LAYER-BASED DEFECT DETECTION USING NORMALIZED SENSOR DATA

• US 20170266762A1
• Filed: 03/21/2017
• Published: 09/21/2017
• Est. Priority Date: 03/21/2016
• Status: Active Grant

• Current Assignee: Divergent Technologies, Inc.
• Original Assignee: Sigma Labs, Inc.
• Inventors: Dave, Vivek R., Cola, Mark J.
• Granted Patent: US 11,072,043 B2
• Time in Patent Office: Days
• CPC Class Codes: B22F 10/28 Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• CPC Class Codes: B22F 10/31 Calibration of process steps or apparatus settings, e.g. before or during manufacturing
• CPC Class Codes: B22F 10/366 Scanning parameters, e.g. hatch distance or scanning strategy
• CPC Class Codes: B22F 10/38 to achieve specific product aspects, e.g. surface smoothness, density, porosity or hollow structures
• CPC Class Codes: B22F 12/41 characterised by the type, e.g. laser or electron beam
• CPC Class Codes: B22F 12/49 Scanners
• CPC Class Codes: B22F 12/90 Means for process control, e.g. cameras or sensors
• CPC Class Codes: B23K 26/034 Observing the temperature of the workpiece
• CPC Class Codes: B23K 26/342 Build-up welding
• CPC Class Codes: B23K 31/125 Weld quality monitoring
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B41M 5/262 recording or marking of inorganic surfaces or materials, e.g. glass, metal, or ceramics marking of plastic artifacts with inorganic additives B41M5/267
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/07 Arrangements for adjusting the solid angle of collected radiation, e.g. adjusting or orienting field of view, tracking position or encoding angular position optical collimating elements G01J5/0806
• CPC Class Codes: G01J 5/48 Thermography; Techniques using wholly visual means
• CPC Class Codes: G01J 5/80 Calibration using comparison with reference sources G01J5/52
• CPC Class Codes: G01K 11/00 Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
• CPC Class Codes: G01N 25/72 Investigating presence of flaws
• CPC Class Codes: Y02P 10/25 : Process efficiency

Abstract

The disclosed embodiments relate to the monitoring and control of additive manufacturing. In particular, a method is shown for removing errors inherent in thermal measurement equipment so that the presence of errors in a product build operation can be identified and acted upon with greater precision. Instead of monitoring a grid of discrete locations on the build plane with a temperature sensor, the intensity, duration and in some cases position of each scan is recorded in order to characterize one or more build operations.

Claims

1. An additive manufacturing method, comprising:

monitoring a heat source scanning across a powder bed using an optical temperature sensor;

scanning across different portions of the powder bed with the heat source to produce a metal part;

recording the intensity and duration of scans made by the heat source;

generating a characteristic curve from the optical temperature sensor for one or more regions of the metal part using the recorded scan duration and intensity data;

comparing the characteristic curve of each region with a baseline characteristic curve associated with the respective region; and

determining one of the regions is defective when the comparing shows a difference between the characteristic curve of the region and the baseline characteristic curve that exceeds a predetermined threshold.

2. The additive manufacturing method of claim 1, further comprising adjusting one or more characteristics of the heat source in accordance with the difference between the characteristic curve of the region and the baseline characteristic curve for the region when the layer is determined to be defective.

3. The additive manufacturing method of claim 1, wherein generating the characteristic curve comprises approximating the distance of each scan from the optical temperature sensor by ranking a set of similar duration scans by intensity.

4. The additive manufacturing method of claim 3, wherein the temperature sensor is an off-axis temperature sensor configured to gather Eulerian data from the powder bed.

5. The additive manufacturing method of claim 1, wherein recording the intensity duration of scans further comprises recording the position of each of the recorded scans.

6. The additive manufacturing method of claim 1, wherein a substantial portion of the field of view of the optical temperature sensor is filled by the melt pool.

7. The additive manufacturing method of claim 1, wherein the heat source is a laser.

8. The additive manufacturing method of claim 7, wherein the optical temperature sensor shares optics with the laser.

9. The additive manufacturing method of claim 1, wherein the baseline characteristic curve is determined at least in part by empirical data.

10. The additive manufacturing method of claim 1, further comprising:

identifying one or more regions of the part more likely to be susceptible to defects; and

recording only those scans of the laser occurring within the identified regions of the part.

11. A manufacturing method, comprising:

identifying one or more regions within a part where defects are more likely to occur during the manufacturing method;

recording sensor data from laser scans made within the identified one or more regions using an optical temperature sensor;

generating a characteristic curve for each of the one or more regions using the sensor data collected for each of the recorded laser scans;

comparing the characteristic curves to corresponding a baseline characteristic curves; and

determining one or more of the regions is defective when the comparing shows a difference between the characteristic curve of the region and the baseline characteristic curve that exceeds a predetermined threshold.

12. The manufacturing method of claim 11, further comprising identifying areas within the part where defects are less likely to occur.

13. The manufacturing method of claim 12, wherein recording laser scans made within the identified one or more regions comprises recording laser scans only within the one or more regions using the temperature sensor.

14. The manufacturing method of claim 11, wherein the manufacturing method is an additive manufacturing method.

15. The manufacturing method of claim 11, wherein the manufacturing method is a laser-based marking operation.

16. An additive manufacturing method, comprising:

creating a metal part on a powder bed using a scanning laser;

recording sensor data for scans made by the laser in select regions of the metal part using an optical temperature sensor;

determining intensity and duration of each of the recorded scans;

creating a characteristic curve for each of the regions of the metal part based on the intensity and duration of each scan associated with the region;

comparing each of the characteristic curves to a baseline characteristic curve associated with each of the regions; and

determining based on the comparing whether any of the regions are likely to have manufacturing defects.

17. The additive manufacturing method of claim 16, wherein the select regions correspond to one or more geometric features of the metal part.

18. The additive manufacturing method of claim 17, wherein the geometric features are selected from the group consisting of a sharp corner, a protrusion and an overhang.

19. The additive manufacturing method of claim 16, further comprising associating position information with the intensity and duration data of each scan.

20. The additive manufacturing method of claim 19, wherein the position information is received from a controller associated with the scanning laser.