LivePrinter is an open source system for live, intuitive, immediate drawing and fabrication with 3D printers. It allows people to directly draw shapes, lines, and complex objects using only code. The system serves as an introduction to the basics of 3D printing, as well as platform for experimenting with new techniques that are not allowed by current software. It also allows users to create physical forms using different functions that take into account physical properties like speed and temperature, instead of the usual visual modelling techniques. As a live performance system, LivePrinter blends mechanical music, sculpture and moving image together. It allows musical concepts and visual aesthetics to directly influence digital manufacturing toolpaths and vice versa. It demonstrates a possible future path where humans play a direct, creatively-rewarding part in a system of semi-automated, digital manufacturing.