The biggest problem in 3D printing is mass production. While prototyping one or two items per day is fine for small manufacturers, what if you want to customize hundreds or thousands phone cases for Google’s Project Ara phone?

3D Systems is solving this problem by creating a sort of 3D printing assembly line. The line runs in a circle with printing nozzles squirting out different colors at each pass. For example, you could print half of one layer in blue, another in red, and another one using conductive material. As the items spin under the nozzles they gain height and are then moved out of the system into a collection bin. Think of it as a merry-go-round for manufacturing.

The goal is to offer cases for Project Ara phones that are designed entirely by customers. It looks like things are going to be fairly simple – just colored squares on a background – but the concept is compelling.

Quoth 3DSystems:

Whereas 3D printers typically utilize a moving printhead on a stationary bed, the high-speed, continuous fab-grade printer puts the print bed in motion on speedy track system under a set of stationary printheads. The result is a 3D printing assembly line: many products printing at once, all unique, all in full color and multi materials.

The new system prints 50 times faster than standard FDM printing, which is pretty impressive. You probably won’t get this technology in your home workshop anytime soon, however, because you’re basically looking at seven 3D printers all working at once in an industrial environment. The company will be showing off more Ara tech over the next few weeks.