WO2023282893A1

WO2023282893A1 - Fiber molding tool flow structures

Info

Publication number: WO2023282893A1
Application number: PCT/US2021/040660
Authority: WO
Inventors: Mary Louise Gray BAKER; Ronnie George PARSONS; Nathan Eric SHIRLEY; Lluis PARE BARNIOL; Jonathan Fernando CORTES-RODRIGUEZ
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2021-07-07
Filing date: 2021-07-07
Publication date: 2023-01-12

Abstract

In an example in accordance with the present disclosure, a fiber molding tool is described. The fiber molding tool includes a first surface that includes a first plurality of perforations and a second surface that includes a second plurality of perforations. A distribution of the second plurality of perforations on the second surface is independent of a distribution of the first plurality of perforations on the first surface. The fiber molding tool also includes a flow structure through a thickness of the tool such that a fluid is to flow from the first plurality of perforations, through the flow structure to the second plurality of perforations.

Description

FIBER MOLDING TOOL FLOW STRUCTURES

BACKGROUND

[0001] Fiber molding refers to an operation where a fibrous material such as recycled paper, cardboard, or other natural fibers are dispersed as a slurry. The slurry is compressed against a shaped screen and water is removed from the slurry leaving a hardened and shaped molded fiber product in a shape to match the screen. Examples of molded fiber products include, but are not limited to paper products such as paper plates, food containers, and protective packaging, such as for any variety of shipped goods. Once used, such products may be recycled, broken down into a slurry, and formed into new molded fiber products.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The accompanying drawings illustrate various examples of the principles described herein and are part of the specification. The illustrated examples are given merely for illustration, and do not limit the scope of the claims.

[0003] Fig. 1 is a block diagram of a fiber molding tool with side independent perforations, according to an example of the principles described herein;

[0004] Fig. 2 depicts a fiber molding die with a 3D-printed flow structure, according to an example of the principles described herein;

[0005] Fig. 3 is a flowchart of a method for generating a flow structure for a fiber molding tool, according to an example of the principles described herein; [0006] Fig. 4 depicts a cross-sectional view of a branched pathway flow structure, according to an example of the principles described herein;

[0007] Figs. 5A and 5B depict a lattice infill flow structure, according to an example of the principles described herein;

[0008] Fig. 6 depicts a cross-sectional view of a fiber molding tool flow structure, according to an example of the principles described herein;

[0009] Figs. 7A and 7B depict a lattice flow structure, according to an example of the principles described herein;

[0010] Fig. 8 depicts a cross-sectional view of a flow structure, according to an example of the principles described herein;

[0011] Fig. 9 is a flowchart of a method for generating a fiber molding tool flow structure, according to an example of the principles described herein; and [0012] Fig. 10 depicts a non-transitory machine-readable storage medium for generating a fiber molding tool flow structure, according to an example of the principles described herein.

[0013] 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

[0014] Fiber molding refers to an operation where a fibrous material such as recycled paper, cardboard, or other natural fibers are dispersed as a slurry. The slurry is compressed against a shaped screen and water is removed from the slurry leaving a hardened and shaped molded fiber product in a shape to match the shaped screen. Examples of molded fiber products include, but are not limited to paper products such as paper plates, food containers, and protective packaging, such as for any variety of shipped goods. Once used, molded fiber products may be recycled, broken down into a slurry, and formed into new molded fiber products. Accordingly, such products are desirable due to their recyclability and therefore reduced impact on the environment.

[0015] In general, a fiber molding die includes two components, a screen against which the fiber accumulates to make the pulped object, and a form tool that supports the screen. Both of these components include perforations through which the fluid from the slurry is drawn. In the case of the screen, the fluid flows from the slurry side to a side of the screen that sits against the form tool. In the case of the form tool, the fluid flows from the screen side to the plenum, i.e. , a region to where the fluid is drawn and retained.

[0016] In general, the formation of these fiber molding tools may be manual, complex, and cumbersome. For example, the screen may be made of a metal mesh that is hammered into place over a form tool. The form tool may be a machined metal block with holes drilled through. Accordingly, forming these fiber molding tools is labor intensive and may prevent the beneficial use of molded fiber products.

[0017] Moreover, the desired fluid flow through these components and a controlled thickness of the final molded fiber product, depends on the controlled placement and consistent density of perforations over the surface of the components. Maintaining an even density of perforations in areas of sharp curvature on the surface of the form tool and screen is a challenge as some spacing of holes may not be able to be maintained at sufficient density on both sides of the tool without collision of holes on the concave side. The collision of these holes on the concave side may cause structural weakness due to loss of material. The difficulty is exacerbated in narrow structures such as towers in form tools and screens. Accordingly, the present specification provides for the automated and additive manufacturing of such components to address these and other issues.

[0018] Specifically, additive manufacturing systems form a three-dimensional (3D) object through the solidification of layers of build material. Additive manufacturing systems make objects based on data in a 3D model of the object generated, for example, with a computer-aided drafting (CAD) computer program product. The model data is processed into slices, each slice defining portions of a layer of build material that are to be solidified. 3D objects may be formed using any variety of additive manufacturing systems including fusing agent-based systems, a binding agent-based system, selective laser sintering, selective laser melting, fused metal deposition, and stereolithography.

[0019] Specifically, the present specification describes a fiber molding tool, method, and machine-readable storage medium that place perforations on each side of the fiber molding tool (e.g., form tool or screen) independently from one another.

[0020] As used in the present specification and in the appended claims, the term “a number of” or similar language is meant to be understood broadly as any positive number including 1.

[0021] Turning now to the figures, Fig. 1 is a block diagram of a fiber molding tool (100) with side independent perforations, according to an example of the principles described herein. As described above, the fiber molding tool (100) is used to form a molded fiber product. In general, a fiber molding die includes two components, a screen against which the fiber accumulates to make the pulped object, and a form tool that supports the screen. As such, the fiber molding tool (100) may be either the form tool of the molded fiber die and/or the screen for the molded fiber die.

[0022] The fiber molding tool (100) may also be a transfer tool of the fiber molding die. The transfer tool refers to a tool that removes the molded fiber product from the screen following molding. In an example, the transfer tool includes a transfer form tool and a transfer screen separately.

[0023] In another example the transfer tool includes the transfer form tool and the transfer screen together. In this example, the transfer tool is in the form of the fiber molded product, but sits on an outside surface of the molded fiber product opposite from the side of the molded fiber product that forms against the screen and form tool. After fiber molding, the transfer tool fits to the molded fiber product and the direction of the vacuum is reversed to push the molded fiber product from the screen/form to the transfer tool. The transfer tool is then be used to deposit the molded fiber product on a belt or to otherwise transfer the molded fiber product throughout its manufacturing cycle. In this example, the fiber molding tool (100) is be the transfer tool of the molded fiber die.

[0024] Each of these components include perforations. In the case of the screen and form tool, fluid from the fluid slurry is drawn through these perforations. For example, in a fiber molding screen or form tool, a slurry of fibrous material and a fluid is on one side of the form tool and screen. Via vacuum pressure, the fluid is drawn in a direction such that the fibrous material of the slurry is compressed against the screen. As a screen is in a desired shape of a molded fiber object, the fibrous material conforming to the screen molds the product in the desired structure.

[0025] Accordingly, the fiber molding tool (100) includes a first surface (102) having a first plurality (104) of perforations and a second surface (106) having a second plurality (108) of perforations. In an example, the first surface (102) is be an entrance surface through which water enters the fiber molding tool (100) during a fiber molding operation and the second surface (106) is be an exit surface through which water exits the fiber molding tool (100) during the fiber molding operation. For a screen, the first surface (102) is be the surface in contact with the slurry of fibrous material and the second surface (106) is be the surface in contact with the form tool. For a form tool, the first surface (102) is be the surface in contact with the screen and the second surface (106) is be the surface in contact with the plenum.

[0026] As described above, each surface includes a plurality of perforations, which perforations are independent of one another. As used in the present specification and in the appended claims, the term “independent” means that a number, placement, shape, and size of the first plurality (104) of perforations is different than a number, placement, shape, and size of the second plurality (108) of perforations. For example, perforations of the first plurality (104) may not align with perforations of the second plurality (108).

[0027] As such, the fiber molding tool (100) includes a flow structure (110) extending through a thickness of the fiber molding tool (100) such that a fluid is to flow from the first plurality (104) of perforations, through the flow structure (110), and to the second plurality (108) of perforations. The figures that follow depict a variety of flow structures (110) that are generated between the first plurality (104) of perforations and the second plurality (108) of perforations. [0028] Fig. 2 depicts a three-dimensional fiber mold die (212) with a 3D- printed flow structure (Fig. 1, 110), according to an example of the principles described herein. As described above, the fiber molding tool (Fig. 1 , 100) to be fabricated may be a form tool (214) for the fiber molding die (212) or a screen (216) for the fiber molding die (212). As described above, the fiber molding die (212) filters material elements from a fluid. In some examples, the fluid may be water or another type of suitable fluid in which pulp material, e.g., paper, wood, fiber crops, bamboo, or the like, is mixed into a slurry (222). The material elements may be, for instance, fibers of the pulp material. In these examples, the sizes of the perforations are defined by the sizes of the fibers in the slurry. For instance, the perforations are sized to prevent or limit the flow of the fibers into the pores.

[0029] Fig. 2 depicts an example of the screen (216) having perforations (218-1, 220-1) and a form tool (214) also having perforations (218-2, 220-2).

The perforations (218-1 , 218-2) on the first side (Fig. 1 , 102) define the first plurality (Fig. 1 , 104) of perforations while the perforations (220-1 , 220-2) on the second side (Fig. 1 , 106) define the second plurality (Fig. 1 , 108) of perforations.

[0030] Fig. 2 depicts a cross-sectional side view of an example fiber molding die (212) that includes an example screen (216) and form tool (214). As shown, the screen (216) overlays the form tool (214). In an example, the form tool (214) is thicker than the screen (216) and is more rigid than the screen (216).

As such, the form tool (214) provides structural support for the screen (216).

The form tool (214) may be formed of a rigid material, such as a metal, a plastic, a ceramic, and/or the like.

[0031] As described above, the screen has first side perforations (218-1) and second side perforations (220-1). Similarly, the form tool (214) has first side perforations (218-2) and second side perforations (220-2). As described above, the first side perforations (218) on either fiber molding tool (Fig. 1 , 100) are independent from the second side perforations (220) on the fiber molding tool (Fig. 1 , 100). According to examples, the placement of the perforations (218, 220) in both the screen (216) and the form tool (214) is determined through packing of the digital ellipsoids discussed herein. The perforations (218, 220) may have circular cross-sections. In an example, the perforations (218-2, 220- 2) in the form tool (214) are larger in diameter than the perforations (218-1 , 220- 1) in the screen (216). While particular reference is made to perforations (218, 220) with circular cross sections, the perforations (218, 220) may have cross- sections of different shapes.

[0032] In operation, a vacuum, or reduced pressure, is be applied from a side of the form tool (214) opposite the screen (216) when the fiber molding die (212) is immersed in a fiber slurry (222) containing a material (224). As fluid in the fiber slurry (222) flows through the screen (216) and the form tool (214) as denoted by the arrows, the material (224) in the slurry (222) is accumulated and compressed onto the screen (216) and takes the shape of the screen (216). The material (224) pressed against the screen is then dried to form a molded fiber product in the shape of the screen (216)

[0033] Fig. 3 is a flowchart of a method (300) for generating a flow structure (Fig. 1 , 110), according to an example of the principles described herein. According to the method (300), a processor accesses (block 301) a digital model of a fiber molding tool (Fig. 1 , 100) to be fabricated. That is, the digital model of the fiber molding tool (Fig. 1 , 100) may be a three-dimensional (3D) computer model of the fiber molding tool (Fig. 1 , 100), such as a computer aided design (CAD) file, or other digital representation of the fiber molding tool (Fig. 1 , 100). In an example, the processor accesses the digital model of the fiber molding tool (Fig. 1 , 100) from a data store (not shown) or some other source. In some examples, the digital model of the fiber molding tool (Fig. 1 ,

100) is generated using a CAD application. That is, the CAD application is used to define the physical geometry of the digital model.

[0034] As described above, the digital model defines the geometry of the fiber molding tool (Fig. 1 , 100) to be fabricated and includes a first surface (Fig.

1 , 102) through which fluid is drawn through the fiber molding tool (Fig. 1 , 100). The processor determines (block 302) a distribution of a first plurality (Fig. 1 , 104) of perforations on the first surface (Fig. 1 , 102) of the fiber molding tool (Fig. 1 , 100). As described above, an even distribution of perforations over the first surface (Fig. 1 , 102) ensures uniform fluid flow through the fiber molding tool (Fig. 1 , 100) and uniform thickness of the molded fiber product.

[0035] In an example, the determination (block 302) of the distribution of the first plurality (Fig. 1 , 104) of perforations is done without user intervention other than providing the digital model. That is, a user may provide the digital model and the processor determines the distribution of the first plurality (Fig. 1 , 104) of perforations which will be overlaid on the digital model. That is, given a particular digital model and certain parameters such as a desired perforation size and spacing, the processor operates to determine the location of the first plurality (Fig. 1 , 104) of perforations on the first surface (Fig. 1 , 102). The processor determines the locations at which the perforations are to be formed in the fiber molding tool (Fig. 1 , 100) such that, for instance, the perforations are spaced evenly with respect to each other (or at other intended spacings) and/or at desired density levels to achieve intended flow rates through the perforations. In addition, the perforations may have any geometric shape such as circular, spherical, hexagonal, octagonal, and/or the like, and some of the perforations may have different shapes with respect to each other.

[0036] In an example, to determine (block 302) the distribution of the first plurality (Fig. 1 , 104) of perforations, the processor packs a plurality of digital ellipsoids to intersect a first surface (Fig. 1, 102) of the digital model of the fiber molding tool (Fig. 1 , 100), in which the digital ellipsoids have a certain spacing with respect to each other and certain diameters. As discussed in greater detail herein, the processor selects the diameters and packs the digital ellipsoids with respect to each other based on a curvature of the first surface (Fig. 1 , 102). The processor determines the locations on the first surface (Fig. 1 , 102) of the digital model at which the digital ellipsoids intersect the first surface (Fig. 1 , 102) and sets the determined locations as points on the first surface (Fig. 1 , 102) at which the perforations are to be formed. The processor removes the digital ellipsoids and adds digital representations of the perforations at the determined locations in the digital model such that, for instance, the digital model is employed in fabricating the fiber molding tool (Fig. 1 , 100) with the perforations positioned at the determined locations.

[0037] As such, the processor packs a plurality of digital ellipsoids to intersect the first surface (Fig. 1 , 102) of the digital model of the fiber molding tool (Fig. 1 , 100). The digital ellipsoids are digital representations of ellipsoids that are arranged with respect to the digital model of the fiber molding tool (Fig.

1 , 100) and may have sections that are circular or elliptical. In an example, the processor packs the digital ellipsoids such that the digital ellipsoids do not overlap with any other ones of the digital ellipsoids.

[0038] In an example, the processor determines (block 302) the distribution of the first plurality (Fig. 1 , 104) of perforations based on any number of criteria. For example, a thickness of the fiber molding tool (Fig. 1 , 100), a material of the fiber molding tool (Fig. 1 , 100), a radius of curvature of the fiber molding tool (Fig. 1 , 100), a desired thickness for the fiber molded product; and a material of the fiber molded product.

[0039] For example, the digital ellipsoids may be arranged, e.g., spaced from each other, based on a curvature of a first surface (Fig. 1 , 102) on which the digital ellipsoids intersect. For instance, the centers of the digital ellipsoids may be relatively closer to each other when the first surface (Fig. 1 , 102) is relatively flat and may be relatively farther apart from each other when the first surface (Fig. 1 , 102) is curved.

[0040] In an example, the processor generates the digital ellipsoids to have certain diameters. For example, the processor determines the diameters of the digital ellipsoids that result in the perforations being formed according to the intended density, e.g., a number of perforations per area unit of the first surface. A user and/or a CAD program may define the intended density according to, for instance, intended properties of the object.

[0041] In some examples, a similar operation is performed for the second surface (Fig. 1, 106). That is, the processor determines (block 303) a distribution of a second plurality (Fig. 1 , 108) of perforations on a second surface (Fig. 1 , 106) of the fiber molding tool (Fig. 1 , 100). That is, as described above, the processor places digital ellipsoids on the second surface (Fig. 1 , 106) based on any number of the aforementioned criteria. However, as described above, the distribution of the second plurality (Fig. 1 , 108) of perforations is determined independently of the determination of the distribution of the first plurality (Fig. 1 , 104). That is, a location, size, and/or shape of perforations of the first plurality (Fig. 1 , 104) has no bearing on the location, size, and/or shape of the perforations of the second plurality (Fig. 1 , 108). The independent determination of first and second pluralities of perforations provides for greater flexibility in defining the flow structure.

[0042] In an example, determining (block 303) the distribution of the second plurality (Fig. 1 , 108) of perforations includes extending a lattice structure from the first plurality (Fig. 1 , 104) of perforations towards the second surface (Fig. 1 ,

106). The lattice passages at the termination of the extension, which may be defined by a predetermined thickness setting in the digital model or otherwise set, define the second plurality (Fig. 1 , 108) of perforations. In this example, the passages in the lattice structure are sized and positioned to align with the first plurality (Fig. 1 , 104) of perforations. Additional detail regarding this example is provided below in connection with Fig. 7.

[0043] The method (300) also includes defining (block 304) a flow structure (Fig. 1 , 110) to extend between the first plurality (Fig. 1 , 104) of perforations and the second plurality (Fig. 1 , 108) of perforations through a thickness of the fiber molding tool (Fig. 1 , 100). With such a flow structure (Fig. 1 , 110) in place, fluid flows from the first plurality (Fig. 1 , 104) of perforations through the flow structure (Fig. 1 , 110) to the second plurality (Fig. 1 , 108) of perforations.

[0044] As described above, the flow structure (Fig. 1 , 110) is defined in any number of ways. For example, defining (block 304) a flow structure (Fig. 1 , 110) may include intersecting a lattice volume with a digital model of the fiber molding tool (Fig. 1 , 100). An example of such is depicted in Fig. 6.

[0045] In another example, defining (block 304) the flow structure (Fig. 1 ,

110) may include defining, for each perforation of the first plurality (Fig. 1 , 104) of perforations, a shortest path to the second surface (Fig. 1, 106) of the fiber molding tool (Fig. 1 , 100). An example of such is depicted in Fig. 8. [0046] In yet another example, defining (block 304) the flow structure (Fig. 1 , 110) may include defining branched pathways between the first plurality (Fig. 1 , 104) of perforations and the second plurality (Fig. 1 , 108) of perforations. An example of such is depicted in Fig. 4.

[0047] In any example, such a definition (block 304) of the flow structure (Fig. 1 , 110) may be performed without additional user intervention other than providing a digital model for the fiber molding tool (Fig. 1 , 100). In this example, a user provides the digital model and the processor defines (block 304) a flow structure (Fig. 1 , 110) which will be overlaid on the digital model.

[0048] The method (300) includes modifying (block 305) the digital model of the fiber molding tool (Fig. 1 , 100) to include the first plurality (Fig. 1 , 104) of perforations, the second plurality (Fig. 1 , 108) of perforations, and the flow structure (Fig. 1 , 110). That is, the processor modifies the digital model to include the determined locations as the locations at which the perforations are to be formed and also includes the flow structure (Fig. 1 , 110) that is grown, or extended from the perforations. In addition, the processor removes the digital ellipsoids and adds digital representations of the perforations at the set points on and/or through the surface at which the perforations are to be formed by modifying the digital model to include the digital representations of the perforations. As a result, an additive manufacturing system employs the digital model to fabricate the fiber molding tool (Fig. 1 , 100), in which the fiber molding tool (Fig. 1 , 100) includes the perforations and flow structure (Fig. 1 , 110) at the locations determined on the digital model.

[0049] As described herein, the method (Fig. 3, 300) described herein may be implemented for the screen (Fig. 2, 216), the form tool (Fig. 2, 214), or a transfer tool, albeit with different input parameters. For example, based on dimensions of the respective fiber molding tool (Fig. 1 , 100), the placement, size, and shape of perforations differ based on whether a screen (Fig. 2, 216), form tool (Fig. 2, 214), or transfer tool is 3D printed.

[0050] Fig. 4 depicts a cross-sectional view of a branched pathway (422) flow structure, according to an example of the principles described herein. As described above, the flow structure of the fiber molding tool (100) allows fluid to flow from first side perforations (218) on a first surface (Fig. 1 , 102) of the fiber molding tool (100) through a thickness of the fiber molding tool (100) to second side perforations (220). For simplicity, in Fig. 4 and others, a single instance of a first side perforation (218) and a second side perforation is indicated with a reference number. As described above, in some examples the flow structure (Fig. 1 , 110) is defined based on both first side perforations (218) locations and based on second side perforation (220) locations. Figs. 4 and 5 depict examples of such. That is, defining a flow structure (Fig. 1 , 110) through the thickness of the fiber molding tool (100) includes defining a placement and size of first side perforations (218) and defining a placement and size of second side perforations (220). The placement and sizing of these perforations is performed as described above.

[0051] In general, the term first side perforations (218) refer to those perforations of the first plurality (Fig. 1 , 104) which are on the first surface (Fig.

1 , 102). Similarly, the term second side perforations (220) refer to those perforations of the second plurality (Fig. 1 , 108) which are on the second surface (Fig. 1, 106).

[0052] Specifically, using a technique such as sphere packing, points (indicated as black spheres) for perforations are placed over the first surface (Fig. 1 , 102) of the fiber molding tool (100) such that the points are within some margin of being equidistance from each other and with the desired density to achieve the requested open area for the fiber molding tool (100) once perforations are placed at those points. The desired spacing between perforations prevents them from colliding and thus causing potential structural weakening. A similar operation is performed for locating the second side perforations (432) on the second surface (Fig. 1 , 106).

[0053] As described above, the placement and sizing of the first side perforations (218) are defined independently from the placement and sizing of the second side perforations (220) such that the number, placement and sizing of the first side perforations (218) are different then the number, placement and size of second side perforations (220). In Figs. 4 and 5, a flow structure (Fig. 1 , 110) is then generated between the first side perforations (218) and the second side perforations (220). In either example, passages of the flow structure (Fig.

1 , 110) align with the first side perforations (218) and the second side perforations (220). That is, were the passages of the flow structure (Fig. 1 , 110) to block the perforations (218, 220), fluid flow would be impeded.

[0054] In the example depicted in Fig. 4, the flow structure (Fig. 1 , 110) includes branched pathways (422). In this example, the processor identifies, for each first side perforation (218), the nearest second side perforation (220) or previously placed pathway (422), that is in the general direction of desired fluid flow. In the case of the form tool (Fig. 2, 214), for instance, this is in the direction of the plenum. In the case of the screen (Fig. 2, 216) for instance, this is in the direction towards the form tool (Fig. 2, 214).

[0055] That is, each of the first side perforations (218), second side perforations (220), and pathways (422) have indices indicating their location. In an example, the processor calculates a shortest distance from a first side perforation (218) to each second side perforation (220) and pathway (430) and create a fluidic channel to the nearest. As this is performed for each first perforation (218), a network of branched pathways (422) is created in the space between the first surface (Fig. 1 , 102) and the second surface (Fig. 1, 106). As depicted in Fig. 4, in some examples, multiple perforations (218) of the first plurality (Fig. 1 , 104) converge to a single perforation (220) of the second plurality (Fig. 1 , 108). Similarly, multiple perforations (220) of the second plurality (Fig. 1 , 108) converge to a single perforation (218) of the first plurality.

In an example, converges in both directions are found in a single flow structure (Fig. 1 , 110).

[0056] Figs. 5A and 5B depict a lattice infill (524) flow structure, according to an example of the principles described herein. Specifically, Fig. 5A depicts an isometric view of the lattice infill (524) flow structure and Fig. 5B depicts a cross- sectional view of the lattice infill (524) flow structure. For simplicity in Fig. 5A, the first side perforations (Fig. 2, 218) and the second side perforations (Fig. 2, 220) for the fiber molding tool (100) have been omitted. Moreover, as in Fig. 4, in the remaining figures, black spheres are used to indicate locations where perforations are to be placed. [0057] In the example depicted in Figs. 5A and 5B, the flow structure (Fig. 1,

110) is a lattice infill (524). That is, a lattice structure is formed between the first surface (102) and the second surface (106). In this example, the processor identifies and defines each first side perforation (218) and each second side perforation (220) and generate a lattice therebetween.

[0058] In this example, the sizes and openings in the lattice infill (524) correspond to the first plurality (Fig. 1 , 104) of perforations and the second plurality (Fig. 1 , 108) of perforations. That is, as described above, if the ribs of the lattice infill (524) were to cover the first side and second side perforations (428, 432), flow would be interrupted which impacts the physical characteristics of the fiber molded object in an undesirable way. Accordingly, the processor identifies a particular region around the perforations (218, 220) as a region where a lattice rib is not to be placed.

[0059] As a specific example, a processor of the system receives a digital model of the object to be perforated. For each of the first surface (Fig. 1 , 102) and the second surface (Fig. 1 , 106, locations for perforations are independently determined, for example by positioning digital ellipsoids across each surface as described above. As described above the determination of the locations for perforations on the second surface is independent, and not influenced by the locations for perforations on the first surface.

[0060] The system then calculates a set of curves that represents the edge of lattice cells, which lattice cells are centered around the perforations. The curves form the connected lattice infill (524) skeleton. As the cells are centered around perforations, the curves do not cross over an area that is to be perforated, thus ensuring perforations are not blocked by the lattice infill (524). [0061] Each of the skeleton members are then increased in thickness to form the lattice ribs as depicted in Figs. 5A and 5B. This lattice structure is then subtracted from the volume of the digital model to be perforated and perforation cylinders are added to the lattice structure as material to be subtracted from the volume of the digital model.

[0062] Accordingly, ribs of the lattice infill (524) are generated in a pattern so as to not impinge upon these regions around the first side and second side perforations (218, 220). In an example, other characteristics such as the length and diameter of lattice ribs and volume of lattice openings are defined based on perforation dimensions, fiber molding tool (100) characteristics, and/or user input.

[0063] The lattice infill (524) structure between the surfaces allows fluid to flow from first side perforations (218) to second side perforations (220). Such a lattice infill (524) provides for a direct path from any first side perforation (218) to a second side perforation (220). Such direct paths facilitate the cleaning of additive manufacturing powder when printed or slurry (Fig. 3, 222) during fiber molding. The lattice infill (524) also provides rigidity to the fiber molding tool (Fig. 1 , 100) to prevent flexure during handling and/or fiber molding.

[0064] Fig. 6 depicts a cross-sectional view of a flow structure (Fig. 1 , 110), according to an example of the principles described herein. In the example depicted in Fig. 6, the flow structure (Fig. 1 , 110) is defined by an intersection of a lattice volume (626) with the digital model of the fiber molding tool (100). For example, the processor overlays the digital model over a lattice volume (626) of a generic size and shape, but that is larger than the digital model. The processor then intersects the two. That is, each pixel that falls both within the boundaries of the lattice volume (626) and the digital model of the fiber molding tool (100) are retained while pixels that are outside the boundaries of either are discarded. As such, the additive manufacturing file in this example includes an overlap of the lattice volume (626) over the digital model of the fiber molding tool (Fig. 1 , 100). In this example, the lattice passages at the intersection with the digital model and the lattice volume 9636) define both the first plurality (Fig.

1 , 104) of perforations and the second plurality (Fig. 1, 108) of perforations. [0065] Figs. 7A and 7B depict a lattice flow structure (728), according to an example of the principles described herein. As described above, in some examples the flow structure is defined from both ends, i.e. , a first surface (102) and a second surface (106). In this example, the lattice flow structure (728) extends from one surface, in particular the first surface (102) with the lattice spaces at the second surface (106) defining the second plurality (Fig. 1 , 108) of perforations. In this example, the lattice structure or pathways extend a target distance, for example to a frame or other component of the digital model.

[0066] As before, the passages in the lattice structure (728) are sized and positioned to align with the first side perforations (218). That is, in an example, the first side perforations (218) have a surrounding volume which is designated as being free from lattice ribs. Accordingly, the processor generates the ribs for the lattice structure (728), which may be a symmetrical three-dimensional lattice structure, ensuring that no ribs fall within the volume surrounding each first side perforations (218).

[0067] In this example, using a technique such as sphere packing, points for perforation locations are placed over the first surface (102) of the fiber molding tool (100) such that the points are within some margin of being equidistance from each other and with the desired density to achieve the requested open area for the fiber molding tool (100) once perforations are placed at those points. The desired spacing between perforations prevents them from colliding and thus causing potential structural weakening.

[0068] In this example, a lattice structure (728) is generated using the location, sizing, and spacing of the first side perforations (218) as input parameters for the lattice structure (728) ribs and passages. In an example, the thickness to which the lattice structure (728) is extended is based on any number of criteria. For example, the digital model of the fiber molding tool (100) may include a frame located a certain distance away from the first surface (102). In this example, the lattice structure (728) is extended to the frame or to any other target distance.

[0069] In an example, the lattice structure (728) ribs are thicker and passageways are wider towards the second surface (106) of the fiber molding tool (100). As such, the quantity of ribs decreases towards the second surface (106) of the fiber molding tool (100). That is, as the distance from the first surface (102) increases, the lattice structure (728) ribs become less in number, but larger. At the point furthest from the first surface (102), for example as defined by the target distance and/or frame, the lattice structure (728) ribs provide a rigid support for the fiber molding tool (100). In an example, a last layer of the rigid support (i.e., the second surface) and the first surface perforations are defined and the lattice structure (728) is grown between the two as described above.

[0070] While particular reference is made to a particular lattice structure (728), other types of lattice structures (728) may be implemented. For example, the lattice structure (728) may be a gyroidal lattice which includes a triply periodic minimal surface lattice for infill. This structure provides a sure path between first side perforations (218) and second side perforations (220).

[0071] Fig. 8 depicts a cross-sectional view of a flow structure (Fig. 1 , 110), according to an example of the principles described herein. In this example, the processor defines for each first side perforation (218), a shortest path to the second surface (Fig. 1, 106) of the fiber molding tool (100).

[0072] In this example, using a technique such as sphere packing, points for perforation locations are placed over the first surface (Fig. 1 , 102) of the fiber molding tool (100) such that the points are within some margin of being equidistance from each other and with the desired density to achieve the requested open area for the fiber molding tool (100) once holes are placed at those points. The desired spacing between holes will prevent them from colliding and thus causing potential structural weakening.

[0073] In an example, the fiber molding tool (100) includes a pipe (830) from the first side perforations (218) to the nearest point on the second surface (Fig.

1 , 106) of the fiber molding tool (100). That is, each of the first side perforations (218) and the second surface (Fig. 1 , 106) have indices indicating their location. In this example, the processor calculates a shortest distance from a first side perforation (218) to a location on the second surface (Fig. 1 , 106). In this example, the intersection of a pipe (830) and the second surface (Fig. 1 , 106) defines a perforation of the second plurality (Fig. 1 , 108). In an example, the pipes (830) are straight to provide enhanced cleaning of the additive manufacturing build material and to prevent clogging of the fiber molding tool (100) during fiber molding as pulp is less likely to get stuck in straight pipes (830). [0074] Fig. 9 is a flowchart of a method (900) for generating a fiber molding tool (Fig. 1 , 100) flow structure (Fig. 1 , 110), according to an example of the principles described herein. According to the method (900), a processor accesses (block 901) a digital model of a fiber molding tool (Fig. 1 , 100) to be fabricated and determines (block 902) a distribution of a first plurality (Fig. 1 ,

104) of perforations on a first surface (Fig. 1 , 102) of the fiber molding tool (Fig. 1 , 100) and determines (block 903) a distribution of a second plurality (Fig. 1 ,

108) of perforations on a second surface (Fig. 1 , 106) of the fiber molding tool (Fig. 1 , 100). The processor also defines (block 904) the flow structure (Fig. 1 , 110) through the fiber molding tool (Fig. 1 , 100) and modifies (block 905) the digital model. In some examples, these operations are performed as described above in connection with Fig. 2.

[0075] In an example, the processor generates (block 906) an additive manufacturing file for the fiber molding tool (Fig. 1 , 100) and flow structure (Fig. 1 , 110). In this example, the fiber molding tool (Fig. 1 , 100) is formed by fusing build material particles together, which are fused together during an additive manufacturing process by an additive manufacturing system. In these examples, the build material particles may be any suitable type of material that is employed in 3D fabrication processes, such as, a metal, a plastic, a nylon, a ceramic, an alloy, and/or the like. In some examples, the screen is formed to have a relatively thin height and is relatively pliable as compared to the form tool. In other examples, the structures are formed through other fabrication techniques such as selective laser ablation, selective laser melting, stereolithography, fused deposition modeling, and/or the like. As such, the processor converts a modified digital model into a format usable by an additive manufacturing system to create the fiber molding tool (Fig. 1 , 100). In an example, this includes converting the format of the digital model file to an additive manufacturing file format.

[0076] In some examples, in addition to generating (block 906) the additive manufacturing file, the processor additively manufactures (block 907) the fiber molding tool (Fig. 1 , 100) to be fabricated with the first side perforations (Fig. 2, 218) and the flow structure (Fig. 1 , 110). That is, in some examples, the system forms part of the additive manufacturing system itself such that a single device is used to generate the additive manufacturing file and generate the fiber molding tool (Fig. 1 , 100) itself. Note that as described above, the additive manufacturing may take a variety of forms fusing agent-based manufacturing, a binding agent-based manufacturing, selective laser sintering, selective laser melting, fused metal deposition, and stereolithography. As such, additively manufacturing (block 905) the fiber molding tool (Fig. 1 , 100) includes forming the fiber molding tool (Fig. 1 , 100) via any of the aforementioned, or other, additive manufacturing processes.

[0077] Fig. 10 depicts a non-transitory machine-readable storage medium (1032) for generating a fiber molding tool (Fig. 1 , 100) flow structure, according to an example of the principles described herein. To achieve its desired functionality, a system includes various hardware components. Specifically, the system includes a processor and a machine-readable storage medium (1032). The processor may be a semiconductor-based microprocessor, a central processing unit (CPU), an application specific integrated circuit (ASIC), a field- programmable gate array (FPGA), and/or other suitable hardware device.

[0078] The machine-readable storage medium (1032) is communicatively coupled to the processor. The machine-readable storage medium (1032) includes a number of instructions (1034, 1036, 1038, 1040) for performing a designated function. In some examples, the instructions may be machine code and/or script code.

[0079] The machine-readable storage medium (1032) causes the processor to execute the designated function of the instructions (1034, 1036, 1038, 1040). The machine-readable storage medium (1032) can store data, programs, instructions, or any other machine-readable data that can be utilized to operate the system. The machine-readable storage medium (1032) can store machine readable instructions that the processor of the system can process, or execute. The machine-readable storage medium (1032) can be an electronic, magnetic, optical, or other physical storage device that contains or stores executable instructions. Machine-readable storage medium (1032) may be, for example, Random-Access Memory (RAM), an Electrically Erasable Programmable Read- Only Memory (EEPROM), a storage device, an optical disc, etc. The machine- readable storage medium (1032) may be a non-transitory machine-readable storage medium (1032 where the term “non-transitory” does not encompass transitory propagating signals.).

[0080] Referring to Fig. 10, digital model instructions (1034), when executed by the processor, cause the processor to, access a digital model of a fiber molding tool (Fig. 1 , 100) to be fabricated. Perforation instructions (1036), when executed by the processor, cause the processor to determine a distribution of a first plurality (Fig. 1 , 104) of perforations on a first surface (Fig. 1 , 102) of the fiber molding tool (Fig. 1 , 100) and determine a distribution of a second plurality (Fig. 1 , 108) of perforations on a second surface (Fig. 1 , 106) of the fiber molding tool (Fig. 1 , 100), wherein a distribution of the second plurality (Fig. 1 ,

108) of perforations are independent of a distribution of the first plurality (Fig. 1 ,

104) of perforations on the first surface (Fig. 1 , 102).

[0081] Flow structure instructions (1038), when executed by the processor, cause the processor to define a flow structure (Fig. 1 , 110) extending from the first plurality (Fig. 1 , 104) of perforations on the first surface (Fig. 1 , 102) through a thickness of the fiber molding tool (Fig. 1 , 100) such that a fluid is to flow from the first plurality (Fig. 1 , 104) of perforations through the flow structure (Fig. 1 , 110) to the second plurality (Fig. 1 , 108) of perforations. Modify instructions (1040), when executed by the processor, cause the processor to modify the digital model of the fiber molding tool (Fig. 1 , 100) to include the first plurality (Fig. 1 , 104) of perforations, the second plurality (Fig. 1 , 108) of perforations, and the flow structure (Fig. 1 , 110). Additive manufacturing file instructions (1042), when executed by the processor, also cause the processor to, generate an additive manufacturing file for the fiber molding tool (Fig. 1 , 100) with the flow structure (Fig. 1 , 110) merged with the digital model of the fiber molding tool (Fig. 1 , 100).

[0082] In summary, such a tool, method, and machine-readable storage medium may, for example 1) provide for placement of perforations in fiber mold components to ensure effective fluid flow through the mold and uniform thickness of the molded product; 2) enable placement of perforations on both surfaces of the fiber molding tool independently; and 3) facilitate the additive manufacturing of the fiber mold components. However, it is contemplated that the devices disclosed herein may address other matters and deficiencies in a number of technical areas, for example.

Claims

1 . A fiber molding tool, comprising: a first surface comprising a first plurality of perforations; a second surface comprising a second plurality of perforations, wherein a distribution of the second plurality of perforations on the second surface is independent of a distribution of the first plurality of perforations on the first surface; and a flow structure through a thickness of the fiber molding tool such that a fluid is to flow from the first plurality of perforations, through the flow structure to the second plurality of perforations.

2. The molded fiber tool of claim 1 , wherein the fiber molding tool is selected from the group consisting of: a form tool for a molded fiber die; a screen for the molded fiber die; and a transfer tool for the molded fiber die.

3. The fiber molding tool of claim 1 , wherein a number, placement, shape, and size of the first plurality of perforations is different than a number, placement, shape, and size of the second plurality of perforations.

4. The fiber molding tool of claim 3, wherein the flow structure comprises branched pathways.

5. The fiber molding tool of claim 4, wherein: multiple perforations of the first plurality converge to a single perforation of the second plurality; multiple perforations of the second plurality converge to a single perforation of the first plurality; or combinations thereof.

6. The fiber molding tool of claim 1 , wherein: the flow structure comprises a lattice infill; and sizes and openings in the lattice infill correspond to the first plurality of perforations and the second plurality of perforations.

7. A method, comprising: accessing, with a processor, a digital model of a fiber molding tool to be fabricated; determining, with the processor, a distribution of a first plurality of perforations on a first surface of the fiber molding tool; determining, with the processor, a distribution of a second plurality of perforations on a second surface of the fiber molding tool, wherein the distribution of the second plurality of perforations on the second surface is independent of the distribution of the first plurality of perforations on the first surface; defining, with the processor, a flow structure extending between the first plurality of perforations and the second plurality of perforations through a thickness of the fiber molding tool such that a fluid is to flow from the first plurality of perforations through the flow structure to the second plurality of perforations; and modifying, with the processor, the digital model of the fiber molding tool to include the first plurality of perforations, the second plurality of perforations and the flow structure.

8. The method of claim 7, further comprising: determining, with the processor, the placement and size of the second plurality of perforations comprises extending a lattice structure from the first plurality of perforations towards the second surface, wherein passages in the lattice structure are sized and positioned to align with the first plurality of perforations; and modifying, with the processor, the digital model to include the lattice structure.

9. The method of claim 7, wherein defining a flow structure comprises intersecting a lattice volume with the digital model of the fiber molding tool.

10. The method of claim 7, wherein defining, with the processor, a flow structure extending between the first plurality of perforations and the second plurality of perforations comprises defining, for each perforation of the first plurality of perforations, a shortest path to the second surface of the fiber molding tool.

11. The method of claim 7, wherein defining, with the processor, a flow structure extending between the first plurality of perforations and the second plurality of perforations comprises defining branched pathways between the first plurality of perforations and the second plurality of perforations.

12. The method of claim 7, further comprising: generating, with the processor, an additive manufacturing file for the fiber molding tool with the flow structure merged with the digital model of the fiber molding tool; and additively manufacturing the fiber molding tool to be fabricated with the exterior surface protrusions and flow structure.

13. The method of claim 7, wherein the distribution of the first plurality of protrusions and the second plurality of protrusions are determined based on elements selected from the group consisting of: a thickness of the fiber molding tool; a material of the fiber molding tool; a radius of curvature of the fiber molding tool; a desired thickness for the fiber molded product; and a material of the fiber molded product to be formed.

14. A non-transitory machine-readable storage medium encoded with instructions executable by a processor, the machine-readable storage medium comprising instructions to, when executed by the processor, cause the processor to: access a digital model of a fiber molding tool to be fabricated; determine a distribution of a first plurality of perforations on a first surface of the fiber molding tool; determine a distribution of a second plurality of perforations on a second surface of the fiber molding tool, wherein a distribution of the second plurality of perforations on the second surface are independent of a distribution of the first plurality of perforations on the first surface; define a flow structure extending from the first plurality of perforations on the first surface through a thickness of the fiber molding tool such that a fluid is to flow from the first plurality of perforations through the flow structure to the second plurality of perforations; modify the digital model of the fiber molding tool to include the first plurality of perforations, the second plurality of perforations, and the flow structure; and generate an additive manufacturing file for the fiber molding tool with the flow structure merged with the digital model of the fiber molding tool.

15. The non-transitory machine-readable storage medium of claim 13, wherein: lattice ribs are thicker and passageways are wider towards the second surface of the fiber molding tool; the lattice flow structure is a gyroidal lattice; or combinations thereof.