Soft Robotics

This week I designed a 3D printed mould of a gripper with 3 legs.

To create the mould I used Fusion 360.

First I created a 2D design of on leg of the gripper. Then I extruded and cut to create the negative 3D mould of the leg by creating round ages near the ground in order to remove the silicon material later easier. Then I created the positive 3D lines in the middle of the leg, which have a shorter height than the sides of the gripper. Then I created 2 more copies of this first leg in a 120 degree angle in relation to the first leg so they could create the shape showed in the picture. I connected the 3 legs together by creating a short angle between them. This angle was taken from the length of the legs that is why the other 2 legs look shorter than the first one. In the middle I created a circle and connected it with the insides of each leg. The circle has same height as the inside lines of the legs. Then I printed the mould using normal PLA.

We used Ecoflex A and Ecoflex B to create soft grippers. We mixed the 2 parts in a 50:50 ratio and stirred of 2 min.


I then poured the mixture slowly into my mould trying not to create bubles and to share it even.

Then in a flat plate of glass we created a thin layer of silicon in order to put it later on top of the gripper so we would have a close patter. Together with our moulds we put also the flat plates into the oven at 70 degrees of 15 min in order to speed up the drying process. After that I tried to carefully remove the silicon from the mould. This process was slow and need to be done carefully in order not to destroy or make holes in the silicon. Took around 1 hour.

Then I glued together the soft silicon layer with the body of the gripper by using the same mixture of Ecoflex as glue. Again I put them in the oven with same features to make the glue dry quicker.

When the body of the gripper was ready I inserted a needle into the center of the gripper. Then I connected the DC air pomp through a tube with the needle.
After many failed attempts to inflate the griper I saw a hole in one of the legs. Then I tried to inflate it again by trying to block the hole with a finger and it worked. I created a video.