a smooth-on 2 part urethane mold mix. Just mix equal parts of each container (A and B) and mix slowly in a figure eight pattern to minimize the bubbles.

What I learned about this material:

Mix very thoroughly. Take your time (at least 10 – 15 minutes if you can stand it). The end result will be sticky if the parts are not mixed together well – My first two molds were sticky.)

Add heat. Heat both accelerates the process and creates a less sticky end product. I used a desk lamp positioned in close proximity to the freshly poured mold.
Be careful not to leave the heat on longer than 15 minutes or so and let the wax and rubber cool before removing the rubber mold from the wax.
I learned the heat lesson the hard way when my mold melted from excessive heat. (see photos below)

Beware of Melting Molds

All The Molds (Good and Bad)

Skills Learned

Tools Used

Next Steps:

Create a box and system for keying in the sides of the police box so it can be cast.
Get LED, resistor and battery to wire up the light on the top.
Cast in hydrastone