CN112643793A

CN112643793A - Method for cutting plastic film and related device

Info

Publication number: CN112643793A
Application number: CN202010500575.5A
Authority: CN
Inventors: 大卫·特雷斯
Original assignee: Plastic Omnium SE
Current assignee: Plastic Omnium SE
Priority date: 2019-10-10
Filing date: 2020-06-04
Publication date: 2021-04-13
Also published as: EP3804927A1; FR3101804A1; CN212859777U; FR3101804B1

Abstract

The present invention relates to a method and a related device for cutting plastic film sheets, in particular for cutting plastic film sheets arranged on bodywork parts for masking or decoration, comprising a sonotrode mounted on a controlled mechanism, the sonotrode of the device having a cutting end with a flat and provided partial element forming a protuberance projecting from the flat surface by a height substantially equal to the thickness of the film sheet, the partial element forming the protuberance being free to move. The invention also relates to a method using the device.

Description

Method for cutting plastic film and related device

Technical Field

The present invention relates to the field of decoration or treatment of motor vehicle body parts. More specifically, the invention relates to a method for cutting a plastic film sheet pre-arranged on a vehicle body part. Such plastic films can be used in particular for partial covering before subsequent finishing operations or assembly operations, or for decorating vehicle body parts. Such masking may be intended, for example, to protect an area from paint or to preserve future adhesive traces.

Background

For example, it is known to use masking techniques (also known as masking) to delineate areas to be painted and areas not to be painted from automobile parts.

The masking operation is intended to arrange small-sized membranes at some locations on the part to be painted. This placement process is complicated and is typically done manually. In order to obtain a certain precision, at least one edge of the masking film or tape must be very precisely positioned at the boundary of the area along reliefs or embossments (embossments) of the component, such as grooves, sculpted edges, natural edges of the component. However, it is difficult or even impossible to arrange a large sheet of masking film on a vehicle body member by obtaining high positioning accuracy because the masking film is flexible and can generate wrinkles. A robot may be used to position the masking film strip or the masking film sheet so as to have an accurate frame of reference relative to the part to be masked. Positioning the sheets of film using a robot is also complicated in view of the flexibility of the film and the formation of wrinkles.

However, the requirements regarding the quality of the painted surface require a very clear and flawless transition. The positional tolerance of the boundary between the painted and unpainted areas is therefore very small, about +/-0.1 mm.

This requirement is not compatible with known positioning devices. Therefore, there is no method to perform very precise large area shading of a vehicle body part by obtaining a precise (clear) shading boundary without significant irregularities to define the following two areas: one area decorated by the film, one area not decorated, or when the ending operation is a painting operation, one is the area to be painted and one is the area not to be painted.

This situation can be improved.

Disclosure of Invention

The aim of the invention is in particular to improve the cutting accuracy of plastic films, in particular in the case of masking operations carried out before painting of automobile parts.

The present invention relates to an ultrasonic device for the "in situ" cutting of a plastic film web after it has been laid on a vehicle body part, comprising a sonotrode capable of being mounted on a controlled mechanism, the cutting end of the sonotrode having a substantially flat surface forming the bottom of a partial element provided with a forming protuberance (or bulge) whose height protruding from the flat surface is substantially equal to the thickness of the film web, the partial element forming the protuberance ideally being able to move freely.

The ultrasonic device for cutting a membrane may also comprise one or more of the following features considered alone or in combination:

the local element forming the projection is a wire that is free to move (rotate) under the sonotrode, which advantageously enables a positioning that is automatically tangent to the predetermined cutting trajectory and which brings about a high cutting precision.

The diameter of the wire is between 50 and 400 microns. The reduced diameter wire is therefore flexible and becomes movable and freely orientable under the sonotrode, which also gives it a flexible and resistive feature suitable for ultrasonic cutting.

The device is configured to effect renewal of the wire by automatically unwinding the spool, the unwinding being continuous or discontinuous. Advantageously, this makes it possible to renew the portion of wire that is cut through the plastic film sheet by ultrasound after a predetermined number of component cuts, and avoids cutting operations with excessively worn wire portions.

The invention also relates to a method for cutting a plastic film web arranged on a component by means of a device as described above. Thus, the plastic film is cut directly on the part, rather than pre-cut on the cutting frame or anvil, which has the advantage of avoiding transfer. It is thus possible to cut plastic films of the same thickness as the filaments, which is of particular interest for masking in applications relating to the painting of automotive parts.

The method for cutting plastic film sheets according to the invention may also comprise one or more of the following characteristics considered alone or in combination:

the method includes disposing a plastic film sheet for masking on the part prior to relative movement of the sonotrode and the part along a predetermined cutting path.

The method uses a wire having a diameter substantially equal to the thickness of the plastic film sheet. Thus, in addition to allowing a high cutting precision to be obtained, the correspondence between the diameter of the wire and the thickness of the piece of material to be cut makes it possible to easily and quickly remove debris inside or outside the contour of the part formed after cutting, or more broadly, those portions of the film sheet that are not useful for masking.

The method uses a wire having a diameter greater than the thickness of the plastic film. In the case of applications relating to painting of the support part, it is therefore possible to form in the support part a groove of depth less than the diameter of the wire, corresponding to the profile of the covering formed after cutting, which groove better delimits the painted areas from the unpainted areas.

The method uses filaments having a length of between 8 and 15mm, preferably 10 mm. Such a length advantageously gives the wire great flexibility and great mobility with respect to its diameter, so as to optimize the free positioning of the tangent along the predetermined cutting trajectory.

The method comprises the following steps: in the case of masking operations or overmoulding, the cut film is removed, the part is painted or glued, the remaining film is removed, or in the case where the cut film remains on the part for decorative purposes, a varnish is applied to the cut film.

Finally, the invention relates to a body part obtained by the cutting method as described above, comprising a cut plastic film and/or a groove hollowed out along a predetermined trajectory.

Drawings

The invention will be better understood from reading the following description, given purely by way of example and without limiting features, and made with reference to the accompanying drawings, in which:

fig. 1 shows a device for cutting plastic film sheets according to a specific and non-limiting embodiment of the present invention.

Fig. 2 shows a sonotrode included in the cutting device shown in fig. 1, which sonotrode is located in the vicinity of a body part on which a plastic film to be cut is arranged.

Fig. 3a shows the sonotrode, already shown in fig. 2, in a cutting operation of a film web arranged on a body part.

Fig. 3b shows the sonotrode, the part, the plastic membrane at the end of the cutting operation of the plastic membrane, which have been shown in fig. 2 and 3 a.

Fig. 4 shows an example of a body part and a cutting path of a plastic film for shading purposes.

Fig. 5 shows a step of arranging a shading membrane on the body part already shown in fig. 4.

Fig. 6 shows the step of painting the area of the body part already shown in fig. 4 and 5 after removing the cut part of the plastic masking film.

Fig. 7 shows the body part already shown in fig. 4 to 6, which is partially painted after the cut-out section of the shading film has been removed.

Fig. 8 shows a comparison of the position of the cutting element according to the prior art (8a) and the invention (8b) along a predetermined trajectory, depending on whether the cutting element is rectangular or freely rotationally movable.

Detailed Description

Fig. 1 shows a device 1 for cutting a plastic film web 3 arranged on a body part 5. The device 1 for cutting comprises a sonotrode 7 moved by a robot 9. The sonotrode 7 is generally made of metal, such as titanium, aluminum or steel, or any other material suitable for its function. The sonotrode 7 may or may not have been heat treated. It is configured to release vibrational energy at its distal end.

The sonotrode 7 has a longitudinal axis 71, which longitudinal axis 71 is substantially perpendicular to the component during cutting. The cut end 73 of the sonotrode 7 (visible in figures 2, 3a and 3 b) has a plane or substantially flat surface which is cleverly provided with a partial element 11, which partial element 11 forms a protrusion which protrudes below the flat surface by a height substantially equal to the thickness of the plastic film web 3. According to a preferred embodiment of the invention, the element 11 is a metal cutting strip or wire segment freely movable in angular orientation in space around the longitudinal axis 71 of the sonotrode 7. The term "cutting bar" is understood herein to mean the active/protruding portion below the bottom of the sonotrode. The wire may be made of, for example, copper, and may be wound on a spool. According to a variant of this embodiment, the cutting strip (element 11) has axial symmetry with respect to the axis 71 and has, for example, the shape of a pin, tenon or hemisphere and, with respect to a flat or substantially flat cutting surface, a height equal to the thickness of the plastic film 3. Thus, in both embodiments, the element 11 is angularly positioned in a manner that is non-differentiated as to the shape of the cutting trajectory, without having to fix this angular position by specific control of the controlled mechanism (robot).

During the cutting operation, vibrations in the form of ultrasound are transmitted to the sonotrode 7 until into the element 11, which element 11 forms a protrusion on the flat or substantially flat surface of the cutting end 73. When the cutting end 73 is positioned in contact with the membrane 3, the vibrations transmitted to the element 11 forming the projection generate a thermal effect, cutting the membrane 3 arranged on the bodywork part 5.

The robot 9 thus moves the element 11 along a predetermined trajectory, for example the trajectory 13, and cuts the plastic film web 3 arranged on the body part 5 according to this trajectory. The various actuators of the robot 9 for initiating the movement are not shown, as they are not useful for understanding the invention. For example, it may be a common industrial robot carrying the sonotrode 7.

Advantageously, the use of the element 11 forming a protrusion on the flat surface of the cutting end 73 of the sonotrode 7 enables to escape from the situation in which the orientation of the cutting tool (for example a rectangular knife or blade) has to be controlled in order to follow a predetermined cutting trajectory. Thus, the cutting accuracy is improved and the robot 9 is simplified, since it is not necessary to control the movement of the element 11 forming the cutting tool about the longitudinal axis 71 of the sonotrode 7. The respective advantages will be explained by a detailed description of fig. 8.

The cutting accuracy is obtained by the positioning accuracy caused only by the robot and by the sharpness of the cut made locally by the element 11 (caused, for example, by the fineness of the wire and its free positioning when the element 11 is a portion of wire).

According to a preferred embodiment of the invention, the sonotrode 7' is configured to operate at a frequency between 20 and 120KHz, preferably between 50 and 90KHz, more preferably at 70KHz or very close to 70KHz, and the element 11 is a length of copper wire having a diameter between 50 and 400 microns and a length between 5 and 20 mm, preferably between 8 and 15mm, more preferably equal to 10 mm.

The term "length of the wire segment" is understood herein to mean the length of the portion of the wire located between the flat or substantially flat surface of the cutting end 73 of the sonotrode 7 and the end of the wire segment. This portion of the wire is free to move. The wire thus has mobility, flexibility, length and diameter about the longitudinal axis 71 of the sonotrode 7, so that the resulting fineness of the cut is increased.

The movability of the partial elements 11 made in the form of small-diameter wires is particularly advantageous because it gives the cutting element 11 the ability to be freely positioned tangentially to the intended cutting trajectory, i.e. the trajectory 13 in the example shown in fig. 1.

The cutting precision thus obtained is particularly suitable for finishing operations or assembly operations of automotive parts, such as masking operations carried out before painting the part 5 shown in fig. 1. It often happens that the appearance element has one or more areas that must be protected and these areas must remain unpainted. This is the case, for example, for areas which are desired to be transparent, allowing backlighting to be achieved, or for areas for carrying decorative elements, or for fixing one appearance piece to another by gluing. Thus, for example, it must be possible to very precisely delimit painted and unpainted areas.

As shown in fig. 1, the device 1 according to the invention is particularly suitable for screening operations intended to define such areas.

The screening method according to the invention consists in using the device 1 to cut the plastic screening film 3 so as to define the area outside the predetermined trajectory 13 as the area to be painted, the area inside the trajectory 13 as the area not to be painted, or vice versa. Depending on whether the area to be painted is inside or outside the closed track 13, the part of the cut masking film 3 to be removed before the painting is inside or outside the track 13.

The use of the device 1 for cutting a plastic film 3 arranged on a motor vehicle part 5 comprises the following preliminary steps: one (or more) large-sized plastic film sheets 3 are arranged, which can cover one (or more) areas on the surface of the component 5 in a large-area, coherent integration, and the sonotrodes 7 are then displaced relative to the component 5 on the visible surface of the component 5, so that the protrusion-forming elements 11 follow a predetermined trajectory 13 (which is a cutting trajectory) on the plastic film sheets 3. The plastic film 3 can be arranged by gluing or by using an electrostatic effect which keeps the plastic film 3 stationary on the part 5. The plastic film web is usually a length of almost rectangular film that is released and disposed directly from the dispensing roller and then cut to length when the area to be protected is completely covered. Thus, the film can be cut into sheets along the width of the roll without taking other precautions. The precise cutting of the sheet along the predetermined trajectory 13 is then completed by the movement of the sonotrode 7 along the predetermined cutting trajectory 13. During the step of relative movement of the sonotrode 7 and the part 5, the flat or substantially flat cutting end 73 remains in contact with the plastic film web 3, so that the local elements 11 forming the protrusions cut the film web 3 along the trajectory 13. The cutting is effected by local heating of the plastic film web 3 caused by the vibration of the protrusion-forming elements 11. Cutting can be effected over the entire thickness of the plastic film web by cleverly using a wire having a diameter equal to the thickness of the plastic film web 3, or by cleverly using a hemisphere protruding from the flat cutting surface of the cutting end 73. Such cutting offers the advantage that parts of the film web not intended to be masked in the step of spraying the lacquer can be removed easily and without difficulty.

According to a variant of the above-described cutting method, a wire is used having a diameter greater than the thickness of the plastic film web 3, which wire, in addition to cutting the plastic film web 3 precisely, has the following effect: the recess 15 is formed in the body part 5 by heating the thermoplastic material of the body part 5 under the influence of vibrations (the recess 15 is visible in fig. 3 b). Advantageously, the grooves 15 thus formed along the predetermined trajectory 13 allow to further better delimit the painted areas and the unpainted areas, since they are able to slightly absorb the paint and therefore limit the spreading of the paint out of the grooves 15 by capillary action.

According to a variant of the embodiment of the invention, the step of smoothing the plastic film 3 is performed before the step of relatively moving the sonotrode and the body part 5. This smoothing step is carried out, for example, by means of a robot equipped with smoothing means which are placed on the part and which follow a predetermined trajectory 13 in order to remove or lighten defects which may occur during the laying of the plastic film 3 on the bodywork part 5. These defects may be, for example, wrinkles, bubbles. A robot or any other equivalent actuator provided for this purpose, for example a smoothing device of the type with pads, brushes or boluses, the flexibility of which is capable of crushing bubbles, smoothing out wrinkles or pressing against the plastic film without risking damaging it.

According to a variant of embodiment of the invention, the device 1 for cutting the plastic film web 3 used in the cutting process comprises means for replacing the useful part of the wire constituting the protruding element 11. The means for replacing the useful portion of the wire may be activated manually or automatically. In case of automatic activation of the means for replacing the useful portion of the wire, i.e. the cutting strip, the means may be adapted to release the wire continuously or discontinuously. The wire may be released towards the flat or substantially flat surface of the cutting end 73 of the sonotrode 7 by means of a groove (or dispensing channel) dug longitudinally or obliquely in the end of the sonotrode 7 and leading to the outside of the sonotrode 7, for example to the reel of an automatically controlled unreeling machine. The wire releasing means may be combined with the cutting means of the cutting wire to cut away the used portion. Thus, it is possible to renew the wire portion forming the projection after one or more cutting operations and to maintain the cutting accuracy by using the wire portion not worn by the cutting operation.

Fig. 2 shows a sonotrode 7 for use with the cutting device 1 according to the invention, which sonotrode 7 is located in the immediate vicinity of a body part 5, on which body part 5 a plastic membrane 3 is arranged, the dimensions of which are greater than those of the part 5. The cutting end 73 of the sonotrode 7 has a partial element 11 which lies on the flat surface of the cutting end 73 and forms a protrusion on this surface. The element 11 is a wire (visible in fig. 3 a) located in a supply channel inside the sonotrode, such that the wire is positioned perpendicular to or inclined with respect to the cutting surface of the cutting end 73 where the wire emerges from a groove in the sonotrode. The wire is then automatically placed parallel to the surface of the component and is naturally oriented in the direction forming the tangent to the cutting trajectory during the movement of the sonotrode 7. In fact, the length, diameter and flexibility characteristics are neatly defined so that during the relative movement of the sonotrode 7 and the part 5, the surface of the sonotrode 7 is in contact with the plastic membrane 3, the wire is free to move around the longitudinal axis 71 and is positioned freely in a manner tangential to the trajectory undergone by the cutting end 73 of the sonotrode 7, which cutting end 73 cuts the plastic membrane 3 due to the vibrations caused by the transducer 7' (the sonotrode coupled to the sonotrode 7).

Fig. 3a shows the sonotrode 7 already shown in fig. 2 during the cutting operation of the plastic film web 3. The flat or substantially flat surface of the cutting end 73 is kept in contact with the plastic film web 3, and the local element 11 forming a protrusion, which moves in oscillation, cuts the film web 3 by locally heating the film web 3. Fig. 3a shows a partial cross-sectional view of the end of the sonotrode 7, showing the internal groove (or wire feed channel) opening onto the periphery of the sonotrode. According to an alternative embodiment of the invention, the element 11 may remain locked in a groove allowing its positioning, or may be released continuously or discontinuously by means of a filament pay-off device not shown in fig. 3a, wherein the filament pay-off device is adapted to slide the filament in the wire feed channel of the sonotrode 7. In this figure it can be seen that the partial elements 11 forming the protrusions effect a cut in the thickness of the plastic film web 3.

According to a variant of the embodiment of the invention, there is a wire feed channel that is not perpendicular to the flat or substantially flat surface 73 of the sonotrode (bottom), but at an angle of about 10 to 40 degrees to the surface 73 of the sonotrode 7. Advantageously, this enables the portion of wire forming the protrusion useful for cutting the plastic film sheet to be protected from mechanical stress (bending, twisting, etc.) when the predetermined trajectory 13 follows the main direction, without too sharp a convolution or turn.

The wire feed channel, so inclined and without an elbow inside the sonotrode, prevents the wire from bending too much and makes the "natural" positioning of the wire along the predetermined trajectory 13 easier.

Fig. 3b shows the sonotrode 7 at the end of the cutting operation by relative movement of the sonotrode 7 and the part 5, slightly set back from the part 5 on which the plastic film 3 is arranged, wherein the sonotrode is kept in contact with the plastic film 3 along a predetermined cutting trajectory during the cutting operation. We can see the recess 15 formed in the thickness of the plastic film 3 by the local element 11 forming a protrusion. In this way, the groove, after cutting, defines two portions of the plastic film 3, one or other of which can be removed quickly and easily from the component by a simple manual removal operation. Thus, the shutter can be removed in its entirety without breaking.

Fig. 4 shows an example of a body part 5 of a motor vehicle, and an example of a predetermined cutting trajectory 13, the predetermined cutting trajectory 13 being defined to perform a masking, defining an area to be painted outside the trajectory 13 and an area to be protected from painting inside the trajectory 13. The cutting path of the plastic film web arranged for masking purposes therefore corresponds to the boundary of the painted area with respect to the unpainted area.

Fig. 5, 6 and 7 show successive steps of painting the body part 5 (the skin of the bumper) by implementing a masking using the cutting method according to the invention. The cutting method according to the invention uses the device 1 shown in fig. 1. The body part 5 is the part already shown in fig. 4. Fig. 5 shows the body part 5 after the plastic film 3 has been arranged over the entire part (the plastic film 3 is shown here as transparent). Fig. 6 shows the part being painted on the area to be painted after cutting the plastic film web 3 along the predetermined cutting trajectory 13 and removing the part of the plastic film web outside the cutting trajectory 13. The part of the plastic film 3 remaining after the removal of the part outside the track 13 effects a masking which makes it possible to protect the regions of the body part 5 other than the region to be painted (i.e. the regions which are each also covered by a portion of the plastic film, in this figure appearing "zigzag") from being painted. Fig. 7 shows the body part 5 after removal of the remaining part (in a "zig-zag" shape) from the plastic film 3 of the body part, which shows a clear demarcation between the painted and unpainted areas along a predetermined trajectory.

Fig. 8 shows the successive positions of the cutting element along the predetermined cutting trajectory 13, which differ depending on whether the cutting element has an elongated or rectangular cutting shape (element 110) or is freely movable (element 11). The sonotrode 7 is carried by an arm 91 of the robot 9. The connection between the arm 91 of the robot 9 and the sonotrode 7 is not articulated. The portion of figure 8 on the left side, labelled 8a, shows the successive positions of the rectangular cutting element 110, which cutting element 110 must rotate in order to adopt a position tangential to the trajectory 13. The continuous orientation of the arm 91 of the robot shows that it is necessary to position the arm 91 and thus the sonotrode 7 so that the cutting element 110 has a position oriented along a tangent to the trajectory 13. This configuration corresponding to the cutting tools of the prior art does not allow to follow curves (turns) precisely. The part marked 8b on the right-hand side of figure 8 shows the successive positions of a cutting wire whose properties allow it to move freely and thus to be positioned freely when the sonotrode carrying the cutting wire is subjected to a predetermined cutting trajectory 13. The cutting element is of the kind "don't care" for the shape of the predetermined trajectory 13. This is the case for a cutting wire type element, but it is also the case when the element forms a protrusion that is symmetrical about any axis perpendicular to the longitudinal axis of the sonotrode 7 (i.e. a hemisphere, a pin or a tenon, for example). In this case, the arm 91 of the robot 9 can maintain the same orientation along the predetermined cutting trajectory 13. Thus, in addition to the high cutting accuracy achieved due to the cutting device 1 according to the present invention and the cutting method using the cutting device 1, it is advantageously possible to eliminate the need to control an additional movement, i.e., the rotational movement of the cutting tool 110, in order to conform the tangential position of the cutting tool to the predetermined cutting trajectory 13.

The invention is not limited to cutting methods for carrying out masking operations, but also includes other operations, such as decorating or preparing parts for assembly. The plastic film 3 can thus be cut, for example, from a decorative film and/or a luminescent film which remains on the vehicle body part.

The plastic film can be made into a usable roll of constant width (and having predetermined dimensions). It is conceivable that the plastic film can be arranged, in particular, by gluing or that the plastic film is held on the body part by means of electrostatic effects. Its use and cutting can be designed for the purpose of overmoulding from another plastic, in particular a translucent material, to prepare a decorative element of a vehicle body part.

In other words, the device 1 according to the invention is suitable for the precise cutting of plastic film webs 3 arranged on a body part 5. The device 1 comprises a sonotrode 7 which is moved vibrationally by means of a sonotrode 7'. The sonotrode 7 is mounted on a controlled mechanism 9 (robot). The cutting end of the sonotrode 7 of the device 1 for cutting plastic film webs 3, which has a flat surface 73 (also called "bottom"), is provided with local elements 11 forming projections, the height of which elements 11 above the flat surface is substantially equal to the thickness of the plastic film web 3. The partial elements 11 forming the projection are ideally free to move, in particular about the longitudinal axis 71 of the sonotrode 7. According to a preferred embodiment of the invention, the local element 11 forming the protrusion is a metal wire, for example made of copper, with a diameter comprised between 50 and 400 microns. The device 1 may comprise a device configured to effect renewal of the portions of wire forming the protrusions by automatically unwinding the coil continuously or discontinuously.

The cutting method according to the invention for cutting a plastic film web 3 arranged on a component 5 by means of a device 1 comprises:

a plastic film 3 serving as a masking film is arranged on the component 5; and

the sonotrode 7 and the part 5 are made to perform a relative movement along a predetermined cutting trajectory 13, the cutting end 73 of the sonotrode remaining in contact with the plastic film 3 during the movement along the trajectory 13.

The method according to the invention may use a wire having a diameter substantially equal to the thickness of the plastic film 3 or a wire having a diameter greater than the thickness of the plastic film 3. In the case of using a metal wire with a diameter greater than the thickness of the plastic film 3, the implementation of the method advantageously allows the formation of the groove 15 in the part 5 where the plastic film 3 is arranged.

Advantageously, the method for cutting the plastic film sheet 3 uses a wire having a length of between 8 and 15mm, preferably 10 mm.

According to a variant of the method, the preceding step of unit geometric calibration (registration g from three unit) is performed before the step of relative movement of the sonotrode 7 and the part 5.

The invention also relates to a body part 5 obtained by the above method, which body part 5 comprises a groove corresponding to a predetermined cutting trajectory and/or a portion of plastic film, which portion is or is not overmolded and is used, for example, for decorative purposes. Advantageously, the body component obtained by implementing the method according to the invention can be free of any reliefs of the embossing (embossage), groove, rib (ar e), sculpting rib (ar e de style) type on the predetermined cutting trajectory 13, since it is not necessary to position by such shapes arranged on the visible surface of the component in order to define precisely the cutting trajectory, including when the cutting trajectory is positioned "full skin" on the body component.

The invention is not limited solely to the embodiments described above but relates more generally to any device for cutting plastic films or plastic film sheets arranged on a component, which device comprises a sonotrode mounted on a controlled mechanism, such as a robot, having a cutting end with a flat surface (bottom) provided with a partial element forming a protrusion protruding from the flat surface at a height substantially equal to the thickness of the plastic film or film sheet, the partial element forming a protrusion and being in the shape of a pin, tenon, hemisphere or ideally free to move, such as a wire.

List of reference numerals:

1: cutting device

3: plastic film

5: vehicle body component

7: ultrasonic welding electrode

7': ultrasonic generator

9: robot

11: cutting element forming a protrusion

13: predetermined cutting trajectory

15: a recess formed in the vehicle body component.

Claims

1. A device (1) for cutting plastic film webs (3) arranged on vehicle body parts (5), comprising a sonotrode (7), the device (1) being characterized in that the sonotrode (7) has a cutting end (73) with a flat surface provided with local elements (11) forming projections which project from the flat surface by a height substantially equal to the thickness of the plastic film web (3), the local elements (11) forming projections being free to move.

2. Device (1) according to claim 1, wherein the protrusion-forming elements (11) are wires.

3. Device (1) according to claim 2, wherein the diameter of the wire is between 50 and 400 microns.

4. The device (1) according to claim 3, configured to effect renewal of the wire by automatically unwinding a reel.

5. A method for cutting a plastic film web (3) arranged on a component (5), which method is carried out with a device (1) as claimed in any one of claims 2 to 4.

6. The method of claim 5, wherein:

a plastic membrane (3) is arranged on the component (5),

-relatively moving the sonotrode (7) and the part (5) along a predetermined cutting trajectory (13).

7. Method for cutting a plastic film sheet (3) according to any one of claims 5 and 6, wherein the diameter of the filaments is substantially equal to the thickness of the plastic film sheet (3).

8. Method for cutting a plastic film sheet (3) according to any one of claims 5 and 6, wherein the diameter of the filaments is greater than the thickness of the plastic film sheet (3).

9. Method for cutting a plastic film sheet (3) according to any one of claims 5 to 8, the length of the filaments being between 8 and 15mm, preferably 10 mm.

10. Method for cutting a plastic film sheet (3) according to any one of claims 5 to 9, comprising a preliminary step of unit geometric calibration before the relative movement step of the sonotrode (7) and the part (5).

11. A vehicle body component (5) comprising a cut plastic film and/or a groove (15) hollowed out along a predetermined trajectory (13), said vehicle body component (5) being obtained by a cutting method according to any one of claims 5 to 10.

12. The body component (5) according to claim 11, which is free of any embossing, grooving, ribbing or ribbing type reliefs along said predetermined trajectory (13).