Process for manufacturing plastic components

Abstract

The present invention relates to a process for manufacturing a plastic component (1) comprising an insert (13) surrounded by a hollow body (11), the process comprising: (a) placing an insert (13) in a mold such that a gap is formed between the insert (13) and the mold; (b) feeding a polymer melt into the gap, thereby forming a hollow body (11) surrounding the insert (13); (c) removing the plastic component (1) from the mold; To form the gap, a ridge (17) is formed on the insert (13), or the mold has a pin (25) on which the insert is placed, or the gap is a recess in the insert (13).

Description

[Technical Field]

[0001] The present invention relates to a process for manufacturing a plastic component including an insert surrounded by a hollow body, the process including: (a) placing the insert in a mold such that a gap is formed between the insert and the mold; (b) supplying a polymer melt into the gap, thereby forming a hollow body surrounding the insert; and (c) removing the plastic component from the mold. [Background technology]

[0002] Plastic components manufactured by injection molding must be designed to meet the limitations and boundary conditions imposed by the injection molding process, which typically result from mass buildup and the release of the injection molded plastic component upon mold opening.

[0003] Mass buildup typically results in higher cycle times because plastic components require longer cooling times. Mass buildup also increases the risk of internal void buildup. For this reason, plastic components manufactured by injection molding processes should have small wall thicknesses.

[0004] To demold the plastic component, it is necessary that each internal core, insert, or geometric design that reduces mass buildup must have a shape that allows the mold to be opened and the plastic component to be removed, which places constraints on the shape of the plastic component and requires a mold with complex moving cores and complex kinematics for opening and closing.

[0005] Currently, there are several non-standard injection molding processes that can produce hollow parts to avoid such mass accumulation, such as gas-assisted injection molding (GAIM), water-assisted injection molding technology (WIT), or fusible core technology.

[0006] In GAIM / WIT, a mold is completely filled with polymer melt, and then some of the hot polymer melt is forced out of the mold by injecting a liquid, usually water, or gas. This liquid or gas injection leaves the polymer melt in contact with the mold walls, forming a hollow section. In fusible core technology, a metal core is inserted into the mold and then melted to form the hollow section.

[0007] The GAIM / WIT process has the disadvantage that complex injection machinery is required to inject the liquid or gas, and furthermore, due to the high pressure and velocity of the liquid or gas, the wall thickness of the hollow part or plastic component may be non-uniform. In the fusible core technology, the removal of the metal core results in an additional process step.

[0008] Summary of the Invention It is therefore an object of the present invention to provide a process for producing plastic components without mass build-up, which does not have the drawbacks of the known GAIM / WIT process or fusible core technology.

[0009] This object is achieved by a process for manufacturing a plastic component comprising an insert surrounded by a hollow body, the process comprising: (a) placing an insert into a mold such that a gap is formed between the insert and the mold; (b) delivering a polymer melt into the gap, thereby forming a hollow body surrounding the insert; (c) removing the plastic component from the mold; To form the gap, a ridge is formed on the insert, or the mold has a pin onto which the insert rests, or the gap is a recess in the insert.

[0010] By using an insert and retaining the insert within the plastic component, it is possible to produce a plastic component including sections with different wall thicknesses without the drawbacks of known processes. Particularly when low-weight inserts are used, plastic components can be produced that are lighter than plastic components with walls made of solid material. Furthermore, when the gap is a recess within the insert, the polymer melt distribution point can be located in a position that cannot be achieved by the injection point in the mold, such as below the insert, thereby achieving balanced filling and undisturbed fiber orientation to take advantage of anisotropic material behavior and reduce warpage of the plastic component.

[0011] Furthermore, the insert forms part of the mold by forming a gap using a protrusion formed on the insert or pin in the mold into which the insert is placed, or a gap that is a recess in the insert. Therefore, the walls of the plastic component forming the hollow body have a defined thickness and shape that differs from walls produced by known GAIM / WIT processes. Unlike fusible core technology, the insert remains within the plastic component and is not melted, making the process much simpler. Standard injection molding processes can be used to produce plastic components using the process of the present invention, which also simplifies the process for producing plastic components. Other liquid plastic molding processes, such as casting processes (e.g., RIM), are also suitable.

[0012] To produce lightweight components, it is preferable to use inserts made of foam and / or a second hollow body. In particular, the inserts are made of foam. Due to the gas that forms the bubbles in the foam, the foam has a much lower density than a solid insert, which results in components that weigh less than comparable components with solid walls.

[0013] Since the insert forms part of the mold during polymer melt dispensing, it is necessary to use a material or insert construction that can withstand the loads and temperatures encountered during polymer melt dispensing.

[0014] When the insert is a second hollow body, it is preferable to manufacture at least two sections of the second hollow body and then connect the sections later to form the second hollow body. The connection can be achieved by welding, soldering, or adhesive bonding. Alternatively, the sections can be secured in the mold by ridges or pins and then placed together without fastening after they are surrounded by the polymer melt from the polymer forming the hollow body. However, to prevent displacement of the sections, it is preferable to provide grooves and tongues or recesses on the edges that meet when connected. When the second hollow body is formed by connecting at least two sections, it is particularly advantageous that the sections can be manufactured by standard processes, such as standard injection molding.

[0015] Depending on the size of the insert and the pressure acting on it, if the insert is a second hollow body, it may be necessary to reinforce the insert. To reinforce the second hollow body, the second hollow body may, for example, include columns or walls connecting the opposing interior walls of the second hollow body. The columns or walls connecting the opposing interior walls of the second hollow body may be separate parts that are placed on one part before connection with the second part, or they may be integrally formed with at least one part. If the columns or walls are integrally formed with one part, they preferably have a height such that the parts forming the opposing interior walls contact the upper ends of the columns or walls after connection with the integrally formed columns or walls. Furthermore, it is also possible to integrally form portions of the columns or walls on the parts that are positioned to form the opposing interior walls of the second hollow body, so that after connection of the hollow body parts, the walls or columns of the parts of the hollow body that form the opposing interior walls also contact, thus forming the columns or walls.

[0016] In addition to or in addition to the pillars or walls, the inner or outer walls of the second hollow body may be reinforced by ribs or other suitable geometric reinforcements formed in the walls of the sections to produce the second hollow body.

[0017] If the insert is made of foam, it must be one that essentially maintains its shape when the polymer melt is fed into the mold, and for this purpose, the insert is preferably made of a foam with high compression stiffness.

[0018] To further reduce the weight of the plastic component, the insert can also be a second hollow body made of foam. If the stability of such a second hollow body made of foam is too low, it can be filled with a lighter material. In the case of polyamide foam, for example, the foam can be made of thermoplastic polyurethane (TPU), expandable polyamide (EPA), or polystyrene (PS). By changing the material, the rigidity and weight can be adapted to the needs of the plastic component.

[0019] If greater stiffness is required, or if the part must have greater mass due to noise vibration harshness requirements, or if the plastic component has electrical, magnetic or other functionality that requires greater weight, the insert may comprise a dense, heavy material, such as a non-foamed polymer or metal.

[0020] Suitable materials for the insert include any material capable of forming an insert that essentially maintains its shape when a polymer melt is dispensed into the mold. Such materials may be, for example, polymeric materials such as thermoplastics or thermosets, ceramics, or metals. Particularly preferably, the insert is made of a polymeric material.

[0021] If the insert is made of a polymer material, preferably a polymer material is used that forms a uniform connection with the polymer dispensed into the gap between the insert and the mold wall, where a uniform connection in this context means that the insert and the hollow body surrounding the insert are in contact over the entire surface, in particular that the polymer melt dispensed into the gap between the mold and the insert melts and welds to the outer surface of the insert, forming an inseparable form-fit connection between the insert and the hollow body.

[0022] Furthermore, to achieve a stable insert, it may be advantageous to reinforce the insert. When a polymer material is used to manufacture the insert, the polymer material may be reinforced by adding short or long fibers or powdered reinforcing materials such as talc. Furthermore, continuous fibers can also be used to reinforce the insert. Whether short, long, or continuous fibers are used to reinforce the insert, the fibers may be glass fibers, carbon fibers, aramid fibers, or natural fibers such as hemp or wool. When the insert is made of foam and continuous fibers are used to reinforce the insert, all known techniques for connecting the foam and fibers can be used, such as over-foaming the fibers or placing pre-fabricated fiber sections in / on the foam to create the desired load path.

[0023] It is particularly preferred to use the same polymer to form the insert and the hollow body, in order to enable the plastic components produced by the process of the present invention to be recycled without complex separation steps to separate the different materials used to form the plastic components.

[0024] Suitable polymers for forming the insert and / or hollow body of the plastic component are preferably polyamide (PA), polyethylene (PE), polybutylene terephthalate (PBT), polyester, polyoxymethylene (POM), or polypropylene (PP). Due to the high compressive strength of polyamide foam, polyamide-based materials are preferred, as they can be reinforced. Therefore, if the polymer forming the hollow body is, for example, polypropylene, the insert is preferably made of polypropylene or foamed propylene. If polyamide is used as the polymer for the hollow body, the insert is also made of a polymer, particularly the same type of polymer as the hollow body.

[0025] In addition to the insert material, it is also possible to use a reinforcing polymer to form the hollow body. In this case, the polymer melt may contain short or long fiber or powder reinforcing material to form the hollow body. The material, fiber, or powder material may be any material known to those skilled in the art as a fiber or powder reinforcing material, preferably the materials described above for the insert are used.

[0026] The polymeric materials for producing the inserts and the hollow bodies may contain, in addition to the reinforcing materials, additives that are commonly used in polymeric materials, such as plasticizers, impact modifiers, dyes, or any other type of additive known to those skilled in the art.

[0027] It is possible to use polymers as inserts, especially foams or second hollow bodies, because under mechanical load the highest stresses are usually located in the outer region of the hollow body surrounding the insert, so there are no high stresses acting on the insert, and therefore the insert can be made from a material with lower mechanical properties.

[0028] To manufacture a plastic component, the first step involves placing an insert into a mold. The insert is placed in the mold so that a gap is formed between the mold's inner wall and the insert. This gap defines a cavity for the filling process, thereby forming a hollow body. According to the present invention, to form the gap, a protrusion is formed on the insert, or the mold is provided with a pin onto which the insert is placed.

[0029] If the ridges are formed on the insert, they may be integrally formed on the insert or may be separate components connected to the insert.

[0030] The ridges integrally formed on the insert are preferably formed while the insert is being formed. If the insert is made of foam, the ridges are also typically made of foam. If the insert is a second hollow body, the ridges are formed on the outer surface of the second hollow body, typically during part formation, to form the second hollow body. If the part for forming the second hollow body is formed by injection molding, a mold for manufacturing the part for the second hollow body is provided with recesses where the ridges should be.

[0031] Inserts made of foam can be manufactured by cutting the insert from the foam or by forming the foam insert in a mold. If the foam insert is formed in a mold, recesses are also provided where the ridges will be. During the formation of the foam insert, the ridges are also formed and made from the foam. Also, if the insert is cut from foamed raw material, the ridges may be formed on or made from the foam.

[0032] If the ridges are separate components, they may be connected to the insert by any suitable method known to those skilled in the art. For example, the ridges may be glued to the insert using an adhesive or may be welded to the insert. Furthermore, to connect the ridges to the insert, they may be partially enclosed by the insert. To partially enclose the ridges from the insert, it is preferable to form the insert by placing the ridges in a mold and then injecting a foam insert-forming material or a polymer melt to form a portion of the second hollow body.

[0033] Furthermore, if the ridges are separate components, they may be made of a different material or the same material from which the insert is made. However, if the insert and the hollow body forming the plastic component are made of different materials, it is particularly preferred to make the ridges from the same material from which the hollow body of the plastic component is made.

[0034] The raised portion may have any suitable shape, for example, a conical or cylindrical shape. In addition to a conical or cylindrical shape, any other shape may also be possible. Preferably, the raised portion has a conical shape and is connected to the insert or a portion of the insert such that the tip of the raised portion contacts the mold when the insert is placed in the mold. Such a conical shape is particularly preferred when the raised portion is formed from a material different from the polymer from which the hollow body is formed, or is formed from a foam. The conical shape and orientation of the conical raised portion so that the tip of the raised portion contacts the mold minimizes surface contact with the mold, and the raised portion remains invisible in the plastic part after demolding.

[0035] If the ridges are made of a solid material and are made of the same polymer as the hollow body of the plastic component, they usually remain invisible even if they have a different shape, e.g., a cylindrical shape, and a larger contact area with the surface of the mold. By using the same material, at least the surface of the ridges melts during the polymer melt feeding, and the polymer melt forms an integral connection with the ridges.

[0036] Alternatively, the side facing away from the insert may be provided with a raised portion having a convex curved surface to minimize the contact area with the surface of the mold.

[0037] However, particularly preferably, the ridge has a conical shape.

[0038] If the mold is provided with pins to form a gap between the inner surface of the mold and the insert, the pins may be fixed or retractable. Preferably, the pins are retractable to achieve a closed hollow body surrounding the insert without openings after deforming the plastic component. More preferably, the pins are continuously retracted when the polymer reaches them during feeding to avoid displacement of the insert during feeding of the mold.

[0039] Since the insert remains in the plastic component produced by the process of the present invention, it forms part of the mold during the feeding of the polymer melt to form the hollow body. This has the advantage that the inner surface of the hollow body can have any possible shape. The insert may, for example, be provided with a structured surface.

[0040] To form a structured surface, the insert may, for example, include recesses such that the polymer melt fills the recesses during dispensing. As the insert remains within the plastic component, it is even possible to form protrusions with undercuts on the inner surface of the hollow body of the plastic component.

[0041] The surface structure may have peaks and valleys smaller than the average wall thickness of the hollow body. Such a surface structure may help to define better load transfer between the rigid polymer material of the hollow body and the insert. Furthermore, surface micro-processing, such as a small texture or plasma treatment, may be advantageous because it allows for better connection of the insert to the hollow body.

[0042] In addition to small protrusions and recesses, in a preferred embodiment, recesses are formed, for example, on the inner surface of the hollow body, forming reinforcing ribs. Such protrusions, like reinforcing ribs, allow the hollow body to be reinforced without modifying its outer surface. This allows the provision of reinforcing ribs even when the surface of the hollow body is smooth.

[0043] Furthermore, for reinforcement purposes, it may be appropriate to form connecting bars connecting opposing inner surfaces of the hollow body. To this end, openings are formed in the insert, which are filled with the polymer melt during the feeding process, thereby forming connecting bars between the opposing inner surfaces of the hollow body. In this case, the core design creates defined cavities for the polymer melt. After the filling process, these cavities act as clearly defined load paths within the plastic component, improving its mechanical behavior.

[0044] After the insert is placed in the mold, the mold is closed and the polymer melt is fed into the mold. Any suitable process known to those skilled in the art can be used to feed the polymer melt into the mold. The polymer melt may be fed, for example, by an injection molding process. In this case, the mold into which the insert is placed before feeding the polymer melt is the mold of an injection molding machine. In addition to feeding the polymer melt using the injection molding process, the polymer melt can also be fed into the mold using a casting process or a centrifugal casting process. In these cases, the mold is the mold of a casting machine or a centrifugal casting machine, respectively. However, preferably, the injection molding process is used to feed the polymer melt into the mold.

[0045] To produce long plastic components, particularly long, closed profiles that can be used for bending loads or axial crash scenarios, polymer melt can be injected into a mold using sequential gating. In this case, an insert is placed in the mold so that a gap is formed between the mold and the insert. The polymer melt is then sequentially injected into the mold by opening a first gate, closing the first gate, and after a predetermined amount of polymer melt has been injected into the mold, opening a second gate and continuing to inject the polymer melt through the second gate. After the predetermined amount of polymer melt has been injected, the second gate is closed and additional gates are opened. This operation continues until the polymer melt has been injected into the mold sequentially through all gates. A good way to control gate opening is to open each gate immediately after it reaches its position in the mold and simultaneously close the previous gate. This method of feeding the polymer melt into the mold allows the polymer to be injected into the mold at a much lower injection pressure than would be required if the polymer melt were injected into the mold through only one injection point. Because the injection pressure is low, the mold clamping pressure can also be reduced, making it possible to produce very long profiles without the need for large machines with high clamping pressures and powerful injection units.

[0046] After dispensing the polymer melt into the mold, the polymer solidifies within the mold and the plastic component is subsequently removed from the mold.

[0047] Components that can be produced by the process of the present invention can be any part with thicker regions, where inserts can be placed to reduce the risk of internal void accumulation and provide uniform wall thickness, or hollow parts can be filled with foam inserts, so that the part can be produced by a less complex process. Additionally, the use of foam as an insert can improve the dynamic behavior of the plastic component, thus improving the dynamic response for better acoustic and noise-vibration harshness behavior.

[0048] The plastic components produced by the process of the present invention may be, for example, electric motors or other parts such as combustion engines, support structures for rotating machines, structural parts used to fasten or support structurally mechanically loaded parts, in particular parts that may be damaged by impact, for example in vehicles, or parts in which other parts are embedded. Such plastic components are, for example, roof rails, door handles, pedals, chairs, in particular highway stones, bicycle frames, seat frames or protective undercoatings for wheel rims.

[0049] Generally, injection-molded plastic components used as structurally mechanically loaded components are made of fiber-reinforced polymers and exhibit complex shapes resulting from the high loads and required design.

[0050] It is often not possible to locate the injection point at the ideal location in the mold for an optimal filling process, i.e., a location where balanced filling and undisturbed fiber orientation can be achieved to take advantage of anisotropic material behavior and reduced warpage of the plastic component. For optimal filling of the cavity, inserts are used that contain recesses that act as channels and connect the injection point with the optimal filling point for filling the cavity, improving the quality and mechanical behavior of the plastic component.

[0051] Components used to fasten or support other parts have dynamic natural frequency behavior that depends on the component's geometry, material, and mechanical boundary conditions. If the natural frequency of a component is close to a critical frequency of the main structure, such as an electric motor or combustion engine, this effect can lead to undesirable resonance effects. If the damping contribution of the component within the resonant frequency is not high enough, the vibrations can result in part damage or undesirable airborne noise and poor acoustic behavior.

[0052] Overmolding foam as an insert enables new designs of plastic components where resonance and damping behavior can be actively controlled through the material, geometry, and placement of the foam insert. This approach of overmolding a tailored foam insert allows for intelligent modification of dynamic behavior to actively control and improve dynamic response within a system.

[0053] The advantage of surrounding the foam insert with polymer is that the injection-molded polymer is placed in the outer shell of the available space, where loads are transferred much more efficiently. There is no need to design complex geometries that would displace metal tool sections or compromise performance due to the required release direction in the injection mold.

[0054] This effect becomes apparent when torsional loads must be transmitted. Closed cross sections in torsion are always advantageous compared to open cross sections. Open cross sections generally must be used in standard injection molding due to demolding. Closed cross sections can easily be used when designing components with overmolded foam inserts.

[0055] Plastic components that define the visible skin of an assembly may have requirements regarding crash, impact scenarios, or misuse. Drop testing of domestic machinery is an example of such a requirement.

[0056] Depending on the material selected for the cover, a crash scenario could result in brittle failure of the outer skin, with debris being generated by the spallation of the failure. Many failed particles can break down and seep into the environment, potentially causing undesirable behavior.

[0057] The use of inserts can change the type of failure. On the one hand, foam inserts distribute energy more evenly within the component, thus reducing local stresses. On the other hand, the tight connection established between the foam insert and the polymer melt prevents the part from breaking down into numerous small particles.

[0058] If the plastic component needs to be connected to other parts and / or other parts need to be incorporated into the injection molded part, the additional parts can be incorporated by including them in an insert before or after overmolding. The parts may be incorporated by any known connection technique, e.g., gluing, screwing, snapping, etc. Parts that are incorporated into the plastic component are, for example, sensors, electrical devices, electronic circuit boards, metal reinforcements, threaded and / or non-threaded inserts.

[0059] To incorporate the add-on, the insert may include a cavity into which the part to be incorporated into the plastic component is placed. After the add-on is placed in the cavity, the opening in the foam may be closed and then overmolded with a polymer melt. In this case, the add-on is safe and secure within the insert and will not be damaged by the polymer melt.

[0060] Possible connections to the outside of additional parts, for example electrical cables, may also be incorporated by the defined boundary between the foam insert and the polymer melt.

[0061] If additional parts must be incorporated into a plastic component because they are too soft to withstand the filling pressure of the polymer melt during the injection molding process without significant deformation, these parts can be incorporated into a foam insert and fixed relative to each other to prevent relative deformation during the injection molding process. Such soft additional parts can be, for example, wires and rods used as electrical conductors. Deformation during the injection process that causes them to come into contact with each other can result in an electrical short circuit. In this case, the component will not function and will be useless. If the additional parts are used as mechanical structures, deformation means that the desired mechanical function will at least be weakened or destroyed. By incorporating the additional parts into the plastic component insert, the component will still have the same external shape, but the tendency for core shift during the filling process will be minimized.

[0062] To incorporate the additional portions into the foam, the additional portions may be placed in a foam tool before the foaming process begins, thereby embedding them into the foam insert. Alternatively, the foam insert may be manufactured separately, and the additional portions may be incorporated into the foam insert after the foaming process.

[0063] Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. [Brief explanation of the drawings]

[0064] [Figure 1] FIG. 1 shows a plastic component manufactured by the GAIM / WIT process according to the state of the art. [Figure 2] FIG. 2 shows a plastic component produced by the process of the present invention. [Figure 3] FIG. 3 shows a plastic component with a ridge on an insert having a conical shape. [Figure 4] FIG. 4 shows a plastic component with a protuberance on an insert having a conical shape in a second embodiment. [Figure 5]FIG. 5 shows a plastic component having a ridge on an insert in the form of a cylindrical pin. [Figure 6] FIG. 6 shows diagrammatically the fixation of the insert by means of a retractable pin. [Figure 7] FIG. 7 shows a plastic component having an insert with a structured surface. [Figure 8] FIG. 8 shows an insert having recesses and openings to form additional cavities that are filled. [Figure 9] FIG. 9 shows an insert in the form of a hollow body. [Figure 10a] FIG. 10a shows an insert with recesses as channels. [Figure 10b] Figure 10b shows the plastic part injected into the insert of Figure 10a. [Figure 11] FIG. 11 shows a bracket with a foam insert to improve noise vibration harshness. [Figure 12] FIG. 12 shows an engine mount for an electric engine. [Figure 13] FIG. 13 shows an engine mount for a combustion engine. [Figure 14] FIG. 14 shows a plastic component with a foam insert to avoid decomposition in a crash scenario. [Figure 15] FIG. 15 shows a plastic component having an insert with a cavity for incorporating an add-on part. [Figure 16] FIG. 16 shows an insert incorporating a soft section. [Figure 17] FIG. 17 shows a plastic component having inserts incorporating different materials.

[0065] In the figures, exemplary plastic components are shown for demonstration purposes. Plastic components produced by the process of the present invention can have any geometric shape that can be produced by injection molding or casting methods, and can have more or fewer sections with different wall thicknesses, for example, as shown herein. Plastic components produced with the process of the present invention can have simple geometric shapes, such as, for example, cylinders, cones, or spheres, or can have any other geometric shape. Furthermore, plastic components can have much more complex structures, as shown here.

[0066] FIG. 1 shows an exemplary plastic component manufactured by the GAIM / WIT process according to the state of the art.

[0067] The plastic component 1 comprises several sections with different thicknesses: a first section 3 has a small wall thickness, a second section 5 has a medium wall thickness and a third section 7 has a large wall thickness. To avoid material buildup in the second section 5 and the third section 7, the plastic component comprises a cavity 9 surrounded by polymer material forming a hollow body 11.

[0068] According to the state of the art, the cavity 9 is formed by injecting a gas or liquid after the polymer melt has filled the mold, which then displaces the polymer melt, forming the cavity 9. This process avoids material buildup and produces a hollow body 11.

[0069] However, due to this process, variations in the wall thickness and uneven wall of the hollow body cannot be avoided. Further slight variations in the pressure or velocity of the gas or liquid used to remove the polymer melt can result in differences in the geometry of the hollow body.

[0070] To avoid these drawbacks, the process of the present invention produces a plastic component that includes an insert surrounded by a hollow body, an example of which is shown in Figure 2.

[0071] The plastic component 1 of Figure 2 has the same external shape as the plastic component 1 shown in Figure 1. However, unlike the plastic component 1 produced by the process according to the state of the art, the plastic component 1 produced by the process of the invention comprises an insert 13 which completely fills the cavity 9 of the hollow body 11.

[0072] By using the insert 13, the hollow body 11 can be produced with a defined wall thickness and unintentional different wall thicknesses can be avoided. The insert 13 can be, for example, a foam or a second hollow body which can be made of metal, ceramic or optionally reinforced polymer.

[0073] To manufacture the plastic component 1, the insert 13 is placed in the mold, thereby forming a gap between the insert 13 and the inner wall of the mold. A polymer melt is then fed into the gap to form the hollow body 11.

[0074] To form the gap, it is possible to provide a ridge on the insert or to use a pin in the mold into which the insert is placed.

[0075] 3-5 show different embodiments of the ridges on the insert.

[0076] A plastic component having a cone-shaped protuberance on the insert is shown in FIG.

[0077] To achieve a hollow body 11 with the desired wall thickness, it is necessary to provide a mold into which the polymer melt is fed, the mold having a cavity corresponding to the desired shape of the hollow body. According to the process of the present invention, the cavity is bounded by the inner wall of the mold and the surface 15 of the insert 13. Because the surface 15 of the insert is opposite the inner wall of the mold, the cavity into which the polymer melt flows to form the hollow body 11 has the form of a gap. The distance between the surface 15 of the insert 13 and the inner wall of the mold, and therefore the wall thickness of the hollow body 11, is defined by a ridge 17 on the insert 13.

[0078] When the insert is placed in the mold, the ridges 17 contact the inner wall of the mold, with the insert 13 abutting against the ridges 17 on the inner wall of the mold, thereby forming a gap through which the polymer melt can flow to form the hollow body 11.

[0079] In the embodiment shown in Figure 3, the ridges are arranged on the surface 15 of the insert 13. This can be achieved by providing ridges and connecting them to the surface 15 of the insert, for example by gluing or welding. In this case, the ridges 17 may be made of the same material as the insert 13, or may be made of a different material that can be fixed to the surface 15 of the insert 13. If the insert 13 and the hollow body 11 are made of different materials and the ridges are made of a material different from the material from which the insert is made, it is particularly preferred that the ridges 17 are made of the same material as the hollow body 11. If the insert 13 and the hollow body 11 are made of the same material, it is also preferred that the ridges 17 are made of the same material.

[0080] In addition to manufacturing the ridges 17 separately from the insert 13 and securing them to the surface 15 of the insert 13, it is also possible and preferred to manufacture the ridges 17 integrally with the insert 13.

[0081] In particular, when the ridges 17 and the hollow body 11 are made of different materials or when the ridges 17 are made integrally with the insert 13, a conical shape of the ridges 17 as shown in Figure 3 is preferred to minimize the contact area of ​​the ridges 17 on the inner wall of the mold. This is particularly preferred when the ridges 17 are made integrally with the insert 13 and the insert is foam, since in this case the ridges 17 are also made of foam.

[0082] An alternative configuration for securing the ridge 17 to the insert 13 is shown in FIG.

[0083] The ridges shown in Figure 4 also have a conical shape. However, unlike the embodiment shown in Figure 3, the ridges 17 shown in Figure 4 are not fixed to the surface 15 of the insert 13, but are instead partially surrounded by the material of the insert 13. This design of the insert 13 has the advantage that no adhesive or additional steps are required to secure the ridges 17 to the insert 13, for example by welding, on the surface 15 of the insert 13.

[0084] Such a design of the insert 13 with a partially enclosed ridge 17 is particularly preferred when the ridge 17 is made of a solid material and the insert 13 is made of a foam. In this case too, the ridge 17 is preferably made of the same material as the hollow body 11.

[0085] To manufacture an insert 13 having a partially enclosed ridge 17, for example, the ridge 17 is placed in a mold for manufacturing the insert 13, and then material for forming the insert 13 is supplied into the mold.

[0086] A further alternative for the ridge 17 to be at least partially surrounded from the material of the insert 13 is shown in FIG.

[0087] The embodiment shown in Figure 5 differs from the embodiment shown in Figure 4 only in the shape of the raised portion 17. The difference from the embodiment of Figure 4 is that the raised portion 17 in the embodiment shown in Figure 5 has a cylindrical shape.

[0088] In addition to the cylindrical shape of the ridges 17 shown in FIG. 5 or the conical shape of the ridges 17 shown in FIG. 3 or FIG. 4, the ridges 17 may have any other shape, for example a pyramid, a sphere or hemisphere, or a cube.

[0089] Instead of the raised portion 17 for forming a gap through which the polymer melt flows to form the hollow body 11, as shown in Figures 3 to 5, it may be used to form a gap pin in the mold. This is exemplarily shown in Figure 6.

[0090] For illustrative purposes, FIG. 6 shows a section of a mold, which includes a first portion 19 and a second portion 21. To form the hollow body 11 of the plastic component 1, the first portion 19 and the second portion 21 are closed, thereby forming the mold. Each portion 19, 21 of the mold includes an opening 23 into which a pin 25 is received. The pin 25 may be fixed or, preferably, retractable. If the pin is retractable, the mold is opened and the pin 25 is moved to a first position in which it protrudes into the mold to place the insert 13 into the mold. The length the pin protrudes into the mold corresponds to the width of the gap through which the polymer melt is injected to form the hollow body. The insert 13 is then placed on the pin, and the mold is closed. Alternatively, the insert can be placed on the inner surface of the first portion 19 or the second portion 21, the mold can be closed, and the pin 25 can then be moved to the protruding position to form the gap.

[0091] To form the hollow body, it is possible to leave the pins 25 in the extended position while feeding the polymer melt. However, this has the disadvantage that the hollow body will have a hole after being removed from the mold. Therefore, it is preferable to use retractable pins 25, which are continuously retracted into their openings 23 as the polymer melt reaches each pin 25 during filling of the mold. By continuously retracting the pins 25 while filling the gap, the gap upstream of the melt front is filled with polymer melt, and therefore the insert 13 remains in place.

[0092] FIG. 7 shows a plastic component having an insert with a structured surface.

[0093] In addition to a smooth surface, as shown in Figures 2-6, the surface 15 of the insert 13 may have a structure 27. Depending on the intended function of the structure 27, the insert 13 may have a structure 27 with small or large surface variations. Small surface variations mean that the distance between the highest point of the convex portion and the lowest point of the concave portion of the structure is less than half the average wall thickness of the hollow body. Small surface variations can help ensure better load transfer between the material of the hollow body 11 and the material of the insert 13, for example. Furthermore, particularly when torsional loads act on plastic components, small surface variations better connect the insert 13 to the hollow body 11. Therefore, the insert 13 does not slide inside the hollow body 11 when torsional loads act on the plastic component, but the relative positions of the contact surfaces of the insert 13 and the hollow body 11 remain constant.

[0094] The structures 27 may have any suitable geometric shape, for example, wavy, zigzag, triangular, or grooved. Furthermore, the surface may have ridges of any possible shape, for example, pyramidal, conical, hemispherical, cylindrical, or any other shape.

[0095] In addition to small surface variations, the structure may also have large surface variations, meaning that the distance between the lowest point of the recess and the highest point of the protrusion is greater than half the average wall thickness or hollow body. Such large surface variations may comprise, for example, reinforcing ribs. In addition to structures with small or large surface variations, a combination of small and large surface variations is also possible.

[0096] An example of an insert with a structure having large surface variations is shown in FIG.

[0097] The insert 13 includes recesses 29 and holes 31. When filling the gap with a polymer melt to form the hollow body, the polymer melt flows into the recesses 29 and holes 31. After hardening, the polymer filled into the recesses 29 forms ribs on the inner surface of the hollow body. The polymer filled into the holes 31 forms a connection between two opposing inner surfaces of the hollow body, thereby reinforcing the polymer component.

[0098] In addition to the recesses 29 and holes 31 shown herein, the insert 13 may also include only at least one hole 31 or only one recess 29 for forming a reinforcing rib on the inner surface of the hollow body 11. Therefore, the geometric shape of the recess depends on the intended form of the reinforcing rib. In addition to intersecting grooves as shown here as recesses 29, the recesses 29 may also be parallel grooves of any shape. Furthermore, the recesses 29 may be provided not only in the thickest portion 33 of the insert 13 as shown here, but also in additional surfaces, such as the inclined surface 35 connecting the thinner portion 37 to the thickest portion 33 and / or the thinner portion 37. Furthermore, the recesses 29 may be provided in any other surface of the insert 13.

[0099] The optimal location and shape of the recesses depends on the intended shape of the reinforcing rib for optimal mechanical performance and can be determined by simulation calculations. The same applies to the holes 31 through which the polymer melt flows to form a connection between the two inner surfaces of the hollow body.

[0100] The holes 31 may have any cross-sectional area, such as a circle as shown here. However, besides a circle, the cross-sectional area may be, for example, oval, square, triangular, cross-shaped, or have any polygonal form. The cross-sectional area of ​​the holes may also be constant or may vary over the entire length of the holes 31. For example, the cross-sectional area may decrease or increase, or may first decrease and then increase, or first increase and then decrease. Additionally, the holes 31 may vary in cross-sectional area shape along their length.

[0101] The insert 13 shown in Figures 2 to 8 is preferably made of foam. Alternatively, the insert 13 may also be a second hollow body. This is shown for example in Figure 9.

[0102] When the insert 13 is a second hollow body, it is preferred that the insert 13 comprises at least a first portion 39 and a second portion 41, the first portion 39 and the second portion 41 being connected to form the insert 13. However, other than only the two portions 39, 41 as shown here, depending on the shape of the insert 13, the insert 13 may also consist of two or more portions.

[0103] For a stable connection of the parts 39, 41 forming the insert, it is preferred that the connecting edges 43 of the parts 39, 41 be structured, for example, by having a tongue and groove, as shown here. When the parts are connected, the tongue slides into the groove, so that they cannot move relative to each other. As an alternative to the tongue and groove as shown here, it is also possible to provide each of the connecting edges with a protrusion, one part on the outer surface and the other part on the inner surface, so that the part with the protrusion on the inner surface can slide into the part with the protrusion on the outer surface, thus forming a stable connection.

[0104] Additionally, the portions may be secured together, for example by gluing or welding.

[0105] In order to reinforce the insert 13 forming the second hollow body, it is possible to provide pillars or walls 45 connecting the two opposing inner surfaces of the hollow body, whereby the pillars and / or walls can be manufactured in one part of the insert 13 or partially in two parts, with the contacting parts of the partially formed pillars and / or walls forming the inner connecting pillars or walls of the second hollow body, as shown here.

[0106] As an alternative to, or in addition to, walls or pillars connecting two opposing sides, reinforcing ribs may be formed on part of or the entire inner surface of the second hollow body.

[0107] FIG. 10a shows an example of an insert 13 having a recess 47 as a flow path. The recess 47 connects an injection point 49, through which the polymer melt is injected into the mold, with a distribution point for distributing the polymer melt into a cavity 51 in the insert 13. The injection point 49 is located in an easily positionable position within the mold, and the distribution point for distributing the polymer melt is located in a position that allows optimal filling of the cavity 51, i.e., balanced filling, reduced warpage of the plastic component 1, and, if the polymer melt contains fibers, undisturbed fiber orientation for achieving anisotropic material behavior. Furthermore, by locating the easily positionable injection point and distribution point in a position that allows optimal filling of the cavity, improvements in the quality and mechanical behavior of the resulting plastic component are achieved.

[0108] Figure 10b shows the plastic part after the polymer melt has been injected into the cavity of the insert 13 of Figure 10a. The plastic part comprises a sprue 53 at the injection point 49, a bar 54 formed in the flow path connecting the injection point 49 with a dispensing point 55, and a rib 57 formed in the cavity 51 of the insert.

[0109] FIG. 11 is a schematic diagram of a bracket with a foam insert for improving noise vibration harshness.

[0110] The noise vibration harshness improved bracket 59 may comprise a first bracket portion 61 and a second bracket portion 63. The insert 13 may be disposed between the first bracket portion 61 and the second bracket portion 63 and further surrounded by a connecting portion 65 connecting the first bracket portion 61 and the second bracket portion 63. Due to its location, geometry and material, the insert 13 effectively changes the dynamic behavior of the bracket 59, thus improving the dynamic response for better acoustics and noise vibration harshness.

[0111] The insert 13 may completely or partially fill the cavity 9 between the first bracket portion 61 and the second bracket portion 63. If the insert 13 only partially fills the cavity 9, it is possible to position the insert 13 in the mold by means of a ridge on the insert 13 or a pin in the mold, for example, and fill the remaining hollow portion with the respective portion of the mold while injecting the polymer melt for the first and second bracket portions 61, 63.

[0112] Depending on the vibration, it may be advantageous to use inserts 13 to position them in different directions according to a given primary load in shear, tension and / or compression. The inserts 13 themselves, preferably made from polymer foam, may be the primary component through which energy is dissipated, or may act as a modifier or enabler so that the rest of the entire plastic component behaves in a desired way.

[0113] An example of a plastic component with improved noise vibration harshness that can be produced with the process of the present invention is an engine mount for an electric or combustion engine, as exemplarily shown in Figures 12 and 13.

[0114] The engine mount 67 for an electric engine provides a space for accommodating an electric motor. To dampen vibrations, the engine mount 67 has a cavity 9 filled with a foam insert 13. Filling the cavity 9 with the insert 13 has the added advantage of allowing the engine mount 67 to be designed with an essentially constant wall thickness. Furthermore, a large amount of plastic forms the outer skin of the engine mount 67, thus transferring loads much more efficiently. Due to the required release direction in injection molding, there is no need to design complex geometries that would shift metal tool sections or compromise performance.

[0115] This effect becomes apparent when torsional loads must be transmitted. Closed cross sections for torsion are always advantageous compared to open cross sections. Open cross sections usually have to be used in standard injection molding due to demolding. Closed cross sections can easily be used when designing parts using the manufacturing process of the present invention for overmolding inserts.

[0116] An engine mount 71 for a combustion engine, shown exemplarily in Fig. 13, comprises a cavity 9 which is filled with an insert 13 and which damps the vibrations of the combustion engine. Furthermore, for mounting the combustion engine, the engine mount 71 comprises a blind hole 73 incorporating a metal insert 75 for accommodating a fixing element of the combustion engine.

[0117] The process of the present invention also allows for the production of plastic components with foam inserts to avoid decomposition in a crash scenario, an example of such a plastic component is shown in cross section in Figure 14.

[0118] The component that will not break down in a crash scenario, reducing the number of small particles that enter the environment after a crash, generally forms the exterior wall and includes the visible portion of the component, such as outer portion 77, which may be the skin of a bumper. The insert 13 is secured to the inner surface 79 of outer portion 77 and is therefore invisible after installation. The tight connection between insert 13 and outer portion 77 holds the portions together in the event of an impact or collision. Additionally, insert 13, especially if made of foam, strengthens outer portion 77 in flexion, increasing overall strength.

[0119] The use of an insert 13 surrounded by a hollow body 11 has the additional advantage that additional parts can be incorporated into the plastic component 1. For this purpose, a cavity 81 is formed in the insert 13, as shown in Figure 16.

[0120] Additional parts not shown here are placed in cavity 81 of insert 13. Depending on the shape of the parts to be incorporated into insert 13, and therefore the shape of cavity 81, it may be necessary to use an insert made of several parts, which are assembled before being placed in a mold for overmolding with a polymer melt.

[0121] The part to be incorporated into cavity 81 may be, for example, a sensor, an electrical device, an electronic circuit board, a metal reinforcement, an insert with or without threads, or any other part known to those skilled in the art that can be incorporated into plastic component 1.

[0122] If the additional part is soft and may be deformed during the injection molding process, such as a wire or rod used as a conductor, the additional part can be fixed using an insert 13. An example of an insert 13 having a conductor 83 with a soft part embedded therein is shown in Figure 16.

[0123] The soft additional parts, such as the conductors 83, may be embedded in the foam of the insert by placing them in the tool for producing the foam insert before the tool is filled with the components that form the foam. Alternatively, it is also possible to first form the insert from the foam after the foaming process and then place the soft insert in the foam.

[0124] After the insert is finished with the additions, the insert 13 is placed in a mold and a polymer melt is injected into the gap between the insert 13 and the interior wall of the mold.

[0125] In addition to using hollow inserts 13, it is also possible to reduce the weight of the plastic component 1 by filling the cavity within the insert 13 with a lighter material, for example a foam having a lower density.

[0126] On the other hand, if a higher mass of plastic component 1 is required to improve noise vibration harshness, for example to provide greater rigidity, or if plastic component 1 has an electrical, magnetic, or other function, a denser, heavier material may be incorporated into insert 13. The material incorporated into insert 13 depends on the intended function and may be, for example, a conductive or magnetic material, such as a metal. Furthermore, to increase stability or weight, a polymer having a higher density than the material of the insert's foam may also be incorporated into insert 13, for example, over a non-foamed polymer.

[0127] An example of a plastic component 1 having an insert 13 with an additional different material 85 is shown in FIG.

Claims

1. A process for manufacturing a plastic component (1) comprising an insert (13) surrounded by a hollow body (11), said process comprising: (a) placing an insert (13) into a mold such that a gap is formed between the insert (13) and the mold; (b) feeding a polymer melt into said gap, thereby forming said hollow body (11) surrounding said insert (13); (c) removing the plastic component (1) from the mold; A process in which a ridge (17) is formed on the insert (13) to form the gap, or the mold comprises a pin (25) on which the insert is placed, or the gap is a recess in the insert (13).

2. 2. The process according to claim 1, wherein the insert (13) is made of foam or is a second hollow body.

3. 3. The process of claim 2, wherein the second hollow body comprises columns or walls (45) connecting opposing interior walls of the second hollow body to reinforce the second hollow body.

4. 4. The process according to any one of claims 1 to 3, wherein the insert (13) is made of metal, ceramic or polymer.

5. 4. The process according to any one of claims 1 to 3, wherein the insert (13) is made of a polymer material that forms a uniform connection with the polymer dispensed into the gap.

6. 6. The process according to any one of claims 1 to 5, wherein the polymer from which the insert (13) is made and from which the hollow body (11) is made is polyamide, polyethylene or polypropylene.

7. 7. The process according to any one of claims 1 to 6, wherein the polymer inserted in the gap is the same polymer from which the insert (13) is made.

8. 8. The process according to any one of claims 1 to 7, wherein the ridges (17) are made from the same material as the inserts (13).

9. 9. The process according to any one of claims 1 to 8, wherein the ridge (17) is integrally formed on the insert (13).

10. 8. The process according to any one of claims 1 to 7, wherein the ridge (17) is a separate component and is connected to the insert (13).

11. 11. The process according to any one of claims 1 to 10, wherein the ridge (17) has a conical shape and is connected to the insert (13) such that when the insert is placed in the mold, the tip of the ridge (17) contacts the mold.

12. 8. The process according to any one of claims 1 to 7, wherein the pins (25) of the mould are retractable, and the pins (25) are preferably continuously retracted as the polymer melt reaches them during feeding of the polymer melt.

13. 13. The process according to any one of claims 1 to 12, wherein the insert (13) has a structured surface (27).

14. 14. The process according to any one of claims 1 to 13, wherein the surface of the insert (13) is provided with recesses (29) so that during the supply of the polymer melt, the polymer melt fills the recesses (29), and the recesses (29) preferably have a form such that reinforcing ribs are formed on the inner surface of the hollow body (11).

15. 15. The process according to any one of claims 1 to 14, wherein openings (31) are formed in the insert (13) which are filled with the polymer melt during the feeding step, thereby forming a connecting bar between two opposing inner surfaces of the hollow body (11).

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