In a remarkable display of engineering and creativity, Paul MH has engineered a CNC machine dedicated to crafting intricate string art images. At a glance, string art may appear simple, involving only threads wound around posts, typically nails, to form patterns, text, shapes, or images. However, the underlying mathematics to achieve a precise image through string art is profoundly complex. The precision in the image is derived from the overlapping strings' density and angles. While skilled artists can manually create these pieces, designing a machine for this purpose poses a significant challenge, as showcased by Paul MH's endeavour.
In a detailed video, Paul shares his journey of developing this unique string art machine from the ground up, highlighting the numerous challenges encountered along the way. One notable challenge was devising a mechanism for inserting nails into the foam board base of the picture. The machine's design is Cartesian, featuring linear X and Y axes akin to a CNC router, and is controlled by a RAMPS 1.4 board, a common choice for such machines. However, the task of grabbing nails and inserting them into the foam board proved to be non-trivial.
Initially, Paul created a mechanism resembling a nail gun, with a hopper on the moving machine head to feed nails to an end effector. However, this design was found to be unreliable and necessitated the machine to bear the full weight of potentially hundreds of nails, consequently slowing down the machine. In response, Paul conceptualized a remote mechanism to feed nails for the end effector to pick up. Despite this innovation, reliability issues persisted, prompting the integration of a webcam coupled with a neural network to visually verify the presence of a nail. Feeding thread to the machine was a relatively simpler aspect of the project. The thread is dispensed from a spool through a PTFE tube and exits from a "nozzle" on the end effector. Once the thread is attached to the initial nail, the tension suffices to continue unspooling the thread as needed.
The software development is a major aspect of Paul's project. Employing advanced mathematical algorithms, the software processes a photo input to determine the thread paths that would yield the best visual representation. This process, akin to dithering a monochrome image, albeit more complex, then generates g-code for the machine. This code guides the machine to wrap the thread around the nails in a specific sequence while evading any collisions, thus bringing the envisioned string art image to life.