Method for manufacturing a decorative part

Abstract

Method for producing a decorative part (1) comprising the process steps in the following order: a. Inserting and fixing a decorative element (3) in a tool, b. Applying a liquid plastic layer (2) over the entire surface of the decorative element (3), c. Stiffening of the decorative element (3) by hardening the plastic layer (2), and subsequent d. Applying a support structure (4) to the solidified plastic layer (2) of the stiffened decorative element (3), wherein the application of the support structure (4) is carried out in a process-integrated manner in the same tool, wherein the support structure (4) integrally comprises a multitude of connecting elements (5) and stiffening elements.

Description

[0001] The invention relates to a method for manufacturing a decorative part consisting of a decorative element and a support structure applied directly to a solidified plastic layer of the stiffened decorative element.

[0002] The demands placed on decorative parts have steadily increased in recent years. Particularly in the automotive sector, they no longer serve merely as functional surface coverings, but, especially in the premium segment, must meet the highest optical, tactile, and mechanical quality standards. Such optical and tactile requirements include, for example, gloss, transparency of the visible area, and a homogeneous, casting-free surface of the component. In terms of mechanical, physical, and chemical properties, high abrasion and scratch resistance, sufficient impact strength, and adequate resistance to outgassing and aging effects, such as discoloration, must be ensured.

[0003] In addition to the high quality requirements for the product itself, a process-optimized workflow is particularly necessary, in which, besides reducing production time and manufacturing costs, an increase in the degree of automation and the guarantee of process security must also be achieved.

[0004] In the prior art, three main processes have been used to manufacture trim and decorative parts: lamination, injection molding, and die casting. The present invention relates to a new process sequence for injection molding, since lamination and die casting are too inefficient for high-volume production with a high degree of automation.

[0005] From DE 10 2004 035 759 A1 a method for producing a decorative molded part is known in which the decorative material is overmolded separately from both sides, and after overmolding a first side, it remains between the closed mold halves of the injection mold.

[0006] EP 1 716 993 B1 discloses a method for producing a veneered molded part in which the final contour of the molded part is realized by a pressing process and force introduction points are subsequently formed by injection molding.

[0007] DE 199 14 092 C2 teaches a method and a device for manufacturing a cladding and decorative part, in which a decorative element is placed in an injection mold and injection molding compound is supplied by means of a sprue funnel, so that the decorative element is completely enclosed by the injection molding compound within the injection mold.

[0008] A disadvantage of the methods described above is that either the decorative element is not directly equipped with the necessary support structure, thus requiring additional production steps to complete the component, or a support structure applied directly to the decorative element can lead to sink marks or uneven warping of the entire component during cooling. Defects become visible on the surface of the decorative element after the plastic has solidified. Such sink marks arise particularly because the support structure has numerous connection and stiffening elements to ensure secure attachment to the vehicle. The varying cross-sections and the multitude of material accumulations within a structure cause precisely this inhomogeneous vibration behavior during cooling, resulting in negative effects on the visible side of the decorative element as well.

[0009] Further state of the art in this technical field is known, for example, from the disclosures in documents DE 10 2006 016 200 A1, EP 2 027 982 A1, US 2009 / 0174121 A1 and DE 10 2004 044 415 A1.

[0010] It is therefore the object of the present invention to provide a method by which decorative parts of the highest quality and without defects can be produced with a higher degree of automation compared to the prior art.

[0011] The problem according to the invention is solved by the method according to the features of claim 1. In this method, a decorative part is produced according to the invention in the following successive steps. First, a decorative element is placed in a mold and fixed therein in such a way that it cannot shift during the injection molding process. Then, a liquid plastic layer is applied over the entire surface of the decorative element to ensure complete surface coating. The plastic layer hardens and stiffens the decorative element in all directions. Finally, a support structure is applied to the plastic layer on the back of the stiffened decorative element.

[0012] In this context, the term "decorative part" refers to the entire component to be manufactured using this method. The term "decorative element" encompasses all components used on the visible side of the decorative part, such as wood veneer inlays. The term "support structure" refers to the structure located on the back of the decorative part, which is used to connect or fasten the decorative part at its point of use, such as the dashboard of a car.

[0013] Any material suitable for injection molding can be used as the plastic layer. For this application, plastics such as acrylic glass, polycarbonate, or styrene-acrylonitrile are commonly used. The processing temperature required to ensure a smooth, liquid application of the plastic varies depending on the specific plastic. For example, polycarbonate can be injected into a mold at temperatures between 280°C and 320°C under high pressure. Styrene-acrylonitrile is preferred in this case because it can be processed at significantly lower temperatures (220°C to 250°C) and exhibits excellent weather resistance.The requirements for the support structure differ from those of the plastic layer, so acrylonitrile butadiene styrene (ABS) is preferably used for the support structure. Optionally, but not necessarily, short and / or long fibers can be incorporated into the support structure to provide additional reinforcement. Processing two different plastics in a single injection mold allows the individual components to be adapted to the specific requirements of their respective applications. This means the support structure can withstand high holding forces without breaking, while the visible surface of the decorative element ensures superior surface quality and durability.

[0014] The application of the carrier structure to the plastic layer of the decorative element is integrated into the process in the same tool, whereby the decorative element always remains in a fixed state within the tool, even while the carrier structure is applied in the subsequent process step using injection molding technology.

[0015] The plastic layer surrounding the decorative element hardens after overmolding or flooding, giving the decorative element the necessary rigidity for subsequent processes. In contrast to previous methods, the support structure is only bonded after the surface of the decorative element has been sealed with the plastic layer. This prevents the decorative element from deforming during cooling due to stresses introduced by the overmolded support structure, as was the case in prior art methods. Instead, the decorative element retains its original shape without sink marks or defects.

[0016] In an advantageous embodiment, the decorative element can be overmolded or immersed in the appropriate plastic at its corresponding processing temperature. The surface structure resulting from this process requires no post-processing, so that no further processing steps are necessary after removal of the finished component, thus significantly reducing production time and manufacturing costs.

[0017] In a cost-effective design, a protective layer can be added to the styrene-acrylonitrile layer on the decorative element to prevent potential negative properties of the plastic layer (hygroscopy, yellowing) and to increase the wear resistance of the visible side of the decorative element. After the plastic layer has hardened, the protective layer is also applied to the visible side of the decorative element using injection molding, preferably with polyurethane.

[0018] In a preferred embodiment according to the invention, the plastic layer is made just thick enough to ensure the durability of the decorative part, while simultaneously minimizing manufacturing costs and production time, and in particular the time required for solidification and stiffening during cooling. The plastic layer has a thickness of 0.5 to 5 mm, preferably 0.5 to 3 mm, even more preferably 0.5 to 2 mm, and optimally 0.5 to 1.2 mm. The specified parameters refer to the finished product and can be verified, for example, by cutting open the decorative part and measuring the layer thickness with calipers.

[0019] Further advantages of the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the figures. The figures show: Fig. 1. a first procedural sequence; Fig. 2 a second procedure. Fig. 3 a perspective view of a decorative part produced by the first method;

[0020] The illustrations in the accompanying figures are schematic and exemplary. Identical components in each figure are labelled with the same reference numerals. Furthermore, only the elements essential for understanding the invention are shown.

[0021] In the Fig. 1 and Fig. Figure 2 illustrates the process sequences of the method according to the invention. According to a first process sequence according to Fig. 1. The decorative element is first placed into the mold, which is designed as an injection mold, and in the second process step is fixed in it so that it does not slip during the injection molding process. Subsequently, in the third process step, the decorative element is completely overmolded with plastic to create a fully enclosed plastic layer around it. According to the process according to Fig. In step 1, the plastic layer forms the outer layer, which can be used as the visible side of the decorative element without any further processing. In a fourth process step, the carrier component is directly injection-molded onto the back of the decorative element surrounded by the plastic layer, without requiring any changes to the decorative element's position in the mold. The plastic layer gives the decorative element increased rigidity, preventing surface distortion of the decorative element during the cooling process of the plastic carrier structure.

[0022] In contrast to the procedure according to Fig. 1 shows the procedure according to Fig. 2. An additional process step is added, namely that an additional protective layer is applied to the plastic layer after it has cooled. The protective layer can be applied only to the visible side of the decorative element or, like the plastic layer, completely around the decorative element. The use of a protective layer offers the advantage that a lightweight and quick-to-process plastic material can be used, which might not otherwise meet the surface requirements on the visible side of the decorative part. These requirements are then ensured by the additional protective layer, so that the entire decorative part can still meet the highest requirements with regard to surface quality (class A) and the stability of the substrate.

[0023] In Fig. Figure 3 shows a perspective view of a decorative part produced by the first method. Reference symbol list 1 decorative part 2 plastic layers 3 decorative elements 4 Support structure 5 connection elements

Claims

[1] Method for producing a decorative part (1) comprising the process steps in the following order: a. Inserting and fixing a decorative element (3) in a tool, b. Applying a liquid plastic layer (2) over the entire surface of the decorative element (3), c. Stiffening of the decorative element (3) by hardening the plastic layer (2), and subsequent d. Applying a support structure (4) to the solidified plastic layer (2) of the stiffened decorative element (3), wherein the application of the support structure (4) is carried out in a process-integrated manner in the same tool, wherein the support structure (4) integrally comprises a multitude of connecting elements (5) and stiffening elements. [2] Method for producing a decorative part (1) according to the preceding claim, characterized by , that the decorative element (3) is overmolded or flooded to apply the plastic layer (2). [3] Method for producing a decorative part (1) according to any one of the preceding claims, characterized by that the tool is designed as an indexable insert tool. [4] Method for producing a decorative part (1) according to any one of the preceding claims, characterized by , that in addition to the plastic layer (2) a protective layer is provided on a visible side of the decorative part (1). [5] Method for producing a decorative part (1) according to any one of the preceding claims, characterized by , that the application of the support structure (4) to the solidified plastic layer (2) of the decorative element (3) is injection molded. [6] Method for producing a decorative part (1) according to any one of the preceding claims, characterized by , that the stiffening plastic layer (2) has a thickness between 0.5 mm and 1.2 mm. [7] Method for producing a decorative part (1) according to any one of the preceding claims, characterized by, that the plastic layer (2) is made of acrylic glass (PMMA), polycarbonate (PC) or styrene-acrylonitrile (SAN). [8] Method for producing a decorative part (1) according to the preceding claim, characterized by , that the support structure (4) is made of acrylonitrile butadiene styrene (ABS). [9] Method for producing a decorative part (1) according to the preceding claim, characterized by , that the support structure (4) has short fibers and / or long fibers.

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