This protocol includes the designs and software necessary to upgrade an existing stereotaxic instrument to a robotic (computer numeric controlled; CNC) stereotaxic instrument for around $1,000 (excluding a drill).
Coffey, K. R., Barker, D. J., Ma, S., West, M. O. Building An Open-source Robotic Stereotaxic Instrument. J. Vis. Exp. (80), e51006, doi:10.3791/51006 (2013).