Ulticasting: A New Method for Soft Robot Fabrication
In the world of soft robotics, advanced manufacturing often plays an integral role in the fabrication of complex and intricate structures. In many cases, 3D printers, CNC machines, laser cutters, and more are irreplaceable. Here at Super-Releaser, 3D printers are key to our prototyping workflow, and as a result of this relationship, enhancement in advanced manufacturing often results in innovation in the field. A great example is how multi-material jetting printers allowed researchers at the Harvard Wyss Institute in 2015 to create a jumping robot that smoothly integrates both hard and soft components.
Recently, students at Delft University of Technology also developed such an innovation: a 3D printing system that allows for easier fabrication of silicone structures while being very inexpensive. The team, consisting of design and engineering undergraduates Christoffer Bendtsen, Oliver Groot, Max Nobel, and Luc van den Boogart set out to investigate new methods of fabricating soft robots, specifically by investigating a concept originally explored by Lars Rossing called UltiCasting. The UltiCast system consists of a modified Ultimaker 2+ 3D printer that has a paste extruder system with motorized syringes (similar to the likes of the MakerBot Frostruder) alongside the normal nozzle. The main nozzle prints out a thin-walled mold made from PVA, a water-soluble plastic, and then uses the secondary extruder to passively mix a 1:1 silicone resin and dispense it into the shell mold.
After the silicone has cured, it can be taken off the printer and the plastic mold can be dissolved away, leaving just the silicone behind. By having the casting process automated like this and pouring the mold as it is printed, the UltiCast system speeds up the fabrication of a silicone structure tremendously. It also reduces the room for human error, as having the mold printed and casted as one operation eliminates the need for complex mold assemblies.
The team started their work by hacking the firmware of their Ultimaker 2+ 3D printer to accommodate the new hardware and the Python tool that they developed to perform slicing, calculate the volume of the mold, and coordinate the movement for the printhead. After much experimentation and problem-solving, it was discovered that the system used to pump the uncured silicone would build up too much pressure, and could even burst. As a result, the team needed to redesign all the parts that came into contact with the silicone. After more hard work, they managed to achieve a fully-functional UltiCast system, creating a large silicone finger as the first print.
After publishing their results online, their work was presented at the TU Delft Industrial Design Engineering Faculty Science Fair, an event hosted by the school to encourage students to pursue interesting fields of research. They showed off the process, the UltiCast system itself, some sample prints, and some additional research the team had done into directly 3D printing soft robotic components out of thermoplastic elastomer materials such as NinjaFlex. This other research project produced a soft robotic exoskeleton glove that allows the wearer to grip objects with greater strength.
On the whole, research and developments such as this are incredibly vital to the growth and maturing of the emergent field of soft robotics. Here at Super-Releaser, we are investigating soft dynamic structures on a daily basis, and know the value that advanced fabrication has. We think the students’ research presents a strong case for the benefits of iterating and improving from the ground up, starting with the manufacturing itself. Taking novel approaches to “old” ideas allows for rapid innovation, and contributes tremendously to new fields, whether it be additive manufacturing, compliant robotics, or beyond.
For more information on the project and research, check out the team’s website.