Precision three-dimensional manufacturing system

Abstract

To provide a three-dimensional (3D) manufacturing system that is configured to fabricate a 3D article, in which an underside of a build surface is aligned very precisely with a build plane.SOLUTION: There is provided a three-dimensional (3D) manufacturing system, comprising: a base; a resin vessel supported by the base; a tension ring; a vertical movement mechanism (VMM); an elevator coupled to the VMM; a build platform; a load sensor; and a controller. The resin vessel includes a transparent sheet that is tensioned by the tension ring. An upper surface of the transparent sheet above the tension ring defines a datum surface. The build platform includes a mechanism and has a build surface. When the build surface is pressed against the datum surface, the mechanism allows the build surface to rotate about a horizontal axis so as to be flush with the datum surface. When the build surface is raised above the datum surface, the mechanism locks in a parallel orientation of the build surface with respect to the datum surface.SELECTED DRAWING: Figure 1

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This non-provisional patent application claims priority to U.S. Provisional Patent Application No. 63 / 625,402, entitled "Precision Three-Dimensional Manufacturing System," by Samuel David Rohrbach et al., filed January 26, 2024, which is incorporated herein by reference under U.S.C. 119(e). [Technical Field]

[0002] The present disclosure relates to an apparatus and method for fabricating solid three-dimensional (3D) manufactured articles from radiation curable materials. More particularly, the present disclosure relates to an apparatus for manufacturing customized, highly precise 3D articles. [Background technology]

[0003] The use of three-dimensional (3D) printers to manufacture customized articles is rapidly increasing. One type of 3D printer is a stereolithography printer, whose general operating principle involves selective curing and solidification of a radiation-curable (i.e., photocurable) liquid resin. One type of stereolithography system includes a containment vessel containing the curable resin, a movement mechanism coupled to a support tray, and a light engine. The stereolithography system forms three-dimensional (3D) manufactured articles by selectively curing a layer of photocurable resin on a lower build surface of the support tray along a build plane. There is a desire to manufacture 3D articles with feature size tolerances of less than 10 microns, less than 5 microns, less than 2 microns, or even less than 1 micron. Summary of the Invention [Problem to be solved by the invention]

[0004] One challenge is to align the underside of the build surface very precisely with the build plane. [Means for solving the problem]

[0005] In a first aspect of the present disclosure, a three-dimensional (3D) manufacturing system is configured to fabricate a 3D article. The 3D manufacturing system includes a base, a resin container supported by the base, a tension ring, a vertical motion mechanism (VMM), an elevator coupled to the VMM, a build platform, a load sensor, and a controller. The resin container includes a transparent sheet tensioned by the tension ring. An upper surface of the transparent sheet above the tension ring defines a datum surface. The build platform includes a mechanism and has a build surface. When the build surface is pressed against the datum surface, the mechanism frictionlessly rotates the build surface about a horizontal axis until it is flush with the datum surface. When the build surface is lifted from the datum surface, the mechanism frictionally locks the build surface relative to the datum surface in a direction parallel to the build surface.

[0006] In a second aspect of the present disclosure, a three-dimensional (3D) manufacturing system configured to fabricate a 3D article includes a base, a resin container supported by the base, a tension ring, a vertical movement mechanism (VMM), an elevator coupled to the VMM, a build platform, a load sensor, and a controller.

[0007] The resin container is configured to contain a quantity of photocurable resin. The resin container includes a transparent sheet that forms a lower containment boundary for the photocurable resin. The transparent sheet is overlaid on a tension ring that applies tension to the transparent sheet below the build plane. The upper surface of the transparent sheet directly above the tension ring defines a reference plane.

[0008] The build platform includes a rod having a lower end, a base assembly, and a spring. The base assembly has a build surface opposite the build plane and the reference surface and is configured to support the 3D article during fabrication. The base assembly has an inner surface defining an internal recess (or, alternatively, an internal cavity defined by and at least partially contained within a portion of the base assembly). The recess has a lower section that is wider than the lower end of the rod and a tapered section that tapers upward to capture the lower end of the rod within the recess. The spring is disposed within the lower section of the recess and configured to apply a vertical force between the lower end of the rod and the base assembly. The tapered section restricts the vertical expansion of the spring by constraining the lower end of the rod.

[0009] The controller is configured to: (1) actuate the VMM to lower the elevator while monitoring signals from the load sensor; (2) determine initial contact between the build surface and the reference surface based on the signals from the load sensor; and (3) actuate the VMM to continue lowering the elevator a predetermined vertical distance while the spring compresses, the lower end of the rod disengages from the tapered section, and the base assembly pivots until the build surface is parallel to and engages the reference surface.

[0010] In one implementation, in step (2), the elevator's descent speed (S2) is relatively slower than the elevator's descent speed (S1) in step (1). In other words, after determining initial contact between the build surface and the reference surface (based on the signal from the load sensor), the elevator's descent speed is slowed from a relatively high speed (S1) to a relatively low speed (S2).

[0011] In another implementation, the controller is further configured to: (4) actuate the VMM to raise the elevator, while the spring is partially compressed and the lower end of the rod re-engages the tapered section to frictionally lock the build surface parallel to the reference surface as it is raised above the reference surface; (5) actuate the VMM to lower the elevator while continuing to monitor signals from the sensor; (6) based on detection of contact between the build surface and the reference surface, (7) actuate the VMM to raise the build surface; (8) position the build surface (or later the bottom surface of the 3D article) on the build plane; (9) actuate the light engine to selectively cure the photocurable resin across the build plane; and repeat steps (7) through (9) to complete fabrication of the 3D article in a layer-by-layer manner.

[0012] In yet another implementation, the rod includes a middle section or portion connected to a lower end, the lower end defining a partial spherical or spheroidal shape having a larger lateral diameter than the middle section of the rod and captured by the tapered section of the recess to limit the expansion of the spring. In other words, the middle section of the rod has a middle lateral dimension, and the lower end of the rod has a lower lateral dimension, the lower lateral dimension being larger than the middle lateral dimension. In a circular cross-sectional embodiment, the middle lateral dimension is the middle lateral diameter, and the lower lateral dimension is the lower lateral diameter, the lower lateral diameter being larger than the middle lateral diameter. Other cross-sectional shapes are possible for the rod portion, such as elliptical, square, polygonal, triangular, or irregular, without departing from the functionality of the independent claims.

[0013] In a further implementation, the build platform includes a washer between the spring and the lower end of the rod, which effectively transfers the force of the spring to the lower end of the rod and more effectively engages the spring.

[0014] In yet another implementation, the base assembly includes a base defining a shaping surface, an insert defining a recess, a lower portion of the insert tightly coupled to the base, and a sleeve tightly coupled to an upper portion of the insert. The coupling between the base and the insert and the coupling between the insert and the sleeve can be threaded. The insert can be fluidly sealed to the base via an O-ring. A face seal can seal the sleeve to the insert and / or the sleeve to the base. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is an isometric view of an embodiment of a three-dimensional (3D) manufacturing system for creating a three-dimensional (3D) article. [Figure 2] 1 is a cross-sectional view illustrating an embodiment of system components including a resin container, an elevator, and a build platform; [Figure 3] FIG. 1 is a cross-sectional view providing details of an embodiment of a build platform that supports a 3D article. [Figure 4] FIG. 1 is an isometric view of an embodiment of a resin container and build platform; [Figure 5A] FIG. 10 is a cross-sectional view of an embodiment of the lower portion of a build platform positioned within a resin container with the build surface above the reference surface. [Figure 5B] FIG. 10 is a cross-sectional view of an embodiment of the lower portion of a build platform positioned within a resin container, with the build surface engaging and parallel to a reference surface. [Figure 6] 1 is a simplified electrical block diagram of an embodiment of a three-dimensional (3D) manufacturing system for creating a 3D article. [Figure 7] 1 is a simplified flowchart of a method for manufacturing a 3D article. [Figure 8] 1 is a flowchart of an embodiment of a method for calibrating and orienting a build surface. DETAILED DESCRIPTION OF THE INVENTION

[0016] FIG. 1 is an isometric view illustrating an embodiment of a three-dimensional (3D) manufacturing system 2 for producing a 3D article 4. The 3D article 4 is generally a polymeric manufactured article that can be used for consumer, industrial, or biological applications. In describing the 3D system 2, mutually perpendicular axes X, Y, and Z are used. Axes X and Y are generally horizontal transverse axes. Axis Z is a vertical axis that generally coincides with the gravity reference. The use of the term "generally" implies that the limitations that are "generally" true are by design but within manufacturing tolerances. Additionally, the angular axes theta-X, theta-Y, and theta-Z are rotations about the X, Y, and Z axes, respectively. For purposes of illustration and explanation, a portion of the 3D manufacturing system 2 (or referred to as system 2 for simplicity) is shown in FIG. 2.

[0017] System 2 is partially contained within outer housing 6 and includes a rigid base 8. Base 8 is rigid in the sense that it is formed from a high stability and high modulus material such as granite, steel, titanium, and other metals. Supported by base 8 is a resin reservoir 10. Resin reservoir 10 defines a liquid containment structure 12 configured to support and contain photocurable resin 14.

[0018] The photocurable resin 14 is a liquid polymeric material configured to be selectively cured by the selective application of radiation. Photocurable resins generally include a monomer and a catalyst. The catalyst promotes polymerization and / or crosslinking of the monomer in response to irradiation. The photocurable resin 14 may also include other components, such as colorants, fillers, and additional polymeric materials. Photocurable resins 14 are commonly known in the field of 3D printing of plastic and biological 3D articles.

[0019] System 2 includes a vertical motion mechanism (VMM) 16 mechanically coupled to elevator 18. One embodiment of vertical motion mechanism 16 includes what is referred to as a motorized ball-bearing screw mechanism, or ball screw mechanism. The ball screw mechanism includes a vertically threaded shaft passing through a ball nut. The ball nut contains circulating steel balls and moves vertically. The vertically threaded shaft has a helical channel that engages the circulating steel balls. Elevator 18 includes the ball nut. A motor is coupled to the vertically threaded shaft and configured to selectively rotate the vertically threaded shaft. As the vertically threaded shaft rotates, the action of the vertically threaded shaft against the ball nut moves the elevator up or down depending on the direction of rotation. Such motion mechanisms are known in the art for precision positioning along vertical, horizontal, and diagonal axes. Other embodiments include lead screw and nut systems, rack and pinion mechanisms, or motorized belt and pulley systems, all of which are known in the art for linearly moving components along various axes.

[0020] Attached to the elevator is a build platform 20. The build platform 20 is for supporting the 3D article 4 being formed. Further details of the build platform 20 are provided below.

[0021] Beneath the resin container 10 is a light engine 22 (within the housing 6). The light engine 22 is configured to selectively illuminate a build plane 24 within the resin container 10. The build plane 24 is the planar area directly above the reference plane 34 (FIG. 2) or within 1 millimeter of the reference plane 34. The lateral extent of the build plane is the area in which the light engine 22 can selectively cure a layer of the photocurable resin 14.

[0022] In the illustrated embodiment, light engine 22 includes one or more projection-type light engines. Projection-type light engines are known in the art for stereolithography systems. Such light engines include a light source, a spatial light modulator, projection optics, and other optical components (such as refractive lenses or mirrors, converging and diverging lenses or mirrors, etc.). The spatial light modulator may include an array of movable mirrors (also known as a micromirror or "DMD" array), as is known in the art. Other light engines are possible, such as lasers steered by galvanometer mirrors or light-emitting diode (LED) array heads, as are known in the art for stereolithography.

[0023] System 2 includes a controller 25 controllably coupled to VMM 16, light engine 22, and various operating devices and sensors. Controller 25 includes a processor coupled to information storage. Information storage may include non-volatile or non-transitory storage, such as a hard drive or flash memory. The non-volatile or non-transitory storage stores software instructions that, when executed by the processor, enable controller 25 to operate portions, elements, and components of system 2. Controller 25 may be a single microcontroller located within housing 6 or may include multiple controllers internal and / or external to housing 6. Controllers may include one or more of microcontrollers, mobile computers, personal computers, desktop computers, servers, laptops, smartphones, and other computing devices known in the art for controlling systems and system components.

[0024] FIG. 2 is a cutaway view further illustrating components of system 2, including resin container 10, elevator 18, and build platform 20. Elevator 18 incorporates load sensor 26 configured to output a signal indicative of a vertical force acting on build platform 20. Load sensors such as load sensor 26 are also referred to as load cells or force transducers, as known in the art. In one embodiment, load sensor 26 includes a piezoelectric crystal that outputs a voltage that correlates to the force acting on the piezoelectric crystal. Load sensor 26 may also include amplification electronics for amplifying the voltage from the piezoelectric crystal and analog-to-digital conversion electronics for converting the analog signal to digital information, all of which are known in the force or load sensor art.

[0025] Resin container 10 is configured to contain photocurable resin 14 and includes a transparent sheet 28 and an outer wall 30. Transparent sheet 28 is tensioned over tension rings 32, which stretch and flatten transparent sheet 28. An upper surface 34 of transparent sheet 28 defines a datum 34 or reference plane 34 that laterally bounds build plane 24 and unsupported or lateral interior regions of transparent sheet 28.

[0026] In an exemplary embodiment, the transparent sheet 28 is "semi-transparent" in that it allows inhibitors such as oxygen to pass through. The transparent sheet is "transparent" in that it is transparent to radiation in the blue to ultraviolet wavelengths or from about 500 nm (nanometers) to 100 nm. One example of a suitable transparent sheet is an optically clear, gas-permeable fluoropolymer, such as Teflon® AF2400. Other polymeric sheet materials may also be suitable for particular applications.

[0027] The build platform 20 includes, among other components, a collar 36, a knob 37, a rod 38, a base assembly 40, and a spring 42. The knob 37 passes through the collar 36 and threads into the elevator 18, securing the build platform 20 to the elevator 18. The rod 38 includes an intermediate or body section 44 that is secured to the collar 36 and extends downward to a lower end 46.

[0028] The lower end 46 of the rod has a larger lateral dimension or side diameter than the body section 44. The lower end 46 generally has the surface geometry or shape of an ellipsoid or sphere. The spring 42 is compressed along a vertical axis Z, spacing the rod 38 and the base assembly 40 vertically apart along Z. The base assembly 40 defines a cavity that captures the lower end 46 of the rod 38, thereby limiting the vertical expansion of the spring 42.

[0029] FIG. 3 is a cross-sectional view showing the lower portion of the build platform 20 in greater detail. The base assembly 40 includes a base 48 and an insert 50. The insert 50 has a lower portion 52 that is tightly coupled to the base 48 by an O-ring 51. The insert 50 defines an internal recess 54 (or, alternatively, an internal cavity 54) that accommodates the lower end 46 of the rod 38. A conical inner surface 56 of the insert 50 defines a portion of the recess 54 that tapers upward. The lower portion of the internal recess 54 allows vertical movement and rotation of the lower end 46 of the rod 38 relative to the base 48. However, the conical inner surface 56 of the insert limits upward movement of the lower end 46 of the rod 38 relative to the base 48. In other words, the tapered section of the recess 54 vertically captures the (spherical or ellipsoidal) lower end 46 of the rod 38 relative to the base 48, limiting its upward movement.

[0030] 3, spring 42 applies a vertical compressive force between bottom end 46 and base 48. Bottom end 46 then presses against conical inner surface 56. In the illustrated embodiment, washer 58 is located between bottom end 46 and spring 42. Washer 58 transfers the force from spring 42 to bottom end 46.

[0031] The sleeve 60 is tightly bonded to the top 62 of the insert 50. The sleeve 60, together with a fluid seal (O-ring 51 and face seal 53 between the sleeve 60 and the insert 50), prevents the photocurable resin 14 from reaching the interior recess 54 that would otherwise impede linear and pivotal movement of the base assembly 40 relative to the lower end 46 of the rod 38. The base 48 of the base assembly 40 has a lower surface 64 on which the 3D article 4 is built in a layer-by-layer manner.

[0032] In an exemplary embodiment for the build platform 20, materials are used for their strength, modulus, and inertness characteristics. The rod 38, base 48, and sleeve 60 may be formed from titanium. The knob 37 and spring 42 may be formed from stainless steel. The collar 36 may be formed from aluminum. The insert 50 may be formed from a polymer such as polyoxymethylene (POM), a high performance acetal resin. The washer 58 may be formed from polyamide. Other materials are possible.

[0033] 2 and 3 also show 3D article 4 partially formed in a layer-by-layer manner on bottom surface 64 of base 48. 3D article 64 also has bottom surface 65, which is the bottom surface of the most recently formed layer.

[0034] Figure 4 is an isometric view of the resin container 10 and the build platform 20. In Figure 4, the base assembly 40 is lowered into the resin container 10. Figures 1 and 2 can be referred to as a "raised state A" for the elevator 18 and the build platform 20. Figure 4 can be referred to as a "lowered state B" for the elevator 18 and the build platform 20. As shown, the sleeve 60 extends sufficiently from the lower surface 64 to completely shield the rod 38 from the photocurable resin 14 contained within the resin container 10.

[0035] 5A and 5B show the lower ends of resin container 10 and build platform 20, with lower surface 64 above (5A) and flush with (5B) reference plane 34. As build platform 20 lowers and raises, a sequence of "mechanical events" occurs, resulting in the following:

[0036] (1. Downward Movement) In the raised state (A), the lower surface 64 is not in contact with the reference surface 34, and the vertically compressed spring 42 pushes the base assembly 40 downward from the lower end 46 of the rod 38. The lower end 46 presses upward against the conical inner surface 56 of the insert 50, thereby limiting the expansion of the spring 42. Additionally, the impact of the lower end 46 against the conical surface 56 frictionally resists rotation of the base assembly 40 about a horizontal axis (X, Y, or a combination of X and Y).

[0037] (2. Downward Movement): Because the lower surface 64 is not yet parallel to the reference surface 34, it initially contacts the reference surface 34 at a single point or location. The force of this initial contact is sufficient to cause a change in the signal from the load sensor 26. Friction between the lower end 46 and the conical surface 56 initially maintains the orientation of the lower surface 64 in a non-parallel orientation relative to the reference surface 34.

[0038] (3. Downward Movement): As rod 38 moves further downward, lower end 46 compresses spring 42 and disengages from conical surface 56. The frictional force between lower end 46 and conical surface 56 then decreases, allowing base assembly 40 to freely rotate about transverse axes X and Y relative to lower end 46.

[0039] (4. Downward Movement): As the rod moves further downward, the base assembly 40 rotates about the X and Y axes until it is parallel to the reference surface 34. When the rotation ends, the lower surface 64 is parallel to the reference surface 34 and presses against (is flush with) the reference surface 34, after which the downward movement of the rod 38 only further compresses the spring 42. Once the spring compression has increased somewhat, the downward movement stops. Figure 5B shows the moment between the downward and upward movement.

[0040] (5. Upward Movement): As rod 38 moves upward, spring 42 extends but maintains the force of lower surface 64 against reference surface 34. This continues until lower end 46 re-engages conical surface 56. Once lower end 46 engages conical surface 56, the orientation of base assembly 48 is frictionally locked parallel to reference surface 34 because the friction between conical surface 56 and lower end 46 prevents rotation about the X and / or Y axes.

[0041] (6. Upward Movement): As the rod moves further upward, the engagement of the lower end 46 of the rod 38 with the cone 56 causes the lower surface 64 of the base assembly 40 to lift off the reference surface, as shown in FIG. 5A. Details of this movement are described with reference to FIGS. 7 and 8.

[0042] FIG. 6 is a simplified electrical block diagram of system 2. Elements of FIG. 6 are described with respect to FIG. 1. Controller 25 is controllably coupled to vertical movement mechanism (VMM) 16, load sensor 26, light engine 22, and other components omitted from FIG. 6 for simplicity. Part of VMM 16 is an encoder that outputs information or data indicative of the height of elevator 18. Such an encoder may be optical, optically sensing small dark "tick marks" along a strip or disk of optically transparent or reflective material to determine distance. Encoders for tracking the position of vertical movement mechanisms are known in various technical fields, including two-dimensional and three-dimensional printers.

[0043] 7 is a flowchart illustrating a method 100 of operating the manufacturing system 2 to create or manufacture a 3D article 4. According to 102, various removable components are attached to the system 2, including the resin container 10 and the build platform 20. The photocurable resin 14 can be poured into the resin container 10 either before or after the resin container 10 is placed on the base 8. The build platform 20 is secured to the elevator 18 with two knobs 37. The exact order of these steps may vary.

[0044] According to 104, system 2 is operated to orient and calibrate build surface 64. Orientation is described above with respect to Figures 5A / B and "Sequence of Mechanical Events," and further described below with respect to Figure 8. Calibration is also described with respect to Figure 8.

[0045] Per 106, the build surface 64 or lower surface 65 is positioned in the build plane 24. The lateral (X and Y) extent of the build plane 24 is defined by the extent of selective illumination of the thin slab of photocurable resin 14 by the light engine 22. The lateral extent of the build plane is within the inner edge of the reference surface 34. Generally, the build plane is located vertically within a distance of 1 millimeter (mm) or less from the reference surface 34.

[0046] According to 108, light engine 22 operates to selectively illuminate build plane 24 to selectively cure a layer of photocurable resin 14 onto underside or face 65 (FIG. 3) of 3D article 4. Steps 106 and 108 are repeated to fully fabricate 3D article 4.

[0047] Figure 8 is a flow chart illustrating a method 200 for orienting and calibrating the build surface 64. Method 200 is a detailed embodiment of step 104 of method 100 (Figure 7). Method 200 begins with the elevator in a relatively elevated state, i.e., with the base assembly 40 above the resin container 10, as shown in Figure 1. All actions in Figure 8 are performed by the controller 25 running on the VMM 16 and monitoring the load sensor 26.

[0048] Per 202, the VMM 16 lowers the elevator 18 at a relatively high speed S0 until the lower surface 64 begins to enter the resin container 10, as shown in Figure 5A. Then, per 204, the VMM 16 lowers the elevator at a slower speed S1. Per 206, the load sensor 26 is monitored.

[0049] Initial contact is made between lower surface 64 and reference surface 34. Per 208, a signal from load sensor 26 indicates initial contact. In an exemplary embodiment, step 208 includes identifying an immediate change in the voltage versus time signal in load sensor 26. Also per 208, an initial VMM 16 encoder value is recorded, indicating the vertical height of elevator 18. Per 210, the VMM slows the downward speed to S2—in one embodiment, the speed is 1 millimeter per second. Per 212, spring 42 is compressed and begins to rotate so that lower surface 64 is parallel to reference surface 34. During this rotation, lower end 46 of rod 38 loses contact with conical surface 56. Before step 216, the elevator descends approximately 4 millimeters (mm), after which the downward movement stops.

[0050] At 214, the image forming surface 64 is forced parallel to the reference surface 34. At 216, the VMM 16 stops its downward movement and begins its upward movement. The force of the spring 42 keeps the image forming surface 64 pressed against the reference surface 34 until the lower end 46 of the rod 38 engages the conical surface 56. At 218, the engagement of the lower end 46 with the conical surface 56 locks the image forming surface 64 in a parallel orientation relative to the reference surface 34.

[0051] At 220, the VMM 16 raises the build surface 64 above the reference surface 34 and then stops moving. Also at 220, the VMM 16 begins its downward movement again at a very slow speed S3 (slower than S2, 50 microns per second in one embodiment). At 222, the load sensor 26 outputs a signal indicating that the build surface 64 has again contacted the reference surface 34. When this signal is detected, the vertical encoder value from the VMM 16 is stored. This identifies a height that provides a very accurate height for the reference surface 34, and therefore the build surface 24 (typically less than 1 mm above the reference surface 34, and more typically less than 0.1 mm above the reference surface 34). Identifying this accurate height allows for accurate positioning in step 106 of method 100 (FIG. 7).

[0052] The particular embodiments and applications described above are intended to be illustrative only and do not exclude modifications and variations encompassed by the scope of the following claims.

Claims

1. 1. A three-dimensional (3D) manufacturing system configured to fabricate a 3D article, comprising: base; a reference surface supported by said base; Vertical movement mechanism (VMM); an elevator coupled to said VMM; a build platform coupled to said elevator; controller Equipped with The build platform comprises: a rod having a lower end; A base assembly defining: a build surface facing the reference surface and configured to support the 3D article; an internal recess having a lower section wider than the lower end of the rod and a tapered section tapering upwardly to capture the lower end of the rod within the internal recess; a spring within the internal recess and configured to apply a vertical force between the lower end of the rod and the base assembly, the tapered section limiting the vertical expansion of the spring; Including, The controller is configured to: (1) actuating the VMM to lower the elevator while the spring presses the lower end of the rod against the tapered section until the base assembly first engages the reference surface; (2) Activating the VMM further lowers the elevator and compresses the spring, causing the lower end of the rod to disengage from the tapered section and the base assembly to begin pivoting about the lower end of the rod until the build surface is parallel to and engages the reference surface. A 3D manufacturing system.

2. a resin container including a transparent sheet forming a lower encapsulation boundary for a photocurable resin within the resin container; a tension ring, the upper surface of the transparent sheet overlying the tension ring defining the reference plane; and a light engine configured to selectively illuminate the photocurable resin on a build plane adjacent to and above the transparent sheet; The 3D manufacturing system of claim 1 further comprising:

3. 2. The 3D manufacturing system of claim 1, wherein the rod includes a mid-section coupled to the lower end, the lower end defining a partial spherical or spheroidal shape having a larger side diameter than the mid-section of the rod and captured by a tapered section of the internal recess to limit the expansion of the spring.

4. The 3D manufacturing system of claim 1 , further comprising a washer between the spring and the lower end of the rod.

5. the base assembly a base defining said shaping surface; an insert defining the interior recess, a lower portion of the insert being tightly coupled to the base; and A sleeve tightly bonded to the top of the insert The 3D manufacturing system of claim 1 , comprising:

6. The 3D manufacturing system of claim 1 , further comprising a load sensor configured to output a signal indicative of a normal force on the build surface.

7. The controller is further configured to: (3) activating the VMM to raise the elevator at least until the lower end of the rod impacts the tapered section of the internal recess, locking the orientation of the build surface parallel to the reference plane; 2. The 3D manufacturing system of claim 1.

8. The controller is further configured to: (4) actuating the VMM to position the lower surface on the reference surface; (5) Store the vertical encoder value indicating the height of the reference plane.

8. The 3D manufacturing system of claim 7.

9. 1. A method of manufacturing a 3D article, comprising: Providing a 3D manufacturing system, the 3D manufacturing system comprising: base; a reference surface supported by said base; Vertical movement mechanism (VMM); an elevator coupled to said VMM; a build platform coupled to the elevator, a rod having a lower end; A base assembly defining: a build surface facing the reference surface and configured to support the 3D article; an interior surface defining an interior recess having a lower section wider than the lower end of the rod and a tapered section tapering upwardly to capture the lower end of the rod within the interior recess; a spring within the internal recess and configured to apply a vertical force between the lower end of the rod and the base assembly, the tapered section limiting the vertical expansion of the spring; a build platform including: a process comprising: actuating the VMM to lower the elevator while the spring presses the lower end of the rod against the tapered section until the base assembly first engages the reference surface; actuating the VMM to further lower the elevator and compress the spring, causing the lower end of the rod to disengage from the tapered section and the base assembly to begin pivoting about the lower end of the rod until the build surface is parallel to and engages the reference surface. A method comprising:

10. the 3D manufacturing system comprises: a resin container including a transparent sheet forming a lower encapsulation boundary for a photocurable resin within the resin container; a tension ring, the upper surface of the transparent sheet overlying the tension ring defining the reference plane; and a light engine configured to selectively illuminate the photocurable resin on a build plane adjacent to and above the transparent sheet; Furthermore, The method further includes operating the VMM mechanism and the light engine to create the 3D article.

10. The method according to claim 9.

11. (3) activating the VMM to raise the elevator at least until the lower end of the rod collides with the tapered section of the internal recess and locks the orientation of the build surface parallel to the reference surface; 10. The method of claim 9, further comprising:

12. 12. The method of claim 11, further comprising the steps of: (4) activating the VMM to position the lower surface on the reference surface; and (5) storing a vertical encoder value indicating the height of the reference surface.

13. 1. A three-dimensional (3D) manufacturing system configured to fabricate a 3D article, comprising: base; a resin container supported by the base, the resin container including a transparent sheet that forms a lower encapsulation boundary for a photocurable resin within the resin container, a tension ring, and an upper surface of the transparent sheet that overlaps the tension ring and defines a reference plane; Vertical movement mechanism (VMM); an elevator coupled to said VMM; a build platform coupled to said elevator; a load sensor configured to output a signal indicative of an upward force exerted on the build platform; a light engine configured to selectively illuminate the photocurable resin on a build surface located above the transparent sheet; and controller Equipped with The build platform comprises: a rod having a lower end; A base assembly defining: a build surface facing the reference surface and configured to support the 3D article; an internal recess having a lower section wider than the lower end of the rod and a tapered section tapering upwardly to capture the lower end of the rod within the internal recess; a spring within the internal recess and configured to apply a vertical force between the lower end of the rod and the base assembly, the tapered section limiting the vertical expansion of the spring; Including, The controller is configured to: (1) activating the VMM to lower the elevator while monitoring the signal from the load sensor; (2) determining initial contact between the build surface and the reference surface based on signals from the load sensor; and (3) activating the VMM to continue to lower the elevator a predetermined vertical distance while the spring is compressed, the lower end of the rod disengages from the tapered section, and the base assembly pivots until the build surface is parallel to and engages the reference surface; A 3D manufacturing system.

14. 14. The 3D manufacturing system of claim 13, wherein during step (2), the elevator's downward speed (S2) is reduced relative to the elevator's downward speed (S1) during step (1).

15. The controller is further configured to: (4) activating the VMM to raise the elevator while the spring is partially compressed and the lower end of the rod re-engages the tapered section to frictionally lock the build surface parallel to the reference surface as the build surface is raised above the reference surface; 14. The 3D manufacturing system of claim 13.

16. The controller is further configured to: (5) activating the VMM to move the elevator down while continuing to monitor signals from the sensors; and (6) Recording information indicating the height of the reference surface based on the detection of contact between the build surface and the reference surface.

16. The 3D manufacturing system of claim 15.

17. The controller is further configured to: (7) actuating the VMM to raise the build surface; (8) positioning the build surface on the build plane; (9) activating the light engine to selectively cure the photocurable resin across the build plane; and (10) Repeating steps (7) through (9) to complete the fabrication of the 3D article in a layer-by-layer manner.

17. The 3D manufacturing system of claim 16.

18. 14. The 3D manufacturing system of claim 13, wherein the rod includes a mid-section coupled to the lower end, the lower end defining a partial spherical or spheroidal shape having a larger side diameter than the mid-section of the rod and captured by a tapered section of the internal recess to limit the expansion of the spring.

19. 14. The 3D manufacturing system of claim 13, further comprising a washer between the spring and the lower end of the rod.

20. the base assembly a base defining said shaping surface; an insert defining the interior recess, a lower portion of the insert being tightly coupled to the base; and A sleeve tightly bonded to the top of the insert 14. The 3D manufacturing system of claim 13, comprising:

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