Layer thickness control for stereolithography utilizing variable liquid elevation and laser focal length

• US 6,955,783 B2
• Filed: 06/06/2003
• Issued: 10/18/2005
• Est. Priority Date: 08/29/2000
• Status: Expired due to Fees

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Farnworth, Warren M.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US10/456,259
• Publication Number:
  US 20030205849A1
• Time in Patent Office: 865 Days
• Field of Search: 264/40.1, 264/401, 264/409, 425/135, 425/174.4, 425/375
• US Class Current: 264/401
• CPC Class Codes: B29C 2035/0838 using laser
• CPC Class Codes: B29C 2037/903 by means of a computer
• CPC Class Codes: B29C 64/135 the energy source being concentrated, e.g. scanning lasers or focused light sources
• CPC Class Codes: B29K 2995/0073 smooth
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 40/00 Auxiliary operations or equipment, e.g. for material handling
• CPC Class Codes: B33Y 40/20 Post-treatment, e.g. curing, coating or polishing

Abstract

An apparatus and method for controlling the surface level of a liquid residing within a relatively vertically stationary workpiece support platform disposed within a reservoir for use in stereolithographic processes wherein a layered object or structure is formed by selectively curing portions of the liquid to at least a semisolid state in multiple, at least partially superimposed layers. Providing precise control of liquid depth over the vertically stationary platform as well as focusing of a laser beam for curing the liquid at the varying surface levels thereof relative to the vertically stationary platform is effected using a laser range finder system controlled by a computer used to control the stereolithographic process in a closed loop fashion.

Claims

1. An apparatus for forming three-dimensional structures, comprising:

a platform disposed within a reservoir configured to hold a liquid curable to at least a semisolid state;

a source of electromagnetic radiation suitable for curing at least a portion of the liquid to the at least a semisolid state; and

a movable assembly configured to vary a surface level of the liquid relative to the platform, wherein the movable assembly comprises one of a displacement structure movable into and out of the liquid in the reservoir and at least a portion of the reservoir configured to be movable relative to the platform.

2. The apparatus of claim 1, wherein the movable assembly comprises a displacement structure having an average density greater than a density of the liquid in the reservoir.

3. The apparatus of claim 1, wherein the movable assembly comprises a displacement structure, and further comprising:

a drive assembly configured for moving the displacement structure into and out of the liquid in the reservoir, wherein the drive assembly comprises at least one of a cable, a stepper motor, and a screw drive.

4. The apparatus of claim 1, wherein the movable assembly comprises at least one of a bottom or side portion of the reservoir movable relative to another portion of the reservoir.

5. The apparatus of claim 1, wherein the movable assembly comprises a portion of the reservoir connected to a lift mechanism configured for raising and lowering the portion of the reservoir relative to the platform.

6. The apparatus of claim 1, further comprising at least one sensor configured to measure a distance from a reference point above the reservoir to a location on or above the platform.

7. The apparatus of claim 6, wherein the at least one sensor comprises at least one laser range finder.

8. The apparatus of claim 6, wherein the at least one sensor comprises a plurality of sensors configured to verify that the platform is level.

9. The apparatus of claim 8, further comprising a level adjustment system operably configured for reorienting the platform responsive to at least one distance measurement provided by the plurality of sensors.

10. The apparatus of claim 6, wherein the source of electromagnetic radiation includes a device for focusing the electromagnetic radiation responsive to a distance measurement provided by the at least one sensor.

11. The apparatus of claim 1, wherein the platform is mounted to a surface of the reservoir.

12. The apparatus of claim 1, wherein the platform is suspended within the reservoir by a vertically fixed support structure.

13. The apparatus of claim 1, wherein the platform is supported by a drive assembly operably configured for tilting the platform.

14. The apparatus of claim 13, wherein the drive assembly comprises a rotatable shaft extending through a side wall of the reservoir.

15. A method of fabricating a three-dimensional structure, comprising:

disposing a platform within a reservoir;

filling the reservoir with a volume of liquid curable to at least a semisolid state;

varying a surface level of the volume of liquid relative to the platform by one of moving a displacement structure into and out of the liquid and moving at least a portion of the reservoir relative to the platform; and

selectively curing portions of the volume of liquid to the at least a semisolid state with a source of electromagnetic radiation.

16. The method of claim 15, wherein varying the surface level of the volume of liquid comprises moving a displacement structure having an average density greater than a density of the liquid into and out of the volume of liquid.

17. The method of claim 15, wherein varying the surface level of the volume of liquid comprises moving a displacement structure into and out of the volume of liquid with a drive assembly comprising at least one of a cable, a stepper motor, and a screw drive.

18. The method of claim 15, wherein varying the surface level of the volume of liquid comprises moving at least one of a bottom or side portion of the reservoir relative to another portion of the reservoir.

19. The method of claim 15, wherein varying the surface level of the volume of liquid comprises raising and lowering the reservoir relative to the platform with a lift mechanism.

20. The method of claim 15, further comprising:

measuring a distance from at least one reference point above the reservoir to at least one location on the platform; and

reorienting the platform responsive to the distance measurement.

21. The method of claim 15, further comprising:

measuring a distance from at least one reference point above the reservoir to the surface level of the volume of liquid; and

focusing the source of electromagnetic radiation responsive to the distance measurement.

22. The method of claim 15, wherein disposing the platform within the reservoir comprises mounting the platform to a surface of the reservoir.

23. The method of claim 15, wherein disposing the platform within the reservoir comprises suspending the platform within the reservoir by a vertically fixed support structure.

24. The method of claim 15, further comprising tilting the platform within the reservoir with a drive assembly.

25. The method of claim 24, wherein tilting the platform within the reservoir comprises rotating the platform about a shaft extending through a side wall of the reservoir.