Method and apparatus for dispensing a viscous material on a substrate

A dispenser for dispensing a volume of viscous material on a substrate includes a frame, a gantry system coupled to the frame, and a dispenser unit coupled to the gantry system. The dispenser unit includes a housing having a chamber and a piston disposed in the chamber. The piston is configured to move between a pre-dispense position and a dispense position within the chamber. The dispenser unit further includes a dispensing bore configured to receive the piston therein and a nozzle coupled to the housing. A controller is coupled to the piston to control the operation of the piston. The dispenser is constructed such that a volume of viscous material dispensed from the dispensing bore is substantially equal to the volume of the piston entering the dispensing bore when moving the piston to the dispense position. Other embodiments and methods of dispensing viscous material are further disclosed.