3-D printed master model

Abstract

This disclosure concerns a master model for the production of a mold, comprising: (a) a first part, a second part comprising a textured surface; wherein the first part and the second part are connected.

Claims

1. A method for producing a modular master model for the production of a mold for an article of footwear, the method comprising: forming a first part representing one portion of a shoe outsole; forming a second part representing another portion of a shoe outsole and including a textured surface; and connecting the first part and the second part by separably fitting the second part into one of a plurality of recesses defined in the first part so as to form the master model, wherein the first part and the second part are formed by additive manufacturing, and wherein another of the plurality of recesses of the first part is configured to be separably fit with a third part including a textured surface as part of the master model.

2. The method according to claim 1, wherein the master model is formed as a positive model of a portion of an article of footwear.

3. The method according to claim 1, wherein the first part and/or the second part is made from a resin or polymer material.

4. The method according to claim 1, wherein forming the first part and/or the second part of the master model comprises activating a liquid photopolymer such that the liquid photopolymer solidifies.

5. The method according to claim 1, wherein forming the first part and/or forming the second part further comprises: forming a temporary support structure connected to and configured to support the respective first and/or second part; and removing the temporary support structure after the respective first and/or second part has been formed.

6. The method according to claim 1, wherein forming the first part comprises forming a texture on the surface of the first part.

7. The method according to claim 6, wherein the texture of the first part and/or the second part comprises at least one resolved feature of linear size of 0.2 mm or smaller.

8. A method for producing a mold for an article of footwear, the method comprising: producing a master model according to the method of claim 7; and forming the mold based on the master model.

9. The method according to claim 8, further comprising: forming a second model based on the master model; and forming, from a heat-resistant material, a third model based on the second model, wherein the mold is formed based on the third model.

10. The method according to claim 8, wherein the mold is a first mold, and wherein the method further comprises: exchanging the second part for a variation the second part having a textured surface differing from the textured surface of the second part so as to form a variation of the master model, the exchanging taking place by removing the second part from the one recess and separably fitting the variation of the second part into the one recess; and forming a second mold based on the variation of the master model.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) In the following, exemplary embodiments of the invention are described with reference to the figures. The figures show:

(2) FIG. 1A-C: An exemplary master model according to the present invention;

(3) FIG. 2: Some exemplary textures for the master model according to the present invention;

(4) FIG. 3: An exemplary schematic of a method of forming a textured mold as known in the art;

(5) FIG. 4: An exemplary schematic of a method of forming a mold according to the present invention;

(6) FIG. 5A-D: An exemplary method of forming part of a master model according to the present invention;

(7) FIGS. 6A-G: An exemplary method of forming a mold according to the present invention; and

(8) FIGS. 7A-C: An exemplary master model (FIG. 7A), an exemplary mold (FIG. 7B), and an exemplary sole element (FIG. 7C) according to the present invention.

DETAILED DESCRIPTION

(9) In the following some embodiments of the invention are described in detail. It is to be understood that these embodiments can be modified in a number of ways and combined with each other whenever compatible and that certain features may be omitted in so far as they appear dispensable. While the invention is described primarily with reference to producing a mold for a sole element for an article of footwear, it is to be understood that the master model may be a positive or negative model which can be used to produce any mold and any molded component that requires a textured surface. For example, the master model may alternatively be used for the production of a mold for forming textured handles for bicycle handlebars, handles for sports rackets, golf clubs, balls, gloves, etc.

(10) FIG. 1A shows an exemplary first part 12 according to the invention. FIG. 1B shows exemplary second parts 13a-13e configured to fit in the corresponding recesses 14a-14e, respectively, formed in the first part 12. The exemplary second parts 13a-13e all comprise a texture. It is to be understood that a master model according to the invention may comprise only a single second part. As shown in FIG. 1B, the texture pattern on the second part 13a is different to the texture pattern on the second parts 13b-13e. By using a different texture on the second part 13a to the texture on the second parts 13b-13e, it is possible to achieve an ideal level of grip for different parts of the molded component. Generally, the term “texture” or “textured surface” within the context of the present invention applies to any modulation of the height of a surface.

(11) FIG. 1C shows an exemplary embodiment of a master model 11 for the production of a mold, comprising: (a) a first part 12 and (b) second parts 13a-13e each comprising a textured surface; wherein the first part 12 and the second parts 13a-13e are connected. Note that in the exemplary embodiment of FIG. 1C, one vacancy 15 for attaching another second part (not shown) is shown for illustration purposes.

(12) The first part 12 and the second parts 13a-13e comprising a textured surface are preferably produced by additive manufacturing. Additive manufacturing is taken to have its conventional meaning. That is, additive manufacturing is any technique which applies an additive shaping principle and thereby builds physical 3D geometries by successive addition of material. Additive manufacturing comprises 3D printing and rapid prototyping. In particular, additive manufacturing comprises techniques such as laser sintering, direct metal laser sintering, selective laser melting, fused deposition modelling (FDM®), fused filament fabrication, and stereolithography. Any additive manufacturing method is suitable for the present invention.

(13) An advantage of producing the first part 12 and the second parts 13a-13e of the master model 11 by additive manufacturing is that the number of process steps required during production can be reduced compared to the conventional way of producing a mold with a textured surface. This is further described with reference to FIGS. 3 and 4.

(14) An advantage of the present invention is that a mold comprising a textured surface can be produced based on the master model 11 without chemical etching or laser texturing. This is because the master model 11 itself comprises the second parts 13a-13e comprising a textured surface. For example, the mold could be cast directly or indirectly based on the master model 11. Casting is a quick, cost-effective, and reproducible method that allows the production of large numbers of molds while retaining a high resolution of the texture. Resolution in the present context refers to the smallest size with which features can be formed deliberately and reproducibly.

(15) Another advantage of producing the first part 12 and the second parts 13a-13e of the master model 11 by additive manufacturing is that additive manufacturing is an efficient method for forming a texture comprising an outward extension from the surface as well as a texture comprising a recess in the surface. Conventional manufacturing techniques, such as milling, laser texturing, or chemical etching, are effective only for textures forming a recess on the surface, which are performed by removing materials from the surface of a molded component. Therefore, in conventional manufacturing techniques large amounts of waste are generated when a texture is formed that comprises an outward extension from the surface. Though it would be possible to form a negative model comprising a grove first and then cast a positive model on that basis, this would lead to an additional process step and restrict the suitable choice of materials.

(16) Furthermore, the resolution of the texture of a mold based on the master model 11 of the present invention is better than for a metallic mold produced directly by additive manufacturing. A better resolution of the texture allows for a greater variety of textures to be formed and, in general, therefore an improved level of grip.

(17) Another advantage of the present invention is the increased flexibility of producing a mold. Due to the modular nature of the master model 11, a first mold with a first type of texture and a second mold with a second type of texture could, in general, be produced by designing only a single first part 12 of the master model 11 and by designing two or more varieties of the second parts 13a-13e of the master model 11. This way, the development process becomes more efficient.

(18) In this exemplary embodiment, the mold is for the production of an article of footwear and the master model 11 is as a positive model of a portion of an article of footwear. The present invention is particularly suitable for forming a mold for the production of an article of footwear. This is because in a typical production environment for footwear, very large amounts of textured components need to be produced quickly and reproducibly. One master model 11 according to the present invention could be used to manufacture several molds which can then be used in parallel to produce a portion of the article of footwear by casting. If the master model 11 is a positive model of a portion of the article of footwear, it is possible to directly cast, within a single step, a mold that is a negative model of a portion of the article of footwear.

(19) The first part 12 of the master model 11 is preferably formed such that the first part 12 substantially defines the rim of an entire sole element of the article of footwear. By “substantially define” it is meant in the present context that the shape of the rim of the sole element of the article of footwear is determined by the shape of the first part 12 of the master model 11 within manufacturing imperfections. The sole element is preferably an entire outsole of footwear but it may be only a portion of an outsole. The combination of the single first part 12 with different second parts 13a-13e with different textures therefore advantageously allows several articles of footwear to be constructed that are similar in size and shape but that require a different texture, for example a running shoe for soft ground and a running shoe for hard ground.

(20) The first part 12 and/or the second parts 13a-13e are preferably made from a resin or polymer material. A first part 12 and/or second parts 13a-13e made from resin or polymer material are simple to construct with a high-resolution texture. Furthermore, a resin or polymer material allows sufficient strength and water resistance.

(21) Forming the master model 11 may comprise activating a liquid photopolymer such that the liquid photopolymer solidifies. This is described in more detail with reference to FIG. 5.

(22) The first part 12 and the second parts 13a-13e are preferably made from the same material. By using the same material for the first part 12 and the second parts 13a-13e, it is possible to produce the first part 12 and the second parts 13a-13e simultaneously by additive manufacturing methods.

(23) In the exemplary master model 11 of FIG. 1C, the first part 12 and the second parts 13a-13e are separably connected. Here, each second part 13a,13b,13c,13d,13e is attached to a corresponding receiving portion 14a,14b,14c,14d,14e, respectively, in the first part 12. Some receiving portions 14b,14c,14d,14e comprise a shallow cavity. A thin layer of adhesive is used to connect the second parts 13a-13e to the first part 12 strongly enough to allow further processing to produce the mold, while still allowing the first part 12 and the second parts 13a-13e to be separated upon application of a sufficient amount of force without damaging the first part 12 or the second parts 13a-13e. Alternatively, a deeper cavity could be used and the corresponding second part 13 is manufactured slightly oversize in order to precisely fit into the cavity. If the second part 13 is then inserted into the cavity in the first part 12, the second part 13 is held in the cavity by the tension generated from squeezing the second part 13 into the cavity in the first part 12.

(24) If the first part 12 and the second parts 13a-13e are separably connected, the modularity of the process is increased advantageously. A single first part 12 could be produced and used in combination with a second part 13 comprising a first type of texture to produce a first mold with a first type of texture. The same first part 12 could be used in combination with the second part 13 comprising a second type of texture to produce a second mold with a second type of texture, wherein the shape of the second mold could be substantially similar to the shape of the first mold. “Substantially similar” in the present context means similar but with the exception of the texture due to the second part and manufacturing imperfections. Furthermore, since the greatest wear and tear is expected for the texture, it is possible to simply replace a second part 13 on which the texture has deteriorated due to wear and tear while leaving the first part 12 in place. Likewise, should the first part 12 be damaged, for any reason, but the second part 13 is still intact, only the first part 12 needs to be replaced. This way, waste and the costs associated therewith can be reduced, resulting in a more favorable environmental impact.

(25) The exemplary first part 12 of FIG. 1 optionally can also have deep grooves on its surface in order to improve the surface traction in those portions where no second part 13 is attached.

(26) In the exemplary embodiment of FIG. 1, forming the texture on the surface of the second part 13a comprises forming at least one resolved feature F2 of linear size of 0.2 mm or smaller. The inventors have found that a feature size of 0.2 mm or smaller significantly improves the amount of grip offered by the surface of the molded component for some applications, for example for a shoe sole on a hard surface. In the exemplary embodiment of FIG. 1, forming the texture on the surface of the second parts 13b-13e comprises forming at least one resolved feature F1 of linear size of 0.1 mm or smaller leading to an even better grip in portions where this is required. The linear size can be measured along any linear direction on the surface of the first or second part, respectively.

(27) The features F1 and F2 of the textured surfaces of the second parts 13a-13e comprise a depth (in case of F1) or height (in case of F2) of between 0.01 mm and 1 mm. The inventors have found that a shallow texture, corresponding to a lower depth or height of the feature, may provide better grip on hard ground such as artificial turf, tarmac, etc.

(28) In the exemplary embodiment of FIG. 1, the second parts 13a-13e are formed to be substantially smaller than the first part 12. This is advantageous for the stability of the master model as it allows the first part 12 to essentially define the shape of the mold and, consequently, the molded component while the second parts 13a-13e define primarily the texture or part of the texture of the mold and, consequently, the molded component.

(29) FIG. 2 shows several exemplary texture patterns 21a-21j that may be formed directly by additive manufacturing on the surface of a first part and/or a second part. The optimal texture pattern is then chosen depending on the application. For example, for portions of a molded component that are expected to experience heavy wear during usage, a coarser pattern may be selected in order to reduce the wear and tear of the molded component. On the other hand in regions that experience less heavy wear during usage but that may require a high level of grip, a finer texture pattern may be selected. In addition to the size of the features, the shape of the features is another important criterion. For example, sharp features produce a better grip than rounded features. Another important criterion is the depth of the features. In the present invention, there is no fundamental limitation to the depth of the texture that can be formed, other than by the size of the additive manufacturing machine. Generally, a deeper texture leads to better grip, especially on soft ground, and greater wear resistance of the molded component.

(30) FIG. 3 shows a method for producing a textured mold by chemical etching as known in the art. In a first step 31a a computer model of the mold is created by computer aided design (CAD). In a second step 31b, a set of instructions for computer aided machining (CAM) is produced based on the CAD model. In a third step 31c, computer numerical control (CNC) machining to produce a model for the mold is performed based on the CAM model. Typically, a model is carved out of wood by CNC machining. In a fourth step 31d, the model is finished manually by a qualified worker. In the fifth step 31e, the actual mold is formed by casting in which molten metal is filled into the model and cooled in order for it to solidify. In a sixth step 31f, the CAD model of the model is adjusted based on the casted mold. This is necessary because the model received some manual finishing. In a seventh step 31g, the mold is assembled. In an eight step 31h, trials are performed to check the performance of the un-textured mold. In a ninth step 31i, chemical texturing is performed on the untextured mold. Chemical texturing comprises: selecting a desired texture, preparing a silk screen plate, silkscreen printing the texture on cotton paper, drying the cotton paper, mapping the cotton paper onto the mold, pressing the mold to a stable texture, manually applying protective ink onto the mold, dipping the mold into a chemical tank and washing the mold before the textured mold is completed. After chemical texturing is completed, surface treatment is performed in a tenth step 31j.

(31) Chemical texture etching is a highly manual process that requires a lot of time and produces large amounts of chemical waste because of the acid required to perform the etching.

(32) FIG. 4 shows an exemplary method for producing the textured mold according to the present invention. At a high level and greatly simplified, the chemical etching process that is used to texture a mold as known in the art is replaced by a digital texturing process that is free of the toxic chemicals and acids required during conventional chemical etching.

(33) In a first step 41a, a digital model of the master model is created using computer aided design (CAD). One or more texture patterns are then selected from a digital texture library. The digital texture is wrapped into the CAD model and then directly used in the second step 41b, to produce the master model including the texture on the second part or the first part and the second part. The master model is produced by additive manufacturing which is also referred to as 3D printing here. In a third step 41c, the mold is cast based on the model created in the second step 41b. The mold may be cast directly from the model, or the mold may be cast indirectly from the model through intermediate models as illustrated in FIG. 6. The mold can have separate parts which can be casted all together or separately at different steps. In a fourth step 41d, the casted mold is adjusted, or reverse engineered, in order to improve the quality of the mold and confirm that the separate parts of the mold fit well to each other. In a fifth step 41e, the mold is assembled. In other words, the separate parts of the mold are assembled together into a complete mold set which is to be used cooperatively to produce a molded component. For example, the mold can have an upper part and a lower part which form a mold cavity in between. The two parts of the mold are then used and fit together to produce a mold component. Trials of the mold are then performed in a sixth step 41f In a seventh step 41g, the surface of the mold is treated, for example to prevent damage to the surface of the mold, to make it corrosion-resistant, and/or to give it a nonstick finish.

(34) The present invention allows the lead time, that is the production time for producing a textured mold to be reduced significantly compared to the techniques known in the art and illustrated in FIG. 3. Though some manual finishing of the 3D printed model may be required, 3D printing is far more precise and reproducible than existing CNC techniques. Therefore, the amount of manual finishing required is greatly reduced in the present invention. Moreover, the 3D printing process itself is much faster than the combination of CAM and CNC as known in the art.

(35) FIG. 5 shows an exemplary method for producing a first part according to the present invention. In this example, the first part is for a master model for a mold for producing an outsole for an article of footwear. While the illustration only shows the production of a first part, it is to be understood that the production of the second part would be similar. In particular, a texture can be formed on the first part and the second part in the step shown in FIG. 5A.

(36) As shown in FIG. 5A, in a first step, a first part 12a is produced by additive manufacturing. In this example, the first part 12a is formed to have a textured surface. In this example, the first part 12a is produced by stereolithography inside a stereolithography machine 51. However, any additive manufacturing method is suitable. The first part 12a is formed immersed in a liquid photopolymer 53. While the boundary of the liquid photopolymer is shown curved for illustration purposes, the liquid photopolymer 53 preferably has a flat and sharp upper boundary. A light, for example a UV laser, is used to selectively activate the photopolymer 53, causing the photopolymer 53 to solidify in those locations where it is activated by the light. The light may be projected onto a single point, or several points simultaneously. For example, a single laser head may be used, or a double laser head may be used. It is also possible to simultaneously project the light onto many points, for example by controlling an array of mirrors, which allows the production speed to be increased. Once one layer is completed, the first part 12a is lowered, in this example by an elevator mechanism 52, and covered by an additional layer of liquid photopolymer for example by a blade (not shown). The process is then repeated on a layer by layer basis. Layers may range in thickness between 0.05 and 0.25 mm. The molding precision can be 0.1 mm or better. As an example, a suitable photopolymer is DSM Somos® Imagine 8000, which is a low-viscosity liquid photopolymer that produces water resistance, durable and accurate three-dimensional parts. The critical exposure required to activate DSM Somos® Imagine 8000 is about 13 millijoule per square centimetre. However, many types of photopolymer are suitable for the present invention.

(37) FIG. 5B shows the first part 12b, immediately after 3D printing. In order to improve the quality of the printed first part 12, the first part 12b contains a temporary support structure 54 that, in this example, was formed directly during the printing from the same material as the first part 12b. By using the temporary support structure 54, the stability of the first part 12a is improved during the 3D printing and therefore printing mistakes are less common. Furthermore, the temporary support structure 54 allows geometries and structures to be formed than would otherwise be difficult or impossible to form. FIG. 5C shows an exemplary method 57 of removing the temporary support structure 54. In this exemplary method 57, a combination of chemical and mechanical means are used to remove the temporary support structure. A cleaning solution 56 and a brush 55 are used to remove the temporary support structure from the first part 12b.

(38) FIG. 5D shows a completed first part 12c from which the temporary support structure 54 has been removed. The first part 12c is ready for the next production step in which a second part (not shown) is attached to the first part in order to produce a master model according to the invention.

(39) FIG. 6 shows several exemplary steps of a method of producing a mold according to the present invention. FIG. 6A shows a first part 12 produced, for example, as described with reference to FIG. 5. In this example, the first part 12 is for a master model for a mold for producing an outsole for an article of footwear. The first part 12 shown in FIG. 6A comprises two parts: 12a corresponding to the left outsole and 12b corresponding to the right outsole. A second part (not shown) is attached to the recesses 14 in the first part 12 by any suitable means. For example, a second part may be attached to the first part 12 by means of an adhesive.

(40) In the next step, shown in FIG. 6B a second model 61 is made from silicone. The silicone model 61 in the making comprises a left side 61a and a right side 61b which will correspond to the left outsole and the right outsole, respectively. As the first part 12 is a positive model of the outsole, the silicone mold 61 is a negative model, that is a cavity model, of the outsole to be formed.

(41) FIG. 6C shows the finished silicone model 62 comprising a left side portion 62a and a right side portion 62b. The texture in the silicone model 62 formed by the texture on the master model is clearly visible.

(42) In the next step, illustrated in FIG. 6D, a third model 64 (shown in FIG. 6E) is made from a heat-resistant material 63. For example, the heat-resistant material could be a ceramic material.

(43) The resulting third model 64 is shown in FIG. 6E as the silicone model 62 is being removed. The method of forming the third model 64 may comprise heating the ceramic in order to consolidate its structure. The third model 64 comprises a left side portion 64a and a right side portion 64b.

(44) FIG. 6F shows the third model 64 after the silicone model has been removed.

(45) In the next step, the mold is formed by casting molten metal using the heat-resistant third model of FIGS. 6E and 6F. The metal is then cooled and allowed to solidify. FIG. 6G shows the resulting mold 65 which comprises a left side portion 65a and a right side portion 65b. The mold 65 is robust and may be used to produce large numbers of outsoles without damage or with reduced wear and tear on the texture formed in the mold 65.

(46) The method shown in FIG. 6 to produce a mold 65 is advantageous especially on maintenance and protection of the master model according to the present invention. In this case, the master model can be made from 3D printing using materials such as acrylonitrile butadiene styrene (ABS), polyethylene (PE), polyamide (PA), or any polymer material. An intermediate ceramic casting core, which can be regarded as a negative model, is then made based on the master model and used to produce the final metal mold. In this case, it is more flexible on the choice of the material to make the master model, since the master model does not need to be subjected to a high temperature manufacture process.

(47) FIG. 7 shows an exemplary method of forming an outsole 72 using a master model 11 according to the present invention. FIG. 7A shows a master model 11 comprising a first part 12 and two sets of second parts 13a, 13b, 13c for a left outsole and 13d, 13e, 13f for a right outsole; all of the second parts comprising a textured surface. The first part 12 and the second parts 13a-13f are connected by any suitable means, for example by means of an adhesive or a recess formed in the first part 12 configured to fit the second parts 13a-13f Note that in this example, there is a single first part 12 for the production of two separate outsoles (left and right side).

(48) The textured surfaces of the second parts 13a-13f comprise features with a depth of between 1 mm and 5 mm. The inventors have found that the deeper (or higher) the feature, compared to the surrounding surface, the better the grip offered by the molded component on soft ground, such as grass, mud, etc. and the greater the durability of the texture.

(49) FIG. 7B shows an exemplary mold 71 formed based on the master model 11 by a method described herein. Note that the mold 71 is a single piece even though two separate outsoles are to be produced with the mold 71. The mold 71 comprises a left-side portion 71b and a right-side portion 71a, each comprising a textured surface. The mold 71 may be made from metal.

(50) FIG. 7C shows an exemplary left outsole 72b and an exemplary right outsole 72a formed based on the master model 11 and a manufacturing method according to the present invention. The outsole 72 comprises a textured surface.

REFERENCE NUMERALS

(51) 11: Master model 12, 12a-12c: First part 13, 13a-13f: Second part 14, 14a-14e: Receiving portion 15: Vacancy 21, 21a-21j: Texture pattern 31a-31j, 41a-41g: Process steps 51: Stereolithography machine 52: Elevator mechanism 53: Liquid photopolymer 54: Temporary support structure 55: Brush 56: Cleaning solution 57: Method of removing temporary support structure 61, 61a, 61b; Silicone model in the making 62, 62a, 62b: Silicone model 63: Ceramic material 64, 64a, 64b: Ceramic model 65, 65a, 65b: Mold 71, 71a, 71b: Mold 72, 72a, 72b: Outsole