HK1252401B - Leveling apparatus for a 3d printer - Google Patents

Description

Leveling device for 3D printers

Related applications

This application claims claims under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 62/191,632, filed on Jul. 13, 2015, the contents of which are incorporated herein by reference in their entirety.

This application is related to multiple U.S. provisional applications that are co-applications, co-applications that are pending, and commonly assigned. One of the U.S. provisional applications is entitled "Methods and Systems for Three-Dimensional Printing" (Attorney Docket No. 63081), filed by Guy Menchik et al. in the United States. A second of the U.S. provisional applications is entitled "Waste Disposal for Three-Dimensional Printing" (Attorney Docket No. 63080), filed by Scott Wayne Beaver et al. in the United States. A third of the U.S. provisional applications is entitled "Operation of a Printing Nozzle in Additive Manufacturing" (Attorney Docket No. 63083), filed by Andrew James Carlson et al. in the United States. This application is also related to a Patent Cooperation Treaty (PCT) patent application entitled "Methods and Systems for Rotary Three-Dimensional Printing" (Attorney Docket No. 62993), filed by Guy Menchik et al. The disclosures of the aforementioned related applications are incorporated herein by reference.

Technical field and background technology

The present invention, in some embodiments thereof, relates to freeform manufacturing, and particularly, but not exclusively, to a leveling apparatus for a freeform manufacturing system.

Additive manufacturing (AM) is generally a process in which a three-dimensional object is manufactured using a computer model of the object. Such processes are used in various fields, such as design-related fields for visualization, display and mechanical prototyping, as well as rapid manufacturing.

The basic operation of any additive manufacturing system consists of slicing a three-dimensional computer model into multiple thin sections, converting the results into two-dimensional bit data, and supplying the data to a controller of the system which builds a three-dimensional structure in a layered manner.

Additive manufacturing involves many different approaches to a manufacturing process, including: 3D printing, such as 3D inkjet printing; laminated object manufacturing; fused deposition modeling; and others.

During a 3D printing process, for example, a build material is dispensed from a dispensing head having a set of nozzles to deposit multiple layers onto a support structure. Depending on the build material, the layers may then be cured or solidified by a suitable device. The build material may include a modeling material, which forms the object, and a support material, which supports the object as it is being built.

During the printing process, the build material is ejected onto the aforementioned multiple layers and accumulates in height. In order to control the height of the three-dimensional object and maintain a level surface, newly ejected and uncured build material passes under a skimmer roller. A portion of the material is removed by the roller and deposited in a collection bath. The roller assembly typically includes: the roller; a scraper; the collection bath; and a suction pump. On longer rollers, multiple suction points are used to locally collect material. Maintenance of the roller bath component is achieved by removing the bath from the assembly.

Various three-dimensional printing technologies exist and are disclosed in, for example, U.S. Patent Nos. 6,259,962, 6,569,373, 6,658,314, 6,850,334, 7,183,335, 7,209,797, 7,225,045, 7,300,619, 7,364,686, 7,500,846, 7,658,976, 7,962,237, and 9,031,680, and U.S. Application Publication No. 20130040091, all of which have the same assignee and are incorporated herein by reference.

For example, U.S. Patent No. 9,031,680 discloses a system comprising: an additive manufacturing apparatus having a plurality of dispensing heads; a build material supply apparatus configured to supply a plurality of build materials to the manufacturing apparatus; and a control unit configured to control the manufacturing and supply apparatus. The system has several operating modes. In one mode, all of the plurality of dispensing heads operate during a single build scan cycle of the manufacturing apparatus. In another mode, one or more of the plurality of dispensing heads do not operate during a single build scan cycle or a portion of a single build scan cycle.

Summary of the Invention

According to one aspect of some embodiments of the present invention, these embodiments provide a drum assembly having a conveying mechanism for conveying debris collected in a bath of the assembly toward a single output. According to some embodiments of the present invention, the conveying mechanism generates pressure for pumping the collected debris out of the assembly and can optionally be used in place of a pump.

According to one aspect of some embodiments of the present invention, these embodiments provide a roller assembly adapted for use with a rotary 3D printing system. According to some embodiments of the present invention, one or more rollers of the assembly are aligned along a radial direction of the rotary 3D printing system. In some exemplary embodiments, the rollers are adapted to skim a layer at a substantially constant linear velocity at multiple different distances from a rotational axis of the printer.

According to one aspect of some embodiments of the present invention, these embodiments of the present invention provide an apparatus comprising: a roller configured to skim off a layer of material deposited by an additive manufacturing (AM) system; a scraper configured to scrape off material accumulated on the roller; a bath configured to collect material scraped off by the scraper; and an auger configured to transport material collected in the bath to a portion of the bath, wherein the portion of the bath extends beyond a length of the roller.

Optionally, the auger extends the entire length of the bath.

Optionally, the auger is mounted in the bath.

Optionally, the auger is engaged with a motor, wherein the motor is configured to rotate the auger along a longitudinal axis of the auger.

Optionally, the scraper extends over the entire length of the drum.

Optionally, a width of the scraper extends from the drum to the auger.

Optionally, the portion of the bath extending beyond the length of the drum comprises a cover configured to enclose the portion of the bath.

Optionally, the bath is configured to create a pressure differential between the portion of the bath extending beyond the length of the drum and a second portion of the bath extending along the length of the drum.

Optionally, the auger comprises a variable pitch thread.

Optionally, a pitch of the auger extending over the length of the drum is wider than the pitch of the auger extending over the portion of the bath.

Optionally, the portion of the bath comprises a backflow channel configured to prevent backflow from being released towards the drum.

Optionally, a housing of the bath comprises: a plurality of wicking channels configured to prevent backflow release towards the drum.

Optionally, the additive manufacturing system is a rotary three-dimensional inkjet printer.

Optionally, the rollers are configured to skim the layer from a rotating build tray.

Optionally, the rollers extend in a radial direction of the rotating building tray.

Optionally, the roller extends in the radial direction over an entire printing area of the tray.

Alternatively, the roller extends in the radial direction over only a portion of the printing area of the tray.

Optionally, the drum is stationary in the radial direction.

Optionally, the roller is mounted on a stage, wherein the stage is configured to move in the radial direction.

Optionally, the apparatus comprises a plurality of rollers, wherein each roller extends in the radial direction over a different portion of the printing area of the tray.

Optionally, each of the plurality of rollers has a different diameter.

Optionally, the drum is a conical drum.

According to one aspect of some embodiments of the present invention, these embodiments of the present invention provide an additive manufacturing system, comprising: a dispensing unit configured to dispense a building material in a layered manner to manufacture an object; a building tray positioned to receive the dispensed building material, wherein the building tray is configured to rotate when the dispensing unit dispenses the building material; and a leveling assembly configured to level the material dispensed on the tray, wherein the leveling assembly comprises: a roller configured to skim off the dispensed building material, wherein the roller is aligned in a radial direction of the building tray; a scraper configured to scrape off material accumulated on the roller; a bath configured to collect material scraped off by the scraper; and an auger configured to transport the material collected in the bath to a portion of the bath, wherein the portion of the bath extends beyond a length of the roller.

Optionally, the auger extends the entire length of the bath and is mounted in the bath.

Optionally, the auger is engaged with a motor, wherein the motor is configured to rotate the auger along a longitudinal axis of the auger.

Optionally, the roller extends in the radial direction over an entire printing area of the tray.

Alternatively, the roller extends in the radial direction over only a portion of the printing area of the tray.

Optionally, the drum is stationary in the radial direction.

Optionally, the roller is mounted on a stage, wherein the stage is configured to move in the radial direction.

Optionally, the apparatus comprises a plurality of rollers, wherein each roller extends in the radial direction over a different portion of the printing area of the tray.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this invention pertains. Although methods and subject matter similar or equivalent to those described herein can be used to implement or test various embodiments of the present invention, exemplary methods and/or exemplary subject matter are described below. In the event of a conflict, the patent specification containing definitions will take precedence. Furthermore, the subject matter, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention are described herein by way of example only with reference to the accompanying drawings. While particular reference will now be made to the drawings in detail, it should be emphasized that the details shown are by way of example only and are for purposes of illustrative discussion of various embodiments of the present invention. In this regard, the description taken in conjunction with the drawings makes it clear to those skilled in the art how various embodiments of the present invention may be practiced.

In the accompanying drawings:

1A to 1D are schematic diagrams of an additive manufacturing system according to some embodiments of the present invention;

2A to 2C are schematic diagrams of multiple print heads according to some embodiments of the present invention;

3A to 3B are schematic diagrams illustrating coordinate transformations according to some embodiments of the present invention;

4A-4B are a perspective view and a front view of an exemplary leveling assembly according to some embodiments of the present invention.

5 is a cross-sectional view cut along a length of an exemplary leveling assembly according to some embodiments of the present invention;

6A and 6B are details of a cross-sectional view cut along a length of an exemplary leveling assembly, and a cross-sectional view cut through a pressure differential region of the exemplary leveling assembly, according to some embodiments of the present invention;

FIG6C is a cross-sectional view of a housing of the collection bath according to some embodiments of the present invention;

7A and 7B are two exemplary cross-sectional views cut along a length of an auger according to some embodiments of the present invention;

8A, 8B, and 8C are schematic diagrams of leveling assemblies covering a printing area according to some embodiments of the present invention; and

9 is a schematic side view of a conical roller above a build tray according to some embodiments of the present invention.

DETAILED DESCRIPTION

The present invention, in some embodiments thereof, relates to freeform manufacturing, and particularly, but not exclusively, to a leveling apparatus for a freeform manufacturing system.

According to some embodiments of the present invention, a roller assembly is provided, comprising: a scraper for scraping material off the roller; and an auger for removing material skimmed off the roller from the scraper and transporting the material scraped from the roller to an area, such as one end of the roller. According to some embodiments of the present invention, the auger cleans the bath and reduces the number of maintenance intervals required to clean the roller. The single output from which the residue is collected eliminates the need for a zone selector valve switch, which is typically used to control multiple suction points.

According to some embodiments of the present invention, the auger of the drum assembly is designed to generate pressure for pumping the collected build material out of the assembly. A combination of a conveying mechanism and a volumetric pumping action can be used to eliminate the suction pump typically used to remove the debris from the bath.

According to some embodiments of the present invention, the roller is integrated into a rotary 3D printing system and is adapted to level the build material as the system rotates. Typically, the roller is rotated by a motor about a longitudinal axis of the roller.

According to some embodiments of the present invention, the roller is defined to have a length that extends along an entire radial printing area, such as all of the plurality of printing paths of the rotary 3D printer. In some other embodiments of the present invention, the roller assembly includes a roller that extends only along one or more paths (but less than all of the plurality of paths) of the rotary 3D printer. The entire radial printing area is covered by axially mounting the roller on a movable stage that moves in the radial direction.

In some other embodiments of the present invention, the roller assembly includes a plurality of rollers, for example, located at a plurality of different positions along the radial direction.

Optionally, when multiple rollers are used, multiple large-diameter rollers are used to level multiple passes farther from a rotational axis, and multiple small-diameter rollers are used to level multiple passes closer to the rotational axis, so that when the multiple rollers skim a layer of dispensed material, the linear velocity of the multiple rollers is substantially the same at multiple different distances from the rotational axis. In some exemplary embodiments, the rollers are defined to have a conical shape that tapers toward a center of the print zone. A taper angle is typically selected to provide the same linear velocity at multiple different distances from the rotational axis of the print zone. Alternatively, a cylindrical roller may be used.

Before explaining at least one embodiment of the present invention in detail, it should be understood that the present invention is not necessarily limited in its application to the details and arrangements of the multiple components and/or methods described in the following description and/or shown in the accompanying drawings. The present invention is capable of many other embodiments or can be implemented or carried out in various ways.

The methods and systems of various embodiments of the present invention fabricate a plurality of three-dimensional objects in a layered manner based on computer object data by forming multiple layers in a configured pattern corresponding to the shapes of the plurality of objects. The computer object data may be in any known format, including, but not limited to, Standard Tessellation Language (STL) or Solid Colour (SLC) formats, Virtual Reality Modeling Language (VRML), Additive Manufacturing File (AMF) format, Drawing Interchange Format (DXF), Polygon File Format (PLY), or any other format suitable for computer-aided design (CAD).

As used herein, the term "object" refers to an entire object, or a portion thereof.

Each layer is formed by an additive manufacturing device that scans and patterns a two-dimensional surface. While scanning, the device visits multiple target locations on the two-dimensional layer or surface and, for each target location or group of target locations, determines whether the target location or group of target locations will be occupied by build material and what type of build material will be delivered to the target location or group of target locations. This determination is made based on a computer image of the surface.

According to preferred embodiments of the present invention, the additive manufacturing comprises three-dimensional printing, more preferably three-dimensional inkjet printing. In these embodiments, a building material is dispensed from a dispensing head having a set of nozzles to deposit the building material in layers on a support structure. The additive manufacturing apparatus thus dispenses the building material into a plurality of target positions to be occupied, while leaving a plurality of other positions empty. The apparatus typically comprises a plurality of dispensing heads, each of which can be configured to dispense a different building material. Thus, a plurality of different target positions can be occupied by a plurality of different building materials. The plurality of types of building materials can be categorized into two main groups: molding materials and support materials. The support material serves as a supporting substrate or structure for supporting the object or parts of the objects during the manufacturing process, and/or for a plurality of other purposes, such as providing a plurality of hollow or porous objects. The plurality of support structures may additionally comprise a plurality of molding material elements, for example for further support strength.

The molding material is generally a composition formulated for use in additive manufacturing that is capable of forming a three-dimensional object on its own, ie, without having to be mixed or combined with any other substances.

The final three-dimensional object is made of the molding material, or a combination of multiple molding materials, or a combination of multiple molding materials and support materials, or modifications of the aforementioned materials (e.g., after curing). All of these operations are well known to those skilled in the art of solid freeform fabrication.

In some exemplary embodiments of the present invention, an object is manufactured by dispensing two or more different build materials, each material from a different dispensing head of the additive manufacturing system. The multiple materials are selectively and preferably deposited in layers during the same pass of the multiple print heads. The multiple materials and combinations of materials in the layers are selected based on the desired properties of the object.

According to some embodiments of the present invention, a representative and non-limiting example of a system 110 suitable for additively manufacturing an object 112 is illustrated in FIG1A . System 110 includes an additive manufacturing apparatus 114 having a dispensing unit 16 comprising a plurality of dispensing heads. As illustrated in FIG2A through 2C described below, each dispensing head preferably includes an array of one or more nozzles 122 through which a liquid build material 124 is dispensed. Optionally, the build material is a polymeric material, such as a photopolymer. Other materials may also be used.

Preferably, but not necessarily, the device 114 is a 3D droplet deposition device, such as an inkjet printing device. In this case, the multiple dispensing heads are multiple print heads, and the build material is preferably dispensed using inkjet technology. This is not a requirement, as for some applications, it may not be necessary for the additive manufacturing device to utilize multiple 3D inkjet technologies. Representative examples of additive manufacturing devices contemplated according to various exemplary embodiments of the present invention include, but are not limited to, a fused deposition modeling device and a molten material deposition device.

Each dispensing head is selectively and preferably fed by a build material reservoir, which optionally includes: a temperature control unit (e.g., a temperature sensor and/or a heating device); and a material level sensor. To dispense the build material, for example, in piezoelectric inkjet printing technology, a voltage signal is applied to the plurality of dispensing heads to selectively deposit droplets of material through the plurality of dispensing head nozzles. A dispensing rate for each dispensing head depends on the number of nozzles, the type of nozzles, and the rate (frequency) of the applied voltage signal. Such dispensing heads are known to those skilled in the art of solid freeform fabrication.

Preferably, but not necessarily, the total number of the plurality of dispensing nozzles or nozzle arrays is selected so that half of the plurality of dispensing nozzles are designated for dispensing the support material and half of the plurality of dispensing nozzles are designated for dispensing the molding material. That is, the number of nozzles ejecting multiple molding materials is the same as the number of nozzles ejecting the support material. In the representative example of FIG1A , four dispensing heads 16a, 16b, 16c, and 16d are depicted. Each of dispensing heads 16a, 16b, 16c, and 16d has a nozzle array. In this example, dispensing heads 16a and 16b can be designated for multiple molding materials, and dispensing heads 16c and 16d can be designated for the support material. Thus, dispensing head 16a can dispense a first molding material, dispensing head 16b can dispense a second molding material, and dispensing heads 16c and 16d can both dispense the support material. In an alternative embodiment, dispensing heads 16c and 16d can be combined into a single dispensing head having two nozzle arrays for depositing the support material.

However, it should be understood that this is not intended to limit the scope of the present invention, and the number of multiple molding material deposition heads (multiple molding heads) and the number of multiple support material deposition heads (multiple support heads) may vary. Generally speaking, the number of multiple molding heads, the number of multiple support heads, and the number of multiple nozzles in each respective dispensing head or dispensing head array are selected to provide a predetermined ratio a, which is the ratio between a maximum dispensing rate of the support material and a maximum dispensing rate of the molding material. A value for the predetermined ratio a is preferably selected to ensure that, in each formed layer, a height of the molding material in the layer is equal to a height of the support material in the same layer. Typical values of a are about 0.6 to about 1.5.

As used herein, the term "about" refers to ±10%.

For example, for a=1, when all of the plurality of forming heads and the plurality of supporting heads are operating, a total distribution rate of the supporting material is generally the same as a total distribution rate of the forming material.

In a preferred embodiment, there are M forming heads and S support heads, each of the M forming heads having m arrays of p nozzles, and each of the S support heads having s arrays of q nozzles, such that M×m×p=S×s×q. Each of the M×m forming arrays and S×s support arrays can be manufactured as a separate physical unit that can be assembled with or disassembled from the set of arrays. In this embodiment, each such array can optionally and preferably include its own temperature control unit and material level sensor, and receive a separate control voltage for operation of the array.

Apparatus 114 may further include a hardening device 324, which may include any device configured to emit light, heat, or the like to cause the deposited material to harden. For example, hardening device 324 may include one or more radiation sources, depending on the molding material used, such as an ultraviolet, visible, or infrared lamp, or other electromagnetic radiation sources, or an electron beam source. In some embodiments, hardening device 324 is used to cure or solidify the molding material.

In some exemplary embodiments, the dispensing heads and radiation sources are preferably mounted on a frame or block 128, which is preferably operable to reciprocate over a tray and/or print platen 360, which serves as a work surface. In some embodiments of the present invention, the plurality of radiation sources are mounted within the block so that the plurality of radiation sources follow the plurality of dispensing heads to at least partially cure or solidify the plurality of materials just dispensed by the plurality of dispensing heads. Tray 360 is positioned horizontally. By convention, an X-Y-Z Cartesian coordinate system is selected so that an X-Y plane is parallel to tray 360. Tray 360 is preferably configured to move vertically (in a Z direction), typically downward. In various exemplary embodiments of the present invention, apparatus 114 further includes one or more leveling devices 132, such as a roller 326. The leveling device 326 is used to straighten, level, and/or establish the thickness of a newly formed layer before a subsequent layer is formed on the newly formed layer. The leveling device 326 preferably includes a waste collection device 136 for collecting excess material generated during leveling. The waste collection device 136 can include any mechanism that directs the material to a waste bin or waste box.

In some exemplary embodiments, the dispensing heads of unit 16 move along a scanning direction, referred to herein as an X-direction, and selectively dispense build material in a predetermined configuration as they pass over tray 360. The build material typically comprises one or more support materials and one or more build materials. Following the passage of the dispensing heads of unit 16, radiation source 126 solidifies the build material(s). As the dispensing heads pass back to the starting point of the layer they just deposited, additional dispenses of build material can be performed according to the predetermined configuration. As the dispensing heads pass forward and/or backward, the layers formed thereby can be straightened by leveling device 326, which preferably follows the path of the forward and/or backward motion of the dispensing heads. Once the dispensing heads have returned to their starting point along the X-direction, they can be moved to another position along a directional direction, referred to herein as the Y-direction, and continue to build the same layer along the X-direction through reciprocating motion. Alternatively, the dispensing heads can be moved along the Y-direction between multiple forward and backward motions or after more than one forward and backward motion. A series of scans performed by the dispensing heads to complete a single layer is referred to herein as a single scan cycle.

Once the layer is completed, the tray 360 is lowered along the Z direction to a predetermined Z level, depending on the desired thickness of the layer to be printed subsequently. This process is repeated to form the three-dimensional object 112 in a layered manner.

In another embodiment, the tray 360 can be displaced in the Z direction between forward and backward passes of the dispensing head of the unit 16 within the layer. Such Z displacement is intended to cause the leveling device to contact the surface in one direction while preventing the leveling device from contacting the surface in another direction.

The system 110 may optionally and preferably include a building material supply system 330 , which includes a plurality of building material containers or cartridges and supplies a plurality of building materials to the additive manufacturing apparatus 114 .

A control unit 340 controls the apparatus 114 and, optionally and preferably, also controls the supply system 330. Control unit 340 typically includes electronic circuitry configured to perform the control operations. Control unit 340 preferably communicates with a processor 154, which transmits digital data relating to manufacturing instructions based on computer object data, such as a CAD configuration represented on a computer-readable medium in an STL format. Typically, processor 154 includes a memory unit and/or storage capacity for storing the computer object data and data relating to manufacturing instructions based on the computer object data. Control unit 340 typically controls the voltage applied to each dispensing head or nozzle array, as well as the temperature of the build material in the respective print head.

Once the manufacturing data is loaded into control unit 340, it can operate without user intervention. In some embodiments, control unit 340 receives additional input from an operator using, for example, data processor 154 or a user interface 116 in communication with control unit 340. User interface 116 can be of any type known in the art, such as, but not limited to, a keyboard, a touch screen, etc. For example, control unit 340 can receive as additional input the type and/or properties of one or more build materials, such as, but not limited to, property distortion and/or transition temperature, viscosity, electrical properties, or magnetic properties. Multiple other properties and sets of properties are also contemplated.

Another representative and non-limiting example of a rotary system 10 suitable for additive manufacturing an object according to some embodiments of the present invention is illustrated in Figures 1B to D. Figures 1B to D illustrate a top view (Figure 1B), a side view (Figure 1C), and an isometric view (Figure 1D) of the system 10.

In various embodiments, system 10 includes a tray and/or print platen 12 and a plurality of inkjet print heads 16, each of which has a plurality of separate nozzles. Tray 12 can have a circular disk shape or a ring shape. Non-circular shapes are also contemplated as long as they can rotate about a vertical axis. Typically, system 10 also includes one or more radiation sources 18 and one or more leveling devices 32.

The tray 12 and the plurality of print heads 16 can optionally and preferably be mounted to allow relative rotational movement between the tray 12 and the plurality of print heads 16. This relative rotational movement can be achieved by: (i) configuring the tray 12 to rotate about a vertical axis 14 relative to the plurality of print heads 16, (ii) configuring the plurality of print heads 16 to rotate about the vertical axis 14 relative to the tray 12, or (iii) configuring both the tray 12 and the plurality of print heads 16 to rotate about the vertical axis 14, but at different rotational speeds (e.g., rotating in opposite directions). Although the following embodiments are described with particular emphasis on configuration (i), in which the tray is a rotating disk configured to rotate about the vertical axis 14 relative to the plurality of print heads 16, it should be understood that the present invention also contemplates configurations (ii) and (iii). Any of the embodiments described herein can be adapted for use with either configuration (ii) or (iii), and one of ordinary skill in the art would understand how to make such adjustments based on the details described herein.

In the following description, a direction parallel to the tray 12 and pointing outward from the axis 14 is referred to as a radial direction r, a direction parallel to the tray 12 and perpendicular to the radial direction r is referred to herein as an azimuthal direction, and a direction perpendicular to the tray 12 is referred to herein as a vertical direction z.

As used herein, the term "radial position" refers to a position on or above the tray 12 that is a specified distance from the axis 14. When the term is used in relation to a print head, the term refers to a position of the print head that is a specified distance from the axis 14. When the term is used in relation to a point on the tray 12, the term corresponds to any point belonging to a locus of points, the locus of points being a circle having a radius the specified distance from the axis 14 and having its center at the axis 14.

As used herein, the term "azimuthal position" refers to a position on or above the tray 12 at a particular azimuthal angle relative to a predetermined reference point. Thus, a radial position refers to any point belonging to a trajectory of a plurality of points that form a straight line at the particular azimuthal angle relative to the reference point.

As used herein, the term “vertical position” refers to a position above a plane that intersects the vertical axis 14 at a specific point.

Tray 12 serves as a support structure for three-dimensional printing. A working area on which one or more objects are printed is typically, but not necessarily, smaller than the total area of tray 12. In some embodiments of the present invention, the working area is annular. The working area is shown at 26. In some embodiments of the present invention, tray 12 rotates continuously in the same direction throughout the object formation process, and in some embodiments of the present invention, the tray rotates in the opposite direction (e.g., in an oscillating manner) at least once during the object formation process. Tray 12 is optionally and preferably removable. Removal of tray 12 can be necessary for maintenance of system 10 or, if necessary, to replace the tray before printing a new object. In some embodiments of the present invention, system 10 is provided with one or more different replacement trays (e.g., a set of replacement trays), wherein two or more trays are designated for various types of objects (e.g., various weights), various operating modes (e.g., various rotation rates), etc. Tray 12 can be replaced manually or automatically as needed. When automatic replacement is employed, the system 10 includes a tray changer 36 configured to remove the tray 12 from its position beneath the print heads 16 and replace the tray 12 with a replacement tray (not shown). In the representative diagram of FIG1B , the tray changer 36 is depicted as a drive 38 having a movable arm 40 configured to pull the tray 12. However, various other types of tray changers are also contemplated.

2A-2C , which may be used with any of the aforementioned additive manufacturing systems, including but not limited to system 110 and system 10 .

2A-B illustrate a printhead 16 having one ( FIG. 2A ) and two ( FIG. 2B ) nozzle arrays 22. The nozzles in the arrays are preferably aligned linearly along a straight line. In embodiments where a particular printhead has two or more linear nozzle arrays, the nozzle arrays may optionally and preferably be parallel to one another.

When a system similar to system 110 is employed, all of the plurality of print heads 16 are selectively and preferably oriented along the pointing direction, wherein the plurality of positions of the plurality of print heads 16 are offset from one another along the scanning direction.

When a system similar to system 10 is employed, all of the plurality of print heads 16 are optionally and preferably oriented radially (parallel to the radial direction), wherein the plurality of azimuthal positions of the plurality of print heads 16 are offset from one another. Thus, in these embodiments, the plurality of nozzle arrays of the plurality of different print heads are not parallel to one another, but are angled relative to one another, the angle being approximately equal to the azimuthal offset between the plurality of respective print heads. For example, one print head may be radially oriented and located at an azimuthal position, and another print head may be radially oriented and located at an azimuthal position. For example, the azimuthal offset between the two print heads is and the angle between the plurality of linear nozzle arrays of the two print heads is also

In some embodiments, two or more printheads may be assembled into a set of printheads, in which case the printheads in the set are generally parallel to each other. A set of printheads including a plurality of inkjet printheads 16a, 16b, 16c is shown in FIG2C.

In some embodiments, the system 10 includes a support structure 30 positioned beneath the printheads 16 such that the tray 12 is positioned between the support structure 30 and the printheads 16. The support structure 30 can be used to prevent or reduce vibrations that may occur in the tray 12 when the inkjet printheads 16 are in operation. In configurations where the printheads 16 rotate about the axis 14, the support structure 30 preferably also rotates such that the support structure 30 is always directly beneath the printheads 16 (with the tray 12 positioned between the printheads 16 and the tray 12).

The tray 12 and/or the plurality of print heads 16 are optionally and preferably configured to move in the vertical direction z, which is parallel to the vertical axis 14, to change a vertical distance between the tray 12 and the plurality of print heads 16. In configurations where the vertical distance is changed by moving the tray 12 in the vertical direction, the support structure 30 preferably also moves vertically with the tray 12. In configurations where the vertical distance is changed by the plurality of print heads 16 in the vertical direction, the support structure 30 is maintained in a fixed vertical position while maintaining a fixed vertical position of the tray 12.

The vertical motion can be established by a vertical drive 28. Once a layer is completed, the vertical distance between the tray 12 and the plurality of print heads 16 can be increased by a predetermined vertical step (e.g., the tray 12 is lowered relative to the plurality of print heads 16) according to a desired thickness of the next layer to be printed. This process is repeated to form a three-dimensional object in a layered manner.

The operation of the plurality of inkjet print heads 16 and optionally and preferably one or more other components of the system 10 (e.g., the movement of the tray 12) is controlled by a controller 20. The controller may include an electronic circuit and a non-volatile storage medium readable by the circuit, wherein the storage medium stores a plurality of program instructions that, when read by the circuit, cause the circuit to perform a plurality of control operations described in further detail below.

The controller 20 may also communicate with a host computer 24 that transmits digital data regarding a plurality of manufacturing instructions based on computer object data, such as the Standard Tessellation Language (STL) or a Solid Cutout (SLC) format, Virtual Reality Modeling Language (VRML), Additive Manufacturing File (AMF) format, Drawing Exchange Format (DXF), Polygon File Format (PLY), or any other format suitable for computer-aided design (CAD). The computer object data are typically organized according to a Cartesian coordinate system.

In these cases, the computer 24 preferably executes a program for transforming the coordinates of each slice in the computer object data from a Cartesian coordinate system to a polar coordinate system. The computer 24 optionally and preferably transmits the manufacturing instructions expressed in accordance with the transformed coordinate system. Alternatively, the computer 24 may transmit the manufacturing instructions provided by the computer object data expressed in accordance with the original coordinate system, in which case the transformation of the coordinates is performed by the circuitry of the controller 20.

The transformation of the multiple coordinates allows three-dimensional printing above a rotating tray. In conventional three-dimensional printing, the multiple print heads move back and forth along multiple lines above a stationary tray. In such conventional systems, as long as the multiple distribution rates of the multiple print heads are consistent, the printing resolution at any point above the tray is the same. Unlike conventional three-dimensional printing, not all of the multiple nozzles of the multiple print head points cover the same distance above the tray 12 at the same time. The transformation of the multiple coordinates can be optionally and preferably performed to ensure that there is an equal amount of excess material at multiple different radial positions. Representative examples of multiple coordinate transformations of computer object data according to some embodiments of the present invention are provided in Figures 3A and 3B, which show a slice of an object, wherein Figure 3A shows a slice presented in a Cartesian coordinate system and Figure 3B shows the same slice after a process of applying a multiple coordinate transformation to the respective slices.

Generally, controller 20 controls a voltage applied to the respective components of the system 10 based on the manufacturing instructions and based on stored program instructions as described below.

Generally speaking, the controller 20 controls the plurality of print heads 16 to dispense a plurality of droplets of building material in layers when the tray 12 rotates, so as to print a three-dimensional object on the tray 12 .

System 10 optionally and preferably includes one or more radiation sources 18, which may be, depending on the molding material being used, such as an ultraviolet, visible, or infrared lamp, or other electromagnetic radiation sources, or an electron beam source. Radiation sources may include any type of radiation-emitting device, including, but not limited to, light-emitting diodes (LEDs), digital light processing (DLP) systems, resistance lamps, and the like. Radiation sources 18 are used to cure or solidify the molding material. In various exemplary embodiments of the present invention, the operation of radiation sources 18 is controlled by a controller 20, which can activate and deactivate radiation sources 18 and optionally also control the amount of radiation generated by radiation sources 18.

In some embodiments of the present invention, system 10 further includes one or more leveling devices 32, which can be implemented as a roller or a scraper. Leveling device 32 is used to straighten a newly formed layer before a subsequent layer is formed on top of it. In some embodiments, leveling device 32 has the form of a conical roller, positioned such that its axis of symmetry 34 is inclined relative to a surface of pallet 12, while a surface of the roller is parallel to the surface of the pallet. This embodiment is illustrated in a side view of system 10 ( FIG. 1C ).

The conical roller may have a shape of a cone or a frustum of a cone.

The angle of the conical roller is preferably selected so that the ratio between the radius of the cone at any location along the axis 34 of the roller and the distance between that location and the axis 14 is a constant ratio. This embodiment allows the roller 32 to effectively level the multiple layers because, as the roller rotates, any point p on the surface of the roller has a linear velocity that is proportional to (e.g., the same as) the linear velocity of the tray at a point perpendicularly below point p. In some embodiments, the roller has the shape of a frustum of a cone having a height h, a radius R ₁ at the closest distance of the frustum from the axis 14, and a radius R ₂ at the farthest distance of the frustum from the axis 14, where the parameters h, R ₁ , and R ₂ satisfy the relationship: R ₁ /R ₂ = (Rh)/h, where R is the farthest distance of the roller from the axis 14 (e.g., R can be the radius of the tray 12).

The operation of the leveling device 32 is optionally and preferably controlled by the controller 20, which can activate and deactivate the leveling device 32 and optionally also control a position of the leveling device 32 along a vertical direction (parallel to the axis 14) and/or a radial direction (parallel to the tray 12 and pointing toward or away from the axis 14).

In some embodiments of the present invention, the print heads 16 are configured to reciprocate relative to the tray in the radial direction r. These embodiments are applicable when the lengths of the nozzle arrays 22 of the print heads 16 are less than the width of the working area 26 on the tray 12 in the radial direction. The movement of the print heads 16 in the radial direction is optionally and preferably controlled by the controller 20.

Some embodiments contemplate fabricating an object by dispensing a plurality of different materials from a plurality of different dispensing heads. These embodiments provide, inter alia, the ability to select a plurality of materials from a given number of material types and to define a plurality of desired combinations of the selected materials and their properties. According to various embodiments, the plurality of spatial locations at which each material is deposited with a layer are defined to achieve the plurality of different materials occupying a plurality of different three-dimensional spatial locations, or to achieve the plurality of different materials occupying a substantially identical three-dimensional location or a plurality of adjacent three-dimensional locations, thereby allowing post-deposition spatial combination of the plurality of materials in the layer to thereby form a composite material at the respective location or locations.

Any post-deposition combination or blend of multiple build materials is contemplated. For example, once a material is dispensed, it may retain many of its original properties. However, when the material is dispensed simultaneously with another build material or multiple other dispensed materials dispensed at the same location or at adjacent locations, a composite material is formed that has a different property or properties than the dispensed material.

Multiple present embodiments therefore make it possible to deposit a wide range of material combinations and to manufacture an object that can be composed of multiple different combinations of materials, wherein the multiple different combinations of materials of the object are in multiple different parts of the object based on the multiple properties required to characterize each part of the object.

Further details of the principles and operations of an additive manufacturing system applicable to embodiments of the present invention may be found in US Pat. No. 9,031,680, the contents of which are incorporated herein by reference.

Reference is now made to Figures 4A-4B, which show a perspective view and a front view of an exemplary leveling assembly according to some embodiments of the present invention. According to some embodiments of the present invention, the leveling assembly 100 includes a roller 110, a scraper 130, a collection bath 120, and an auger 150. The roller 110 skims a surface of a layer deposited to construct a three-dimensional object, where the build material is accumulated on the roller 110. The scraper 130 typically extends along the entire length of the roller 110 and scrapes the material from the roller 110. The material scraped off by the scraper 130 is typically collected in the bath 120. According to some embodiments of the present invention, the bath 120 extends along the entire length of the roller 110 and also extends a defined distance beyond the roller 110. According to some embodiments of the present invention, an auger 150 is positioned within the bath 120 and extends along the entire length of the bath 120. The auger 150, when rotated, moves all material within the bath 120 in a direction (e.g., direction 115). According to some embodiments of the present invention, the auger 150 is rotated by a motor that is included in the leveling assembly.

According to some embodiments of the present invention, when one end of the scraper 130 is pressed against the drum 110, an opposite end of the scraper 130 is substantially in contact with the auger 150. This allows the auger 150 to clean substantially all of the material that the scraper 130 has collected from the drum 110. In some exemplary embodiments, the scraper 130 extends to a bottom of the bath 120 to provide a seamless surface between the drum 110, the scraper 130, and the auger 150 so that material does not collect between the scraper 130 and the bath 120. Alternatively, the scraper 130 is similar to the scrapers described, for example, in U.S. Patent No. 7,500,846, the contents of which are incorporated herein by reference.

Reference is now made to FIG5 , which shows a cross-sectional view taken along the length of an exemplary leveling assembly, according to some embodiments of the present invention. Typically, the auger 150 is longer than the drum 110, such that the auger 150 overlaps the entire length of the drum 110 and also extends beyond the drum 110 in direction 115 . Along the length of the drum 110, the bath 120 is open to allow material 250 scraped from the drum 110 to enter the bath 120. Within the bath 120, the material 250 typically accumulates between the threads 153 of the auger 150 and is mechanically transported in direction 115 by the rotation of the auger 150. According to some embodiments of the present invention, the auger 150 transports the material 250 toward a pumping chamber region 280, where it is removed from the bath 120 through a valve 290. In some exemplary embodiments, region 280 of the bath 120 is sealed to generate pressure. Typically, a pressure differential is established at an interface 220 between the enclosed pump chamber area 280 and an open area extending along a length of the drum 110. In some exemplary embodiments, a peristaltic pump 295 actively removes material 250 from the bath 120.

Reference is now made to Figures 6A and 6B, which show details of a cross-sectional view taken along the length of an exemplary leveling assembly and a cross-sectional view taken at a pressure differential interface, respectively, according to some embodiments of the present invention. Along the length of the auger 150, the pressure differential region 220 can cause material 250 to flow back from region 280 through any interface open to nominal pressure. According to some embodiments of the present invention, a backflow channel 320 prevents backflow from being released near the drum 110 and outside the bath 120. This controlled release point directs the backflow to a safe area of the bath 120 and reduces the possibility of leakage. In some exemplary embodiments, the backflow channel 320 also includes a filler space 260 located along the auger 150 and below a front level 300 of the bath 120. Optionally, the filler space 260 increases the volume of the bath 120 to prevent leakage.

Reference is now made to Figure 6C, which shows a cross-sectional view of a shell of the collection bath according to some embodiments of the present invention. In some exemplary embodiments, multiple wicking channels 325 are introduced along a length of the shell (or cover) 125 of the collection bath 120 as a replacement for the return channels 300. Optionally, the multiple wicking channels are provided in addition to the multiple return channels 300. The wicking channels 325 can remove resin from multiple leak points by capturing the resin on the auger. This prevents the resin from moving toward an opening on a drum side of the shell 125.

7A and 7B , which show two exemplary cross-sectional views of a length cut along an auger according to some embodiments of the present invention. According to some embodiments of the present invention, the auger 150 has a variable pitch thread. In some exemplary embodiments, a wider pitch of the thread 153 along a length of the drum 110 is used to quickly transport material, while a tighter pitch of the thread 153 is used in the area 280 to generate greater pressure. Alternatively, an auger 151 has a constant pitch over its entire length. Typically, the auger 150 is rotated by a motor, which is optionally connected to the auger 150 with a pulley and/or a timing belt.

Reference is now made to Figures 8A, 8B, and 8C, which illustrate schematic diagrams of leveling assemblies covering a print zone, according to some embodiments of the present invention. Referring to Figure 8A, a build tray 400 for a rotary 3D printer, according to some embodiments of the present invention, includes a print zone 405 and a non-print zone 410. Typically, the non-print zone is a central portion of the tray 400. According to some embodiments of the present invention, a length of the roller 110 extends along the entire radial distance of the print zone 405, such that a single roller covers all of the multiple print paths (Figure 8A). Typically, the roller 110 is stationary in the radial direction and is rotated by a motor along a longitudinal axis of the roller 110.

8B, in other exemplary embodiments, a roller 105 is used that covers less than the radial distance of the print area 405 and is movable in the radial direction. Typically, the roller 105 advances in a radial direction to match the location where the material is dispensed.

Referring to FIG8C , in other embodiments of the present invention, more than one roller is used to cover the print area. Optionally, a roller 107 located closer to the center of the tray 400 is selected to have a smaller diameter than a roller 106 located farther from the center. In rotary printing, the relative speed of the rollers relative to the tray 400 depends on radial position. Variations in these relative speeds depend on the size of the tray 400 and can affect component quality and overall functionality of the machine. In some exemplary embodiments, the different diameters are selected to compensate for variations in relative speeds.

Reference is now made to Figure 9, which shows a schematic side view of a conical roller above a build tray according to some embodiments of the present invention. According to some embodiments of the present invention, a roller 111 having a conical shape is used to level the material dispensed above the tray 400 during additive manufacturing. According to some embodiments of the present invention, the conical shape compensates for changes in the relative speed of the roller relative to the tray 400. Generally, a diameter of the cone increases with increasing distance from a center of the tray 400. In alternative embodiments of the present invention, a cylindrical roller extending over an entire print area of the tray 400 is sufficient to produce high print quality. In other embodiments of the present invention, more than one conical roller is used to cover the print area of the tray 400.

It will be understood that specific features of the present invention, which for clarity are described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the present invention, which for brevity are described in the context of a single embodiment, may also be provided separately, in any suitable subcombination, or in any other described embodiment applicable to the present invention. Specific features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiments would not function without those elements.

Claims (30)

1. A device, characterized in that: the device comprises: A roller is configured to skim off a layer of material deposited by an additive manufacturing (AM) system; A scraper is configured to scrape off the material accumulated on the roller; A bath is configured to collect the material scraped off by the scraper; and A spiral drill is configured to transport the material collected in the bath to a portion of the bath, wherein the portion of the bath extends beyond a length of the drum. One end of the scraper presses against the roller, and the opposite end of the scraper is in almost contact with the auger. 2. The device as claimed in claim 1, wherein the auger extends over the entire length of the bath. 3. The device as claimed in claim 1, wherein the auger is mounted in the bath and the auger is engaged with a motor, wherein the motor is configured to rotate the auger along a longitudinal axis of the auger. 4. The device as claimed in claim 1, wherein the scraper is configured to provide a seamless surface between the roller and the auger. 5. The device as claimed in any one of claims 1 to 4, wherein the scraper extends over the entire length of the roller. 6. The device as claimed in any one of claims 1 to 4, wherein a width of the scraper extends from the roller to the auger. 7. The device as claimed in any one of claims 1 to 4, wherein the portion of the bathtub extending beyond the length of the roller comprises: a cover configured to close the portion of the bathtub. 8. The device of claim 7, wherein the bath is configured to form a pressure difference between a portion of the bath extending beyond the length of the roller and a second portion of the bath, wherein the second portion of the bath extends along the length of the roller. 9. The device as claimed in any one of claims 1 to 4, wherein the auger comprises a variable pitch thread. 10. The apparatus of claim 9, wherein a pitch of the auger extending along the length of the drum is wider than the pitch of the auger extending along the portion of the bath. 11. The device as claimed in any one of claims 1 to 4, wherein the portion of the bath includes a return channel configured to prevent backflow towards the roller. 12. The device as claimed in any one of claims 1 to 4, wherein a housing of the bath includes a plurality of wicking channels configured to prevent backflow toward the roller. 13. The device according to any one of claims 1 to 4, wherein the additive manufacturing system is a rotary three-dimensional inkjet printer. 14. The apparatus of claim 13, wherein the roller is configured to remove the layer from a rotating build tray. 15. The apparatus of claim 13, wherein the roller extends along a radial direction of the rotating construction tray. 16. The apparatus of claim 15, wherein the roller extends in the radial direction over an entire printing area of the tray. 17. The apparatus of claim 15, wherein the roller extends only in the radial direction over a portion of the printing area of the tray. 18. The device as claimed in claim 16, wherein the roller is stationary along the radial direction. 19. The apparatus of claim 17, wherein the roller is mounted on a platform, wherein the platform is configured to move along the radial direction. 20. The apparatus of claim 17, wherein the apparatus comprises a plurality of rollers, wherein each roller extends in the radial direction over a different portion of the printing area of the tray. 21. The apparatus of claim 20, wherein each of the plurality of rollers has a different diameter. 22. The device as described in claim 13, wherein the roller is a conical roller. 23. An additive manufacturing system, characterized in that: the additive manufacturing system comprises: A distribution unit is configured to distribute building materials in a layered manner to manufacture an object; A build tray, positioned to receive the dispensed build material, wherein the build tray is configured to rotate as the dispensing unit dispenses the build material; and A leveling assembly configured to level the material dispensed onto the tray, wherein the leveling assembly comprises: A roller is configured to skim off the dispensed building material, wherein the roller is aligned along a radial direction of the building tray; A scraper is configured to scrape off the material accumulated on the roller; A bath is configured to collect the material scraped off by the scraper; and A auger is configured to transport material collected in the bath to a portion of the bath, wherein the portion of the bath extends beyond a length of the drum, wherein one end of a scraper presses against the drum, and an opposite end of the scraper is in near contact with the auger. 24. The device as claimed in claim 23, wherein the auger extends over the entire length of the bath and is installed in the bath. 25. The device of claim 23, wherein the auger is coupled to a motor, wherein the motor is configured to rotate the auger along a longitudinal axis of the auger. 26. The apparatus according to any one of claims 23 to 25, wherein the roller extends in the radial direction over an entire printing area of the tray. 27. The device as claimed in any one of claims 23 to 25, wherein the roller extends in the radial direction only over a portion of a printing area of the tray. 28. The device as claimed in claim 26, wherein the roller is stationary along the radial direction. 29. The apparatus of claim 27, wherein the roller is mounted on a platform, wherein the platform is configured to move along the radial direction. 30. The apparatus of claim 27, wherein the apparatus comprises a plurality of rollers, wherein each roller extends in the radial direction over a different portion of the printing area of the tray.