A robot end effector for dispensing an extrudable substance comprises a chassis and cartridge bays, attached to the chassis and each shaped to receive a corresponding one of two-part cartridges. Robot end effector also comprises a dispensing valve, attached to the chassis and comprising a valve inlet and a valve outlet. The valve outlet is in selective fluidic communication with the valve inlet. Robot end effector further comprises a manifold, comprising a manifold outlet and manifold inlets, which are in fluidic communication with the manifold outlet. Robot end effector additionally comprises a plunger assembly, comprising pairs of plungers and arranged to concurrently extrude contents of the two-part cartridges through the cartridge outlets. Robot end effector also comprises an electric motor, attached to the chassis and configured to selectively move the plunger assembly relative to the chassis.