FR3070618A1 - PROCESS FOR MANUFACTURING A PLASTIC PART - Google Patents

Abstract

A method of manufacturing a radome for a radar of a vehicle made of two thermoplastic materials and provided with a film (3), using a mold comprising a first portion (10) and a second portion (20). ), the two parts (10, 20) delimiting a first molding chamber (100), the method comprising the following steps: - deposition of the film (3) on a wall (21) of the second part (20); - first closing of the mold; injecting a first thermoplastic material into the first molding chamber (100) to obtain a first overmolded layer (1) on the film (3), - opening of the mold, - second closing of the mold so as to form a second chamber molding (200) using a third portion (30) delimiting with the first portion (10) the second molding chamber (200) - injecting a second thermoplastic material into the second molding chamber (200) to obtain a second overmolded layer (2) on the film (3), the film (3) being positioned between the first and second overmolded layers 1, 2.

Description

The invention relates to a method of manufacturing a plastic part. The invention relates more particularly to a method of manufacturing a part for a vehicle, whether it be a motor vehicle or a human powered vehicle. The invention also relates to a part obtained by the manufacturing process. The invention also relates to a set of a radar for a vehicle equipped with a part obtained by the manufacturing process and a vehicle fitted with such a set.

It has already been proposed, in patent EP2640609, a method of manufacturing a decorative radome, which may be the emblem or the logo of the front grille, for a motor vehicle by independent molding of two parts and assembly of these two pieces by gluing. A decoration film is placed on one of the two pieces before bonding so that the film is caught between the two pieces after bonding. Such a process requires the manufacture of two different parts and therefore the use of two presses or at least two different tools. Furthermore, in this type of process, there may be insufficient sealing and trapping of air bubbles between the two parts. Such a phenomenon disturbs, or even prevents, the passage of waves through this part, especially when the part is used as a device for protecting a vehicle radar, also called a radome. In addition, a radome thus obtained imposes geometric constraints on the radar used, because the type of radar is limited by the size of the logo.

The present invention aims in particular to remedy these drawbacks by providing an alternative method of manufacturing a plastic part, in particular a radome for a radar of a vehicle.

To this end, the invention relates to a method of manufacturing a radome for a radar of a vehicle made of two thermoplastic materials and provided with a film, using a mold comprising a first part and a second part, the two parts delimiting a first molding chamber, the method comprising the following steps:

- deposition of the film on a wall of the second part;

- first closing of the mold;

- injection of a first thermoplastic material into the first molding chamber to obtain a first layer overmolded on the film,

- mold opening,

- second closing of the mold so as to form a second molding chamber using a third part delimiting with the first part the second molding chamber,

- injection of a second thermoplastic material into the second molding chamber to obtain a second overmolded layer on the film, the film being positioned between the first and second overmolded layers.

The first part may correspond to the mold of the mold and the second part may correspond to a punch having means for ejecting the first overmolded layer after the injection of the first thermoplastic material into the first molding chamber. The third part may correspond to a second punch having characteristics different from the punch used for the first molding chamber. The first layer is overmolded on one side of the film and remains on the first part of the mold while the other side of the film is exposed to the open air in order to be able to receive the injection of the second thermoplastic material once the second molding chamber is closed. Thus, the film remains positioned in the mold during the injection of the second thermoplastic material. No manipulation of the film is necessary which prevents damage to the film. Furthermore, the second layer of thermoplastic material is added to the part previously overmolded by injection of material, which makes it possible to obtain a good seal between the two layers while avoiding air bubbles or impurities which may be there. in a manufacturing process requiring a bonding step.

The method may also include one or more of the following characteristics, taken alone or in combination:

- The method comprises a step of changing the position of the first part before the second closing of the mold. The change in position of the first part frees up the space near the second part so that a new film can be placed on the wall of the second part for molding the next part.

- The step of changing the position of the first part is a step of rotating the first part, so as to position itself vis-à-vis the third part. To do this, overmolding can be carried out using a plate or a rotating base. The punches are therefore positioned around the axis of the plate or the base.

- The step of changing the position of the first part is a step of translating the first part, so as to position itself vis-à-vis the third part.

To do this, overmolding can be carried out using a carriage moving on the press platform. The punches are therefore positioned on the path of this carriage.

- The first thermoplastic material is chosen from the following materials: polycarbonate (PC), polypropylene (PP), polymethyl methacrylate (PMMA), polyamide (PA) or copolyester, such as polyethylene terephthalate (PET).

- The second thermoplastic material is chosen from the materials of the first thermoplastic material or else in the following materials, preferably black in color: acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polypropylene (PP). The choice of materials used for each injection makes it possible to obtain a first transparent or translucent layer and a second opaque layer.

- The film includes a decorated and preferably metallized surface. The metallized surface with a chrome appearance allows to meet the aesthetic needs of the molded part depending on the vehicle model. During overmolding, the metallized surface is overmolded by the first thermoplastic material which is preferably transparent. The opposite surface of the film is therefore overmolded by the second thermoplastic material which is preferably opaque. The decorated part of the film is therefore located between the film and the first thermoplastic material. This makes it possible to obtain a part having a better gloss and a better sharpness of the metallic design. This is particularly advantageous when you want a three-dimensional depth effect for the decor, as is often the case for metallic logos. This configuration also makes it possible not to show the interface between the film and the decorated area because this interface area which is perhaps less aesthetic is hidden by the decoration.

This metallized surface which is a functional surface of the film is quickly protected from the injection of the first thermoplastic material. In addition, after the first injection, the film is held over its entire surface on the first layer, which makes it possible to inject the second thermoplastic material, the thickness of which could even be greater and possibly with greater risks of deformation of the film. if this second material was injected first. The process makes it possible to overmold a decorated film over a large area, with a minimum of handling, because the film is positioned only at the bottom of the impression by an operator or in an automated manner, then, at the end of the different injection steps without leaving of the press, the final part is obtained, in a reproducible manner and at a very high rate, with a film completely protected on its two faces, with an interface without air bubble, a constant thickness over the entire surface serving as a radome, in order to have good transparency on the air.

- The metallized surface is obtained by a process for depositing a material, preferably by a vapor deposition technique, or by a painting process, or by overmolding a metallized film or by a marking technique hot. The use of this type of coating allows the passage of radar waves to ensure the detection functions in the context of the development of partially or fully autonomous vehicles. The film has good compatibility with the first and second thermoplastic material so that the interface is of good quality (without air bubble, without film deformation ...) so that the transparency at the waves is the best possible and this reproducibly even on a film of a large area.

- The process includes a step of thermoforming the film prior to the step of closing the first molding chamber. It is a question of bringing a 3D form before the injection of the first plastic material. The film is therefore well deployed and homogeneous in thickness, which makes it possible to limit the risks of deformation and even of rupture during the injection process.

- The process includes a film cutting step following the film thermoforming step. This configuration avoids delamination of the final part, which is all the more risky since the surface of overmolded film is large. This delamination deteriorated the aesthetics of the room and hindered the passage of waves. The risk of air or water entering between the two overmolded layers is also limited, which prevents the part from aging.

- The film includes a heating element. The heating element makes it possible to add a defrosting function to the molded part. The heating element can be a wire integrated directly into the film or a pattern of heating material. This pattern can be deposited on the film according to a method chosen from the group consisting of screen printing, stencil, engraving printing, pad printing, flexography printing, offset printing, electrostatic printing and inkjet printing.

- The heating element is arranged on the surface of the film between the film and the second overmolded layer. This arrangement makes it possible to have a “heat shield” effect thanks to the second material since the heat is preferentially transmitted towards the outside of the part, through the first material which will advantageously have better thermal conductivity and may have a greater thickness. weak than the second material.

The film can be decorated or functionalized on both sides. Such a film is very fragile and must be handled with care so as not to deteriorate the decoration or the functionalization. In this case, the manufacturing process which is the subject of this invention makes it possible not to handle the film between the different injection stages and therefore to avoid the risk of damage.

The invention also relates to a part, preferably for a vehicle, obtained by the manufacturing process as described above. This part may be a large part, such as a motor vehicle grid, the dimensions of the front face of which can be 500 mm by 1200 mm. This part could also be a bumper skin whose dimensions of the front face can be 800 mm by 2000 mm.

The invention also relates to a set of a vehicle radar and a part obtained by the manufacturing process as described above.

The invention finally relates to a vehicle equipped with an assembly as described above.

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

FIG. 1 is a diagrammatic view of an example of a part manufacturing process during the injection of the first thermoplastic material,

FIG. 2 is a schematic view of the process according to FIG. 1 during the injection of the second thermoplastic material,

- Figure 3 is a schematic view of a first embodiment of the part comprising a heating element,

FIG. 4 is a schematic view of the method of manufacturing the part according to FIG. 3,

- Figure 5 is a schematic view of a second embodiment of the part comprising a heating element,

FIG. 6 is a detailed view of the part obtained by the manufacturing method according to a first variant,

- Figure 7 is a detailed view of the part obtained by the manufacturing method according to a second variant.

We will now describe a particular embodiment of the invention which is a method of manufacturing a part, the part being a wide radome and decorated for a radar of a vehicle.

A mold, as illustrated schematically in Figure 1 comprises a first part 10 and a second part 20, the two parts 10, 20 defining a first molding chamber 100. According to the example illustrated in Figures 1 and 2 , the first part 10 of the mold is mounted on a plate or a rotary base of an axis (A). A film 3 is placed on an internal wall 21 of the second part 20.

[00013] It is a plastic film carrying electronics, also called "plastronic film". This technology allows to integrate all kinds of functions (electronic, mechanical, optical ... and more particularly here functional elements for defrosting, light or electrical connection) directly on plastic parts, here a flexible polymer substrate , the functionalized part can then be deformed. We are talking about a functionalized film. The materials usually used are polyimide (PI), polyetheretherketone (PEEK), PolyEthylene Naphthalate (PEN) and other materials can be considered. In addition, this film has at least one decorated face, preferably metallized with a chrome appearance. The metallized surface is obtained by a process for depositing a material, preferably of the indium type, or by a painting process, or by overmolding a metallized film. The decorative coating, and in particular the metallized surface, is obtained by a technique known to those skilled in the art, such as the hot stamping technique (printing during which a film is pressed against a surface), or else via the overmolding of a metallized film (for example via the prior deposition of a thin coating layer which gives a metallic appearance, layer of the order of 0.5 μm), either by application of chromating paint, or else by the technique of vapor deposition (“Physical Vapor Deposition”, PVD), of metals such as indium, gold or tin. The use of these techniques and materials makes it possible to give the radome a metallic appearance, even though metallic elements generally disturb the transmission of radar waves.

When the film is completely placed on the wall 21 of the second part 20, a first closing of the mold is carried out and a first thermoplastic material is injected into the first molding chamber 100 to obtain a first overmolded layer 1 on the film 3. The first thermoplastic material is chosen from the following materials: polycarbonate (PC), polypropylene (PP), polymethyl methacrylate (PMMA), Polyamide (PA) or also copolyester, such as polyethylene terephthalate (PET). first thermoplastic material is transparent in color. It is important to place the film on the second part 20 with the face opposite to that which is metallized in contact with the internal wall 21. Thus, the first thermoplastic material is overmolded on this metallized face which makes it possible to obtain a part having a better gloss and a better sharpness of the metallized design.

Once the first overmolded layer 1 is obtained, the mold is opened to separate the first part 10 and the second part 20. Simultaneously, the first overmolded layer 1 is pushed back by ejection means which are arranged in the second part 20. The first overmolded layer 1 thus remains fixed on the first part 10 during the opening of the mold.

Once the two parts 10, 20 are separated, the first part 10 changes position by turning around the axis (A) so as to be positioned opposite a third part 30. Then , the mold is closed so as to form a second molding chamber 200 which is delimited by the first part 10 and the third part 30. This step is followed by an injection of a second thermoplastic material into the second molding chamber 200 to obtain a second overmolded layer 2 on the film 3. The second thermoplastic material is chosen from the following materials: acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polypropylene (PP), polymethyl methacrylate (PMMA), polyamide ( PA) or also copolyester, such as polyethylene terephthalate (PET). The second thermoplastic material is black in color and it is injected onto the film on the face opposite to that which is metallized. Thus, the film 3 is positioned between the first and second overmolded layers 1,2.

According to an alternative of the invention, the method may include a step of thermoforming the film prior to the step of closing the first molding chamber 100. A 3D shape can therefore be provided to the metallized face of the film before the injection of the first plastic material.

According to another alternative of the invention, the method comprises a step of cutting the film 3 following the step of thermoforming the film 3. The film 3 no longer spreads over the entire final part but only occurs on a predefined area of the room. In order to keep the film in place during the injections, and so that the film is well coated with thermoplastic material, two variants are possible:

The first variant illustrated in Figure 6 consists of an injection of the first thermoplastic material by creating a projecting area 5 at the edge of the film. During the injection of the second thermoplastic material, the second overmolded layer 2 takes a shape complementary to that of the first overmolded layer 1 which allows the film 3 to be well trapped between the two layers without having space around it.

The second variant illustrated in Figure 7 consists of an injection of the first thermoplastic material by creating a groove 6 between the film 3 and the mold. During the injection of the second thermoplastic material, in a similar manner to the first solution, the second overmolded layer 2 takes a shape complementary to that of the first overmolded layer 1. Because the film 3 is at the edge of the molding tool, so at the bottom of a housing, it is easier to position and hold it in place.

According to yet another alternative of the invention, the film 3 comprises a heating element 31 connected to an electrical supply wire 32. The heating element 31 is arranged between the film 3 and the second overmolded layer 2. According to a first embodiment as illustrated in FIGS. 3 and 4, an insert can be used in the mold to create a passage 4 for the electrical supply wire 32 in the second overmolded layer

2. This embodiment allows the electrical supply wire 32 to pass over the non-visible side of the final part and to avoid problems of integration of the part on the vehicle. One can also envisage a second embodiment according to which the electrical supply wire is biased between the two overmolded layers, as visible in FIG. 5.

The invention is not limited to the embodiments presented and other embodiments will be apparent to those skilled in the art. It is in particular possible to change the position of the first part 10 of the mold by a translational movement of this first part 10, so that it is positioned opposite the third part 30.

It is also possible to envisage another embodiment, according to which the method comprises a step of injecting a third plastic material via a third punch and the overmolding of a second film during this additional step. In this case, the second film is positioned in the imprint of the third punch and the part from the two previous injections is placed in front of this punch, preserving a volume in which the third plastic is injected. The first film may be a film with heating elements or a decorated film, and the second film is a decorated film. The first plastic material and the second plastic material are opaque materials which are on each side of the first film. The third plastic material can be a transparent material. The second film can be a decorated film. If the second film is positioned on the part resulting from the two previous injections before the injection of the third material, then this third material advantageously covers the second film.

The film can be held in the bottom of the imprint by electrostatics or else a suction system on the surface of the imprint can be envisaged to position it correctly and hold it in place during the injection of the plastic material. If the second film is positioned on the part resulting from the two previous injections, then an equivalent system for holding the film in place can be envisaged across the part.

Claims (15)

claims 1. Method of manufacturing a radome for a radar of a vehicle made of two thermoplastic materials and provided with a film (3), using a mold comprising a first part (10) and a second part (20), the two parts (10, 20) defining a first molding chamber (100), characterized in that it comprises the following steps: - deposition of the film (3) on a wall (21) of the second part (20); - first closing of the mold; - injection of a first thermoplastic material into the first molding chamber (100) to obtain a first overmolded layer (1) on the film (3), - mold opening, - second closing of the mold so as to form a second molding chamber (200) using a third part (30) delimiting with the first part (10) the second molding chamber (200), - injection of a second thermoplastic material into the second molding chamber (200) to obtain a second overmolded layer (2) on the film (3), the film (3) being positioned between the first and second overmolded layers 1,2 . 2. Method according to the preceding claim comprising a step of changing the position of the first part (10), prior to the second closing of the mold. 3. Method according to the preceding claim, wherein the step of changing the position of the first part (10) is a step of rotating the first part (10), so as to position vis-à-vis the third part (30). 4. Method according to one of claims 1 to 3, wherein the step of changing the position of the first part (10) is a step of translating the first part (10), so as to position itself vis- with respect to the third part (30). 5. Method according to any one of the preceding claims, in which the first thermoplastic material is chosen from the following materials: polycarbonate (PC), polypropylene (PP), polymethyl methacrylate (PMMA), polyamide (PA) or also copolyester, such as polyethylene terephthalate (PET). 6. Method according to any one of the preceding claims, in which the second thermoplastic material is chosen from the following materials, preferably black in color: acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polypropylene (PP), polymethacrylate methyl (PMMA), polyamide (PA) or copolyester, such as polyethylene terephthalate (PET). 7. Method according to any one of the preceding claims, in which the film comprises a decorated and preferably metallized surface. 8. Method according to the preceding claim, wherein the metallized surface is obtained by a method of depositing a material, preferably by a vapor deposition technique, or by a painting process, or by overmolding. a metallized film or by a hot stamping technique. 9. Method according to any one of the preceding claims, comprising a step of thermoforming the film prior to the step of closing the first molding chamber (100). 10. Method according to the preceding claim, comprising a step of cutting the film following the step of thermoforming the film. 11. Method according to any one of the preceding claims, in which the film (3) comprises a heating element (31). 12. Method according to the preceding claim, wherein the heating element (31) is arranged on the surface of the film (3) between the film (3) and the second overmolded layer (2). 13. Part, preferably for vehicle, obtained by the manufacturing process according to any one of the preceding claims. 14. Set of a radar for a vehicle and a part obtained by the manufacturing process according to any one of the preceding claims. 15. Vehicle equipped with an assembly according to the preceding claim.