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, in selective fluidic communication with the valve inlet. Robot end effector further comprises a manifold, comprising a manifold outlet and manifold inlets. The manifold outlet is in fluidic communication with the valve inlet. Robot end effector additionally comprises a plunger assembly, comprising pairs of plungers. Plunger assembly is arranged to concurrently extrude contents of the two-part cartridges through the cartridge outlets when the two-part cartridges are received by the cartridge bays. Robot end effector also comprises a non-rotating linear pneumatic actuator, configured to selectively move the plunger assembly relative to the chassis.