Method of and apparatus for measuring and controlling fluid level in stereolithography

• US 5,258,146 A
• Filed: 05/06/1992
• Issued: 11/02/1993
• Est. Priority Date: 09/26/1988
• Status: Expired due to Term

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Smalley, Dennis R., Cohen, Adam L., Lewis, Mark A., Almquist, Thomas A., Lewis, Charles W., Liran, Abraham, Jacobs, Paul F., Modrek, Borzo
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US07/880,190
• Time in Patent Office: 545 Days
• Field of Search: 264/22, 264/40.1, 264/40.2, 264/40.4, 264/308, 425/135, 425/140, 425/147, 425/174.4, 156/64, 156/273.5, 156/275.5, 156/307.1, 156/378, 156/379.6, 156/538, 427/8, 427/35, 427/36, 427/43.1, 427/44, 427/53.1, 427/54.1, 427/512, 427/553, 427/554, 118/423, 118/429, 118/500, 118/620, 118/712, 73/293, 73/305, 73/319, 73/322.5, 250/432 R, 250/492.1, 250/577, 340/619, 340/623, 340/624, 364/476, 365/106, 365/107, 365/119, 365/120, 365/126, 365/127
• US Class Current: 264/401
• CPC Class Codes: B29C 41/12 Spreading-out the material on a substrate , e.g. on the surface of a liquid
• 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: G01F 23/2921 for discrete levels
• CPC Class Codes: G01F 23/366 using optoelectrically actuated indicating means
• CPC Class Codes: G05D 9/12 characterised by the use of electric means
• CPC Class Codes: Y10T 156/17 Surface bonding means and/or assemblymeans with work feeding or handling means

Abstract

Improved apparatus and methods for forming a layer of material over a surface of a previously-formed cross-section of a three-dimensional object in anticipation of forming a next cross-section of the object out of the layer. A volume of material, including at least some excess material, is placed over the surface, and the excess material is swept off by placing the excess material in the predetermined path of a sweeping member, the path being substantially in a plane spaced from a working surface of material. The member may be directed to sweep the excess material away through a successive number of sweeps, which may vary for each cross-section, at least a velocity which may vary for each sweep. Additionally, the clearance between the member and the surface of the previous cross-section may vary for each sweep. A "winged" member is also provided, comprising two legs extending from a base, and a "Trident" embodiment is also provided, comprising three legs extending from a base.

Claims

1. A system for measuring the surface level of a fluid medium in a vessel of an apparatus for stereolithographically producing a three-dimensional object from the fluid medium, solidifiable by synergistic stimulation comprising:

a first chamber of said vessel for containing fluid medium;

a second chamber of said vessel connected to the first chamber with at least the fluid medium surface in the second chamber separated from the fluid medium surface in the first chamber; and

means for measuring the fluid medium surface level in the second chamber, thereby allowing the fluid medium surface level in the first chamber to be determined from the measured fluid medium surface level in the second chamber.

2. The apparatus of claim 1 wherein the means for measuring comprises:

a source for generating abeam of non-synergistic electromagnetic radiation;

a beam director for directing the beam along a first optical path to impinge on the surface of the fluid medium in the second chamber so that a detectable portion of the beam is reflected off the surface along a second optical path; and

a sensor that varies a signal in response to movement of the impinging electromagnetic beam across the sensor.

3. The apparatus of claim 2 wherein the source for generating a beam comprises a laser.

4. The apparatus of claim 2 wherein the sensor comprises a bi-cell.

5. The apparatus of claim 4 further comprising means for forming the signal from a difference of two separate signals generated by the bi-cell.

6. The apparatus of claim 1 wherein the first and second chambers are connected to allow intermixing of the fluid mediums between the chambers.

7. The apparatus of claim 1 wherein the means for measuring comprises:

means for generating and directing a measuring emission at the surface of the fluid medium in the second chamber; and

a sensor for sensing at least some of the measuring emission reflected from the surface of the fluid medium in the second chamber, said sensor having an output varying in response to the position of the measuring emission on the sensor, said output of the sensor indicative of the fluid medium level in at least one of the first and second chambers.

8. The apparatus of claim 1 further comprising means for positioning a previously formed layer of the object below the surface of the fluid medium in the first chamber a distance substantially equal to the thickness of the previously formed layer.

9. The apparatus of claim 2 wherein said first and second chambers are arranged such that the fluid medium surface in the first and second chambers are at the same level and the output from the sensor is indicative of the fluid medium level in both chambers.

10. The apparatus of claim 1 wherein said first chamber is adjacent said second chamber and is separated from the second chamber by a common wall having a submerged opening connecting the first and second chambers.

11. The apparatus of claim 9 wherein said first chamber and second chamber have substantially coplaner lower surfaces.

23. The apparatus of claim 1 further comprising means for adjusting the fluid medium surface level connected to the means for measuring the fluid medium surface level.

24. The apparatus of claim 23 wherein said means for adjusting comprises a plunger displaceable into and of the fluid medium.

25. The apparatus of claim 24 further comprising a motor for moving the plunger into and out of the fluid medium.

26. The apparatus of claim 25 further comprising a feedback loop between the motor and the means for measuring the fluid medium surface level.

27. The apparatus of claim 2 wherein the sensor is fixed in position with respect to the second chamber.

28. The apparatus of claim 2 further comprising a mirror fixed in position with respect to the second chamber for directing the beam.

34. The method of claim 2 wherein the fluid medium and the second fluid medium are the same medium.

12. An apparatus for measuring the fluid medium level in a stereolithography system for producing a three-dimensional object on substantially a layer by layer basis from a fluid medium capable of solidification when subjected to prescribed stimulation comprising:

at least one chamber having a first designated area for forming and solidifying layers of medium to form the object, and a second designated area spaced apart for the first designated area; and

means for measuring the fluid medium level at the second designated area.

13. The apparatus of claim 12 wherein the first designated area is in a first chamber and the second designated area is in a second chamber of the apparatus.

14. The apparatus of claim 12 wherein the means for measuring comprises:

a source for generating a beam of non-synergistic electromagnetic radiation;

a beam director for directing the beam along a first optical path to impinge on the surface of the fluid medium in the second designated area so that a detectable portion of the beam is reflected off the surface along a second optical path; and

a sensor that varies a signal in response to movement of the impinging electromagnetic beam across the sensor.

15. The apparatus of claim 14 wherein the source for generating a beam comprises a laser.

16. The apparatus of claim 14 wherein the sensor comprises a bi-cell.

17. The apparatus of claim 16 further comprising means for forming the signal from a difference of two separate signals generated by the bi-cell.

29. The apparatus of claim 14 further comprising a reflector floating on the fluid medium surface for reflecting the beam to the sensor.

18. An apparatus for measuring fluid medium level in a stereolithography system for making a three-dimensional part on substantially a layer by layer basis by forming a layer of structure of solidified fluid medium onto a previous layer of structure formed from solidified fluid medium comprising:

a chamber for holding the fluid medium;

means for relatively displacing an upper surface of a previously formed layer of the object and the fluid medium surface; and

a detector for detecting the level of the fluid medium in the chamber when the previously formed layer of the object is displaced below the fluid medium surface substantially more than the thickness of the layer.

19. The apparatus of claim 18 wherein the means for measuring comprises:

a source for generating a beam of non-synergistic electromagnetic radiation;

a director for directing the beam along a first optical path to impinge on the surface of the fluid medium so that a detectable portion of the beam is reflected off the surface along a second optical path; and

a sensor that varies a signal in response to movement of the impinging electromagnetic beam across the sensor.

20. The apparatus of claim 19 wherein the source for generating a beam comprises a laser.

21. The apparatus of claim 19 wherein the sensor comprises a bi-cell.

22. The apparatus of claim 21 further comprising means for forming the signal from a difference of two separate signals generated by the bi-cell.

30. A method for measuring the level of a surface of a fluid medium, contained in a vessel, in preparation for formation of a layer of fluid medium over a previously formed layer of an object being stereolithographically formed on substantially a layer by layer basis comprising:

(a) relatively displacing the previously formed layer of the object below the final fluid medium level substantially more than the thickness of the layer to be formed; and

(b) determining a fluid medium level when the previously formed layer of the object is displaced below the surface of the fluid medium level substantially more than the thickness of the layer to be formed.

31. The method of claim 30 wherein the fluid medium is a photopolymer.

32. A method for measuring the level of a surface of a fluid medium, contained in a vessel, in preparation for formation of a thin uniform coating of the fluid medium over a previously formed layer of an object being stereolithographically formed on substantially a layer by layer basis comprising:

(a) containing the fluid medium in a first chamber of the vessel;

(b) containing a second fluid within a second chamber of the vessel operatively connected to the first chamber with at least the second fluid medium surface in the second chamber separated from the fluid medium surface in the first chamber; and

(c) measuring the second fluid medium surface level in the second chamber, thereby allowing the fluid medium surface level in the first chamber to be determined.

33. The method of claim 32 further comprising positioning the previously formed layer of the object below the surface of the fluid medium in the first chamber a distance substantially equal tot he thickness of the layer to be formed.

35. The method of claim 32 wherein the fluid medium and second fluid medium have different densities.

36. The method of claim 32 wherein the fluid medium is a photopolymer.

37. A method for measuring the fluid medium level in a system for stereolithographically producing a three-dimensional object on substantially a layer by layer basis from a fluid medium solidifiable under prescribed synergistic stimulating, comprising:

containing the fluid medium in at least one vat;

forming layers of the three-dimensional object in at least a first section of the at least one vat; and

measuring the surface level of the fluid medium in a second section of the at least one vat, with the second section spaced apart from the first section.

38. The method of claim 37 further comprising the steps of:

coating a previously formed layer of the object with fluid medium in preparation for forming a next layer of the object.

39. The method of claim 37 further comprising the step of adjusting the level of the fluid medium in the vat.