DE102015201898A1 - Method and device for producing an undercut molding - Google Patents

Abstract

The present invention relates to a method for producing a molded part for a motor vehicle, wherein the molded part (10) has at least one undercut and at least one surface structure without marking in the region of the at least one undercut, comprising the steps of: inserting an elastically deformable negative mold (20) into one Forming tool (30) which is designed to be movable in the region of the at least one undercut, introducing a reactive plastic (50) into the negative mold (20) to form a plastic foam layer (52) of the molded part, positioning a support structure (60) in the negative mold (20 ) at a defined distance from the negative mold (20) within a predetermined period of time after the introduction of the reactive plastic (50) into the female mold (20) and foaming of the reactive plastic (50), wherein the foaming reactive plastic (50) forms the support structure contacted to form the molding. The present invention further relates to an apparatus for carrying out the method according to the invention.

Description

The present invention relates to a method and an apparatus for producing a molded part for a motor vehicle with at least one undercut and with a surface structure which is free of marking at least in the region of the at least one undercut.

At molded parts of the interior trim (interior moldings) of motor vehicles, many demands are made today. For example, an instrument panel of a motor vehicle must first of all be designed to be so stable that destroying the instrument panel in extreme situations, such as in the event of an accident, for example, with the associated risk of injury to the vehicle occupants, is excluded. At the same time, the instrument panel must absorb energy in an impact of an object and in particular a body part of a vehicle occupant to minimize the risk of injury from the impact. Furthermore, high demands are placed on interior parts of motor vehicles in terms of their appearance and feel.

To meet these requirements, interior moldings such as instrument panels are nowadays regularly produced as multilayer molded parts (sandwich moldings), these often being produced in the so-called foam-back process. Here, an optical and haptic quality surface layer is introduced together with a carrier molding, which ensures the stability of the molding and the connection of the instrument panel to the interior of the motor vehicle, introduced into a mold and the gap between these two elements then foamed with a plastic. The surface layer is hereby regularly provided as a molded skin, d. h., This already has the surface geometry of the molded part to be produced.

Sprayed molded skins for interior moldings of motor vehicles can currently only be used because of process-related fluctuating wall thickness only for those moldings in which the molded skin is connected to the carrier molding by back-foaming. Through the foam backing the wall thickness variation of the skin is compensated. However, backfoaming is an additional process step, which increases the cost of manufacturing the molded part.

Another problem here is to produce such moldings with an undercut. After one in the EP 0 342 473 B1 It is known that a suitably deformed elastomer layer is applied to an elastic, prefabricated in a master mold and then dimensionally stable under deformation in a mold negative mold, which deformed after removal from the final space shape including an undercut of the molded part and in a split End tool is backfilled with the remaining molding material. The elastomer layer forms an integral, previously elastically deformed outer layer of the finished molded part. However, such a method leads to a relatively high manufacturing and tooling costs and requires an elastic deformation of the outer, non-marking layer of the molding.

It is therefore an object of the present invention to at least partially overcome the disadvantages described above. In particular, it is an object of the present invention to provide a method and a device by means of which a multilayer and undercut molded part, in particular an interior molding for a motor vehicle, can be produced more economically.

The above object is achieved by a method having the features of claim 1 and an apparatus having the features of claim 12. Further features and details of the invention will become apparent from the dependent claims, the description and the drawings. In this case, features and details that are described in connection with the method, of course, also in connection with the inventive apparatus for performing the method and in each case vice versa, so always reciprocally with respect to the disclosure of the individual aspects of the invention is or can be.

• – Einbringen einer elastisch verformbaren Negativform in ein Formwerkzeug, das im Bereich der wenigstens einen Hinterschneidung bewegbar ausgebildet ist,
• – Einbringen eines reaktiven Kunststoffes in die Negativform zur Ausbildung einer Kunststoffschaumschicht des Formteils,
• – Positionieren einer Trägerstruktur in der Negativform in einem definierten Abstand zu der Negativform innerhalb einer festgelegten Zeitspanne nach dem Einbringen des reaktiven Kunststoffes in die Negativform, und
• – Schäumenlassen des reaktiven Kunststoffes, wobei der schäumende reaktive TrägKunststoff die erstruktur zum Ausbilden des Formteils kontaktiert.

According to a first aspect of the present invention, a method for producing a molded part for a motor vehicle is provided, wherein the molded part has at least one undercut and at least one non-marking surface structure in the region of the at least one undercut, comprising the steps:

• Inserting an elastically deformable negative mold into a mold which is designed to be movable in the region of the at least one undercut,
• Introducing a reactive plastic into the negative mold to form a plastic foam layer of the molded part,
• - Positioning a support structure in the negative mold at a defined distance to the negative mold within a specified period of time after the introduction of the reactive plastic in the negative mold, and
• - Foaming the reactive plastic, wherein the foaming reactive Trägstoff plastic contacted the erstruktur to form the molding.

Characterized in that the reactive plastic is introduced into the mold so that it foams after positioning of the support structure to the plastic foam layer of the molding, can be dispensed with by the inventive method on the conventional plastic foaming process, in which the mold are sealed consuming during the foaming got to. Characterized abzeichnungsfreie moldings, ie homogeneous moldings without boundary edges or the like with undercut can be realized in a particularly simple and cost-effective manner.

Another advantage according to the method according to the invention is that the molded part itself does not have to be formed deformable in the region of the marking-free outer layer, and therefore can basically be configured as desired in terms of material and / or wall thickness. In addition, the fact that all components of the molding are applied without process-delaying removal of an intermediate in a single, lined with the negative mold mold, the production cost of the molding can be significantly reduced.

The marking-free surface structure is preferably a grained surface structure. The negative mold is preferably introduced into the mold in such a way that it is supported in a dimensionally stable manner on a part of the mold. The reactive plastic can be applied directly to the negative mold. Alternatively, an intermediate layer between the reactive plastic and the negative mold can be introduced, d. h., Before the reactive plastic is introduced into the negative mold, an intermediate layer is applied to the negative mold. In particular, when using a dyed reactive plastic can be dispensed with the intermediate layer. A reactive plastic is preferably to be understood as a plastic material which reacts within a defined period of time from a flowable state into an at least partially foamed and / or cured state. The reaction can start and run automatically or be initiated by external means, such as heating above a reaction temperature or a chemical reaction. For the person skilled in the art, it is within the scope of his ability to adjust the reactive plastic such that, according to the invention, it only foams into the final plastic foam layer after the carrier structure has been introduced into the negative mold, thereby contacting the carrier structure.

A contacting of the reactive plastic with the carrier structure is preferably to be understood as a chemical or cohesive contacting. That is, when the reactive plastic contacts the support structure for forming the molded part and thereby forms the plastic foam layer, the reactive plastic preferably bonds to the support structure in a materially bonded manner. During the foaming of the reactive plastic, it is also possible to move or push the carrier structure into the reactive plastic. In this case, the molding tool is preferably closed or substantially closed. As a result, the method according to the invention can be accelerated.

The support structure preferably has a complementary shape or a complementary surface to a surface, in particular the surface of the negative mold facing away from the mold. As a result, the support structure can be positioned over its entire surface at a particularly uniform distance from the negative mold, which in turn allows a particularly uniform plastic foam layer to be produced.

A simple and cost-effective way to introduce the reactive plastic in the negative mold is to spray it onto a mold surface of the negative tool.

The negative mold is preferably produced in a separate production step by means of a prototype tool, from which it can be pulled off elastically.

The introduction of the reactive plastic or the positioning of the support structure in the negative mold means in the sense of the present invention that the reactive plastic or the support structure is at least partially surrounded by an inner side of the negative mold.

The fact that the molding tool is designed to be movable in the region of the at least one undercut means that it is preferably formed in several parts and / or divisible in this region, wherein different parts of the molding tool are arranged to be relatively movable or displaceable relative to one another. The molding tool preferably has a mold lower part, a mold upper part and at least one mold side part. When introducing the negative mold into the mold, the at least one mold side part is preferably moved relative to the lower mold part or moved outwards or distally. In this case, the negative mold can be introduced into the mold in an undeformed state or in a substantially undeformed state. After positioning the support structure in the negative mold is or is the mold preferably closed, that is, is in a closed state, in which the components of the mold are in an end position. Even before the mold is in the closed state, the entire reactive plastic is in the negative mold. Alternatively, it is also possible according to the invention for the elastically deformable negative mold to be introduced into the molding tool when the molding tool side part is already in a closed position or a corresponding end position.

The support structure is preferably a material layer located on the mold upper part when closing the mold, which is formed to be complementary or substantially complementary to the negative mold.

After consolidation of the molded part in the mold, the mold is opened and the molded part can be removed together with the negative mold from the open mold and then separated from it under elastic deformation of the female mold.

According to one embodiment of the present invention, the support structure is spaced or positioned substantially at a distance from the reactive plastic. This ensures that the reactive plastic can be left to foam even after the positioning of the support structure and thus after the closing of the mold even further to the plastic foam layer. For the purposes of the present invention, the support structure is still substantially at a distance from the reactive plastic if the support structure removes a small portion of the reactive plastic during positioning in the negative mold and this part remains adhered to the support structure.

According to the invention, it is also advantageous if the time interval is determined as a function of the defined distance between the support structure and the negative mold, the amount of incorporated reactive plastic and / or the expansion coefficient of the foaming reactive plastic. Thereby, the distance between the support structure and the negative mold can be set particularly preferably. For the purposes of the present invention, the coefficient of expansion is to be understood as meaning a size or speed of how fast the reactive plastic used expands or increases during foaming after introduction into the negative mold.

Furthermore, according to the present invention, it is possible that the distance between the support structure and the negative mold is defined as the thickness of the plastic foam layer of the finished molded part. As a result, the desired thickness or thickness of the plastic foam layer is advantageously determined in the mold.

As reactive plastic, a polyurethane system is preferably used according to the invention. Various reactive plastic materials are known from the prior art, with the use of a polyurethane system having been found to be particularly advantageous in practice, in particular with regard to foaming.

In addition, it is possible to introduce a paint layer forming the surface structure of the molding in the negative mold or on the inside of the same prior to the introduction of the reactive plastic. By introducing such a cover layer into the negative mold, advantageous optical and haptic properties can be achieved. Furthermore, a high imaging accuracy and a finely grained molding surface are possible through the paint layer. The lacquer layer according to the invention can be applied to the negative mold, for example by means of in-mold coating. As an alternative to the lacquer layer, it is also possible, according to the invention, to introduce a film into the negative mold as a cover layer of the molded part or to apply it to this.

It is particularly advantageous if the lacquer layer release agent-free, d. h., Is sprayed directly onto the negative mold. As a result, time-consuming cleaning operations for cleaning the negative mold after removal of the same from the finished molded part can be dispensed with.

In addition, according to the present invention, it is possible to coat the paint layer in the negative mold with a paint carrier layer on the back. As a result, the lacquer layer can be advantageously reinforced. The paint carrier layer has, for example, a polyurethane foam or consists of this. The wall thickness of the paint carrier layer is, for example, thinner than 10 mm, preferably thinner than 5 mm and particularly preferably thinner than 2 mm, for example 1 mm applied.

Moreover, according to the present invention, it is possible to use the elastically deformable female mold multiple times. As a result, the inventive method is particularly economical. Since the negative mold is not destroyed during the production of the molding and hardly wears, a particularly frequent reuse of the negative mold is possible. It is further advantageous if the negative mold made of silicone is prefabricated in a galvanoform or another grain form, for example in an etching tool. A negative mold produced in this way has particularly advantageous elastic and wear-resistant properties. Moreover, it is possible that the molded part according to the invention can be manufactured as an instrument panel or at least as part of an instrument panel of a motor vehicle.

According to a further aspect of the present invention, an apparatus for producing a molded part for a motor vehicle is provided with at least one undercut and with a surface structure that is at least unsigned in the region of the at least one undercut. The device is suitable for carrying out the above method and has the molding tool, which is designed to be movable in the region of the at least one undercut.

Thus, the device according to the invention brings about the same advantages as have been described in detail with reference to the method according to the invention.

By the device according to the invention it is also possible to implement process parameters such as a mold temperature or the pressure in the mold, for example for spraying a molding skin or the paint layer and foaming the reactive plastic for producing an undercut molding in a single mold.

For the escape of air between the support structure and the reactive plastic during the foaming of the reactive plastic, it is preferred that in the device according to the invention an air outlet device is provided. The air outlet device may be, for example, a channel or a plurality of channels.

Further, measures improving the invention will become apparent from the following description of an embodiment of the invention, which is shown schematically in the figures. All of the claims, description or drawings resulting features and / or advantages, including constructive details and spatial arrangements may be essential to the invention both in itself and in the various combinations. Each show schematically:

1 a method step according to an embodiment of the present invention,

2 a further method step according to an embodiment of the present invention,

3 a further method step according to an embodiment of the present invention,

4 a further method step according to an embodiment of the present invention,

5 a further method step according to an embodiment of the present invention,

6 a further method step according to an embodiment of the present invention,

7 a further method step according to an embodiment of the present invention, and

8th a further method step according to an embodiment of the present invention.

Elements with the same function and mode of action are in the 1 to 8th each provided with the same reference numerals.

1 shows a part of a mold 30 More specifically, a mold base 32 and two mold side parts 36 , Furthermore, in 1 a prefabricated, undercut and elastically deformable negative mold 20 shown. In a first process step, the negative mold 20 in the undeformed state or substantially undeformed state in the open mold 30 brought in. In the case of the movable in the region of the undercut mold 30 this will be the two mold side parts 36 moved outwards or distally to the side.

2 shows the next step of the illustrated embodiment. This is done by means of a spray device 72 a very uniform paint layer 70 on the negative mold 30 applied.

In the in 3 shown further process step is to form a plastic foam layer 52 of the molding 10 reactive plastic 50 , in particular a polyurethane system, in the negative mold 20 brought in. The reactive plastic 50 is provided or adjusted so that this directly after insertion into the negative mold 20 starts to foam automatically. The reactive plastic 50 is here adjusted so that the foaming and curing proceeds so slowly that before this is completed, nor a support structure 60 into the cavity of the negative mold 20 can be introduced without the support structure 60 in contact with the reactive plastic 50 comes. In 3 is also a mold top 34 with the carrier structure applied thereto 60 shown. The mold is located in 3 in an open state.

4 shows a further method step according to the embodiment of the invention. This is the support structure 60 in the negative form 20 at a defined distance to the negative mold 20 positioned, within a specified period of time after the introduction of the reactive plastic 50 in the negative form 20 , More specifically, the support structure 60 in this process step spaced from the reactive plastic 50 while allowing it to continue to foam. The mold 30 is located after or during the positioning of the support structure in a closed state. The distance between the support structure 60 and the negative mold 20 corresponds to the thickness of the plastic foam layer 52 of the finished molding 10 ,

In 5 is a foaming of the reactive plastic 50 shown in the closed state of the mold, wherein the foaming reactive plastic 50 the support structure for forming the molding 10 already contacted. The air gap between the reactive plastic 50 and the support structure becomes during full foaming and reaction of the reactive plastic 50 filled, wherein the support structure cohesively with the reactive plastic 50 is connected. The air previously located between these two layers can be displaced via a corresponding air outlet opening.

6 shows a further method step of the embodiment according to the invention. After the reactive plastic 50 to the finished plastic foam layer 52 cured or consolidated, the mold is 30 opened and the molding 10 including negative form 20 is without elastic or plastic deformation of the molding 10 or the negative mold 20 from the open mold 30 taken. This from the molding 10 and the negative mold 20 existing overall molding is in 7 shown.

Subsequently, as in 8th represented, the elastic negative mold 20 from the finished molding 10 removed or removed and provided for reuse.

The pointed in the figures pointed edges of the mold 30 and / or the respective material forms are of course not limited thereto. So it is of course also possible to produce molded parts with rounded edges in a suitably designed mold and a correspondingly shaped negative mold.

In addition to the embodiment shown above, further developments according to the invention are conceivable. For example, it is possible that the elastically deformable negative mold 20 in the mold 30 is introduced when the mold side part 36 already in a closed position or a corresponding end position on the lower mold part 32 located. In this case, the mold is 30 designed such that the mold upper part 34 and the support structure applied thereto 60 despite closed mold side part 36 past it into a closed position or corresponding end position (see position in 4 ).

LIST OF REFERENCE NUMBERS

10

molding

20

negative form

30

mold

32

Mold base

34

Mold shell

36

Mold side part

50

reactive plastic

52

Plastic foam layer

60

support structure

70

paint layer

72

sprayer

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0342473 B1 [0005]

Claims (12)

Method for producing a molded part ( 10 ) for a motor vehicle, wherein the molded part ( 10 ) has at least one undercut and at least one in the region of the at least one undercut abzeichnungsfreien surface structure, comprising the steps: - introducing an elastically deformable negative mold ( 20 ) in a mold ( 30 ), which is designed to be movable in the region of the at least one undercut, - introducing a reactive plastic ( 50 ) in the negative form ( 20 ) for forming a plastic foam layer ( 52 ) of the molded part ( 10 ), - positioning a support structure ( 60 ) in the negative form ( 20 ) at a defined distance from the negative mold ( 20 ) within a specified period of time after the introduction of the reactive plastic ( 50 ) in the negative form ( 20 ), and - foaming the reactive plastic ( 50 ), wherein the foaming reactive plastic ( 50 ) the support structure for forming the molded part ( 10 ) contacted. Method according to claim 1, characterized in that the support structure ( 60 ) spaced or substantially spaced from the reactive plastic ( 50 ) is positioned. Method according to claim 1 or 2, characterized in that the period of time depends on the defined distance between the support structure ( 60 ) and the negative form ( 20 ), the amount of incorporated reactive plastic ( 50 ) and / or the expansion coefficient of the foaming reactive plastic ( 50 ). Method according to one of the preceding claims, characterized in that the distance between the support structure ( 60 ) and the negative form ( 20 ) as the thickness of the plastic foam layer ( 52 ) of the finished molding ( 10 ) is defined. Method according to one of the preceding claims, characterized in that as reactive plastic ( 50 ) a polyurethane system is used. Method according to one of the preceding claims, characterized in that prior to the introduction of the reactive plastic ( 50 ) a the surface structure of the molded part ( 10 ) forming paint layer ( 70 ) in the negative form ( 20 ) is introduced. Method according to claim 6, characterized in that the lacquer layer ( 70 ) release agent-free on the negative mold ( 20 ) is sprayed on. A method according to claim 6 or 7, characterized in that the lacquer layer ( 70 ) in the negative form ( 20 ) is coated on the back with a paint carrier layer. Method according to one of the preceding claims, characterized by a multiple use of the elastically deformable negative mold ( 20 ). Method according to one of the preceding claims, characterized in that the negative mold ( 20 ) is prefabricated from silicone in a Galvanoform. Method according to one of the preceding claims, characterized in that the molded part ( 10 ) is manufactured as an instrument panel or at least as part of an instrument panel of a motor vehicle. Device for producing a molded part ( 10 ) for a motor vehicle by a method according to one of the preceding claims, comprising a molding tool ( 30 ), which is designed to be movable in the region of the at least one undercut.

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