WEEK17 WILDCARD

For this week's assignment, I’ll be making a mold again, but this time using 3D CNC milling.

I downloaded Michelangelo’s David sculpture from here.

MODEL PREPARATION:

In Fusion 360, I created a negative mold that I’m going to cast using artistic plaster.

And here’s the final model:

DRAFTS & OVERHANGS

In Fusion 360, we can see the drafts that will determine if the cast can be retracted, as well as check whether the tool will hit any overhanging material.

In my case, I have some overhangs and draft issues, but they won’t be noticeable. Most of the problems are in the hair area — which will still look like hair anyway. The cheek and nose will just become slightly larger, and the flat part will be just fine.

MANUFACTURE PROCESS

The manufacturing process is the same as the one I used in WEEK 7 for 2D CNC cutting, but this time I’ll use 3D milling.

I’m going to use ADAPTIVE CLEARING with a FLAT ENDMILL to remove most of the material.

And then MORPHED SPIRAL with a BALL ENDMILL for smoothing the surfaces.

Since we didn’t have this endmill installed in the program, I had to add it first:

You have to measure the tool with a caliper and add all the dimensions.

Then follow the setup process:

CNC MILLING:

As my mold material, I’m going to use blue EPS polystyrene, 50 mm thick.

I glued two panels together (which wasn’t necessary) and screwed them to a wooden plank to provide grip for the clamps.

ADAPTIVE CLEARING:

MORPHED SPIRAL :

MOLD PREPARATION:

CUTTING OUT THE MOLD

I cut out the piece I needed using an X-Acto knife, and later used a hot wire cutting tool.

The previous tool wasn’t very precise, so I used a hot wire station for straight cuts.

STYROSPRAY LAYER

To finish my mold, I added some cardboard and prepared StyroSpray as a protective layer.

StyroSpray 1000 is a two-component, moisture-cured polyurea hard coating developed by Industrial Polymers Corporation. It's designed to create a durable, waterproof, and impact-resistant shell over expanded polystyrene (EPS) foam and other lightweight substrates. This makes it ideal for applications such as signage, scenic props, architectural theming, papier-mâché structures, and concrete molds.

• Component A: Typically an amber-colored liquid with a syrup-like consistency.
• Component B: A white, thick, and sticky substance, similar in texture to honey.

DATASHEET

Mixing Ratio: 1:1 by volume. After thorough mixing, the resulting blend has a consistency similar to house paint.

Key Features

• Application Methods: Can be applied using a brush, roller, or low-cost gravity-feed hopper spray gun.
• Curing Process: Begins curing upon exposure to atmospheric moisture, becoming dry to the touch in about one hour. Full curing occurs overnight.
• Layering: Successive coats can be applied every 2 to 3 hours, allowing for significant buildup.
• Composition: 100% solids formulation with no solvents or VOCs, making it environmentally friendly and nonhazardous for shipping.
• Durability: Creates a hard, smooth surface that can be painted with either solvent or water-based paints.

The mixture seemed too thick for my mold and I would lose all the fine details.

I tested it on some foam leftovers to see how the layer would look, but for my David mold, I’ll look for another solution.

Here’s how it looks after drying:

CASTING:

PLASTER PREPARATION

For the cast, I’m using artistic plaster.

I was thinking of putting it directly on the foam but apperently it will stick to is very well. I have two homemade solutions:

soap or olive oil and I feel the fat is better so I’ll use it (I found out later that soap was actually a better choice specially for plaster molds)

It literally took 2 minutes to spray it, and my mixture hardened like a rock...

The box said I had 15 minutes of working time — maybe that’s from the moment you open the box 😅

Well… this was torture and made a big mess to remove.

Here’s a new mixture:

FINAL RESULT

The cast came out very well. I’m actually happy with the result.

I should have used a different material for the walls instead of cardboard — it got wet, oily, and stuck a bit too much.

But with some water and a small brush, it should be easy to remove.

FILES:

MOLD NEGATIVE

• david.zip

CHECK LIST:

Design and produce something with a digital process (incorporating computer aided design and manufacturing) not covered in another assignment, documenting the requirements that your assignment meets, and including everything necessary to reproduce it. Possibilities include but are not limited to wildcard week examples.

Learning outcomes:

• Demonstrate workflows used in the chosen process
• Select and apply suitable processes (and materials) to do your assignment

Have you answered these questions?

• Documented the workflow(s) and process(es) you used
• Explained how your process is not covered on other assignments
• Described problems encountered (if any) and how you fixed them
• Included original design files and source code
• Included ‘hero shot’ of the result