WO2023275615A1

WO2023275615A1 - Additive manufacturing devices having curved print interfaces and corresponding methods

Info

Publication number: WO2023275615A1
Application number: PCT/IB2022/000371
Authority: WO
Inventors: Hubertus Theodorus PETRUS VAN ESBROECK; Dheepan IYYAMPILLAI; Ahmed S. YUSUF
Original assignee: Structo North America Inc
Priority date: 2021-06-28
Filing date: 2022-06-27
Publication date: 2023-01-05

Abstract

An additive manufacturing device (100) comprises a vessel (105) for containing a material (110) that is polymerizable on exposure to radiation at one or more wavelengths. The vessel (105) has a lower wall (115) that is curved, and at least partially transparent to the radiation at the one or more wavelengths, and comprises a print surface (120). The device (100) further comprises a build platform (130), having a build surface (135), configured for movement such that a layer of material is defined between the build surface (135) and the print surface (130). Furthermore, the device (100) comprises an irradiation unit (140) configured to generate radiation having a pattern to polymerize the material (110). The vessel (105) is configured to move for the print surface (130) to roll with respect to a reference plane parallel to the build surface (135), and the irradiation unit (140) is configured to be positioned to irradiate a layer of material adjacent to the print surface (130). Also provided is a corresponding additive manufacturing method (1000).

Description

ADDITIVE MANUFACTURING DEVICES HAVING CURVED PRINT INTERFACES AND CORRESPONDING METHODS

FIELD

[0001] The present specification relates to additive manufacturing methods and systems and, in particular, to an additive manufacturing device having a curved print surface, and a corresponding additive manufacturing method.

BACKGROUND

[0002] Additive manufacturing is the process of forming three dimensional objects by adding material, effectively building up an object, as opposed to traditional subtractive methods such as carving or computer numerical control (CNC) machining, in which a three dimensional object is formed by removing material from a larger piece. Generally, in most apparatuses and methods for additive manufacturing, the three-dimensional object is built up layer by layer in a vertical direction. The desired three-dimensional object is formed out of a stack of very thin layers of material, each such layer being the representation of the object’s cross-section at the vertical position of that layer within the object

SUMMARY

[0003] According to an implementation of the present specification there is provided an additive manufacturing device. The additive manufacturing device comprises a vessel for containing a material that is polymerizable on exposure to radiation at one or more wavelengths, the vessel having a lower wall at a bottom of the vessel, the lower wall being curved, and at least partially transparent to the radiation at the one or more wavelengths, and the lower wall comprising a print surface; a build platform having a build surface, the build platform being configured for movement relative to the vessel such that a layer of material is defined between the build surface and the print surface; and an irradiation unit, disposed underneath the bottom of the vessel, the irradiation unit being configured to generate radiation at the one or more wavelengths, the radiation having a pattern to polymerize the material contained within the vessel, wherein the vessel is configured to move for the print surface to roll with respect to a reference plane parallel to the build surface, wherein the irradiation unit is configured to be positioned to irradiate a layer of material that is adjacent to the print surface, and wherein the curvature of the lower wall is oriented away from the irradiation unit. [0004] The irradiation unit may comprise a laser diode.

[0005] The additive manufacturing device may further comprise a controller, wherein the laser diode may be operable to be pulsed on/off via a signal from the controller.

[0006] The irradiation unit may further comprise a rotating polygonal reflector.

[0007] The irradiation unit may further comprise a laser galvanometer.

[0008] The additive manufacturing device may further comprise a controller, wherein the irradiation unit comprises a first sensor and a second sensor, and wherein a speed of rotation of the rotating polygon reflector is measured by the first sensor and fed back to the controller, and wherein a position of the rotating polygon reflector is measured by the second sensor and fed back to the controller.

[0009] The irradiation unit may further comprise an optical assembly.

[0010] The optical assembly may comprise at least an f-theta lens.

[0011] The additive manufacturing device may further comprise a controller, wherein the irradiation unit may further comprise a light intensity measurement sensor upon which a laser beam emitted from the laser diode is directed, and a measured intensity of the laser beam is fed back to the controller.

[0012] The irradiation unit may comprise a linear array of individually addressable light emitting diodes (LEDs).

[0013] The LEDs may comprise micro LEDs.

[0014] The irradiation unit may further comprise a gradient-index (GRIN) lens array.

[0015] The irradiation unit may comprise a linear array of light emitting diode (LED) modules. [0016] Each LED module may comprise an LED, and a lens configured to focus the light emitted by the LED to a demagnified image of the LED.

[0017] The irradiation unit may further comprise an actuator that is configured to oscillate the linear array of LEDs.

[0018] An amplitude of the oscillatory motion may be equal to or greater than a distance between the LED modules.

[0019] The additive manufacturing device may further comprise a first actuator operatively coupled to the vessel and configured to rotate the vessel about a pivot axis; and a second actuator configured to linearly displace a position of the pivot axis, wherein the first actuator and the second actuator are configured to jointly enable the print surface to roll with respect to the reference plane parallel to the build surface.

[0020] The irradiation unit may be operatively coupled to the second actuator for the second actuator to linearly displace the irradiation unit

[0021] The additive manufacturing device may further comprise a controller, wherein the first actuator comprises a rotary encoder that is configured to feedback an angular position of the vessel to the controller.

[0022] The additive manufacturing device may further comprise a third actuator configured to linearly displace the irradiation unit

[0023] The additive manufacturing device may further comprise a controller, wherein the second actuator comprises a linear encoder that is configured to feedback a linear position of the pivot axis to the controller.

[0024] The second actuator may be configured to linearly displace the irradiation unit back and forth between a first linear position and a second linear position, the first linear position and the second linear position having at least one intermediate linear position in-between, wherein at each position, the radiation generated by the irradiation unit irradiates a section of the layer of material adjacent to the print surface, the section corresponding to the position of the irradiation unit The first actuator and the second actuator may be configured to jointly move the vessel for the print surface to roll back and forth between a first angular position and a second angular position, the first angular position and the second angular position having at least one intermediate angular position in-between, wherein each angular position of the print surface corresponds to the corresponding linear position of the irradiation unit After the irradiation unit is displaced from the first linear position to the second linear position, or from the second linear position to the first linear position, the build platform may be configured to be moved away from the print surface by a distance that defines a new layer of material between a bottom surface of the last polymerized layer and the print surface.

[0025] The first actuator and the second actuator may be configured to jointly move the vessel for the highest point of the print surface to intersect with the radiation generated by the irradiation unit

[0026] The print surface may be in direct contact with the material contained in the vessel.

[0027] The additive manufacturing device may further comprise at least one actuation module operatively coupled to the vessel and configured to enable the print surface to roll with respect to the reference plane parallel to the build surface; and a mechanism that prevents the print surface from slipping with respect to the reference plane.

[0028] The mechanism may comprise one of: a toothed rack and a pinion gear, and a mechanical bar linkage.

[0029] According to another implementation of the present specification there is provided an additive manufacturing method, comprising: providing a vessel having a lower wall at a bottom of the vessel, the lower wall being curved, and at least partially transparent to radiation at one or more wavelengths, the lower wall comprising a print surface; at least partially filling the vessel with a material which is polymerisable on exposure to the radiation at the one or more wavelengths; providing an irradiation unit that is configured to generate radiation at the one or more wavelengths, the radiation having a pattern to polymerize the material contained within the vessel, wherein providing the irradiation unit comprises disposing the irradiation unit underneath the bottom of the vessel; positioning a build platform having a build surface relative to the vessel such that a layer of material is defined between the build surface and the print surface; and irradiating, with the radiation from the irradiation unit, the layer of material to polymerize the layer of material, wherein irradiating the layer of material comprises positioning the vessel and the irradiation unit for the irradiation unit to irradiate the layer of material that is adjacent to the print surface, wherein positioning the vessel comprises enabling the vessel to move for the print surface to roll with respect to a reference plane parallel to the build surface, and wherein providing the vessel comprises orienting the curvature of the lower wall away from the irradiation unit

[0030] Providing the irradiation unit may comprise providing an irradiation unit comprising a laser diode.

[0031] The additive manufacturing method may further comprise pulsing on/off the laser diode via a signal from a controller.

[0032] The irradiation unit may further comprise a rotating polygonal reflector.

[0033] The irradiation unit may further comprise a laser galvanometer.

[0034] The additive manufacturing method may further comprise: measuring a speed of rotation of the rotating polygon reflector; measuring a position of the rotating polygon reflector; and providing a signal indicative of the measured speed and position to a controller.

[0035] The irradiation unit may further comprise an optical assembly.

[0036] The optical assembly may comprise at least an f-theta lens.

[0037] The additive manufacturing method may further comprise: measuring an intensity of a laser beam directed from the laser diode; and providing a signal indicative of the measured intensity to a controller. [0038] Providing the irradiation unit may comprise providing an irradiation unit that comprises a linear array of individually addressable light emitting diodes (LEDs).

[0039] The LEDs may comprise micro LEDs.

[0040] The irradiation unit may further comprise a gradient-index (GRIN) lens array.

[0041] Providing the irradiation unit may comprise providing an irradiation unit that comprises a linear array of light emitting diode (LED) modules.

[0042] Each LED module may comprise an LED, and a lens configured to focus the light emitted by the LED to a demagnified image of the LED.

[0043] The additive manufacturing method may further comprise oscillating, by an actuator, the linear array of LEDs.

[0044] An amplitude of the oscillatory motion may be equal to or greater than a distance between the LED modules.

[0045] Positioning the vessel may comprise: rotating, by a first actuator, the vessel about a pivot axis; and linearly displacing, by a second actuator, a position of the pivot axis, wherein the rotation of the vessel, and the linear displacement of the pivot axis enable the print surface to roll with respect to the reference plane parallel to the build surface.

[0046] The irradiation unit may be operatively coupled to the second actuator, and positioning the irradiation unit may comprise linearly displacing, by the second actuator, the irradiation unit.

[0047] Positioning the irradiation unit may comprise linearly displacing, by a third actuator, the irradiation unit.

[0048] The additive manufacturing method may further comprise providing, by a rotatory encoder of the first actuator, a signal indicative of an angular position of the vessel to a controller. [0049] The additive manufacturing method may further comprise providing, by a linear encoder of the second actuator, a signal indicative of a linear position of the pivot axis to a controller.

[0050] Irradiating the layer of material may comprise: (i) linearly displacing the irradiation unit from a first linear position to a second linear position, the irradiation unit having at least one intermediate linear position between the first linear position and the second linear position, wherein at each position: generating radiation by the irradiation unit, which irradiates a section of the layer of material adjacent to the print surface, the section corresponding to the position of the irradiation unit; (ii) moving the vessel for the print surface to roll from a first angular position to a second angular position, the print surface having at least one intermediate angular position between the first angular position and the second angular position, wherein each angular position of the print surface corresponds to the corresponding linear position of the irradiation unit; (iii) after the irradiation unit is at the second linear position, moving the build platform away from the print surface by a distance that defines a new layer of material between a bottom surface of the last polymerized layer and the print surface; (iv) irradiating the new layer of material, defined by the movement of the build platform, by: linearly displacing the irradiation unit from the second linear position to the first linear position and by moving the vessel for the print surface to roll from the second angular position to the first angular position; and (v) after the irradiation unit is at the first linear position, moving the build platform away from the print surface by the distance; and (vi) repeating (i)-(v) until an object is printed.

[0051] Moving the vessel may comprise moving the vessel for the highest point of the print surface to intersect with the radiation generated by the irradiation unit

[0052] The print surface may be in direct contact with the material contained in the vessel.

[0053] Positioning the vessel may comprise: enabling moving of the vessel, by employing at least one actuation module, for the print surface to roll with respect to the reference plane parallel to the build surface; and employing a mechanism that prevents slipping of the print surface with respect to the reference plane. [0054] The mechanism may comprise one of: a toothed rack and a pinion gear, and mechanical bar linkage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] It will be convenient to further describe the present disclosure with respect to the accompanying drawings that illustrate possible arrangements of the disclosure. Other arrangements of the disclosure are possible and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the disclosure.

[0056] Also, in the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not necessarily drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the shapes of the elements as drawn are not necessarily intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.

[0057] FIG. 1 shows an isometric view of a cross-section of an example additive manufacturing device according to some implementations of the present specification;

[0058] FIGs. 2A and 2B show isometric views of a portion of the example additive manufacturing device of FIG. 1;

[0059] FIG. 3 shows a schematic view of the example additive manufacturing device of FIG. 1;

[0060] FIG. 4 shows another schematic view of the example additive manufacturing device of FIG. 1;

[0061] FIG. 5 shows displacement of a vessel and an irradiation unit of the example additive manufacturing device of FIG. 1;

[0062] FIGS. 6A and 6B show different example rolling enabling mechanisms according to some implementations of the present specification; [0063] FIGs. 7A, 7B, 8, and 9 show different example irradiation units according to some implementations of the present specification;

[0064] FIG. 10 shows a flow diagram of an example additive manufacturing method according to some implementations of the present specification; and

[0065] FIG. 11 shows a process of irradiation of layers of material to print an object by an additive manufacturing device according to some implementations of the present specification.

DETAILED DESCRIPTION

[0066] Existing additive manufacturing systems suffer from various drawbacks such as, but not limited to, slow printing rates, low print resolution, inefficiency, a requirement for consumable parts such as separation films, coatings, or vessels etc. For example, many stereolithography (SLA) based additive manufacturing devices have slow printing rates. Digital Light Processing (DLP) based additive manufacturing devices are faster than the SLA based devices, however they are not as scalable, because the projected size of each pixel gets too large in these devices when a large printable object area is desired, thus resulting in low resolution when projected over a larger print area. Some additive manufacturing devices enable rapid printing and scalability using Liquid Crystal Display (LCD); however, they are inefficient in terms of energy usage since most of the energy input is lost as heat to the LCD. Furthermore, the LCD based additive manufacturing devices suffer from limitations in terms of wavelengths that can pass through the LCD. Some novel resin materials in three-dimensional (3D) printing use-cases require lower wavelengths to cure, which is not possible in such devices.

[0067] Furthermore, generally available photopolymer additive manufacturing devices have a lower wall of a vessel farmed of a flexible membrane, such as a silicon layer, Teflon film, fluorinated ethylene propylene (FEP) film, polyurethane, polytetrafluoroethylene (PTFE), or the like, which acts as a print surface so that the polymerized layers of material adhere to a build surface (as the build surface is preferably fabricated of aluminum, acrylic, polycarbonate, or other plastic to which the polymerized material adheres well) rather than the print surface. However, the flexible membrane has a short life and needs to be replaced from time to time, which is a hassle for the user (as replacing the membrane such as FEP film is a time-consuming process) and adds to an operational cost of the device. Also, the quality of printed objects may deteriorate as such separation films age, and so users may observe inconsistent print quality over time between replacement of such consumable films or layers. Additionally, during printing of an object, the polymerized layers still adhere to the membrane, and separation of the polymerized layers from the membrane reduces the manufacturing speed because of the considerable adhesion force bonding the polymerized layers to the membrane.

[0068] The present disclosure seeks to overcome one or more of the above disadvantages, or at least to provide a useful alternative.

[0069] Referring to FIGs. 1, 3, and 4, an additive manufacturing device 100 is shown according to some implementations of the present specification. In particular, FIG. 1 shows an isometric view of a cross section of the additive manufacturing device 100. FIGs. 3 and 4 show schematic views of the additive manufacturing device 100. The additive manufacturing device 100 is operable to produce an object 145. The additive manufacturing device 100 comprises a vessel 105 for containing a material 110 (e.g., resin) which is polymerizable on exposure to radiation. The vessel 105 has a lower wall 115 at a bottom of the vessel. The lower wall 115 is transparent to radiation of one or more wavelengths. Also, the lower wall 115 is curved. In some implementations, the lower wall 115 may have a thickness between 1 mm and 10 mm. In some implementations, a radius of curvature of the lower wall may be between 50 mm and 1000 mm. The curved lower wall 115 of the vessel can also be seen in FIGs. 2A and 2B, which show isometric views of a portion of the additive manufacturing device 100.

[0070] The lower wall 115 ofthe vessel comprises a print surface 120. In some implementations, print surface 120 is an upper face of the lower wall 115. The upper face of the lower wall 115 is a face of the lower wall 115 that is away from an irradiation unit 140, and that forms the print surface 120. A concave face of lower wall 115 faces towards irradiation unit 140. In some implementations, the lower wall 115 may comprise glass (e.g., the print surface 120 comprises glass). The glass may be scratch- resistant In some implementations, the glass may be tempered glass. As described previously, the lower wall 115 of the vessel 105 is curved. The curvature of the lower wall 115 aids in separation of the polymerized resin from the print surface 120. Furthermore, the print surface 120 is in direct contact with the material contained in the vessel. Simply stated, the curved print surface 120, whose curvature is oriented away from the irradiation unit 140, allows the additive manufacturing device 100 to be without the flexible membrane (as generally used in additive manufacturing devices). Therefore, the print surface 120 is in direct contact with the material contained in the vessel 105.

[0071] The vessel 105 may have sidewalls 125. In some implementations, the vessel 105 may have four sidewalls 125 defining an enclosure for containing the material 110.

[0072] The additive manufacturing device 100 further comprises a build platform 130 that is moveable relative to the vessel 105. In some implementations, the build platform 130 is capable of moving or being made to move vertically upwards relative to vessel 105 above an irradiation unit 140. In some implementations, the build platform 130 is configured for movement relative to the vessel 105 by means of a mechanical assembly (not shown in drawings) which may comprise ball screws, lead screws, belt drive mechanisms, a chain and sprocket mechanism, or a combination thereof, and a precision stepper motor, servo motor, or other means of drive. In some implementations, the mechanical assembly may comprise threaded rods and a stepper motor, which is driven by a controller (e.g., controller 150) of the device 100 and which may provide 5 μm precision in the vertical position of the build platform 130. The combined mechanical assembly and stepper motor may be fixed upon or connected to a frame which is supported on one or more the sidewalls 125. The frame provides rigid support and a reference point for the vertical position of the build platform 130. Greater precision (up to about 1 μm) may also be achieved through a suitable choice of lead screw or belt pitch and the resolution (steps per full revolution) of the drive motor.

[0073] The build platform 130 comprises a build surface 135, on which the objects) 145 (multiple objects 145 may be printed on the same build surface side by side) adhere to once printed. The build surface 135 faces towards the print surface 120 comprised in the lower wall 115 of the vessel 105. The build platform 130 is suspended inside the vessel such that the build surface 135 feces towards the print surface 120. To begin printing of the object 145, the build platform 130 is configured to be positioned such that a layer of material is defined between the build surface 135 and the print surface 120. The vessel 105 is also configured to move such that the print surface 120 rolls with respect to a reference plane 155 parallel to the build surface 135. In the context of the subject matter disclosed herein, the rolling of the print surface 120 suggests rolling of the print surface 120 without slipping with respect to the reference plane 155. The layer of material defined between the build surface 135 and the print surface 120 may be polymerized by exposure to radiation, e.g., by radiation from the irradiation unit 140. Once this layer of material is polymerized (e.g., by radiation from the irradiation unit 140), the polymerized layer adheres onto the build surface 135, and the build platform is configured to move such that a new layer of material is defined between the bottom face of the last polymerized layer (that now adheres onto the build surface 135) and the print surface 120. Once this layer is polymerized, the subsequent layers of material are defined between the last polymerized layer and the print surface 120, which are then polymerized by exposure to the radiation. This may also be referred to as progressive printing of the object 145, which includes that the first layer of a given object 145 is polymerized on the print surface 102, which adheres onto the build surface 135, whereafter subsequent layers adhere to preceding layers to form the printed object Subsequent layers are built upon previous ones as the build platform (e.g., build platform 130) is moved in the direction away from the print surface 102 after each layer, to create a 3D volumetric form as desired.

[0074] As described above, in some implementations, the lower wall 115 is curved and may comprise glass that has a lower surface roughness as compared to the build surface 135 (which may be formed of aluminum, steel, acrylic, polycarbonate, or other plastic, or combination thereof). The curvature and the material of the lower wall 115 (and thus the print surface 120) aid in separation of the polymerized layer from the print surface 120, and thus aid in adhesion of the polymerized layer onto the build surface 135 or the previous polymerized layer.

[0075] The additive manufacturing device 100 further comprises an irradiation unit 140 that is configured to generate radiation having a pattern to polymerize the material 110 contained in the vessel 105. The radiation may have the one or more wavelengths that are suitable for polymerizing the material 110 contained in the vessel 105. The irradiation unit 140 is configured to be positioned to irradiate the layer of material adjacent to the print surface 120. For example, for a first layer, the irradiation unit 140 is configured to be positioned to irradiate the layer of material defined between the build surface 135 and the print surface 120. For the subsequent layers, the irradiation unit 140 is configured to be positioned to irradiate the layer of material defined between the print surface 120 and the last polymerized layer.

[0076] The irradiation unit 140 may be disposed underneath the bottom of the vessel, e.g., below the print surface. As can be seen in Figs. 1, 3, 4, and 5, the curvature of the lower wall 115 (comprising the print surface) is oriented away from the irradiation unit 140. By virtue of the curvature of the lower wall 115 being oriented away from the irradiation unit 140 that is disposed underneath the lower wall 115, the radiation from the irradiation unit intersects the highest point on the lower wall 115 at any point in time, therefore the printing happens at the highest point on the lower wall 115 (illustrated in detail in Fig. 11).

[0077] The disposition of the irradiation unit 140 underneath the vessel 105 enables bottom-up printing, which is significantly advantageous to top-down printing wherein the irradiation unit is disposed above the resin tank or print surface. In the “top down” printing, the resin tank must have a depth equal to the desired height of printed objects, and must contain a large excess of resin. For example, if a tall thin tower structure, is to be printed, a massive volume of resin in a deep vessel would be required with top down printing. Whereas in the “bottom up” configuration, the vessel can be shallow as the build platform rises upwards as high as the user may wish depending on the height of the object to be printed. There just has to be enough resin to cover the print surface in 1-2 millimeters of resin for printing to occur.

[0078] Some example implementations of the irradiation unit 140 are shown in FIGs. 7 A, 7B, 8, and 9.

[0079] In some implementations, as can be seen for example from Fig. 4, the additive manufacturing device 100 may comprise a plurality of actuators that jointly enable the vessel 105 to move for the print surface 120 to roll without slipping with respect to the reference plane 155 parallel to the build surface 135. In some implementations, for the first layer, the build surface 135 is considered a reference plane with respect to which the print surface 120 rolls. For the subsequent layers, a bottom face (face closest to the print surface 120) of the last polymerized layer is considered the reference plane with respect to which the print surface 120 rolls. The plurality of actuators comprises a first actuator 160 feat is operatively coupled to the vessel 105 and that is configured to rotate the vessel 105 about a pivot axis 170, and a second actuator 165 that is configured to linearly displace a position of the pivot axis 170. The first actuator 160 and the second actuator 165 jointly enable the vessel 105 to move such feat the print surface 120 rolls wife respect to the reference plane 155 parallel to the build surface 135. In other words, the rotation of the vessel 105 about the pivot axis 170, for example enabled by the first actuator 160, and the linear displacement of the pivot axis 170, for example enabled by the second actuator 165, enables the print surface 120 to roll with respect to the reference plane 155 parallel to the build surface 135.

[0080] In some implementations, the first actuator 160 may comprise a linear motor, a ball screw, a lead screw, or belt and pulley system with stepper motor or servo motor, a chain and sprocket mechanism, or a combination thereof, and a precision stepper motor, servo motor, or other means of drive which may enable the rotation of the vessel 105 about the pivot axis 170. The first actuator 160 may comprise a hydraulic actuator, a pneumatic actuator, or the like, or a combination thereof, or any other means that is capable of rotation of the vessel 105 about the pivot axis 170 with desired speed and control. Similarly, the second actuator 165 may comprise a linear motor, a ball screw, a lead screw, or belt and pulley system with stepper motor or servo motor, a chain and sprocket mechanism, or a combination thereof, and a precision stepper motor, servo motor, or other means of drive which may enable the linear displacement of the pivot axis 170 and/or linear displacement of the irradiation unit 140 (which is explained below). Furthermore, the second actuator 165 may comprise a hydraulic actuator, a pneumatic actuator, or the like, or a combination thereof, or any other means that is capable of linear displacement of the pivot axis 170 and/or linear displacement of the irradiation unit 140 with desired speed and control. It is contemplated that the first actuator 160 and the second actuator 165 can be implemented in a number of ways, which may enable them to fulfil their functionality.

[0081] In some implementations, the first actuator may be mounted on the second actuator. The irradiation unit 140 may also be operatively coupled to the second actuator for the second actuator 165 to linearly displace the irradiation unit 140. The linear displacement of the irradiation unit 140 is synchronized with the linear displacement of the pivot axis 170. As can be seen in FIG. 4, the first actuator 160 is shown to be mounted on the second actuator 165, and that the irradiation unit 140 is operatively coupled to the second actuator 165. It is contemplated that a separate actuator (e.g., a third actuator) may also be employed to linearly displace the irradiation unit 140. In such cases, the irradiation unit 140 may not be operatively coupled to the second actuator 165.

[0082] Furthermore, the first actuator 160 and the second actuator 165 jointly enable the vessel 105 and the irradiation unit 140 to be moved and positioned such that the radiation generated by the irradiation unit 140 intersects the highest point of the print surface 120 comprised in the lower wall 115. The curvature of the print surface 120 being oriented away from the irradiation unit 140 facilitates the radiation from the irradiation unit 140 intersecting the highest point of the print surface 120. The highest point of the print surface 120 comprises a region of the print surface that is most proximate to the reference plane 155 parallel to the build surface 120. In other words, at least a section of a layer of material that is most proximate to the highest point of the print surface 120 may be polymerized by the radiation directed from the irradiation unit 140 at any position of the irradiation unit 140. In particular, the vessel 105 is configured to be moved by the first actuator 160 and the second actuator 165 about the pivot axis 170 such that the print surface 120 rolls with respect to the reference plane 155 parallel to the build surface 135. The rotation of the vessel 105 about the pivot axis 170 or the rolling of the print surface 120 is controlled to be in sync with the motion (e.g., linear displacement) of the irradiation unit 140 (controlled by the second actuator 165) for the highest point of the print surface 120 to intersect with the radiation generated by the irradiation unit 140. Such positioning of the vessel 105 and the irradiation unit 140 is illustrated in FIG. 5. As can be seen in FIG. 5, when the irradiation unit 140 displaces from the position 505 to 510, the vessel 105 moves for the print surface 120 to roll to a position such that the highest point of the print surface 120 intersects with the radiation generated by the irradiation unit 140.

[0083] In some implementations, as an alternative to the actuators 160 and 165, at least one actuation module in combination with a slip-prevent mechanism may be employed which may enable the print surface 120 to roll with respect to the reference plane 155 parallel to the build surface 135. FIGs. 6A and 6B show such example implementations 600A, 600B of the actuation module with slip-prevent mechanism. The actuation module 605 comprises a linear actuator 625 coupled to a passive roller module 630 that enables the movement of the vessel 105 such that the print surface 120 rolls with respect to the reference plane 155 parallel to the build surface 135. The actuation module 605 works jointly with a slip-prevent mechanism which prevents slipping of the print surface 120 with respect to the reference plane 155. In some implementations, the slip-prevent mechanism may comprise a toothed rack 610 and a pinion gear 615 (FIG. 6B), which prevents the print surface 120 from slipping while rolling with respect to the reference plane 155. In some implementations, the slip-prevent mechanism may comprise a mechanical bar linkage 620 (FIG. 6A), which prevents the print surface 120 from slipping while rolling with respect to the reference plane 155. A passive roller module engages the actuation module with a primary rigid bar, and a second passive roller module engages with a secondary rigid bar which is curved such that it constrains the rolling motion of the primary bar to occur without slipping. FIGs. 6A and 6B show the lower wall 115 of the vessel 105 being coupled to one actuation module 605. However, it is contemplated that in some implementations, a plurality of actuation modules 605 may be employed. For example, in some implementation, one actuation module 605 may be employed on each side of the lower wall 115 of the vessel 105. Furthermore, in some implementations, the irradiation unit 140 may be coupled to the linear actuator of the actuation module 605, which may enable the linear displacement of the irradiation unit 140.

[0084] The linear displacement of the pivot axis implies that each point on the pivot axis traverses a linear path, which can be realized by employing a single motor and which is operationally easier to implement as compared to prior solutions. For example, some prior solutions describes an additive manufacturing device with curved solidification substrates, where each point on the curved surface traverses a trochoidal path during an object-building operation. However, such device needs to employ a plurality of motors to achieve lateral, vertical, and pivotal displacement, for each point on the curved surface to traverse a trochoidal path, which is far more complex to implement as compared to the solutions described herein in which each point on the pivot axis traverses a linear path (in contrast to a trochoidal path). The linear displacement of the pivot axis to achieve rolling motion of the vessel is not only easier to implement but also improves the quality and precision of printed objects, and also reduces cost and complexity of assembly and maintenance of the additive manufacturing device.

[0085] In some implementations, as can be seen for example from Fig. 3, the additive manufacturing device 100 may further comprise a controller 150 that may control various electrical, mechanical, electro-mechanical, and/or optical components of the additive manufacturing device 100. The controller 150 may comprise one or more processors that are in communication with one or more computer readable storage mediums, which may include, for example, non-volatile storage (such as a hard disk or solid-state disk), random access memory (RAM), or the like. The storage mediums may store computer-executable instructions, which in response to execution by the one or more processors may cause the controller 150 to perform operations such as those related to controlling various electrical, mechanical, electro-mechanical, sensory, and/or optical components of the additive manufacturing device 100.

[0086] The operations or processes executed by the controller 150 may be implemented in the form of programming instructions of one or more software modules or components stored on the storage medium. However, it is contemplated that the processes or operations executed by the controller 150 could alternatively be implemented, either in part or in their entirety, in the form of one or more dedicated hardware components, such as application-specific integrated circuits (ASICs), microcontrollers, and/or in the form of configuration data for configurable hardware components such as field programmable gate arrays (FPGAs), for example.

[0087] In some implementations, the controller 150 may coordinate the overall flow of an additive manufacturing process. For example, the controller 150 may generate control signals to drive mechanical components of the additive manufacturing device, such as pumps, motors, and actuators, such as actuators 160 and 165. The controller 150 may also process signals from various sensors, as disclosed herein, and control various components accordingly. Furthermore, the controller 150 may generate control signals to control the irradiation unit 140, such as to turn the irradiation unit 140 ON and OFF, to control the duration and intensity of irradiation, or the like.

[0088] In some implementations, the first actuator 160 may comprise a rotary encoder that is configured to feedback an angular position of the vessel 105 to the controller 150. Similarly, the second actuator 165 may comprise a linear encoder that is configured to feedback a linear position of the pivot axis 170 (and/or linear position of the irradiation unit 140) to the controller 150. The feedback of the angular position of the vessel 105 and the linear position of the pivot axis 170 and/or the linear position of the irradiation unit 140 may enable the controller 150 to control motion of the vessel 105 and the irradiation unit 140, and control irradiation of the material contained in the vessel 105. The feedback of the angular position of the vessel 105, and the linear position of the irradiation unit 140 may enable the controller 150 to control the irradiation unit 140 accordingly. For example, based on the angular position of the vessel 105 (that includes angular position of the print surface 120), and the linear position of the irradiation unit 140, the controller 150 may determine if the irradiation unit 140 is to be ON or OFF, i.e. if the irradiation unit 140 is to irradiate the material adjacent to the print surface 120 at that position of the vessel 105 and the irradiation unit 140. For example, if the irradiation unit 140 is a laser diode based irradiation unit (as described below in relation to FIGs. 7 A and 7B), the controller 150 may control pulsing on/off the laser diode (e.g., laser diode 705), the spinning speed and/or position of the rotating polygon reflector (e.g., rotating polygon reflector 710), and the positions of the actuators 160, 165, based on the feedback received from the linear encoder and the rotary encoder. [0089] In some implementations, the combined coordinate of (a) angular position of the spinning mirror, (b) angular position of the vessel and lateral position of the irradiation unit, will indicate to the controller whether the laser should be exposing (irradiating resin) or not The controller 150 may control the pulsing on/off of the laser, the spinning speed and/or position of the polygon mirror, and the angular and lateral position of the vessel motion control actuators.

[0090] FIGs. 7 A and 7B show example irradiation units 700a and 700b, which may be employed as an irradiation unit 140 in the additive manufacturing device 100. The irradiation units 700a or 700b may be disposed underneath the bottom of the vessel, e.g., below the lower wall 115 of the vessel 105.

[0091] The irradiation unit 700a comprises a laser diode 705 that generates a laser beam that is directed towards a rotating polygon reflector 710. The rotating polygon reflector 710 moves continuously in a direction to scan the laser beam along the desired path. By virtue of its shape, the movement of the rotating polygon reflector 710 results in a linear scanning pattern. The scanned laser beam is directed from the rotating polygon reflector 710 to an optical assembly, e.g., f-theta lens 720 that focuses the laser beam onto the print surface 120. The f-theta lens 720 enables the laser beam to be focused on a flat reference plane at the focal point that may lie on the print surface 120. The laser diode 705 is operable to be pulsed on/off via a signal from the controller 150.

[0092] Optionally, the irradiation unit 700a may comprise another optical component 715 disposed between the laser diode 705 and the rotating polygon reflector 710. The optical component 715 is configured to modify the laser beam generated by the laser diode 705. In some examples, the optical component 715 may comprise a collimator lens that collimates the laser beam, and/or a cylinder lens that converges the laser beams onto the rotating polygon reflector 710.

[0093] In some implementations, the irradiation unit 700a may comprise a plurality of sensors that measure a position and a speed of rotation of the rotating polygon reflector 710. The measured position and speed of the rotating polygon reflector 710 are fed back to the controller 150 for calibration purposes. In some implementations, the controller 150 may control pulsing the laser diode 705 ON/OFF at given coordinates to build the given object based on the measured position and the speed of rotation of the rotating polygon reflector 710. The pulsing ON/OFF of the laser diode 710 may be to generate the radiation of the particular pattern, which correspond to the object 145 to be built [0094] Another irradiation unit 700b employing a laser diode 705 is shown in FIG. 7B. The irradiation unit 700a is similar to irradiation unit 700b except that in irradiation unit 700b, a laser galvanometer 725 is used instead of the rotating polygon reflector 710. The laser galvanometer 725 rotates a mirror back and forth with a high degree of precision, to direct the laser beam to desired positions on the printing plane.

[0095] In some implementations, the irradiation unit 700a or 700b may further comprise a light intensity measurement sensor upon which a laser beam emitted from the laser diode 705 may be directed, and a measured intensity of the laser beam is fed back to the controller 150 for calibration purposes. In some implementations, the light intensity measurement sensor may be positioned near an edge of the curved lower wall 115, where the laser beam from the irradiation unit 700a or 700b can be directed to.

[0096] FIG. 8 shows another example irradiation unit 800, which may be employed as the irradiation unit 140 in the additive manufacturing device 100. The irradiation unit 800 may be disposed underneath the bottom of the vessel, e.g., directly below the lower wall 115 of the vessel 105. The irradiation unit 800 comprises an array 805 of individually addressable radiation emitting elements. The radiation emitting elements may be light emitting diodes (LEDs). The array 805 may emit radiation such that the material 110 inside the vessel 105 polymerizes when exposed to light emitted by the array 805. The array 805 may be configured to emit a patterned beam of radiation to cure the material 110 in the vessel 105 with a desired pattern. The radiation emitted by the array 805 may have suitable wavelength to polymerize the material 110 inside the vessel 105. The individually addressable LEDs of the array 805 may be switched on or off by the controller of the device 100 (e.g., controller 150), which may be coupled to the array 805 through electrical connections and/or device drivers. When an LED in the array is activated (switched on), it emits the light, whereas when it is inactive (switched off), it does not emit light Accordingly, the LEDs of the array 805 can be programmed by the controller 150 to produce the desired pattern of radiation. The individually addressable LEDs of the array 805 may, in principle, be designed to emit any particular wavelength of light, e.g., visible, ultraviolet (UV), or infrared (IR), or the like to match the specific polymerization requirement of the polymerisable material 110. [0097] The array 805 may be supported by a substrate backplane underneath the array, which provides electrical connectivity to terminals of each LED while also serving as a mechanical support.

[0098] In some implementations, the LEDs of the array 805 are micro-LEDs. In other words, the irradiation unit 800 may comprise a linear array of micro LEDs. Each micro LED may be switched ON or OFF, e.g., by the controller 150, to generate the particular radiation pattern. Micro LED display is an emerging technology that is being developed for the next generation of LED displays and imaging applications. When compared with widespread LCD technology, micro LED display offers better contrast, response times, and energy efficiency. Micro LEDs generate their own light and do not require a backlight Hence, the Micro LED array offers greatly reduced energy requirements when compared to conventional LCD systems. Moreover, Micro LEDs offer far greater total brightness and do not suffer from bum-ins.

[0099] The array 805 may be sized to cover one dimension (length or width) of the print surface 120. In some implementations, the array 805 may cover a surface area which is smaller than the dimension of print surfrice 120. In some implementations, the array 805 may be a linear array (e.g., one dimensional array) that is sized to cover the print surface 120 one dimensionally (e.g., full length or full width of the print surface 120) substantially. Further, an actuation system such as the actuator 165 may move the array 805 along the other axis, which may allow the array 805 to cover and scan across the whole surface area of the print surface 120 i.e., cover both dimensions of the print surface 120.

[0100] Further, the irradiation unit 800 comprises a gradient-index (GRIN) lens array 810, disposed in the path of light emitted from the radiation emitting elements (e.g., LEDs or micro LEDs). The GRIN lens array 810 may comprises lenses, such as Selfoc lenses, that project a positive image of the radiation emitting elements (e.g., LEDs or micro LEDs) of the array 805. The GRIN lens array 810 may be employed to collimate the radiation beams emitted by the radiation emitting elements of the array 805. The GRIN lens array 810 projects a positive image of the radiation emitting element across a desired throw distance, thus enabling placing a pane of glass in the optical path and forming a vessel for the material. [0101] FIG. 9 shows another example irradiation unit 900, which may be employed as the irradiation unit 140 in the additive manufacturing device 100. The irradiation unit 900 may be disposed underneath the bottom of the vessel, e.g.., directly below the lower wall 115 of the vessel 105.

[0102] The irradiation unit 900 comprises a linear array 905 of LED modules 910. Each LED module 910 comprises an LED, and a lens configured to focus the light emitted by the LED to a demagnified image of the LED. Similar to the array 805, the array 905 may be configured to emit a patterned beam of radiation to cure the material 110 in the vessel 105 with a desired pattern. The radiation emitted by the array 905 may have suitable wavelength to polymerize the material 110 inside the vessel 105. The LEDs of the array 905 may be switched on or off by the controller of the device 100 (e.g., controller 150), which may be coupled to the array 905 through electrical connections and/or device drivers. When the LED is activated (switched on), it emits the light, whereas when it is inactive (switched off), it does not emit light Accordingly, the LEDs of the array 905 can be programmed by the controller 150 to produce the desired pattern of radiation. LEDs of the array 905 may, in principle, be designed to emit any particular wavelength of light, e.g., visible, ultraviolet (UV), or infrared (IR), or the like to match the specific polymerization requirement of the polymerisable material 110.

[0103] Each LED module 910 is separated by a distance from an adjacent LED module 910. The irradiation unit 900 further comprises an actuator 915 to oscillate the array 905 such that the array 905 covers one entire one dimension (e.g., length or width) of the print surface 120. The actuator 915 may oscillate the array 905 with an amplitude of the oscillatory motion that is equal to or greater than a distance between the LED modules 910.

[0104] In a defined position (e.g., original static position), each LED module 910 projects light onto a small region of the print surface 120 above it Due to the gap between the LED modules, there is a gap between the region illuminated by one LED module and the region illuminated by a neighboring LED module. The oscillation motion caused by the actuator 915 effectively moves each LED module 910 back and forth between two terminal positions, and through a multitude of intermediate positions along in between, along the direction of the oscillating motion. The LED module 910 is pulsed ON/OFF (e.g., by the controller 150, based on an input file containing build instructions), such that every region of material that can be defined in the large distance between the regions illuminated by neighboring LED modules in their original (static) positions, can be individually illuminated by an LED module during the oscillatory motion (e.g., by pulsing the LED "ON" when it passes underneath a region of material that is to be illuminated).

[0105] The oscillation of the array 905 may enable the array 905 to cover the print surface 120 one dimensionally (e.g., full length or full width of the print surface 120) substantially. Further, an actuation system such as the actuator 165 may move the array 905 along the other axis, which may allow the array 905 to cover and scan across the whole surface area of the print surface 120.

[0106] It is to be noted that FIGs. 7 A, 7B, 8, and 9 show some examples of the irradiation units that may be employed in additive manufacturing devices disclosed herein. It is contemplated that the additive manufacturing device 100 may be realized with some other irradiation units such as irradiation units that may be modified versions of the example irradiations units disclosed herein. Such modifications and implementations are considered to be covered by the scope of this disclosure.

[0107] FIG. 10 illustrates a flow diagram of an example additive manufacturing method 1000 according to some implementations of the present specification.

[0108] At 1005, a vessel (e.g., vessel 105) is provided. The vessel has a lower wall (e.g., lower wall 115) at a bottom of the vessel. The lower wall is curved, and at least partially transparent to radiation at one or more wavelengths. The lower wall comprises a print surface (e.g., print surface 120). At 1010, the vessel (e.g., vessel 105) is filled with a material (e.g., material 110) which is polymerisable on exposure to radiation at the one or more wavelengths.

[0109] At 1015, an irradiation unit (e.g., irradiation unit 140) is provided. The irradiation unit is configured to generate the radiation having a pattern to polymerize the material contained with the vessel. For example, the irradiation units 700a, 700b, 800, or 900 may be provided as the irradiation unit 140. The irradiation unit is disposed underneath the bottom of the vessel.

[0110] At 1020, a build platform (e.g., a build platform 130) having a build surface (e.g., build surface 135) is positioned relative to the vessel (e.g., vessel 105) such that a layer of material is defined between the build surface (e.g., build surface 135) and the print surface (e.g., print surface 120). [0111] At 1025, the layer of material is irradiated with radiation generated by the irradiation unit (e.g., irradiation unit 140). The vessel (e.g., vessel 105) and the irradiation unit (e.g., irradiation unit 140) may be positioned for the irradiation unit (e.g., irradiation unit 140) to irradiate the layer of material that is adjacent to the print surface (e.g., print surface 120). The vessel (e.g., vessel 105) is positioned by the moving the vessel such that the print surface (e.g., print surface 120) rolls with respect to a reference plane (e.g., reference plane 155) that is parallel to the build surface (e.g., build surface 135). The print surface 120 may roll such that the highest point of the print surface 120 intersects with the radiation generated by the irradiation unit 140 at any position.

[0112] The process of positioning the vessel (e.g., vessel 105), the build platform (e.g., build platform 130), and the irradiation unit (e.g., irradiation unit 140) for irradiating the material (e.g., material 110) contained in the vessel (e.g., vessel 105) is explained in greater detail in relation to FIG. 11 below.

[0113] FIG. 11 shows an example process 1100 of irradiation of layers of material to print an object by an additive manufacturing device 100.

[0114] To irradiate each layer of material, the irradiation unit 140 is linearly displaced from one linear position to another linear position in a continuous motion such that the irradiation unit 140 passes through a finite number of linear positions at each of which the irradiation unit may irradiate a section of a layer of material that is adjacent to the print surface 120. The displacement of the irradiation unit 140 from a first linear position (one of the end positions) to a second linear position (the other of the end positions) may result in irradiation of the layer of the material that is adjacent to the print surface 120.

[0115] In synchronization with the linear displacement of the irradiation unit 140, the vessel 105 is moved such that the print surface 120 rolls from one angular position to another angular position in a continuous motion such that each angular position of the print surface 120 corresponds to the corresponding linear position of the irradiation unit 140. The irradiation unit 140 and the vessel 105 may be moved or displaced by a combination of actuators such as actuators 160, 165. The linear displacement of the irradiation unit 140 is synchronized with the movement of the vessel 105 such that at any linear position of the irradiation unit 140, the highest point of the print surface 120 intersects with the radiation emitted by the irradiation unit 140. The intersection of the highest point of the print surface 120 with the irradiation unit 140 may result in curing of a section of a layer of material that is most proximate to the highest point of the print surface 120.

[0116] The example positioning of the irradiation unit 140, the vessel 105 or the print surface 120, and the build platform 130 to print the object 145 are illustrated in FIG. 11. FIG. 11 show various states of the device 100 while printing the object 145. The object 145 is made up of many layers. States 1105 to 1120 pertain to polymerization of a n^th layer. States 1125 to 1140 pertain to polymerization of (n+1)^th layer. The other layers are polymerized in a similar manner as described below for n^th and (n+1)^th layer.

[0117] At 1105, the irradiation unit 140 is positioned at a first linear position (e.g., a first end position), and the vessel 105 is moved such that the print surface 120 is at a first angular position that corresponds to the first linear position of the vessel 105. As can be seen in FIG. 11 , at 1105, the highest point of the print surface 120 intersects with the radiation from the irradiation unit such that a section of the n^th layer that is adjacent to the print surface 120 (e.g., most proximate to the highest point of the print surface) is irradiated by the radiation from the irradiation unit 140.

[0118] To print the next section of the n^th layer, the irradiation unit may be linearly displaced (left to right) such that the irradiation unit 140 is at an intermediate linear position (state 1110). The linearly displacement of the irradiation unit 140 is in sync with the movement of the vessel 105 which results in rolling of the print surface 120 to be at an intermediate angular position. As can be seen in FIG. 11, at 1110, when the print surface 120 is at the intermediate angular position, the highest point of the print surface 120 intersects with the radiation from the irradiation unit 140. At 1110, the next section of the n^th layer, which is now most proximate to the highest point of the print surface, is now irradiated by the radiation from the irradiation unit 140.

[0119] At 1115, the irradiation unit 140 is shown to be at the second linear position (e.g., a second end position). In other words, the irradiation unit 140 is linearly displaced from the intermediate linear position to the second linear position (left to right). The vessel 105 is also moved such that the print surface 120 rolls from the intermediate angular position to a second angular position. Similar to other angular positions, at the second angular position, the highest point of the print surface intersects with the radiation from the irradiation unit 140. At 1115, the last section of the n^th layer, which is now most proximate to the highest point of the print surface 120, is now irradiated by the radiation from the irradiation unit 140. Thus the whole n^th layer has been irradiated and thus polymerized.

[0120] At 1120, after the n^th layer is irradiated e.g., after the irradiation unit 140 is at the second linear position, the build platform 130 moves away from the print surface 120 by a distance such that a new layer of material e.g., (n+1)^th layer is defined between a bottom surface of the last polymerized layer (n^th layer) and the print surface 120. While the build platform 130 is moving away from the print surface 120, the irradiation unit 140 is configured to not generate the radiation (e.g., the irradiation unit 140 being turned OFF) until the new layer is defined between the last polymerized layer and the print surface 120.

[0121] At 1125, once the new layer is defined between the bottom surface of the last polymerized layer (n^th layer) and the print surface 120, a first section of the next layer (n+1^th layer) is irradiated by the radiation from the irradiation unit 140 that is at the second linear position. The print surface 120 is at the second angular position while the first section of the (n+1)^th layer is being irradiated and thus polymerized.

[0122] To irradiate the next section of the (n+1)^th layer, the irradiation unit is linearly displaced from the second linear position towards the first linear position (from right to left) such that the irradiation unit 140 is at an intermediate linear position (state 1130). The linear displacement of the irradiation unit 140 is in sync with the movement of the vessel 105, which results in rolling of the print surface 120 (from the second angular position towards the first angular position) to be at an intermediate angular position. As can be seen in FIG. 11, at 1130, when the print surface 120 is at the intermediate angular position, the highest point of the print surface intersects with the radiation directed by the irradiation unit 140. At 1130, the next section of the (n+1)^th layer, which is now most proximate to the highest point of the print surface 120, is now irradiated by the radiation from the irradiation unit 140.

[0123] At 1135, the irradiation unit 140 is shown to be at the first linear position (e.g., a second end position). In other words, the irradiation unit 140 is linearly displaced from the intermediate linear position to the first linear position. The vessel 105 is also moved such that the print surface 120 rolls from the intermediate angular position to the first angular position. Similar to other angular positions, at the first angular position, the highest point of the print surface intersects with the radiation from the irradiation unit 140. At 1135, the last section of the (n+1)^th layer, which is now most proximate to the highest point of the print surface 120, is now irradiated by the radiation from the irradiation unit 140. Thus the whole (n+1)^th layer has been irradiated and thus polymerized.

[0124] At 1140, after the (n+1)^th layer is irradiated e.g., after the irradiation unit 140 is at the first linear position, the build platform 130 moves away from the print surface 120 by a distance such that a new layer of material e.g., (n+2)^th layer is defined between a bottom surface of the last polymerized layer ((n+1)^th layer) and the print surface 120. While the build platform 130 is moving away from the print surface 120, the irradiation unit 140 is configured to not generate the radiation (e.g., the irradiation unit 140 being turned OFF) until the new (n+2)^th layer is defined between the last polymerized layer and the print surface 120.

[0125] The steps corresponding to states 1105 to 1140 are repeated until the whole object 145 has been manufactured (printed). In other words, the next layers of material are irradiated and thus polymerized similar to the example n^th layer and (n+1)^th layer. For example (n+2)^th, (n+4)^th (n+6)^th, and so on layers are irradiated (and thus polymerized) similar to the n^th layer i.e., as the irradiation unit 140 linearly displaces from the first linear position to the second linear position and the print surface 120 rolls from the first angular position to the second angular position. And similarly, (n+3)^th, (n+5)^th, (n+7)^th, and so on layers are irradiated (and thus polymerized) similar to (n+1)^th layer i.e., as the irradiation unit 140 linearly displaces from the second linear position to the first linear position and the print surface 120 rolls from the second angular position to the first angular position.

[0126] The irradiation unit 140 scans back and forth (left to right, and right to left) to print successive layers. As described above, for the n^th, (n+2)^th, (n+4)^th, (n+6)^th, and so on layers to be polymerized, the irradiation unit 140 scans (generates radiation-ON configuration) while linearly displacing from the first linear position to the second linear position (left to right displacement). For (n+1)^th (n+3)^th, (n+5)^th, (n+7)^th and so on layers to be polymerized), the irradiation unit 140 scans (generates radiation- ON configuration) while linear displacing from the second linear position to the first linear position (right to left displacement). [0127] Additive manufacturing devices, systems, and methods disclosed herein possess several advantages and benefits as compared to generally known additive manufacturing devices (e.g., 3D printers).

[0128] Typically additive manufacturing devices create objects by ‘stacking’ two-dimensional layers on top of each other. These devices must complete four distinct steps to create each of these individual layers- Step 1 (Irradiate): A thin layer of material is illuminated by a patterned radiation. The radiation solidifies the material in a desired shape, which is effectively the cross section of the printed object at this point; Step 2 (Separate): A build platform (also referred to as “print platform” in some cases) is very slowly moved up, so that the polymerized layer is carefully separated from the base of a vessel. As described previously, often the base is a (consumable) flexible membrane, which eases the separation; Step 3 (Reflow): The build platform is pulled upwards more quickly now, to enlarge the gap between the polymerized layer (which now adheres onto a build surface of the build platform) and the base of the vessel (flexible membrane), which allows the material to fill the void below the polymerized layer; and Step 4 (Squeeze)- The build platform is pushed back downward in a precisely controlled motion to sandwich a new layer of material between the polymerized layer and the base of the vessel, the new layer of material is now ready to be irradiated and polymerized (back to Step 1).

[0129] In each of the three steps/processes (Separate, Reflow and Squeeze), the forces involved (and generally the time taken) are proportional to the square of the surface area being printed. Consider an example where the time to print an object having layer cross sections that measure 1 x 10 units is T. Now to print an area that is 10 times larger (e.g.,10 x 10 units), it involves 10² times greater forces and takes proportionally more time to complete on conventional additive manufacturing devices. In other words, since the print area is lOx larger than before, the time taken is 10² = 100 times longer (100xT), due to the exponential nature of separation and reflow forces. Therefore, the conventional 3D printers are far too slow for many commercial use-cases.

[0130] As described previously, the additive manufacturing devices disclosed herein employ a rolling curved print interface that irradiates and polymerizes layers section-wise, which enable all four processes (Irradiate, Separate, Reflow, and Squeeze) to happen simultaneously for a section of the layer (e.g., narrow linear strip), (a) Irradiation is occurring continuously, at the highest point of the curved surface, where the layer of material defined between the print surface and the bottom of the last polymerized layer is thinnest (b) Separation and reflow are happening continuously on the trailing edge of the curved surface in the direction it is rolling; where the curvature of the surface tends away ftom the polymerized section of the layer of material, (c) Squeezing of material down to the desired layer thickness is also happening continuously, at the leading edge of the rolling curved print surface, where the gap between the print surface and the bottom face of the last polymerized layer gets continuously smaller towards the highest point of the print surface. When polymerized small strips (sections of layers) are continuously created directly adjacent to one another in this manner, they together form the same full-size object layer, but the time taken to do so just stacks up linearly (instead of exponentially). With reference to the above example; producing a 10x10 unit sized layer, the process could be divided into 10 separate strips each measuring 1x10 units. Since the forces associated with separation, reflow and squeezing are occurring continuously (or rather, 10 times sequentially in this example, once for each segment), the overall peak force occurring in the device is much lower than when the full 10x10 unit layer is printed and subsequently separated, reflowed, and squeezed all at once. In this example, the time taken to produce 10 such segments of 10x1 units sequentially is just 10 x T.

[0131] In other words, the rolling curved print interface as disclosed herein enables sequentialization of the printing process, e.g., the polymerization of the layer section wise (as compared to whole layer being polymerized and then separated at once) facilitates low separation forces (small surface area separates exponentially easier than larger surface area). The rolling of the curved print surface enables the small, irradiated section of the layer to separate continuously from the print surface (“continuous linear separation”), since it is very small in surface area, which means the separation forces associated with the layer separation are kept orders of magnitude lower, as c

red to conventional additive manufacturing devices, where a large area is first polymerized and then separated all at once. The reduction of separation forces significantly expedites the printing process (e.g., 10X to 20X faster as compared to similar typical additive manufacturing devices).

[0132] Also, as described previously, generally available additive manufacturing devices require the lower wall of the vessel to be formed of a flexible membrane, such as a FEP, PTFE, or Teflon film. Such films have a short life and need to be replaced from time to time, which is a hassle for the user (as replacing the film is a time-consuming process) and adds to an operational cost of the device. By virtue of having a rolling curved lower wall, the additive manufacturing device disclosed herein does not require the lower wall of the vessel to be formed of flexible membrane such as Teflon film, thus eliminating the need for a flexible membrane altogether, which is thus significantly advantageous. Also as described previously, the rolling curved lower wall of the vessel or curved print surface enables the material to reflow easily and fill a void created by the upward movement of the build platform, thus reducing the forces required to separate the polymerized layer from the print surface, thus eliminating the need for the flexible membrane. The reduction of force expedites the printing process.

[0133] The generally available additive manufacturing devices that employ the flexible membrane also suffer from print speed disadvantages. In such devices, when one layer is printed, the build platform moves up and peels the object off the membrane, and then comes down again to define a layer of resin for the subsequent curing cycle. This process (up + down for separation, reflow and layer definition) takes time, which slows the printing process. However, by employing the curved print surface that may be made out of a non-stick or low surface energy or oxygen permeable, rigid material, the flexible membrane is not required, due to which the release of each printed line element happens immediately and as a result of the rolling motion itself, rather than being a separate process after the printing of the layer is completed.

[0134] Additionally, the additive manufacturing devices disclosed herein employ irradiation units such as the micro LED based irradiation unit, which has very high light intensity, can be 50x higher than conventional DLP or SLA based printers. This results in better printing and higher printing speed as compared to conventional DLP or SLA based printers. The additive manufacturing devices as disclosed herein also enable 3D printing with higher resolution, at larger scale, as well as greater brightness, better uniformity, and higher efficiency than conventional 3D printing techniques.

[0135] Whilst there has been described in the foregoing description exemplary embodiments of the present invention, it will be understood by those skilled in the technology concerned that many variations and combination in details of design, construction and/or operation may be made without departing from the present disclosure. For example, additive manufacturing devices having bottom- up configuration are disclosed herein for illustrative purposes only. The systems and methods disclosed herein may be realized for other different types of additive manufacturing devices, which may have different configurations such as, but not limited to, a top-down configuration.

Claims

We Claim:

1. An additive manufacturing device comprising, a vessel for containing a material that is polymerizable on exposure to radiation at one or more wavelengths, the vessel having a lower wall at a bottom of the vessel, the lower wall being curved, and at least partially transparent to the radiation at the one or more wavelengths, and the lower wall comprising a print surface; a build platform having a build surface, the build platform being configured for movement relative to the vessel such that a layer of material is defined between the build surface and the print surface; and an irradiation unit disposed underneath the bottom of the vessel, the irradiation unit being configured to generate radiation at the one or more wavelengths, the radiation having a pattern to polymerize the material contained within the vessel, wherein the vessel is configured to move for the print surface to roll with respect to a reference plane parallel to the build surface, wherein the irradiation unit is configured to be positioned to irradiate a layer of material that is adjacent to the print surface, and wherein the curvature of the lower wall is oriented away from the irradiation unit.

2. The additive manufacturing device of claim 1, wherein the irradiation unit comprises a laser diode.

3. The additive manufacturing device of claim 2, further comprising: a controller, wherein the laser diode is operable to be pulsed on/off via a signal from the controller.

4. The additive manufacturing device of claim 2, wherein the irradiation unit further comprises a rotating polygonal reflector.

5. The additive manufacturing device of claim 2, wherein the irradiation unit further comprises a laser galvanometer.

6. The additive manufacturing device of claim 5, further comprising: a controller, wherein the irradiation unit comprises a first sensor and a second sensor, and wherein a speed of rotation of the rotating polygon reflector is measured by the first sensor and fed back to the controller, and wherein a position of the rotating polygon reflector is measured by the second sensor and fed back to the controller.

7. The additive manufacturing device of claim 1, wherein the irradiation unit comprises a linear array of individually addressable light emitting diodes (LEDs).

8. The additive manufacturing device of claim 7, wherein the LEDs comprise micro LEDs.

9. The additive manufacturing device of claim 7, wherein the irradiation unit further comprises a gradient-index (GRIN) lens array.

10. The additive manufacturing device of claim 1, wherein the irradiation unit comprises a linear array of light emitting diode (LED) modules.

11. The additive manufacturing device of claim 10, wherein each LED module comprises an LED, and a lens configured to focus the light emitted by the LED to a demagnified image of the LED.

12. The additive manufacturing device of claim 10, wherein the irradiation unit further comprises an actuator that is configured to oscillate the linear array of LEDs, and wherein an amplitude of the oscillatory motion is equal to or greater than a distance between the LED modules.

13. The additive manufacturing device of claim 1, further comprising: a first actuator operatively coupled to the vessel and configured to rotate the vessel about a pivot axis; and a second actuator configured to linearly displace a position of the pivot axis, wherein: the first actuator and the second actuator are configured to jointly enable the print surface to roll with respect to the reference plane parallel to the build surface, the irradiation unit is operatively coupled to the second actuator for the second actuator to linearly displace the irradiation unit, the second actuator is configured to linearly displace the irradiation unit back and forth between a first linear position and a second linear position, the first linear position and the second linear position having at least one intermediate linear position in-between, wherein at each position, the radiation generated by the irradiation unit irradiates a section of the layer of material adjacent to the print surface, the section corresponding to the position of the irradiation unit, the first actuator and the second actuator are configured to jointly move the vessel for the print surface to roll back and forth between a first angular position and a second angular position, the first angular position and the second angular position having at least one intermediate angular position in-between, wherein each angular position of the print surface corresponds to the corresponding linear position of the irradiation unit, after the irradiation unit is displaced from the first linear position to the second linear position, or from the second linear position to the first linear position, the build platform is configured to be moved away from the print surface by a distance that defines a new layer of material between a bottom surface of the last polymerized layer and the print surface, and the first actuator and the second actuator are configured to jointly move the vessel for the highest point of the print surface to intersect with the radiation generated by the irradiation unit

14. The additive manufacturing device of claim 1, further comprising: at least one actuation module operatively coupled to the vessel and configured to enable the print surface to roll with respect to the reference plane parallel to the build surface; and a mechanism that prevents the print surface from slipping with respect to the reference plane.

15. The additive manufacturing device of claim 14, wherein the mechanism comprises one of: a toothed rack and a pinion gear, and a mechanical bar linkage.

16. An additive manufacturing method comprising, providing a vessel having a lower wall at a bottom of the vessel, the lower wall being curved, and at least partially transparent to radiation at one or more wavelengths, the lower wall comprising a print surface; at least partially filling the vessel with a material which is polymerisable on exposure to the radiation at the one or more wavelengths; providing an irradiation unit that is configured to generate radiation at the one or more wavelengths, the radiation having a pattern to polymerize the material contained within the vessel, wherein providing the irradiation unit comprises disposing the irradiation unit underneath the bottom of the vessel; positioning a build platform having a build surface relative to the vessel such that a layer of material is defined between the build surface and the print surface; and irradiating, with the radiation from the irradiation unit, the layer of material to polymerize the layer of material, wherein irradiating the layer of material comprises positioning the vessel and the irradiation unit for the irradiation unit to irradiate the layer of material that is adjacent to the print surface, wherein positioning the vessel comprises enabling the vessel to move for the print surface to roll with respect to a reference plane parallel to the build surface, and wherein providing the vessel comprises orienting the curvature of the lower wall away from the irradiation unit

17. The additive manufacturing method of claim 16, wherein positioning the vessel comprises: rotating, by a first actuator, the vessel about a pivot axis; and linearly displacing, by a second actuator, a position of the pivot axis, wherein the rotation of the vessel, and the linear displacement of the pivot axis enable the print surface to roll with respect to the reference plane parallel to the build surface.

18. The additive manufacturing method of claim 17, wherein the irradiation unit is operatively coupled to the second actuator, and positioning the irradiation unit comprises: linearly displacing, by the second actuator, the irradiation unit

19. The additive manufacturing method of claim 16, wherein irradiating the layer of material comprises:

(i) linearly displacing the irradiation unit from a first linear position to a second linear position, the irradiation unit having at least one intermediate linear position between the first linear position and the second linear position, wherein at each position: the irradiation unit generates radiation, which irradiates a section of the layer of material adjacent to the print surface, the section corresponding to the position of the irradiation unit;

(ii) moving the vessel for the print surface to roll from a first angular position to a second angular position, the print surface having at least one intermediate angular position between the first angular position and the second angular position, wherein each angular position of the print surface corresponds to the corresponding linear position of the irradiation unit;

(iii) after the irradiation unit is at the second linear position, moving the build platform away from the print surface by a distance that defines a new layer of material between a bottom surface of the last polymerized layer and the print surface;

(iv) irradiating the new layer of material, defined by the movement of the build platform, by: linearly displacing the irradiation unit from the second linear position to the first linear position, and by moving the vessel for the print surface to roll from the second angular position to the first angular position; and

(v) after the irradiation unit is at the first linear position, moving the build platform away from the print surface by the distance; and

(vi) repeating (i)-(v) until an object has been printed.

20. The additive manufacturing method of claim 19, wherein moving the vessel comprises: moving the vessel for the highest point of the print surface to intersect with the radiation generated by the irradiation unit.