Group Assignment on Moulding and casting
Group members
Week 13 – Networking and Communications (Group Work)
This week's group assignment:
- Review the safety data sheets for each of your moulding and casting materials
- Make and compare test casts with each of them
- Compare printing vs milling moulds
In the group work, we used pre-made moulds and poured liquids into them, which then hardened into casts.
Materials:
Smooth-Cast 305
Fully cured castings made from Smooth-Cast 305 are tough, durable, machinable, and paintable. According to the datasheet, this material is not safe to touch or inhale. We used vinyl gloves, lab coats, and safety goggles in a ventilated space. Eating or drinking was also forbidden in the workspace to prevent accidental swallowing. Its pot life is 7 minutes, which means that after starting the mixing of the solutions together, there is 7 minutes working time before the material hardening begins.
Smooth-Sil 940
Smooth-Sil Platinum Silicones cure at room temperature with minimal shrinkage, offer good chemical, abrasion, and heat resistance, and are ideal for making durable moulds for casting materials like plaster, concrete, wax, low-melt metals, and resins. Smooth-Sil 940 is also suitable for food-related applications. According to the datasheet, this material is not considered hazardous. However, we still used protective gear. Its pot life 30 minutes.4
Dragon Skin 10 Slow
Dragon Skin is a soft, super-strong, and stretchy material. This is also not considered hazardous, according to the datasheet.
Mixing Materials for Moulds
We mixed parts A and B of the materials according to the weight ratios written on the bottle labels. Wooden sticks were used for mixing.
Degassing
The mixed material in the cup was placed in a degassing chamber. Under low pressure, the liquid began to bubble as internal gases were released. After a few minutes, the bubbling stopped, and we slowly returned the chamber to atmospheric pressure by gradually turning the valve to the horizontal position.
Pouring
We then slowly poured the material into the mould. Below is Smooth-Sil:
And here is Dragon Skin:
Casting
Gleb had previously scanned Tuomo's head and 3D-printed it. A mould was then made by pouring a moulding liquid on top of the 3D-printed head. After hardening, the 3D-printed head was removed from the mould. We poured both Smooth-Sil and melted tin in into this cavity.
Even the layer lines from the 3D print were well reproduced with Smooth-Sil. For a higher-resolution result, resin printing could have been used. In the tin casting, the surface accuracy was not quite as good. Baby powder was applied inside the mould to create a small air gap between the mould and the molten tin. There may have been too much powder in the nose area, as that section did not reproduce well.
Summary
- Moulding and casting involved more steps than 3D printing but allowed us to produce results that would not be possible with 3D printing alone.