In order to explore the current limits of 3D printing technology, I've created a technique for converting digital audio files into 3D-printable, 33rpm records and printed a few functional prototypes that play on ordinary record players. Though the audio quality is low -the records have a sampling rate of 11kHz (a quarter of typical mp3 audio) and 5-6 bit resolution (less than one thousandth of typical 16 bit resolution)- the songs are still easily recognizable, watch the video above to see the process and hear what the records sound like.
This past year I've been posting a lot of audio projects, specifically, I've been experimenting with using relatively simple tools and techniques and very little memory to approximate and recreate digital audio signals. A great example is my Arduino Vocal Effects Box, where I used an Arduino to perform realtime pitch-bending on an incoming audio signal. Through these projects, I've learned that audio is a very resilient medium, it can take a fair amount of abuse (in the form of distortion and compression) while still maintaining most of the integrity of the original sound. The key is as long as you loosely approximate the overall shape of an audio signal, the output will sound reasonably recognizable. We have evolution 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 (sometimes these even include contextual or visual cues) to piece together mangled or noisy audio and make sense of it; this is how we are able to focus on one voice in crowded room or decipher a message sent over a cheap walkie talkie.
This project was my first experiment extending this idea beyond electronics. I printed these records on a UV-cured resin printer called the Objet Connex500. Like most 3D printers, the Objet creates an object by depositing material layer by layer until the final form is achieved. This printer has incredibly high resolution: 600dpi in the x and y axes and 16 microns in the z axis, some of the highest resolution possible with 3D printing at the moment. Despite all its precision, the Objet is still at least an order of magnitude or two away from the resolution of a real vinyl record. When I first started this project, I wasn't sure that the resolution of the Objet would be enough to reproduce audio, but I hoped that I might produce something recognizable by approximating the groove shape as accurately as possible with the tools I had.
In this Instructable, I'll demonstrate how I developed a workflow that can convert any audio file, of virtually any format, into a 3D model of a record, and how I optimized these records for playback on a real turntable. The 3D modeling in this project was far too complex for traditional drafting-style CAD techniques, so I wrote an program to do this conversion automatically. It works by importing raw audio data, performing some calculations to generate the geometry of a record, and eventually exporting this geometry straight to a 3D printable file format. Most of the heavy lifting is done by Processing, an open source programming environment that's often used for 2D and 3D graphics and modeling applications. Here's a basic overview of my Processing algorithm:
use raw audio data to set the groove depth- parse through the raw audio data, this is the set of numbers that defines the shape of the audio waveform, and use this information to set the height of the bottom of a spiral groove. This way, when a turntable stylus moves along the groove it will move vertically in the same path as the original waveform and recreate the original audio signal.
draw record and groove geometry- A 3D model is essentially a list of triangles arranged in 3D space to create a continuous mesh, use the data from the last step and some general record parameters (record diameter, thickness, groove width, etc) to generate the list of triangular faces that describes the record's shape and the detailed spiral groove inscribed on its surface.
export model in STL format- the STL file format is understood by all 3D printers, export the geometry calculated in the last step as an STL file. To get Processing to export straight to STL, I used the ModelBuilder Library written by Marius Watz (if you are into Arduino/Processing and 3D printing I highly recommend checking this out, it works great).
I've uploaded some of my complete record models to the 123D gallery as well as the Pirate Bay. Check Step 6 for a complete listing of what's there and what I plan on posting. Alternatively, you can go to Step 7 to download my code and learn how to make printable record models from your own audio.
Special thanks to Randy Sarafan, Steve Delaire, Arthur Harsuvanakit, Phil Seaton, and Audrey Love for their help with this project.
Here's another video that gives a great overview of the printing process and shows the printers at work:
Step 1: How Does a Record Work?
The record player and record cutter were invented by Edison in 1877. Due to a lack of precise machinery and technique at the time, the grooves on the first records were much larger than those on modern microgroove records and, subsequently, the audio signals were much noisier. This is a similar situation that I found myself in when starting this project: despite the high precision of the Objet machines, the resolution is nowhere near modern vinyl quality. Here and here are two examples of Edison's first phonograph tests. You can hear that the quality of recording of these tests is pretty close to what I've been able to 3d print; although I can't find the exact specs on these records, I'd imagine that the scale of the grooves was similar to what I was working with.
To give you an idea of the resolution of a modern record, check out the images above. Figs 1-3 are from Chris Supranowitz, a researcher at The Institute of Optics at the University of Rochester. These are close up images of a vinyl record, taken with an electron microscope. The dark objects in figs 1 and 2 are tiny particles of dust. Fig 3 is a bird's eye view of the record grooves, the darker regions are the top (uncut) surface of the record.
Fig 4 was made by branku62 at vinylengine.com, it shows the profile dimensions of a standard microgrove mono groove, this is what you would find on a modern mono 33 or 45 (stereo grooves are actually cut a bit smaller). In the diagram 1 mil = 1/1000", which is about 25um. Microgroove records require a stylus with a 0.7 to 1.0 mil radius tip, the tip makes contact with the groove at E in fig 1, a width of about 1.4 mil. The total depth of the groove is around 1.1 mil. These dimensions match up nicely with the dimensions of the electron microscope images.
Fig 5 is from Ron Geesin and Mark Berresford's website, it shows the groove depths of the older 78's. These records were much more coarse than microgroove records, both the needle and grooves were about 3x as large in every dimension. Fig 2 shows the groove depth for 78's was somewhere between 2.2 and 3.6 mil. The stylus radius was around 2.7 mil.