We present a printer that builds functional three-dimensional structures by reversible assembly of a discrete set of components, “digital materials”. This approach uses the components rather than a control system to impose the spatial and functional constraints. Printing can be performed as a parallel rather than a linear process. The printing process is reversible for re-use of the pieces or for error correction at any point in the object's life. Error detection, error-reduction and error-tolerance during assembly allows for reliable, high throughput printing. We are presenting development approaches to such a printing device.