WO2023146538A1

WO2023146538A1 - Self-supporting porous structures

Info

Publication number: WO2023146538A1
Application number: PCT/US2022/014389
Authority: WO
Inventors: Nathan Eric SHIRLEY; Mary Louise Gray BAKER; Ronnie George PARSONS; Jonathan Fernando CORTES-RODRIGUEZ
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2022-01-28
Filing date: 2022-01-28
Publication date: 2023-08-03

Abstract

In some examples, a tool for manufacturing a part includes a self-supporting porous structure including a layer including a plurality of pores through which a liquid associated with a fibrous slurry to form the part flows. The self-supporting porous structure further includes a support body and an interconnect structure to interconnect the support body to the layer. The interconnect structure includes curved support members that engage portions of the layer. The layer, the support body, and the interconnect structure are integrally formed.

Description

SELF-SUPPORTING POROUS STRUCTURES

Background

[0001 ] Molded fiber manufacturing uses molded fiber (also referred to as a molded pulp) to manufacture products. The molded fiber can include cellulose fibers, which can be made from recycled paper, cardboard, and so forth. Examples of products that can be manufactured using molded fiber manufacturing include trays, plates, containers, or other products.

Brief Description of the Drawings

[0002] Some implementations of the present disclosure are described with respect to the following figures.

[0003] FIG. 1 is a schematic diagram of a tool that includes a self-supporting porous structure, in accordance with some examples.

[0004] FIG. 2 is a block diagram of a process of building a tool according to some examples.

[0005] FIG. 3 is a schematic sectional view of a portion of a digital representation of a tool that includes a support body and an interconnect structure, according to some examples.

[0006] FIG. 4 is a schematic top view of a portion of the digital representation of the tool that includes the support body and the interconnect structure, according to some examples.

[0007] FIG. 5 is a schematic bottom perspective view of a portion of the digital representation of the tool that includes the support body, the interconnect structure, and a layer with pores, according to some examples.

[0008] FIG. 6 is a flow diagram of a process according to some examples. [0009] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings.

Detailed Description

[0010] In the present disclosure, use of the term "a," "an," or "the" is intended to include the plural forms as well, unless the context clearly indicates otherwise. Also, the term "includes," "including," "comprises," "comprising," "have," or "having" when used in this disclosure specifies the presence of the stated elements, but do not preclude the presence or addition of other elements.

[0011 ] A molded fiber manufacturing process uses a fibrous slurry including cellulose fibers suspended in a liquid, such as water. Mold tools are immersed in a tank filled with the fibrous slurry. The mold tools include a form and a screen. The form supports the screen, which defines a target shape of a product to be manufactured by the molded fiber manufacturing process. In some prior examples, the form and the screen are separate from one another such that the screen and the form are separate mold tools.

[0012] A suction device can draw the fibrous slurry onto a surface of the screen, which has small pores. The liquid in the fibrous slurry is drawn through the pores of the screen, and the liquid exits through openings in the form (which can be a lattice) to a plenum. The remaining portion of the fibrous slurry takes the shape of the screen. In some molded fiber manufacturing processes, a transfer tool (another mold tool) can then be used to transfer the part away from the screen, and the transfer tool can move the part to another location for drying, such as in an oven or another location where heat can be applied to the part, or the part can be air dried. [0013] The form, screen, and transfer tool are examples of mold tools that are used as part of a molded fiber manufacturing process. In other examples, molded fiber manufacturing processes can employ different techniques and mold tools.

[0014] A screen may be relatively thin and thus fragile. As a result, handling of the screen during molded fiber manufacturing may cause damage to the screen. Additionally, a screen can be damaged through regular repeated use, as the suction forces involved can be substantial, which can be sufficiently large to break or damage the screen during use. In addition, screens have to be used with forms that support the screens. Making separate screens and forms increases the manufacturing time associated with making tools for molded fiber manufacturing. Also, the separate tools (screens, forms, and transfer tools) have to be separately inspected and checked for quality assurance, which adds to the time associated with making the tools. Moreover, using multiple separate molded tools means that tolerances between the molded tools have to be tightly controlled to ensure that the molded tools can fit together.

[0015] In accordance with some implementations of the present disclosure, a self-supporting screen can be built that has its own support structure. The self- supporting screen does not have to be used with a separate form, which reduces the quantity of tools used in molded fiber manufacturing. In other examples, a transfer tool with a porous structure can also be integrally formed. The porous structure of the transfer tool allows for enhanced dewatering of a part built using molded fiber manufacturing. A "self-supporting" porous structure (e.g., a screen, form, etc.) is a porous structure that does not rely on a separate structure to provide support for the porous structure so that the porous structure does not bend or otherwise deform by an extent such that the porous structure is damaged.

[0016] As used here, a "tool" is a component that is used to build a physical part.

[0017] FIG. 1 is a schematic sectional view of a tool 100 that can be used for manufacturing a part, such as with molded fiber manufacturing. The tool 100 includes a self-supporting porous structure 102 that includes a layer 104 that includes multiple pores 106 through which a liquid flows, where the liquid is associated with a fibrous slurry to form the part. The self-supporting porous structure 102 further includes a support body 108 and an interconnect structure 110 that interconnects the support body 108 to the layer 104.

[0018] As used here, a "layer" can refer to a relatively thin structure, such as in the form of a sheet, a film, and so forth. Although FIG. 1 show the layer 104 as being generally planar, it is noted that the layer 104 can have any of various different shapes depending upon a part (e.g., an egg carton, a container, etc.) that is to be formed using the tool 100.

[0019] The support body 108 has a rigidity and thickness that is greater than that of the layer 104. For example, the support body 108 can be more than twice as rigid as the layer 104, or more than five times as rigid as the layer 104, or more than 10 times as rigid as the layer 104, and so forth. The support body 108 can have a generally rectangular cross-sectional profile, or a curved profile, or a profile of any other shape. The support body 108 is used to support the layer 104, which can protect the layer 104 from damage due to handling, use in molded fiber manufacturing, and so forth. For example, the support body 108 can have a grid structure, including a lattice or ribs to provide a target rigidly, which can provide adequate support for the layer 104 to withstand a large suction force to protect the layer 104 from damage or breakage. As explained further below, the support body 108 has flow channels to improve dewatering performance, which can reduce the likelihood of clogging due to powders or other materials used during a build operation.

[0020] In some examples, the layer 104 can be a screen used in molded fiber manufacturing. In other examples, the layer 104 can be part of a transfer tool used in molded fiber manufacturing.

[0021] The interconnect structure 110 includes curved support members 112 that engage a lower surface 104-1 of the layer 104 in the view shown in FIG. 1 . If the tool 100 is in a different orientation, then the lower surface 104-1 can be an upper surface (such as when the tool 100 is upside down), or a diagonal surface, a vertical surface, and so forth for other orientations of the tool 100.

[0022] A "curved" support member 112 refers to a support member having at least some portion that is curved.

[0023] By using curved support members 112, each support member 112 projects in a normal direction from the surface of the layer 104 for a specified distance, before extending towards the nearest grid support (e.g., in the form of a base 112-1 ). In this manner, a minimum space can be defined between the pores 106 of the layer 104 and the curved support members 112 to ensure that any fiber materials that have passed through the pores 106 can be removed from the tool 100.

[0024] In some examples, each curved support member 112 includes a base 112-1 that sits on an upper surface 108-1 of the support body 108. Each curved support member 112 may include branches 112-2 that extend from the base 112-1. Tip portions of the branches 112-2 engage the lower surface 104-1 of the layer 104, when viewed in the orientation shown in FIG. 1 . In some examples, the branches 112-2 can grow in thickness (e.g., grow in diameter or width) from where the branches 112-2 touch the lower surface 104-1 of the layer 104 to the base 112-1 , and further, the base 112-1 can have a thickness that is greater than thicknesses of the branches 112-2. For example, the tip portions of the branches 112-2 can have thicknesses in the range between 0.1 and 1 millimeter (mm), and can grow in thickness up to between 1 and 10 mm as the branches 112-2 extend downwardly to the base 112-1. The base 112-1 can in turn be thicker (e.g., greater than 5 mm) than the branches 112-2.

[0025] The branches 112-2 can include curved branches as well as branches having other shapes, including straight branches, and/or branches of more complex shapes. A branch with a more complex shape can have a portion that is curved and another portion that is straight. In some examples, a curved support member 112 may have just one branch. [0026] The tool 100 can be used in molded fiber manufacturing, in which a fibrous slurry including cellulose fibers is suspended in a liquid. During the molded fiber manufacturing process, a suction device can draw the fibrous slurry onto an upper surface 104-2 of the layer 104.

[0027] The self-supporting porous structure 102 can be built using an additive manufacturing process. By using an additive manufacturing process, to build the self-supporting porous structure 102, the different portions of the self-supporting porous structure 102, including the layer 104, the interconnect structure 110, and the supporting body 108 can be integrally formed together. Components are "integrally" formed together if the components are formed as a one-piece structure where the components are already connected to each other, such that a separate attachment/connection process does not have to be applied to connect the components together.

[0028] Additive manufacturing machines produce three-dimensional (3D) objects by accumulating layers of build material, including a layer-by-layer accumulation and solidification of the build material patterned from digital representations of physical 3D objects to be formed. An additive manufacturing machine can also be referred to as a 3D printing system (e.g., 3D printer). Each layer of the build material is patterned into a corresponding part (or parts) of the 3D object, based on application of a liquid agent to selected portions of the layer, followed by a further processing (e.g., heating) of the layer after the liquid agent is applied. In other examples, selective laser sintering (SLS), stereolithography (SLA), or other 3D printing processes/machines can be employed.

[0029] FIG. 2 shows an example process of building the tool 100 according to some examples. A script 202 (or another type of program) is used to create a digital representation 204 of the tool 100 with the self-supporting porous structure 102. In some examples, the digital representation 204 is in the form of a computer-aided design (CAD) file or another type of representation. The digital representation 204 is provided as an input to an additive manufacturing machine 206. [0030] The additive manufacturing machine 206 builds the tool 100 on a layer-by- layer basis. In the additive manufacturing process performed by the additive manufacturing machine 206, a first layer of build material (e.g., powdered build material such as powdered polymer, powdered metal, or any other material used to form the tool 100) is deposited onto a build bed of the additive manufacturing machine 206, and the first layer of build material is then processed (a liquid agent applied, heat applied, etc.) according to a slice of the digital representation 204, where the slice corresponds to the first layer of build material. Once the first layer of build material has been processed, a subsequent layer of build material is formed on the previously processed layer of build material, and the subsequent layer of build material is processed using another slice of the digital representation 204. The foregoing is repeated until the tool 100 is built according to the digital representation 204.

[0031] The script 202 creates the digital representation 204 based on an input file 208 (or multiple input files). The file 208 can include various information, including information describing the geometry to be built. The "geometry" can refer to the outer contour or profile of the tool 100 (e.g., geometry for the support body 108, geometry for the layer 104 with pores 106, etc.). In addition, the input file 208 can include information relating to the mesh that represents the support body 108 of the tool 100, such as a grid spacing parameter representing a space between beams of the support body 108, a beam thickness representing a thickness of the beams of the support body 108, etc. The input file 208 also includes information relating to the layer 104 that includes the pores 106, such as a size of each pore 106, a pitch between the pores 106, etc. The input file 208 can also include information relating to an overall outer envelope of the tool 100 (e.g., information pertaining to a master surface of the tool to be made, a frame including sidewalls, a space of the volume of the support body 108, etc.). In further examples, the input file 208 may also include information indicating regions of the tool 100 to perforate, such as for screws or other fasteners. As further examples, the input file 208 may include information for logos or other labels to be added to the tool 100. [0032] The script 202 builds a structural Voronoi cube grid (representing the support body 108) according to the information relating to the mesh included in the input file 208. A Voronoi cube grid is based on a Voronoi diagram that partitions a plane into regions corresponding to seeds. The Voronoi diagram includes Voronoi cells containing respective points. A Voronoi cell includes all points of the plane that is closer to a respective seed than any other seed. A Voronoi cube grid is a three- dimensional arrangement of the Voronoi diagram.

[0033] Although reference is made to a Voronoi cube grid in some examples for creating the support body 108, in other examples, other types of grid structures can be employed. In other examples, other grid structures can include a surface lattice (which is a lattice generated from trigonometric equations that control a shape, size, and density of the lattice), a strut lattice (which includes a series of rod-like structures that are connected in different orientations to form different unit cells of the lattice, or a planar based lattice (which includes structures created as a periodic pattern in a 2D plane and then extruded in a direction to create a 3D structure).

[0034] An initial volume for the grid (corresponding to the support body 108) is defined by the input file 208. The script 202 strips away a portion of the initial volume where the interconnect structure 110 is to be formed. The portion of the initial volume stripped away can be the space corresponding to where the interconnect structure 110 is to be formed. The remaining volume (after stripping away the portion from the initial volume) is populated with an array of points, which can be a rectangular grid array of points in some examples. In other examples, any other point cloud can be employed. The remaining volume is fractured by the script 202 using the points in a 3D Voronoi fracture, which fractures an object using the Voronoi diagram to form fragments that make up the Voronoi cells. The script 202 extracts the edges of the fracture, which become the skeleton for the base grid of the support body 108.

[0035] The base grid is spaced apart from the layer 104 with pores, which leaves a gap between the base grid and the layer. The structural Voronoi cube grid defines a lattice that forms the support body 108. In other examples, other types of rigid grids for the support body 108 can be generated by the script 202. The gap between the grid and the layer is where the interconnect structure 110 is formed.

[0036] On the side of the layer 104 that is to connect with the base grid, the script 202 populates points in a way that the points lie between the pores 106 and have a controlled spacing adequate to support the screen. The script 202 draws lines from these points on the side of the layer 104 perpendicular to the layer 104, before using a branching algorithm to join with neighboring branches before finally finding the shortest path to a neighboring portion of the base grid. In some cases, the script 202 smooths the branch structures for a more natural flowing curve.

[0037] Once the base grid and branches have been drawn as lines and smoothed out, the script 202 thickens the branches by populating spheres along the extents of the branches. This forms the base 112-1 and the branches 112-2 of the curved support members 112 so that the base 112-1 and the branches 112-2 remain strong and rigid along most of their lengths. The radius of each sphere is calculated dynamically based on its distance from the surface of the layer 104 using a ramp defined by a curve, allowing the thickness to taper off from the base 112-1 that sits on the support body 108, before contacting the layer 104 so that no pores 106 are obstructed in some examples.

[0038] Tapering off each branch 112-2 causes a width of the branch 112-2 closer to the base 112-1 to be greater than the width of the tip portion of the branch 112-2 that contacts the layer 104. Reducing the width of the branch 112-2 closer to the layer 104 can avoid obstructing the pores 106 so that liquid flow through the pores 106 is not restricted due to obstruction caused by presence of portions of the branches 112-2.

[0039] In some examples, the tip portions of the branches 112-2 contact the lower surface 104-1 of the layer 104 so that the tip portions of the branches 112-2 are away from the pores 106. The branches 112-2 (or more specifically the tip portions of the branches 112-2) being "away" from the pores 106 means that the branches 112-2 do not obstruct any of the pores 106 relating to liquid flow through the pores 106. In such examples, the tip portions of the branches 112-2 contact solid portions of the layer 104 (and do not engage the pores 106). A "solid portion" of the layer 104 refers to a portion of the layer 104 that does not include a pore 106. The pores 106 are formed in the solid portions.

[0040] In other examples, the tip portions of some of the branches 112-2 may overlap with some pores 106 so that there may be some liquid flow obstruction. Although some obstruction may be acceptable in some examples, the script 202 seeks to reduce as much of the obstruction with the pores 106 as possible.

[0041 ] FIG. 3 is a schematic section view of a portion of a digital representation (e.g., 204) of the tool 100 according to some examples. FIG. 4 is a top view of a portion of the digital representation of the tool 100 according to some examples.

[0042] In each of FIGs. 3 and 4, a representation of the layer 104 with pores 106 is not shown. The support body 108 is in the form of a lattice, which can be based on a Voronoi cube grid or some other type of grid. The lattice of the support body 108 includes beams (horizontal beams, vertical beams, beams in other orientations) that define channels through the lattice. The channels allow for liquid flow through the support body 108. The channels of the lattice include first channels 302 running generally along a first direction, and second channels 304 (FIG. 4) that run in a second direction that intersects the first direction. The top view of FIG. 4 shows that the first channels 302 running in the first direction and the second channels 304 running in the second direction are generally perpendicular to one another. In other examples, the first channels 302 and second channels 304 can intersect at different angles.

[0043] The channels 302 and 304 of the support body 108 that run in multiple directions allows for liquid flow in multiple directions (cross-flow) through the channels 302 and 304. This improves dewatering performance during molded fiber manufacturing. In some examples, traditional forms used in molded fiber manufacturing have ribs that restrict liquid flow to one direction, which can reduce dewatering performance, or may be solid blocks of metal with holes drilled in them. [0044] The improved liquid flow provided by the channels 302 also reduce the likelihood of clogging during molded fiber manufacturing. The configuration of lattice forming the support body 108 reduces the likelihood that fiber is trapped in the support body 108.

[0045] As seen in FIGs. 3 and 4, each curved support member 112 can have many branches growing from a respective base. Moreover, note that the bases of multiple curved support members 112 can grow together, with branches extending from the bases that have grown together.

[0046] FIG. 5 is a schematic bottom perspective view of a portion of a digital representation of the tool 100, with the layer 104 included. FIG. 5 shows engagement of branches 112-2 of the curved support members 112 with the lower surface 104-1 of the layer 104, such as at points 502. FIG. 5 also shows a relatively large quantity of pores (e.g., 504) in the layer 104.

[0047] In some examples, rigidity can be provided to the layer 104 with pores 106 (e.g., a screen, a transfer tool, etc.) due to the support body 108 and the interconnect structure 110 so that the part built in molded fiber manufacturing has improved part qualities. Also, the self-supporting porous structure of the tool 100 avoids having to provide mechanical fasteners such as clips, screws, welded connections, etc., in the center of the screen, which reduces complexity.

[0048] Building the tool 100 using an additive manufacturing process allows for features of the tool 100, such as pore sizes, spacings between pores, etc., to be more easily controlled (such as by setting these as variables in the input file 208 of FIG. 2.

[0049] Because of the integral nature of the tool 100, there are fewer components to handle, which means less components to break, clean, and coordinate. Also, because the components of the tool 100 are integrally formed by an additive manufacturing process, fit and tolerances between different components are no longer issues. Also, fasteners do not have to be used to attach components of the tool 100.

[0050] Building the tool 100 with integrated components also means that separate screens and forms do not have to be built, which saves on tool manufacturing time.

[0051 ] FIG. 6 is a flow diagram of a process 600 according to some examples. The process 600 forms a tool (e.g., 100 in FIG. 1 ) for use in molded fiber manufacturing of a part with a fibrous slurry. The process 600 includes integrally forming (at 602) a layer (e.g., 104 in FIG. 1) including a plurality of pores, a support body (e.g., 108 in FIG. 1 ), and an interconnect structure (e.g., 110 in FIG. 1 ) having curved support members (e.g., 112 in FIG. 1) that connect the layer to the support body, where the integrally formed layer, support body, where the interconnect structure provides a self-supporting porous structure useable in the molded fiber manufacturing, and where a liquid associated with the fibrous slurry is to flow through the plurality of pores.

[0052] In the foregoing description, numerous details are set forth to provide an understanding of the subject disclosed herein. However, implementations may be practiced without some of these details. Other implementations may include modifications and variations from the details discussed above. It is intended that the appended claims cover such modifications and variations.

Claims

What is claimed is:

1 . A tool for manufacturing a part, comprising: a self-supporting porous structure comprising a layer including a plurality of pores through which a liquid associated with a fibrous slurry to form the part flows, the self-supporting porous structure further comprising a support body and an interconnect structure to interconnect the support body to the layer, the interconnect structure comprising curved support members that engage portions of the layer, wherein the layer, the support body, and the interconnect structure are integrally formed.

2. The tool of claim 1 , wherein the layer, the support body, and the interconnect structure are integrally formed using an additive manufacturing process.

3. The tool of claim 1 , wherein the layer comprises a screen including the plurality of pores, the screen useable in molded fiber manufacturing of the part with the fibrous slurry.

4. The tool of claim 1 , wherein the curved support members are placed away from the plurality of pores.

5. The tool of claim 1 , wherein the curved support members of the interconnect structure contact solid portions of the layer, the plurality of pores being defined by the solid portions.

6. The tool of claim 1 , wherein the support body comprises a transfer tool useable in molded fiber manufacturing of the part with the fibrous slurry.

7. The tool of claim 1 , wherein the support body comprises liquid flow channels that cross one another.

8. The tool of claim 7, wherein the support body comprises a lattice defining the flow channels.

9. The tool of claim 1 , wherein the curved support members of the interconnect structure comprise a base connected to the support body and horns extending from the base, wherein respective tips of the horns engage respective portions of the layer away from corresponding pores in the layer.

10. A method of forming a tool for use in molded fiber manufacturing of a part with a fibrous slurry, the method comprising: integrally forming a layer comprising a plurality of pores, a support body, and an interconnect structure having curved support members that connect the layer to the support body, wherein the integrally formed layer, support body, and interconnect structure provide a self-supporting porous structure useable in the molded fiber manufacturing, wherein a liquid associated with the fibrous slurry is to pass through the plurality of pores.

11 . The method of claim 10, wherein integrally forming the layer, the support body, and the interconnect structure comprises using an additive manufacturing machine to print the layer, the support body, and the interconnect structure.

12. The method of claim 10, wherein the layer comprises a screen with the plurality of pores, the screen for use in the molded fiber manufacturing.

13. The method of claim 10, wherein the layer and the support body comprises a transfer tool for use in the molded fiber manufacturing.

14. A tool for manufacturing a part, comprising: an integral arrangement of a porous structure comprising a plurality of pores through which a liquid associated with a fibrous slurry to form the part flows, a support body comprising a lattice structure, and an interconnect structure that interconnects the porous structure and the support body, the lattice structure defining liquid channels in a plurality of different directions, wherein the interconnect structure comprises curved support members that engage portions of the layer.

15. The tool of claim 14, wherein the porous structure comprises a screen for use in molded fiber manufacturing of the part with the fibrous slurry.