Viscous Material Noncontact Jetting System

Abstract

A viscous material noncontact jetting system has a jetting dispenser mounted for relative motion with respect to a surface. A control is operable to cause the jetting dispenser to jet a viscous material droplet that is applied to the surface as a viscous material dot. A device, such as a camera or weigh scale, is connected to the control and provides a feedback signal representing a size-related physical characteristic of the dot applied to the surface. The size-related physical characteristics of subsequently applied dots are controlled by heating and cooling, or adjusting a piston stroke in the jetting dispenser, in response to the size-related physical characteristic feedback. Dispensed material volume control and velocity offset compensation are also provided.

What is claimed is: 
     
         1 . A method of dispensing a viscous material onto a surface with a jetting dispenser having a nozzle, the method comprising:
 operating the jetting dispenser to apply dots of viscous material onto the surface;   determining a size-related physical characteristic of the dots applied to the surface; and   operating one of a first device that increases the temperature of the nozzle or a second device that decreases the temperature of the nozzle in response to the size-related physical characteristic of the dots applied to the surface deviating from a desired value.   
     
     
         2 . The method of  claim 1 , wherein the size-related physical characteristic is determinative of weights of the dots applied to the surface. 
     
     
         3 . The method of  claim 1 , wherein the size-related physical characteristic is determinative of volumes of the dots applied to the surface. 
     
     
         4 . The method of  claim 1 , wherein the size-related physical characteristic is determinative of diameters of the dots applied to the surface. 
     
     
         5 . The method of  claim 1 , further comprising:
 increasing the temperature of the nozzle of the jetting dispenser with a first device in response to the size-related physical characteristic of the dots applied to the surface being less than the desired value; and   decreasing the temperature the nozzle of the jetting dispenser with a second device in response to the size-related physical characteristic of the dots applied to the surface being greater than the desired value.   
     
     
         6 . The method of  claim 1 , further comprising:
 providing the desired size-related physical characteristic of the dots of viscous material to be applied to the surface; and   causing relative motion between the dispenser and the surface.   
     
     
         7 . A method of dispensing a viscous material onto a surface with a jetting dispenser having a piston reciprocable with respect to a seat, the method comprising:
 withdrawing the piston through a stroke away from the seat;   moving the piston through the stroke toward the seat to jet a droplet of viscous to the surface as a dot of viscous material;   determining a size-related physical characteristic of the dot applied to the surface;   sending a feedback signal to a controller, the feedback signal representing a size-related physical characteristic being respectively, less than, or greater than, a desired value; and   increasing or decreasing the stroke of the piston in response to the feedback signal.   
     
     
         8 . The method of  claim 7 , further comprising iterating the steps of withdrawing, moving, determining, sending and increasing or decreasing to apply a plurality of dots to the surface and to maintain the size-related physical characteristic of the plurality of dots close to the desired value. 
     
     
         9 . The method of  claim 7 , wherein increasing or decreasing the stroke of the piston further comprises:
 automatically increasing or decreasing the stroke using a motor mechanically coupled to the piston and electrically coupled to the controller.   
     
     
         10 . The method of  claim 7 , further comprising providing the desired size-related physical characteristic value representing a desired size-related physical characteristic of the dot of viscous material to be applied to the surface. 
     
     
         11 . The method of  claim 7 , wherein the size-related physical characteristic is a diameter of the dot applied to the surface. 
     
     
         12 . The method of  claim 7 , wherein the size-related physical characteristic is a weight of the dot applied to the surface. 
     
     
         13 . The method of  claim 7 , wherein the size-related physical characteristic is a volume of the dots applied to the surface. 
     
     
         14 . A method of dispensing a viscous material onto a surface with a jetting dispenser operatively connected to a controller, the method comprising:
 moving the jetting dispenser at a relative velocity with respect to the surface;   operating the jetting dispenser to dispense a viscous material dot onto the surface;   storing first coordinate values representing a position of the jetting dispenser upon operating the jetting dispenser;   storing second coordinate values representing a position of the viscous material dot on the surface; and   determining an offset value representing a difference between the first coordinate values and the second coordinate values, the offset value being used to modify the first coordinate values during a subsequent operation of the jetting dispenser.   
     
     
         15 . The method of  claim 14 , further comprising providing first coordinate values representing a position of the jetting dispenser at which the jetting dispenser is operable to apply a dot of viscous material onto the surface.