FR3096918A1 - Process for manufacturing an automotive body part from plastic - Google Patents

Abstract

The invention relates to a method of manufacturing a body part (2) in plastic material, by means of a mold (11, 12) comprising a molding chamber defining the shape of the part, comprising the following steps: depositing , on a wall of the molding chamber, a film (1) comprising at least one textured face, the textured face being turned towards the inside of the molding chamber; injecting a plastic material into the molding chamber in order to obtain the body part (2) having a relief pattern given by the film (1); remove the bodywork part (2) from the mold (11, 12). Figure for the abstract: Fig. 1

Description

Process for manufacturing a plastic automobile body part

The invention relates to the technical field of the manufacture of automobile body parts made of plastic material, by an injection molding process.

To manufacture plastic parts, preferably thermoplastic (TP), it is known to use an injection molding process. Such a method uses molding equipment comprising:

• a mold provided with a movable element and a fixed element, the two elements, typically made of steel, forming a molding chamber in the closed position of the mould;
• the facing surfaces in the chamber of the fixed element and the mobile element forming the molding parts of the part and simultaneously giving it all its shapes and its surface appearance;
• a press, usually hydraulic, allowing the mobile element to be moved towards the fixed element.

Depending on the functions of the bodywork part, it may be necessary to add a particular aspect to it or make it aesthetic by a pattern in relief, such as graining, streaks, a grid, on its outer surface to obtain a visible surface called " textured”. It is known from the state of the art a process for molding a bodywork part having such a textured appearance by integrating, for example by machining or chemical attack, the pattern in relief in the steel surface of the molding chamber. . The desired appearance is thus obtained on the bodywork part by the injected material which takes the form of the pattern in relief against the molding wall of the chamber. This technique has the disadvantage of being able to achieve only one aspect on all the parts produced by this mould. To obtain another style of surface on a part of the same shape, it is necessary to change all or part of the mould, at least at the level of its surface having the textured pattern, which makes the process complicated and generates a significant additional cost.

The object of the invention is in particular a process for manufacturing a body part having a textured surface which is simple, fast and inexpensive and above all adaptable.

To this end, the subject of the invention is a process for manufacturing a plastic bodywork part, by means of a mold comprising a molding chamber defining the shape of the part, comprising the following steps:

• depositing, on a wall of the molding chamber, a film comprising at least one textured side, the textured side facing the inside of the molding chamber;
• injecting a plastic material into the molding chamber in order to obtain the body part comprising a relief pattern given by the film;
• remove the body part from the mould.

The film makes it possible to bring a particular raised aspect to the face of the bodywork part without specific preparation or definitive impact on the surfaces of the molding chamber. Thus, it is possible to modify the appearance of parts produced by the same mold more easily and at a lower cost. The textured face corresponds to a textured surface or a discontinuous surface. When it comes to a textured surface, hollows or bumps are present on the textured side which result from a preforming of the film by stamping without removing any material. The textured surface is then inside the molding chamber to come into contact with the injected material; when it is a discontinuous surface, areas are cut in the thickness of the film by removing material. The areas then become perforated areas in order to provide extra thicknesses on the surface of the bodywork part. The film can thus include relief patterns, such as graining, cut-out areas or changes in thickness forming a design or logo.

According to other optional characteristics corresponding to different embodiments of the manufacturing process, taken alone or in combination:

• The method includes a step of fixing the film in the mold so that the film remains in the mold when the body part is removed from the mold. This makes it possible to produce a series of bodywork parts with the same film, without having to reapply a new film before each molding. The process is simpler, faster and less expensive. Any type of fixation can be considered, such as adhesion, mechanical fixation, suction or even electrostatic fixation.
• The film and/or the mold are configured so that the film is maintained in the mold only during the molding of the bodywork part and remains on the bodywork part when the latter is removed from the mold. Thus, it is possible to change the shape of the film and therefore the appearance with each molded part successively. This also makes it possible to protect the textured surface of the part, in particular in the event of a graining which is often fragile and liable to be damaged during transport or storage. It is thus necessary to hold the film in place in the mold by a temporary means, capable of being activated and deactivated synchronously with the molding cycle, so that the film does not remain attached to the mold after the opening of the mold to eject the part. Mechanical retention, by adhesion or overmolding points with low mechanical strength, or electrostatic retention between the film and the bodywork part is preferable so that the film can come out of the mold with the bodywork part and be easily removed by the following.
  With a cut-out film, the shapes in relief obtained on the part can then be, during a subsequent finishing step, covered and decorated, for example by hot stamping (known as "hot-stamping"), by pad printing or by another decorative film (for example "stickers") glued to the part. The cut-out film then advantageously makes it possible to perform a masking function, and thus only the zones of the part visible through the cut-outs will for example be painted or pad-printed.
• The resistance of the film to temperature is higher than the temperature of implementation in the mold of the injected plastic material. For example, when the bodywork part is made of polypropylene, the film should be able to withstand a temperature of at least 200°C.
• The material constituting the film is preferably chosen from: polycarbonate (PC), polyetherimide (PEI), polyarylene sulfone (PES), polymethyl methacrylate (PMMA), thermoplastic polyolefin (TPO), thermoplastic polyurethane (TPU), acrylonitrile butadiene styrene (ABS ), polyvinyl chloride (PVC), polypropylene (PP), polyamide (PA).
• The thickness of the film is between 0.1 and 3 mm.
• The film includes a protective layer configured to prevent adhesion of the film to the body part.

The invention also relates to a part obtained by implementing the method as described above.

The invention also relates to a film made of plastic material, and comprising at least one textured face, the film being capable of being in contact with a plastic material injected into an injection mold for an automobile body part. The relief surface of the film is made up of non-through reliefs of the thickness of the film, such as for example graining, embossing or of through reliefs of the thickness of the film, such as for example slits, cut-outs.

Another subject of the invention is a mold for the manufacture of plastic parts comprising a fixed element and a movable element, the two elements delimiting a molding chamber in the closed position of the mold, at least part of the surface molding the chamber consisting of an embossed film, preferably plastic.

Brief description of figures

The invention will be better understood on reading the following description given solely by way of example and made with reference to the appended drawings in which:

Figure 1 is a sectional view of a mold during manufacture of a part according to one embodiment of the invention;

FIG. 2a is a perspective view of a film according to one embodiment of the invention;

Figure 2b is a sectional view of the film of Figure 2a;

FIG. 3a is a perspective view of a part obtained by a manufacturing method according to the invention using the film of FIG. 2a;

Figure 3b is a sectional view of the part of Figure 3a.

detailed description

There is shown in Figure 1 a mold according to one embodiment of the invention, designated by the reference 10. The mold 10 comprises a fixed element 12 and a movable element 11 delimiting a molding chamber in the closed position of the mold. A film 1 is deposited in the molding chamber and on the wall of the movable element 11 in this example. Movie 1 will be described later. After injection of a plastic material into the molding chamber, a part is obtained, in particular a body part 2 which bears a pattern in relief given by the film 1.

When the process is finished, the bodywork part 2 is taken out of the mold 10. The film can remain in the mold to produce a series of bodywork parts with the same film; by using a temporary holding means, the film can also remain on the bodywork part when the latter comes out of the mould.

The film 1 used in the manufacturing process described above is illustrated in FIGS. 2a and 2b according to an embodiment in which the film 1 comprises a first zone 3 having here a square shape. This first zone 3 has a textured surface, for example graining. Furthermore, the film 2 comprises a second zone 4 having here a rectangular shape.

As visible in FIG. 2b which is a sectional view along plane AA, the second zone 4 is cut out in the thickness of the film 1 by removal of material and becomes an openwork zone. The second zone 4 forms with the rest of the film 1 a discontinuous surface.

By using the film 1 described above and illustrated in FIGS. 2a and 2b in the manufacturing method according to the invention, a bodywork part 2 is obtained as can be seen in FIGS. 3a and 3b. The bodywork part 2 comprises a first zone 5 having a textured surface, corresponding to zone 3 of the film. This surface has a texturing of a shape complementary to that arranged on the film 1 and in this example forming a graining on the bodywork part 2.

As seen in Figure 3b which is a sectional view along the plane AA, the body part 2 comprises a second zone 6 corresponding to the zone 4 of the film and having an extra thickness on the surface of the body part 2. thickness of the second corresponding zone 6 corresponds to the thickness of the film 1.

The invention is not limited to the embodiments shown and other embodiments will be apparent to those skilled in the art. It is in particular possible for the first zone 3 and/or the second zone 4 of the film 1 to form a particular design or a desired logo.

Claims (10)

Method of manufacturing a bodywork part (2) in plastic material, by means of a mold (11, 12) comprising a molding chamber defining the shape of the part, comprising the following steps:

• depositing, on a wall of the molding chamber, a film (1) comprising at least one textured face, the textured face being turned towards the interior of the molding chamber;
• injecting a plastic material into the molding chamber;
• removing the body part (2) from the mold (11, 12).

Method according to the preceding claim comprising a step consisting in fixing the film (1) in the mold (11, 12) so that the film (1) remains in the mold (11, 12) when the bodywork part (2 ) is taken out of the mold (11, 12). Method according to claim 1 in which the film (1) is configured so that the film is held in the mold (11, 12) only during the molding of the body part (2) and remains on the body part (2) when the latter has left the mold (11, 12). Method according to one of the preceding claims, in which the temperature resistance of the film (1) is greater than the melting point of the injected plastic material. Process according to the preceding claim, in which the material constituting the film (1) is chosen from: polycarbonate (PC), polyetherimide (PEI), polyarylene sulphone (PES) and polymethyl methacrylate (PMMA), thermoplastic polyolefin (TPO), thermoplastic polyurethane (TPU ), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), polypropylene (PP), polyamide (PA). Method according to one of the preceding claims, in which the thickness of the film (1) is between 0.1 and 3 mm. Method according to one of the preceding claims, in which the film (1) comprises a protective layer configured to prevent the adhesion of the film (1) to the bodywork part (2). Bodywork part (2) obtained by implementing the method according to one of the preceding claims. Film (1) made of plastic material, and comprising at least one textured face, the film being capable of being in contact with a plastic material injected into an injection mold for a car body part. Mold (11, 12) for manufacturing plastic parts comprising a fixed element (12) and a movable element (11), the two elements delimiting a molding chamber in the closed position of the mould, at least part of the surface molding of the chamber comprising a film (1) in relief, preferably according to the preceding claim.