Jeremy Grandclaudon Fab Academy 2017

Moulding and Casting :

let's mold a cat!

Assignment for this week

Design a 3D mould, machine it, and cast parts from it

----------------------------------------------------------------------------------------------------------------------------------

What I have done?

Specific material and softwares used during this assignment

- Material :
- 1 flat mill 4mm
- 1 flat mill 8mm
- 1 piece of extruded Polystyrene
- CNC Router High-Z
- Sicovoss : Silicone for food friendly moldmaking - Several screws
- Cardoard
- Software :
- Fusion360
- WinPC-NC

Source files for this week.

Designing and machining the master mold

For this assignement, I have decided to make a mold in order to produce chocolate cat! The master mold will be make from extruded polystyrene and machined with a CNC
I have made my design on Fusion360 :

The cat was made from a 2d drawing and was quicly extruded with the base

The mold can be make in two pass. One to machined the cat and the second to extract the mold from the main body. For more detail on the CNC process, check the assignment n°7

Prepping the mold for casting

I have now my master mold, I can produce the silicone mold. I will set-up 4 pieces of cardboard with to create the formwork around it

Now that's the fun part : I have to find the right amount of silicone to fill the mold. The final mold needs to be at least 10mm thick to ensure that the mold doesn't tear.
I can use Fusion 360 to get the answer but let's try it the old fashion way.

I'm using rice to determine the needed volume of silicone. Spoiler, it's 250ml

Now that I have that quantity, I also know that I need 12.5ml (5% of the amount of silicone) of silicone hardener I need to put into the mix.

The downside of this kind of mold, it take 24h to harden

Release and first try of the mold

24H later, It's time to see if everything went fine. I was a little stressed :)

So far, so good! The cardboard is oddly easy to remove

Everything went fine except the tail in the master mold is broken

It's time now to test the silicon mold and what's better than chocolate? I will try to produce a chocolate cat from the mold
I'm not a very good cook but let's go!

I'm melting the chocolate via "un bain marie"

The silicon mold handle easily the hot chocolate

In order to speed-up the process, I have put the mold in the freezer, again no issue with the mold

The cat broked during the unmolding, I should have let it cool longer and maybe put an unmolding agent before

Lessons learned and possible improvements

Now that I understood and tested the whole process, It much easier to see the flaws of my firt mold :

I should have design the mold in full 3d not in 2.5d
During the design, I have to think how to avoid any sharp line or form,like the tail of the cat, to facilitate the unmolding
I don't need to make the mold so thick, next time I can save some material (quite expensive by the way)

Update

During a review, my instructors have pointed out that my master mold (the cat) was in 2.5d and not 3d.So I have use something in 3d (yeah for the kiwi and thanks Ben!) and the same teps have been taken in order to complete the assignement at 100%.
Once the mold is dry (24h), I will updated the page :)

As you can see, the kiwi is made with several level of depths

Date: April 2017