Scanfield alignment of multiple optical systems
A method for calibrating beam scan fields for an additive manufacturing process in which two or more radiant energy beams are used to selectively melt material to form a workpiece. The method includes: directing the two or more radiant energy beams using individual beam steering mechanisms to create a calibration build pattern on a substrate, the calibration build pattern including at least one measurement artifact created by each of the two or more radiant energy beams; measuring the position of the measurement artifacts; comparing the position of the measurement artifacts to a standard to identify an alignment error; and adjusting at least one of the beam steering mechanisms to compensate for the alignment error.
1. A method of calibrating beam scan fields for an additive manufacturing process in which two or more radiant energy beams ( 54 , 56 ) are used to selectively fuse material to form a workpiece ( 25 ), the method comprising:
directing the two or more radiant energy beams ( 54 , 56 ) using individual beam steering mechanisms to create a calibration build pattern ( 66 ) on a substrate, the calibration build pattern ( 66 ) including at least one measurement artifact ( 70 , 72 ) created by each of the two or more radiant energy beams ( 54 , 56 );
measuring the position of the measurement artifacts ( 70 , 72 );
comparing the measured position of the measurement artifacts ( 70 , 72 ) to a standard to identify an alignment error; and
adjusting at least one of the beam steering mechanisms to compensate for the alignment error;
wherein the measurement artifacts ( 70 , 72 ) are arranged in a plurality of measurement artifact groups ( 68 ), and the measurement artifact groups ( 68 ) have a variable spacing distance within the calibration build pattern ( 66 ).
2. The method of claim 1 wherein each beam steering mechanism is associated with a scan field, and the beam steering mechanisms are positioned such that the scan fields partially overlap each other.
3. The method of claim 1 wherein the step of adjusting includes minimizing an average alignment error of each beam steering apparatus.
4. The method of claim 1 wherein the step of adjusting includes minimizing the alignment error in a predetermined location of the calibration build pattern ( 66 ).
5. The method of claim 1 wherein each beam steering mechanism includes at least one galvanometer operable to steer a radiant energy beam in response to an input signal.
6. The method of claim 1 wherein the step of adjusting includes changing at least one parameter of a software transfer function used to transmit drive signals to the beam steering mechanism.
7. The method of claim 1 wherein:
each beam steering mechanism is associated with a scan field, and
the step of adjusting includes providing different adjustment values at different portions of the scan field for each beam steering mechanisms.
8. The method of claim 1 wherein the measurement artifacts ( 70 , 72 ) are arranged in a plurality of measurement artifact groups ( 68 ), each measurement artifact group including a control point and including at least one measurement artifact formed by each of the radiant beams ( 54 , 56 ).
9. The method of claim 1 wherein the calibration build pattern ( 66 ) includes a central area ( 67 ) surrounded by a boundary ( 69 ), the measurement artifacts ( 70 , 72 ) are arranged in a plurality of measurement artifact groups ( 68 ), and the measurement artifact groups ( 68 ) have a relatively larger spacing within the central area ( 67 ) and a relatively smaller spacing near the boundary ( 69 ).
10. The method of claim 1 wherein the calibration build pattern ( 66 ) has a central area ( 67 ) surrounded by a boundary ( 69 ), the measurement artifacts ( 70 , 72 ) are arranged in a plurality of measurement artifact groups ( 68 ), and the measurement artifact groups ( 68 ) have a smaller spacing in a preselected region within the central area ( 67 ).
11. The method of claim 1 wherein the step of measuring includes determining a position of at least one point lying on each of the measurement artifacts ( 70 , 72 ).
12. The method of claim 1 wherein the material is a powder contained in a build chamber and the two or more energy beams are used to selectively fuse the powder in the build chamber in a layer-by-layer process to form the workpiece.
13. The method of claim 1 further comprising: using the calibrated additive manufacturing process to build one or more workpieces each including two or more layers.
14. The method of claim 13 further comprising: repeating the steps of creating a calibration build pattern, measuring the position of the measurement artifacts, comparing the measured position of the measurement artifacts to a standard, and adjusting at least one of the beam steering mechanisms, after a predetermined number of layers are built for one workpiece.
15. The method of claim 13 further comprising: repeating the steps of creating a calibration build pattern, measuring the position of the measurement artifacts, comparing the measured position of the measurement artifacts to a standard, and adjusting at least one of the beam steering mechanisms, after a predetermined number of workpieces are built.
16. The method of claim 1 further comprising: repeating the steps of creating a calibration build pattern, measuring the position of the measurement artifacts, and comparing the measured position of the measurement artifacts to a standard subsequent to adjusting at least one of the beam steering mechanisms, to confirm that a correction was sufficient.
17. The method of claim 1 wherein the standard includes at least one of a position or a rotation of a scan field relative to a center of a worksurface.
18. The method of claim 1 wherein the standard comprises an absolute position of a scan field.
19. The method of claim 1 wherein the standard comprises a relative position of two or more scan fields.