Method for forming molded articles from a moldable material in a mold, mold, and molded article

Abstract

A method for forming molded articles from a moldable material in a mold, a mold, and a molded article is disclosed. The mold has two mold halves that, in a closed state, define a mold cavity between the mold surfaces of the mold halves and the mold cavity has an undercut. The mold halves have openings on their mold surfaces via which a relative underpressure and a relative overpressure are configured to be generated. Moldable material in the mold cavity is pressed into a molded article when the mold is closed and, for deforming, an overpressure is generated via the openings of a second mold surface when the mold is closed, such that the molded article is pushed away from the second mold surface and the mold is then opened by relative displacement of the mold halves away from one another.

Description

PRIORITY CLAIM

[0001] The present application claims priority under 35 U.S.C. § 119 to German Patent Application No. DE 10 2025 102 506.1, filed January 23, 2025, the disclosure of which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The invention describes a method for forming molded articles from a moldable material in a mold, a mold, and a molded article.BACKGROUND

[0003] Recently, fibrous materials are increasingly used, for example, to produce packaging for food (e.g., trays, capsules, boxes, etc.) and consumer goods (e.g., electronic devices, etc.) as well as beverage containers. The fibrous materials usually have natural fibers, which are obtained, for example, from renewable raw materials or waste paper. The natural fibers can be mixed in a so-called pulp with water and optionally further additives, such as starch. Additives can also have an effect on color, barrier properties and mechanical properties. This pulp can have a proportion of natural fibers of, for example, 0.2 to 10 wt.%. The proportion of natural fibers varies depending on the method used for the production of packaging etc. and the product properties of the product to be produced. In addition, fibrous materials are increasingly being used that can be processed in a dry state. Examples include airlaid, fluff pulp, crepe, paper, cardboard, etc. Furthermore, films made of polymers are shaped in thermoforming machines into packaging for various applications.

[0004] When producing molded articles from a fibrous material, for example preforms made of a fibrous material with a relatively high moisture content or relatively dry preforms or fiber webs / cuttings are pressed together under high pressure and high temperature. This creates a connection between the individual fibers.

[0005] To shape polymers, film webs or web cuttings are fed to a mold, where the webs or web cuttings can be heat-treated beforehand.

[0006] Forming is usually carried out using a mold that has at least two mold halves that are movable relative to one another. For forming, for example, the fibrous material is placed between the mold halves and the fibrous material is then pressed in a mold cavity. For this purpose, the mold is closed, where the mold halves are moved toward one another. The formation of molded articles with so-called undercuts is made difficult or impossible due to the forming direction, i.e., the opening and closing of the mold. If the formation of undercuts is necessary, additional movable components must necessarily be provided in the mold halves, which can perform a movement that deviates from the forming direction. Such components include, for example, sliders that are movable orthogonally to the forming direction.

[0007] The formation of molds with such sliders has several disadvantages. For example, such molds are complex and subject to high requirements with regard to manufacturing tolerances and movability. Therefore, production, acquisition, and maintenance are all very time-consuming and expensive. In particular, molds for fibrous materials, in particular moist fiber materials, tend to become relatively heavily soiled due to the fibrous material. For components that are movable within a cavity (mold cavity), the risk of contamination and impairment increases significantly because, for example, fibers can get into the spaces between movable components, which can severely impair functionality.

[0008] Furthermore, movable components cause overlaps or folds in molded articles, in particular in the undercut. This means that, for example, lids do not provide a completely homogeneous contact surface because the folds or overlaps created by the displaceable components form elevations on the molded article. To reduce resulting leaks when placing lids on, for example, a cup edge, undercuts are oversized, i.e., made larger. This is an attempt to reduce leaks by larger contact regions.

[0009] Moreover, the integration of movable components into molds results in higher costs and more complex tool designs.

[0010] A mold with components movable orthogonally to the forming direction is known, for example, from DE 10 2020 109 686 A1.SUMMARY OF EMBODIMENTSOBJECT

[0011] The object is therefore to present a solution for producing products made from fibrous material, where products with complex geometries, in particular with at least one undercut, can be produced, and the disadvantages of the prior art are eliminated. In addition, a solution should be provided in which moving mold surfaces for a tool are not required.SOLUTION

[0012] The aforementioned object is achieved by a method for forming molded articles from a moldable material in a mold, where the mold has two mold halves that, in a closed state, define a mold cavity between the mold surfaces of the mold halves and the mold cavity has an undercut, where the mold halves each have openings on their mold surfaces via which a relative underpressure and a relative overpressure can be generated, where moldable material in the mold cavity is pressed into a molded article when the mold is closed and, for deforming, an overpressure is generated via the openings of a second mold surface when the mold is closed, so that the molded article is pushed away from the second mold surface and the mold is then opened by relative displacement of the mold halves away from one another.

[0013] It has been shown that by providing overpressure after molding, the molded article can be pressed against the first mold surface such that a linear stroke, i.e., relative movement of the two mold halves away from one another, is possible without additional movement of further components in order to deform a molded article with an undercut, where the undercut is not damaged. By eliminating movable components within the mold halves, the molded article subsequently has no folds or overlaps that would impair the tightness of undercuts at corresponding surfaces. Accordingly, smaller undercuts can be formed to achieve the required tightness. Smaller undercuts make deforming easier. When pushing the molded article away from the second mold surface, the process of passing over a narrow point in the mold in the region of an undercut is also significantly supported, where the molded article is "pressed" over the narrow point in this region.

[0014] In molded articles from the prior art (e.g., lids), they always exhibit markings (folds etc.) that result from additional strokes alongside the main forming movement.

[0015] In further embodiments, the molded article can be suctioned through the openings of a first mold surface after molding, so that in addition to being pushed away from the second mold half, the molded article is suctioned to the mold surface of the first mold half, thereby further improving deforming and simultaneously holding the molded article in place.

[0016] In further embodiments, the overpressure and / or the underpressure can be maintained when the mold is open. Maintaining the underpressure makes it possible to hold molded articles and transfer them to further stations via the mold half.

[0017] In further embodiments, the undercut can have a depth (t) of 0.05 to 1 mm, so that the undercut in molded articles can be approximately between 0.1 and 2 mm in diameter. This means that the undercut is significantly less pronounced compared to undercuts produced by means of molds with movable components, but this design without defects (folds, overlaps, etc.) allows an at least equivalent sealing effect when latching onto corresponding contact surfaces.

[0018] In further embodiments, a relative overpressure of 1.2 to 6 bar can be generated.

[0019] In further embodiments, the mold cavity can have an offset of less than 2 mm, so that molded articles made of fibrous material can be formed.

[0020] In further embodiments, the overpressure and / or the underpressure can be changed. For example, the overpressure at the beginning can be significantly higher in order to provide high pressure against the molded article. In other embodiments, the pressure increases so that, even when the mold is already partially open, there is still sufficient pressure to push the molded article away from the second mold surface.

[0021] In further embodiments, the underpressure can be provided by creating a vacuum.

[0022] In further embodiments, compressed air can be released through the openings in the second mold surface.

[0023] In further embodiments, more openings can be provided at the mold surfaces in the region of the undercut than on remaining regions of the mold surfaces to facilitate deforming, since the pressure in the region of the undercut is thus high enough to support the opening movement of the mold substantially orthogonal to the orientation of the undercut.

[0024] In further embodiments, a greater overpressure and / or underpressure can be generated in the region of the undercut compared to the remaining regions of the mold surfaces in order to increase the pressure or suction effect for an easier opening movement of the mold and thus simplify it further.

[0025] In further embodiments, a first mold half with the first mold surface can form a negative side and a second mold half with the second mold surface can form a positive side of the mold. It has also been shown that molded articles with an undercut, which is formed, for example, only on an inner side of a molded article, can thus be easily deformed.

[0026] In further embodiments, the material of the formed molded article can be elastically compressed at least in an undercut region of the molded article by the overpressure acting on the molded article and the underpressure acting by suction when opening the mold. In particular for molded articles made of fibrous material with an undercut, deforming can be significantly simplified by simply moving the mold halves linearly. Molded articles made of fibrous material normally have a greater wall thickness than molded articles made of polymers, so that the fibrous material can be elastically deformed for short periods.

[0027] The aforementioned object is also achieved by a mold for forming molded articles, including a first mold half with a first mold surface and a second mold half with a second mold surface, where the mold, in its closed state, forms a mold cavity between the first mold surface and the second mold surface for forming a molded article, and where the first mold surface and the second mold surface have openings via which an overpressure and an underpressure can be generated in the mold cavity and at the molded article, where the mold is configured to perform one of the methods described above.

[0028] The aforementioned object is further achieved by a molded article, in particular made of a fibrous material and produced according to any of the methods described above, where the molded article has an undercut with a depth (t) of 0.05 to 1 mm. In combination with the special method, where the molded article is pushed away from the mold surface of the second mold half for deforming, molded articles with very shallow undercut depths can be produced, where, due to the design of the undercut without overlaps and folds, a sufficient sealing effect can be achieved when the undercut comes into contact with corresponding surfaces of a cup or the like. This allows the molded article to have a constant wall thickness in the undercut and in adjacent regions in the circumferential direction.

[0029] In further embodiments, the undercut can be formed by an accumulation of fibrous material and have a greater wall thickness compared to adjacent regions in the deforming direction. In such embodiments, the undercut can be formed, for example, on an inner side by differences in wall thickness, where no undercut is formed on the outer side. This also simplifies deforming, because the undercut acts on only one side of the tool.

[0030] Further features, embodiments and advantages result from the following illustration of exemplary embodiments with reference to the figures.BRIEF DESCRIPTION OF THE FIGURES

[0031] In the figures.

[0032] FIGS. 1A and 1B show schematic representations of lids made of fibrous material with an undercut according to the prior art;

[0033] FIG. 2 shows a schematic sectional view through a molded article made of fibrous material according to the technical teaching described herein;

[0034] FIG. 3 shows an enlarged representation of the molded article from FIG. 2;

[0035] FIGS. 4A and 4B show different representations of lids made of fibrous material with an undercut according to the technical teaching described herein;

[0036] FIGS. 5A and 5B show a mold for forming molded articles according to the technical teaching described herein; and

[0037] FIG. 6 shows a schematic representation of a method for forming molded articles from a moldable material in a mold.DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0038] Exemplary embodiments of the technical teaching described herein are shown below with reference to the figures. Identical reference signs are used in the figure description for identical components, parts and processes. Components, parts and processes that are not substantial to the technical teachings disclosed herein or that are obvious to a person skilled in the art are not explicitly reproduced. Features specified in the singular also encompass the plural unless explicitly stated otherwise. This applies in particular to statements such as "a" or "one."

[0039] FIGS. 1A and 1B show schematic representations of lids 10 made of a fibrous material with an undercut 14 according to the prior art. The lid 10 is manufactured in a so-called WET process, where fibers are suctioned from a pulp and a preform formed from the suctioned-in fibers is pressed in a mold under pressure and temperature input.

[0040] The undercut 14 is created in a mold by movable elements in the mold, which in an edge 12 act on the lid 10 and thus form the undercut 14. The formation of undercuts 14 itself is known from the prior art. For example, undercuts 14 are introduced into lids 10 so that lids 10 can engage behind a corresponding portion, e.g., a bead-like edge of a cup. The lid 10 is secured from falling off by the snap-fit connection between the edge of the cup and the undercut 14 and provides a seal between the cup and the lid 10 so that, for example, no hot coffee or other liquid can escape during drinking.

[0041] As shown in FIGS. 1A and 1B, the lids 10 have folds 16 and overlaps on their outer side in the region of the undercut 14. The folds 16 and overlaps are created by the movable components of the mold, as described at the beginning. Folds 16 and overlaps can be found not only on the outer side of the lid 10, but also on the inner side of the lid 10 and contribute significantly to the fact that a tightly sealing contact between the lid 10 and the edge of a cup cannot occur, because due to the overlaps and folds 16 no homogeneous circumferential contact surface is formed in the undercut 14. To increase tightness, undercuts 14 are often formed with a greater depth (see FIG. 3), so that an overall larger contact region is created. However, this also leads to an increase in folds 16 and overlaps, since moist fiber material of a preform is pushed together more strongly by the movable components tangentially to the circumferential direction of the lid 10.

[0042] FIG. 2 shows a schematic sectional view through a molded article 20 made of fibrous material according to the technical teaching described herein that is designed as a lid, which has an undercut 28 in an edge 22 that shows no overlaps or folds. The undercut 28 in the embodiments described below is achieved by reducing the depth t (see FIG. 3) of the effective undercut 28 in conjunction with targeted control of introduced compressed air or relative overpressure. In the embodiments shown, the undercut 28 is formed on an inner side 26 in the region of the edge 22. The opposite region on an outer side 24 has no undercut 28, so that the formation of effective undercuts 28 and deforming is further improved compared to the prior art.

[0043] FIG. 3 shows an enlarged representation of the molded article 20 from FIG. 2 in the region of the undercut 28. Since the undercut 28 is formed without elevations, folds, overlaps or the like on the peripheral side, it can have a considerably smaller depth t compared to known embodiments. For example, the depth t can be 0.05 - 1 mm.

[0044] FIGS. 4A and 4B show various representations of lids or molded articles 20 made of fibrous material with an undercut 28 according to the technical teaching described herein, where there is no indentation on the outer side 24. The formation of the effective undercut 28 on the inner side 26 also improves the stacking and unstacking capability of such molded articles 20, because undercuts 28 on the inner side 26 cannot engage behind corresponding surfaces on the outer side 24 and only come to rest against substantially smooth or flat edge surfaces.

[0045] FIGS. 5A and SB show a mold 50 for forming molded articles 20 made of a fibrous material according to the technical teaching described herein. The mold 50 is arranged in a forming station of a system for producing molded articles. The system can include further components, such as a suction station, a pre-pressing station, transport devices, and control and regulation devices.

[0046] The mold 50 has a first mold half 52 and a second mold half 56. The first mold half 52 and the second mold half 56 are made of a thermally conductive material (e.g., aluminum) and have heating devices. The mold halves 52, 56 each have a mold surface 54, 58. Channels 53, 57 run through the mold halves 52, 56, via which compressed air can be supplied and suction can take place. The representation of channels 53, 57 in FIG. 5A is schematic. The channels 53, 57 open into openings in the mold surfaces 54, 58. When the mold 50 is in the closed state, a mold cavity 51 is formed between the mold surfaces 54, 58. In the mold cavity 51, fibrous material is pressed into a molded article 20 under pressure and temperature influence, so that a relatively moist preform with a moisture content of 40-90 wt.% water is formed into a molded article 20. The molded article 20 has a moisture content of approximately 2-15 wt.% water after pressing. During pressing, the fibers of the preform become in particular interconnected. Water vapor escaping from the fibrous material during pressing is discharged via channels 53 and / or channels 57.

[0047] In further embodiments, relatively dry fiber material can be pressed in a mold 50 in a so-called DRY process, where usually no water vapor is produced, since the moisture content is less than 30 wt.% water.

[0048] FIGS. 5A and 5B show only a section, where the mold cavity 51 for forming lids or molded articles 20 is partially shown. Furthermore, in further embodiments, molds 50 can have several cavities or mold cavities 51, so that several molded articles 20 can be manufactured simultaneously in one molding step.

[0049] In further embodiments, forming stations can have two opposing tool tables, and first mold halves 52 and second mold halves 56 can be arranged at the tool tables.

[0050] The second mold surface 58 is formed in a region with an undercut 55, so that, during pressing, a corresponding undercut 28 is created at the edge 22 of a molded article 20. The opposite region of the first mold surface 54 does not have such an undercut, so that closing the mold 50 and deforming (i.e., opening the mold 50) has no negative effect on the outer side 24 of the molded article 20. Advantageously, the undercut 28 of the molded article 20 is formed only on the inner side 26.

[0051] The mold halves 52, 56 shown in FIG. 5A can be displaced relative to one another in order to introduce fibrous material between the mold surfaces 54, 58, to press it and to remove it from the mold cavity 51.

[0052] FIG. 5B schematically shows a state of the mold 50 after a molding operation during deforming. During such operation, the manufactured molded article 20 is suctioned in via the channels 53 (not shown in FIG. 5B for reasons of simplicity) of the first mold half 52 in order to hold the molded article 20 on the first mold half 52. In order to allow deforming without damaging the formed undercut 28, an overpressure is generated via the channels 57 after forming, while the mold 50 is still closed (see FIG. 5A), so that the molded article 20 is pushed away from the second mold surface 58 and pressed against the first mold surface 54. For this purpose, compressed air at, for example, 1.2 to 6 bar can be introduced into the channels 57.

[0053] The suction and application of compressed air is schematically indicated by the arrows in FIG. 5B. The channels 53, 57 are connected with appropriate devices for the intake of water vapor that arises during pressing under pressure and temperature influence, and for generating an overpressure by compressed air (or another gas or gas mixture) at the mold surfaces 54, 58. Suction devices can include fans and vacuum tanks. Devices for generating overpressure can include, for example, compressors and pressure chambers. Channels 53 and / or channels 57 leading to mold surfaces 54, 58 can be connected to a distribution manifold that can be connected to further channels 53, 57 of further mold surfaces 54, 58 in order to jointly control the provision of overpressure and underpressure for a plurality of molds 50 of a forming station. In further devices, it is possible to switch between providing underpressure and overpressure. For example, during pressing, an underpressure can be applied or suction can be carried out via the openings and channels 53, 57 of both mold surfaces 54, 58 in order to remove water vapor during pressing. After pressing, before the mold 50 is opened, switching can be carried out such that overpressure is provided or compressed air is released via the openings and channels 57 to push the formed molded article 20 away from the second mold surface 58. Valves or other control devices can be provided for this purpose, which regulate the quantity and speed of the discharged water vapor and / or the application of compressed air.

[0054] The enlarged representation of FIG. 5B schematically shows a hatched region 21 that can be traversed without damage during the linear stroke. Region 21 can be temporarily elastically compressed without damaging the fibrous material. The provision of overpressure at the second mold surface 58, when the mold 50 is opened, primarily causes the molded article 20 to be "overpressed" in region 21, so that traversing said critical region 21 is easier without damaging or weakening the molded article 20.

[0055] The schematically shown design of the mold 50 and the dimensioning of the molded article 20 or depth t of the undercut 28 allow a linear displacement of the mold halves 52, 56 toward one another without additional strokes orthogonal to the closing and opening direction.

[0056] FIG. 6 shows a schematic representation of a method 60 for forming molded articles 20 from a moldable material in a mold 50. Fibrous material or plastics can be used as moldable material. The design of molds 50 and the processing and provision for the molding process may differ depending on the materials used. For example, pre- heating may be necessary for forming polymer films. In case of dry fiber materials (e.g., airlaid, fluff pulp, etc.), local moistening can be carried out. When producing molded articles 20 from a pulp, fibrous material can first be suctioned in from the pulp to the suction body of a suction tool and the suctioned-in fibers can be pressed into preforms in a pre-pressing station, where water is mechanically pressed out of the fibrous material.

[0057] Subsequently, preforms are introduced into cavities or in the mold cavity 51 of a mold 50. This involves the introduction 61 of the moldable material, e.g., a preform, where the preform is placed on a first mold surface 54 of a first mold half 52. Subsequently, the mold 50 is closed 62, for which purpose the mold halves 52 and 56 are moved relative to one another. The fibrous material of the preform is then pressed 63, forming an undercut 28, as described above. During pressing 63, heat is introduced into the fibrous material via the thermally conductive mold surfaces 54, 58. Water vapor escaping from the fibrous material during pressing 63 can be discharged via the openings in the mold surfaces 54, 58 and the channels 53, 57. After the preform has been formed into a molded article 20, an overpressure provision 64 is provided at the second mold surface 58 by supplying compressed air to the channels 57 and by suctioning in the molded article 20 through the openings in the first mold surface 54 and the channels 53, while the mold 50 is still closed. This results in a slight compression of the fibrous material of the molded article 20, in particular in the region of the undercut 28. For this purpose, the overpressure in the region of the undercut 28 or the adjacent regions of the molded article 20 can be greater than in other regions of the molded article 20. To achieve this, the pressure can be locally variable and / or multiple channels 57 can be provided in this region. In yet further embodiments, the cross sections and diameters of the channels 57 can vary in the regions in order to provide different pressures.

[0058] The provision 64 of underpressure and overpressure is maintained when an opening 65 of the mold 50 takes place, where the mold halves 52, 56 are moved away from one another relative to one another. Since the undercut 28 has a very shallow depth t and the fibrous material of the molded article 20 is pushed away from the second mold surface 56, and in particular traversing the narrow point in the mold 50 in the region of the undercut 55 is significantly supported by the overpressure, deforming or opening 65 can only be carried out by a linear movement of the two mold halves 52, 56 of the mold 50. By suctioning in the molded article 20 against the first mold surface 54 and pushing it away from the second mold surface 58, a slight elastic compression of the fibrous material occurs locally at the molded article 20. An additional elastic compression can occur when passing over mold surfaces 58, as shown schematically in FIGS. 5A and 5B .

[0059] Once the mold 50 has been opened, the application of overpressure to the second mold surface 58 can be stopped. The molded article 20 can continue to be held via the first mold surface 54 by providing an underpressure in order to subsequently transfer 66 the manufactured molded article 20 to a transport or transfer device for further processing or machining. For the transfer, the provision of the underpressure or suction can be stopped in order to detach the molded article 20 from the first mold surface 54.

[0060] Advantageously, the undercut 28 is formed only on the inner side 26, so that the molded article 20 can be released without additional tool movements, because no undercut is formed on the outer side 24.

[0061] The presented solution allows the formation of undercuts 28 in molded articles 20 with a simple tool design and by means of a linear forming process, without causing damage or deterioration of the surface quality of molded articles 20 (in particular in the region of undercuts 28, cf. folds 16 in known embodiments).LIST OF REFERENCE SIGNS

[0062] 10 Lid

[0063] 12 Edge

[0064] 14 Undercut

[0065] 16 Fold

[0066] 20 Molded article

[0067] 21 Region

[0068] 22 Edge

[0069] 24 Outer side

[0070] 26 Inner side

[0071] 28 Undercut

[0072] 50 Mold

[0073] 51 Mold cavity

[0074] 52 First mold half

[0075] 53 Channel

[0076] 54 First mold surface

[0077] 55 Undercut

[0078] 56 Second mold half

[0079] 57 Channel

[0080] 58 Second mold surface

[0081] 60 Method

[0082] 61 - 66 Method steps

[0083] t Depth

Claims

1. A method for forming molded articles from a moldable material in a mold, wherein the mold has two mold halves that, in a closed state, define a mold cavity between mold surfaces of the two mold halves and the mold cavity has an undercut, wherein the two mold halves have openings on their mold surfaces via which a relative underpressure and a relative overpressure are configured to be generated, wherein the moldable material in the mold cavity is pressed into a molded article when the mold is closed and, for deforming, an overpressure is generated via openings of a second mold surface when the mold is closed, such that the molded article is pushed away from the second mold surface and the mold is then opened by relative displacement of the two mold halves away from one another.

2. The method according to claim 1, wherein the molded article is suctioned in via openings of a first mold surface after molding.

3. The method according to claim 1, wherein the relative overpressure and / or the relative underpressure is maintained when the mold is open.

4. The method according to claim 1, wherein the undercut has a depth of 0.05 to 1 mm.

5. The method according to claim 1, wherein the relative overpressure generated is from 1.2 to 6 bar.

6. The method according to claim 1, wherein the mold cavity has an offset of less than 2 mm.

7. The method according to claim 1, wherein the relative overpressure and / or the relative underpressure is modified.

8. The method according to claim 1, wherein the relative underpressure is provided by generating a vacuum.

9. The method according to claim 1, further comprising discharging compressed air via the openings in the second mold surface.

10. The method according to claim 1, wherein more openings are provided at the mold surfaces in a region of the undercut than on the remaining regions of the mold surfaces.

11. The method according to claim 1, wherein a greater relative overpressure and / or relative underpressure is generated in a region of the undercut compared to remaining regions of the mold surfaces.

12. The method according to claim 1, wherein a first mold half with the first mold surface forms a negative side of the mold and a second mold half with the second mold surface forms a positive side of the mold.

13. The method according to claim 1, wherein the molded material of the formed molded article is elastically compressed at least in an undercut region of the molded article by the overpressure acting on the molded article and underpressure acting by suction when opening the mold.

14. A mold for forming molded articles, comprising a first mold half with a first mold surface and a second mold half with a second mold surface, wherein the mold, in its closed state, forms a mold cavity between the first mold surface and the second mold surface for forming a molded article, and wherein the first mold surface and the second mold surface have openings via which an overpressure and an underpressure are configured to be generated in the mold cavity and at the molded article, wherein the mold is configured to perform the method for forming molded articles according to claim 1.

15. A molded article made of a fibrous material manufactured according to the method of claim 1, wherein the molded article has an undercut of 0.05 to 0.5 mm.

16. The molded article according to claim 15, wherein the undercut is formed by an accumulation of moldable material and has a greater wall thickness compared to adjacent regions.

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