Silicon Mold Design – Lessons Learned

Soft Robots

The previous week, I learned to convert some PVC pipe, a 3D printed inner core into a mold to cast silicon in. We made an inflatable silicon actuator by adding fabric cut in the right places inside the cast.

After that, I wanted to cast my own actuator, and this time try to do a sleeker, longer version of the one last week. I decided to use paper instead of fabric, and use straws of different thicknesses to create a hollow tube, rigid in some places and inflatable in others.

My mold was made using a large milkshake straw, a thinner plastic straw, a metal stick to hold the straws in place, a base made of cardboard and paper.

Upon casting, I learned that pouring silicon into such a tiny space was impossible — at that stage I believe I wanted a funnel attached to the mouth of the larger straw.

The next morning:

After the cast has cured over night, I learned that despite using ample amount of demolding spray, it was impossible to pull it out from the tight space between the straws.

I then learned that mine was a deconstruct-able mold. I cut through the bigger straw to find out that air bubbles had formed all over the cast, and realised that instead of a funnel, to achieve this kind of shape I must have a mechanism to pour (and demold) longitudinally. Two half molds for the outer shell would have solved the problem of air bubbles.

Leave a Reply

Your email address will not be published. Required fields are marked *