The 3D Print
For this week, I wanted to gain an understanding on the thought process and the reactions to be able to mold & cast moving forward comfortably. I decided to make a paper weight as my first object. I simply designed it on Rhino and printed it on an Ultimaker 2+ using White PLA, 2.85mm. The materials to be used are: Oomoo 30 silicone rubber and Smooth-cast 326 liquid plastic.
The Steps
Step 1:
The first thing to do once the object is printed is to set it up in a container to pour the silicone rubber into. I hot glued my object onto a foamcore piece making sure there are no spaces underneath. Then, I cut a piece of a plastic water bottle and superglued it around the object on the same foamcore keeping a good 5-10cm above the end of the 3D printed object (it will be the base). Once it is glued, I used a piece of non-hardening clay and sealed off any section of the "wall" that could have let the silicone seep through.
Step 2: Prepping
Once everything is glued well and dried, I sprayed the enclosure completely with Smooth-On Mold Release to make sure that once the silicone mold has cured I can easily remove it without having leaks or tearing parts apart. You don't necessarily need a lot of the mold release, but you do however need to make sure that the spray gets into all the niches of the object so make sure to rotate the enclosure well why you are spraying.
Some Instructions on using the Mold Release:
- Shake well before using.
- Hold can 12 in./30cm. from surface to be sprayed.
- Apply a continuous light mist coating to model or mold surface and surrounding forms.
- You are now ready to apply mold rubber or cast into a cured rubber mold.
Step 3: Measuring & Mixing
The next step is to mix the liquid plastic parts A and B separately and then together before pouring them into the enclosure where the reaction will take place over a period of time.
Oomoo 30 is an easy to use tin cure silicone rubber compound that features a convenient one-to-one by volume mix ratio, it has low viscosity for easy mixing and pouring, and cures at room temperature with negligible shrinkage.
Measuring & Mixing
Once you open the containers A and B, use a long wooden stick and mix each one separately in their own containers. Once they are stirring smoothly, you can pour equal amounts of A and B in a cup before pouring them in one larger cup. Once they are poured into the same cup, you will need to mix it thouroughly for approximately 3 minutes. Make sure that you scrape the bottom and sides to make sure nothing is stuck.
How do I know that I am done mixing? When you see that the mixture is uniform in color, with no colors streaks.