Apparatus and method for calibrating and normalizing a stereolithographic apparatus

• US 5,123,734 A
• Filed: 11/08/1988
• Issued: 06/23/1992
• Est. Priority Date: 04/18/1988
• Status: Expired due to Term

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Almquist, Thomas, Tarnoff, Harry L., Spence, Stuart T.
• Primary Examiner(s): Rosenberger, Richard A.
• Assistant Examiner(s): Pham, Hoa
• Application Number:
  US07/268,837
• Time in Patent Office: 1,323 Days
• Field of Search: 356/121-123, 356/237, 356/356, 356/355, 356/153, 356/375, 356/400, 250/347, 250/239, 425/174, 425/174.1, 425/174.4, 164/35, 264/22
• US Class Current: 356/121
• CPC Class Codes: B29C 64/135 the energy source being concentrated, e.g. scanning lasers or focused light sources
• CPC Class Codes: B29C 64/40 Structures for supporting 3D objects during manufacture and intended to be sacrificed after completion thereof
• 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 50/00 Data acquisition or data processing for additive manufacturing
• CPC Class Codes: G01J 1/4257 applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam monitoring arrangements for lasers in general H01S3/0014
• CPC Class Codes: G03F 7/0037 Production of three-dimensional images
• CPC Class Codes: G03F 7/70416 2.5D lithography
• CPC Class Codes: G05B 2219/49013 Deposit layers, cured by scanning laser, stereo lithography SLA, prototyping
• CPC Class Codes: G06T 17/00 Three dimensional [3D] modelling, e.g. data description of 3D objects
• CPC Class Codes: G06T 17/10 Constructive solid geometry [CSG] using solid primitives, e.g. cylinders, cubes
• CPC Class Codes: G06T 17/20 Finite element generation, e.g. wire-frame surface description, tesselation

Abstract

An apparatus and a method for calibrating and normalizing a stereolithographic apparatus so that a reaction means directed by a positioning means supplied with positioning means information may be positioned accurately on a designated surface of a working medium. One or more sensors fixed in location with respect to the designated surface of the working medium are utilized to correlate positioning means information with specific locations on the designated surface of the working medium. Other locations intermediate the specific locations may then be determined by the technique of linear interpolation.

Claims

1. In a stereolithographic machine for the production of a three-dimensional object from a medium capable of solidification when exposed to a reaction means operating in a prescribed manner upon a designated working surface of the medium defining a working region of the machine to solidify successive adjacent laminae forming the object, the improved of an apparatus for calibration and normalizing the machine prior to operation of the machine to make a three-dimensional object, comprising:

(a) at least one sensor located at a plurality of predetermined locations within the working region prior to forming the three dimensional object, and removed from the working region prior to forming the three-dimensional object, for sensing when the reaction means is pointed at each predetermined location;

(b) a positioner for positioning the reaction means in response to positioner information;

(c) a first memory for receiving selected positioner information and corresponding predetermined location information for each of the plurality of predetermined locations, the selected positioner information for a predetermined location corresponding to the positioner information when the positioner directs the reaction means on to the at least one sensor when the at least one sensor is located at the predetermined location;

(d) a second memory for receiving data representing a laminae of the three-dimensional object to be formed wherein the data represents desired spatial relationships between a plurality of points to be solidified; and

(e) a processor connected to the at least one sensor, the positioner, and the first and second memory and programmed to use the selected positioner information and the corresponding predetermined location information to map the data which represents desired spatial relationships between the plurality of points to be solidified to calibrate positioner information to accurately position the reaction means on the working surface.

2. The apparatus of claim 1 wherein the processor includes means for carrying out linear interpolation between adjacent values of said selected positioner information for providing calibrated intermediate positioner information for directing said positioner.

3. The apparatus of claim 1 wherein the reaction means is a laser beam.

4. The apparatus of claim 1 wherein the medium is a photopolymerizable liquid.

5. A method for calibrating and normalizing a stereolithographic machine for the production of a three-dimensional object from a medium capable of solidification when exposed to a reaction means operating in a prescribed manner upon a designated working surface of the medium defining a working region of the machine to solidify successive adjacent laminae forming the object, prior to operation of the machine to produce a three-dimensional object, comprising the following steps:

(a) temporarily locating at least one sensor at a plurality of predetermined locations within the working region prior to forming the three-dimensional object to sense when the reaction means is pointed at each predetermined location;

(b) positioning the reaction means using a positioner responsive to positioner information;

(c) receiving in a first memory selected positioner information and corresponding predetermined location information for each of the plurality of predetermined locations, said selected positioner information for a predetermined location corresponding to the positioner information when the positioner directs the reaction means onto the at least one sensor when the at least one sensor is located at the predetermined location;

(d) receiving in a second memory data representing a laminae of a three-dimensional object to be formed wherein the data represents desired spatial relationships between a plurality of points to be solidified;

(e) using the selected positioner information and the corresponding predetermined location information to map the data, which represents desired spatial relationships between the plurality of points to be solidified, to calibrated positioner information, to accurately position the reaction means onto the working surface; and

(f) removing said at least one sensor from the working region prior to forming the three-dimensional object.

6. The method of claim 5 further comprising the following steps:

(e) positioning the reaction means onto the working surface in response to linear interpolations between adjacent values of said selected positioner information for providing calibrated intermediate positioner information.

7. The method of claim 5 wherein the reaction means is a beam and the recording in memory step comprises generating a location lookup table, further comprising the steps of:

determining a scanning speed lookup table from the information in the location lookup table;

directing the beam to move over the designated working surface of the medium according to a scanning speed parameter;

maintaining a desired scanning speed at a particular beam position by modifying the scanning speed parameter according to the beam position using the scanning speed lookup table.

8. In a stereolithographic machine for the production of a three-dimensional object from a medium capable of solidification when exposed to a solidifying reaction means operating in a prescribed manner upon a designated working surface of the medium defining a working region of the machine to solidify successive adjacent laminae forming the object, the improvement of an apparatus for calibrating and normalizing the machine, comprising:

(a) at least one sensor located at a plurality of predetermined locations within the working region prior to forming the three-dimensional object, for sensing when the solidifying reaction means is pointed at each predetermined location;

(b) means for removing said at least one sensor from the working region prior to forming the three-dimensional object;

(c) a positioner for positioning the solidifying reaction means in response to positioner information;

(d) a memory for recording and storing selected positioner information and corresponding predetermined location information for each of the plurality of predetermined locations, the selected positioner information for a predetermined location corresponding to the positioner information when the positioner directs the solidifying reaction means on to the at least one sensor when the at least one sensor is located at the predetermined location; and

(e) a controller linked to the positioner and memory and supplied with uncalibrated data corresponding to a plurality of desired points on the working surface to be solidified and having a desired spatial relationship, said controller having means for making positioner control computations using selected positioner information, corresponding predetermined location information, and uncalibrated data to determine calibrated positioner information, for directing the positioner to direct the solidifying reaction means to the plurality of desired points on the working surface wherein the calibrated positioner information produces the desired spatial relationship of the plurality of desired points as the solidifying reaction means solidifies the medium at the plurality of desired points.

9. The apparatus of claim 8 wherein the reaction means is a laser beam.

10. The apparatus of claim 8 wherein the medium is a photopolymerizable liquid.

11. The apparatus of claim 8, wherein at least a substantial number of the plurality of predetermined locations are located within the working region of the machine.

12. The apparatus of claim 11, wherein the at least substantial number of the plurality of predetermined locations form a calibration plate which is located substantially coplanar with the designated working surface.

13. A method for calibrating and normalizing a stereolithographic machine for production of a three-dimensional object from a medium capable of solidification when exposed to a solidifying reaction means operating in a prescribed manner upon a designated working surface of the medium defining a working region of the machine to solidify successive adjacent laminae forming the object, comprising the steps of:

(a) locating at least one sensor at a plurality of predetermined locations within the working region prior to forming the three-dimensional object, to sense when the solidifying reaction means is pointed at each predetermined location;

(b) positioning the solidifying reaction means by use of a positioner responsive to positioner information;

(c) recording in a memory selected positioner information and corresponding predetermined location information for each of a plurality of predetermined locations, said selected positioner information for a predetermined location corresponding to the positioner information when the positioner directs the solidifying reaction means on to the at least one sensor when the at least one sensor is located at the predetermined location; and

(d) computing calibrated positioner information from uncalibrated data corresponding to a plurality of desired points on the working surface to be solidified having a desired spatial relationship using the selected positioner information, corresponding predetermined location information, and said uncalibrated data, and providing the calibrated positioner information to the positioner to direct the solidifying reaction means to the plurality of desired points on the working surface to achieve the desired spatial relationship of the desired points upon solidification; and

(e) removing said at least one sensor from the working region prior to forming the three-dimensional object.

14. The method of claim 13 wherein said reaction means is a laser beam.

15. The method of claim 13, wherein at least a substantial number of the plurality of predetermined locations are located within the working region of the machine.

16. The method of claim 15, wherein the at least substantial number of the plurality of predetermined locations form a calibration plate which is located substantially coplanar with the designated working surface.

17. In a stereolithographic machine for the production of a three-dimensional object from a medium capable of solidification when exposed to a beam of radiation operating in a prescribed manner upon a designated working surface of the medium defining a working region of the machine to solidify successive adjacent laminae forming the object the improvement of an apparatus for calibrating and normalizing the machine, comprising:

(a) a positioner for positioning the beam in response to positioner information;

(b) at least one sensor located at a plurality of predetermined locations within the working region prior to forming the three-dimensional object, for sensing an intensity value when a portion of the beam is pointed at each predetermined location;

(c) means for removing said at least one sensor from the working region prior to forming the three-dimensional object;

(d) a first memory for receiving particular positioner information, corresponding predetermined location information, and intensity value information for each portion of the beam for each of the plurality of predetermined locations, the particular positioner information for a predetermined location corresponding to the positioner information when the positioner directs the portion of the beam on to the at least one sensor when the at least one sensor is located at the predetermined location;

(e) a processor programmed to calculate a centroid-like function from the particular positioner information and the intensity information for each portion of the beam for each predetermined location to determine best positioner information corresponding to each predetermined location;

(f) a second memory linked to the first memory and processor, for receiving data representing a laminae of a three-dimensional object to be formed wherein the data represents desired spatial relationships between a plurality of points to be solidified; and

(g) the processor including means for using the best positioner information and the corresponding predetermined location information from the plurality of predetermined locations to map the data, which represents desired spatial relationships between the plurality of points to be solidified, to calibrate positioner information to accurately position the beam onto the working surface.

18. A method for calibrating and normalizing a stereolithographic machine for the production of a three-dimensional object from a medium capable of solidification when exposed to a beam of solidifying radiation operating in a prescribed manner upon a designated working surface of the medium defining a working region of the machine to solidify successive adjacent laminae forming the object, comprising:

(a) positioning the beam in response to positioner information;

(b) using at least one sensor located at a plurality of predetermined locations within the working region prior to formation of a three-dimensional object, for sensing an intensity value when a portion of the beam is pointed at each predetermined location;

(c) receiving particular positioner information, corresponding predetermined location information, and intensity value information for each portion of the beam for each of the plurality of predetermined locations, the particular positioner information for a predetermined location corresponding to the positioner information when the positioner directs the portion of the beam on to the at least one sensor when the at least one sensor is located at the predetermined location;

(d) determining best positioner information corresponding to each predetermined location by calculating a centroid-like function from the particular positioner information and the intensity information for each portion of the beam for each predetermined location;

(e) receiving data representing a laminae of a three-dimensional object to be formed wherein the data represents desired spatial relationships between a plurality of points to be solidified;

(f) using the best positioner information and the corresponding predetermined location information from the plurality of predetermined locations to map the data, which represents desired spatial relationships between the plurality of points to be solidified, to calibrated positioner information to accurately position the beam onto the working surface; and

(g) removing said at least one sensor from the working region prior to forming the three-dimensional object.