METHOD FOR PRODUCING AN ELASTICLY DEFORMABLE MOLDED PART

Description

[0001] The invention relates to a method for producing an elastically deformable molded part having a number of undercut molded part regions by means of a mold.

[0002] Injection molding is often used to cost-effectively produce identical molded parts in large quantities. During injection molding, the injection molding material is liquefied and injected under pressure into an injection mold. The material then cools in the mold. The resulting molded part can then be removed from the mold. The mold cavity determines the design of the molded part.

[0003] Due to the increasing customer demand for individually configured products that are tailored precisely to their needs, one-off or custom-made products are playing an increasingly important role in production.

[0004] To date, no process is known that enables the cost-effective production of components in small quantities, especially as one-off items (batch size 1). The production costs for injection-molded components manufactured using custom-made, single-use molds (disposable molds) are very high. Therefore, the use of injection molding technology is generally uneconomical in such cases. Alternative manufacturing processes are then used, meaning that the specific advantages of injection molding, especially the achievable high precision, are not realized.

[0005] Layered construction processes serve as an alternative manufacturing method. In these additive manufacturing processes, layers of a build-up material are successively applied one on top of the other. Before the next layers are applied, the areas in the respective layers corresponding to the cross-section of the component to be manufactured are selectively solidified. One advantage of additive manufacturing is that components with very complex geometries can be easily constructed. This particularly applies to components with severe undercut areas, where demolding the undercut from a fixed shaping contour would not be possible without destroying the molded part.

[0006] A disadvantage of using additive manufacturing techniques, however, is that particularly soft materials cannot be processed, since, for technical reasons, additive manufacturing always requires a layer of material to be sufficiently hardened before a new layer can be built on top. Therefore, the processing of various plastics, such as elastomers, polyurethane foams, silicone, and the like, is not possible or only possible with limitations. Therefore, molded parts that are intended to be elastically deformable are often impossible to produce using additive manufacturing, or only with considerable effort.

[0007] DE 10 2007 007154 A1 describes a method for producing a foam part with a foam-free undercut. An elastically deformable mold is used for the undercut area. To demold the foam part, the mold is elastically deformed. The mold remains undamaged and can be used multiple times in succession to produce the same foam part.

[0008] An object of the present invention is to provide a technique that makes it possible to produce individual molded parts that are elastically deformable and have undercut areas from very soft materials with high precision and at low cost.

[0009] This object is achieved by a method according to claim 1. Advantageous embodiments of the invention are specified in the subclaims. The advantages and embodiments explained below in connection with the method according to the invention also apply mutatis mutandis to a device used to carry out the method (not part of the claimed invention), and vice versa.

[0010] The method according to the invention for producing an elastically deformable molded part having a number of undercut molded part regions by means of a mold is characterized in that molded part material is introduced into the mold, wherein the mold has a shaping contour with a number of special contour regions which are designed to shape the number of undercut molded part regions of the molded part. The molded part material has a higher elongation at break than the mold material from which the mold is made, at least in the region of the special contour regions of the shaping contour. The molded part is demolded from the mold by at least partially deforming the mold together with the molded part contained therein in such a way that the molded part is elastically deformed and the mold breaks at least partially, but in any case within the circumference of the special contour regions.

[0011] The invention proposes producing an elastic molded part, particularly made of a soft plastic material, in a brittle, non-removable mold, preferably manufactured by additive manufacturing, which has special contour areas for shaping undercut molded part regions. The mold is shattered to demold the molded part. Demolding occurs exclusively by destroying at least part of the mold; no loose parts (sliders or the like) are used.

[0012] In forced demolding, plastic parts made of a tough, elastic molded part material are deformed in the elastic range during ejection. In the case according to the invention, the produced molded parts are elastically deformable, but nevertheless cannot be forced demolded because the mold, due to the undercut areas of the molded part to be formed, has a geometry that prevents forced demolding despite the molded part's deformability.

[0013] The invention is based, among other things, on the fact that the elastic molded part located in the mold is deformable. While external triggers can cause the mold to break, the deformability of the molded part enables the mold to deform, resulting in the mold breaking. Due to its elastic deformability, the molded part located in the mold will not break either due to its deformation or due to the deformation of the mold, and will not be otherwise destroyed or damaged in a way that limits its functionality, in particular not due to deformation-induced impact with the broken mold.

[0014] Since the molded part produced is elastically deformable, so that it can be deformed during demolding, the method according to the invention differs significantly from known methods for producing non-elastically deformable molded parts, such as those commonly used for cores in the foundry industry, particularly in metal casting, and in which demolding of the molded part with undercut areas from the mold is also not possible.

[0015] The invention proposes the use of molds for producing individual molded parts and thus a manufacturing process with a batch size of 1. Each molded part can have an individually defined geometry, or at least one molded part section with an individualized contour. There are no limits to the shape of the molded part. There are no geometric restrictions for the molded part produced by the method according to the invention. In particular, even strongly undercut molded parts can be produced using the method according to the invention, whereby this is understood to mean molded parts with geometries that would not allow demolding of the undercut from a fixed shaping contour without destroying the molded part.Accordingly, a mold according to a particularly advantageous embodiment of the method is characterized in that the number of special contour areas of the shaping contour of the mold are designed in such a way as to shape the number of undercut molded part areas of the molded part, that the number of undercut molded part areas formed in this way have a geometry such that demolding of these molded part areas from the mold would not be possible without destroying the molded part, despite the elastic deformability of the molded part.

[0016] The fact that, despite deformation of the molded part and the mold, only the mold or parts thereof are destroyed, in particular break into shards (fragments), is achieved according to the invention in that the molding material has a significantly lower elongation at break than the molding material. In other words, the molding material has a higher elongation at break than the molding material from which the mold is made, at least in the area of ​​the special contour areas of the shaping contour. Thus, the molded part is less brittle, at least in the area of ​​its undercut molding areas, than the mold in the area of ​​the special contour areas.

[0017] The ratio of the elongation at break of the molding material to the elastic material of the molded part (molded part material) can be as small as desired. However, according to the invention, this ratio is at least 1:3. In other words, the elongation at break of the molding material is at least three times the elongation at break of the molding material. Preferably, the elongation at break of the molding material is at least ten times, particularly preferably at least twenty times, the elongation at break of the molding material.

[0018] The molded part material is preferably a (very) soft material from which a non-brittle, elastic molded part can be produced. By using a mold filled with the molded part material, very precise components can be manufactured from very elastic materials. In this way, material so soft that it cannot be additively processed can also be used for the molded part.

[0019] The use of plastics as the molding material is particularly advantageous, especially the use of elastomers, polyurethane foams, silicone, and the like. Multi-component molding materials can also be used. According to one embodiment of the invention, the molding material has a Shore A hardness of < 90.

[0020] Preferably, the molding material is introduced into the mold under pressure or at a pressure of < 50 bar. Filling the mold with molding material can be achieved by pouring or injection molding, for example.

[0021] According to one embodiment of the invention, inserts are used which are placed into the mold prior to the filling process and bond with the elastic molding material, thereby becoming part of the molded part. The inserts are preferably assembly elements or reinforcement elements, such as fabric. In this way, the functionality of the molded parts can be expanded. If the inserts are assembly elements or have assembly elements, molded parts intended for assembly with other components can then be more easily connected to the other components to form a finished product. In this way, it is also particularly easy to specifically influence the basic functional properties of the molded part to be produced.

[0022] According to one embodiment of the invention, a number of inserts are used to produce a multi-component molded part. Preferably, one insert, together with the soft, elastically deformable component of the molded part, consisting of the molded part material, forms the molded part. The component of the molded part formed by the insert preferably consists of an insert material that has a different hardness, in particular a significantly greater hardness, than the molded part material, and thus serves as the hard component of the molded part. In this way, with the help of suitable inserts, any desired hard-soft molded parts with different deformabilities in certain sections can be formed.

[0023] According to one embodiment of the invention, the inserts can also be special inserts that are not inserted into an already fully existing mold, but are designed in such a way that, together with an existing mold base, they form the overall mold. In other words, such inserts not only serve to influence the properties of the molded part to be produced, since they form a permanent part of the molded part after demolding, but also form a functional component of the mold. These inserts can also be filled with molding material themselves and thus serve as a mold or part of the mold.

[0024] Since, according to the invention, the molded part is not directly manufactured additively, the selection of the molded part material is not limited by its applicability for an additive manufacturing process. Since the molded part material does not have to be suitable for additive manufacturing, a proven molded part material that is optimally suited for the respective application can be used instead.

[0025] The mold material used for the production of the mold used in the process according to the invention, but at least for the special contour areas of the shaping contour, is preferably suitable for producing a crushable, preferably additively produced mold and is further preferably characterized by being so brittle that it breaks into individual shards upon deformation. Breaking into individual, unconnected shards has the advantage that these shards can be removed relatively easily after the molded part has been demolded from the mold.

[0026] The mold used in the application of the method according to the invention is completely or partially destroyed by the process of demolding the molded part, depending on whether the mold is formed in one piece or in several pieces.

[0027] With a one-piece mold, the mold cannot be reused once it has been destroyed, at least to the extent of the special contour areas. A new mold is required for each molded part. The mold is therefore a true one-time mold (lost mold).

[0028] In a multi-part mold, the shaping contour with the special contour areas is preferably formed by a partial mold of the mold, which, together with one or more other mold components, forms the mold. In this case, only the partial mold with the shaping contour provided with special contour areas is preferably destroyed, while destroying the partial molds not provided with special contour areas is not necessary. In this way, one part of the mold can be reused, while another part of the mold serves as a disposable mold and can be individually designed.

[0029] In one embodiment of the invention, the shaping contour of the mold may, in addition to the special contour areas, also comprise shaping areas which are designed to shape non-undercut molded part areas.

[0030] It has proven particularly advantageous if the mold is designed with thin walls. In this way, not only can the amount of mold material used in mold production be reduced, but the time required to produce the mold can also be reduced, particularly when using additive manufacturing technology. At the same time, a low wall thickness of the mold supports the shattering of the mold upon deformation as desired according to the invention. It is therefore particularly advantageous to design the mold as a thin-walled shell construction, at least in the area of ​​the shaping contour having the special contour areas. Depending on the mold material used, the wall thickness of the mold can be, for example, 0.5 to 1.5 mm. In order to prevent the mold from already cracking during the filling phase, iewhen the molding material is poured into the mold, in particular under increased filling pressure, the mold breaks, according to one embodiment of the invention the mold can be mechanically reinforced from the outside during the filling process, at least partially, but in any case around the circumference of the shaping contour. For this purpose, the mold can be supported on the outside with an additional support material that can preferably be easily removed later. For example, the mold can be placed in a stabilizing mass during the filling process, e.g. in a bed of sand. Such a support structure or bed is particularly advantageous for thin-walled molds. It can also protect the mold from bursting not only during the filling process, but also during any foaming phase of the molding material introduced into the mold.

[0031] According to one embodiment of the invention, it is advantageous if the mold, at least in the area of ​​the special contour regions of the shaping contour, is provided with a number of predetermined breaking points. In this way, it can be ensured that the mold, at least in the area of ​​the shaping contour, breaks into a plurality of shards upon deformation. The arrangement and course of the predetermined breaking points can also influence the size and arrangement of the resulting shards. The predetermined breaking points are thus advantageously designed such that the resulting shards can be easily removed from the undercut areas of the elastic molded part due to their size and position.

[0032] For a simple and uncomplicated production of the mold, especially when using additive manufacturing technology, it has proven advantageous if the forming

[0033] The mold material used for the contour with the special contour areas is identical to the mold material used for the remaining areas of the mold. In this way, the entire mold, or at least the part of the mold that encompasses the shaping contour with the special contour areas, is made of the same mold material from which the special contour areas are made and can be manufactured in a single operation.

[0034] According to a preferred embodiment of the invention, a region of the mold comprising the shaping contour or a partial mold of a multi-part mold comprising the shaping contour or the entire one-part mold is produced by means of an additive manufacturing process, but in any case at least that special contour region which serves to form the undercut molded part region and is later destroyed for the purpose of demolding the molded part.

[0035] The molding material used at least for the special contour areas of the shaping contour is preferably a light-curing plastic.

[0036] The preferred additive manufacturing processes are UV-curing processes, such as digital light processing (DLP), UV LCD, stereolithography (SLA), and the like. The use of such processes for mold production is advantageous, among other things, because they allow for the creation of very smooth surfaces and the creation of fine details, such as logos and text.

[0037] In addition to the special contour areas, the mold or partial mold can also have contour areas with shaped contours that serve to shape areas of the elastic molded part that are not subject to significant undercuts. These additional contour areas can then also be manufactured conventionally without the use of additive manufacturing processes.

[0038] The shaping contour with the special contour areas can also be combined with other sub-shapes and assembled into an overall mold, regardless of their manufacturing method (additive or non-additive). These other sub-shapes can also have been manufactured in advance and / or using other processes, e.g., non-additive manufacturing, as well as using different mold materials. These other sub-shapes can advantageously have different material properties, so that, in particular, a different deformation behavior can be achieved. In this way, it is easy to specifically permit or prevent breakage of defined areas of the mold.

[0039] According to one embodiment of the invention, a multi-part mold can also be produced by forming the mold at least partially by special inserts which partially form the mold or form a component of the mold, as described above.

[0040] Following the solidification of the soft molding material in the mold, creating the desired molded part, demolding takes place. Demolding occurs through deformation of the mold and the molded part contained therein. Due to this deformation, the shape-giving contour of the brittle mold, at least in the special contour areas, is destroyed by mechanical breakage or shattering. If the fracture strength of the molding material is exceeded, separation or brittle fractures typically occur. However, the mold can also break due to deformation or ductile fractures.

[0041] According to the invention, the mold is deformed. Along with the mold, the molded part still in the mold is also deformed. Advantageously, the mold is deformed by applying external pressure to the mold. The pressure can be applied either directly by mechanical application or indirectly by pneumatic or hydraulic application via a medium to the outside of the mold. If a support structure or bedding is used, the pressure is preferably applied while the mold is still being mechanically reinforced from the outside.

[0042] Crushing the mold, together with the molded part contained therein, between rollers or in a mangle has proven particularly advantageous for shattering the molding contour. The device for carrying out the method according to the invention comprises suitable means for applying pressure for this purpose (not part of the claimed invention).

[0043] By crushing the mold, at least within the special contour areas of the molding contour, all fragments of the molding contour can be removed from the undercut areas of the molded part. Depending on the geometry of the elastic molded part, this can be done immediately during crushing or in a subsequent step.

[0044] The removal of the fragments can advantageously be assisted by shaking, rocking, turning or by flushing with air or liquid.

[0045] In one embodiment of the invention, in which not only crushable but also soluble molding material is used, the fragments can be dissolved after the mold has been destroyed. This eliminates the potentially laborious removal of small and tiny fragments. For this purpose, the molding material is selected so that it is soluble in a solvent.

[0046] However, for environmental reasons, the removal of the fragments is preferably carried out purely mechanically. This allows the fragments to be disposed of easily and inexpensively or, at least in part, to be recycled into molding material.

[0047] According to an advantageous embodiment of the invention, the mold is provided with a suitable release agent before filling the mold. In this way, early detachment of the mold fragments from the elastic molded part can be achieved. The fragments are then no longer supported by the molded part and can be more easily broken into smaller pieces. Depending on the materials used, a silicone-containing agent, for example, can be used as the release agent. If a release agent is used, demolding of the molded part or removal of the fragments is preferably followed by a cleaning step in which the resulting elastic molded part is cleaned of any residues of the release agent using a suitable solvent.

[0048] According to a further advantageous embodiment of the invention, the mold is embrittled in a suitable manner before filling it with the molding material or, alternatively, before demolding. This can be achieved, for example, by intensive irradiation with UV light or by subjecting the mold to intensive drying. The mold can also be exposed to an atmosphere that chemically embrittles the molding material.

[0049] The invention provides a technique that makes it possible to produce individual, elastically deformable molded parts having undercut areas with high precision from very soft materials in a simple and comparatively cost-effective manner.

[0050] The invention encompasses the described method for producing an elastically deformable molded part having a number of undercut molded part regions using a mold. The device designed to carry out this method and comprising all means and devices designed to carry out the described method steps is not part of the claimed invention.

[0051] The invention also encompasses the individual elastic molded part produced by such a method. At the same time, the invention thus also relates to the use of an elastically deformable molded part produced by the method according to the invention as part of an article or to any article comprising an elastically deformable molded part produced by this method. A molded part produced by the method according to the invention can advantageously be used for the purpose of individualizing an article, in particular in orthopedic technology or in the manufacture of individual products for performance improvement, e.g. work equipment or sports equipment. Such a molded part according to the invention can be used in particular as part of a shoe, in particular as a shoe sole or as part of a shoe sole.

[0052] The invention also encompasses a method for producing a mold or partial mold described in connection with the method according to the invention and usable with this method, having a shaping contour, in particular by means of additive manufacturing, as well as the use of such a mold or partial mold for the method according to the invention. The invention also encompasses a material suitable for use as a molding material for producing the shaping contour of the mold or partial mold, as well as the use of such a material for producing a crushable, in particular additively manufactured, shaping contour of a mold or partial mold for use in the method according to the invention.

[0053] An embodiment of the invention is explained in more detail below with reference to the drawings. Fig. 1 a schematic sectional view of an empty mold, Fig. 2 a schematic sectional view of a mold filled with molding material, Fig. 3 a schematic sectional view of a partially broken mold, Fig. 4 a schematic sectional view of a molded part.

[0054] All figures depict the invention not to scale, but merely schematically and with only its essential components. Like reference numerals correspond to elements with the same or comparable function.

[0055] With the described method, an elastically deformable molded part 1 is produced by means of a mold 2. The finished molded part 1 has a number of strongly undercut molded part areas 3, see Fig. 4 .

[0056] Form 2 includes a fixed, ie . non-elastically deformable, shaping contour 4 with a number of special contour areas 5, as in Fig. 1 illustrated. The special contour areas 5 are designed to shape the number of undercut molded part areas 3 of the molded part 1. The thin-walled mold 2 is, at least in the circumference of the special contour areas 5 , Made of a brittle, breakable material. Mold 2 is produced using additive manufacturing. The mold material is a light-curing plastic.

[0057] First, as in Fig. 1 indicated by the arrow, the molding material is introduced into the mold. Mold 2 is filled without pressure or under low pressure. Nevertheless, the mold 2 is heated from the outside by a Fig. 1 The indicated bedding 6 is mechanically reinforced with sand. The molded part material is a relatively soft plastic, such as PU foam. The ratio of the elongation at break of the molding material to the molded part material is at least 1:3. .

[0058] After the soft molded part material has solidified in the mold 2, the molded part 1 is removed from the mold 2. For this purpose, the mold 2 together with the molded part 1 contained therein is at least partially deformed in such a way that the molded part 1 deforms elastically without damage and the mold 2 at least partially, but in any case within the scope of the special contour areas 5 , into shards (fragments) 7. In the area of ​​the special contour areas 5, the shaping contour 4 of the mold 2 is provided with predetermined breaking points 8, as in Fig. 2 The partially broken form 2 is shown in Fig. 3 To achieve the desired deformation, the mold 2, and thus also the molded part 1 contained within the mold 2, is subjected to pressure, caused by the direct impact of rotating rollers (not shown) on the mold 2. The breakage of the mold 2 in the area of ​​the special contour areas 5 is caused by the deformation of the mold 2 during the pressure application and can also occur due to the deformation of the elastic molded part 1.

[0059] Finally, the fragments 7 are removed, for example by simply shaking, rattling and / or turning the molded part 1. Fig. 4 shows the finished molded part 1 .

[0060] All features presented in the description, the following claims and the drawings may be essential to the invention both individually and in any combination with one another.

[0061] These features or combinations of features may each constitute an independent invention, the use of which is expressly reserved.

[0062] When specifying a combination of features defining an invention, individual features from the description of an embodiment need not necessarily be combined with one or more or all other features specified in the description of that embodiment; in this respect, each sub-combination of features of one or more embodiments is expressly disclosed. List of reference symbols

[0063] 1Molded part 2Mold 3Undercut molded part area 4Shaping contour 5Special contour area 6Bedding 7Shards 8Predetermined breaking points

Claims

1. Method for producing an elastically deformable molded part (1) having a number of undercut molded part regions (3) by means of a mold (2), in which molded part material is introduced into the mold (2), the mold (2) having a shaping contour (4) with a number of special contour regions (5) designed to shape the undercut molded part regions (3) of the molded part (1), characterized in that - the molded part material has a higher elongation at break than the mold material from which the mold (2) is made, at least in the region of the special contour regions (5) of the shaping contour (4), and - the molded part (1) is demolded from the mold (2) by at least partially deforming the mold (2) together with the molded part (1) contained therein, such that the molded part (1) is elastically deformed and the mold (2) breaks at least in the region of the special contour regions (5).

2. Method according to claim 1, in which the special contour regions (5) are designed to shape the undercut molded part regions (3) such that these undercut molded part regions (3) have a geometry making demolding from the mold (2) impossible without destroying the molded part (1).

3. Method according to claim 1 or 2, in which the elongation at break of the molded part material is at least three times, preferably at least ten times, particularly preferably at least twenty times that of the mold material.

4. Method according to any one of claims 1 to 3, in which the molded part material is a plastic.

5. Method according to claim 4, in which the molded part material has a Shore hardness A < 90.

6. Method according to claim 4 or 5, in which the molded part material is introduced into the mold (2) without pressure or at a pressure < 50 bar.

7. Method according to any one of claims 1 to 6, in which the mold material, at least in the region of the special contour regions (5), is characterized by breaking into shards (7), particularly individual shards, through deformation.

8. Method according to any one of claims 1 to 7, in which the mold (2) is designed in multiple parts, and during demolding, only the mold part containing the shaping contour (4) with the special contour regions (5) breaks as a result of the deformation of the mold (2) and the molded part (1).

9. Method according to any one of claims 1 to 8, in which the mold (2) is provided with predetermined breaking points (8) at least in the region of the special contour regions (5) of the shaping contour (4).

10. Method according to any one of claims 1 to 9, in which the mold (2) is produced by additive manufacturing at least in the region of the special contour regions (5) of the shaping contour (4).

11. Method according to claim 10, in which the mold material is a light-curing plastic at least in the region of the special contour regions (5) of the shaping contour (4).

12. Method according to any one of claims 1 to 11, in which the shaping contour (4) is destroyed by mechanical fracturing at least in the region of the special contour regions (5) during deformation of the mold (2) and the molded part (1) contained therein.

13. Method according to claim 12, in which the mold (2) is deformed by applying pressure.