Anna Aflalo

Fab Academy 2015 | Wgtn

WEEK 12 | Composites

Hydrostone & Rag
Daniel, Bridget and I decided to start this week by making some composite tests on Wendy's wood design. Daniel had the great idea to vacuum form the piece of wood (we didn't want to damage it). We had some concerns about one sharp angle. So we used two little pieces of wood to protect the plastic from it (see photo above). All the details were transferred on the plastic mold so we could move on to the casting.



The ratio was 32 parts water for 100 parts plaster by weight. We decided to use a brush to spread the plaster. We realised that we should have poured more plaster in the mixture. We had to take out some liquid in order to stick the rag to the mold otherwise it wasn't a big issue.
The cast took two days to be completely cured and we had to break the mold in order to take it off. The result looks indestructible and we still have all the details.
Sugar & paper


I wanted to test sugar as a matrix. It was my first caramel and I discovered that sugar becomes hard very fast! Indeed I made a mess and the result isn't very pretty but I had a lot of fun.

For next time:
- Don't burn the caramel (because it smells bad),
- Maybe use a smaller mold,
- Use a material smoother than paper.
Rice paper, jute & hot water
This test was promising so I was curious and I decided to do more tests with the rice paper.
Week Assignment
I didn't find a use in my final project for this week assignment. So I decided to play with Grasshopper and make a parametric rosace. I followed this very well made tutorial and played with different shapes.
I milled it in wax with the Roland MDX-40 machine. And I had some issues with the finishing path. I wanted to check the mold during the milling so I pressed "View" and opened the lid. Apparently, you have to wait until the light stops blinking otherwise the machine enters "emergency mode". And that is what happened... So I had to restart the job from the beggining. Daniel told me that I could mill faster. The thing was that I didn't save the job's file in SRP Player so we couldn't change the feed rate. We had to guess my previous settings, not an easy task. I was glad to have Bry and Daniel in the lab.

Rough cut drill bit: 1/8"
Finishing cut drill bit:1/32"
Download the STL and Grasshopper files here.
Test 1: Rice paper, linen & hot water
I left the composite is the vacuum bag only few hours. But the paper rice took two days to cure so the details at the end of the rosace were not what I expected.

Test 2: Rice paper, chiffon & hot water
I chose chiffon instead of linen because it's thiner and I was hopping to see more details. I left the composite to cure totally in the vacuum bag. With these two modifications from Test 1, I had a much better result with the details. But a few days later I realised that the composite started to bend and loose its curvy shape.

Finally, I decided to make a test with the resin.
Resin and chiffon

The composite is more reliable with resin (even if its much more fun to play with rice paper). The result is smooth and it doesn't bend. Otherwise the precision of the details is similar to the second rice paper test.





Second rice paper test and resin test results.
CarboGlass visit




Fab Lab Wgtn and Massey University 3D Workshop organised the visit of a composite factory. It was very useful, we had a better idea of what a composite is and what we could do with it. These pictures show one of the two techniques we've seen.
This is the workflow:
1. Spray some glue onto the bottom of the mold,
2. Place the carbon sheet on it, be careful with the angles,
3. Spray "vacuum Infusion Enabler" (this glue is pigmented so he didn't use it on the bottom layer),
4. Repeat 2 & 3 few times,
5. Spray some pigmented glue and add a layer of cloth,
6. Place the green mesh: it'll help the resin to spread up faster,
7. Close the vacuum bag and start the extraction
8. Wait at least 10 minutes
9. With the second tube, put the resin into the bag. It'll spread uniformly over the top of the composite.