Apparatus and method for printing three dimensional articles

Abstract

An apparatus for printing an image onto a curved surface of a three dimensional article. The apparatus principally includes a support fixture adapted to support the article, an ink jet print head having a plurality of nozzles, and an articulatable robotic arm. One of the support fixture supporting the article and the print head is mounted to and carried by the robotic arm. The robotic arm has more than three degrees of freedom of movement and is moveable so as to cause relative movement of the print head along a series of scanning paths that follow the surface contour of the curved surface of the article. A controller is coupled to the robotic arm and is configured to cause articulation of the robotic arm so as to move the print head along the series of scanning paths. The controller causes the robotic arm to continuously locate the print head relative to the curved surface of the article in a position suitable for printing as the print head is moved along the series of scanning paths. The controller is further configured to cause the plurality of nozzles to eject printing medium at predetermined locations along the scanning paths so as to form the image on the curved surface of the substrate.

1 . An apparatus for printing an image onto a curved surface of a three dimensional article, the apparatus comprising:
 a support fixture adapted to support the article;   an ink jet print head having a plurality of nozzles coupled to a source of printing medium;   an articulatable robotic arm, one of the print head and the support fixture being mounted to and carried by the robotic arm, the robotic arm having more than three degrees of freedom of movement and being moveable so as to cause relative movement of the print head along a series of scanning paths following surface contour of the curved surface of the article; and   a controller coupled to the robotic arm and being configured to cause articulation of the robotic arm so as to cause relative movement of the print head along the series of scanning paths, the controller causing the robotic arm to continuously locate the print head relative to the curved surface of the article in a position suitable for printing as the print head is moved along the series of scanning paths, the controller coupled to the print head and further configured to cause the plurality of nozzles to eject printing medium at predetermined locations along the scanning paths so as to form the image on the curved surface of the substrate.   
   
   
       2 . The apparatus of  claim 1  wherein the scanning paths are linear. 
   
   
       3 . The apparatus of  claim 1  wherein the plurality of nozzles are provided in one of a linear array and a two-dimensional array. 
   
   
       4 . The apparatus of  claim 1  wherein the controller is configured to cause the plurality of nozzles to eject printing medium based on a distance from a known point on the scanning paths correlated to image location data stored in memory of the controller. 
   
   
       5 . The apparatus of  claim 4  wherein the controller is configured to receive a start signal at a starting point of travel along the scanning paths and additional distance signals at additional distances along the scanning path and relative to the starting point. 
   
   
       6 . The apparatus of  claim 5  wherein the controller is configured to correct errors based on an actual scanning path relative to a desired scanning path, the controlling of the ejection of printing medium from the plurality of nozzles being corrected to correspond to the actual scanning path. 
   
   
       7 . The apparatus of  claim 1  further comprising a sensor configured to sense part features on the curved surface of the part, wherein the controller is configured to cause the plurality of nozzles to eject printing medium based on the sensing of part features by the sensor. 
   
   
       8 . The apparatus of  claim 7  where in the sensor is an optical sensor. 
   
   
       9 . The apparatus of  claim 7  wherein the sensor is a laser sensor. 
   
   
       10 . The apparatus of  claim 7  wherein the controller is configured to have stored in memory a set of values for the ejection of printing medium from each of the plurality of nozzles, the sets of values corresponding to each location of the part features. 
   
   
       11 . The apparatus of  claim 1  wherein the controller is configured to compare an actual position of the print head to stored image data corresponding to a three dimensional image on the surface of the article and control the ejection of printing medium from the plurality of nozzles based thereon. 
   
   
       12 . The apparatus of  claim 1  further comprising a print head height sensor configured to monitor the height of the print head relative to the curved surface of the article. 
   
   
       13 . The apparatus of  claim 12  further comprising an actuator configured to move one of the print head and surface of the article either toward or away from one another based on the monitored height of the print head. 
   
   
       14 . The apparatus of  claim 12  wherein the print head height sensor includes a laser. 
   
   
       15 . The apparatus of  claim 1  wherein the controller is configured to cause articulation of the robotic arm to position the print head at an orientation normal to the curved surface of the article. 
   
   
       16 . A method for printing an image onto a curved surface of a three dimensional article, the method comprising the steps of:
 providing a three dimensional article having a curved surface to be printed upon;   locating an ink jet print head having a plurality of nozzles proximate to the surface of the article;   causing relative movement of the ink jet print head along a scanning path across the surface of the article while positioning the ink jet print head relative to curvature exhibited by the surface of the article; and   ejecting ink from the plurality of nozzles according to the position of the print head relative to the article and image data stored in memory of a controller and correlated to the surface of the article.   
   
   
       17 . The method of  claim 16  wherein the step of ejecting ink further comprises the step of determining a starting location for relative movement of the ink jet print head and ejecting ink from the ink jet print head based on distance from the starting point that the print head has moved along the scanning path. 
   
   
       18 . The method of  claim 16  wherein the step of ejecting ink further comprises the step of determining a time of initial ejection of ink and ejecting ink from the ink jet print head based on elapsed time from the starting of ejecting of ink and the velocity of the print head moving along the scanning path. 
   
   
       19 . The method of  claim 16  wherein the step of ejecting ink further comprises the step of determining absolute coordinates of the print head relative to the surface of the article and correlating the coordinates with image data stored in memory of a controller. 
   
   
       20 . The method of  claim 16  wherein the step of ejecting ink further comprises the step of sensing a part feature with a sensor and ejecting ink from the ink jet print head based on location of the sensed part features correlated with image data stored in memory of a controller. 
   
   
       21 . The method of  claim 16  further comprising the step of sensing the height of the print head relative to the actual surface of the article and adjusting the height of the print head to an off-set height relative to the actual surface of the article.