Wildcard Week

Reflection

Shell making is a difficult process, especially for the soft shell. I'm trying to make one for my final project. If I follow the normal process, it is a huge project and very time-consuming. But I found a quick eggshell-making process, which is more suitable.

I started with a simple shape, and the result was good. Then I tried to make it more complex by cutting some patterns on the surface. However, it was hard to cast and demold. I need to try another method.

Practices

I used a shell-shaped lampshade in my final project. I want to make it with silicone by casting. During Wildcard week, I plan to try the 3D print Eggshell casting method, which I haven't attempted before.

Eggshell Casting

Research

Eggshell modelling

3D print Eggshell modeling uses the lost mold method to create shell-like objects. First, a 3D model of the object is created and a 0.4mm shell is extracted. The thinnest possible outer wall is then produced via 3D printing. Next, a silicone mixture is poured into the cavity gap. After solidification, the mold is directly broken to take out the finished product.

eggshell.webp

Advantages

  • High Precision
  • Support Complex Shape
  • Fast

Disadvantages

  • Single-Use Molds
  • Fragile Molds
  • Limited Production Scale
  • The 3D printing trace will be cast out.

3D modeling

Base the final project I creat a shape of mold and set the cut gap for it.

w17_001 w17_002 w17_003 w17_004

The Puring gap is too narrow, then I add a funnel shaped opening to enlarge and avoid the leak the liquid.

w17_005

3D Printing

w17_006 w17_018

Casting

Addition-Cure Liquid Silicone Rubber (LSR)

  • Bottle A (Base): Vinyl-terminated polydimethylsiloxane (base polymer) and fumed silica (food-grade reinforcing filler).

  • Bottle B (Curing Agent): Methyl hydrogen silicone oil (crosslinker) and platinum complex catalyst.

Component A (base glue) and Component B (curing agent) are mixed in a ratio of 1:1.

Shore hardness is 30A Taobao link

w14_021

The cut inside is hard to cast. The liquid is hard to reach the every conror. Fist I try a shape without the parttern. w17_007 w17_008

Because of the complex pattern, it is hard to continue. Then I try some simple line, but still, the pouring is good, but it is hard to break the outer cage. Maybe next time I need to try PVA that can melt in the water. w17_019

Demold

Demold process is like peeling the eggshell w17_009

Result

The shape is out but very small bubble can't remove. w17_010 w17_011 w17_012

Files

skin.3mf

skin.stl