FR3087376A1 - METHOD FOR MANUFACTURING AUTOMOTIVE PARTS COMPRISING A STEP OF COATING A LIQUID SUPPORT IN A MOLD, AND PARTS ARISING FROM THE PROCESS - Google Patents

Abstract

The invention relates to a method of manufacturing parts intended to be installed in a vehicle, comprising the following successive steps: coating (1.4) of a support in liquid form on the inner wall of a mold followed by a drying step of said support during which the support stiffens, and removal (1.10) of the part formed after hardening of the foam. In this way parts for the automotive industry are produced in a faster and simpler process, all being very stiff and having a good appearance. According to a particular embodiment, the method comprises a step of spraying (1.7) foam on said support followed by a step of a first determined duration during which the foam hardens.

Description

Method of manufacturing automotive parts comprising a step of coating a liquid support in a mold, and parts resulting from the method 1 TECHNICAL FIELD The field of the invention is that of the manufacture of parts intended to equip means of transport, and in particular motor vehicles.

The invention relates more precisely to the fact that the parts are manufactured by coating a mold with a liquid support which stiffens during drying, the part thus produced is removed after hardening of the support.

2 TECHNOLOGICAL BACKGROUND The present invention relates to the manufacture of automotive parts in composite material using plastics and expanded foam, or hard panels, cut and glued.

It particularly relates to a process allowing the manufacture of automobile parts and more particularly of bodywork parts.

Nowadays, a motor vehicle can include many plastic parts usually made by an injection molding process.

The parts obtained can be structural or semi-structural parts of the motor vehicle in question.

The current manufacturing process consists of placing a skin (or “Gel Coat” in the Anglo-Saxon language) at the bottom of a mold, which will ultimately give the external appearance.

The automotive part generally needs to be reinforced with resin coated glass or carbon fibers which are laid on the skin and bonded with it.

Always kept in its mold, the part is then either covered with a determined layer of foam which expands and hardens as it dries, or glued to panels of hardened foam.

In the case of expanded foam, once dry and hard, it can be worked to obtain the desired thickness, for example using a milling cutter which eliminates excess thickness.

The part is then unmolded and possibly cut out with a milling cutter to give it its final dimensions.

Some auto parts must have a good appearance on both sides.

In this case, these parts consist of two panels which are glued against each other leaving a gap between the two.

The foam is then injected between the two panels, which once hardened, ensures the bonding between the two panels.

2 In the case of parts requiring great rigidity, one or more inserts are integrated into the manufacturing process.

These inserts are preformed parts incorporated in and / or integral with said molded part which generally serve to reinforce said molded part and / or for the subsequent fixing of mechanical elements.

These inserts 5 can be made of wood, steel, aluminum or composite plastics.

These inserts are secured with the resin and the glass and carbon fibers, and covered with foam.

In the case of expanded foam, the current manufacturing process requires a period of drying thereof which monopolizes the production line for a part 10 for a long time, typically a few hours.

There is therefore a real need to implement a new process which shortens the duration of manufacture of automotive parts.

In addition, the current manufacturing process is complex because it requires several elements to manufacture the parts.

It would be advantageous to simplify the process by eliminating the use of certain layers and minimizing the drying time between the components used.

3 SUMMARY According to the invention, there is thus proposed a method of manufacturing parts 20 intended to be installed in a vehicle, comprising the following successive steps: coating a support in liquid form on the inner wall of an open mold followed by a step of drying said support during which the support stiffens; 25 removal of the formed part after hardening of the support.

Thus, the invention proposes to produce parts for the automotive industry according to a faster and simpler process, while providing parts of great rigidity and having a good appearance.

According to a particular embodiment, the manufacturing method further comprises a step of spraying foam on said support followed by a step of a first determined duration during which the foam hardens.

According to another particular embodiment, the mold comprises an edge 3 ending in an acute angle, said edge delimiting all or part of the contour of the part to be manufactured, the method comprising a step of passing a roller from pressing the support being dried at the edge in order to cut it, said step of passing the roller occurring between the coating step and the step of spraying foam.

In this way, the cutting of the support is facilitated.

According to a particular embodiment, the method comprises a step of passing a sharp circular blade rolling on the support above a metal surface of the mold located at the periphery, said step of passing said blade intervening between the coating step and the foam projection step.

In this way, the cutting of the support is facilitated and the mold is not damaged by the cutting.

According to a particular embodiment, the foam is projected by a motorized arm moving to cover the internal surface of the mold, the speed of movement of the arm being a function of the thickness of foam to be obtained.

In this way, the thickness of the foam in the part being manufactured is easy to control.

According to a particular embodiment, the method comprises a step of placing fibers, such as glass fiber.

According to a particular embodiment, the method comprises a step of machining the hardened foam layer so as to make the surface smooth, the machining step occurring when the part is still in the mold.

According to a particular embodiment, the method comprises a step prior to that of coating the projection support with a mold base paint.

According to a particular embodiment, the thickness of the paint layer varies from 0.1 to 0.2 millimeter and in that the thickness of the support is greater than 1 millimeter.

According to a particular embodiment, the method comprises a preliminary step of coating the mold base with a release product.

According to a particular embodiment, the method comprises a step of treating the mold, such as plasma scanning, in order to give it semi-permanent mold release power.

4 4 LIST OF FIGURES Other characteristics and advantages of the invention will become apparent on reading the following description, given by way of indicative and non-limiting example, and the appended drawings, in which: FIG. 1 shows an example flowchart of the main steps for the implementation of an automotive parts manufacturing process; FIG. 2 is a diagram showing a mold intended to receive a liquid support and surrounded by a protective masking tape; Figure 3 shows a cross-sectional diagram of a device for cutting the medium using a roller; FIG. 4 is a diagram of a mold containing a part at the start of the spraying of the foam; FIG. 5 is a diagram of a mold containing a part at the end of the foam projection step; FIG. 6 represents a cross-sectional diagram of an automobile part produced by the method according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION In all the figures of this document, identical elements and steps 20 are designated by the same reference.

The general principle of the technique described is based on a process for manufacturing automotive parts consisting in depositing at the bottom of an open mold a support in liquid form which stiffens during drying and, once the support is dry, in extracting the part. thus manufactured from the mold.

The claimed manufacturing process also provides legal protection for the part manufactured by said process.

With reference to FIG. 1, a flowchart is presented listing the main steps for the implementation of a process for manufacturing automotive parts, according to an exemplary embodiment of the invention.

The parts are made from an open mold which defines the final dimensions of the part, on at least one side.

Initially and in step 1.1, the method comprises a step of cleaning the mold and in particular the parts which will be in contact with the part to be produced.

This step makes it possible in particular to eliminate impurities which might be visible during demolding.

The unused surfaces of the mold, which are generally located at the periphery of the part, are then covered with a mask strip making it possible to protect these zones from the coating of the support and from the projection of the foam (step 1.2).

This masking is advantageously carried out using an adhesive tape approximately 4 centimeters wide.

In step 1.3, a mold release agent is applied to the useful surface delimited by the masking tape.

This release agent limits the adhesion of the support coated in liquid form to the bottom of the mold and then stiffens during drying, which greatly facilitates the extraction of the part.

The application of the mold release agent is advantageously carried out by applying several layers with a waiting time between each layer to allow drying.

At the end of step 1.3, a polishing operation can be carried out, this operation improving the smooth and shiny appearance of the part 15 produced.

According to an alternative embodiment, the surface of the mold can undergo a treatment, such as plasma scanning, in order to give it semi-permanent mold release power.

Fig. 2 is a diagram showing an open mold intended to receive a liquid support and surrounded by a protective masking tape.

Once the release agent layer (s) has dried, the bottom of the mold can then be coated with a support in liquid form (step 1.4).

The support stiffens during drying and gives the finished exterior appearance of the part, this support must therefore respect technical characteristics of color, appearance (mat, satin gloss, ...), and impact resistance,. ...

The coating is carried out with a paint gun operated manually or with the aid of a robotic arm.

According to an alternative embodiment, the paint gun is stationary and it is the open mold which moves in front of it using robotic arms.

A single support layer may suffice, which in no way excludes, in the context of this invention, the provision of at least two layers, a first layer giving the apparent color of the part and a second constituting the support itself.

The thickness of the paint layer varies from 0.1 to 0.2 millimeter and that of the support, which is more resistant, is greater than 1 millimeter.

The material of the support is chosen for its mechanical characteristics (rigidity, impact resistance, elongation at break, etc.).

The optional paint layer allows great flexibility in color variation without adversely affecting the mechanical performance of the support, while exhibiting advantageous characteristics such as: resistance to ultraviolet rays, self-cleaning, etc.

In all cases, a drying time is to be expected following the coating of a layer so that the support stiffens and then becomes a "skin" in the jargon of those skilled in the art, this skin forms a surface resistant to shocks, chemicals and ultraviolet rays.

This skin may have a certain flexibility, requiring stiffening by the bonding of another material, such as expanded foam.

Drying can be accelerated by blowing an air knife (either hot air or air at room temperature).

In the case of parts requiring significant rigidity, the method comprises an optional step 1.5 of simultaneous projection of fibers and resin making it possible to produce a hard skin having mechanical characteristics that can be controlled according to the choice of resin, fibers and material. ratio (often expressed as a volume fraction of fiber and resin).

To replace the previously used polyester which takes a long time to dry, resin is used, and the fibers are made of glass or carbon.

During the step of drying the support, the skin is flexible enough to be easily cut to the precise dimensions of the part to be produced (step 1.6).

According to a first exemplary embodiment, illustrated by FIG. 3, the cutting is carried out by means of a cutting device using a roller 4 exerting pressure on the skin 3.

The mold 1 comprises a sharp edge 2 directed towards the outside of the mold, which is positioned precisely at the periphery of the part to be produced.

After coating, the skin 3 covers this ridge and extends on each side.

After the skin has dried, a roller 4 is applied to the level of the ridge.

Said roller 4 rotates around an axis 5 animated in rotation by vertically exerting a strong vertical pressure directed towards the skin.

Edge 2 is sharp enough to cut the skin under the pressure of the roller.

The shape of the ridge 2 allows the cut skin to be naturally pushed back beyond the ridge and facilitates its evacuation.

This trimming operation can advantageously be carried out by a robotic arm moving the roller 4 above the edge and ensuring constant pressure on the skin.

7 According to an alternative embodiment, the cutting is carried out by means of a thin and sharp circular blade rolling over the skin and exerting sufficient pressure to cut it.

In order not to damage the mold located below the cutting line, it has a metal surface of the mold with a width of a few 5 centimeters.

This circular blade is the same type as the pie and pizza rollers used in the kitchen.

After a certain time allowing the skin to harden (step 1.7), and according to a particular embodiment, a layer of expanded foam can be projected.

Fig. 4 shows a diagram of a mold containing a part at the start of the spraying 10 of foam.

You can see a bead of foam projected over a length of the bottom of the mold.

Step 1.7 can be implemented manually (which was the case during the testing and debugging steps).

It can advantageously be implemented by a robotic arm which controls the movements of a foam spray head 15 and which is integrated into an automobile parts production line.

According to an alternative embodiment, the spray head is fixedly mounted on a gantry and the mold moves in front of the head by robotic arms.

The expanded foam is applied by spraying at a constant rate throughout the operation, the relative speed of movement between the spray head and the mold being a function of the thickness of the foam to be obtained.

If the layer of foam exceeds a maximum thickness, it is necessary to carry out several passes and therefore to spray several layers of foam into the mold.

Experimentation has shown that it is not useful to wait for the complete drying of one coat before spraying the next, so that the time between two coats is shorter than that of completing the drying.

In this way, the overall manufacturing time of the part is thus reduced.

The foam increases the strength of the part to be produced and improves the insulation between the passenger compartment of a vehicle and its ambient environment (insulating foam).

Once cured, the foam becomes solid and can be machined.

According to an improvement, the foam can also be covered with a layer of material 30 to give a good appearance to the side opposite that of the skin, or to guarantee it better stability and good sealing.

This layer of finishing material 8 also makes it possible to stiffen the part by a sandwich effect: skin + foam + layer, and to ensure the dimensional stability of the parts by limiting the deformations due to the slow process of polymerization of the foam over time.

Fig. 5 is shown on a diagram of a mold containing a part at the end of step 1.7 of spraying the foam at the end of manufacture.

One can see in this figure the irregular appearance of the surface of the foam.

Once sprayed in one or more layers, the part is left to stand so that the foam expands and hardens (step 1.8), the hardening of the foam contributes greatly to the rigidity of the automotive part.

Being still in its mold, the part does not deform during this curing step.

The duration of this step varies depending on the thickness of the projected foam and the number of layers produced.

Experimentation has shown that for a layer of expanded foam 70 millimeters thick on average, it is necessary to carry out at least two layers.

In any case, the drying time of a layer which has just been sprayed depends on its thickness.

To improve the appearance of the foam surface and in particular to smooth its thickness, the method may include a machining step (step 1.9) using a milling cutter carried on a motorized arm for example, or with any another means, in particular abrasive, designed to remove material from the surface.

This step is advantageously carried out when the part is still in the mold, or when the part, once extracted, is then placed on a specific support.

When the foam is hardened, the part is removed from the mold (step 1.10).

The extraction is preferably carried out using compressed air ejection valves making it possible to exert a uniform pressure between the mold and the part thus produced and thus to avoid excessive mechanical stresses.

Any other means for extracting the part is also possible, for example the appropriate deformation of the mold in certain places to project the rigid part to the outside.

According to an improvement, inserts can be integrated into the part during step 1.7 of foam projection.

These inserts are wooden, metal or fiber rods making it possible to reinforce the stiffening of the automobile part.

Fig. 6 shows a sectional diagram of an automobile part produced by the method according to an exemplary embodiment of the invention.

The cut of the part thus manufactured comprises: a skin 10 comprising a support layer covered with a paint, a layer 11 of fiberglass or carbon coated with resin (optional), an optional layer 12 of expanded foam, obtained either by projection, or following the gluing of foam panels against the support, a layer 13 of finishing material (optional), one or more inserts 14 to stiffen the part (optional).

The steps of the process are advantageously implemented in a production line where the elements (mold, mold cleaning means, robotic arms for projecting the release agent, for coating the mold and for spraying the foam, blowing device for accelerating the drying, device for extracting and machining the part, etc.) are placed in an isolated island with an air renewal conditioning unit.

Although described through a number of detailed exemplary embodiments, the proposed method and the corresponding devices include different variants, modifications and improvements which will be evident to those skilled in the art, it being understood that these different variants , modifications and improvements are within the scope of the invention as defined by the claims which follow.

In addition, different aspects and features described above may be implemented together, or separately, or substituted for each other, and all of the different combinations and sub-combinations of aspects and features are within the scope of the 'invention.

Claims (11)

CLAIMS 1. A method of manufacturing parts intended to be installed in a vehicle, comprising the following successive steps: coating (1.4) of a support in liquid form on the inner wall .5 of an open mold followed by a step of drying said support with during which the support stiffens; removal (1.10) of the formed part after hardening of the support, 2. A method of manufacturing parts according to claim 1, characterized in that it further comprises a step of spraying (1.7) foam on said support followed by a step of a first determined duration during which the. foam hardens. 3. Process for manufacturing parts according to claim 2, characterized in that said mold comprises an edge terminating at an acute angle, said edge delimiting all or part of the contour of the part to be manufactured, the process comprising a step ( 1.6) passage of a roller pressing the support during drying at the level of the edge in order to cut it, said step of passage of the roller occurring between the coating step and the foam projection step 20 4. A method of manufacturing parts according to claim 2, characterized in that it comprises a step (1.6) of passing a sharp circular blade rolling on the support above a metal surface of the mold located at the periphery. , said step of passing said blade occurring between the coating step and the foam projection step 5. A method of manufacturing parts according to any one of claims 2 to 4, characterized in that the foam is projected by a motorized arm moving to cover the internal surface of the mold, the speed of movement of the arm being a function of l thickness of foam to be obtained. 11 6. A method of manufacturing parts according to any one of the preceding claims, characterized in that it carries a step (1.5) of placing fibers, such as fiberglass. Process for manufacturing parts according to any one of the preceding claims depending on Claim 2, characterized in that it comprises a step (1.9) of machining the hardened foam layer so as to make the surface smooth, said machining step occurring when the part is still in the mold or placed on a specific support. 8. A method of manufacturing parts according to any one of the preceding claims, characterized in that it comprises a step prior to that of coating the projection support with a mold base paint. 9. A method of manufacturing parts according to claim 8, characterized in that the thickness of the paint layer varies from 0.1 to 0.2 millimeter and in that the thickness of the support is greater than 1 millimeter. 10. A method of manufacturing parts according to any one of the preceding claims, characterized in that it comprises a prior step of coating the mold base with a release product. 11. A method of manufacturing parts according to any one of claims 1 to 9, characterized in that it comprises a step of treating the mold, such as plasma scanning, in order to give it a semi-mold release power. - permanent.