System and method for generation of test patterns for measurement of printhead to substrate separation in a printer
View Patent ↗A method of generating a test pattern for use in identification of a z-axis distance between a printhead and a substrate in a three-dimensional object printer includes forming a first predetermined test pattern on a substrate with the printhead and generating image data of the first test pattern. The method further includes identifying cross-process direction offsets of marks in the image data of the first test pattern and generating second test pattern data for the printhead using only a portion of the ejectors in the printhead and not including a mark from at least one ejector in the printhead with a cross-process direction offset that is less than another cross-process direction offset of at least one ejector in the portion of the ejectors.
1. A method of operating a three-dimensional object printer comprising:
operating with a controller a plurality of ejectors in a printhead with reference to stored image data to form a first predetermined test pattern including a first plurality of marks arranged in a cross-process direction on a surface of a substrate;
generating with an image sensor first generated image data of the first plurality of marks on the substrate;
identifying with the controller a plurality of cross-process direction offsets for the first plurality of marks in the first generated image data of the first predetermined test pattern, each cross-process direction offset being identified with reference to a difference between a location of a mark in the first generated image data and a predetermined location of the mark in the stored image data referenced to form the first predetermined test pattern;
generating with the controller second test pattern data that correspond to a second plurality of marks arranged in the cross-process direction to be formed by only a portion of the plurality of ejectors in the printhead and without a mark formed by at least one other ejector in the plurality of ejectors, the mark corresponding to the at least one other ejector having an identified cross-process direction offset that is less than another identified cross-process direction offset of at least one ejector in the portion of the plurality of ejectors in the printhead; and
storing with the controller the second test pattern data in a memory for operation of the portion of the plurality of the ejectors to enable identification of a z-axis distance between the printhead and the substrate, the z-axis being perpendicular to the surface of the substrate.
2. The method of claim 1 , the generation of the second test pattern data further comprising:
identifying with the controller the portion of the plurality of ejectors with reference to a max sum min gap process applied to the plurality of cross-process direction offsets to identify the portion of the plurality of ejectors that form marks in the first plurality of marks with a maximized sum of cross-process direction offsets.
3. The method of claim 2 , the max sum min gap process further comprising:
identifying with the controller the portion of the plurality of ejectors during the max sum min gap process with a predetermined minimum number of ejectors in the plurality of ejectors that are not in the portion of the plurality of ejectors separating ejectors in the portion of the plurality of ejectors that form adjacent marks in the cross-process direction in the second test pattern data.
4. The method of claim 1 , the generation of the second test pattern data further comprising:
generating with the controller the second test pattern data including a plurality of rows of marks formed by the portion of the plurality of ejectors in the printhead.
5. The method of claim 1 further comprising:
operating with the controller the plurality of ejectors in the printhead with reference to the second test pattern data to form a second test pattern having the second plurality of marks on the surface of the substrate at a first z-axis distance between the printhead and the substrate with reference to the second test pattern data;
generating with the image sensor second generated image data of the second plurality of marks in the second test pattern on the substrate at the first z-axis distance;
identifying with the controller a first variation of cross-process direction distances between marks in the second plurality of marks of the second test pattern with reference to the second generated image data;
operating an actuator to move at least one of the printhead and the substrate along the z-axis by a predetermined offset distance to separate the printhead and the substrate by a second z-axis distance;
operating with the controller the plurality of ejectors in the printhead with reference to the second test pattern data to form the second test pattern on the surface of the substrate at the second z-axis distance between the printhead and the substrate;
generating with the image sensor third generated image data of the second test pattern on the substrate at the second z-axis distance;
identifying with the controller a second variation of cross-process direction distances between marks in the second plurality of marks of the second test pattern with reference to the third generated image data;
generating with the controller a profile for the printhead with reference to the first variation, the second variation, and the predetermined offset distance, the profile including a relationship between a plurality of variations of cross-process direction distances between marks in test patterns and corresponding z-axis distances between the printhead and the substrate; and
storing the profile in a memory for use in identification of the z-axis distance between the printhead and the substrate during a printing operation.
6. The method of claim 5 , the generation of the profile further comprising:
generating with the controller a linear relationship between the plurality of variations of cross-process direction distances between marks in printed test patterns and corresponding z-axis distances between the first printhead and the substrate with reference to the first variation, the second variation, and the predetermined z-axis offset distance.
7. The method of claim 1 further comprising:
operating with the controller the plurality of ejectors in the printhead with reference to the second test pattern data to form a second test pattern having the second plurality of marks on the surface of the substrate;
generating with the image sensor second generated image data of the second test pattern on the substrate;
identifying with the controller a variation of cross-process direction distances between marks in the second plurality of marks of the second test pattern with reference to the second generated image data;
identifying with the controller a z-axis distance between the printhead and the substrate, with reference to the identified variation, the z-axis being perpendicular to the surface of the substrate; and
operating with the controller at least one actuator to move at least one of the printhead and the substrate along the z-axis in response to the identified z-axis distance being outside of a predetermined z-axis distance range.
8. The method of claim 7 further comprising:
identifying with the controller the z-axis distance between the printhead and the substrate with reference to a profile stored in the memory, the profile including a relationship between a range of z-axis distances between the first printhead and the substrate and corresponding variations between marks in printed test patterns formed over the range of z-axis distances.
9. A three-dimensional object printer comprising:
a printhead having a plurality of ejectors configured to eject drops of a material onto a surface of a substrate;
an actuator configured to move at least one of the substrate and the printhead along a z-axis;
an image sensor configured to generate image data of the surface of the substrate and test patterns formed on the substrate;
a memory; and
a controller operatively connected to the printhead, the actuator, the image sensor, and the memory, the controller being configured to:
operate the plurality of ejectors in the printhead with reference to image data stored in the memory to form a first predetermined test pattern including a first plurality of marks arranged in a cross-process direction on the surface of the substrate;
generate with the image sensor first generated image data of the first plurality of marks on the substrate;
identify a plurality of cross-process direction offsets for the first plurality of marks in the first generated image data of the first predetermined test pattern, each cross-process direction offset being identified with reference to a difference between a location of a mark in the first generated image data and a predetermined location of the mark in the stored image data referenced to form the first predetermined test pattern;
generate second test pattern data that correspond to a second plurality of marks arranged in the cross-process direction to be formed by only a portion of the plurality of ejectors in the printhead and without a mark formed by at least one other ejector in the plurality of ejectors, the mark corresponding to the at least one other ejector having an identified cross-process direction offset that is less than another identified cross-process direction offset of at least one ejector in the portion of the plurality of ejectors in the printhead; and
store the second test pattern data in the memory for operation of the portion of the plurality of the ejectors to enable identification of a z-axis distance between the printhead and the substrate, the z-axis being perpendicular to the surface of the substrate.
10. The three-dimensional object printer of claim 9 , the controller being further configured to:
identify the portion of the plurality of ejectors with reference to a max sum min gap process applied to the plurality of cross-process direction offsets to identify the portion of the plurality of ejectors that form marks in the first plurality of marks with a maximized sum of cross-process direction offsets.
11. The three-dimensional object printer of claim 10 , the controller being further configured to:
identify the portion of the plurality of ejectors during the max sum min gap process with a predetermined minimum number of ejectors in the plurality of ejectors that are not in the portion of the plurality of ejectors separating ejectors in the portion of the plurality of ejectors that form adjacent marks in the cross-process direction in the second test pattern data.
12. The three-dimensional object printer of claim 9 , the controller being further configured to:
generate the second test pattern data including a plurality of rows of marks formed by the portion of the plurality of ejectors in the printhead.
13. The three-dimensional object printer of claim 9 , the controller being further configured to:
operate the plurality of ejectors in the printhead with reference to the second test pattern data to form a second test pattern having the second plurality of marks on the surface of the substrate at a first z-axis distance between the printhead and the substrate with reference to the second test pattern data;
generate with the image sensor second generated image data of the second plurality of marks in the second test pattern on the substrate at the first z-axis distance;
identify a first variation of cross-process direction distances between marks in the second plurality of marks of the second test pattern with reference to the second generated image data;
operate the actuator to move at least one of the printhead and the substrate along the z-axis by a predetermined offset distance to separate the printhead and the substrate by a second z-axis distance;
operate the plurality of ejectors in the printhead with reference to the second test pattern data to form the second test pattern on the surface of the substrate at the second z-axis distance between the printhead and the substrate;
generate with the image sensor third generated image data of the second test pattern on the substrate;
identify a second variation of cross-process direction distances between marks in the second plurality of marks of the second test pattern with reference to the third generated image data;
generate a profile for the printhead with reference to the first variation, the second variation, and the predetermined offset distance, the profile including a relationship between a plurality of variations of cross-process direction distances between marks in test patterns and corresponding z-axis distances between the printhead and the substrate; and
store the profile in the memory for use in identification of the z-axis distance between the printhead and the substrate during a printing operation.
14. The three-dimensional object printer of claim 13 , the controller being further configured to:
generate a linear relationship between the plurality of variations of cross-process direction distances between marks in printed test patterns and corresponding z-axis distances between the first printhead and the substrate with reference to the first variation, the second variation, and the predetermined offset distance.
15. The three-dimensional object printer of claim 9 , the controller being further configured to:
operate the plurality of ejectors in the printhead with reference to the second test pattern data to form a second test pattern having the second plurality of marks on the surface of the substrate;
generate with the image sensor second generated image data of the second test pattern on the substrate;
identify with the controller a variation of cross-process direction distances between marks in the second plurality of marks of the second test pattern with reference to the second generated image data;
identify with the controller a z-axis distance between the printhead and the substrate, with reference to the identified variation, the z-axis being perpendicular to the surface of the substrate; and
operate the actuator to move at least one of the printhead and the substrate along the z-axis in response to the identified z-axis distance being outside of a predetermined z-axis distance range.
16. The three-dimensional object printer of claim 15 , the controller being further configured to:
identify the z-axis distance between the printhead and the substrate with reference to a profile stored in the memory, the profile including a relationship between a range of z-axis distances between the first printhead and the substrate and corresponding variations between marks in printed test patterns formed over the range of z-axis distances.