Week 8 – Soft Robotics¶
Assignment¶
Design and fabricate a soft robotic system using flexible materials and pneumatic actuation.
Initial Design & First Trials¶
A first soft robotic design was planned.
Initial mold-making results were not successful, so this design was abandoned.
Reference Research & Model Selection¶
After reviewing previous Fabricademy works shared by Fabricademy 2024 alumna Aslı Aydı Aksan,
a mold model originally created by Samson, a Fab Academy 2023 student, was selected.
3D Modeling – Blender¶
The model was imported into Blender.
Without changing the main structure, a closure system and air inlet were designed.
Boolean operations were used to simulate silicone-filled areas between mold parts.
The final design was exported as an STL file.
Mold Fabrication – 3D Printing¶
The mold was prepared for 3D printing on an Ultimaker printer.
Print settings
- Material: PLA
- Nozzle temperature: 200 °C
- Bed temperature: 60 °C
High acceleration was avoided to preserve mold surface quality for silicone casting.
Silicone Casting Process¶
RTV-2 silicone and catalyst were used.
Even with small quantities, accurate ratio measurement was critical.
Key observations: - Silicone must reach small details - Air bubbles should be removed with a pin - Casting surface must be completely level - Full curing time must be respected - Sharp tools are required for trimming excess silicone - Continuous cleaning during casting is essential
Assembly & Air Inlet Integration¶
After curing, the silicone parts were removed from the molds.
Two silicone parts were bonded together using freshly mixed silicone.
An additional small mold was used to reinforce the air inlet, ensuring a strong pneumatic connection.
Equal silicone ratios were maintained to preserve uniform flexibility.
Final Soft Robotic Actuator¶
Initially, a wrist-wrapping soft robotic system actuated by a pear pump was planned.
Due to difficulties in achieving a sufficiently thin silicone structure, this concept was abandoned.
Instead, a previously tested soft robotic structure from Fab Academy references was successfully fabricated.
Initial Actuation Test¶
(The final videos are embedded in the “Final Vimeo Videos” section at the end of this page.)
Video Caption
A soft robotics design was initially planned.
The first mold-making results were not satisfactory, and this design was abandoned.
After reviewing previous Fabricademy works shared by Fabricademy 2024 alumna Aslı Aydı Aksan,
a mold model originally created by Samson, a Fab Academy 2023 student, was selected.
The model was imported into Blender.
Without changing the main structure, a closure system and air inlet were designed.
The model was exported as an STL file and prepared for 3D printing on an Ultimaker printer.
Standard PLA filament was used with a nozzle temperature of 200 °C and a bed temperature of 60 °C.
The prepared silicone mixture was poured into the molds, cured, and removed.
Two silicone parts were bonded together.
An additional small mold was used to reinforce the air inlet connection.
Final Testing & Failure Analysis¶
11-second observation — The soft robotic actuator started inflating but did not continue.
As pressure increased, it became clear that there was air leakage in the system.
8-second observation — Leakage increased and it was understood that the plastic tube connector used for the air inlet did not adhere well to the silicone.
15-second test — Compressed air was supplied using a compressor.
The actuator inflated as intended, but because the air pressure was too strong, the silicone ruptured at its weakest point.
Structural Behavior Explanation¶
This actuator was designed with asymmetric wall thickness:
- Bottom layer: thick (structural support)
- Top layer: thin (designed to expand)
When air pressure enters the chamber, the thin side expands first.
This expansion bends the actuator toward the thicker side, creating a gripping / curling motion.
If both sides had equal thickness, this controlled bending behavior would not occur.
When air inlet pressure and air release are properly regulated, the actuator’s gripping, opening, and releasing motion can be controlled more reliably.
Reflections & Learnings¶
- Silicone work requires patience, precision, and time
- Accurate ratio measurement is essential
- Mold surface quality directly affects silicone performance
- Boolean simulations in Blender are highly effective
- Air inlet design is a critical structural element
- Pressure control is as important as material choice
- Failure points provide valuable design feedback