Some of the feedback we’ve received from our recent crowdfunding plea has suggested we try to find a cheaper way to produce our discs, ie ink printing. Robert has written up this explanation, for those interested in a breakdown of the technical details and costs:

The optical disc technology used by Mattel/Opsonar (et al) was based on high resolution film. Only film has the resolution to meet our audio quality targets. With film, you can digitally plot an image up to 16,000 DPI (and even better), and it’s straightforward to make copies (a mechanical/optical process). This is why film is still used for circuit board and chip fabrication as well as archival microfilm. Since the tracks on the discs are so narrow, the equivalent bit resolution computes to slightly less than 8 bits when plotted at 8000 DPI.

Ink systems are problematic. First, I know of no ink printers that can print at such high resolution. Second, the ink would have to be very thin and have zero surface tension to capture fine details. The side effect of this would be that the ink would be less opaque. It would also have to have a really good binder to stick to the plastic (Mylar) substrate, which would affect its ability to flow into the details. This ink would also be easy to damage by merely touching the disc or removing it from a disc sleeve.

Photo plotting will generate a master negative, but to make copies requires making contact prints (a manual process). You also need a film processor to develop the film in a controlled, dust-free manner. A fixture is required to cut the large sheets of film down to smaller rectangles that can be processed. There are punch fixtures for precisely aligning the center hole with the disc image. Most of these manual steps are not needed to produce film for PCBs, so the businesses that plot film aren’t fully equipped to do this or are willing to take this on.

The primary costs are due to the expense of the equipment (plotter and film processor), building the darkroom (walls, ceiling, door) power connections for plotter and processor (220V 13A to 16A with disconnect box), water connections, water filtering, utility sink, chemical waste collection and disposal, special drainage, venting for the processor, air filtering, fixtures, lighting (exposure and safety), contact frame, vacuum pump for contact frame, furniture (tables and shelves). All told, this will cost around $50k.

There is some good news: I was able to retrieve the punch fixture, contact frame, exposure light, and vacuum pump that were used to make the discs (total cost $1300). A film processor company is working with me on spec’ing a new machine to develop discs at a substantial cost savings compared to standard PCB film processors.

Acquiring the means to make discs in-house allows for more creativity. It will be much easier to make discs with custom sounds for individuals, and will allow for more experimentation.