Method for producing a molded body composite

Abstract

The invention relates to a method for producing a molded body composite, comprising at least the steps of: a) providing at least one inductively heatable molded body and one thermoplastic molded body; b) fixing the inductively heatable molded body and the thermoplastic molded body to each other by means of a first joining force; c) heating the inductively heatable molded body at least in the joining region; and d) joining the molded bodies by applying at least one second joining force.

Description

[0001] Process for producing a molded composite

[0002] The invention relates to a method for producing a molded composite.

[0003] Molded body composites made of metal and plastic have a wide range of applications. If the joint is to be strong and media-tight, the molded bodies to be joined are screwed or clamped together, with an additional seal placed between the two joining partners or molded bodies. A challenge with screwed connections is a drop in preload due to the settling or creep behavior of the joining partners. In addition to the screws, a seal is also required as an additional material for the connection.

[0004] Good, media-tight molded body composites made of metal and plastic are created using an adhesive bonding process. This involves cleaning, roughening, or activating both the joining partners and the molded bodies in the area of ​​the joint. After the adhesive is applied, the joining partners and the molded bodies are fixed in the desired position and remain there until the adhesive has cured. A challenge with such bonding processes is the complex pretreatment of the surfaces, which must take place immediately before the bonding process. The joining partners and the molded bodies must also be quickly and sufficiently secured to one another after the adhesive has been applied. The curing time can then be several minutes before the resulting molded body composite can be transported, loaded, or packaged. Such processes are lengthy and difficult to automate. Such bonded molded body composites are sometimes cured in an oven.Depending on the type of adhesive, viscosity changes occur during heating before final curing, so that the previously positioned joining partners or molded bodies may lose their alignment with each other and additional effort is required to fix the joining partners or molded bodies to each other.

[0005] Metal-plastic composites can also be produced by injecting a metal molded body into a plastic. However, many applications cannot be covered by this joining process, such as sealing metal housings with plastic lids or covering cooling channels.

[0006] Furthermore, processes for producing molded body composites made of metal and plastic are known, in which the joining partners or molded bodies are joined together by means of local heat input.

[0007] EP 3 433 078 B1 discloses a device and a method for producing a material-to-material or material-to-material and form-fitting connection, or for separating such a connection. A metallic or ceramic joining partner or molded body is joined or separated from a joining partner or molded body made of thermoplastic polymer by heating the metallic or ceramic element above the softening temperature of the polymer using resistance heating, laser irradiation, and / or induction. The polymer melts and, after cooling, adheres to the metal or ceramic. A typical application for this joining process is the production of point-like connections between metal and plastic. For example, aluminum electronics housings can also be closed with a plastic cover, thus replacing screws and seals. A characteristic feature of this process is the creation of a flat joining area.Furthermore, the state of the art does not explain how the connection point should be designed to create a high-quality and media-tight connection.

[0008] Molded body composites made of metal and plastic can also be rotationally symmetrical. For example, plastic pipes are connected with metal connectors to build load-bearing structures or transport fluids. Generally, the rotationally symmetrical elements are fixed to each other and then pressed together using sleeves, clamps, or similar devices. Alternatively to mechanical fixation, an adhesive can also be applied, which then bonds the metal and plastic. If the plastic joining partner is a thermoplastic, hot air or ultrasound can be used to create the composite.

[0009] WO 2008 / 028224 A1 discloses a method for joining two components, where at least one component is a plastic composite material. For joining, a thermoplastic film can be inserted between the two components and the joint heated.

[0010] Another application for molded body composites made of metal and plastic is sensor manufacturing. Many sensors used to measure distance or temperature have a rotationally symmetrical shape for easy screwing into assemblies. They often consist of a metal flange with internal electronics and a plastic cover that protects the integrated electronics from splash water while simultaneously preventing interference with sensor signals such as ultrasonic wavelengths. Currently, these composites are manufactured using adhesives, screwing, or clamp rings.

[0011] A disadvantage of the prior art is that known processes require additional material, are slow and difficult to automate, and / or are only suitable for flat joining surfaces. The objective is therefore to provide a process for producing a molded body composite that overcomes the disadvantages of the prior art and, in particular, enables media-tight molded body composites from complex molded bodies, and in particular from rotationally symmetrical molded bodies, without the use of additional material.

[0012] According to the invention, the object is achieved by a method having the features according to independent claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

[0013] According to the invention, a method for producing a molded body composite comprises at least the steps: a) providing at least one inductively heatable molded body and at least one thermoplastic molded body, b) fixing the inductively heatable molded body and the thermoplastic molded body to one another by means of a first joining force, c) heating the inductively heatable molded body at least in the joining region, d) joining the molded bodies by applying at least a second joining force.

[0014] This advantageously creates a strong and media-tight connection between the molded bodies. Furthermore, it advantageously creates an at least partially material- and / or form-fitting molded body composite.

[0015] An inductively heatable molded body within the meaning of the invention comprises molded bodies that at least partially comprise at least one electrically conductive material. The melting temperature of the electrically conductive material is at least 1.5 times the melting temperature of the thermoplastic material of the thermoplastic molded body. Electrically conductive materials include metals, some semimetals, in particular certain modifications of carbon, and / or electrically conductive ceramics. Electrically conductive ceramics include, for example, non-oxide ceramics, such as carbides and / or nitrides, or doped ceramics.

[0016] In embodiments, in step a), an inductively heatable molded body is provided, which is at least partially inductively heatable, particularly in the joining region. Such a molded body comprises at least partially, particularly in the joining region, at least one electrically conductive material, such as metal and / or ceramic.

[0017] In further embodiments, in step a), an inductively heatable molded body is provided that is completely inductively heatable. Such a molded body consists entirely of at least one electrically conductive material, such as metal and / or ceramic.

[0018] Thus, in step a), an inductively heatable molded body is provided, which at least partially comprises at least one electrically conductive material. Further components of the inductively heatable molded body can thus also be non-electrically conductive materials, the melting temperature of which is at least 1.5 times the melting temperature of the thermoplastic material of the thermoplastic molded body.

[0019] A thermoplastic molded body within the meaning of the invention comprises molded bodies that at least partially comprise at least one thermoplastic material. "At least partially" means that the thermoplastic molded body has at least one thermoplastic material at least in the joining region or that this material forms the joining region. The thermoplastic material can be present as a coating of the at least partially thermoplastic molded body, wherein the coating is arranged at least in the joining region of the thermoplastic molded body. Furthermore, the at least one thermoplastic material can completely form the thermoplastic molded body or a region of the thermoplastic molded body, in particular the joining region of the thermoplastic molded body.

[0020] In embodiments, step a) provides a thermoplastic molded body consisting entirely of at least one thermoplastic material. In further embodiments, step a) provides a thermoplastic molded body that is designed as a fiber-reinforced thermosetting molded body having a thermoplastic coating, at least in the joining region, or as a fiber-reinforced thermoplastic molded body. The fibers comprise any known fibers used as reinforcement, such as short, long, or continuous fibers made of glass, carbon, aramid, basalt, and / or other materials and additives.

[0021] In step b), the molded bodies to be joined are fixed to one another by means of a first joining force. Fixing in the sense of the invention means that the molded bodies to be joined are fixed in a spatial position relative to one another by applying a first joining force for the subsequent process step c). In embodiments, the molded bodies to be joined are advantageously fixed to one another in a position that approximately corresponds to a final composite position. This is advantageous if molded bodies with a non-rotationally symmetrical or a rotationally symmetrical joining region are provided in step a). In further embodiments, the molded bodies to be joined are fixed to one another in a position that deviates significantly from the final joining position. This is advantageous if molded bodies with a rotationally symmetrical joining region are provided in step a).A joining force within the meaning of the invention means a force applied from the outside to the shaped bodies to be joined.

[0022] In step c), the inductively heatable molded body is heated at least in the joining area. This is advantageous if an inductively heatable molded body is provided in step a) that is at least partially inductively heatable, particularly in the joining area. This advantageously melts the thermoplastic molded body that was fixed in position relative to the inductively heatable molded body in step b). The heating of the thermoplastic molded body advantageously takes place locally where there is direct contact with the inductively heatable molded body due to the fixing in step b).

[0023] In embodiments, the inductively heatable molded body is heated completely in step c). This is advantageous if a completely inductively heatable molded body is provided in step a).

[0024] In step d), the molded bodies to be joined are joined to form a molded body composite by applying at least a second joining force. Advantageously, the molded bodies to be joined move relative to one another until a final bonded position is reached. In embodiments, the relative movement ranges from 0.1 mm to 20 mm. In embodiments, the joining in step d) is force- and / or displacement-controlled, e.g., by means of a servo drive. In embodiments, two second joining forces can be applied in step d), which act in opposite directions to one another. This advantageously allows, for example, a molded body composite to be produced in which two thermoplastic molded bodies enclose an inductively heatable molded body in the joining area.

[0025] In further embodiments, the first and / or the at least one second joining force can be applied with a defined force-time curve or a defined force-displacement curve. A defined force-time curve means, for example, a reduction in force over time, and a defined force-displacement curve means a reduction in force depending on the final bonded position achieved by the molded bodies to be joined.

[0026] In embodiments, the first and / or second joining force is applied in a controllable and / or adjustable manner. This advantageously ensures that the dimensional accuracy of the molded body composite is maintained. For this purpose, in embodiments, after a predetermined target value of the respective joining force has been reached, the actual position of the molded bodies to be joined is checked and, if there are deviations between the actual position and the target position of the molded bodies to be joined, the respective joining force is controlled and / or regulated. In embodiments, the method is carried out in the order a), b), c) and d). In further embodiments, step d) can be carried out at least partially simultaneously with step c). This means that steps c) and d) overlap at least partially in time. In embodiments, step d) can be carried out entirely simultaneously with step c).

[0027] If several inductively heatable and / or thermoplastic molded bodies are provided in step a), steps b), c) and d) can be carried out simultaneously or successively.

[0028] Advantageously, the process according to the invention can be used to produce a molded body composite comprising an inductively heatable molded body and at least two thermoplastic molded bodies, in which the inductively heatable molded body is circumferentially enclosed by the thermoplastic molded bodies. In embodiments, an inductively heatable molded body and at least two thermoplastic molded bodies are provided in step a). In step b), the molded bodies are fixed to one another in such a way that the at least two thermoplastic molded bodies enclose the inductively heatable molded body. In step c), the inductively heatable molded body is heated at least in the joining region with each of the at least two thermoplastic molded bodies, so that a local fusion of the at least two thermoplastic molded bodies occurs simultaneously.Joining the molded bodies by applying at least a second joining force in step d) can be carried out partially or completely simultaneously with step c). In step d), two second joining forces are applied that act in opposite directions to each other.

[0029] A joining region within the meaning of the invention means a region of the molded bodies to be joined in which there is direct contact between the at least one inductively heatable molded body and the at least one thermoplastic molded body in the so-called joining plane and which together form the connecting region of the joined molded bodies in the molded body composite. In embodiments, the joining plane can run perpendicular to the first and / or the at least one second joining force or in the direction of the first and / or the at least one second joining force or parallel to it. A joining region with a joining plane that is perpendicular to the first and / or the at least one second joining force or a joining region with a joining plane that runs in the direction of or parallel to the first and / or the at least one second joining force can also be referred to as a radial or axial joining region.In the case of shaped bodies with rotationally symmetric joining areas, the joining plane can be a curved surface.

[0030] The molded bodies to be joined or the molded body composite thus have at least one joining area or connection area. Thus, a molded body composite comprising molded bodies with rotationally symmetrical joining areas in some embodiments has a radial joining area and an axial joining area, whereby the dimensions of the axial joining area can be larger than the dimensions of the radial joining area. The joining area with the larger dimensions then represents the main joining area, through which the load-bearing connection of the molded bodies to be joined is primarily achieved.

[0031] If the molded body composite is produced from several inductively heatable and / or thermoplastic molded bodies, the molded body composite can have one common or several joining areas or connecting areas.

[0032] The joining area or main joining area as well as the connection area have extensions along different directions, whereby these extensions must be designed depending on the expected loads on the molded body composite. In the case of a rotationally symmetrical joining area, the joining area has at least one axial extension in the direction of the axis of symmetry and one extension in the direction of the circumference (also called length), i.e. perpendicular to the axis of symmetry, within the joining plane. In the case of a non-rotationally symmetrical joining area, the joining area has a first extension, running in the direction of the main loading direction of the molded body composite and a second extension, running perpendicular to the first extension, within the joining plane.

[0033] In some embodiments, the axial or first dimension of the joining or connection area of ​​the molded body composite, which is subject to moderate loads, is in the range of 2 mm to 3 mm. In other embodiments, the axial or first dimension of the joining or connection area of ​​the molded body composite, which is subject to high loads, is in the range of 5 mm to 20 mm, preferably 6 mm to 10 mm. Moderate loads are understood to mean tolerable shear stresses of 5 to 15 MPa. High loads mean shear stresses above 15 MPa in the connection area.

[0034] In embodiments, the molded bodies to be joined are geometrically designed so that they theoretically overlap in the joining area. Overlap means that the molded bodies cannot be fixed in the unjoined state to form the geometrically defined molded body composite without deforming and possibly destroying the molded bodies. In embodiments, the overlap along the radial and / or first extent is at least 0.05 mm - 5 mm, preferably 0.1 mm - 2 mm. This means that the geometric dimensions of the molded bodies to be joined are designed with rotationally symmetrical joining areas in the sense of at least a slight press fit. The degree of overlap should preferably compensate for the component tolerances of the respective molded bodies as well as the cavities created by undercut structures in the inductively heatable molded body.

[0035] In preferred embodiments, in step a) at least one of the shaped bodies is provided with a rotationally symmetrical joining region.

[0036] Advantageously, the molded body itself does not need to be rotationally symmetrical, but only its joining area, i.e., the area of ​​the molded body that forms the connection area with the other molded body in the molded body composite. This advantageously allows even complex molded bodies to be joined together to form a molded body composite, as long as at least one of the molded bodies has a rotationally symmetric joining area.

[0037] Rotationally symmetrical in the sense of the invention means both simple and multiple rotational symmetries.

[0038] In some embodiments, the extension of the joining area in the direction of the symmetry axis of the rotationally symmetric joining area, also called the axial extension, is 0.1 mm to 20 mm, preferably 3 mm to 10 mm. The axial extension of the joining areas of the molded bodies to be joined corresponds to the axial extension of the connection area in the finished molded body composite.

[0039] In further embodiments, at least one of the joining regions of the molded bodies to be joined is conical. This means that the surfaces of the joining regions of the molded bodies to be joined do not run parallel to the axis of symmetry along their axial extent, but are inclined at an angle to the axis of symmetry. If the joining regions of both molded bodies are conical, the conicities of the inductively heatable and the thermoplastic molded body correspond to one another, so that there is an overlap between the molded bodies to be joined at every point in the joining region. This advantageously ensures that one molded body can be inserted into the other molded body or is received by the other molded body along the axial extent of the joining region. The inductively heatable molded body is preferably inserted into the thermoplastic molded body.In further embodiments, the thermoplastic molded body is introduced into the inductively heatable molded body. In this way, the molded bodies to be joined are guided towards one another in a defined manner. In embodiments, the surfaces of the joining regions are the inner surface of the receiving molded body and the outer surface of the received molded body, which are connected to one another. In further embodiments, the surfaces of the joining regions of the molded bodies to be joined are inclined by 0.1° - 5°, preferably 1 - 1.5°, relative to the axis of symmetry. In further embodiments, the molded bodies are designed such that the ratio of the axial extent of the joining region to the diameter of the molded body composite is in the range of 0.1 - 1.

[0040] In preferred embodiments, in step a) at least one of the shaped bodies is provided with at least one collecting structure in the joining area.

[0041] Advantageously, the at least one collecting structure serves to collect the excess melt of the thermoplastic material formed by the heating in step c). Excess melt is defined as the proportion that is neither required to fill any roughnesses or cavities caused by undercut structures that may be present in the joining area nor to achieve a complete material and / or form fit in the connection area. This advantageously achieves a complete material and / or form fit connection between the molded bodies to be joined. The material and / or form fit connection is advantageously achieved even with molded body pairs that have high tolerances. High tolerance means that, for example,In the case of thermoplastic molded bodies produced by injection molding, tolerances in the joining plane in the range of 0.1 mm to 0.5 mm, in some cases up to 1 mm, can be compensated, and a material and / or form-fitting connection can advantageously be achieved. Even typical tolerances in the diameter of pipes produced by extrusion of up to + / -0.2 mm can be compensated, and a material and / or form-fitting connection can advantageously be achieved. Another advantage is that a clean connection point is created in the molded body composite, thus avoiding subsequent processing steps for removing melt that has escaped and solidified at the connection point.

[0042] In embodiments, in step a), the inductively heatable molded body and / or the thermoplastic molded body is provided with at least one collecting structure in the joining area.

[0043] In embodiments, the volume of the at least one collecting structure is at least equal to the volume of the melt of the thermoplastic material formed and maximally displaced during joining.

[0044] In embodiments, the at least one collecting structure is produced in the joining region of at least one of the shaped bodies by means of mechanical separation processes, for example turning or milling, in the form of a circumferential groove, channel or shoulder.

[0045] In embodiments, the at least one collecting structure is introduced into the joining region of at least one of the molded bodies during the production of the molded bodies, for example during injection molding or die-casting of the molded bodies. In further embodiments, the at least one collecting structure is arranged at at least one edge of the joining region or, in the case of partially rotationally symmetrical joining regions, at at least one end of the joining region. An edge of the joining region means an end of the joining region along the first and / or second extent of the joining region in the case of molded bodies with non-rotationally symmetrical joining regions. An end of the joining region here means a first or a second end of a rotationally symmetrical joining region, which is in each case arranged along the axial extent of the joining region.

[0046] In embodiments, molded bodies are provided in step a), each having at least one collecting structure, which is arranged at opposite ends of the axial or second extension of the forming connection region. Thus, the connection region of the molded body composite advantageously has a collecting structure at both ends of the axial or second extension. Furthermore, this advantageously prevents the melt from escaping at the ends or edges of the connection region, since the excess melt is completely absorbed by the collecting structures.

[0047] In embodiments, the collecting structures are each produced with a depth in the range from 0.1 mm to 3 mm, preferably 0.2 mm to 1 mm. The depth extends perpendicular to the joining plane in the direction of the first and / or the at least one second joining force or, in the case of partially rotationally symmetrical shaped bodies, perpendicular to the axis of symmetry. In further embodiments, the collecting structures are each produced with a length that corresponds to the maximum longitudinal extent of the joining region. In the case of partially rotationally symmetrical shaped bodies, the length corresponds to the circumference of the joining region; in the case of non-rotationally symmetrical joining regions, the length extends along the second extent. In embodiments, the at least one collecting structure is produced with a width in the range from 0.5 mm to 2 mm, wherein the width in the case of rotationally symmetrical joining regions extends along the axial extent orin the case of non-rotationally symmetrical joining areas, it is aligned along the first dimension.

[0048] The dimensions, or rather the depth and width, of the collecting structure are generated depending on the maximum volume of the melt of the thermoplastic material to be absorbed. The melt quantity is determined by the geometric overlap of the molded bodies in the joining area.

[0049] In some embodiments, the geometric overlap is selected so that the joining area can be completely filled with melt across the entire tolerance range of the mold pairing. For a rotationally symmetric and cylindrical joining area, the maximum volume of the melt of the thermoplastic material to be collected can be calculated using formula (1).

[0050] V = TI ' l ■ (r2 2 - r ) (1)

[0051] Where V... is the maximum volume of the melt to be displaced, I... is the axial extent of the joining area, n... is the inner radius of the outer mold body, r2... is the outer radius of the inner mold body. If there is no overlap in the joining area, a negative volume value results. Therefore, in certain embodiments, the overlap must be selected so that the melt volume is > 0 even with a maximum inner radius of the outer mold body and a minimum outer radius of the inner mold body.

[0052] In embodiments, the volume of the collecting structure is at least equal to the difference between the volume of the excess melt of the thermoplastic material and the volume of the undercut structures to be filled.

[0053] In embodiments, the dimensions of the at least one collecting structure in the case of shaped bodies to be joined with rotationally symmetrical joining regions can be determined as follows.

[0054] 1. Determination of the minimum overlap of the molded bodies to be joined in the joining area, whereby the maximum dimension of the inner radius of the outer arranged or receiving molded body and the minimum dimension of the outer radius of the inner or received molded body are taken into account and the calculation of the minimum melt volume V to be displaced m in accordance with formula (2).

[0055] 2. Determination of the maximum overlap of the molded bodies to be joined in the joining area, whereby the minimum dimension of the inner radius of the outer arranged or receiving molded body and the maximum dimension of the outer radius of the inner or received molded body are taken into account and the calculation of the maximum melt volume to be displaced V ma x according to formula (2).

[0056] With Vmin / max.... volume of the melt to be displaced, h... axial extension of the joining area, rn... upper inner radius of the outer or receiving mold body, ri2... lower inner radius of the outer or receiving

[0057] Form body, r2i... upper outer radius of the inner or also recorded

[0058] Form body, r22... lower outer radius of the inner or also recorded

[0059] molded body.

[0060] The upper inner radius of the outer mold body refers to an inner radius at a first end of the joining area of ​​the outer mold body. The first end of the joining area of ​​the outer mold body is located away from the component end of the outer mold body located in the joining area.

[0061] A lower inner radius of the outer mold body refers to an inner radius at a second end of the joining area of ​​the outer mold body. The second end of the joining area of ​​the outer mold body is located near the component end of the outer mold body located in the joining area.

[0062] An upper outer radius of the inner mold body refers to an outer radius at a first end of the joining area of ​​the inner mold body. The first end of the joining area of ​​the inner mold body is located near the component end of the inner mold body located in the connecting area.

[0063] A lower outer radius of the inner mold body refers to an outer radius at a second end of the joining area of ​​the inner mold body. The second end of the joining area of ​​the inner mold body is located away from the component end of the inner mold body located in the joining area.

[0064] The first and second ends of the joining region of a molded body are each arranged opposite one another along the axial extent of the joining region of each molded body.

[0065] 3. Determination of the volume VHS of the cavities created by the undercut structures and to be filled by the melt. The volume of the undercut structures can be determined based on their geometric dimensions and expansion in the joining area.

[0066] 4. Determination of the minimum volume VA of the planned containment structures according to the following formula (3):

[0067] With VA.... volume of the collecting structures, h... width of the collecting structures, rsi ... outer radius of the inner or received shaped body in the area of ​​the upper collecting structure, r32... inner radius of the outer or receiving shaped body in the area of ​​the upper collecting structure, i... outer radius of the inner or received shaped body in the area of ​​the lower collecting structure, 2... inner radius of the outer or receiving shaped body in the area of ​​the upper collecting structure.

[0068] The upper collecting structure means a collecting structure that is arranged at the first end of the joining area of ​​the inner molded body or at the first end of the joining area of ​​the outer molded body.

[0069] The lower collecting structure means a collecting structure that is arranged at the second end of the joining area of ​​the inner molded body or at the second end of the joining area of ​​the outer molded body.

[0070] 5. Verification of the determined values ​​under the following conditions a) Vmin > 0 b) Vmin > HS

[0071] C) A > max HS

[0072] In preferred embodiments, the at least one collecting structure is formed in the form of at least one groove and / or a shoulder and / or a depression.

[0073] As a result, the excess melt volume of the thermoplastic material formed in step c) can advantageously be absorbed by the collecting structures and a material and / or form-fitting connection of the molded bodies to be joined can be achieved.

[0074] In preferred embodiments, the inductively heatable molded body is provided with at least one undercut structure in the joining area.

[0075] Advantageously, the at least one undercut structure achieves a preferably positive connection between the shaped bodies to be joined.

[0076] In further embodiments, the at least one undercut structure is created in the joining area. In some embodiments, the undercut structure can be created either by material removal or by a local buildup of material. In further embodiments, the at least one undercut structure can completely cover the joining area without geometrically damaging any at least one retaining structure that may be present.

[0077] In further embodiments, the undercut structures are preferably formed as a linear structure; in the case of rotationally symmetrical joining areas, for example, in the form of a thread or a helix; or as a plurality of linear structures. The plurality of linear structures can each be straight, curved, and / or angled and can also intersect one another. This advantageously allows for a variety of different undercut structures, which are selected depending on the expected load on the molded body composite. Undercut structures for rotationally symmetrical molded body composites can be created, for example, in the form of opposing threads or knurls.

[0078] In further embodiments, the undercut structures are created perpendicular to the main loading direction of the finished molded composite. The main loading direction of the finished molded composite refers to the direction in which the predominant loading of the molded composite occurs during use.

[0079] In further embodiments, the cavities created by at least one undercut structure are taken into account when determining the minimum required geometric overlap of the molded body partners.

[0080] In preferred embodiments, the at least one undercut structure is formed with height differences in the range of 30 μm to 2 mm. The height difference is the difference in height between structures manufactured using additive processes and the trenches or groove depths created using subtractive processes. The height is oriented perpendicular to the symmetry axis for rotationally symmetric joining areas, and perpendicular to the joining plane for non-rotationally symmetric joining areas.

[0081] An overlay of a coarse and a fine macrostructure is advantageously achieved. Furthermore, the coarse macrostructure ensures force transmission in the joint area of ​​the molded body composite. The fine macrostructure advantageously ensures media-resistant sealing in the joint area of ​​the molded body composite.

[0082] A coarse macrostructure refers to undercut structures whose preferably linear structures are each produced with a structure depth or height in the range of 0.5 mm to 2 mm and a structure width of 1 mm to 2 mm. A fine macrostructure refers to undercut structures whose linear structures are each produced with a structure depth or height in the range of 30 pm to 300 pm and a structure width in the range of 50 pm to 200 pm. The structure depth runs largely perpendicular to the joining plane or, in the case of rotationally symmetrical joining areas, largely perpendicular to the axis of symmetry. The structure width is aligned along the axial or first extent of the joining area. In embodiments, undercut structures are produced as a coarse macrostructure using mechanical processes, e.g. turning or milling.In further embodiments, undercut structures are created as coarse macrostructures using additive processes, such as powder or wire deposition welding or 3D printing. In further embodiments, undercut structures are created as fine macrostructures using laser-based processes, such as laser remote structuring.

[0083] In further embodiments, undercut structures formed as coarse macrostructures can be arranged, for example, for transmitting torques or tensile loads, at the ends or edges of the joining area of ​​the inductively heatable molded body. In further embodiments, undercut structures formed as fine macrostructures can be arranged in a central region adjacent to the ends or edges of the joining area to achieve media tightness.

[0084] In preferred embodiments, in step b) a first joining force in the range of 0.2 kN to 2 kN is applied.

[0085] Advantageously, the molded bodies to be joined are thus fixed in a defined position relative to one another. In some embodiments, the fixation serves to monitor dimensional accuracy and the degree of geometric overlap. Also advantageous is the locally defined surface contact between the at least one inductively heatable molded body and the at least one thermoplastic molded body. This allows the heat generated in the inductively heatable molded body to be evenly absorbed by the plastic in step c).

[0086] In embodiments, the first joining force in step b) can be applied via a predefined force-time curve and / or force / displacement curve.

[0087] In some embodiments, once the target force has been reached, the actual position is checked by a servo drive.

[0088] In preferred embodiments, in step d) the at least one second joining force is applied in the range of 0.2 kN to 10 kN.

[0089] Advantageously, the molded bodies to be joined move relative to each other until a final bonded position is reached. Furthermore, the at least one second joining force presses the formed melt of the thermoplastic material into the collecting structure and the undercut structures, thus achieving a material and / or form-fitting connection between the molded bodies to be joined.

[0090] In embodiments, the relative movement occurs in the range of 0.1 mm to 20 mm, preferably 3 mm to 10 mm. In preferred embodiments, the first and at least one second joining force are each applied in the axial direction.

[0091] This advantageously prevents the molded bodies from tilting during joining. In some embodiments, a servo drive can apply both the first and the at least one second joining force.

[0092] An axial direction means a direction that runs along the axis of symmetry of a rotationally symmetrical joining area and / or perpendicular to the joining plane in the case of non-rotationally symmetrical joining areas.

[0093] In embodiments, two molded bodies with a rotationally symmetrical joining area are aligned centrally to each other by a shoulder in step b) and fixed by the first joining force; then, by applying at least a second joining force, a relative movement between the molded bodies takes place in the direction of the joining forces until the final joining position is reached.

[0094] In preferred embodiments, the heating in step c) is carried out by means of an inductor for a period of time of 0.1 to 20 seconds, preferably 0.5 to 10 seconds.

[0095] This advantageously avoids unnecessarily high heating of the inductively heatable molded body.

[0096] An inductor in the sense of the invention means a device that is suitable for generating an electromagnetic field in such a way that the inductively heatable body is heated.

[0097] In some embodiments, the inductor for heating in step c) is arranged at a distance of 1 mm to 10 mm from the molded bodies to be joined. In some embodiments, the thermoplastic molded body can be arranged between the inductor and the inductively heatable molded body, or the inductively heatable molded body can be arranged between the inductor and the thermoplastic molded body.

[0098] In embodiments, the heating in step c) is carried out with a fixed or a rotating inductor.

[0099] In embodiments, the heating in step c) takes place with a heating power in the range of 1 kW to 30 kW.

[0100] In some embodiments, heating occurs at frequencies of 10–350 kHz. In preferred embodiments, the inductor and / or the molded bodies to be joined and fixed rotate in step c).

[0101] This advantageously results in uniform heating of the thermoplastic material in the joining area.

[0102] In some embodiments, the inductor rotates around the molded bodies to be joined and secured. The molded bodies to be joined and secured can be stationary or rotate around themselves.

[0103] In some embodiments, the molded bodies to be joined and fixed rotate around themselves. The inductor can be stationary or rotate around the molded bodies to be joined.

[0104] In further embodiments, heating takes place without rotation of the inductor and / or the molded bodies to be joined and fixed in step c). This means that the inductor and / or the molded bodies to be joined and fixed are stationary. This is preferably done for complex-shaped molded bodies. The inductor can then completely enclose the molded body.

[0105] In further embodiments, the inductor does not rotate in a circle around the molded body, but at an almost uniform distance from the molded body.

[0106] In some embodiments, an additional rotational movement is generated between the two axially fixed mold bodies. This advantageously simplifies the filling of the cavities of the undercut structures with the generated melt.

[0107] In embodiments, the rotation of the molded bodies and / or the inductor occurs at 30 to 500 revolutions per minute.

[0108] In preferred embodiments, a third joining force is additionally applied.

[0109] Advantageously, the bond between the molded bodies to be joined is improved. In some embodiments, the third joining force ensures complete filling of the undercut structures.

[0110] In embodiments, the third joining force is applied during step c) or after step c).

[0111] In further embodiments, the third joining force is applied by means of a pressure roller. In further embodiments, the pressure roller is spring-mounted. In further embodiments, the pressure roller is geometrically designed to allow a defined geometric shape in the joining area of ​​the molded body composite.

[0112] In further embodiments, the joining force is applied by means of one or more pressure elements that act radially on the rotationally symmetrical joining area. In further embodiments, the joining area can be subjected to force over its entire circumference. In further embodiments, the force is applied via a centering gripper.

[0113] In preferred embodiments, the third joining force is applied almost perpendicular to the first and the at least one second joining force.

[0114] This advantageously improves the connection of the molded bodies to be joined.

[0115] Almost perpendicular in the sense of the invention means that the direction of the third joining force encloses an angle in the range of 70° to 110° with the direction of the first and the at least one second joining force.

[0116] In embodiments, the third joining force is applied in a radial direction for rotationally symmetric joining areas. The radial direction is oriented perpendicular to the axis of symmetry.

[0117] In preferred embodiments, the third joining force is applied in the range of 100 N to 1000 N.

[0118] In preferred embodiments, the produced molded body composite is cooled after step d).

[0119] This advantageously accelerates the solidification of the melt of the thermoplastic material.

[0120] In some embodiments, cooling is carried out using compressed air or nitrogen

[0121] In further embodiments, cooling is carried out by a water-cooled holder of the inductively heatable molded body.

[0122] For the realization of the invention, it is also expedient to combine the above-described inventive embodiments, embodiments and features of the claims.

[0123] Embodiments The invention will be explained in more detail below using embodiments. These are intended to describe the invention without limiting it.

[0124] The invention is explained in more detail with the aid of drawings.

[0125] Fig. 1a shows an embodiment of the provided shaped bodies to be joined, each with a rotationally symmetrical, cylindrical joining area,

[0126] Fig. 1 b shows an enlargement of the section from Fig. 1a,

[0127] Fig. 1c shows the area from Fig. 1b after step b),

[0128] Fig. 2a-c various embodiments of an inductively heatable molded body provided with an undercut structure,

[0129] Fig. 3 shows an embodiment of the provided shaped bodies to be joined with their geometric dimensions for determining the geometric sizes of the collecting structure,

[0130] Fig. 4 schematically shows an embodiment of a method according to the invention,

[0131] Fig. 5 different embodiments of step c).

[0132] Example 1

[0133] A molded body composite is produced by providing at least one inductively heatable molded body (1) and at least one thermoplastic molded body (2) in step a) according to Fig. 1 (a), (b). In one embodiment, the thermoplastic molded body (2) is provided as a glass fiber or carbon fiber reinforced thermoplastic pipe with an outer diameter of 80 mm and a wall thickness of 2 mm and a length of 500 mm. In order to connect several such thermoplastic pipes to one another, connecting pieces, so-called fittings, are used. The inductively heatable molded body (1) is provided as a stainless steel fitting with an outer diameter of 80 mm and a wall thickness of 4 mm. The thermoplastic pipe (2) and the stainless steel fitting (1) are each provided as rotationally symmetrical molded bodies (1, 2) and have a rotationally symmetrical nominal joining area with an axial extent (1.2, 2.2) of 10 mm.In further embodiments, the joining regions (1.2, 2.2) of the shaped bodies (1, 2) to be joined can each be conical along their axial extent, i.e. the surfaces of the joining regions are each inclined by 1° to 1.5° with respect to the axis of symmetry (3) in such a way that the conicities correspond to one another. This advantageously achieves the result that in step b) the thermoplastic pipe (2) can slide over a region of the stainless steel fitting (1) and is guided in a defined manner (see Fig. 1 (c)). The joining regions (1.2, 2.2) of the shaped bodies (1, 2) to be joined are designed in such a way that a slight press fit is present. For example, the thermoplastic pipe (2) is provided with a tolerance H7 and the fitting (1) with a tolerance n6. Fig. 1c shows the shaped bodies to be joined.

[0134] (1 . 2) after step b). The slight interference fit of the formed bodies (1 , 2) to be joined is expressed in an overlap (4) along the radial extent of the formed bodies (1 , 2) in the joining area (1.2, 2.2) or connection area (5).

[0135] In embodiments according to Fig. 1 (a) - (c), the fitting (1) is provided with at least one collecting structure (1.3) in the joining region (1.2), which is designed as a circumferential shoulder (1.3) with a depth in the range of 0.3 mm and a width in the range of 1.5 mm. The collecting structure (1.2) is arranged at one end of the axial extension of the joining region (1.2). Furthermore, according to Fig. 1 (a) - (c), the thermoplastic molded body (2) is also provided with a collecting structure (2.3) in the form of a shoulder with a depth of 3 mm and a width of 2 mm. The collecting structure (2.3) is arranged at one end of the axial extension of the joining region (2.2). The ends of the axial extension of the joining areas (1.2, 2.2) are opposite each other along the axial extension of the connecting area (1, 2, 2.2, 5). According to Fig. 2 (a) - (c), the fitting (1) can further be provided with an undercut structure (1.4) in the joining area (1.2) are provided, which is formed as an overlay of a coarse macrostructure produced by turning or milling, in the form of a plurality of circumferential grooves, each with a depth of 0.2 mm and a width of 1 mm; and a fine macrostructure produced by laser remote structuring, in the form of circumferential trenches, each with a depth of 100 pm and a width of 100 pm. Fig. 2 (a) shows an undercut structure (1.4) that was produced by subtractive processes (or material removal) in the form of trenches or depressions. Fig. 2 (b) and (c) show undercut structures (1.4) that were produced by additive processes (or material deposition).

[0136] The determination of the geometric sizes of the collecting structures (1.3, 2.3) can be carried out according to the following steps, Fig. 3 illustrates the geometric sizes of the shaped bodies

[0137] (1.2):

[0138] 1. Determination of the minimum overlap (4) of the shaped bodies (1, 2) in the joining area (1.2, 2.2), whereby the maximum dimension of the inner radius (determinable from 2.1) of the externally arranged shaped body (2) and the minimum dimension of the outer radius (determinable from

[0139] 1.1) of the inner mold body (1) and the calculation of the minimum melt volume V to be displaced m in accordance with formula (2).

[0140] 2. Determination of the maximum overlap (4) of the shaped bodies (1, 2) in the joining area (1.2,

[0141] 2.2), whereby the minimum dimension of the inner radius (determinable from 2.1) of the externally arranged mold body (2) and the maximum dimension of the outer radius (determinable from 1.1) of the internal mold body (1) are taken into account and the calculation of the maximum melt volume V to be displaced ma x according to formula (2).

[0142] Where Vmin / max. . . . volume of the melt to be displaced, h... axial extent of the joining area (1.2, 2.2), rn... upper inner radius (2.4) of the outer mold body (2), ri2... lower inner radius (2.5) of the outer mold body (2), r2i... upper outer radius (1.5) of the inner mold body (1), r22... lower outer radius (1.6) of the inner mold body (1).

[0143] 3. Determination of the volume VHS of the cavities created by the undercut structures (1.4) and to be filled by the melt.

[0144] 4. Determination of the minimum volume VA of the planned containment structures (1.3, 2.3) according to the following formula (3):

[0145] With VA.... volume of the collecting structures (1.3, 2.3), h... width of the collecting structures (1.3, 2.3), rai... outer radius (1.7) of the inner shaped body (1) in the area of ​​the upper collecting structure (1.3), r32... inner radius (2.4) of the outer shaped body (2) in the area of ​​the upper collecting structure (2.3), r4i... outer radius (1.6) of the inner shaped body (1) in the area of ​​the lower collecting structure (2.3), 2... inner radius (2.6) of the outer shaped body (2) in the area of ​​the lower collecting structure (1.3).

[0146] 5. Verification of the determined values ​​under the following conditions a) Vmin > 0 b) Vmin > VHS c) VA > Vmax VHS

[0147] In this application example, the following values ​​result:

[0148] Vmin: 76 mm 3 ; V ma x: 102 mm 3 ; VHS: 63 mm 3 ; front: 52 mm 3In the next step b), as shown in Fig. 4 (b), the two molded bodies (1, 2) are fixed to each other using a first joining force (F1). For this purpose, the stainless steel fitting (1) is clamped in a lathe chuck (shown in Fig. 4 by the thick arrow), and the thermoplastic pipe (2) is fixed in a free-running lathe chuck and pressed axially onto the stainless steel fitting (1) with a defined first joining force (F1) of 200 N.

[0149] Subsequently, in step c), the fitting (1) is heated, at least in the joining area (1.2), for 3 seconds at a generator power of 15 kW using a stationary inductor (6) arranged at a distance of 2 mm. During heating, both the thermoplastic pipe (2) and the fitting (1) rotate at a rotation speed of 60 rpm (indicated in Fig. 4 (a) to (c) by the curved arrow), so that uniform heating of the joining area (1.3, 2.3) is achieved.

[0150] In the next step d), a second joining force (F2) of 1000 N is applied in the axial direction as shown in Fig. 4 (c), with the axial direction running along the axis of symmetry (3) of the thermoplastic molded body (2). This advantageously achieves a relative movement between the molded bodies (1, 2) to be joined into a final bonded position, and the melt of the thermoplastic material formed by the heating in step c) is pressed into the undercut and collecting structures (1.3, 2.3, 1.4).

[0151] This advantageously achieves a media-tight, material-locking and form-fitting connection between the two molded bodies (1, 2), wherein both molded bodies (1, 2) are materially and / or form-lockingly connected to one another over a length of at least 7 mm, i.e., the connection region (5) of the finished molded body composite has an axial extension of at least 7 mm. Advantageously, subsequent processing steps for removing any melt leaked out in the connection region (5) are omitted, since this is completely absorbed by the undercut and collecting structure (1.3, 2.3, 1.4).

[0152] In further embodiments of the method, in addition to the second joining force (F2), a third joining force (F3) according to Fig. 4 (c) in the range of 100 N can be applied perpendicular to the second joining force (F2). This joining force (F3) is generated by a spring-loaded, freely rotating roller. It ensures that the outer diameters of pipe (2) and fitting (1) are aligned in the joining area (1.2, 2.2).

[0153] Fig. 5 shows various embodiments of step c) of the method according to the invention. Thus, Fig. 5 (a) shows stationary mold bodies (1, 2) fixed by the first joining force (F1) and an inductor (6) rotating around the mold bodies (1, 2) during step c).

[0154] Fig. 5 (b) shows self-rotating mold bodies (1, 2) and an inductor (6) rotating around the mold bodies (1, 2) fixed by the first joining force (F1) in step c).

[0155] Fig. 5 (c) shows self-rotating mold bodies (1, 2) and a stationary inductor (6) in step c). The rotation of the mold body (1, 2) and / or inductor (6) is represented by the curved arrow in Fig. 5 (a) to (c). Analogous to Fig. 4, the thick arrow represents the clamping of the inductively heatable mold body (1) in a lathe chuck.

[0156] Reference symbol

[0157] 1 Inductively heatable molded body

[0158] 1.1 Outer diameter of the inductively heatable molded body in the joining area di

[0159] 1.2 Joining area of ​​the inductively heatable molded body or axial extension of the joining area

[0160] 1.3 At least one collecting structure in the joining area of ​​the inductively heatable molded body

[0161] 1.4 At least one undercut structure

[0162] 1.5 upper outer radius of the inner mold body

[0163] 1.6 Outer radius of the inner molded body in the area of ​​the lower collecting structure

[0164] 1.7 Outer radius of the inner molded body in the area of ​​the upper collecting structure

[0165] 2 Thermoplastic molded body

[0166] 2.1 Inner diameter of the thermoplastic molded body in the joining area d2

[0167] 2.2 Joining area of ​​the thermoplastic molded body or axial extension of the joining area

[0168] 2.3 At least one collecting structure in the joining area of ​​the thermoplastic molded body

[0169] 2.4 upper inner radius of the outer molded body or inner radius of the outer molded body in the area of ​​the upper collecting structure

[0170] 2.5 lower inner radius of the outer mold body

[0171] 2.6 Inner radius of the outer molded body in the area of ​​the lower collecting structure

[0172] 3 axis of symmetry

[0173] 4 Coverage

[0174] 5 Connection area of ​​the molded body composite

[0175] 6 Inductor

[0176] F1 First joining force F2 At least a second joining force

[0177] F3 Third joining force

Claims

Patent claims 1. A method for producing a molded body composite comprising at least the steps: a) providing at least one inductively heatable molded body and at least one thermoplastic molded body, b) fixing the inductively heatable molded body and the thermoplastic molded body to one another by means of a first joining force, c) heating the inductively heatable molded body at least in the joining region, d) joining the molded bodies by applying at least a second joining force.

2. Method according to claim 1, characterized in that at least one of the shaped bodies is provided with a rotationally symmetrical joining region.

3. Method according to claim 1 or 2, characterized in that at least one of the shaped bodies is provided with at least one collecting structure in the joining area.

4. Method according to claim 3, characterized in that the at least one collecting structure is formed in the form of at least one groove and / or a shoulder and / or a depression.

5. Method according to one of claims 1 to 4, characterized in that the inductively heatable shaped body is provided with at least one undercut structure in the joining area.

6. Method according to claim 5, characterized in that the at least one undercut structure is formed with height differences in the range of 30 pm to 2 mm.

7. Method according to one of claims 1 to 6, characterized in that in step b) a first joining force in the range of 0.2 kN to 2 kN is applied.

8. Method according to one of claims 1 to 7, characterized in that in step d) the at least one second joining force is applied in the range from 0.2 kN to 5 kN.

9. Method according to one of claims 1 to 8, characterized in that the first and the at least one second joining force are each applied in the axial direction.

10. The method according to any one of claims 1 to 9, characterized in that the heating in step c) is carried out by means of an inductor for a period of time of 0.1 to 20 seconds.

11. The method according to claim 10, characterized in that in step c) the inductor and / or the shaped bodies to be joined and fixed rotate.

12. Method according to one of claims 1 to 11, characterized in that a third joining force is additionally applied.

13. The method according to claim 12, characterized in that the third joining force is applied almost perpendicular to the first and the at least one second joining force.

14. Method according to one of claims 12 or 13, characterized in that the third joining force is applied in the range from 100 N to 1000 N.

15. The method according to any one of claims 1 to 14, characterized in that after step d) the molded body composite produced is cooled.

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