Mold for manufacturing cushioning elements for sportswear

Abstract

One aspect of the invention relates to a mold for manufacturing a cushioning element of a sports garment. Further aspects of the invention relate to a mold insert used in the mold, a method of manufacturing a cushioning element for a sports garment using such a mold, and a cushioning element manufactured by such a method. A mold for manufacturing a cushioning element of a sports garment is provided, wherein the cushioning element is manufactured from particles of an expanding material, and wherein an electromagnetic field is used as an energy carrier to fuse the particle surfaces. The mold insert used in the mold has been manufactured using an additive manufacturing method, and the mold insert is adapted to locally adjust the field strength of the electromagnetic field inside the mold cavity of the mold based at least partially on the geometry of the cushioning element.

Description

[0001] This application is a divisional application of the Chinese Invention Patent Application with the application date of October 15, 2020, the application number of 202011101883.7, and the invention name of “Mold insert for use in a mold for manufacturing a cushioning element of a sports garment”. TECHNICAL FIELD

[0002] The invention relates to a mold insert for use in a mold for manufacturing a cushioning element of a sports garment, in particular for manufacturing a shoe sole or a shoe midsole, wherein the cushioning element is manufactured from particles of an expanded material, and wherein an electromagnetic field is used as an energy carrier to fuse the particle surfaces. The invention also relates to a mold using such a mold insert.

[0003] The invention also relates to a method for constructing such a mold insert using an optimization method, and to a method for manufacturing a mold insert constructed in this way.

[0004] Furthermore, the invention relates to a method for manufacturing a cushioning element of a sports garment, in particular a shoe sole or a shoe midsole, from particles of an expanded material, wherein an electromagnetic field is used as an energy carrier to fuse the particle surfaces, and wherein the method uses such a mold. The invention also relates to a cushioning element, in particular a shoe sole or a shoe midsole, manufactured by such a method. BACKGROUND

[0005] In recent years, it has been found that the use of a particle foam material, i.e. a material made from individual particles of an expanded plastic material, can be used for manufacturing a cushioning element of a sports garment, in particular for manufacturing a shoe sole of a sports shoe. In particular, it has been considered to use expanded thermoplastic polyurethane (eTPU) particles for manufacturing a shoe sole, which particles are fused at their surfaces by subjecting them to pressurized steam within a mold (commonly referred to in the art as “steam chest molding”). In this context, the use of eTPU particles is advantageous, because the use of eTPU particles can result in a shoe sole having a low weight, a good temperature stability and a small hysteresis loss for the energy exerted by the deformation of the shoe sole during running, i.e. a good energy resilience for the wearer of the shoe.

[0006] However, in order to obtain a high-quality dimensionally stable component, it is also necessary to provide thermal energy to the interior of the component in order to obtain a sufficient degree of fusion between the particles. For thermal energy provided by steam (or, even worse, when using a liquid adhesive material, which has also been considered), this is only possible when the particles in the mold reach a certain thickness and packing density and exceed a certain “threshold” thickness or density, which steam chest molding usually results in defects, in particular in the interior of the component.

[0007] Another disadvantage of using steam as energy carrier is that a large portion of the energy stored in the steam can be lost by heating the mold instead of being supplied to the particle surfaces. On the one hand, this can require a longer preheating phase until the mold, usually made of a metallic material, is heated to the saturation temperature, on the other hand, this can delay the stabilization and cooling of the fused component, since the mold can have stored a large amount of thermal energy which delays the cooling. Furthermore, due to the usually large size of conventional molds, this leads to a slow heating of the mold and a significant accompanying energy consumption. Thus, the method can be time-consuming and very energy-inefficient.

[0008] To solve these disadvantages, therefore, energy carriers other than pressurized steam have been considered. In particular, a method for manufacturing a cushioning element of an article of sports apparel is described in DE 102015202013 Al and EP 3053732 Al, which comprises packing a mold with a first material comprising particles of an expanded material and fusing the particle surfaces by providing energy in the form of at least one electromagnetic field.

[0009] However, the methods disclosed in these two applications still leave room for improvement, since they do not sufficiently take into account the complex geometries of the components which modern performance footwear, such as running shoes, usually comprise, in particular when it comes to their soles and midsoles. The complex geometries of these components, in turn, pose very high demands on the manufacturing equipment and the manufacturing method. For the case of using a particle foam material in the soles and midsoles, this means that a uniform and stable connection between the particle surfaces must be ensured for sole geometries which have significant variations in thickness, curvature, contour, etc., in all areas of the sole and throughout the interior of the sole. With the known methods and machines, this can be difficult to achieve or even impossible in some cases.

[0010] Based on the described prior art, it is therefore a problem of the present invention to provide an improved tool and method for manufacturing a cushioning element of an article of sports apparel from particles of an expanded material and using an electromagnetic field as energy carrier, which allows for manufacturing high-quality products with complex geometries. Another problem solved by the present invention is to provide an improved method of manufacturing such a tool. SUMMARY

[0011] The different aspects of the present invention address the above-mentioned problems and at least partially solve them.

[0012] A first aspect of the present invention relates to a mold insert. In one embodiment, a mold insert for use in a mold for manufacturing a cushioning element of an article of sportswear, in particular for manufacturing a shoe sole or midsole, is provided, wherein the cushioning element is manufactured from granules of an expanded material, and wherein an electromagnetic field is used as an energy carrier to fuse the granule surfaces. The mold insert has been manufactured using an additive manufacturing method, and the mold insert is adapted to locally adjust a field strength of the electromagnetic field inside a mold cavity of the mold at least partially based on a geometry of the cushioning element.

[0013] One advantage of using an electromagnetic field (in the following sometimes simply referred to as "field" for brevity) in particular electromagnetic radiation as an energy carrier in the fusion of granules of an expanded material compared to using steam is that the energy provision by the electromagnetic field is not coupled with a mass transfer. Thus, the electromagnetic field can more easily penetrate the interior of the part being molded, and thus lead to a uniform and consistent fusion of the granules throughout the part, under certain conditions, e.g. the mold is not completely or predominantly made of metal or another electrically conductive material. In general, the electromagnetic field leads to a dielectric heating of the granules and the granule surfaces, which then fuse together to form the molded part.

[0014] For parts with a "regular" geometry, like a simple material plate with a constant thickness throughout and using only one material, e.g. granules of an expanded material, the surface of the material, e.g. the surface of all granules, will be heated very uniformly, leading to a uniform and consistent fusion throughout the plate.

[0015] However, for parts such as cushioning elements with a complex geometry, e.g. shoe soles as often encountered in modern performance shoes, the situation becomes more complex. Due to the complex geometry of the cushioning element, the areas of the mold cavity in which the cushioning element is manufactured will also have varying thicknesses, curvatures, profiles, etc. This will typically distort the electromagnetic field that penetrates the mold and the mold cavity, and lead to an increase of the field strength in certain areas, while other areas can suffer from "dilution", i.e. a decrease of the field strength of the electromagnetic field. Since the energy density in the electromagnetic field is (not taking into account the magnetic contribution, and wherein is the electric field, is the electric displacement field), this means that the granules in areas of increased field strength are provided with more energy compared to areas of decreased field strength. This will lead to an uneven and inconsistent fusion of the granule surfaces, and ultimately to a defective and unacceptable end product.

[0016] To solve this problem, the mold insert of the present invention is shaped in a way that at least partially compensates for this effect. In principle, two options are possible in this regard:

[0017] First, the mold insert can be placed into the mold in such a way that it locally adjusts the field strength inside the mold cavity without affecting the geometry of the mold cavity. For example, the insert can be "sandwiched" between other parts of the mold.

[0018] Second, the mold insert can not only locally adjust the field strength inside the mold cavity, it can itself define at least a portion of the mold cavity. For example, the mold insert can be arranged directly adjacent to the mold cavity and form a portion of the wall of the mold cavity (or it can at least define the geometry of a portion of the mold cavity, but for example be further coated or covered by additional material layers).

[0019] In any case, there is an interaction between the mold insert and the geometry of the manufactured part, for example the above-mentioned cushioning element. The interaction is such that the mold insert takes into account the geometry of the cushioning element (and thus of the mold cavity) and adjusts the electromagnetic field specifically to this geometry and as needed to achieve the desired fusion of the expanded particles. This is the meaning of "adjusting the electromagnetic field based at least in part on the geometry of the cushioning element". Of course, other factors must also be taken into account in general, such as the geometry and material of the rest of the mold and / or the kind of electromagnetic field used. Thus, the adjustment will be "only partially" based on the geometry of the cushioning element. However, the mold insert is tailored to the specific geometry of a given cushioning element, and different inventive mold inserts will typically be used for different part geometries.

[0020] Another factor that must be taken into account in this regard is the kind of particles used. Although the mold insert can initially be designed to adjust the electromagnetic field in the empty mold cavity in the desired way (for example, as a first-order approximation in the design of the mold insert), the ultimate goal is to adjust the field as desired in the filled state of the mold, since it is in this state that the electromagnetic field delivers its energy to the particle surfaces for their fusion (and typically also to their overall volume). Since the particles themselves have certain dielectric properties, for example, which typically vary with the different base compounds from which the particles are manufactured, these properties should advantageously be taken into account in the design of the mold insert in order for the electromagnetic field to have the desired distribution throughout the filled mold cavity during the actual fusion process.

[0021] The particles of the expanded material for the cushioning element can comprise at least one of the following materials: expanded thermoplastic polyurethane (eTPU), expanded polyamide (ePA), expanded polyether block amide (ePEBA); expanded polylactide (ePLA); expanded polyethylene terephthalate (ePET); expanded polybutylene terephthalate (ePBT); expanded thermoplastic polyester ether elastomer (eTPEE).

[0022] For example, for the purpose of manufacturing shoe soles, particles of eTPU, ePEBA and / or ePA have proven to be advantageous and can thus be used in the context of the present invention.

[0023] To allow for the desired adjustment, it is particularly suitable to create the mold insert with an additive manufacturing process. Additive manufacturing processes allow for a fine-tuned control not only of the general geometry of the mold insert but also of its interior, which can play an important role in providing the desired "deformation" to the electromagnetic field. Furthermore, modern additive manufacturing processes allow for the manufacturing of components in a very short time frame and on site, so that the product development process is not stopped (at least not for long) due to having to wait for the manufacturing of a manufacturing tool or a re-manufacturing / adaption, which often delays the process by days or even weeks.

[0024] Designing a mold insert for additive manufacturing can involve one or several options and approaches, wherein a combination is of course also possible. Due to the fact that additive manufacturing is used, the simplest case is a simple trial-and-error approach, which is feasible due to the short time that is spent from providing a design of the mold insert until the manufactured mold insert is finished. A second approach is to use computer simulations of the electromagnetic field distribution (e.g. local field strength) through the mold, in particular the mold insert and the mold cavity.

[0025] One possibility to design a mold insert can use the desired target distribution of the electric displacement field in the (filled) mold cavity as a starting point. As known from standard electrodynamics, the electric displacement field describes the combined effect of an externally applied electric field and the polarization effect induced by the external field inside a dielectric material, and in this sense, the electric displacement field represents the "effective field" inside the material. Thus, in the context of the present invention, the electric displacement field is the suitable quantity to consider for specifying the design target of the mold insert. However, other "target functions" (e.g. the desired distribution of the electric field are also possible.

[0026] As further described below, the local adjustment of the field strength inside the mold cavity can (e.g. at least partially) be caused by local variations of the (relative) permittivity of the mold insert, which in turn can be influenced by local variations of the density of the material of the mold insert. Furthermore, the materials or material mixtures used in different parts and regions of the mold insert are also able to influence the permittivity of the mold insert and thus the field distribution inside the mold cavity.

[0027] As also described in further detail below, the mold insert is manufactured using an additive manufacturing method (e.g., 3D printing or deposition technique), which typically involves controlling the fill or feed rate at which material is supplied to the "print head" of the additive manufacturing device, as well as the composition of the material used for the additive build process of the mold insert.

[0028] Hence, the optimization process for designing the mold insert can be based on the fill or feed rate and the material composition or "mixing rule" as input parameters, as well as the above-mentioned objective function as design goal, e.g., the desired electric displacement field in the (filled) mold cavity To perform the optimization, the structure or shape of the (currently unknown) mold insert can be discretized, e.g., into a grid of cells or pixels, and at each grid location, the local density of the mold insert can be varied and optimized as a function of the fill rate and mixing rule by calculating the field distribution within the mold cavity resulting from a given distribution of local densities at the grid location using the dielectric heating equation (other physical parameters besides the local density can also be included in the optimization process). By varying the density distribution over the grid, the influence on the resulting field distribution within the mold cavity can be investigated, and hence the optimal configuration can be selected or determined (e.g., by minimizing an "energy function"). Since the local density is in turn specified as a function of the fill rate and mixing rule, the density distribution obtained as a result of the optimization process can finally be converted into a set of parameters and instructions that allow the optimized mold insert or structure to be manufactured by using an additive manufacturing method.

[0029] In any case, once the design has been created on the computer, it can be quickly manufactured, for example, and then verified by a test run on the actual machine, and further adjusted or changed if necessary, subsequently. Since additive manufacturing processes are used, it is possible that the entire process from the first design to an acceptable tool can be completed in a short period of time of a few weeks or even days.

[0030] In particular, the mold insert can be adapted to increase the uniformity of the field strength in the entire mold cavity during the manufacturing of the cushioning element.

[0031] Since the energy density in an electromagnetic field is (again neglecting the magnetic contribution), a uniform field strength will promote a uniform fusion of the particles in the entire cushioning element, such that homogenizing the field is particularly suitable for obtaining a cushioning element with a consistent and uniform fusion of the entire particle surface.

[0032] On the other hand, by reversing the argument, it is also clear that the mold insert can be used to create specific regions (e.g. local values of the field strength) in the field distribution, in which an increased or decreased amount of fusion will occur (assuming the same particles are used everywhere; otherwise the varying composition of the particles will also have an effect on the amount of fusion). This is desirable for providing different regions of the cushioning element with different performance characteristics (e.g. stiffness).

[0033] The local adjustment of the field strength inside the mold cavity can be caused at least in part by a local variation of the dielectric properties of the mold insert.

[0034] Of course, first of all, a variation of the dielectric properties of the mold insert will typically change the field inside the mold insert itself. However, contrary to the ideal case of an infinitely large plate capacitor, in which a plate of dielectric material is inserted and the field outside the dielectric material remains unchanged due to the formation of a "just the right amount" of polarization charge at the surface of the plate of dielectric material, in the case of a mold insert of finite size with typically complex geometry, there is also an influence on the electromagnetic field outside the mold insert itself, in particular the electromagnetic field inside the mold cavity. This is true in particular if the mold insert is arranged directly adjacent to the wall of the mold cavity or even forms part of the wall of the mold cavity. In this sense, the mold insert can be considered a "dielectric lens" of the electromagnetic field, which changes its distribution throughout the mold cavity.

[0035] In particular, the local adjustment of the field strength inside the mold cavity can be caused at least in part by a local variation of the dielectric constant of the mold insert.

[0036] As understood by the skilled person, the dielectric constant of the mold insert has a direct influence on the field strength inside the mold insert (for a constant "external" field applied to the mold) and, due to the above-mentioned effects, will also influence the field distribution (e.g. local values of the field strength) inside the mold cavity. A further advantage of using the dielectric constant as a "control knob" to influence the field distribution is that materials with various values of the dielectric constant are known and available, such that a large degree of adjustment and adaptation can be made in this way by selecting and / or combining different materials in the additive manufacturing process.

[0037] The local variation of the dielectric constant of the mold insert can be caused at least in part by a local variation of the density of the material of the mold insert.

[0038] Another advantage of using the dielectric constant to adjust the field is that, in addition to using different materials with different intrinsic dielectric constant values, it is possible to use the same material in different areas of the mold insert, but with different densities, to obtain the desired effect. The density can be a "strictly local" density measured in areas of the mold insert that are as technically small as possible, for example, the density of a sample cube with edges of 1 mm length, or it can be an "average" density measured on a large distance scale, for example, an average of the density determined from sample cubes with edges of, for example, 5 mm length or 10 mm length. Since additive manufacturing is used to manufacture the mold insert, such density variations are further relatively easy to implement, so that a combination of these two aspects is particularly advantageous.

[0039] For example, one way to obtain such local variations in the density of the material of the mold insert is by including air cavities within the material. The ability to create complex distributions of air cavities is a particular advantage of using additive manufacturing for the mold insert. Including such air cavities is therefore an important option provided by the present invention to locally adjust the material density, and thus the dielectric constant, and thus the field distribution within the mold cavity.

[0040] Generally, a higher density of the material of the mold insert leads to a higher dielectric constant of the mold insert.

[0041] The local density of the material of the mold insert can be between 0.4 g / cm 3 and 1.7 g / cm 3 .

[0042] For the materials that can be used for additive manufacturing of the mold insert of the present invention, discussed in more detail below, these values are on the one hand technically achievable without too much difficulty and on the other hand lead to a favorable compromise between, for example, the heating of the mold itself and the degree of influence on the field inside the mold cavity of the mold insert. If the density is too low, the mold insert will generally not heat sufficiently, which will be detrimental to the fusion, and if the density is too high, the mold insert will heat too much and thus, for example, unnecessarily prolong the fusion and subsequent cooling / solidification process.

[0043] For example, suitable values for the local dielectric constant can be between 1 and 20.

[0044] Alternatively or additionally, the local adjustment of the field strength within the mold cavity can be caused at least in part by a local variation of the dielectric loss factor of the mold insert.

[0045] In contrast to the case of a local change in the dielectric constant, a local change in the dielectric loss factor of the mold insert can not (or only to a more limited extent) have a direct influence on the field distribution, in particular outside the mold insert and within the mold cavity. However, a local change in the dielectric loss factor of the mold insert can lead to different degrees of energy absorption and thus to different degrees of heating of different regions of the mold insert. Since the dielectric constant is generally a function of temperature, these different degrees of heating of different regions of the mold insert can cause a local change in the dielectric constant, which in turn can cause a local adjustment of the field also outside the mold insert, in particular within the mold cavity.

[0046] On the other hand, due to the different degrees of heating, a local change in the dielectric loss factor of the mold insert can also have a more direct influence on the fusion of the particle surfaces, in that the energy emitted in the form of thermal radiation into the mold cavity is different. The closer the mold insert is arranged to the mold cavity, the more pronounced this influence is generally, and this influence also generally has a greater influence on the fusion of particles arranged at the surface of the cushioning element and facing the mold insert than on particles arranged inside or on different sides of the cushioning element. Thus, this process can be used intentionally, for example, to provide a surface layer of a region of the cushioning element with specific properties. For example, particles in a surface layer of the cushioning element can be fused more strongly in a region adjacent to a portion of the mold insert, in which region they have a high dielectric loss factor and thus emit a large degree of heat into the direction of the mold cavity. For example, such more strongly fused particles can provide an increased stiffness of the respective region of the cushioning element after cooling.

[0047] Furthermore, while excessive energy loss caused by undesired heating of the mold is generally to be avoided, a certain degree of heating of the mold and in particular of the mold insert can be desirable. Such preheating can be used to preheat the particles of the expanding material before they actually fuse, which can widen the processing window and generally facilitate the fusion process.

[0048] For example, the local dielectric loss factor of the mold insert can be between 0.01 and 0.10, in particular between 0.01 and 0.07.

[0049] This range has proven to be suitable, as it provides a good compromise between the level of energy absorption of the mold insert and sufficient heating of the mold insert to promote fusion, i.e. on the one hand the mold insert does not absorb too much energy, and on the other hand the mold insert is heated enough to promote fusion of the particle surfaces as described above.

[0050] Other values are possible, however it can be up to 0.3. For example, using polyvinylidene fluoride (PVDF), also known as polyvinylidene difluoride, in the structure of the mold insert, a value of 0.2 or even higher can also be achieved. This can allow, for example, a particularly "visible" modification of the field distribution in parts or locations of the mold cavity where this is necessary or considered advantageous.

[0051] As already mentioned, the mold insert can be arranged adjacent to the mold cavity and thus influence the geometry of the mold cavity. In particular, in this case, the local variation of the dielectric loss factor is then also able to influence the amount of surface heating of the surface of the mold insert adjacent to the mold cavity during the manufacture of the damping element.

[0052] Thus, the mold insert can serve a dual or even triple role, as it not only influences the distribution of the electromagnetic field, but also serves to (partially) define the geometry of the damping element and can even influence the temperature inside the mold cavity, which is an important parameter in the fusion process.

[0053] For example, the additive manufacturing method for the mold insert can comprise at least one of the following methods: 3D printing; micro-droplet-based methods; powder-bed-based methods; stereolithography, SLA; selective laser sintering, SLS; selective laser melting, SLM; continuous liquid interface production, CLIP; fused deposition modeling, FDM; digital light processing, DLP; multi jet modeling, MJM; polyjet methods; film transfer imaging methods, FTI; electron beam melting, EBM; electron beam additive manufacturing, EBAM; subtractive rapid prototyping, SRP.

[0054] At least one of the following materials can be used for the mold insert: ceramic-filled resin; cyanate ester; polylactic acid / polylactide, PLA; acrylonitrile butadiene styrene, ABS; polyamide 6 / nylon 6, PA6; polyamide 66 / nylon 66, PA66; polyamide 12 / nylon 12, PA12; polyether ether ketone, PEEK; adhesive system; epoxy resin; UV-curing thermoset.

[0055] Combinations of different methods and / or different materials are also possible.

[0056] The electromagnetic field can provide the energy to fuse the particle surfaces in the form of electromagnetic waves in the radio frequency part of the 30 kHz to 300 MHz spectrum, or in the form of electromagnetic waves in the microwave part of the 300 Mhz to 300 Ghz spectrum, in particular in the form of electromagnetic waves with a frequency in the range of 25 to 30 MHz.

[0057] For many reasons, it is advantageous to use these kinds of radiation. First, radio frequency and microwave generators are both commercially available and can be implemented into the manufacturing tool with relatively little effort. Furthermore, the radio frequency or microwave radiation can be focused approximately onto the mold cavity, so that the energy efficiency of the method increases. Moreover, the intensity and frequency of the radio frequency or microwave radiation can be easily changed and adapted to the respective requirements. In particular, the use of radiation with a frequency in the range of 25 to 30 MHz has proven to be advantageous in the context of the present invention. In combination with the above-described materials and mechanisms with respect to the mold insert of the present invention, this frequency range allows for a good control of the field distribution within the mold cavity.

[0058] The cushioning element can in particular be a sole for a shoe, more particularly a midsole.

[0059] As mentioned above, currently soles, in particular midsoles, often have a rather complex geometry. The use of the mold insert of the present invention in the manufacture of such elements in particular enables the advantages of the present invention.

[0060] Another aspect of the present invention relates to a mold. In one embodiment, a mold for manufacturing a cushioning element for an article of sportswear from particles of an expanded material is provided, wherein an electromagnetic field is used as an energy carrier to fuse particle surfaces. The mold comprises an embodiment of the mold insert of the present invention.

[0061] It goes without saying that all features, combinations of features, options and possibilities described in the present application in relation to the mold insert can also be applied to the case of a full molding tool and also in the manufacturing method described herein.

[0062] In one embodiment, the mold comprises at least two mold portions, and each of the two mold portions comprises electrodes for providing the electromagnetic field. The mold insert is placed into one of the two mold portions, and the two mold portions can be moved relative to each other in a first direction to open the mold to allow loading of particles into the mold, and the two mold portions can also be moved relative to each other in a second direction to close the mold so as to form a mold cavity between the electrodes.

[0063] This setup allows for an easy exchange of the mold insert and a general operation of the mold. In particular, in case the mold insert at least partially also defines the geometry of the mold cavity, the same overall tool can be used with different mold inserts for manufacturing a plurality of different cushioning elements.

[0064] It is also possible to use a mold insert that completely surrounds the mold cavity, for example a mold insert having a first part (e.g. a top part) and a second part (e.g. a bottom part) that are put into two mold parts (e.g. using a mold having an upper mold part and a lower mold part).

[0065] However, it is also mentioned that the tool itself can be adapted to suit the manufacture of a particular type or kind of cushioning element, for example a particular type of shoe midsole. In particular, the geometry of one or both electrodes can be such that the electromagnetic field generated has been substantially adapted for the manufacture of shoe midsoles (or some different type of cushioning element), and then the mold insert of the invention is used to further adapt the electromagnetic field on a more fine level, for example taking into account different shoe sizes, different overpronation / underpronation protection characteristics desired for the sole, different additional sole elements, such as torsion bars that can or can not be included in the sole, etc.

[0066] For example, the two mold parts or at least a part thereof described above can comprise a capacitor plate as an electrode, which can be arranged on the inside of the mold part (i.e. on the side of the part that faces the mold cavity). These mold parts can be composed of a layered structure, for example a base plate, a mold plate that defines at least part of the mold cavity, and an insulating layer on the inside (i.e. the side facing the mold cavity) of the mold plate. The capacitor plate can also be included in such a layered structure. Other layered structures are also conceivable.

[0067] In an embodiment, the thickness of the mold plate and / or the capacitor plate is varied. For example, by varying the thickness of the mold plate and / or the capacitor plate, the mold part can be profiled. This allows for fine-tuning of the energy to be applied to the shoe midsole (or some different type of cushioning element or part) in the tooling mold. Adjusting the capacitor plate can be preferred because it can allow the same mold plate to be kept, which can be more economical than adjusting the mold plate itself.

[0068] Of course, by using the mold insert of the invention together with two “standard” electrodes that are not specifically adapted to a particular product or product category, adaptation to these factors can also be achieved individually (but can be to a lesser extent). In this sense, using the mold insert of the invention can also help to expand the field of applicability of a standard molding tool or mold assembly.

[0069] Another aspect of the present invention is provided by a method of manufacturing a mold insert of the present invention by using an additive manufacturing process. The method can include an optimization process of the structure of the mold insert as described above, wherein a target function is specified and the mold structure is optimized to meet the specifications provided by the target function. In particular, the optimization process can take the fill rate and the material composition or mixing rules for the additive manufacturing process of the mold insert as input parameters and the desired electric displacement field in the (filled) mold cavity as a design goal. To perform the optimization, the structure or shape of the (currently unknown) mold insert can be discretized into a grid of cells or pixels and at each grid location, the local density of the mold insert can be varied and optimized as a function of the fill rate and the mixing rules by using the dielectric heating equation to calculate the field distribution within the mold cavity resulting from a given distribution of local densities at the grid location. The optimized local density distribution can then be converted into a set of parameters and / or instructions used by the additive manufacturing machine to create the mold insert using the determined fill rate and mixing rules.

[0070] The following will explain in detail exemplary embodiments of the optimization process of the structure of the mold insert described above:

[0071] An additive manufactured version of a processing mold for a dielectric heating process can be constructed. Within the processing mold, a complex 3D shape of an additive manufactured structure comprising a plurality of mold inserts of different heights, widths, and material densities can be shaped to form a mold cavity. Within the mold cavity, a part made of expanded thermoplastic elastomer (eTPE), such as particles of expanded thermoplastic polyurethane (eTPU) for the cushioning element described above, can be manufactured. The additive manufactured processing mold itself can comprise electrically conductive aluminum electrodes, such as an anode and a cathode, and a dielectric mold insert material surrounding the material of the part.

[0072] Initially, the dielectric mold insert can be printed with a material fill rate of 100%, i.e., the dielectric mold insert can be formed of a full density of the selected dielectric mold insert material. For example, polylactic acid / polylactide, PLA; acrylonitrile butadiene styrene, ABS; polyamide 6 / nylon 6, PA6; polyamide 66 / nylon 66, PA66; polyamide 12 / nylon 12, PA12; polyether ether ketone, PEEK; polyethylene terephthalate, PET; PE materials; polytetrafluoroethylene, PTFE; adhesive systems; epoxy resins; UV-curing thermoset materials can be used.

[0073] When checking the performance of the processing mold structure by using finite element method (FEM) simulation methods that provide other relevant process parameters (e.g. the frequency of the provided A / C voltage generated by the electromagnetic field generator and the voltage value applied between the anode and the cathode), the electric field strength occurring within the dielectric mold insert material and within the part material can be calculated based on Maxwell's equations. This initial calculation can reveal a non-uniform distribution of the electric field strength, whereby the electric field strength within the part can be highest in areas of lower material density of the part material and can be correspondingly lower in areas of high material density.

[0074] In order to average the observed differences in the occurring electric field strength, the optimization process according to the present application can be used to design the topology of the additively manufactured dielectric mold insert. Here, the volume integral function of the normalized electric field distribution on the part within the mold cavity can be calculated. This value can be denoted by E av For each point in the corresponding normalized field distribution, the following objective function Phi,

[0075]

[0076] where E pp may be the electric field strength density calculated for each infinitesimal point in the mold cavity. In order to optimize the material density occurring within the dielectric mold insert, a topology optimization density model can be applied to all such volume regions of the mold insert geometry. The domain control variable can be discretized on nodes or elements and a fictitious material can be introduced in order to implicitly state the material boundary. An interpolation can then be constructed such that wherever the control variable can equal one, the physical control equation can be solved, while when the control variable can equal zero, the equation associated with the fictitious material can be solved. The interpolation can be specific to the physical properties and can be constructed such that intermediate values of the control variable can be suboptimal.

[0077] By applying the Lykknes equation, the bulk material permittivity of the target optimization domain is obtained by the following equation:

[0078]

[0079] where v i is the volume fraction of the i-th constituent, ε i is the permittivity of the i-th constituent, n is the number of total constituents in the part material, and the total volume fraction in the equation is given by The mold insert material model for the finite element method simulation can be modified during the optimization iteration to produce a change in the permittivity values of the mold insert material. The output density model values (0 < θ c<1), the simulation model can produce an integral solution of the dielectric field strength for each iteration of the optimization cycle.

[0080] Termination of the optimization method can occur by either converging to the solution to a set optimality tolerance or by reaching a set maximum number of model evaluations. The final result of the optimization process can be a density map across the dielectric mold insert material producing a value of the topological optimization density model variable at each point of the volume integral across the dielectric mold insert material which can in turn create a local modification of the source material model properties based on the relationship represented by the Lykkenikov equation for the bulk material dielectric constant of the target optimization domain.

[0081] Success of the optimization process can be assessed by calculating the dielectric field strength across the mold cavity of the component using the modified material dielectric constants of the material matrix obtained as output of the density model of the optimization process and comparing this field strength to the original objective function Phi

[0082] The skilled person will understand that the example implementation is merely one way of implementing the optimization process according to the present application and that other methods, algorithms or approaches can also be applied.

[0083] Yet another aspect of the present application relates to a manufacturing method for a cushioning element of an athletic garment, in particular a shoe sole or midsole. In one embodiment, a method for manufacturing a cushioning element of an athletic garment from particles of an expanding material is provided, wherein an electromagnetic field is used as an energy carrier to fuse the particle surfaces, and wherein the method uses an embodiment of the mold of the present application.

[0084] Further aspects of the present application relate to a cushioning element, in particular a shoe sole or midsole manufactured with an embodiment of the manufacturing method of the present application, and to a shoe, in particular an athletic shoe, comprising such a shoe sole or midsole.

[0085] As mentioned above, by using the mold insert of the present application, a cushioning element can be manufactured having a complex geometry which still has the desired fusion and connection between the entire particles, as the mold insert allows to adjust and adapt the distribution of the electromagnetic field (e.g. the local field strength) within the mold cavity and during the molding process in such a way that the desired degree of fusion is locally achieved in a controlled manner. This can provide a significant advantage over known methods in which no such mold insert is used, in which such local control can be difficult or even impossible. BRIEF DESCRIPTION OF DRAWINGS

[0086] Possible embodiments of the present application are further described below with reference to the accompanying drawings:

[0087] Figure 1 ​: Explains the technical complexity of producing cushioning elements with complex geometries from particles of expanded material using electromagnetic fields as energy carrier for particle surface fusion;

[0088] Figure 2 : An embodiment of the mold insert of the present invention;

[0089] Figure 3 : the dielectric constant of the material suitable for the mold insert of the present invention; and

[0090] Figure 4 : Figure 4 The dielectric loss factor of the material. DETAILED DESCRIPTION

[0091] The following detailed description, primarily of tools and methods for manufacturing shoe soles, describes possible embodiments of various aspects of the present invention. However, it should be emphasized that the present invention is not limited to these embodiments. Rather, it can also be used for various types of cushioning elements in sports equipment, sports footwear, and sportswear (e.g., knee or elbow pads).

[0092] Further reference is made to the fact that only various embodiments of the present invention may be described in more detail hereinafter. However, it will be understood by those skilled in the art that the optional features and possible modifications described with reference to these specific embodiments may also be further modified and / or combined with one another in different ways or in different sub-combinations without departing from the scope of the present invention. If individual features are not required to achieve the desired result, they may also be omitted. Therefore, to avoid repetition, reference is made to the explanations in the previous sections, which also apply to the detailed description below.

[0093] Figure 1 The technical complexities that may arise when an electromagnetic field is used as an energy carrier for fusing particles of expanded material at their surface in the production of a cushioning element having complex geometrical features are schematically illustrated.

[0094] exist Figure 1 The upper left portion of the tool, generally designated by the reference numeral 100, shows a simplified diagram of a simple sheet 110 of material having a constant thickness, using an electromagnetic field (indicated by arrows 130) as an energy carrier to fuse the surfaces of a plurality of particles 140 of expanded material in a die 120. Due to the constant thickness of the sheet 110 and its simple geometry, the electromagnetic field is substantially uniform throughout the tool, as indicated by the constant thickness of the arrows 130, and the fusing of the surfaces of the particles 140, caused by their dielectric heating by the electromagnetic field, is therefore generally uniform and consistent.

[0095] exist Figure 1In the upper right part, as a contrast, generally indicated by reference numeral 150, a part 160 is depicted which is also made of granules 140 of expanded material, but now has a more complex geometry, here in the case of different thicknesses of the part 160 in different areas 161, 162 and 163. Due to this complex geometry of the mould cavity of the tool for the manufacture and the resulting shape, the strength of the electromagnetic field used for the fusing of the granules 140 is no longer constant throughout, but varies between the different areas 161, 162 and 163, as indicated by the different thicknesses of the arrows 131, 132 and 133 which represent the field in these different areas. As a result, while in one area, for example in the middle area 162, a uniform and consistent fusing of the surface of the granules 140 can still be achieved, in the remaining areas 161 and 163 the surface of the granules 140 can only show a low degree of fusing or can even not sufficiently fuse (i.e. the granule foam part generally indicated by reference numeral 171), or they can show too high a degree of fusing and be over-fused or even burnt (i.e. the granule foam part generally indicated by reference numeral 173).

[0096] To solve this problem of potentially inconsistent and non-uniform fusing of the surface of the granules for cushioning elements having a complex geometry, the present invention provides an additively manufactured mould insert for at least partially compensating for this effect by adjusting the electromagnetic field which penetrates the mould cavity.

[0097] Figure 2 Possible embodiments 210, 220 and 230 of the mould insert of the present invention are depicted. In all three embodiments, the mould insert is depicted as completely closing the mould cavity (but it should be noted that in each case only a two-dimensional cut through the three-dimensional mould insert is shown which cannot capture all the details of the three-dimensional shape of the respective mould insert). It should be noted that generally the mould inserts 210, 220, 230 will be separable into at least two parts, for example a top part and a bottom part, so that the mould cavity can be loaded with granules and the fused part removed from the mould. However, for the sake of simplicity, such separation lines between the different parts of the mould insert are not shown in the drawings. Figure 2

[0098] It should also be mentioned that the mould insert of the present invention can for example also be provided as an insert for only the upper part or the lower part of a mould in which the mould insert is used (such a mould will be described in more detail below), and thus only interfaces with the mould cavity on one side. As already mentioned, the mould insert of the present invention can even be incorporated into the mould at a location which is not directly adjacent to the mould cavity, but which influences the field distribution within the mould cavity. While these possibilities are not further discussed in more detail below, they also form part of the present invention.

[0099] ​The mold insert 210 comprises only one type of material. However, even if the entire mold insert 210 is made of the same material, the material of the mold insert 210 can still "twist" the penetrating electromagnetic field in a desired manner, as the material has different thicknesses in different regions. In addition, the effect can be further enhanced using local variations in density, for example.

[0100] The mold insert 220 builds on the general structure of the mold insert 210, but now uses different materials in different regions of the mold insert 220. The different materials are referred to as "Material A", "Material B", and "Material C" in Figure 2 In addition to using these different materials, the dielectric properties (e.g. permittivity, dielectric loss factor) can also be locally varied within one of the given material regions. "Material A", "Material B", and "Material C" can be chosen, for example, from the materials discussed herein, in particular from the materials discussed in the context of Figure 3 and Figure 4 with the further restriction that the dielectric loss factor should be larger than 0.01 (more details on this will follow below).

[0101] Finally, the mold insert 230 further builds on the general structure of the mold insert 220, where now three different material structures (made of the same material or different materials, e.g. made of the three different materials "Material A", "Material B", and "Material C" of the mold insert 220) are employed in different regions. The different material structures are referred to as "Structure A", "Structure B", and "Structure C" in Figure 2 Here, the additive manufacturing of the mold insert of the present invention is advantageously implemented, as such a method allows to create complex and "open" (i.e. comprising cavities, channels, etc.) internal structures, which might otherwise not be realizable. Such internal structures can in particular help to vary the local density and / or the local dielectric properties of different regions or segments of the mold insert 230, and thus to vary the way the mold insert influences the penetrating electromagnetic field. As one possible example, the three different structures can comprise different (average) sizes of air cavities, leading to different (average) densities of the mold insert 230 in the respective regions, and thus to different permittivity values.

[0102] In addition to the three different regions or segments, the mold inserts 220 and 230 can also comprise a different number of regions or segments, e.g. 2 or 4 or 5. The number of different regions or segments can also differ between the top and bottom portions of the insert (for an insert having a top and bottom portion). Moreover, the materials used in the top and bottom portions need not correspond or be the same, but can also be at least partially different.

[0103] As mentioned above, the mold inserts 210, 220 and 230 can be used for manufacturing cushioning elements of sports apparel from granules of expanded material, for example in a mold (not shown) for manufacturing a midsole of a sports shoe (e.g. a running shoe), wherein the electromagnetic field is used as energy carrier to fuse the granule surfaces.

[0104] Granules that can be used in the present application are in particular granules of expanded thermoplastic polyurethane (eTPU), expanded polyether block amide (ePEBA) and / or expanded polyamide (ePA), and mixtures thereof. These materials have proven to be advantageous for manufacturing shoe soles, for example, because of their good energy resilience and their temperature independence.

[0105] Additionally or alternatively, the granules can also comprise or consist of one or more of the following materials: expanded polylactic acid (ePLA), expanded polyethylene terephthalate (ePET), expanded polybutylene terephthalate (ePBT), expanded thermoplastic polyester ether elastomer (eTPEE), or mixtures thereof.

[0106] The mold can comprise an upper mold part and a lower mold part, which cooperate to define a mold cavity in which the cushioning element (e.g. a shoe sole) is molded.

[0107] One possibility is that the mold insert completely surrounds the mold cavity (e.g. the mold inserts 210, 220 and 230) and thus defines the geometry of the mold cavity. In this case, the bottom part of the mold insert can be placed into the lower mold part and the top part of the mold insert can be placed into the upper mold part.

[0108] Another possibility is that the lower mold part comprises a "die" or female mold, which cooperates with the mold insert of the present application, which is placed in the upper mold part and acts as a "plunger" or male mold to form the mold cavity when the mold is closed (or vice versa).

[0109] For the sake of completeness, it is again mentioned that the mold inserts of the present application can also be arranged at another position within the mold, for example as a layer or sublayer of the upper or lower part of the mold, without directly influencing the geometry of the mold cavity, but still for influencing and adjusting the way the electromagnetic field penetrates the mold cavity.

[0110] Instead of an upper mold part and a lower mold part, it is also possible to use for example inner and outer mold parts, or more than two mold parts can be used. Similar statements apply to the mold inserts covered by the present application.

[0111] For the sake of clarity, returning to the case of a mold having an upper mold part and a lower mold part, each of the two mold parts can comprise electrodes for providing an electromagnetic field. In the simplest case, the electrodes can simply be capacitor plates or metal plates with a simple geometry. However, in other embodiments, the electrodes can also have a shape that generally corresponds to the shape of the cushioning element to be manufactured in the mold, to "pre-form" the electromagnetic field for fusing the cushioning element. Further "tuning" of the electromagnetic field can then be achieved by the mold insert of the present invention.

[0112] The electromagnetic field generated between the electrodes can provide energy in the form of electromagnetic waves in the radio frequency part of the 30 kHz to 300 MHz spectrum, or in the form of electromagnetic waves in the microwave part of the 300 Mhz to 300 Ghz spectrum to fuse the particle surfaces. In one particular embodiment, it provides energy in the form of electromagnetic waves with a frequency in the range of 25 to 30 MHz to fuse the particle surfaces.

[0113] The two (or more) mold parts are movable relative to each other in a first direction (e.g. vertically away from each other) to open the mold and so as to allow loading of the mold with particles, and the mold parts are further movable relative to each other in a second direction (e.g. vertically towards each other) to close the mold to form a mold cavity between the electrodes.

[0114] During loading, the mold can be fully open and the two mold parts fully separated from each other, or the mold can be only partially open and open to an extent such that the two mold parts are still to some extent "engaged" with each other and limit the loading volume available for loading particles into. This "crack-gap loading" option can be used to influence the physical properties of the cushioning element that has been manufactured during loading, such as its density and stiffness, by controlling the amount of particles incorporated into the cushioning element and / or the degree of compression the particles are subjected to when the mold is fully closed. This can also allow different kinds of cushioning elements to be manufactured with the same mold by adjusting the crack-gap height (i.e. the extent to which the mold is open) during loading.

[0115] Returning to the discussion of the mold inserts of the present invention, such as the mold inserts 210, 220 and 230, encompassed by the present invention, a variety of different additive manufacturing methods and a variety of different base materials can be used for their manufacture.

[0116] For example, the additive manufacturing method can comprise at least one of the following methods and processes: 3D printing; micro-droplet based methods; powder bed based methods; stereolithography, SLA; selective laser sintering, SLS; selective laser melting, SLM; continuous liquid interface production, CLIP; fused deposition modeling, FDM; digital light processing, DLP; multi-jet modeling, MJM; multi-jet methods; film transfer imaging methods, FTI; electron beam melting, EBM; electron beam additive manufacturing, EBAM; subtractive rapid prototyping, SRP.

[0117] Furthermore, the mold insert can comprise at least one of the following materials: ceramic-filled resin; cyanate ester; polylactic acid / polylactide, PLA; acrylonitrile butadiene styrene, ABS; polyamide 6 / nylon 6, PA6; polyamide 66 / nylon 66, PA66; polyamide 12 / nylon 12, PA12; polyether ether ketone, PEEK; adhesive system; epoxy resin; UV-cured thermoset.

[0118] Using such methods and materials, the mold insert of the present invention can be adapted to locally adjust the field strength of the electromagnetic field inside the mold cavity of the mold at least partially based on the geometry of the cushioning element. In particular, the mold insert of the present invention can be manufactured and provided in such a way that it increases the uniformity of the field strength of the entire mold cavity during the manufacturing of the cushioning element.

[0119] As mentioned above, for cushioning elements having a complex geometry, the material distribution of the tool and / or the shape of the electromagnetic field generated by the tool can be such that the electromagnetic field penetrating the mold cavity is distorted in such a way that "cold spots" and "hot spots" are created during the fusing of the particles of the expanding material via the energy carried and supplied by the electromagnetic field. This can lead to an uneven and possibly even unacceptable end result of the fusing process. The mold insert serves to compensate for and at least partially eliminate this effect in order to improve the quality of the production result.

[0120] As already mentioned, the local adjustment of the field strength within the mold cavity can at least partially be caused by local changes in the dielectric properties of the mold insert.

[0121] Of course, as will be understood by the skilled person, other factors such as the frequency or intensity distribution of the generated electromagnetic field will typically also influence the field distribution inside the mold cavity. But changing the dielectric properties of the mold insert provides a specific treatment to adjust the field distribution (e.g. the local field strength) within the mold cavity which does not require significant changes in the overall setup and structure of the molding tool which can for example be particularly advantageous for prototyping, but also generally because every setup change in the underlying machine can be very time consuming and cost intensive.

[0122] One specific way of adjusting or at least influencing the field strength within the mold cavity is by means of a local variation of the dielectric constant of the material of the mold insert.

[0123] Values of the (relative) dielectric constant of materials suitable for the mold insert of the present invention, measured at 27.12 Mhz, are shown in Figure 3

[0124] - curve 310 shows the dielectric constant of a material called PerFORM having a density of 1.61 g / cm 3 over a temperature range of 20°C - 120°C. PerFORM is a ceramic composite stereolithography material.

[0125] - curve 320 shows the dielectric constant of a PET material having a density of 1.39 g / cm 3 over a temperature range of 20°C - 120°C.

[0126] - curve 330 shows the dielectric constant of a PLA (polylactic acid) material having a density of 1.24 g / cm 3 over a temperature range of 20°C

[0127] - 120°C.

[0128] - curve 340 shows the dielectric constant of a cyanate ester resin CE 221 having a density of 1.21 g / cm 3 over a temperature range of 20°C

[0129] - 90°C.

[0130] - curve 350 shows the dielectric constant of a PE material having a density of 0.93 g / cm 3 over a temperature range of 20°C - 120°C.

[0131] All of the materials investigated, except the PE material, show an increase of the dielectric constant with increasing temperature. Furthermore, for the materials shown, the dielectric constant correlates with the density of the material, i.e. a higher density means a higher dielectric constant. Alternatively or additionally, for the use of different materials (e.g. the materials discussed in the context of Figure 3 , the local variation of the dielectric constant of the mold insert of the present invention can thus at least partially be caused by a local variation of the density of the material of the mold insert. Generally (at least for the materials shown in Figure 3 ), a higher density of the material of the mold insert results in a higher dielectric constant of the mold insert. Suitable values of the local density of the material of the mold insert of the present invention are between 0.4 g / cm 3 and 1.7 g / cm 3 .

[0132] ​Alternatively, with respect to suitable values ​​of the dielectric constant, values ​​between 1 and 20 have generally proven to be advantageous for obtaining the desired influence on the field distribution within the mould cavity.

[0133] Another way to locally adjust or at least influence the field distribution (eg, local field strength) within the mold cavity is through local variation of the dielectric loss factor of the mold insert.

[0134] The values ​​of the dielectric loss factor of materials generally suitable for the mold insert of the present invention, measured at 27.12 MHz, are shown in Figure 4 (This material is the same as above Figure 3 the same material discussed in the context of

[0135] - Curve 410 shows a density of 1.61 g / cm 3 PerFORM material at 20℃

[0136] Dielectric loss factor in the temperature range of -120°C.

[0137] - Curve 420 shows a density of 1.39 g / cm 3 The dielectric loss factor of PET material in the temperature range of 20℃-120℃.

[0138] - Curve 430 shows a density of 1.24 g / cm 3 Dielectric loss factor of PLA material in the temperature range of 20℃-120℃.

[0139] - Curve 440 shows a density of 1.21 g / cm 3 The dielectric loss factor of CE 221 in the temperature range of 20℃-90℃.

[0140] - Curve 450 shows a density of 0.93 g / cm 3 The dielectric loss factor of PE material in the temperature range of 20℃-120℃.

[0141] The PerFORM, PET, and PLA materials (see curves 410, 420, and 430) show a significant increase in dielectric loss factor with temperature, while the dielectric loss factor of the CE 221 and PE materials (see curves 440 and 450) remains nearly constant.

[0142] We again point out that while the dielectric loss factor of the material of the mold insert (or variations therein) can not directly influence the field distribution (e.g. local field strength) inside the mold cavity, it can at least indirectly. A change in the dielectric loss factor of the material of the mold insert will typically change the heating experienced by the mold insert when being penetrated by the electromagnetic field. This local change in temperature in the mold insert can lead to a corresponding change in the dielectric constant of the mold insert, which is typically a temperature dependent quantity, see for example Figure 3 which in turn can influence the electromagnetic field outside the mold insert.

[0143] A further influence that a (local or global) change in the dielectric loss factor can have on the outcome of the fusion process (especially for the case where the mold insert is arranged directly adjacent to the mold cavity) is the amount of heating experienced by the mold insert when being subjected to the electromagnetic field, in particular the heat at the surface of the mold insert facing the mold cavity.

[0144] The inventors' research has shown that a certain degree of heating of the material surrounding the mold cavity is beneficial for the fusion process and that fusion without any "pre-heating" of the surface of the expanded material particles can be insufficient.

[0145] Therefore, in a preferred embodiment of the invention, a material with a (local) dielectric loss factor greater than 0.01 and less than 0.10 is used in the mold insert, in particular a material with a (local) dielectric loss factor of 0.01 to 0.07. In this regard, the PE material discussed in the context of Figure 3 and Figure 4 is less suitable than other materials and the PLA material is also less suitable at temperatures below about 90°C.

[0146] However, as already mentioned in the summary part of the present document, other values are possible as well. For example, using polyvinylidene fluoride (PVDF), also known as polyvinylidene difluoride, in the structure of the mold insert can also achieve values of 0.2 or even higher.

[0147] Further embodiments are described in the following in order to facilitate the understanding of the invention:

[0148] 1. A mold insert for use in a mold for manufacturing a cushioning element of an article of sportswear,

[0149] a. wherein the cushioning element is made from particles of an expanded material,

[0150] b. wherein an electromagnetic field is used as an energy carrier to fuse the particle surfaces,

[0151] c. wherein the mold insert has been manufactured using an additive manufacturing method, and

[0152] d.wherein the mold insert is adapted to locally adjust the field strength of the electromagnetic field within the mold cavity of the mold at least partially based on the geometry of the cushioning element.

[0153] 2. The mold insert of example 1, wherein the mold insert is adapted to increase the uniformity of the field strength throughout the mold cavity during the manufacturing of the cushioning element.

[0154] 3. The mold insert of example 1 or 2, wherein the local adjustment of the field strength within the mold cavity is at least partially caused by a local variation of the dielectric properties of the mold insert.

[0155] 4. The mold insert of example 3, wherein the local adjustment of the field strength within the mold cavity is at least partially caused by a local variation of the dielectric constant of the mold insert.

[0156] 5. The mold insert of example 4, wherein the local variation of the dielectric constant of the mold insert is at least partially caused by a local variation of the density of the material of the mold insert.

[0157] 6. The mold insert of example 5, wherein a higher density of the material of the mold insert results in a higher dielectric constant of the mold insert.

[0158] 7. The mold insert of example 5 or 6, wherein the local density of the material of the mold insert is between 0.4 g / cm 3 and 1.7 g / cm 3 .

[0159] 8. The mold insert of one of examples 3 to 7, wherein the local adjustment of the field strength within the mold cavity is at least partially caused by a local variation of the dielectric loss factor of the mold insert.

[0160] 9. The mold insert of example 8, wherein the local dielectric loss factor of the mold insert is between 0.01 and 0.10, in particular between 0.01 and 0.07.

[0161] 10. The mold insert of one of examples 1 to 9, wherein the mold insert is arranged adjacent to the mold cavity and influences the geometry of the mold cavity.

[0162] 11. The mold insert of one of examples 8 or 9 and one of example 10, wherein the local variation of the dielectric loss factor further influences the amount of surface heating of a surface of the mold insert adjacent to the mold cavity during the manufacturing of the cushioning element.

[0163] 12. The mold insert according to one of examples 1 to 11, wherein the additive manufacturing method for the mold insert comprises at least one of: 3D printing; micro-droplet based methods; powder bed based methods; stereolithography, SLA; selective laser sintering, SLS; selective laser melting, SLM; continuous liquid interface production, CLIP; fused deposition modeling, FDM; digital light processing, DLP; multi-jet modeling, MJM; multi-jet methods; film transfer imaging methods, FTI; electron beam melting, EBM; electron beam additive manufacturing, EBAM; subtractive rapid prototyping, SRP.

[0164] 13. The mold insert according to one of examples 1 to 12, wherein the mold insert comprises at least one of the following materials: ceramic filled resin; cyanate ester; polylactic acid / polylactide, PLA; acrylonitrile butadiene styrene, ABS; polyamide 6 / nylon 6, PA6; polyamide 66 / nylon 66, PA66; polyamide 12 / nylon 12, PA12; polyether ether ketone, PEEK; adhesive systems; epoxy resin; UV-cured thermoset.

[0165] 14. The mold insert according to one of examples 1 to 13, wherein the electromagnetic field provides energy to fuse the particle surfaces in the form of electromagnetic waves in the radio frequency part of the 30 kHz to 300 MHz spectrum, or in the form of electromagnetic waves in the microwave part of the 300 Mhz to 300 Ghz spectrum, in particular in the form of electromagnetic waves with a frequency in the range of 25 to 30 MHz.

[0166] 15. The mold insert according to one of examples 1 to 14, wherein the cushioning element is a sole, in particular a midsole, for a shoe.

[0167] 16. A mold for manufacturing a cushioning element of a sports garment from particles of an expanded material,

[0168] a. wherein an electromagnetic field is used as an energy carrier to fuse the particle surfaces, and

[0169] b. wherein the mold comprises a mold insert according to one of examples 1 to 15.

[0170] 17. The mold according to example 16,

[0171] c. wherein the mold comprises at least two mold parts,

[0172] d. wherein each of the two mold parts comprises an electrode for providing an electromagnetic field,

[0173] e. wherein the mold insert is placed in one of the two mold parts,

[0174] f. wherein the two mold parts can be moved relative to each other in a first direction to open the mold, thereby allowing the mold to be loaded with particles, and

[0175] g. wherein the two mold parts can be moved relative to each other in a second direction to close the mold, thereby forming a mold cavity between the electrodes.

[0176] 18. Method of manufacturing a cushioning element for sports clothing from particles of an intumescent material,

[0177] a. wherein an electromagnetic field is used as an energy carrier to fuse the particle surfaces, and

[0178] b. wherein the method uses a mold according to example 16 or 17.

[0179] 19. Cushioning element, in particular shoe sole or shoe midsole, manufactured with the method according to example 18.

[0180] 20. Shoe, in particular sports shoe, comprising a shoe sole or shoe midsole according to example 19.

Claims

1. A mold for manufacturing a cushioning element of a sports garment from particles of an expanded material, the mold comprising: a. at least two mold parts, each of the two mold parts comprising an electrode for providing an electromagnetic field, b. a mold insert manufactured using an additive manufacturing method; wherein the mold insert is placed in at least one of the two mold parts, wherein the two mold parts are movable relative to each other in a first direction to open the mold, thereby allowing the mold to be loaded with particles, wherein the two mold parts are movable relative to each other in a second direction to close the mold, thereby forming a mold cavity between the electrodes, wherein the electromagnetic field serves as an energy carrier to fuse the particle surfaces, wherein the mold insert is adapted to locally adjust the field strength of the electromagnetic field within the mold cavity of the mold based at least in part on the geometry of the cushioning element.

2. The mold of claim 1, wherein, The local adjustment of the field strength within the mold cavity is caused at least in part by a local variation of the dielectric properties of the mold insert.

3. The mold of claim 1, wherein, The mold insert at least partially defines the geometry of the mold cavity.

4. The mold of claim 3, wherein, The same overall tool consisting of the at least two mold parts can be used with different mold inserts for manufacturing a plurality of different cushioning elements.

5. The mold of claim 1, wherein, The mold has a mold insert that completely surrounds the mold cavity.

6. The mold of claim 5, wherein, The mold insert comprises a first part and a second part, which are configured to be placed into the two mold parts, respectively.

7. The mold of claim 1, wherein, The geometry of one or both of the electrodes is configured such that the resulting electromagnetic field has already been substantially adjusted for manufacturing the cushioning element, the mold insert is configured to further adjust the electromagnetic field on a more fine-grained level.

8. The mold of claim 1, wherein, The two mold parts or at least a part thereof comprise a capacitor plate as an electrode, which is arranged on the inside of the mold part.

9. The mold of claim 8, wherein, The mold part consists of a layered structure comprising a base plate, a mold plate defining at least part of the mold cavity, and an insulation layer on the inside of the mold plate.

10. The mold of claim 8 or 9, wherein, The thickness of the mold plate and / or the capacitor plate is varied.

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