Bridging internal channels in 3D printed objects

Abstract

A method for printing an internal bridge within a three-dimensional object includes the steps of: depositing a plurality of droplets of printing material in a first direction to form a supported step-out at the edge of a bridge layer; depositing a plurality of droplets of printing material to form an anchor layer adjacent to and in contact with the supported step-out; and depositing a plurality of droplets of printing material to form an unsupported step-out adjacent to and in contact with the supported step-out. A printing system for a three-dimensional object configured to perform the method for printing an internal bridge within a three-dimensional object is also described.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims priority to U.S. Patent Application No. 18 / 233134, filed on 11 August 2023, the contents of which are incorporated herein by reference in their entirety.

[0002] This instruction outlines a system and method for printing bridges on internal channels within a 3D part using three-dimensional (3D) printing, and more specifically, a 3D printer. [Background technology]

[0003] 3D printing involves ejecting liquid build material through an ejector. Multiple droplets of the liquid build material are ejected from the nozzle of the ejector. The droplets fall onto the build plate, where they cool and solidify to form a 3D part. It is often desirable to print channels within the 3D part. Conventionally, the maximum bridging distance (and thus the maximum channel width) without supports is approximately 1.75 mm. More specifically, two supports may be spaced 1.75 mm apart, and seven 0.25 mm bridging lines (also called overhang segments or unsupported step-outs) may be printed in the XY plane to bridge the distance between them. This corresponds to one or more bridge lines (e.g., 0.875 mm) being printed from the first pillar to the second pillar, and one or more bridge lines (e.g., 0.875 mm) being printed from the second pillar to the first pillar, which can meet in the center to form a 1.75 mm bridge. However, it is desirable to be able to increase the maximum bridge distance in the 3D printed part. [Overview of the project]

[0004] The following is a simplified overview to provide a basic understanding of some aspects of one or more embodiments of this teaching. This overview is not a comprehensive overview, nor does it identify important or key elements of this teaching, nor does it explicitly define the scope of this disclosure. On the contrary, its primary purpose is simply to present one or more concepts in a simplified form as an introduction to the more detailed explanations presented below.

[0005] A method for printing an internal bridge within a three-dimensional object is disclosed. The method includes the steps of: depositing a plurality of droplets of printing material in a first direction to form a supported step-out at the edge of a bridge layer; depositing a plurality of droplets of printing material to form an anchor layer adjacent to and in contact with the supported step-out; and depositing a plurality of droplets of printing material to form an unsupported step-out adjacent to and in contact with the supported step-out, wherein the anchor layer is formed at a first droplet spacing, and the unsupported step-out is formed at a second droplet spacing, the first droplet spacing being approximately 1.75 to approximately 2.50 times the second droplet spacing, and the internal bridge and anchor layer formed by the unsupported step-out are positioned at an angle of 0 to approximately 30 degrees with respect to the edge of the bridge layer. Embodiments of the method for printing an internal bridge within a three-dimensional object may include cases where the first droplet spacing is 0.7 mm or the second droplet spacing is 0.32 mm. Each droplet of the plurality of droplets used to form the unsupported step-out is depositable in a first direction. Each droplet of the plurality of droplets used to form the anchor layer can be deposited in a second direction opposite to the first direction. Unsupported step-outs are formed at a line spacing of 0.25 × n (mm) from the supported step-out, with n being the nth unsupported step-out. The anchor layer is formed at a line spacing of n × 0.25 + 0.125 (mm) from the supported step-out, with n being the nth anchor step-out. A method for printing an internal bridge in a three-dimensional object may include (a) depositing a third plurality of droplets of the printing material at a third droplet spacing to form an anchor layer adjacent to and in contact with the supported step-out; (b) depositing a plurality of droplets of the printing material at a second droplet spacing to form an unsupported step-out adjacent to and in contact with the anchor layer; and (c) repeating steps (b) and (c) until the required number of unsupported step-outs have been deposited. A method for printing an internal bridge in a three-dimensional object may include raising the temperature of the region surrounding the three-dimensional object. A method for printing an internal bridge within a three-dimensional object may include the step of heating a portion of the internal bridge.In one example, no printing material is deposited between the unsupported step-out or anchor layer and the substrate. There is no support material between the unsupported step-out or anchor layer and the substrate. The anchor layer is formed with n being the nth anchor step-out, at line spacings of n × 0.25 + 0.125 (mm) from the supported step-out.

[0006] A printing system for three-dimensional objects is disclosed. The printing system includes a reservoir configured to receive and melt a printing material, and an ejector having a nozzle that is fluidly connected to the reservoir and receives the molten printing material from the reservoir. The system also includes a platform positioned opposite the ejector. The system also includes at least one actuator operably connected to at least one of the platform and the ejector, the at least one actuator configured to move at least one of the platform and the ejector relative to the other. The system also includes a controller operably connected to the reservoir, the ejector and the at least one actuator, the controller configured to deposit a plurality of droplets of printing material in a first direction to form a supported step-out at the edge of a bridge layer, and to deposit a plurality of droplets of printing material to form an anchor layer adjacent to and in contact with the supported step-out. The system also includes depositing a plurality of droplets of printing material to form an unsupported step-out adjacent to and in contact with the supported step-out. An anchor layer is formed with a first droplet spacing, and an unsupported step-out is formed with a second droplet spacing, where the first droplet spacing is approximately 1.75 to 2.50 times the second droplet spacing, and the internal bridge and anchor layer formed by the unsupported step-out are positioned at an angle of 0 to approximately 30 degrees with respect to the edge of the bridge layer. Embodiments of the printing system for three-dimensional objects include the case where the first droplet spacing is 0.7 mm and the second droplet spacing is 0.32 mm. Each droplet of the plurality of droplets used to form the unsupported step-out is deposited in a first direction. Each droplet of the plurality of droplets used to form the anchor layer is deposited in a second direction opposite to the first direction. The unsupported step-outs are formed with a line spacing of 0.25 × n (mm) from the supported step-out, with n being the nth unsupported step-out.

[0007] A method for printing an internal bridge within a three-dimensional object is disclosed. The method for printing an internal bridge includes the steps of: calculating the number of layers n of unsupported step-out layers in the internal bridge based on the lateral dimension of the overhang of the internal bridge divided by the line width; depositing anchor layers in a first direction with a first droplet spacing; and depositing unsupported step-outs in a second direction with a second droplet spacing, wherein the second direction is opposite to the first direction. In an embodiment of the method for printing an internal bridge within a three-dimensional object, the line width is 0.25 mm, the first droplet spacing is 0.7 mm, and the second droplet spacing is 0.32 mm. A method for printing an internal bridge within a three-dimensional object may include the steps of forming an unsupported step-out from a supported step-out at a line spacing of 0.25 × n (mm), with n being the nth unsupported step-out, and forming an anchor layer from a supported step-out at a line spacing of n × 0.25 + 0.125 (mm), with n being the nth anchor step-out.

[0008] The features, functions, and advantageous effects described may be achieved independently in various embodiments, or may be combined in further embodiments, the further details of which can be understood by referring to the following description. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows a schematic cross-sectional view of one liquid metal ejector jet of a 3D printer (e.g., an MHD printer and / or a multi-jet printer) relating to this disclosure. [Figure 2A] The following is a perspective view of a 3D part including a first channel opening and a second channel opening relating to this disclosure. [Figure 2B] This diagram shows a cross-sectional perspective view of a 3D component relating to this disclosure, which shows a channel extending from a first channel opening to a second channel opening. [Figure 3A] A schematic top view of a bridge that can be printed on a channel according to an embodiment is shown. [Figure 3B]Another schematic top view with dimension indicators of a bridge that can be printed on a channel according to an embodiment is shown. [Figure 3C] Figure 3B shows the bridge relating to this disclosure, identifying the anchor, supported step-out, and unsupported step-out. [Figure 4A] This disclosure shows a 10 mm wide, zero-degree (0°) horizontal overhang printed using experimental values. [Figure 4B] This shows a cross-section of the step-out distance related to this disclosure. [Figure 5] This disclosure shows a flowchart of a method for bridging channels within a 3D part using a 3D printer. [Modes for carrying out the invention]

[0010] The accompanying drawings, which are incorporated into and form part of this specification, illustrate embodiments of this teaching and, together with the detailed description, serve to illustrate the principles of this disclosure.

[0011] It should be noted that some details in the drawings have been simplified and are drawn to facilitate understanding of this instruction rather than to ensure strict structural accuracy, detail, and scale.

[0012] Hereinafter, exemplary embodiments of this teaching will be referred to in more detail, and examples thereof are shown in the accompanying drawings. Where possible, the same reference numerals are used throughout the drawings to refer to the same, similar, or identical parts / components.

[0013] For the purposes of this disclosure, the term "print path" may be defined as the path or course that a drop-on-demand printer follows in accordance with its executable program instructions to complete the construction of an object. Line spacing may be defined as the distance between a print line, which the drop-on-demand printer follows in accordance with its program instructions to complete the construction of an object, and adjacent or neighboring print lines. Alternatively, line spacing may be considered as the distance between a print path and an adjacent print path, and possibly parallel print paths. Droplet spacing may be defined as the distance between droplets ejected from a drop-on-demand printing system. The distance between droplets or droplet spacing may be expressed in a dimension of time, such as milliseconds, or in a dimension of distance, such as millimeters. In this context, droplets are separated along a single print path or line.

[0014] The term "bridge layer" refers to the final layer of a 3D object or part fabricated before a step-out is formed. A step-out (or step-out) is defined as a layer or group of droplets deposited or printed by an ejector that deviates horizontally from the edge of a 3D part or object or from the bridge layer. A supported step-out is defined as a series of droplets (or dropletlets) that are in full contact with or above the bridge layer or other supporting structure within the 3D object. An unsupported step-out is defined as a series of droplets in an overhang with similar droplet spacing to the bridge layer and supported step-out, with no printed material deposited between the unsupported step-out and the substrate. An anchor layer is a series of droplets in an overhang with wider droplet spacing compared to the bridge layer, supported step-out, or unsupported step-out. No printed material is deposited between the anchor layer and the substrate. An overhang is an unsupported structure formed during the fabrication, manufacturing, or printing of a 3D object or part. A supportless structure does not have any printed material or support structure between the overhang portion of the 3D part and the platform or substrate on which the 3D part is fabricated.

[0015] In a liquid drop-on-demand (DOD) jet printing system, the ability to produce unsupported overhangs is important, particularly for extending the scope of printable designs for internal cavities where support pillars cannot be accessed and removed after a three-dimensional (3D) part is completed. One such approach involves bridging internal channels within a 3D object formation. The present disclosure provides systems and methods for producing 0-degree (horizontal) overhangs forming internal bridges, which comprises depositing a plurality of droplets of printing material in a first direction to form a supported step-out at an edge of a bridge layer; depositing a plurality of droplets of printing material to form an unsupported step-out adjacent to and in contact with the supported step-out; and depositing a plurality of droplets of printing material to form an anchor layer adjacent to and in contact with the unsupported step-out. In an example of this method, the anchor layer is formed with a first droplet spacing, the unsupported step-out is formed with a second droplet spacing, the first droplet spacing is from about 1.75 times to about 2.50 times the second droplet spacing, and the internal bridge and the anchor layer formed by the unsupported step-out are arranged at an angle of from 0 degrees to about 30 degrees relative to the edge of the bridge layer.

[0016] For the purposes of the present disclosure, an overhang may be defined as an unsupported feature of a 3D printed part that is not lifted or supported by an underlying support structure or other printed element. A layer-by-layer printing approach involving liquid or molten printing material can produce one or more lower surfaces of an inclined surface of a part, and each subsequent layer must project slightly beyond the preceding layer. Since the molten printing material is still in its fluid state before solidification, gravity and other factors such as the overhang angle and the inclined surface may cause sagging or deflection, curling, or otherwise hinder the printing of the desired shape. An outward overhang refers to an overhang that protrudes outward, that is, laterally relative to a previously formed portion of a three-dimensional part by only one continuous contact area between an initial portion of the three-dimensional part and the overhang. A central overhang refers to an overhang that protrudes inward, that is, laterally relative to a previously formed portion of a three-dimensional part by two or more, that is, at least two continuous contact areas between an initial portion of the three-dimensional part and the central overhang. By way of example, a central overhang may also be referred to as a bridge or a bridge layer within the overall structure of a three-dimensional part. For the purposes of the present disclosure, the term "step-out" may be used interchangeably with overhang, since ejected droplets forming an unsupported overhang structure may be considered to "protrude" at an angle of 0 degrees from the horizontal plane associated with the three-dimensional part or object while being printed or formed.

[0017] Examples of the present disclosure provide a printing approach that enables printing of complex features such as reentrant geometries, hollow features, overhangs and fine internal bridge features that cannot be machined with conventional tools due to, for example, space constraints or reachability. These features can be printed using the method and system of the present disclosure by printing structures and features divided among a plurality of layers. Very simple 2D layers can be printed stacked on top of each other until the entire object is completed.

[0018] Certain liquid printing processes can produce three-dimensional parts with extreme overhangs, as described herein, which are only possible by bridging support structures. Currently, support layers consist of finely spaced and extending solid supports constructed from printing material, including aluminum or other applicable printing materials. Once the part is printed, these support structures must be removed, but often a rough overhang surface remains due to the molten metal or molten printing material settling into the fine gaps of the support structures before solidification. Some residual support structures may remain attached to the part after the support structures have been removed. This requires one or more post-processing steps to provide a better surface finish. Printing overhangs without supports can offer improved printing efficiency, reduced post-processing, and other benefits. Removing support structures from internal channels or structures can be particularly difficult when the design parameters of an object fabricated in this manner determine internal channels.

[0019] In previous printing methods, the formation of support structures within 3D metal objects using droplet-ejection 3D object printers has been explored. These studies have shown that the maximum bridge distance initially achievable without support is 7 × 0.25 mm = 1.75 mm (with seven supports separated by 0.25 mm intervals), which corresponds to printing 0.875 mm long (1.75 / 2 = 0.875 mm) overhang segments printed from opposite ends so that they meet in the center. Each newly printed bridge line steps out from the previous line in the XY plane and is therefore called "supportless step-out". This instruction describes a new toolpath for printing supportless bridges exceeding 1.75 mm for a nozzle size of 475 microns.

[0020] Internal channels are a common feature found in various 3D object design applications, such as manifolds and heat exchangers. These features are essentially used to allow fluids to pass through the structure of a part for the part's effective performance. These features are difficult to generate using conventional manufacturing methods. This disclosure provides an experimentally determined method for providing printed parts with internal bridges on channels or other structures.

[0021] Figure 1 shows a schematic cross-sectional view of a liquid metal ejector jet of a 3D printer (e.g., an MHD printer and / or a multi-jet printer) according to the present disclosure. Figure 1 shows a part of a type of drop-on-demand (DOD) or three-dimensional (3D) printer 100. The 3D printer or liquid ejector jet system 100 may include an ejector (also called the body, pump chamber, or “integrated” pump) 104 within an outer ejector housing (enclosure) 102, also called the lower block. The ejector 104 may define an internal volume 132 (also called an internal cavity or inner cavity). Printing material 126 may be introduced into the internal volume 132 of the ejector 104. This internal volume 132 may be considered a reservoir configured to receive and melt the printing material within the internal volume 132 of the ejector 104. The printing material 126 may be a metal, a polymer, or the like, or may contain such a material. It should be noted that alternative ejection technologies other than MHD described herein may be required depending on the properties and characteristics of the printing material used in the examples of this disclosure. For example, the printing material 126 may be aluminum or an aluminum alloy, in this case an aluminum wire, introduced by a spool of the printing material supply unit 116 or the printing material wire feed 118, or may contain an aluminum wire. The liquid ejector jet system 100 further includes a first inlet 120 within the pump cap or upper cover portion 108 of the ejector 104, thereby introducing the printing material wire feed 118 into the internal volume 132 of the ejector 104. The ejector 104 further defines the nozzle 110, the area of ​​the upper pump 122, and the area of ​​the lower pump 124. One or more heating elements 112 are dispersed around the pump chamber (ejector) 104 to provide a heating source and maintain the printing material 126 in a molten state during printer operation. The heating element 112 is configured to heat or melt the printing material wire feed 118, thereby changing the printing material wire feed 118 from a solid state to a liquid state (e.g., printing material 126) within the internal volume 132 of the ejector 104.The three-dimensional (3D) printer 100 and ejector 104 may further include an air or argon shield 114 located near the nozzle 110 and a water coolant source 130 to allow temperature control of the nozzle and / or ejector 104. The liquid ejector jet system 100 further includes a system of liquid level sensors 134, which are configured to detect the liquid level of the molten printing material 126 inside the ejector 104 by directing a detector beam 136 toward the surface of the printing material 126 inside the ejector 104 and reading the reflected detector beam 136 inside the liquid level sensors 134.

[0022] The 3D printer 100 may also include a power supply (not shown here) and one or more metal coils 106 surrounded by a pump heater wound at least partially around the ejector 104. The power supply may be connected to the coils 106 and configured to supply current to the coils 106. This current can be supplied as pulses energized at a specific frequency, which determines the rate at which the pulses energize the coils 106 and thus how often droplets can be ejected from the ejector 104. The increasing magnetic field produced by the coils 106 can generate an electromotive force within the ejector 104 and similarly induce a current within the printing material 126. The magnetic field and induced current in the printing material 126 can generate a radially inward force on the printing material 126 known as the Lorentz force. The Lorentz force generates pressure at the inlet of the nozzle 110 of the ejector 104. This pressure causes the printing material 126 to be ejected through the nozzle 110 in the form of one or more droplets 128.

[0023] The 3D printer 100 may also include a substrate 144 or platform positioned near (e.g., below) the nozzle 110. The ejected droplets 128 can land on the substrate 144 and solidify to create a 3D object. The 3D printer 100 may also include a substrate control motor configured to move the substrate 144 to a desired shape and size while droplets 128 are being ejected through the nozzle 110, or during pauses while droplets 128 are being ejected through the nozzle 110. The substrate control motor may be configured to move the substrate 144 in one dimension (e.g., along the X-axis), two dimensions (e.g., along the X and Y axes), or three dimensions (e.g., along the X, Y, and Z axes). In other examples, further or alternatively, the ejector 104 and / or nozzle 110 may be configured to move in one, two, or three dimensions. In other words, the substrate 144 may move below the fixed nozzle 110, or the nozzle 110 may move above the fixed substrate 144. In yet another example, the nozzle 110 and the substrate 144 may rotate relative to each other around one or two additional axes to achieve four-axis or five-axis position control. In some examples, both the nozzle 110 and the substrate 144 may move. For example, the nozzle 110 may move upward and / or downward in the Y direction, while the substrate 144 moves in the X and Y directions. For the purposes of this disclosure, the print bed may also be referred to as the substrate.

[0024] The 3D printer 100 may include one or more gas control devices, which may be or include a gas source 138. The gas source 138 may be configured to introduce gas. The gas may be or include an inert gas such as helium, neon, argon, krypton and / or xenon. In other examples, the gas may be or include nitrogen. The gas may contain less than about 10% oxygen, less than about 5% oxygen, or less than about 1% oxygen. In at least one example, the gas may be introduced via a gas line 142 which includes a gas regulator 140 configured to regulate the flow or rate of one or more gases introduced from the gas source 138 into the three-dimensional (3D) printer 100. For example, the gas may be introduced at a position above the nozzle 110 and / or heating element 112. This may allow the gas (e.g., argon) to form a covering / sheath around the nozzle 110, droplet 128, 3D object and / or substrate 144, thereby reducing / preventing the formation of oxides (e.g., aluminum oxide) in the form of an air shield 114. Controlling the gas temperature may further or alternatively help control (e.g., minimize) the rate at which oxide formation occurs.

[0025] The liquid ejector jet system 100 may also include an enclosure 102 that defines the internal volume (also called the atmosphere). In one example, the enclosure 102 may be hermetically sealed. In other examples, the enclosure 102 may not be hermetically sealed. In one example, the ejector 104, heating element 112, power supply, coil, substrate 144, additional system elements, or a combination thereof may be located at least partially inside the enclosure 102. In other examples, the ejector 104, heating element 112, power supply, coil, substrate 144, additional system elements, or a combination thereof may be located at least partially outside the enclosure 102. The liquid ejector jet system 100 shown in Figure 1 is a general representation of the liquid ejector jet system 100, and the location and specific configuration and / or physical relationships of various features may differ in alternative design examples.

[0026] The printing systems described herein, or printing systems having other printing material raw materials and / or ejection systems, may alternatively include other printing materials, such as plastics or other non-metallic ductile materials. The printing materials may include metals, metal alloys, or combinations thereof. Non-limiting examples of printing materials may include aluminum. An exemplary example of a printing system of this disclosure may include an ejector for ejecting a printing material, comprising a structure defining an inner cavity and a nozzle pore connected to the inner cavity, and configured to eject one or more droplets of liquid printing material. The ejector is configured to form an overhang over a three-dimensional printed part.

[0027] In other well-known methods, such as the one shown in Figure 1, a printer includes a controller configured to receive commands or a programmed set of coordinates from a computing device and operate an ejector head to construct various elements of a 3D object. A reservoir or internal volume is configured to receive and melt the printing material, while an ejector with a nozzle is fluidly connected to the reservoir to receive the melted printing material from the reservoir. Since the platform is positioned opposite the ejector, there is at least one actuator operably connected to at least one of the platform and the ejector, and the at least one actuator is configured to move at least one of the platform and the ejector relative to the other. The controller is further operably connected to the reservoir, at least one ejector and at least one actuator and is configured to execute commands for various printing methods as described herein.

[0028] Figures 2A and 2B show perspective views of a 3D part including a first channel opening and a second channel opening, and a cross-sectional perspective view of a 3D part showing a channel extending from the first channel opening to the second channel opening, respectively. Figure 2A shows a perspective view of a 3D part 200 according to an embodiment, and Figure 2B shows a cross-sectional perspective view of a 3D part 200 according to an embodiment. The 3D part 200 may include an internal channel 202 extending from a first channel opening 204 to a second channel opening 206. In one example, the 3D part 200 may be a manifold or a heat exchanger, and the channel 202 may be used to allow fluid to pass through the 3D part 200 for effective performance. In the operation steps of a 3D printing system as described herein, toolpath generation for an unsupported step-out to print the internal bridge may be employed. The 3D printer 100 may print the internal bridge 210 on at least a portion of the channel 202. As described in more detail below, the bridge 210 may include multiple unsupported step-outs. The distance between the unsupported step-outs may be approximately 0.10 mm to 0.40 mm, 0.20 mm to 0.30 mm (e.g., 0.25 mm), or 0.19 mm to 0.25 mm. Multiple anchor droplets may be printed to print the bridge 210 beyond 1.75 mm (i.e., wider). The anchor droplets may be sparsely spaced and will have little contact with previously printed unsupported step-outs, so that they can be used as supports for the next unsupported step-out line. The anchor droplets may form an anchor line or anchor layer. The anchor layer may have droplet spacing of approximately 0.5 mm to 1.0 mm or approximately 0.6 mm to 0.8 mm (e.g., 0.7 mm). As used herein, droplet spacing refers to the distance between droplets in a printing path (e.g., linear or curved), such as an anchor line. The anchor droplet can be positioned approximately 0.100 mm to 0.150 mm (e.g., 0.125 mm) away from the previous unsupported step-out.

[0029] The starting points of anchor droplets for each anchor line can be printed randomly to avoid deposition at the same point for each unsupported step-out. As used here, random printing means starting the deposition of the first anchor droplet in the anchor layer at a randomly determined position along the anchor line or anchor layer. In this embodiment, anchor droplets can be started randomly at various positions along the anchor line, as over-facing can only occur in areas where droplets on the unsupported step-out line overlap with sparsely spaced droplets on the anchor line. The values ​​for droplet spacing and / or line spacing relative to the unsupported step-out, anchors, are determined experimentally by printing a curved bridge and varying the values ​​for each iteration. Anchor droplets are deposited on the unsupported step-out. The droplet spacing in the anchor layer is wider than the droplet spacing of adjacent line paths. The alternating directions when depositing the anchor layer give the droplets time to cool properly before a return operation to print additional droplets or subsequent layers. By initiating anchor droplets at random locations along a path or line, the regular spacing of the anchor droplets is interrupted. If deposited at regular intervals, excess material will be created in certain areas, resulting in the creation of a visible pattern in the part. The location of the first anchor droplet in the anchor layer is randomly selected between the maximum and minimum droplet spacings. This wider spacing between anchor droplets can accelerate the cooling or solidification of the deposited anchor droplets, which would otherwise be caused by sparser spacing. Adjacent lines, such as step-out or standard fill print layers, are printed at narrower intervals and therefore cool more slowly.

[0030] Figures 3A and 3B show schematic top views of a bridge that can be printed on a channel according to an embodiment, and another schematic top view of a bridge that can be printed on a channel with dimension indicators, respectively. Figure 3C shows the bridge according to Figure 3B according to the present disclosure, identifying anchors, supported step-outs and unsupported step-outs. As shown in Figure 3A, there is an initial layer in the formation of the internal bridge, which consists of supported step-outs 300, in which at least a portion of the underside of each individual droplet 306 is supported from below by the rest of the 3D object structure. Next, an anchor layer 304 follows an unsupported step-out 302. For the remaining width of the internal bridge, the formation alternates between unsupported step-outs 302 adjacent to and in contact with the preceding anchor layer 304, and subsequent anchor layers 304 adjacent to and in contact with the preceding unsupported step-out 302. The same configuration is shown in Figure 3B with approximate dimensions in mm, and the droplets and layer structures shown in Figure 3A are superimposed. Figure 3C schematically illustrates a similar bridge structure, further highlighting the configuration of the supported step-out 300, the unsupported step-out 302, and the anchor layer 304. Figure 3C further shows the toolpath architecture for the horizontal overhang (e.g., 10 mm) above the supports in the bridge layer. In Figure 3C, there are a total of 40 unsupported step-outs, each spaced a predetermined distance apart. The predetermined distance can range from approximately 0.10 mm to approximately 0.40 mm. For example, the predetermined distance could be 0.25 mm. In this example, the horizontal overhang is 40 unsupported step-outs × 0.25 mm = 10 mm. In other examples, the horizontal overhang for the internal channel may range from approximately 0.10 mm to approximately 25 mm.

[0031] Example toolpath for printing a 0° unidirectional bridge As used herein and further illustrated in Figure 3C, a bridge layer refers to an uppermost or roof layer that defines the uppermost portion of an internal channel in a 3D object or part. In the bridge layer, a supported step-out 300 with a droplet spacing of 0.2 mm may be printed on the top of a column or on the edge of a solid part of the 3D object. Subsequently, an anchor layer 304 with a droplet spacing of 0.7 mm may be printed in a first (e.g., clockwise) direction at a distance of 0.125 mm from the unsupported step-out. Since the first unsupported step-out is 0.25 mm from the supported step-out, the first anchor may be printed at 0.25 mm + 0.125 mm = 0.375 mm from the supported step-out. Next, an unsupported step-out 302 with a droplet spacing of 0.32 mm may be printed in a second (e.g., counterclockwise) direction at a distance of 0.25 mm from the supported step-out. Again, an anchor layer 304 with a droplet spacing of 0.7 mm can be printed in a clockwise direction over a distance of 0.625 mm (2 × 0.25 mm + 0.125 mm). A new unsupported step-out 302 can be printed in a counterclockwise direction over a distance of 0.5 mm (2 × 0.25 mm). This can be continued until the desired number of unsupported step-outs 302 are produced. The unsupported step-outs can be initiated in two ways. The first way to initiate an unsupported step-out 302 is from a supported step-out 300. The second way to initiate an unsupported step-out 302 is from the inner periphery.

[0032] Print the internal bridge in one direction. Printing a 0° horizontal overhang in one direction with a bridge layer of a specific length can be determined as follows: The number of unsupported step-outs can be determined as follows: Number of unsupported step-outs (N) = length of horizontal overhang / 0.25 mm. For example, this toolpath can be determined using the following logic for code: In one example, the supported step-out and / or inner periphery may be at x. Direction = 1 → Clockwise i=1: floor(N) Print the anchor at x + i × 0.25 + 1.25 along the direction with a droplet spacing of 0.7 mm. Print an unsupported step-out pattern at x+i×0.25 along direction ×-1 with a droplet spacing of 0.32 mm. Direction = Direction × -1 end When N-floor(N)=0 Droplet spacing (ds_l) for the last unsupported step-out = 0.32 + 0.32 × (ls d -ls a ) / ls d ls d The desired line spacing is 0.25. ls a The actual line spacing is (N - floor(N)) × 0.25. Print the anchor along the direction x + (floor(N) + 1) × 0.25 + 1.25 with a droplet spacing of 0.7 mm. Print an unsupported step-out droplet along the direction × -1 at x + (floor(N) + 1) × 0.25 with a droplet spacing of ds_l. end

[0033] Print the internal bridge in two directions. Printing a 0° horizontal overhang in two directions with a specific length of bridge layer can be determined as follows: The number of unsupported step-outs can be determined. Here again, the number of unsupported step-outs is (N) = length of horizontal overhang / 0.25 mm. For example, the toolpath is as follows: 1. Calculate the number of unsupported step-outs. Number of unsupported step-outs (N) = Length of horizontal overhang / 0.25 2. Assume that there is a supported step-out or inner periphery at x1 and x2 on one side. Direction = 1 → Clockwise For i=1: floor(N / 2) Print the anchor at x1 + i × 0.25 + 1.25 along the direction with a droplet spacing of 0.7 mm. Print unsupported step-outs at x1+i×0.25 along direction ×-1 with a droplet spacing of 0.32 mm Print anchors at x2+i×0.25+1.25 along the direction with a droplet spacing of 0.7 mm Print unsupported step-outs at x2+i×0.25 along direction ×-1 with a droplet spacing of 0.32 mm direction = direction ×-1 End When N / 2-floor(N / 2)=0 Remaining unsupported step-outs (Nr)=(N / 2-floor(N / 2))×2 When Nr<1 Droplet spacing for the last unsupported step-out (ds_l)=0.32+0.32×(ls d -ls a ) / ls d ls d is the desired line spacing = 0.25 ls a is the actual line spacing = Nr×0.25 Print anchors at x1+(floor(N / 2)+1)×0.25+1.25 along the direction with a droplet spacing of 0.7 mm Print unsupported step-outs at x1+(floor(N / 2)+1)×0.25 along direction ×-1 with a droplet spacing of ds_l Otherwise, when Nr=1 Print anchors at x1+(floor(N / 2)+1)×0.25+1.25 along the direction with a droplet spacing of 0.7 mm Print unsupported step-outs at x1+(floor(N / 2)+1)×0.25 along direction ×-1 with a droplet spacing of 0.32 mm In other cases Print anchors at x1+(floor(N / 2)+1)×0.25+1.25 along the direction with a droplet spacing of 0.7 mm Print unsupported step-outs at x1+(floor(N / 2)+1)×0.25 along direction ×-1 with a droplet spacing of 0.32 mm Droplet spacing (ds_l) for the last unsupported step-out = 0.32 + 0.32 × (ls d -ls a ) / ls d ls d The desired line spacing is 0.25. ls a The actual line spacing is (Nr-1) × 0.25. Print the anchor along the direction with a droplet spacing of 0.7 mm at x2 + (floor(N / 2) + 1) × 0.25 + 1.25. Print an unsupported step-out pattern in x2 + (floor(N / 2) + 1) × 0.25 direction × -1 with a droplet spacing of ds_l. end end

[0034] By following one of the above scenarios, anchors and unsupported step-outs are printed using a frequency of 300 Hz, making it possible to print internal bridges or horizontal overhangs at a 0° angle without compromising throughput. When these features are printed, they may not be exactly 0° in some cases, but can vary up to 26.8° or even 30° due to some temperature mismatch as the toolpath prints further away from the bulk of the part. In one example, printing a 10 mm 0° horizontal overhang resulted in an 11.21 mm 26.8° horizontal overhang. This lift-off, or difference in the achieved angle compared to the target angle, is caused by uneven temperature distribution throughout the printed object. Because the unsupported step-outs extend outward, the deposited droplets move away from the solid part area, and their temperature is lower than that of the bulk of the part. Such lift-off, i.e., the increasing angle relative to the horizontal, can be addressed by printing within the enclosure, increasing the bed temperature, increasing the frequency, or by targeted auxiliary heating, such as lasers or other heating methods, including but not limited to radiation or convection heating. This method has proven reliable in experiments and allows for the unsupported printing of large horizontal overhangs and bridges. While tests have been conducted up to a distance of 10 mm, it is understood that the method described herein can be further extended to 25 mm or less. For example, the line spacing of various layers, e.g., unsupported step-outs, where n is the nth unsupported step-out, are formed with a line spacing of 0.25 × n (mm) from the supported step-outs. With respect to anchor layers, anchor layers, where n is the nth anchor step-out, can be formed with a line spacing of n × 0.25 + 0.125 (mm) from the supported step-outs. The variable n is the total number of unsupported step-outs that make up the internal bridge, and the "nth" layer is the last layer in the internal bridge or structure.

[0035] Figures 4A and 4B show cross-sections of a 10 mm wide, experimentally printed zero-degree (0°) horizontal overhang and step-out distance, respectively, according to the present disclosure. A horizontal overhang structure 400 is shown, which has an upper surface 402 comprising one or more unsupported step-out layers and anchor layers as described above. Figure 4B is a cross-section of a total step-out distance 402A, as indicated by line AA, which has an unsupported portion 404 of the similarly shown part. Certain angles are illustrated in Figure 4B, but the angles shown may vary depending on the part design and specific printing conditions, so the angles shown do not necessarily represent the underside of the entire part.

[0036] Figure 5 shows a flowchart of a method for bridging channels within a 3D part using a 3D printer according to the present disclosure. The method 500 for printing an internal bridge within a three-dimensional object includes the steps of: 502 depositing a plurality of droplets of printing material in a first direction to form supported step-outs at the edge of a bridge layer; 504 depositing a plurality of droplets of printing material to form an anchor layer adjacent to and in contact with an unsupported step-out; and 506 depositing a plurality of droplets of printing material to form an unsupported step-out adjacent to and in contact with the supported step-out. In this method 500, the anchor layer is formed with a first droplet spacing, and the unsupported step-outs are formed with a second droplet spacing, the first droplet spacing being approximately 1.75 to 2.50 times the second droplet spacing, and the internal bridge and anchor layer formed by the unsupported step-outs are positioned at an angle of 0 to approximately 30 degrees with respect to the edge of the bridge layer. Method 500 may include a case where the first droplet spacing is 0.7 mm and the second droplet spacing is 0.32 mm. For example, the first droplet spacing may be approximately 0.45 mm to approximately 0.8 mm, approximately 0.5 mm to approximately 0.7 mm, or approximately 0.5 mm to approximately 0.6 mm. In a particular example, the second droplet spacing may be approximately 0.26 mm to approximately 0.32 mm, or approximately 0.28 mm to approximately 0.30 mm.

[0037] In certain examples, Method 500 may include a case where each droplet of a plurality of droplets used to form an unsupported step-out is deposited in a first direction, and each droplet of a plurality of droplets used to form an anchor layer is deposited in a second direction opposite to the first direction. Method 500 further includes a case where n is the nth unsupported step-out, the unsupported step-out is formed at a line spacing of 0.25 × n (mm) from a supported step-out, or where n is the nth anchor step-out, the anchor layer is formed at a line spacing of n × 0.25 + 0.125 (mm) from a supported step-out. A method 500 for printing internal bridges within a three-dimensional object may further include: (a) depositing a third plurality of droplets of printing material at a third droplet spacing to form an anchor layer adjacent to and in contact with an unsupported step-out; (b) depositing a plurality of droplets of printing material at a second droplet spacing to form an unsupported step-out adjacent to and in contact with the anchor layer; and (c) repeating steps (b) and (c) until the required number of unsupported step-outs are deposited. In some examples, the temperature of the region surrounding the three-dimensional object can be increased by heating a portion of the internal bridge or by other means well known to those skilled in the art. For example, the platform or substrate of the printing system may be heated, or an external heating method such as laser or other radiant heat treatment may be used. When employing method 500, no printing material is deposited between the unsupported step-out or anchor layer and the substrate, and no supporting material is present between the unsupported step-out or anchor layer and the substrate.

[0038] In another example of a method for printing an internal bridge within a three-dimensional object, step 501 may be completed before any physical operation of the printing system, which calculates the number of layers n of the unsupported step-out layers in the internal bridge based on the lateral dimension of the internal bridge's overhang divided by the line width. These operation steps may include depositing the anchor layer in a first direction with a first droplet spacing and depositing the unsupported step-out in a second direction with a second droplet spacing. In this example, the second direction is the opposite of the first direction. This method of printing an internal bridge within a three-dimensional object may include a line width of 0.25 mm. The first droplet spacing is 0.7 mm and the second droplet spacing is 0.32 mm. A method for printing an internal bridge within a three-dimensional object may further include the steps of forming an unsupported step-out from a supported step-out at a line spacing of 0.25 × n (mm), with n being the nth unsupported step-out, and forming an anchor layer from a supported step-out at a line spacing of n × 0.25 + 0.125 (mm), with n being the nth anchor step-out.

[0039] Although this instruction has been described with respect to one or more embodiments, modifications and / or alterations may be made to the described examples without departing from the spirit and scope of the subsequent claims. For example, although a process is described as a series of actions or events, it should be clear that this instruction is not limited by the ordering of those actions or events. Some actions may be performed in a different order and / or simultaneously with other actions or events than those described herein. Furthermore, not all processing steps need to implement the methods according to one or more aspects or embodiments of this instruction. Structural objects and / or processing steps may be added, or existing structural objects and / or processing steps may be removed or altered. Also, one or more of the actions illustrated herein may be performed in one or more separate actions and / or steps. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variations thereof are used in either the detailed description or the claims, these terms are inclusive in a similar manner to the term “comprising.” The term "at least one" is used to mean that one or more of the enumerated items may be selected. Also, in this description and in the claims, the terms "on" and "over" used with respect to two materials mean that one means at least some contact between the materials, while the other means that the materials are near each other, but contact is possible but not required, and possibly has one or more additional intervening materials. Neither "on" nor "over" implies any direction as used herein. The term "conformal" refers to a coating material in which the angle of the underlying material is maintained by the conforming material. The term "about" indicates that the enumerated values ​​may be changed to some extent, provided that the changes to the illustrated embodiments do not result in a nonconformity of processing or structure.The terms “couple,” “coupled,” “connect,” “connection,” “connected,” “in connection with,” and “connecting” mean “directly connected” or “connected via one or more intermediate elements or members.” Finally, the terms “exemplary” or “explanatory” indicate that the explanation is used as an example, not that it is ideal. Other embodiments of this teaching may become apparent to those skilled in the art from a review of the specification and the practice of the disclosure herein. The specification and examples are to be considered merely illustrative, insofar as they represent the true scope and spirit of this teaching as set forth by the following claims.

Claims

1. A method for printing an internal bridge within a three-dimensional object, A step of depositing multiple droplets of printing material in a first direction to form a supported step-out at the edge of the bridge layer, A step of depositing a plurality of droplets of the printing material to form an anchor layer adjacent to and in contact with the supported step-out, The steps include depositing a plurality of droplets of the printing material to form an unsupported step-out adjacent to and in contact with the supported step-out, Equipped with, The anchor layer is formed with a first droplet spacing, The aforementioned unsupported step-out is formed at a second droplet spacing, The first droplet spacing is approximately 1.75 to 2.50 times the second droplet spacing. A method for printing an internal bridge in a three-dimensional object, wherein the internal bridge and anchor layer formed by the unsupported step-out are positioned at an angle of 0 to approximately 30 degrees with respect to the edge of the bridge layer.

2. A method for printing an internal bridge within a three-dimensional object according to claim 1, wherein the first droplet spacing is 0.7 mm.

3. A method for printing an internal bridge within a three-dimensional object according to claim 1, wherein the second droplet spacing is 0.32 mm.

4. A method for printing an internal bridge within a three-dimensional object according to claim 1, wherein each of the plurality of droplets used to form the unsupported step-out is deposited in the first direction.

5. A method for printing an internal bridge in a three-dimensional object according to claim 1, wherein each of the plurality of droplets used to form the anchor layer is deposited in a second direction opposite to the first direction.

6. A method for printing an internal bridge within a three-dimensional object according to claim 1, wherein the unsupported step-out is formed at a line spacing of 0.25 × n (mm) from the supported step-out, with n being the nth unsupported step-out.

7. A method for printing an internal bridge within a three-dimensional object according to claim 1, wherein the anchor layer is formed with n as the nth anchor step-out, at line intervals of n × 0.25 + 0.125 (mm) from the supported step-out.

8. (a) A step of depositing a third plurality of droplets of the printing material at a third droplet interval to form an anchor layer adjacent to and in contact with the supported step-out, (b) A step of depositing a plurality of droplets of the printing material at a second droplet interval to form an unsupported step-out adjacent to and in contact with the anchor layer, (c) Repeating steps (b) and (c) until the required number of unsupported step-outs are accumulated, A method for printing an internal bridge within a three-dimensional object according to claim 1, further comprising:

9. A method for printing an internal bridge within a three-dimensional object according to claim 1, further comprising the step of raising the temperature of the region surrounding the three-dimensional object.

10. A method for printing an internal bridge in a three-dimensional object according to claim 1, further comprising the step of heating a portion of the internal bridge.

11. A method for printing an internal bridge within a three-dimensional object according to claim 1, wherein no printing material is deposited between the unsupported step-out or the anchor layer and the substrate.

12. A method for printing an internal bridge within a three-dimensional object according to claim 1, wherein no support material exists between the supportless step-out or the anchor layer and the substrate.

13. A printing system for three-dimensional objects, A reservoir configured to receive and melt printing material, An ejector having a nozzle that is fluidly connected to the reservoir and receives molten printing material from the reservoir, A platform positioned opposite the ejector, At least one actuator operably connected to at least one of the platform and the ejector, the at least one actuator configured to move the platform and the ejector relative to the other, A controller operably connected to the reservoir, the ejector, and the at least one actuator, Multiple droplets of printing material are deposited in a first direction to form a supported step-out at the edge of the bridge layer. Multiple droplets of the printing material are deposited to form an anchor layer adjacent to and in contact with the supported step-out. Multiple droplets of the printing material are deposited to form an unsupported step-out adjacent to and in contact with the supported step-out. A controller configured as follows, Equipped with, The anchor layer is formed with a first droplet spacing, The aforementioned unsupported step-out is formed at a second droplet spacing, The first droplet spacing is approximately 1.75 to 2.50 times the second droplet spacing. A printing system for three-dimensional objects, wherein the internal bridge and anchor layer formed by the unsupported step-out are positioned at an angle of 0 to approximately 30 degrees with respect to the edge of the bridge layer.

14. The first droplet spacing is 0.7 mm. The second droplet spacing is 0.32 mm. A printing system for a three-dimensional object according to claim 13.

15. A printing system for a three-dimensional object according to claim 13, wherein each of the plurality of droplets used to form the unsupported step-out is deposited in the first direction.

16. A printing system for a three-dimensional object according to claim 13, wherein each of the plurality of droplets used to form the anchor layer is deposited in a second direction opposite to the first direction.

17. The printing system for a three-dimensional object according to claim 13, wherein the unsupported step-outs are formed from the supported step-outs at a line spacing of 0.25 × n (mm), with n being the nth unsupported step-out.

18. A method for printing an internal bridge within a three-dimensional object according to claim 1, wherein the anchor layer is formed with n as the nth anchor step-out, at line intervals of n × 0.25 + 0.125 (mm) from the supported step-out.

19. A method for printing an internal bridge within a three-dimensional object, The steps include: calculating the number of layers n of the unsupported step-out layer in the internal bridge based on the lateral dimension of the overhang of the internal bridge divided by the line width; A step of depositing an anchor layer in a first direction with a first droplet spacing, A step of depositing unsupported step-outs in a second direction with a second droplet spacing, wherein the second direction is opposite to the first direction, A method for printing an internal bridge within a three-dimensional object that has [a specific feature / feature].

20. A method for printing an internal bridge within a three-dimensional object according to claim 19, wherein the line width is 0.25 mm.

21. The first droplet spacing is 0.7 mm. The second droplet spacing is 0.32 mm. A method for printing an internal bridge within a three-dimensional object according to claim 19.

22. The step of forming the unsupported step-out at a line interval of 0.25 × n (mm) from the supported step-out, with n being the nth unsupported step-out, The steps include forming the anchor layer with line spacing of n × 0.25 + 0.125 (mm) from the supported step-out, with n being the nth anchor step-out, A method for printing an internal bridge within a three-dimensional object according to claim 19, further comprising:

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