Patent Publication Number: US-2021177090-A1

Title: Cushioning structures

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/US2019/047101 filed on Aug. 19, 2019, which claims the benefit of U.S. Provisional Patent Application No. 62/725,722, filed Aug. 31, 2018. The entire contents of each of these applications are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The field of the invention is cushioning structures. In some examples, the cushioning structures may be manufactured using additive manufacturing. 
     Description of the Related Technology 
     Cushioning structures may be used for a variety of different purposes. For example, cushioning structures may be used in footwear, including customized footwear. Such customized footwear may be manufactured using additive manufacturing technologies such as 3-D printing, for example. Examples of cushioning structures can include foam or other structures configured to bend or deform and absorb force and thereby provide a cushioning effect from the force. 
     Cushioning structures may be used, for example, in a liner of a ski boot. For example, European Patent Application No. EP3320796A1, hereby incorporated by reference in its entirety, describes a custom ski shoe that includes an inner shoe that has different zones constructed with different structures to provide different mechanical properties in each of the different zones. This can improve wearing comfort by choosing the appropriate structure for the appropriate zone based on the desired mechanical properties. Accordingly, EP3320796A1 describes generic structures such as generic honeycomb, bar, lattice, 3D lattice, trigonal, tetragonal, and cubic structures that can be used to provide different mechanical properties in different zones. 
     However, a disadvantage of existing cushioning structures is that they are not optimized for force absorption, such as for providing different levels of force absorption in different directions. Another disadvantage of existing cushioning structures, such as generic structures, is that they are not optimized for 3-D printing. For example, the scanning patterns (e.g., pattern in 2D over which energy is applied to build material for generating a layer of an object on a layer-by-layer basis) needed to generate the generic structures may be inefficient or complex, leading to excess energy consumption and a higher rate of build failure for 3-D printing. 
     SUMMARY 
     Certain embodiments herein provide a cushioning structure comprising a plurality of unit cells formed in an array, each unit cell of the plurality of unit cells comprising one or more first walls parallel to a central plane and a first protruding structure that protrudes from the central plane, the first protruding structure forming a concave structure on a first side of the central plane and a convex structure on a second side of the central plane, the first protruding structure comprising one or more walls at a non-perpendicular angle to the central plane. 
     Certain embodiments provide a computer-implemented method of designing an object with a cushioning structure. The method includes generating a first digital model corresponding to a negative of an array, the array comprising a plurality of unit cells. The method further includes superimposing the first digital model over a digital model of a solid structure corresponding to the object. The method further includes performing a Boolean subtraction of the digital model of the solid structure from the first digital mode to generate a second digital model corresponding to a second negative array having a shape corresponding to the solid structure. The method further includes performing a second Boolean subtraction of the second digital model from the digital model of the solid structure to generate a digital model of the object comprising at least a portion of the array. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a computer environment suitable for the implementation of 3D object design and manufacturing. 
         FIG. 2  illustrates an example functional block diagram of one example of a computer. 
         FIG. 3  shows an example high level process for manufacturing a 3D object using the methods and systems disclosed herein. 
         FIG. 4  is an example of a scanning system which may be used to manufacture a cushioning structure as described herein. 
         FIGS. 5A-5C  show an example of a unit cell with angled walls that can be used to form a cushioning structure, according to certain embodiments. 
         FIGS. 5D-5F  show another example of a unit cell with angled walls that can be used to form a cushioning structure, according to certain embodiments. 
         FIGS. 5G-5I  show yet another example of a unit cell with angled walls that can be used to form a cushioning structure, according to certain embodiments. 
         FIGS. 5J-5L  show yet another example of a unit cell with angled walls that can be used to form a cushioning structure, according to certain embodiments. 
         FIGS. 5M-5O  show yet another example of a unit cell with angled walls that can be used to form a cushioning structure, according to certain embodiments. 
         FIGS. 6A-6H  illustrate an example of a 2D cushioning structure formed of a plurality of unit cells of  FIGS. 5A-5C , according to certain embodiments. 
         FIGS. 7A and 7B  illustrate an example of a 3D cushioning structure formed as a stack of 2D cushioning structures of  FIGS. 6A-6C , according to certain embodiments. 
         FIG. 8  illustrates a view of an exterior structure of a shoe, according to certain embodiments. 
         FIG. 9  illustrates one or more 2D or 3D cushioning structures inside a hollow shell of a shoe, according to certain embodiments. 
         FIGS. 10A-10C  illustrate example see-through views of an example shoe in various positions, according to certain embodiments. 
         FIG. 11  illustrates an example see-through view of an example shoe on the foot of a wearer, according to certain embodiments. 
         FIG. 12  illustrates a flowchart of example operations for designing an object including cushioning structures, according to certain embodiments. 
         FIG. 13  illustrates an example of a negative array superimposed over a solid structure representing a hollow shell, according to certain embodiments. 
         FIG. 13A  illustrates a close up view of a portion of a negative array, according to certain embodiments. 
         FIG. 14  illustrates an example of a resulting object of the operations of  FIG. 12 , according to certain embodiments. 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS 
     Embodiments of this disclosure relate to cushioning structures formed of a plurality of unit cells. A unit cell is referred to as a “unit” cell in that in certain embodiments it refers to an individual unit that is repeated in a pattern to form a cushioning structure. For example, a plurality of unit cells may be arranged in 3D space and coupled to one another (e.g., directly coupled to one another without additional structure between one another) to form a cushioning structure. In certain embodiments, the design of the unit cell includes angled walls, and allows for the plurality of unit cells to be stacked together to form an array (e.g., a 2D array, such as over an X-axis and Y-axis or a 3D array such as over an X, Y, and Z axis). Based on the angled walls and stackability, a cushioning structure based on the plurality of unit cells advantageously can provide an improved cushioning effect, such as a different cushioning effect based on the direction force is applied. Further, a cushioning structure based on the plurality of unit cells can advantageously be manufactured more efficiently using 3D printing techniques by allowing the use of long continuous vectors in a scanning pattern for 3D printing the cushioning structure. This reduces the chance of errors in the manufacturing of the cushioning structure, and can also reduce power consumption. 
     Certain embodiments are described herein with respect to footwear, such as a shoe or a ski boot liner, that utilizes one or more cushioning structures as discussed herein. However, it should be noted that the cushioning structures discussed herein may be used for a variety of other applications. 
     Further, certain embodiments of cushioning structures are described herein as being manufactured using additive manufacturing or 3D printing. However, it should be noted that other suitable manufacturing techniques could be used to manufacture such cushioning structures. 
     Additive Manufacturing Systems 
     Embodiments of the invention may be practiced within a system for designing and manufacturing 3D objects. Turning to  FIG. 1 , an example of a computer environment suitable for the implementation of 3D object design and manufacturing is shown. The environment includes a system  100 . The system  100  includes one or more computers  102   a - 102   d,  which can be, for example, any workstation, server, or other computing device capable of processing information. In some aspects, each of the computers  102   a - 102   d  can be connected, by any suitable communications technology (e.g., an internet protocol), to a network  105  (e.g., the Internet). Accordingly, the computers  102   a - 102   d  may transmit and receive information (e.g., software, digital representations of 3-D objects, commands or instructions to operate an additive manufacturing device, etc.) between each other via the network  105 . 
     The system  100  further includes one or more additive manufacturing devices or apparatuses (e.g., 3-D printers)  106   a - 106   b.  As shown the additive manufacturing device  106   a  is directly connected to a computer  102   d  (and through computer  102   d  connected to computers  102   a - 102   c  via the network  105 ) and additive manufacturing device  106   b  is connected to the computers  102   a - 102   d  via the network  105 . Accordingly, one of skill in the art will understand that an additive manufacturing device  106  may be directly connected to a computer  102 , connected to a computer  102  via a network  105 , and/or connected to a computer  102  via another computer  102  and the network  105 . 
     It should be noted that though the system  100  is described with respect to a network and one or more computers, the techniques described herein also apply to a single computer  102 , which may be directly connected to an additive manufacturing device  106 . 
       FIG. 2  illustrates a functional block diagram of one example of a computer of  FIG. 1 . The computer  102   a  includes a processor  210  in data communication with a memory  220 , an input device  230 , and an output device  240 . In some embodiments, the processor is further in data communication with an optional network interface card  260 . Although described separately, it is to be appreciated that functional blocks described with respect to the computer  102   a  need not be separate structural elements. For example, the processor  210  and memory  220  may be embodied in a single chip. 
     The processor  210  can be a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any suitable combination thereof designed to perform the functions described herein. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The processor  210  can be coupled, via one or more buses, to read information from or write information to memory  220 . The processor may additionally, or in the alternative, contain memory, such as processor registers. The memory  220  can include processor cache, including a multi-level hierarchical cache in which different levels have different capacities and access speeds. The memory  220  can also include random access memory (RAM), other volatile storage devices, or non-volatile storage devices. The storage can include hard drives, optical discs, such as compact discs (CDs) or digital video discs (DVDs), flash memory, floppy discs, magnetic tape, and Zip drives. 
     The processor  210  also may be coupled to an input device  230  and an output device  240  for, respectively, receiving input from and providing output to a user of the computer  102   a.    
     Suitable input devices include, but are not limited to, a keyboard, buttons, keys, switches, a pointing device, a mouse, a joystick, a remote control, an infrared detector, a bar code reader, a scanner, a video camera (possibly coupled with video processing software to, e.g., detect hand gestures or facial gestures), a motion detector, or a microphone (possibly coupled to audio processing software to, e.g., detect voice commands). Suitable output devices include, but are not limited to, visual output devices, including displays and printers, audio output devices, including speakers, headphones, earphones, and alarms, additive manufacturing devices, and haptic output devices. 
     The processor  210  further may be coupled to a network interface card  260 . The network interface card  260  prepares data generated by the processor  210  for transmission via a network according to one or more data transmission protocols. The network interface card  260  also decodes data received via a network according to one or more data transmission protocols. The network interface card  260  can include a transmitter, receiver, or both. In other embodiments, the transmitter and receiver can be two separate components. The network interface card  260 , can be embodied as a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any suitable combination thereof designed to perform the functions described herein. 
       FIG. 3  illustrates a process  300  for manufacturing a 3-D object or device, such as an object including one or more cushioning structures as discussed herein. As shown, at a step  305 , a digital representation of the object is designed using a computer, such as the computer  102   a.  For example, 2-D or 3-D data may be input to the computer  102   a  for aiding in designing the digital representation of the 3-D object. Continuing at a step  310 , information is sent from the computer  102   a  to an additive manufacturing device, such as additive manufacturing device  106 , and the device  106  commences the manufacturing process in accordance with the received information. At a step  315 , the additive manufacturing device  106  continues manufacturing the 3-D object using suitable materials, such as a liquid resin. 
     These suitable materials may include, but are not limited to a photopolymer resin, polyurethane, methyl methacrylate-acrylonitrile-butadiene-styrene copolymer, resorbable materials such as polymer-ceramic composites, etc. Examples of commercially available materials are: DSM Somos® series of materials 7100, 8100, 9100, 9420, 10100, 11100, 12110, 14120 and 15100 from DSM Somos; ABSplus-P430, ABSi, ABS-ESD7, ABS-M30, ABS-M30i, PC-ABS, PC ISO, PC, ULTEM 9085, PPSF and PPSU materials from Stratasys; Accura Plastic, DuraForm, CastForm, Laserform and VisiJet line of materials from 3-Systems; the PA line of materials, PrimeCast and PrimePart materials and Alumide and CarbonMide from EOS GmbH. The VisiJet line of materials from 3-Systems may include Visijet Flex, Visijet Tough, Visijet Clear, Visijet HiTemp, Visijet e-stone, Visijet Black, Visijet Jewel, Visijet FTI, etc. Examples of other materials may include Objet materials, such as Objet Fullcure, Objet Veroclear, Objet Digital Materials, Objet Duruswhite, Objet Tangoblack, Objet Tangoplus, Objet Tangoblackplus, etc. Another example of materials may include materials from the Renshape 5000 and 7800 series. Further, at a step  320 , the 3-D object is generated. 
       FIG. 4  illustrates an example additive manufacturing apparatus  400  for generating a three-dimensional (3-D) object. In this example, the additive manufacturing apparatus  400  is a laser sintering device. The laser sintering device  400  may be used to generate one or more 3D objects layer by layer. The laser sintering device  400 , for example, may utilize a powder (e.g., metal, polymer, etc.), to build an object a layer at a time as part of a build process. 
     Successive powder layers are spread on top of each other using, for example, a recoating mechanism (e.g., a recoater blade, drum, or roller). The recoating mechanism deposits powder for a layer as it moves across the build area, for example in the direction shown, or in the opposite direction if the recoating mechanism is starting from the other side of the build area, such as for another layer of the build. After deposition, a computer-controlled CO2 laser beam scans the surface according to a scanning pattern and selectively binds together the powder particles of the corresponding cross section of the product. In some embodiments, the laser scanning device is an X-Y moveable infrared laser source. As such, the laser source can be moved along an X axis and along a Y axis in order to direct its beam to a specific location of the top most layer of powder according to the scanning pattern. Alternatively, in some embodiments, the laser scanning device may comprise a laser scanner which receives a laser beam from a stationary laser source, and deflects it over moveable mirrors to direct the beam to a specified location in the working area of the device according to the scanning pattern. During laser exposure, the powder temperature rises above the material (e.g., glass, polymer, metal) transition point after which adjacent particles flow together to create the 3D object. The device  400  may also optionally include a radiation heater (e.g., an infrared lamp) and/or atmosphere control device. The radiation heater may be used to preheat the powder between the recoating of a new powder layer and the scanning of that layer. In some embodiments, the radiation heater may be omitted. The atmosphere control device may be used throughout the process to avoid undesired scenarios such as, for example, powder oxidation. 
     The control computer  434  may be configured to control operations of the additive manufacturing apparatus  400 . In some embodiments, the control computer may be one or more computers  102  from  FIG. 2  or the computer  305  from  FIG. 3 . In some embodiments, the control computer  434  may be a controller built into or configured to interface with the additive manufacturing apparatus  400 . 
     Various embodiments disclosed herein provide for the use of a computer control system. A skilled artisan will readily appreciate that these embodiments may be implemented using numerous different types of computing devices, including both general purpose and/or special purpose computing system environments or configurations. 
     Examples of well-known computing systems, environments, and/or configurations that may be suitable for use in connection with the embodiments set forth above may include, but are not limited to, personal computers, server computers, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like. These devices may include stored instructions, which, when executed by a microprocessor in the computing device, cause the computer device to perform specified actions to carry out the instructions. As used herein, instructions refer to computer-implemented steps for processing information in the system. Instructions can be implemented in software, firmware or hardware and include any type of programmed step undertaken by components of the system. 
     A microprocessor may be any conventional general purpose single- or multi-chip microprocessor such as a Pentium® processor, a Pentium® Pro processor, a 8051 processor, a MIPS® processor, a Power PC® processor, or an Alpha® processor. In addition, the microprocessor may be any conventional special purpose microprocessor such as a digital signal processor or a graphics processor. The microprocessor typically has conventional address lines, conventional data lines, and one or more conventional control lines. 
     Aspects and embodiments of the inventions disclosed herein may be implemented as a method, apparatus or article of manufacture using standard programming or engineering techniques to produce software, firmware, hardware, or any combination thereof. The term “article of manufacture” as used herein refers to code or logic implemented in hardware or nontransitory computer readable media such as optical storage devices, and volatile or non-volatile memory devices or transitory computer readable media such as signals, carrier waves, etc. Such hardware may include, but is not limited to, field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), complex programmable logic devices (CPLDs), programmable logic arrays (PLAs), microprocessors, or other similar processing devices. 
     The control computer  434  may be connected to a laser scanning device  444 . The laser scanning device may include movable mirrors which can direct the laser beam received from a laser source into the building area. The laser source may also be a movable laser source, or it may also be the laser scanner provided in a stereolithography device  400 . The control computer  434  may further include software which controls the movement and functionality of the laser scanning system  444  according to the scanning pattern. As such, the control computer  434  may be configured to control the moment and activation of the laser scanning device according to the scanning pattern. 
     The control computer  434  may further be configured to interface with an image acquisition assembly  436 , such as to receive data/images from the image acquisition assembly  436 . The control computer  434  may further be configured to process the data/images to determine if errors have or will occur in the build process as described herein. The control computer  434  may further be configured to control when and how the image acquisition assembly  436  captures images. 
     The image acquisition assembly  436  may be configured to attach to, be integrated with, and/or sit separate from the additive manufacturing apparatus  400  and placed in such a position to monitor the building area  450  and/or the build surface. Further, the image acquisition assembly  436  may be configured to be stationary, or moveable (such as based on control signals received from the control computer  434 ) to monitor the building area  450  from different angles. 
     The image acquisition assembly  436  may be configured to acquire images of a calibration plate  448  or a build surface. More particularly, the image acquisition assembly  436  may be configured to acquire images of laser spots and/or other markings made on the calibration plate  448  or build surface by the scanning system  444 . 
     The image acquisition assembly  436  may include a camera, for example, an optical camera. The camera may be a commercial off-the-shelf (“COTS”) digital camera having sufficient resolution to capture spots and other markings on the calibration plate  448  or build surface in sufficient detail to calibrate the scanning device. In some embodiments, the image acquisition assembly is selected from an optical camera, a thermal imaging device, an IR camera, or a sensor that transfers other signals to visual signals. 
     A camera may take the form of a special purpose camera which is configured to capture spots reflecting from the surface of the calibration plate. In order to capture spots on the calibration plate, it may be necessary to position the camera so that it points to the area near the spot created by a scanner in the scanning system  444 . Accordingly, the image acquisition assembly  436  may also include a mount. In some embodiments, the mount may be a tilt-pan mount, which provides a range of motion sufficient to capture images in various locations on the calibration plate  448 . The mount may be driven by a motor. The motor may be configured to receive control signals from the control computer  434  which provide instructions for the movement of the camera  436 . In some embodiments, in addition to having a tilt-pan range of motion, the camera  436  may be further mounted on a projecting arm of a crane, commonly referred to as a jib. The jib may provide a further range of motion by allowing the camera not only to tilt and pan, but also to physically move its location in order to better acquire images of spots and/or markings on the calibration plate  448  or build surface. 
     Cushioning Structure 
     As discussed, certain embodiments herein provide a cushioning structure formed of a plurality of unit cells. In certain aspects, the cushioning structure includes a single type of unit cell of a single size. Forming such cushioning structures from such symmetrical unit cells may provide certain advantages such as for the ability to create an ordered array of repeating cells with predictable openings. In certain aspects, the cushioning structure includes a single type of unit cell, but having different sizes at different locations or portions in the cushioning structure. However, such structures may not provide as much predictability of openings or repeatability. In certain aspects, the size of the cushioning structure is selected based on a desired property (e.g., deformability, aesthetic, ventilation, etc.) of the cushioning structure. In certain aspects, a material used for the cushioning structure is also based on a desired property of the cushioning structure. 
     In certain aspects, the cushioning structure is a one-piece structure. A one-piece cushioning structure may comprise individual unit cells that are formed as a uni-component structure that is undivided and/or indivisible, for example, a structure that cannot be separated into individual components except by breaking or destroying elements of the structure. For example, a one-piece cushioning structure may comprise locations or portions having different geometries or sizes, but the portions cannot be separated except by breaking the one-piece structure apart. For example, the portions may be continuous with one another. One-piece cushioning structures may comprise a single material, or one-piece cushioning structures may comprise more than one material, wherein the materials are joined or fused together to form the one-piece cushioning structure. In some embodiments, a one-piece cushioning structure may be built by additive manufacturing in a single build session. The one-piece cushioning structure itself may have a coating placed thereon or be attached or coupled to other structures/objects. The one-piece cushioning structure may further form a uni-component structure along with one or more other objects/structures, such as additional one-piece cushioning structures. 
       FIGS. 5A-5C  show an example of a unit cell  500  with angled walls (e.g., faces) that can be used to form a cushioning structure, according to certain embodiments.  FIG. 5A  shows a first view of the unit cell  500 .  FIG. 5B  shows a second view of the unit cell  500  that is rotated approximately 20 degrees clockwise along an axis running vertical from the view shown in  FIG. 5A .  FIG. 5C  shows a third view of the unit cell  500  that is rotated approximately 90 degrees clockwise along an axis running vertical from the view shown in  FIG. 5A . 
     As shown, the unit cell  500  includes six triangular faces  502   a - 502   f.  In certain embodiments, the triangular faces  502   a - 502   f  have approximately the same size and shape as one another. Triangular faces  502   a  and  502   b,  as shown, are parallel to the same plane, and include surfaces that are within the same plane (also referred to as a central plane). As shown, the triangular faces  502   a  and  502   b  are connected at a node  504  that is central to unit cell  500 . In certain embodiments, the triangular faces  502   a  and  502   b  include outer edges  506   a  and  506   b,  respectively, that are opposite node  504 . In certain embodiments, outer edges  506   a  and  506   b  are parallel to one another. 
     Each of the triangular faces  502   a  and  502   b  further include two inner edges  508 . In certain aspects, the two inner edges of  508  of triangular face  502   a  align with the two inner edges of  508  such that they form two contiguous lines formed approximately as an “X.” 
     Triangular faces  502   c  and  502   d  are also connected to node  504 . In certain embodiments, the triangular faces  502   c  and  502   d  include outer edges  506   c  and  506   d,  respectively, that are opposite node  504 . In certain embodiments, outer edges  506   c  and  506   d  form an approximately 90 degree angle to one another, for example in a plane perpendicular to the central plane including surfaces of triangular faces  502   a  and  502   b.  Outer edges  506   c  and  506   d  intersect at a node. Further, in certain embodiments, outer edge  506   c  is perpendicular to outer edge  506   a,  and outer edge  506   d  is perpendicular to outer edge  506   b.  Outer edge  506   c  intersects with outer edge  506   a  at a node, and outer edge  506   d  intersects with outer edge  506   b  at a node. One inner edge  508  of triangular face  502   c  is shared with one inner edge  508  of triangular face  502   a.  Further, one inner edge  508  of triangular face  502   d  is shared with one inner edge  508  of triangular face  502   b.  The remaining inner edge of each of triangular faces  502   c  and  502   d  is shared. As shown, the triangular face  502   c  and triangular face  502   d  are positioned with respect to the central plane including surfaces of triangular faces  502   a  and  502   b  such that they form a pyramid like structure (an example of a protruding structure) with respect to the central plane. The pyramid like structure is a convex structure from one side of the central plane, and a concave structure from the opposite side of the central plane. 
     Triangular faces  502   e  and  502   f  are similar to triangular faces  502   c  and  502   d.  However, triangular faces  502   e  and  502   f  share different inner edges with triangular faces  502   a  and  502   b,  respectively, than triangular faces  502   c  and  502   d.  Further, triangular faces  502   e  and  502   f  form a pyramid like structure (an example of a protruding structure) that is convex on a side of the central plane that triangular face  502   c  and triangular face  502   d  form a concave structure, and that is concave on a side of the central plane that triangular face  502   c  and triangular face  502   d  form a convex structure. 
     As shown, the triangular faces  502   a - 502   f  of unit cell  500  form angled walls with respect to one another. Advantageously, the structure of unit cell  500  including its angled walls allows multiple unit cells  500  to be arranged into a cushioning structure. The angled walls of the unit cell  500  advantageously provide the ability for the unit cell  500  to bend to absorb forces, and can be configured in an array which forms a cushioning structure with openings that are not in a straight line and further add to the cushioning effect of the cushioning structure. In certain aspects, each of the walls/faces of the unit cell  500  have a substantially same thickness. 
     Though  FIGS. 5A-5C  show unit cells with angled walls having triangular faces, and pyramid like structures on either side of a central plane, and certain embodiments are described with respect to such unit cells with angled walls, unit cells with angled walls having other shaped faces, such as other geometric shapes, curved shapes, etc., may similarly be used with the embodiments set forth herein. A unit cell with angled walls in certain aspects comprises a unit cell with one or more protruding structures, one or more faces parallel to a central plane, and where at least one of the protruding structures comprises a wall that is at an angle to the central plane. In certain aspects, non-curved walls may be preferable to curved walls as faces as certain points on the curved walls may not be self-supporting during the additive manufacturing process in that they cannot be built without additional support structures to prevent deformation. In contrast, non-curved walls can be configured so that the whole plane comprising the non-curved wall is self-supporting. Further, though unit cell  500  is shown as having two protruding structures that protrude or jut from a central plane on two sides, a unit cell may only have one such protruding structure from one side of the unit cell, while the remainder of the unit cell can be the flat central plane. In certain aspects, wherein the unit cell includes two protruding structures, the protruding structures have a same shape. In certain aspects, the protruding structures have different shapes. 
     For example,  FIGS. 5D-5F  illustrate another example unit cell  520  having curved faces instead of triangular faces. As shown, the unit cell  520  includes a central plane  522  formed of two faces  524 . The unit cell  520  further includes protruding structures  526  and  528 , formed of curved faces, that protrude from opposite sides of central plane  522 . A bottom edge and top edge of the unit cell  520  are perpendicular to the central plane  522 . In another example,  FIGS. 5G-5I  illustrate an example unit cell  530  also having curved faces. As shown, the unit cell  530  includes a central plane  532  formed of two faces  534 . As shown, the central plane  532  is formed at an angle other than being perpendicular to the bottom edge and top edge of the central plane  532 . The unit cell  530  further includes protruding structures  536  and  538 , formed of curved faces, that protrude from opposite sides of central plane  532 , but at an angle other than perpendicular to the central plane  532 . 
     A unit cell with angled wall may further comprise other configurations. For example,  FIGS. 5J-5L  illustrate another example unit cell  540 . As shown, the unit cell does not include faces on a central plane. However, unit cell  540  comprises triangular faces, and protruding structures  544  and  546  that connect at a node. In certain aspects, protruding structures  544  and  546  are symmetrical across a plane that passes through the node. As shown, each of the protruding structures  544  and  546  is formed of four triangular faces. Each of the protruding structures  544  and  546  are further convex from the same side of the unit cell  540 , and concave from an opposite side of the unit cell  540 . Each of the protruding structures  544  and  546  comprises two edges that are shared with protruding structures  547  and  548 , respectively. In certain aspects, protruding structures  547  and  548  are symmetrical across a plane that passes through a node where protruding structures  547  and  548  couple. As shown, protruding structures  547  and  548  form an X shape. A triangular face  549  is located on one side of the X shape. 
     In another example,  FIGS. 5M-5O  illustrate another example unit cell  550 . As shown, the unit cell does not include faces on a central plane. However, unit cell  550  comprises triangular faces, and protruding structures  554  and  556  that connect at a node. As shown, protruding structure  554  comprises four triangular faces, while protruding structure  556  comprises three triangular faces. Each of the protruding structures  554  and  556  are further convex from the same side of the unit cell  550 , and concave from an opposite side of the unit cell  550 . Each of the protruding structures  554  and  556  coupled to an additional structure  559  as shown. 
       FIGS. 6A-6C  illustrate an example of a cushioning structure  600  formed of a plurality of unit cells  500  rotated to varying degrees. In particular, cushioning structure  600  includes a plurality of unit cell  500  arrayed in two dimensions (e.g., aligned as rows and columns) and may be referred to as a 2D cushioning structure. As shown, all the unit cells  500  are oriented in the same direction in cushioning structure  600  and aligned. Orienting the one or more unit cells  500  in the same direction may provide enhanced cushioning effect. In other embodiments, one or more unit cells  500  of cushioning structure  600  may be oriented in different directions from one another. 
     As shown, unit cells  500  are coupled to adjacent unit cells at one or more nodes and/or or along one or more shared edges. For example, unit cell  500   a  is an interior unit cell  500  that is fully coupled at all side to additional unit cells  500 . For example, unit cell  500   a  shares a node at the intersection of outer edges  502   a  and  502   e  with additional unit cells. Further, unit cell  500   a  shares a node at the intersection of outer edges  502   b  and  502   f  with additional unit cells. Unit cell  500   a  shares a node at the intersection of outer edges  502   a  and  502   c  with additional unit cells. Further, unit cell  500   a  shares a node at the intersection of outer edges  502   b  and  502   d  with additional unit cells. Unit cell  500   a  further shares its outer edge  502   f  with an additional unit cell. Unit cell  500   a  further shares its outer edge  502   c  with an additional unit cell. Therefore, in certain embodiments, four nodes and two edges of an interior unit cell  500  are shared with other unit cells in a 2D cushioning structure. 
     Some unit cells, such as unit cell  500   x,  may be exterior unit cells  500  that are not fully coupled at all sides to additional unit cells  500 , and therefore may have fewer nodes and/or edges shared with additional unit cells  500  than unit cell  500   a.    
     As shown, the unit cells  500  of cushioning structure  600  form perforations or openings  602 . The openings  602 , in some embodiments, are shaped as parallelograms when the cushioning structure  600  is in an undeformed state, such as when an external force is not applied to cushioning structure  600 . In certain aspects, the openings  602  provide fluid movement (e.g., air movement) through the cushioning structure  600 , such as for ventilation. 
     In certain embodiments, each unit cell  500  in cushioning structure  600  may be characterized as forming at least one inlet opening and at least one outlet opening. In certain embodiments the angled walls of a unit cell  500  may be curved, instead of straight as shown. In certain aspects, a 3D cushioning structure may be formed by stacking or layering 2D cushioning structures together. For example,  FIGS. 7A and 7B  illustrate 3D cushioning structure  700  formed as a stack of cushioning structures  600 . 
     For example, a first plurality of unit cells  500  may be arrayed in a 2D cushioning structure  600  in an x-y plane, and then a second plurality of unit cells  500  may be arrayed in a second 2D cushioning structure  600  in a different x-y plane stacked upon the first plurality of unit cells to form 3D cushioning structure  700 . In certain embodiments, each unit cell  500  in a first 2D cushioning structure  600  may have the same orientation as all other unit cells in the first 2D cushioning structure  600 . In a second 2D cushioning structure  600 , each unit cell may also have the same orientation as all other unit cells in the second 2D cushioning structure  600 , but may have a different orientation from the unit cells in the first 2D cushioning structure  600 . 
     In certain aspects, when force is applied to 2D cushioning structure  600  (e.g., and similarly cushioning structure  700 ), the cushioning structure  600  deforms, thereby providing a cushioning effect. For example, as shown in  FIG. 6D , a force can be applied in the direction of arrow  650  to the cushioning structure  600  aligned as shown in  FIG. 6A , thereby deforming the cushioning structure  600  to resemble, for example, the cushioning structure  600  as shown in  FIG. 6D . As shown, the deformation causes the openings  602  to deform from the previous parallelogram like shape. The force direction of arrow  650  may be considered as a force applied parallel to the openings  602  of the cushioning structure  600 , and the cushioning structure  600  provides a significant cushioning effect from force in such a direction due to the shape and design of cushioning structure  600 . 
       FIGS. 6E-6H  further shows a force applied to cushioning structure  600  in the direction of arrow  660  at an angle considered as perpendicular to the openings  602  of the cushioning structure  600 . As shown, the force causes the cushioning structure  600  to compress from the structure shown in  FIGS. 6E and 6F  to the structure shown in  FIGS. 6G and 6H , but the cushioning structure  600  does not bend and deform the openings  602  like shown in  FIG. 6D . Accordingly, the cushioning structure  600  may provide less of a cushioning effect for force in the direction of arrow  660  than for in the direction of arrow  650 . For example, the deformation may be limited by the walls of the unit cells  500  which are parallel to the direction of the force. Accordingly, in certain aspects, the cushioning structure can be oriented in an object so that the openings  602  are parallel to the direction in which the most cushioning effect is desired. 
     In certain embodiments, objects may include one or more 2D or 3D cushioning structures as discussed herein. The one or more 2D or 3D cushioning structures may be separable from the rest of the object. The one or more 2D or 3D cushioning structures may be formed as a one-piece structure as part of the object. A one-piece structure may comprise individual parts (e.g., such as the one or more 2D or 3D cushioning structures) that are fastened together, for example, by fastening means such as screws, bolts, or adhesives. A one-piece structure may comprise parts added to an existing structure. Alternatively, a one-piece structure may comprise a uni-component structure that is undivided and/or indivisible, for example, a structure that cannot be separated into individual components except by breaking or destroying elements of the structure. One-piece structures may comprise a single material, or one-piece structures may comprise more than one material, wherein the materials are joined or fused together to form the one-piece structure. In some embodiments, a one-piece structure may be built by additive manufacturing in a single build session. 
     In certain embodiments, where the object includes multiple 2D or 3D cushioning structures, the different 2D or 3D cushioning structures may be referred to as different zones of the object. Zones may be located adjacent to one another or may be stacked in layers. A zone may comprise an array of the same unit cells in the same orientation. In certain aspects, different zones may have the same unit cells in the same orientation, size, and/or shape. In certain aspects, different zones may have different unit cells in different orientations, sizes, and/or shapes. 
     Footwear 
     As discussed, one type of object that can include one or more 2D or 3D cushioning structures as discussed herein comprises footwear, such as a shoe or a ski boot liner. For example, a footwear can include a hollow shell and the one or more 2D or 3D cushioning structures inside the hollow shell. In certain embodiments, different zones of the footwear include different 2D or 3D cushioning structures having different orientation, size, and/or shape to accommodate different cushioning or support requirements for footwear corresponding to the locations of the zones. 
     For example,  FIG. 8  illustrates a view of an exterior structure of a shoe. In particular, in  FIG. 8  the hollow shell  800  of the shoe is visible, but not the one or more 2D or 3D cushioning structures inside the hollow shell  800 . The shoe includes a plurality of zones (not shown) in hollow shell  800 . As discussed, each of the different zones may have different cushioning or support requirements. 
       FIG. 9  illustrates one or more 2D or 3D cushioning structures  900  inside the hollow shell  800 . For example,  FIG. 9  illustrates the one or more 2D or 3D cushioning structures  900  in a similar orientation as a top view of hollow shell  800 . As shown, the one or more 2D or 3D cushioning structures  900  correspond to different zones  905   a - 905   f  of the shoe of  FIG. 8 . In certain embodiments, the one or more 2D or 3D cushioning structures  900  have a different shape, size, and/or orientation at different zones  905   a - 905   f.    
       FIGS. 10A-10C  illustrate example see-through views of an example shoe in various positions.  FIG. 11  illustrates an example see-through view of an example shoe on the foot of a wearer, according to certain embodiments. 
     In certain embodiments, the one or more 2D or 3D cushioning structures are positioned/oriented in the hollow shell to provide cushioning effect in the desired orientation. For example, in certain embodiments, the openings formed by unit cells of the 2D or 3D cushioning structures are oriented perpendicular to the corresponding surface of the hollow shell so as to provide cushioning effect in the direction of a user&#39;s foot when placed in the footwear. 
     Object Design Method for Including Cushioning Structures 
     Certain embodiments herein provide a method of designing an object with one or more 2D or 3D cushioning structures.  FIG. 12  illustrates a flowchart of example operations  1200  for designing an object to include cushioning structures. 
     At block  1202 , a unit cell (e.g., size, orientation, shape, etc.) design is selected. For example, a unit cell of the design of unit cell  500  is selected. In certain embodiments, the design is selected from a library of designs on a computing device (e.g., automatically or by a user of the computing device) such as computing device  102 . 
     At block  1204 , the unit cells are stacked into an array in a digital model, such as to form a 2D or 3D cushioning structure as a digital model. In certain embodiments, the unit cells are stacked in an array by a computing device (e.g., automatically) such as computing device  102 . 
     Further, at block  1206 , a negative of the array in the digital model is generated as a negative digital model of the array. The negative digital model may be generated so as to include structure/material wherever there was no material corresponding to the array, and not include structure/material wherever there was material corresponding to the array. In certain embodiments, the negative of the array in the digital model is generated by a computing device (e.g., automatically) such as computing device  102 . 
     Continuing, at block  1208 , the negative of the array in the digital model is superimposed over a digital model of a solid structure corresponding to the object to be filled with cushioning structure instead of the solid structure (e.g., the hollow portion of a shell of a ski boot liner wherein the hollow portion is represented as a solid model instead of hollow). In certain embodiments, the negative of the array is aligned with the solid structure so that the expected forces on the resulting object are properly aligned.  FIG. 13  illustrates an example of a negative array  1300  superimposed over one of the zones  1305  (e.g., similar to a zone  905 ) of a solid structure representing a hollow shell of a ski boot liner.  FIG. 13A  illustrates a close up view of a portion of the negative array  1300 . In certain embodiments, the negative of the array in the digital model is superimposed over a digital model of the solid structure to be filled by a computing device (e.g., automatically) such as computing device  102 . 
     Further, at block  1210 , a Boolean subtraction of the digital model of the solid structure from the negative array is performed to remove any non-overlapping areas of the negative array with respect to the solid structure. The result is a negative array having a shape corresponding to the solid structure and superimposed over the solid structure. 
     Continuing, at block  1212 , a second Boolean subtraction of the negative array having a shape corresponding to the solid structure from the solid structure is performed. The result is the object with the cushioning structure.  FIG. 14  illustrates an example of the resulting object with the cushioning structure. 
     The operations  1200  allow for a computationally less complex method to generate a design of an object with one or more 2D or 3D cushioning structures. Accordingly, operations  1200  reduce the computational complexity and processing power of a computing device to design an object with one or more 2D or 3D cushioning structures. 
     Scanning Method for Cushioning Structures 
     A further aspect of the present disclosure relates to a method for manufacturing a cushioning structure according to the embodiments herein. In some embodiments, the method may comprise receiving, in a computing device, a digital model of the cushioning structure. 
     The method may further comprise the steps of scanning the layers of the cushioning structure. The layers of the cushioning structure may be oriented so that a scanning pattern used for the layers includes long continuous vectors for scanning that do not require turning on and off of the laser/scanning device during scanning of different locations, thereby more efficiently generating the cushioning structure. For example, the shape of cushioning structures  600  and  700  may be conducive to using long continuous vectors. 
     For example, scanning may comprise building cross-sectional layers of the cushioning structure by moving an extruder containing build material or by applying either an energy source or chemicals to a build material along a scan pattern. Scan patterns may comprise at least one of a contour, hatch, outline, corner, fill, jump, or other feature of the cross-sectional layer built by AM. In some embodiments, scan patterns may vary in at least one of the number of hatch lines, the space between hatch lines, the shape of the overall scan pattern, and more. In some embodiments, the scan patterns comprise long continuous vectors. 
     Every cross section in the cushioning structure may vary in scan pattern and orientation from the cross sections immediately underlying and overlying it. Alternatively, in some embodiments, every two or more adjacent cross sections may have the same scan pattern and orientation as each other, while the next cross section in the z direction (either immediately underlying or overlying) has a different scan pattern and orientation. Two or more cross sections may form a stack of cross sections, so that variation arises between stacks but not between individual cross sections. 
     Any combination of cross sections or stacks of cross sections may be configured in either a random or non-random pattern in which the combination of different scan patterns and different orientations collectively lead to in a variation in openings. 
     In the cross sections of the cushioning structure, variation in scan patterns between cross sections may comprise variation in length of lines, number of lines, spacing between lines, thickness of lines, pattern in a cross section, geometric shapes traced by scan patterns, orientation, and/or more. 
     It will be apparent to those skilled in the art that various modifications can be made in form and detail to the above-described example embodiments of the present disclosure without departing from the spirit or scope of the invention. Thus, it is intended that the present disclosure covers all such modifications provided they fall within the scope of the appended claims and their equivalents. The specifications and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.