A bone cement mixing and delivery system is provided in which separate components of bone cement are mixed together in a mixer to form a bone cement mixture. The mixer includes a paddle for mixing the components in a mixing chamber and a piston that pushes the mixing cement into an attached delivery device. The system further includes a switch that disconnects the drive assembly that actuates the paddle and piston from its power source. The switch is automatically tripped by a follower that moves upon actuation of the drive assembly. Once the cement is mixed and transferred to the delivery device, the follower trips the switch to automatically deactivate the drive assembly.