WEEK 11: Molding and casting
Group assignment:
For the group assignment we conducted several tests with the products available at the lab. We grouped the information collected in the following table. It was the occasion for us to understand the specificity of each product and see how one or the other would match the need of the design we want to do for this week assignment.
TINSIL 70-60
First we tested TINSIL 70-60, but as the ratio was 5 to 100, we must have made a mistake and the misture cured before the expeted pot time so it was not possible to use it.
Safety:
Part A:
The part A is Flamable, toxic, skin corrosive, and causes damage to acuatic life.
Part B:
The part B doesn't have any GHS labels, but it says that it may cause mild eye and skin irritation, and recomends to avoid contact with eyes and mucous membranes.
PLASTIL FS-20
We also tested the PLASTIL FS-20, a regular molding silicone with good quality and fast curing. We mixed it with the drill and the we poured in the mold. It cured fast and gave us a good quality mold.
Safety:
The product is not hazardous, but it says that it may cause mild eye and skin irritation, so it's recommended to use it with gloves and safety glasses.
FOAM-IT 4
Then we tested the Foam one, that has a hight expansion and it's so light. We tested it on an existing mold, that we clamped and the we poured the mixture in. After a while, we saw how the mixture expanded and went out of the mold.
Safety:
The product is harmful and hazardous. It can cause skin irritation, eye irritation, allergy, respiratory irritation among others.
EASYPLAST 00-40
I tested this one for my individual assignment.
Safety:
It doesn't have safety datasheet, and in the technical datasheet it says that is not toxic, so it's supossed to be no hazardous.
ACRYLCAST
I used Acrylcast to cast my individual assignment.
Safety:
As the previous one, it doesn't have any safety datasheet, and in the technical datasheet it says that is non toxic, so it's supossed to be no hazardous.
Casting with low temperature metal
To cast, we tested a low temperature metal that we casted on a TINSIL 70-60 mold, because it can resist the heat. We melted it in the oven (better not to do this) and the we poured it. It was easy and the result was quite good and accurate.
Individual assignment
For the individual assignment I designed two molds.
First, I designed a kind of a soap holder in Rhino. The idea is that you can put the soap in the tilted surface and the water would go down to the base.
I also wanted to try to encapsulate a PCB, so I decided to also make a mold to do it with the following PCB I've made in the electronics design week.
I had a block of machining wax, so I had to fit both molds in the block in order to mill them
I pasted the block to the base of the milling machine with double side tape
And then I started doing all the process with MODELA Player 4, the software we have in the lab to control the machines.
First, I imported the stl file that I exported in Rhino.
Then I selected the machine in the menu (Roland SRM-20 in my case)
I set up the dimensions of the model and the origin point
And I created the endmills and assigned the parameters for each one. In the end I used a 1/8 flat and a 1/16 also flat.
Then I started creating all the processes. First, I made a surfacing of 3mm to get the top surface even
After the surfacing, I created the roughing where I defined only the neccesary area around the piece. I did this with the 1/8 flat endmill
And lastly I created two finishings, one with an 1/8 endmill and another one, only in the upper part of the piece with the 1/16 endmill
After I had all the processes created for both pieces, I exported them to files that I was able to launch one by one from the CNC software.
After setting the Z and the X/Y origin, I started cutting. First the surfacing:
Then the roughing:
And finally the finishing. This is the final result after milling the two pieces in the same piece of wax:
After having the wax molds, the next step was to make the silicone mold for the soap holder (because it was though to be made with a hard material), and to cast the silicone to encapsulate the PCB directly in the wax mold (because the silicone is soft).
First of all I measured the volume of silicone I needed to fill the mold up. To do so, I filled it with water first and then I measured the volume of water.
Then I sprayed the mold with mold release
Then I mixed the two components of the silicone. The ratio was 1 to 1 in volume.
And lastly I filled up the mold by pouring the mixture into the mold slowly and smoothly in one corner, leting the silicone fill the mold up by itself.
Then I let the mold cure until the next day. The final result was really good, and I felt so happy with the ease of the material.
To make the piece itself, I started using Hydrocal: https://www.feroca.com/es/escayolas-yesos/348-hydrocal-white.html
Again, I measured the volume of the silicone mold with water, and the I mixed the hydrocal with water
And I added a bit of blue colour
Lastly I poured it into the mold and wait for it to cure
The final result was good. However there were some air bubles that got trapped.
To test another materials, I also gave a try to the Acrylcast: https://www.formx.es/downloads/acrylcast-td-en.pdf, wich is a mineral/acrylic - casting and molding system
The mix ratio was 40 grams of liquid to 100 grams of powder
I added a bit of green colour as well. I painted the inside of the mold with a bit of the casting material because it says so in the datasheet, and then I poured the mix.
To finish with this mold, I made a third test trying to pour hydrocal with different colours (white and organge-ish).
The final result and comparison of the three tests:
To encapsulate the PCB I used Easy Crystal, because I want to try it and because it says that is suitable for that in the datasheet: https://www.feroca.com/es/index.php?controller=attachment?id_attachment=439
First I mixed the two components (A and B) in a proportion 1:1 in volume
Then I mixed well both together
As I saw that it had some bubbles, I decided to degass it (in the datasheet says that its recommended to degass it for 3 minutes).
After the degassing, the resin was perfect. To finish I poured the mixture in the mold, first a little bit without the PCB and then i put the PCB in the mold and poured the rest until cover all the components except for the button.
After letting it cure for 5 hours, it took it out of the mold. It was tricky and I had to use a cutter knife... That's why the resin broke in one side, so the result was not as good as expected...
But after testing its operation in the dark, I felt better because it looks so cool with the LEDs. So it's likely I'll give it another try.
Conclusions:
Although I've heard a bit about molding and casting and the stuff you can make, I was greatly surprised getting to know all the different materials and thechniques that exist to make almost anything.
Considering that in the field of architecture, models is something that we usually make a lot, I couldn't believe that I didn't try anything of this before, but I'm sure I'll keep practising because the possibilities are almost infinite.
Files:
Rhino file of the mold
STL of the mold for milling
Hydrocal datasheet
Easy Crystal datasheet
Acrylcast datasheet