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Pioneering Cable-Driven Robotics with 3D Printing

Creating devices that mirror the fluid movements of human limbs has long posed a challenge in robotics. However, advancements in “cable-driven” mechanisms are paving the way for innovative solutions. This technique involves threading strings through an object, facilitating coordinated movements across its sections. For instance, in a robotic finger, a cable could run from the palm to the fingertip, allowing the digit to curl and perform intricate motions.

Although these cable-driven systems can generate movement akin to bending, twisting, or folding, they often require extensive manual assembly, which can be both labor-intensive and time-consuming. To streamline this process, researchers at the Massachusetts Institute of Technology’s (MIT) Computer Science and Artificial Intelligence Laboratory (CSAIL) have introduced a novel 3D printing technology known as “Xstrings.” This comprehensive tool integrates part design and fabrication, significantly accelerating the assembly of bionic robots, artistic installations, and dynamic fashion pieces.

In a recent study slated for presentation at the 2025 Conference on Human Factors in Computing Systems (CHI2025), the team employed Xstrings to print a diverse array of vibrant objects. These included a robotic lizard that moves like a real creature, a peacock-inspired wall sculpture, a curling tentacle, and a claw capable of gripping items by forming a fist.

The Xstrings platform empowers users to create tailored designs using software, which can then be sent to a multi-material 3D printer for production. This process allows for the simultaneous printing of all components, including the necessary cables and joints, which are essential for the object’s movement capabilities.

Lead author Jiaji Li, a postdoctoral researcher at MIT CSAIL, noted that this method can reduce production time by up to 40% compared to traditional assembly methods. “Our innovative approach enables anyone to design and fabricate cable-driven devices using a desktop bi-material 3D printer,” Li stated.

Innovative Cable-Driven Fabrication

To utilize Xstrings, users start by entering design dimensions, such as a segmented rectangular cube featuring internal holes. They can then dictate the movement of these segments by selecting various “primitives” like bending, coiling, twisting, or compressing, and control the angles of these movements.

For more complex designs, multiple primitives can be combined, allowing for sophisticated motion sequences. For example, a toy snake could employ a series of twists, driving a coordinated movement through a single cord, while the robot claw may integrate several cables in a “parallel” configuration, enabling each digit to operate independently.

Moreover, Xstrings enhances the integration of cables within the design. Users can determine precise anchor points, threaded areas, and pull points, ensuring optimal functionality. For instance, a robotic finger can have its anchor at the fingertip while a cable traverses through the finger, with an easily accessible pull tag at the opposite end.

Applications in Art, Robotics, and Beyond

After simulating their designs digitally, users can fabricate their creations using a fused deposition modeling 3D printer, which constructs objects layer by layer from melted plastic. Xstrings meticulously places cables during printing to maintain functionality. Rigorous testing confirmed that their strings withstand immense stress, remaining intact after over 60,000 cycles of movement.

Li explained, “The software facilitates a multitude of creative possibilities, enabling engineers to produce robotic devices that replicate human hand movements while also allowing artists to create interactive sculptures and adjustable clothing designs. This technology may soon enable the rapid production of cable-driven robots in challenging environments like space stations or extraterrestrial habitats.”

The Xstrings approach not only enhances the speed of producing cable-driven designs but also ensures flexibility, allowing for hard exteriors and soft interiors or the potential for future developments that feature rigidity on the inside and flexibility on the outside, akin to human anatomy.

Collaborators on this research included students from Zhejiang University and Tsinghua University, alongside CSAIL members. Support for this research was partly provided by a postdoctoral fellowship from Zhejiang University and the MIT-GIST Program.

Source
news.mit.edu