In order to test the current limits of 3D printing, I created a technique for converting digital audio recordings into 3D-printable, 33rpm records that play on ordinary turntables. Though the audio quality is low, the songs encoded on these records are still easily recognizable. The 3D modeling in this project was too complex to do by hand, so I wrote a Processing program to do this conversion automatically. It works by importing raw audio data, performing some calculations to generate the geometry of a 12" record, and eventually exporting this geometry straight to a 3D printable file format.

I initially came up with this idea after many experiments with very low resolution, real-time digital signal processing on an Arduino. Through these projects, I learned that audio is a very resilient medium; it can take a fair amount of distortion and compression while still maintaining most of the integrity of the original sound.  We have biology to thank for this: as we hear audio, some complicated processing goes on in our brains that makes us very good at ignoring noise and focusing on the important pieces of information coming through.  We can work off of relatively few cues to piece together mangled or noisy audio and make sense of it.

I printed these records on an Objet Connex 500, a high-end UV-cured resin printer.  Like most 3D printers, it creates an object by depositing material layer by layer until a final form is built.  The Objet prints with tiny resin droplets at a resolution of 600dpi in the x and y axes and 16 microns in the z axis. Even with this precision, the smallest features printed by an Objet are at least 1 or 2 orders of magnitude larger than those on a real vinyl record.  After a lot of experimentation and parameter tuning, I was able to produce records with a sampling rate of 11 kHz and 5-6 bits of resolution per sample. A detailed discussion of the development process, code, and downloadable 3D record files can be found on Instructables.

My code takes raw data from a digital recording and uses it to modulate the depth of the record groove to match the original waveform of the song. If you look carefully at the following closeup images, you can see the waveform traced out by the bottom of the groove. The waves are oriented vertically relative to surface of the record and cause the needle to vibrate up and down as it moves across the groove, recreating the original audio signal. The geometry of the record is calculated as a mesh of triangular faces and saved as an STL file using the ModelBuilder Library.

Stereo (2 channel) vinyl records are cut both vertically and laterally, this way it’s possible for two isolated channels of audio to fit into one groove. I chose to encode audio information vertically within the groove because the 3D printer I used was most precise along its vertical axis. With the exception of Edison cylinders, mono recordings are typically cut laterally for better quality and higher dynamic range.