Closed-loop, rapid manufacturing of three-dimensional components using direct metal deposition

• US 6,925,346 B1
• Filed: 09/27/2000
• Issued: 08/02/2005
• Est. Priority Date: 06/30/1998
• Status: Expired due to Term

• Current Assignee: DM3D Technology, LLC
• Original Assignee: Joseph K. Kelly, Jyoti Mazumder
• Inventors: Kelly, Joseph K., Mazumder, Jyoti
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): Rapp, Chad
• Application Number:
  US09/671,538
• Time in Patent Office: 1,770 Days
• Field of Search: 700/119, 700/120, 700/160, 700/182, 700/258, 700/121, 419/7, 219/121.15, 219/121.16, 219/121.23, 219/121.22, 219/121.3, 219/121.309, 219/121.42, 219/121.5, 219/121.6, 219/121.61, 219/121.62, 219/121.63, 219/121.79, 219/121.81, 219/121.83
• US Class Current: 700/119
• CPC Class Codes: B22F 10/25 Direct deposition of metal particles, e.g. direct metal deposition [DMD] or laser engineered net shaping [LENS]
• CPC Class Codes: B22F 10/368 Temperature or temperature gradient, e.g. temperature of the melt pool
• CPC Class Codes: B22F 10/64 by thermal means control of energy beam parameters for post heating B22F10/364
• CPC Class Codes: B22F 10/85 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B22F 12/90 Means for process control, e.g. cameras or sensors
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/1017 Multiple heating or additional steps B22F3/101 takes precedence
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/034 Observing the temperature of the workpiece
• CPC Class Codes: B23K 26/32 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/34 Laser welding for purposes other than joining
• CPC Class Codes: B23K 35/0244 Powders, particles or spheres; Preforms made therefrom
• CPC Class Codes: B33Y 40/00 Auxiliary operations or equipment, e.g. for material handling
• CPC Class Codes: C23C 24/10 with intermediate formation of a liquid phase in the layer
• CPC Class Codes: C23C 4/12 characterised by the method of spraying
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

Multiple criteria are monitored and controlled to enhance the success of direct-metal deposition, including greater control over factors such as deposit layer height/thickness, sub-harmonic vibration, contour path shape, powder mass flow, and deposition speed, and stress accumulation. Sensors are used to monitor some or all of the following parameters during the deposition process: deposit height, width, temperature, and residual stress. A predetermined limit with respect to the yield strength of the material is preferably set. If the stress exceeds that limit sensors will automatically introduce one or more remedial measures, the priority of which is established using a look-up table generated in accordance with prior experimental knowledge. To control temperature induced distortion and stress, an infrared temperature detector may be used in conjunction with a controller to reduce temperature, increase speed and decreased power for purpose of stress management.

Claims

1. A method of optimizing a laser-assisted direct metal deposition process wherein material added to a melt pool is solidified fabricated an object according to a description thereof, the comprising the steps of:

creating a database including acceptable direct metal deposition process parameters based upon previously obtained empirical data;

measuring one or more dimensions of the melt pool;

monitoring the accumulation of residual stress of the object; and

referring to the description of the object to determine if the object is being fabricated in accordance with the description and, if so;

referring to the database to determine if the process parameters are within acceptable limits and if not;

implementing a corrective measure.

2. The method of claim 1, wherein the process parameter is the accumulation of stress within the object.

3. The method of claim 2, wherein the corrective measure is to modify the contour path of the laser.

4. The method of claim 2, wherein the corrective measure is to modify the mass flow of the powder.

5. The method of claim 2, wherein the corrective measure is to modify the speed of the deposition.

6. The method of claim 1, wherein the residual stress of the object is monitored through sub-harmonic vibration.

7. The method of claim 1, wherein the process parameter is the temperature of the melt pool.

8. The method of claim 7, wherein the corrective measure is to modify the power delivered to the laser.

9. The method of claim 1, wherein one or more dimensions of the melt pool are measured by monitoring the light received at the pixels of an optical detector.

10. The method of claim 1, wherein the database includes a look-up table.

11. A system for optimizing a laser-assisted direct metal deposition process wherein an object is fabricated in accordance with a description thereof, the system comprising:

a controllably moveable deposition head including a laser operative to form a melt pool on the surface of the object and a supply of powder feeding the melt pool to be solidified as the deposition head is traversed;

a database including acceptable direct metal deposition process parameters based upon previously obtained empirical data;

a first sensor for detecting one or more dimensions of the melt pool;

a second sensor the sensing the accumulation of residual stress of the object; and

a controller interfaced to the laser, deposition head movement control, database and first and second sensors, the controller being operative to perform the following functions;

refer to the description of the object to determine if the object is being fabricated in accordance with the description and, if so;

refer to the database to determine if the process parameters are within acceptable limits and if not;

implement a corrective measure.

12. The system of claim 11, wherein the process parameter is the accumulation of stress within the object.

13. The system of claim 12, wherein the corrective measure is to modify the contour path of the laser.

14. The system of claim 12, wherein the corrective measure is to modify the mass flow of the powder.

15. The system of claim 12, wherein the corrective measure is to modify the speed of the deposition.

16. The system of claim 12, wherein the first sensor is a sub-harmonic vibration sensor.

17. The system of claim 11, wherein temperature sensor.

18. The system of claim 17, wherein the corrective measure is to modify the power delivered to the laser.

19. The system of claim 11, wherein the second sensor is a one- or two-dimensional pixelized image sensor.

20. The system of claim 11, further including multiple deposition heads.