Difficulty: Elementary
Duration: Design - 30min, Fabrication - ca. 7-10h
Introduction
SoRoCAD is a tool for soft robotics design. It exposes the design parameters in its UI, and supports previewing the soft robot’s behavior by simulating the final actuation during the design phase. The following tutorial gives you an example of how to design and fabricate a silicon, pneumatic soft robot using SoRoCAD.
Prerequisite & Background topics
Designing Soft Robots that move the way you would like them to move is hard. Basic physical rules apply here: e.g. for pneumatic actuation - air always pushes in the way of least resistance, i.e. the thinner wall gets pushed out. The simulation in the tool is a key fact as it gives you a chance to see what movement you designed robot will do after fabricating it (not 100% accurate in terms of angle of the movement but direction of movement is correct).
Materials & Equipment
Software SoRoCAD (Runs on a MacBook)
Drying plate/area for silicone
Instructions
1. Before you start with designing the robot we would like to show you the interface of SoRoCAD with all its elements
Left: Interface of SoRoCAD during exterior geometry design: a) the viewport on the left showing the actuator (viewport control is possible); b) the three steps in the design pipeline (Air Channel, Exterior and Mold); c) sliders and text fields to control parameters that define the actuator; d) Run Simulation button; e) simulation preview (GIFs). / Right: Simulation window: f) viewport showing the simulation of the actuator; g) the user can step through the simulation using timesteps.
2. Designing a soft robot using SoRoCAD includes three basic steps in the tool before you can start fabricating the robot with real silicon materials. Those three basic steps are designing the Air channels, then the Silicone Exterior and then exporting the Mold file (the software has one tab for each step, which is visible in the top of the software window).
a.) Starting with building the pneumatic network in the Air Channel tab. The pneumatic network inside the soft robot takes care that the air pumbed inside gets distributed evenly. This is important to assure a smooth actuation of the soft robot. The tool gives the option for 6 different types of air channels that can be stacked next to each other as blocks. Each air channel block can be adapted regarding its dimension, its position in relation to the others (y-axis) and also rotated.
If you do not want to start from scratch you can also use templates for basic movement that the software provides.
b.) The you define the exterior geometry such as wall thicknesses
Every time the user adapts the outer wall thicknesses a little GIF is presented at the lower right in the software that previews what the movement will be like in the end. This preview does not take into account the shore value of the used silicone nor the amount of air pressure.
c.) You can always test in between what the movmenet of the design you have just created will be like when it is fabricated. For this you have to press the button 'Run a Simulation' (lower right in the interface in the Silicone Exterior tab). When the button was pressed this little window shows up in which you can define the shore value and air pressure for the simulation. The lower the shore value of the silicone is the softer and more flexible it is when it has dried.
When the Simulation has started, you can step through the movement and check whether the movement is fine with what he had in mind. But: the simulation is not 100% correct, but it gives the idea whether a robot might bend,or elongate etc.
d.) and finally exporting the automatic generated mold. The Mould consists of two files, each of them represents one half of the robot. I.e. you have to cast twice, once filling the molds with silicone and then gluing both together.
3. After the design phase you can start to fabricate the soft robot
3.1. 3D-Print your molds (b)
3.2. Cast the two halves of your robot using silicone (c)
3.3. Let the silicone cure (d)
3.4. Glue the two robots halves together (e)
3.5. Use a needle and a simple air pump to actuate your robot (f-h)
Link to the paper: https://dl.acm.org/doi/abs/10.1145/3491101.3519770