MULTI-SENSOR QUALITY INFERENCE AND CONTROL FOR ADDITIVE MANUFACTURING PROCESSES

• US 20160185048A1
• Filed: 11/18/2015
• Published: 06/30/2016
• Est. Priority Date: 11/18/2014
• Status: Active Grant

• Current Assignee: Divergent Technologies, Inc.
• Original Assignee: Sigma Labs, Inc.
• Inventors: Roybal, Matias, Castro, Alberto, Dave, Vivek R., Clark, David D., Cola, Mark J., Piltch, Martin S., Madigan, R. Bruce
• Granted Patent: US 10,786,948 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B22F 10/00 Additive manufacturing of workpieces or articles from metallic powder apparatus or devices therefor B22F12/00
• CPC Class Codes: B22F 10/10 Formation of a green body
• CPC Class Codes: B22F 10/20 Direct sintering or melting
• CPC Class Codes: B22F 10/28 Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• CPC Class Codes: B22F 10/30 Process control
• CPC Class Codes: B22F 10/31 Calibration of process steps or apparatus settings, e.g. before or during manufacturing
• CPC Class Codes: B22F 10/36 of energy beam parameters
• CPC Class Codes: B22F 10/366 Scanning parameters, e.g. hatch distance or scanning strategy
• CPC Class Codes: B22F 10/368 Temperature or temperature gradient, e.g. temperature of the melt pool
• CPC Class Codes: B22F 10/38 to achieve specific product aspects, e.g. surface smoothness, density, porosity or hollow structures
• CPC Class Codes: B22F 10/85 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B22F 12/41 characterised by the type, e.g. laser or electron beam
• CPC Class Codes: B22F 12/44 characterised by the configuration of the radiation means
• 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: B22F 2203/03 for feed-back
• CPC Class Codes: B22F 2203/11 temperature, temperature profile
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B29C 64/153 using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• CPC Class Codes: B29C 64/386 Data acquisition or data processing for additive manufacturing
• CPC Class Codes: B29C 64/393 : for controlling or regulating additive manufacturing processes
• CPC Class Codes: B33Y 50/02 : for controlling or regulating additive manufacturing processes
• CPC Class Codes: G05B 19/41875 : characterised by quality surveillance of production
• CPC Class Codes: G05B 2219/32194 : Quality prediction
• CPC Class Codes: Y02P 10/25 : Process efficiency

Abstract

This invention teaches a multi-sensor quality inference system for additive manufacturing. This invention still further teaches a quality system that is capable of discerning and addressing three quality issues: i) process anomalies, or extreme unpredictable events uncorrelated to process inputs; ii) process variations, or difference between desired process parameters and actual operating conditions; and iii) material structure and properties, or the quality of the resultant material created by the Additive Manufacturing process. This invention further teaches experimental observations of the Additive Manufacturing process made only in a Lagrangian frame of reference. This invention even further teaches the use of the gathered sensor data to evaluate and control additive manufacturing operations in real time.

Claims

1. An additive manufacturing method, comprising:

monitoring the temperature of a first portion of a build plane during an additive manufacturing operation using a first optical temperature sensor;

monitoring the temperature of a second portion of the build plane that includes the first portion using a second optical temperature sensor;

detecting a change in state of material within the first portion as a heat source passes through the first portion of the build plane with the first sensor;

calibrating the second sensor by correlating the change in phase detected by the first sensor with information collected by the second sensor during the detected phase change; and

changing an amount of heat supplied by the heat source in accordance with the calibrated temperature information provided by the second sensor.

2. The additive manufacturing method of claim 1, wherein changing the amount of heat supplied by the heat source comprises shutting off the heat source.

3. The additive manufacturing method of claim 1, wherein changing the amount of heat supplied by the heat source comprises increasing the amount of heat supplied by the heat source in response to detecting solidification of the material within the first portion.

4. The additive manufacturing method of claim 1, wherein the first optical temperature sensor is a single color pyrometer.

5. The additive manufacturing method of claim 4, wherein the single color pyrometer detects both melting and solidification of the material within the first portion.

6. The additive manufacturing method of claim 4, wherein the on heating liquidus temperature is identified by taking the derivative of the temperature and correlating the on heating liquidus temperature with the greatest value from the temperature derivative.

7. The additive manufacturing method of claim 1, wherein calibrating the second sensor comprises correlating the detected melt temperature of the material with a known melting temperature of the material and scaling the temperature data recorded by the first optical temperature sensor using the correlation.

8. An additive manufacturing system, comprising:

a processor;

a heat source configured to direct energy towards a layer of powder arranged on a powder bed in a pattern defined by the processor that corresponds to a shape of a part;

a first optical sensor configured to determine a temperature associated with a fixed portion of the part; and

a second optical sensor configured to receive light emitted by a portion of the layer of powder being melted by the energy from the heat source,

wherein the processor is configured to receive sensor data from the first and second optical sensors during an additive manufacturing operation and to calibrate the sensor data by identifying phase changes during an additive manufacturing operation.

9. The additive manufacturing system of claim 8, wherein the processor is further configured to send a signal to the heat source to change the amount of heat applied to the layer of powder in response to the calibrated data indicating a rate at which one or more of the phase changes is occurring is off-nominal.

10. The additive manufacturing system of claim 9, wherein the processor is further configured to periodically calibrate the sensor data throughout the additive manufacturing operation so that any fluctuations in the application of the heat by the heat source is recorded for characterizing an overall quality of a part produced by the additive manufacturing operation.

11. The additive manufacturing system of claim 8, wherein the first optical sensor is a pyrometer and the second optical sensor is a photodiode.

12. The additive manufacturing system of claim 11, wherein the photodiode is configured as a Eulerian sensor and is able to detect heat emitted from the layer of powder in the powder bed.

13. The additive manufacturing system of claim 11, wherein the photodiode is configured as a Lagrangian sensor and shares optics with the heat source.

14. The additive manufacturing system of claim 13, wherein the calibrated temperature data from the pyrometer is correlated with raw data from the photodiode to characterize temperatures of the part outside of the fixed portion of the part.

15. The additive manufacturing system of claim 8, wherein the first optical sensor is configured to be focused on a portion of the powder bed that does not make up the part being produced by the additive manufacturing operation.

16. The additive manufacturing system of claim 15, wherein the portion of the build plane that the first optical sensor is focused on is a destructible portion that can be separated from the production part.

17. The additive manufacturing system of claim 8, wherein an area across which the first optical sensor measures temperature is substantially larger than an area that is heated by the heat source.

18. An additive manufacturing method, comprising:

applying heat to a powder distributed across a powder bed using a heat source;

measuring an amount of heat being emitted by a portion of the powder bed with an optical temperature sensor;

identifying when the portion of the part undergoes melting and solidifying phase changes;

calibrating the temperature data retrieved by the optical temperature sensor using the temperature at which the part undergoes the melting phase change and the temperature at which the material making up the metal part is known to melt; and

adjusting the amount of heat applied by the heat source in accordance with the calibrated temperature data.

19. The additive manufacturing method of claim 18, wherein the heat source is a laser.

20. The additive manufacturing method of claim 18, wherein the heat source is an electron beam.