Method for producing low modulus articles

Abstract

A method for manufacturing a 3D article includes operating a 3D printing system including an elevator (14) coupled to a vertical movement mechanism and a distance sensor (58). The elevator includes an elevator actuator. The vertical movement mechanism is coupled to the elevator. A build platform includes a build plate having a lower surface. The method includes loading the build platform onto the elevator, operating the vertical movement mechanism to lower the lower surface of the build platform into a measurement range of the distance sensor, scanning the distance sensor along a horizontal axis, receiving signals from the distance sensor indicative of multiple vertical positions along the horizontal axis of the lower surface of the build platform while scanning the distance sensor, and operating the elevator actuator to adjust the height of the lower surface of the build platform.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This non-provisional patent application claims priority to U.S. Provisional Patent Application No. 63 / 484,354, entitled "Method for Manufacturing Low Modulus Articles," by David Sabo et al., filed February 10, 2023, which is incorporated by reference herein 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] Three-dimensional (3D) printers are rapidly increasing in use for manufacturing customized articles. One class of 3D printers includes stereolithography printers, which have a general operating principle involving selective curing and solidification of a radiation-curable (i.e., photocurable) liquid resin. One type of stereolithography system includes a reservoir that holds 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 the underside of the support tray. It is desirable to effectively manufacture 3D articles with feature size tolerances of less than 10 microns, less than 5 microns, or even less than 2 microns. Summary of the Invention [Problem to be solved by the invention]

[0004] Various challenges in fabricating such small geometries include limitations on optical and mechanical systems historically suited to tolerances in the 20 micron range or greater. [Means for solving the problem]

[0005] A first aspect of the present disclosure is a method for manufacturing a three-dimensional (3D) article using a 3D printing system. The 3D printing system includes an elevator, a vertical movement mechanism, a build platform, and an imaging module. The elevator is configured to translate along a vertical axis and includes an elevator actuator. The vertical movement mechanism is coupled to the elevator. The build platform includes a build plate having a lower surface. The imaging module includes a light engine and a distance sensor. The method includes mounting the build platform on the elevator, operating the vertical movement mechanism to lower the lower surface of the build platform into a measurement range of the distance sensor, scanning the imaging module along at least one horizontal axis, receiving signals from the distance sensor simultaneously with the scanning of the distance sensor indicating multiple vertical positions of the lower surface of the build platform along the horizontal axis, calculating a tilt of the lower surface of the build platform based on the signals from the distance sensor, and operating the elevator actuator to level the lower surface of the build platform. The distance sensor can be one or more confocal distance sensors. Other distance sensors, such as laser displacement sensors, can be used. The light engine may include one or more projection light engines.

[0006] Activating an actuator within the elevator to level the underside of the build platform allows for more accurate imaging of the 3D article. In fact, this leveling method allows for dimensional tolerances that are an order of magnitude smaller than conventional 3D printing systems. The implementations listed below further enable precise imaging.

[0007] In one implementation, the elevator includes (a) a lower support including an elevator actuator extending upward from an upper portion of the lower support, and (b) an upper support including a reference surface at a lower portion that engages the elevator actuator. The method includes operating the actuator to adjust the orientation of the upper support relative to the lower support and relative to a horizontal axis.

[0008] In another implementation, an elevator includes a lower support and an upper support. The lower support has an upper portion. The upper support includes a lower portion including three reference surfaces. The lower support includes a pin and two elevator actuators extending upward from the upper portion and engaging the three reference surfaces. Operation of the two elevator actuators adjusts the orientation of the upper support along two orthogonal axes.

[0009] In yet another implementation, the build platform includes a support plate having a lower surface and a plurality of vertical rods connecting the lower surface of the support plate to the upper surface of the build plate, and mounting the build platform on the elevator includes mounting the lower surface of the support plate on the upper surface of the elevator.

[0010] In a further implementation, the elevator includes at least one electromagnet. The build platform includes a support plate having a lower surface and a plurality of vertical rods connecting the lower surface of the support plate to an upper surface of the build plate. Mounting the build platform on the elevator includes mounting the lower surface of the support plate to the upper surface of the elevator and activating the at least one electromagnet.

[0011] In a further implementation, the light engine includes a plurality of light engines. The method includes scanning and operating the plurality of light engines to image the layer of light curable resin.

[0012] In another implementation, a 3D printing system includes a rigid base, a vertical beam extending upward from the rigid base, and a plurality of actuators extending upward from the rigid base. The method includes mounting a build container on the rigid base, engaging the plurality of actuators, scanning an imaging module along at least one horizontal axis along a lower surface of the build container, receiving signals from a distance sensor indicating a plurality of vertical positions along the horizontal axis of an inner surface of the build container while scanning the imaging module, and operating the plurality of actuators to adjust the height of the lower surface of the build container. The inner surface of the build container can be the upper surface of a glass plate supporting a flexible transparent sheet. The upper surface of the glass plate can provide a mechanical reference surface for the transparent sheet.

[0013] In a second aspect of the present disclosure, a three-dimensional (3D) printing system configured to print 3D articles in a layer-by-layer manner includes a vertical beam, an elevator, and a build platform. The elevator is configured to translate vertically along the vertical beam and includes an upper support and a lower support. The lower support includes at least one elevator actuator extending upward from the upper portion. The upper support has a lower portion including a reference surface engaged with the actuator. The elevator actuator is configured to change the vertical height of the reference surface above the upper portion of the lower actuator to adjust the tilt of the upper portion of the upper support. The build platform includes a build plate coupled below the support plate. The build plate has a lower portion for forming the 3D article. The support plate has a lower portion that engages an upper side of the elevator upper support to support the build platform. The elevator actuator can include two elevator actuators configured to change the vertical height of the upper support relative to the lower support, with or without a net rotation about one or two horizontal axes X and Y. The two elevator actuators can independently adjust the tilt of the upper support about one of two horizontal axes, X or Y (θ-X or θ-Y). In combination, the two elevator actuators can adjust the tilt about two horizontal axes, X and Y (θ-X and θ-Y).

[0014] The elevator includes lower and upper supports—the tilt of the upper support is adjusted by an elevator actuator—allowing for mechanical compensation for mechanical tolerances and / or fluid resistance. The elevator (and other parts of the 3D printing system) are configured to ensure a uniform layer of resin between the build plate and the transparency sheet. This uniformity allows for the production of 3D articles with dimensional tolerances that can be less than 10 microns, less than 5 microns, less than 2 microns, or even less than 1 micron. Pixels or voxels can be defined with vertical steps of less than 10 microns, or even 5 microns or less.

[0015] In one implementation, the 3D printing system includes a controller including a processor coupled to a storage device. The storage device stores software instructions that, when executed by the processor, enable the controller to operate parts and elements of the 3D printing system. This includes operating an elevator actuator to adjust the height and tilt of the elevator's upper support, thereby lowering or leveling the underside of the build plate to coincide with a horizontal surface. This allows the underside of the build platform to be lowered to less than 10 microns or approximately 5 microns from the transparency sheet. This therefore allows for layer thicknesses and pixel sizes of approximately 5 microns.

[0016] In another implementation, the elevator includes a force sensor configured to output a signal indicative of a force exerted on the elevator by the platform. The 3D printing system includes a controller configured to analyze the signal and determine a vertical position error of the build plate when the lower surface of the build plate is moved to the build plane. The controller is configured to address the vertical position error by vertically translating the build plate a distance of less than 20 microns. The controller can also determine an angular tilt or tilt error of the underside of the build plate. The controller is configured to respond to the determination by operating an actuator to correct the error and vertically translate and / or level the lower portion of the build plate.

[0017] In yet another implementation, a 3D printing system includes a distance sensor and a controller. The controller is configured to operate the distance sensor to scan a bottom of a build plate and receive signals from the sensor during the scan. The controller is configured to analyze the signals and determine a vertical position error and / or an angular tilt or tilt error of the bottom of the build plate. The controller is configured to respond to the determination by operating an actuator to correct the errors and vertically translate and / or level the bottom of the build plate.

[0018] In a further implementation, the 3D printing system includes a controller, a rigid base, an imaging module, a plurality of base actuators extending upward from the rigid base, and a build container. When the build container is placed on the rigid base, it is engaged by the plurality of base actuators. The controller is configured to scan a lower surface of the build container with the imaging module. The imaging module outputs a signal indicating the height of a point on the lower surface of the build container being scanned. The controller is configured to determine height and / or tilt errors of the lower surface of the build container and operate the plurality of base actuators to correct the height and / or tilt errors. The plurality of base actuators can include three base actuators, enabling height error correction along a vertical axis Z and tilt error correction along two axes θ-X and θ-Y.

[0019] In yet another embodiment, the elevator lower support includes an upwardly extending pin, and the elevator actuator includes two elevator actuators. The upper support includes three datums having reference surfaces positioned and configured to engage the pin and the two elevator actuators. The two elevator actuators are configured to adjust the height, tilt, or inclination of the elevator upper support about the pin and two horizontal axes θ-X and θ-Y.

[0020] A third aspect of the present disclosure is a method for manufacturing a three-dimensional (3D) article using a 3D printing system. The 3D printing system includes a rigid base, a vertical beam extending above the rigid base, an elevator configured for vertical translation along the vertical beam, the elevator including an elevator actuator and a force sensor, a vertical translation mechanism coupled to the elevator, a build platform including a build plate having a lower surface, a build vessel containing a photocurable resin and having a lower portion with a transparent sheet, an imaging module, and a controller. The method includes mounting the build platform on the elevator, operating the vertical translation mechanism to translate the lower surface of the build plate through the resin toward the build plane, where the photocurable resin applies a force to the elevator that translates and / or rotates the lower surface of the build plate away from the build plane, receiving a signal from the force sensor, operating the controller to calculate a positional deviation between the lower surface of the build plate and the build plane due to an external force based on the signal from the force sensor, and operating the elevator actuator to correct the positional deviation. The force applied to the elevator can have a torque component, and the misalignment correction can include both a vertical displacement and a rotational component.

[0021] 3D printing systems are fabricated from thick, rigid materials such as tool steel and granite plates. However, the fluid resistance of the underside of the build plate as it is translated through the photopolymerizable resin to the build plane is sufficient to induce vertical and / or angular displacement, making it difficult to precisely position the underside of the build plate on the build plane and limiting the machine's resolution to layer thicknesses of 10 or 20 microns or less. Actuating actuators to offset the displacement allows for a closer approach to the build plane, enabling thinner layer thicknesses of less than 10 microns, or even 5 microns or less.

[0022] In one implementation, the elevator includes a lower support further including an elevator actuator extending upward from an upper portion of the lower support, and an upper support including a reference surface, a lower portion of which is engaged with the elevator actuator. The method includes operating the elevator actuator to adjust the orientation of the upper support relative to the lower support and a horizontal plane. The lower support may include a pin extending upward from an upper portion of the lower support. A lower portion of the upper support may include a reference that engages with the pin and self-centers on the pin. Operating the elevator actuator can rotate the upper support about the pin. The force sensor can be a load cell coupled between the pin and the lower support. Receiving a signal from the sensor can be receiving a signal from the load cell indicative of the force of the pin reference against the pin. The elevator actuator can include two elevator actuators. Operating the elevator actuator can include selectively rotating the upper support about two horizontal axes. The lower support can include a proximal portion slidably coupled to the vertical beam and a distal portion extending along the horizontal axis X away from the vertical beam. The pin can be located on the distal portion. Two elevator actuators can be located on the proximal portion on opposite sides of the vertical beam relative to a second transverse axis Y. Operation of the two elevator actuators can selectively raise, lower, and / or rotate the proximal portion relative to the distal portion. The transverse axes X and Y are perpendicular to each other and generally horizontal.

[0023] In another implementation, the elevator includes an electromagnet. Mounting the build platform on the elevator includes energizing at least one electromagnet. The electromagnet further ensures that the system can overcome the flow resistance and pressure of the photocurable resin on the build plate. The electromagnets can include three electromagnets arranged around the pin to define an equilateral triangle around the pin.

[0024] In yet another implementation, the method includes operating an imaging module to selectively cure a layer of photocurable resin at the build plane.

[0025] In a further implementation, the build platform includes a support plate coupled to and above the build plate, and a plurality of vertical rods couple the support plate to the build plate, and mounting the build platform on the elevator includes mounting the support plate on the elevator. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is an isometric view of one embodiment of a three-dimensional (3D) printing system. [Figure 2] FIG. 1 is an isometric view of one embodiment of a 3D print engine. [Figure 3] Isometric view of part of the 3D printing engine in Figure 2 [Figure 4] Isometric view of the portion of the 3D printed engine from Figure 2 highlighting the rigid base that supports the imaging module. [Figure 5] Isometric view of the portion of the 3D printed engine from Figure 2 highlighting the rigid base that supports the imaging module. [Figure 6] An isometric view of a portion of the 3D printed engine from Figure 2 highlighting the elevator's lower support. [Figure 7] An isometric view of the portion of the 3D printed engine from Figure 2 highlighting the elevator upper support. [Figure 8] Isometric view of a portion of the 3D print engine from Figure 2 highlighting the elevator and electromagnets used to secure the build platform. [Figure 9] Isometric view similar to Figure 8 except that the cover is placed over the electromagnet [Figure 10] Isometric view of a portion of an elevator with a portion of the upper support visible through it to allow visibility of the lower portion. [Figure 11] FIG. 1 is an isometric cross-sectional view of an elevator supporting the support plate of a build platform. [Figure 12] 1 is a simplified electrical block diagram of one embodiment of a 3D printing system. [Figure 13] FIG. 1 illustrates one embodiment of a "high level method" for manufacturing a 3D article. [Figure 14] A graph showing the correlation between distance sensor readings (representing the height of a point on the elevator or build platform) and force sensor or load cell readings (representing the force being sensed at the elevator). [Figure 15] 14 is a flow chart illustrating a calibration method that is part of the method of FIG. 13. [Figure 16] 14 is a flowchart illustrating a manufacturing method that is part of the method of FIG. 13. DETAILED DESCRIPTION OF THE INVENTION

[0027] FIG. 1 is an isometric view illustrating one embodiment of a three-dimensional (3D) printing system 2. Mutually perpendicular axes X, Y, and Z are used to describe the 3D printing system 2. Axes X and Y are generally horizontal transverse axes. Axis Z is a vertical axis generally aligned with a gravity reference. The use of the term "generally" indicates limitations that are "generally" true by design, within manufacturing tolerances. Additionally, angular axes θ-X, θ-Y, and θ-Z are rotations about the X, Y, and Z axes, respectively. The 3D printing system 2 includes an outer housing 4 that houses an internal chamber 6 that houses a print engine 8. A door 5 is provided on the housing 4 to allow access to an enclosed portion of the internal chamber 6.

[0028] 2-5 are isometric views providing further details of print engine 8. Referring to FIG. 2, print engine 8 includes a rigid base 10 and a vertical beam 12 extending upwardly from rigid base 10. An elevator 14 is slidably coupled to vertical beam 12 and configured for vertical translation along vertical beam 12. A vertical translation mechanism 16 (not shown in detail here) is coupled to vertical beam 12 and elevator 14 and configured to controllably, selectively, vertically, and precisely translate and position elevator 14 along vertical beam 12.

[0029] One embodiment of the vertical translation mechanism 16 includes a motorized ball-bearing screw mechanism, or what is otherwise known as a ball-screw mechanism. The ball-screw mechanism includes a vertical screw shaft that passes through a ball nut. The ball nut contains recirculating steel balls and translates vertically. The vertical screw shaft has a helical channel that engages the recirculating balls. The elevator 14 includes the ball nut. A motor is coupled to the vertical screw shaft and configured to selectively rotate the vertical screw shaft. As the vertical screw shaft rotates, the action of the vertical screw shaft against the ball nut translates the elevator up or down depending on the direction of rotation. Such translation mechanisms are known in the art for precise positioning along vertical, horizontal, and diagonal axes. Other embodiments are possible, such as 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 translating components along various axes.

[0030] The elevator 14 is slidably coupled to the vertical beam 12 by linear bearings. The linear bearings have a combination of race and ball bearings for low friction and linear motion. Other bearing designs are possible, and linear bearings are known in the art for precise linear motion constraints.

[0031] The print engine 8 includes a build vessel 18 containing a photocurable resin 20. The build vessel 18 includes an upper ring 22 connected to a lower ring 24 by vertical rods 26. The photocurable resin 20 is contained within the build vessel 18 by an outer cylindrical vertical wall 28 and a lower circular transparent sheet 30 supported by a circular glass plate 32. At least one gas port 34 allows oxygen-containing or atmospheric gas to enter or exit the space between the transparent sheet 30 and the circular glass plate 32.

[0032] Print engine 8 also includes a build platform 36 that is supported by elevator 14. Referring to FIG. 3 , build platform 36 includes a build plate 38 that is coupled to a support plate 40 via a plurality of vertical rods 42. Support plate 40 has a lower surface 41. Build plate 38 has a lower surface 44 for supporting a 3D article (not shown) being manufactured by 3D printing system 2. Elevator 14 includes a lower support 46 that supports an upper support 48. Support plate 40 is supported on elevator upper support 48.

[0033] 4 and 5 are isometric views showing details around the rigid base 10 of system 2. The rigid base 10 includes a granite plate 50 that provides stable support for the mechanical and optical components of the print engine 8. The granite plate 50 supports three base actuators 51 configured to engage the underside of the build vessel's lower ring 24 (FIG. 2) when the build vessel is mounted on the rigid base 10. An imaging module 52 is also coupled to the granite plate 50.

[0034] The imaging module 52 is configured to translate along both lateral axes X and Y. Translation along the two axes is provided by a two-dimensional (2D) translation mechanism 54. In one embodiment, the translation mechanism 54 includes two translation mechanisms 54X, 54Y, which may be similar to the vertical translation mechanism 16 described with respect to FIG. 2. In the illustrated embodiment, the translation mechanism 54 includes a linear motor driving a screw or gear mechanism. The translation mechanisms 54X, 54Y are configured to selectively position and translate the imaging module 52 along the lateral X and Y axes, respectively. Other precision translation mechanisms 54 are possible and are known in the art for precision mechanisms used for 3D printing, 2D printing, and imaging circuit photolithography.

[0035] In the illustrated embodiment, imaging module 52 includes three light engines 56. Light engines 56 are projection-based light engines known in the art for photopolymer stereolithography. Such light engines include a light source, a spatial light modulator, projection optics, and other optical components (such as bending lenses or mirrors, converging and diverging lenses or mirrors, to name a few).

[0036] Disposed alternately between the light engines are two confocal distance sensors 58. The confocal distance sensors are non-contact distance sensors configured to sense the distance and / or height of the surface of the build plate 38, transparency sheet 30, and / or glass plate 32. The confocal distance sensors 58 can be configured to utilize monochromatic or polychromatic light and are known in the art for high precision distance measurements.

[0037] Other known distance sensors 58 can also be used. Alternatively, the distance sensor can be laser-based. Some direct a beam at a small oblique angle to the surface normal and receive the beam at a line of the sensor. The principle of triangulation is used to determine distance. Highly accurate sensors utilize the principle of interferometry. Such sensors are known in the art and are widely available.

[0038] FIG. 6 is an isometric view of the lower support 46 of the elevator 14. The lower support 46 includes a proximal portion 60 slidably coupled to the vertical support 12. The proximal portion 60 has a major axis along a second horizontal axis Y and has two elevator actuators 62 located at opposite ends of the proximal portion 60 relative to Y. The two elevator actuators 62 are disposed laterally on either side of the vertical support 12 relative to the second horizontal axis Y and individually extend upward from an upper surface 64 of the proximal portion 60. The elevator actuators 62 are spaced apart relative to the second horizontal axis Y. The elevator actuators 62 each have a spherical tip at their upper end.

[0039] The elevator actuators 62 are configured to selectively raise and lower vertically along a vertical axis Z. In one embodiment, the elevator actuators 62 may be individually coupled to motorized lead screws. The lead screws thread into motorized nuts. When a motor rotates the nut, it has the effect of selectively raising and lowering the elevator actuators 62. Vertical actuators such as the illustrated elevator actuator 62 are known in the art for extremely precise vertical movement. Lead screw implementations typically have very fine threads.

[0040] The lower support 46 includes a distal portion 66 that extends along a first transverse axis X from a proximal portion 60 to a distal end 68. A pin 70 extends upwardly from the distal end 68. The pin 70 has a rounded or spherical tip at its upper end.

[0041] FIG. 7 is an isometric view of the lower portion 72 of the upper support 48 of the elevator 14. The lower portion 72 has three datums 74, including a flat datum 74F, a V-shaped datum 74V, and a conical datum 74C. The V-shaped datum 74V defines a V-recess geometry. The conical datum 74C defines a conical recess. When the upper support 48 is mounted on the lower support 46, the lower portion 72 faces the lower support 46. The spherical tips of the pairs of actuators 62 individually engage with the two datums 74, including the flat datum 74F and the V-shaped datum 74V. The spherical tip of the pin 70 engages with the conical datum 74C.

[0042] FIG. 8 is an isometric view of an elevator 14 slidably coupled to a vertical support 12 including an upper support 48 supported by a lower support 46. An upper portion 76 of the upper support 48 includes a plurality of three electromagnets 78 extending upwardly from the upper portion 76. FIG. 9 is similar to FIG. 8 except that a cover 80 is disposed over a portion of the upper surface 76 and the three electromagnets 78. The cover 80 is formed from a ferromagnetic material. The cover 80 has an upper surface 82 that forms a portion of the upper surface of the upper support 48 when the cover 80 is disposed over the electromagnets 78. When the build platform 36 is mounted on the elevator 14, the lower surface 41 of the support plate 40 rests on the upper surface 82.

[0043] Figure 10 is an isometric view. Compared to Figure 9, the orientation has changed and portions of the upper support 48 are shown "ghosted," with sufficient transparency to allow for viewing of the interior or underlying components. The pin 70 and conical datum 74C are located at the center of an equilateral triangle defined by the center of the (circular) electromagnet 78. By coupling the upper support 48 to the lower support 46, the electromagnet 78 and force sensor 86 (described below) of the upper support 48 are electrically coupled to the print engine 8 (Figures 1 and 2). The electromagnet 78 and force sensor 86 are components of the lower support 46.

[0044] The upper support 48 is also mechanically coupled to the lower support 46 by a combination of springs and shoulder bolts (not shown) located near the two actuators 62 and the spherical pin 70. The springs and shoulder bolts spring-load datums 74 onto the actuators 62 and the spherical tips of the pins 70.

[0045] 11 is a cross-sectional isometric view showing details of a portion of the build platform 36 mounted on the elevator 14. The support plate 40 of the build platform 36 is mounted on an upper surface 82 of the upper support 48. The support plate 40 includes an internal magnetic or ferromagnetic plate 84 that covers the three electromagnets 78 when the support plate 40 is mounted on the upper support 48 of the elevator 14.

[0046] The lower support 46 includes a load cell 86 below the pin 70. The pin 70 is centered within and threaded into the load cell 86. The load cell 86 is a force sensor that outputs a voltage indicative of the normal force applied to the pin 70 by the conical datum 74C. The linear factor driving the normal force on the force sensor 86 is the force on the build plate 38 transmitted to the support plate 40 by the vertical rod 42. Thus, the force sensor 86 outputs a varying signal that is modulated by variations in the force on the build plate 38.

[0047] 12 is a simplified electrical block diagram of 3D printing system 2 including print engine 8. FIG. 12 is simplified in the sense that certain features of print engine 8 may be omitted for simplicity. Controller 88 is electrically and controllably coupled to components of elevator 14, vertical movement mechanism 16, base actuator 51, imaging module 52, and membrane pressurization system 90.

[0048] Controller 88 includes a processor 92 coupled to an information storage subsystem 94 that includes non-transitory or non-volatile information storage. Information storage 94 stores software instructions that, when executed by processor 92, operate portions of print engine 8, including the various systems and subsystems shown in FIG. 12. Controller 88 may be a single module co-located with print engine 8 and / or may include modules, computers, and / or servers that are separate or remote from print engine 8. Controllers including processors and storage subsystems are known in the art for controlling electromechanical systems.

[0049] 13 is a "high level method" 98 for manufacturing a 3D article using the 3D printing system 2. The method or major steps 100, 200, and 300 can be performed simultaneously before and during the manufacture of the 3D article. Alternatively, these methods may be performed at separate times, but each and in combination are part of an overall method 98 for manufacturing a 3D article. Some or all of the method 98 can be performed by the controller 88. Some manufacturing methods may be manual.

[0050] According to 100, the confocal sensor 58 is used to measure the displacement of a point (or line or area) on the build platform 36 relative to the load cell readings. One way to do this is to mount the platform 36 on the elevator 14 and then operate the vertical movement mechanism 16 to position the lower surface 44 of the build plate within the measurable range of the confocal sensor 58. At that point, the height (from the confocal sensor 58) and voltage readings 86 of the lower surface 44 are obtained and plotted on a graph. This is repeated after various normal forces are applied to the lower surface 44. An exemplary graph of the results is shown in FIG. 14. From this graph, the displacement height of the lower surface 44 from an unstressed state can be inferred from the load cell readings.

[0051] According to 200, the confocal sensor 58 and the actuators 51 and 62 are used to level the underside 44 of the build vessel 18 and the build plate 38, respectively. Leveling of the build vessel 18 can occur before or after leveling of the build plate 38.

[0052] According to 300, the 3D article is fabricated. During fabrication, the voltage from the load cell 86 is monitored, analyzed, and utilized to adjust the position of the lower surface 44 using the elevator actuator 62. The position adjustments can include vertical translation and / or rotational adjustments.

[0053] 15 is a flowchart illustrating one embodiment of method 200 in greater detail. According to 202, build platform 36 is loaded onto elevator 14 by resting lower surface 41 of support plate 40 on upper surface 82 of elevator 14. As part of loading platform 36, electromagnet 78 may be energized to magnetically secure support plate 40 to upper support 48.

[0054] According to 204, the vertical movement mechanism 16 is operated to move the lower surface 44 of the build plate 38 to a "build plane" position. In the build plane position, the lower surface 44 is essentially at the focal length of the light engine 56 and within the measurement range of the confocal length sensor 58.

[0055] According to 206, the confocal sensor 58 and elevator actuator are operated to level the lower surface 44. More specifically, 206 includes the following "minor" steps: (1) operating the lateral movement mechanism 54 to scan the imaging module 52 along the lower surface 44 using the confocal sensor 58; (2) concurrently with the scan (1), operating the confocal sensor 58 to output a signal indicating the vertical height of a point on the surface 44; (3) based on this signal, the tilt and height error of the surface 44 are calculated; (4) the elevator actuator is then operated to level the surface 44 to coincide with the build plane defined by the lateral XY motion of the lateral movement mechanism 54. Steps (1)-(4) can be repeated as necessary until the surface 44 is parallel to the lateral XY motion of the lateral movement mechanism 54, which is generally horizontal.

[0056] With respect to minor step (4) of step 206 above, the actuators can be operated to adjust the tilt or orientation of the lower surface 44 relative to the lateral X- or Y-axis. Referring to FIG. 6 , note that a vertically moving actuator 62 has the effect of rotating the upper support 48 about the pin 70. When both actuators 62 are raised or lowered simultaneously, the rotation is in θ-Y about the lateral Y-axis. When two actuators 62 are moved in opposite directions (one actuator is raised and the other is lowered by the same amount), the effect is a rotation in θ-X about the lateral X-axis. In this way, any tilt of the lower surface 44 relative to the horizontal plane (or the plane of the lateral X-Y motion of the lateral movement mechanism 54) can be offset by rotation along both lateral axes.

[0057] According to step 208, the platform 36 is removed from the elevator 14. According to step 210, the build vessel 18 is mounted on the rigid base 10 and filled with the photocurable resin 20. Once the build vessel 18 is mounted on the rigid base 10, the lower ring 24 is positioned on and engaged with the base actuator 51. At this time, the top surface of the glass plate 32 is within the measurement range of the confocal distance sensor 58. The top surface of the glass plate 32 is the reference surface on which the transparent sheet 30 is placed.

[0058] According to 212, the confocal sensor 58 and the base actuators are operated to level the glass plate 32 in a manner similar to that of step 206. Thus, step 212 has a similar set of four minor steps (1) to (4) relative to the top surface of the glass plate 32. In step (4), the three base actuators 51 are operated to move the top surface of the glass plate 32 to the appropriate height and level the glass plate 32.

[0059] According to 214, the build platform 36 is loaded onto the elevator 14 in a manner similar to step 202. At this point, the print engine 8 is ready to proceed to method 300. In various embodiments, the order of the steps and minor steps of method 200 can be changed.

[0060] 16 is a flowchart illustrating a method 300 for manufacturing a 3D article. According to 302, print engine 8 is calibrated and initialized using procedures similar to methods 100 and 200. From the calibration of method 100, controller 88 stores information correlating readings from load cell 86 with variations in height and / or angular tilt of surface 44. An example of that correlation information is shown in FIG. 14.

[0061] According to 304, vertical movement mechanism 16 is operated to translate lower surface 44 of build plate 38 through photocurable resin 20 to a build plane above transparent sheet 30. According to 306, controller 88 receives a signal from load cell 86 indicative of a viscous drag force on lower surface 44, which tends to mechanically bend or deflect lower surface 44 out of plane with the build plane.

[0062] According to 308, the controller 88 calculates the displacement of the lower surface 44 based on the signal from the load cell 86 and the stored correlation information. As the lower surface 44 is lowered into the resin, the drag force may apply an upward force to the lower surface 44, which may apply a torque to the elevator along θ-Y about the horizontal axis Y. As a result, the lower surface 44 may not approach the build plane as desired after step 304. Also, the lower surface 44 (or the lower surface of the 3D article) may have an increasing slope along the axis X.

[0063] According to 310, elevator actuators 62 are adjusted to offset the height error and / or deflection tilt angle error. If the viscous drag is upward, an upward force and / or torque is applied about lateral axis Y, and the adjustment is to raise both actuators 62 to adjust the vertical height of surface 44 and / or level it. Adjusting actuators 62 can be an iterative process: (a) during step 310, the actuators are adjusted to correct a portion of the error calculated in step 308, (b) steps 306 and 308 are repeated, and (c) step 310 is repeated. This procedure repeats steps 306-310 until it is determined in step 308 that the error has been corrected, at which point the process proceeds to step 312.

[0064] According to 312, the light engine is operated to selectively cure a layer of light-curable resin 20 at the build plane and on the front surface 44 or underside of the 3D article. Method 300 then returns to 304. Steps 304-312 can be repeated until the fabrication of the 3D article is complete. Steps 306-310 can be repeated as necessary to ensure that surface 44 remains level.

[0065] The particular embodiments and applications described above are intended to be illustrative only and do not exclude modifications and variations encompassed by the appended claims.

Claims

1. 1. A method for manufacturing a three-dimensional (3D) article, comprising: providing a 3D printing system; mounting the build platform on the elevator; operating a vertical movement mechanism to lower the lower surface of the build platform into a measurement range of a distance sensor; scanning the imaging module along at least one horizontal axis; Concurrently with scanning the distance sensor, receiving signals from the distance sensor indicative of a plurality of vertical positions along a lateral axis of the underside of the build platform; calculating the slope of the underside of the build platform based on signals from the distance sensor; and operating the elevator actuator to level the underside of the build platform. Including, The 3D printing system includes: an elevator configured for translation along a vertical axis and including an elevator actuator; a vertical movement mechanism coupled to the elevator; a build platform including a build plate having a lower surface; and An imaging module further including: a light engine configured to project pixelated light upward; and Distance Sensor A method comprising:

2. The elevator is a lower support further including an elevator actuator extending upward from an upper portion of the lower support; and an upper support having a lower portion including a reference surface that engages the elevator actuator; Equipped with The method includes operating the actuator to adjust the orientation of the upper support relative to the lower support and relative to a horizontal axis.

2. The method of claim 1.

3. 3. The method of claim 2, wherein the elevator actuator includes two elevator actuators, the lower support includes a pin extending upward from an upper portion of the lower support, the two elevator actuators and the pin engage three reference surfaces on a lower portion of the upper support, and the step of operating the two elevator actuators adjusts the orientation of the upper support along two orthogonal horizontal axes.

4. 10. The method of claim 1, wherein the build platform comprises a support plate coupled above a build plate, and the step of mounting the build plate comprises mounting the support plate on the elevator.

5. 5. The method of claim 4, wherein a plurality of vertical rods connect the lower surface of the support plate to the upper surface of the build plate, and wherein mounting the build platform on the elevator includes mounting the lower surface of the support plate on the upper surface of the elevator.

6. 5. The method of claim 4, wherein the elevator includes at least one electromagnet, and the step of mounting the platform includes energizing the at least one electromagnet to magnetically hold the support plate to the elevator.

7. 10. The method of claim 1, further comprising scanning and operating the light engine to image a layer of photocurable resin.

8. 10. The method of claim 1, wherein the imaging module includes a plurality of light engines, the method including scanning and operating the plurality of light engines to image the layer of photocurable resin.

9. 2. The method of claim 1, wherein the distance sensor is a confocal sensor, the method including receiving a signal from the confocal sensor.

10. The 3D printing system includes a rigid base, a vertical beam extending upward from the rigid base, and a plurality of actuators extending upward from the rigid base, and the method further includes: mounting a build vessel on the rigid base and engaging the plurality of actuators; scanning the imaging module along at least one horizontal axis along an upper surface of a transparent plate at a lower end of the build vessel; Concurrently with scanning the imaging module, receiving signals from the distance sensor indicative of a plurality of vertical positions along a transverse axis of the lower surface of the build vessel; and adjusting the height of the upper surface of the transparent plate of the modeling container by operating the plurality of actuators; 2. The method of claim 1, comprising:

11. 1. A method for manufacturing a three-dimensional (3D) article, comprising: providing a 3D printing system; mounting a support plate on an upper surface of the elevator upper support; operating a vertical movement mechanism to lower the lower surface of the build plate adjacent to a distance sensor; scanning the imaging module along at least one horizontal axis; Concurrently with scanning the distance sensor, receiving signals from the distance sensor indicative of a plurality of vertical positions along a lateral axis of the underside of the build platform; calculating the slope of the underside of the build platform based on signals from the distance sensor; and operating the elevator actuator to level the underside of the build platform. Including, The 3D printing system includes: Rigid base; a support beam extending upwardly from said rigid base; an elevator configured for vertical translation along the support beam, further comprising: a lower support slidably coupled to the support beam and having an upper surface including an upwardly extending elevator actuator; and an upper support having a lower surface including a reference surface engaged with the actuator; a vertical movement mechanism coupled to the elevator; a build platform including a support plate and coupled to a build plate having a lower surface; An imaging module further including: a light engine configured to project pixelated light upward; and Distance Sensor A method comprising:

12. 12. The method of claim 11, wherein the lower support includes a proximal portion slidably coupled to the support beam and a distal portion extending along a first horizontal axis X, the elevator actuator includes two elevator actuators located on the proximal portion of the lower support and a pin extending upward from the distal portion of the support, the upper support includes a reference surface that engages the two elevator actuators and the pin, and operating the elevator actuators includes operating the two elevator actuators to swing the upper support relative to the pin.

13. 12. The method of claim 11, wherein the upper support includes at least one electromagnet, and wherein mounting the support plate includes energizing the at least one electromagnet to magnetically hold the support plate to the elevator.

14. 12. The method of claim 11, including scanning and operating the light engine to image a layer of photocurable resin.

15. The 3D printing system includes a plurality of actuators extending upward from the rigid base, and the method further comprises: mounting a build vessel on the rigid base and engaging the plurality of actuators; scanning the imaging module along at least one horizontal axis along a surface of a transparent plate at a lower end of the build vessel; Concurrently with scanning the imaging module, receiving signals from the distance sensor indicative of a plurality of vertical positions along a transverse axis of a surface of the transparent plate of the build vessel; calculating the inclination of the surface of the transparent plate of the build vessel based on the signal from the distance sensor; and adjusting the height of the modeling container by operating the plurality of actuators; 2. The method of claim 1, comprising:

16. 1. A method for manufacturing a three-dimensional (3D) article, comprising: providing a 3D printing system; mounting the build platform on the elevator; operating a vertical movement mechanism to lower the lower surface of the build platform to a position adjacent to a distance sensor; scanning the imaging module along at least one horizontal axis; Concurrently with scanning the distance sensor, receiving signals from the distance sensor indicative of a plurality of vertical positions along a transverse axis of the lower surface of the build plate; calculating the slope of the lower surface of the build plate based on signals from the distance sensor; operating the elevator actuator to level the underside of the build platform; mounting the shaped container on a rigid base; scanning the imaging module along at least one horizontal axis; receiving signals from the distance sensor indicative of a plurality of vertical positions along a transverse axis of a surface of the transparent plate of the build vessel simultaneously with scanning the distance sensor; and activating the plurality of elevator actuators to adjust the height and orientation of the surface of the transparent plate of the build vessel; Including, The 3D printing system includes: a rigid base having a plurality of base actuators; an elevator configured for translation along a vertical axis and including an elevator actuator; a vertical movement mechanism coupled to the elevator; a build platform including a build plate having a lower surface; and An imaging module further including: a light engine configured to project pixelated light upward; and Distance Sensor A build vessel having a bottom end with a transparent plate A method comprising:

17. 17. The method of claim 16, wherein the surface of the transparent plate is the top surface of the transparent plate.

18. 17. The method of claim 16, including scanning and operating the light engine to image a layer of photocurable resin.

19. 17. The method of claim 16, wherein the lower surface of the build plate is leveled before adjusting the height of the surface of the transparent plate of the build vessel.

20. 20. The method of claim 19, wherein the build platform is removed from the elevator before the height of the surface of the transparent plate of the build vessel is adjusted.

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