FIBER PLACEMENT MACHINE WITH SPECIAL LASER HEATING MEANS

Abstract

The present invention relates in particular to a fiber placement machine comprising a fiber placement head with a compaction roller, and laser heating means comprising several laser devices, each including a laser source and an optical system. Each optical system is capable of forming an elementary laser spot at a working plane in the pinch zone, having a width in a longitudinal direction parallel to the roller axis, and having in the longitudinal direction an elementary intensity profile (71-78) of the flat-plate type, comprising an elementary central plate (711-718) and two lateral edges (721-728). Adjacent elementary laser spots overlap, at least partially, outside their elementary central plates, each elementary central plate being located at the level of a fiber, with at least one elementary central plate being located on each fiber.(Figure for the abbreviation: [Figure 6]).

Description

Title of the invention: FIBER PLACEMENT MACHINE WITH SPECIAL LASER HEATING MEANS

[0001] The present invention relates to a fiber placement machine for producing composite material parts, and more particularly to a fiber placement machine comprising particular laser heating means. The present invention also relates to a method for manufacturing composite material parts by means of a corresponding fiber placement machine.

[0002] Fiber placement machines are known for the contact application on a draping tool, such as a male or female mold, of a wide strip formed of one or more continuous flat fibers, of the wick type, dry or impregnated with thermosetting or thermoplastic resin, in particular carbon fibers, consisting of a multitude of carbon threads or filaments.

[0003] These fiber placement machines conventionally comprise a placement head, a movement system capable of moving the placement head, and storage means for storing the fibers in the form of reels. The fiber storage means may be mounted on the head, or be arranged at a distance from the head. The head conventionally comprises a compacting system comprising at least one compacting roller for applying a strip formed of several fibers to an application surface of a draping tool, a guiding system for guiding the fibers in the form of a strip towards said compacting roller, and for each fiber, cutting means for cutting a fiber, rerouting means for rerouting the fiber to the compacting roller after a cut made by the cutting means, and blocking means for blocking the fiber that has just been cut.The compacting roller presses the fiber strip against the application surface of the mold, or against the previously deposited fiber strip(s), in order to facilitate the adhesion of the deposited strips to each other, as well as to gradually evacuate the air trapped between the deposited strips.

[0004] Heating means provide heating of the strip of fibers to be applied, and / or of the mold or strips already applied upstream of the compacting roller, just before compacting the strip, in order to at least soften the resin, and thus promote adhesion of the strips to each other. In the case of thermosetting resins, the pre-impregnated fibers are simply heated to soften them, typically at temperatures of the order of 40°C. The heating means typically comprise one or more infrared lamps. In the case of thermoplastic resins, the pre-impregnated fibers must be heated to higher temperatures, at least up to the melting temperature of the resin, i.e. around 200°C for nylon type resins, and up to around 400°C for PEEK type resins. The heating means conventionally comprise a remote laser source and an optical system mounted on the head, connected to the source by an optical fiber and capable of forming a laser beam in the direction of the pinching zone between the roller and the application surface extending over the entire width of the strip.

[0005] In particular, in patent document US2021 / 0206123, laser heating means have been proposed comprising several laser devices, each laser device being capable of emitting a laser beam towards the pinching zone between the roller and the application surface, each laser device comprising a laser source and an optical system mounted on the head for shaping the laser beam, a control unit capable of controlling the laser devices independently of each other. The machine may comprise one laser device per fiber, each laser device being activated only when the fiber associated with said laser device is present in the strip. Such heating means have been proposed in order to avoid heating of the fibers already applied when a fiber of the strip is not applied, and to limit the risks of winding of said fibers already applied on the compacting roller.The proposed laser devices use low-power laser sources, of the order of 200W for a 12.7 mm (1 / 2 inch) fiber, allowing the layup of fibers pre-impregnated with thermosetting resin at high speeds, and the layup of fibers pre-impregnated with thermoplastic resin at reduced speeds. In one exemplary embodiment, each laser device associated with a fiber forms a laser spot that extends over the adjacent fibers. When two adjacent fibers are applied, the laser spots overlap. The fibers are therefore not heated uniformly across their entire width, and it is difficult to obtain controlled consolidation in the case of thermoplastic resin. Furthermore, the overlapping of the laser spots can lead to overheating of the fibers along their adjacent longitudinal edges. In another embodiment, the laser spot has a width less than the width of the fibers.In such a case, the fibers are not heated over their entire width, resulting in non-uniform adhesion of the individual plies in the case of thermosetting resins or non-uniform consolidation in the case of thermoplastic resins.

[0006] The aim of the present invention is to propose a solution aimed at overcoming at least one of the aforementioned drawbacks.

[0007] To this end, the present invention proposes a fiber placement machine for producing parts from composite material by applying strips formed from several continuous fibers arranged side by side comprising - a fiber placement head, comprising at least one compacting roller of longitudinal axis capable of applying several fibers side by side on an application surface, and for each fiber, cutting means and rerouting means, and preferably blocking means, - laser heating means comprising several laser devices, each laser device being capable of emitting a laser beam in the direction of the pinching zone between the compacting roller and the application surface, each laser device comprising a laser source and an optical system mounted on the placement head, upstream of the compacting roller relative to the direction of advancement of the head during draping, for shaping the laser beam, and - a control unit capable of controlling the laser devices independently of each other, characterized in that each optical system is capable of forming an elementary laser spot, preferably substantially rectangular, at a working plane in the pinching zone, said elementary laser spot having a width in a longitudinal direction parallel to the axis of the roller, and having in the longitudinal direction an elementary intensity profile of the flat plate type, comprising an elementary central plate and two lateral edges, said optical systems being arranged and defined so that at the working plane, the adjacent elementary laser spots overlap outside their elementary central plates, at least partially by their lateral edges, each elementary central plate is arranged at a fiber, at least one elementary central plate being arranged on each fiber.

[0008] According to the invention, each optical system is capable of forming an elementary task having an intensity profile across the width of the strip of the flat plate type, called "top-hat" according to the English expression usually used, the elementary laser tasks overlapping only by their longitudinal edges, so that, when all the laser sources are activated, the adjacent elementary laser tasks overlap without causing harmful overheating, the overlap being able to be defined so that the intensity of the combined laser task in the longitudinal direction is substantially constant over the entire width of the strip.The heating means according to the invention may in particular comprise high power laser sources, for example more than 500W, allowing the draping of fibers pre-impregnated with thermoplastic resin at high speeds, for example up to 1 m / s depending on the type of adhesion or consolidation sought, with substantially uniform heating over the entire width of the fibers. The elementary central plates are arranged at the level of the fibers, and not straddling two fibers, the heating means can thus be activated or deactivated depending on the presence of fiber or not, the heating means according to the invention thus allowing, in particular during the draping of pre-impregnated fibers. impregnated with thermoplastic resin at high temperatures, to avoid overheating of the substrate and / or the compacting roller.

[0009] The elementary laser tasks are preferably substantially rectangular, at a work plane in the pinching zone, each elementary laser task having a width in a first longitudinal direction parallel to the axis of the roller, and a height in a second direction perpendicular to the first direction. According to another embodiment, the elementary laser tasks are of substantially circular shape at the work plane.

[0010] The fibers used are continuous flat fibers, also called rovings, generally unidirectional, and comprising a multitude of filaments. The deposited fibers may be dry fibers provided with a binder in the form of powder and / or veil(s), or fibers pre-impregnated with thermosetting or thermoplastic resin. The fibers typically have widths of 6.35 mm or 12.7 mm wide (1 / 4 or 1 / 2 inch). In the present, the term "fibers" also designates fibers of greater width, greater than 12.7 mm, conventionally called strip in placement technology. The heating means according to the invention prove to be particularly advantageous for the application of fibers provided with a thermoplastic binder or pre-impregnated with a thermoplastic resin.The continuous fibers applied are for example carbon fibers, glass fibers or synthetic fibers, for example 6.35 mm or 12.7 mm wide, the fibers being pre-impregnated with a thermoplastic polymer for example chosen from the group consisting of polyamides, polyesters such as polyethylene terephthalate, polyethersulfones, polyether-retherketones, polyphenylene sulfides, polyurethanes, epoxies, polyolefins, polylactic acid, or a mixture of one or more of these polymers.

[0011] According to one embodiment, at the level of the working plane, the adjacent elementary laser tasks overlap substantially entirely by their lateral edges, so that, when the laser sources are controlled in power to obtain elementary central plateaus substantially at the same intensity level, the combined laser task, formed by the combination of the elementary laser tasks, has a combined intensity profile with a flat plateau, with a combined central plateau.

[0012] According to one embodiment, the laser heating means comprise a row of optical systems formed by central optical systems arranged between two lateral optical systems, the central optical systems being capable of forming substantially identical elementary laser tasks having in the longitudinal direction a width Lb with elementary central plates of width L'b the lateral optical systems being capable of forming substantially identical elementary laser tasks, having in the longitudinal direction a width L2 greater than the width Li, with central plates of width L'2 greater than the width L'i. Preferably, for all optical systems, the lateral edges of the elementary intensity profiles extend in the longitudinal direction over the same width L”. Since the outer fibers of the strip cannot benefit from an overlap of elementary tasks at their outer longitudinal edge, the use of specific optical systems at the end makes it possible to guarantee sufficient heating of the outer fibers of the strip over their entire width.

[0013] According to one embodiment, the control unit is capable of controlling the laser sources associated with the central optical systems at a first power and the laser sources associated with the lateral optical systems at a second power greater than the first power, so that the elementary central plates of the corresponding elementary laser tasks are arranged substantially at the same intensity.

[0014] According to one embodiment, the outer end of the elementary central plates of the lateral optical systems are arranged substantially at the level of the outer longitudinal edges of the outer fibers of the fiber strip. Thus, when the adjacent elementary laser tasks overlap substantially entirely by their lateral edges, the combined central plate, formed from elementary central plates substantially at the same intensity level, has a width substantially equal to the width of the fiber strip.

[0015] According to one embodiment, the lateral edges of the elementary laser tasks extend in the longitudinal direction over a width of at most 3 mm, preferably at most 2 mm, better still at most 1 mm, for example of the order of 0.5 mm.

[0016] According to one embodiment, the fiber placement machine is provided for the application of a strip of fibers 6.35 mm wide, the heating means being capable of forming a central plate arranged on each fiber, the width of the central plate in the longitudinal direction preferably being at least equal to 50% of the width of the fibers, preferably at least 60% of the width of the fibers.

[0017] According to one embodiment, when a first fiber is present in the strip and a second fiber adjacent to the first fiber is absent, the control unit is able to - drive at a first power each first laser source associated with a first optical system having a first elementary central plate arranged on the first fiber, and - to control at a second power lower than the first power each second laser source associated with the optical system which is adjacent to a first optical system, and having a second elementary central plate which is not arranged on the first fiber, and which is arranged on the second absent fiber, said control unit preferably being capable of controlling at zero power each source associated with an optical system whose elementary central plate is arranged on an absent fiber, and which is not adjacent to an optical system whose elementary central plate is arranged on a present fiber. A central plate arranged on an absent fiber means an elementary central plate which would be arranged on said fiber if said fiber were present in the band. The use at reduced power of laser devices whose optical systems are not centered on a fiber makes it possible to guarantee sufficient heating of said fiber over its entire width.

[0018] According to one embodiment, the control unit is capable of controlling said second source at a second power lower than the first power, so that the second elementary central plate is substantially arranged at less than 75% of the intensity of the first elementary central plate, preferably at less than 60%, better still of the order of 50%.

[0019] According to one embodiment, each laser device comprises a laser source, preferably of the diode laser type, for example remote from the placement head, connected by an optical fiber to an optical system mounted on the placement head, via appropriate connection means. According to one embodiment, each laser source has a power of at least 500W, that is to say is capable of emitting at the output radiation having a power of at least 500W, preferably at least 600W, better still at least 750W, for example 750W or 1kW.

[0020] The present invention also relates to a method for manufacturing a part made of composite material comprising the application of strips of fibers to an application surface, characterized in that the application of strips of fibers is carried out by means of a fiber placement machine as defined above, by relative movement of the fiber placement head with respect to the application surface according to deposition trajectories.

[0021] According to one embodiment, during the application of each strip of fibers, - when a first fiber is present in the strip and a second fiber adjacent to the first fiber is absent, each first laser source associated with a first optical system having a first elementary central plate arranged on the first fiber, is driven at a first power, each second laser source associated with the optical system which is adjacent to a first optical system, and having a second elementary central plate arranged on the second absent fiber, is driven at a second power lower than the first power, - each laser source associated with an optical system whose elementary central plate is arranged on an absent fiber, and which is not adjacent to an optical system whose central plate is arranged on a present fiber, is preferably driven at low power or zero power.

[0022] According to one embodiment, when applying bands, the laser sources associated with the central optical systems are driven at a first power and the laser sources associated with the lateral optical systems are driven at a second power greater than the first power, so that the elementary central plates of the corresponding elementary laser tasks are arranged substantially at the same intensity.

[0023] The invention will be better understood, and other objects, details, characteristics and advantages will appear more clearly during the following detailed explanatory description of a particular currently preferred embodiment of the invention, with reference to the appended schematic drawings, in which: - [Fig.l] is a schematic side view of a fiber placement head equipped with a set of optical systems according to the invention; - [Fig.2] is a partial enlarged view of [Fig.l] at the pinch zone; - [Fig.3] is a schematic top view of the elementary laser beams from the optical systems; - [Fig.4] is a schematic view representing the different elements of the heating means; - [Fig.5] is a schematic view of the elementary laser tasks projected onto the work plane and their positioning relative to eight FrF8 fibers of width d, for example 6.25 mm (1 / 4 inch), - [Fig.6] is a diagram illustrating the elementary intensity profiles of the elementary laser tasks of [Fig.5] at the working plane in the longitudinal direction parallel to the axis of the compacting roller, when all the laser sources are activated, and the corresponding combined intensity profile, as well as the positioning of the eight FrF8 fibers; - [Fig.7] is a diagram similar to that of [Fig.6], illustrating the elementary intensity profiles and the combined intensity profile when only the F3 fiber is applied; - [Fig.8] a diagram similar to that of [Fig.6], illustrating the elementary intensity profiles and the combined intensity profile when only the fiber Fi is applied; - [Fig.9] is a diagram illustrating the elementary intensity profiles and the combined intensity profile of [Fig.6], and the positioning of four fibers F'i-F'4 of width 2d, for example 12.7 mm (1 / 2 inch); - [Fig. 10] is a diagram similar to that of [Fig.9], illustrating the elementary intensity profiles and the combined intensity profile when only fiber F'2 is applied; and, - [Fig.l 1] a diagram similar to that of [Fig.9], illustrating the intensity profiles elementary and the combined intensity profile when only the fiber F\ is applied.

[0024] Figures 1 and 2 show a fiber placement head 1 of a fiber placement machine according to the invention, comprising a compacting roller 11, which is rotatably mounted about its longitudinal axis A on a support structure 12 of the head. The head is provided for the application of a strip formed of several fibers arranged side by side. The fibers are preferably flat continuous fibers, of the roving type, pre-impregnated with a thermosetting resin or a thermoplastic resin, or dry fibers provided with a binder. The head is mounted by said support structure 12 at the end of a movement system (not shown), for example a robot wrist. With reference to [Fig.2], the head comprises guide means 13 which guide the fibers entering the head towards the compacting roller 12 in the form of a strip of fibers, the fibers of the strip being arranged side by side in a substantially contiguous manner. By moving the head by the robot, the compacting roller is brought into contact with the application surface S of a mold to apply the strip.

[0025] With reference to Figures 3 and 4, the machine according to the invention comprises laser heating means formed of several laser devices, each laser device comprising a laser source 2, connected by an optical fiber 3 to an optical system 4. The optical systems are mounted in a row side by side on the head via a support 14, upstream of the roller 11 relative to the direction of advancement D of the placement head during the application of the strip of fibers on an application surface S. In the present embodiment, the head is provided for the application of a strip of eight fibers F, individually referenced from Fi to F8. The heating means comprise eight laser devices, with eight laser sources 2, individually referenced from 2i to 28, and eight optical systems 4, individually referenced from 4i to 48, including six so-called central optical systems 22 to 27, and two so-called lateral optical systems 2i and 28.Each optical system is connected by its own optical fiber to its laser source. Each optical system is formed, in a manner known per se, of a set of mirrors and / or lenses, to shape the laser beam emitted by the laser source and guided by the optical fiber. The laser sources are offset from the compacting roller, and are connected by connection lines 151 to a control unit 15 of the machine.

[0026] Each optical system forms an elementary laser beam 5 directed obliquely towards the pinching zone between the compacting roller 11 and the application surface S, to heat a section of strip arranged on the roller, before its compaction by the latter, as well as the application surface and / or one or more previously applied fibers. With reference to [Fig. 2], each elementary beam 5 has a main axis B directed substantially towards the contact line .... compaction and the application surface. Each optical system is defined so as to form an elementary laser task defined at a working plane PI orthogonal to the main axis B. The optical system is arranged relative to the compaction roller so that the main axis B is oriented on the contact line, and said working plane PI passes substantially through the contact line.

[0027] [Fig. 5] represents the elementary laser tasks projected onto the work plane, and their positioning relative to the fibers of the strip, along the width of the strip. The elementary laser tasks 6 have a substantially rectangular shape. The central elementary tasks 62 to 67 of the central optical systems 22 to 27 have a width Li in a first direction, called longitudinal, parallel to the axis of the roller, and a height H in a second direction parallel to the longitudinal direction. The lateral elementary tasks 6i and 68 of the lateral optical systems 2i and 28 have a width L2, greater than Lb and the same height H.

[0028] [Fig. 6] schematically represents the elementary intensity profiles 7 of the elementary laser spots in the longitudinal direction, and their positioning along the fiber strip. Each elementary laser spot has an elementary intensity profile of the flat plateau type, conventionally called "top-hat", comprising an extended elementary central plateau, where the intensity is strong and substantially constant at a value Imax, and two steeply sloping lateral edges. The central elementary spots each have a plateau 712-717 of width L\ and lateral edges 722-727 also extending in the longitudinal direction over a width L”. The lateral elementary laser spots each have a plateau 71b 718 of width L'2 larger than L'b and lateral edges 72b 728 extending in the longitudinal direction over a width L”. [Fig. 6] is a schematic representation of the elementary intensity profiles.In practice, the intensity can vary along the plate, by at most 10%, preferably by at most 5%. Furthermore, the elementary intensity profiles can vary from one elementary laser task to another, in particular at the level of the slopes of the lateral edges.

[0029] The central elementary tasks are centered on the fibers F2 to F7, the axes B of the bundles being centered on said fibers. The adjacent elementary tasks are superimposed by their lateral edges over a distance corresponding to the width L”. The lateral elementary tasks 6b 68 are slightly off-center with respect to the fibers Fi and F8, the width L'2 of their plates being for example defined so that the outer ends of said central plates are substantially arranged at the level of the outer edges of the outer fibers Fi and F8.

[0030] When all the fibers of the strip are present, the laser sources 22-27 associated with the central optical systems 42-47 are driven at a power Po so that the corresponding elementary central plates 712-717 are at an intensity Imax. laser sources and optical systems may vary slightly from each other, so each laser device will be calibrated and this power Po may vary slightly from one laser device to another. The power will be defined according to the fibers to be applied. The control unit will vary this power Po according to the speed of the placement head. Since the laser beams of the lateral optical systems 4i and 48 are larger than those of the laser beams of the central optical systems, the laser sources 2i and 28 associated with the lateral optical systems are driven at a power P'o> greater than Po, so that the corresponding elementary plates 71 i, 718 are at the same intensity Imax. The lateral edges of the adjacent elementary profiles intersect at 50% of the intensity Imax.The combined laser spot, formed by the combination of the elementary laser spots, has a combined intensity profile 8, with a flat plateau, with a combined central plateau 81 of intensity Imax, and two lateral edges 82. Each fiber of the strip thus receives uniform laser radiation over its entire width.

[0031] For example, for fibers with a width d of 6.35 mm, - the central elementary tasks have a width Li of 8.35 mm, with a central plateau having a width L\ of 4.35 mm, and lateral edges extending over a width L” of 2 mm, each central plateau is centered on a fiber and is substantially 1 mm from the longitudinal edges of said fiber; - the lateral elementary tasks have a width L2 of 9.35 mm, with a central plate having a width L'2 of 5.35 mm, and lateral edges extending over the same width L” of 2 mm, each central plate is offset relative to an external fiber Fb F8 so that one end of the plate is arranged substantially at the level of the external longitudinal edge of said external fiber, and the other end of the plate is arranged substantially 1 mm from the other longitudinal edge of said fiber. The elementary laser tasks have for example a height H of 13 mm. In the second direction, perpendicular to the first direction, the elementary laser tasks can have a flat plate type intensity profile, with a width less than the central plates 71r718, or a Gaussian type intensity profile. Each laser source is of the diode laser type, for example with a power of 750W.

[0032] [Fig. 7] illustrates the case of the application on the application surface of only the third fiber F3, all the other fibers being absent from the strip. In such a case, according to the invention, the control unit - pilot at a power Pola laser source 23 associated with the optical system 43 centered on said fiber F3 so that its central plate 713 is at the intensity Imax; - drives at a lower power, at approximately 0.5 x Po the two laser sources 22 and 24 associated with the optical systems 42, 44 adjacent to the optical system 43 centered on said fiber, so that the corresponding central plates 712, 714 are at 50% of the intensity Imax; and, - disables other laser sources so that they are at zero power.

[0033] The resulting combined laser spot, formed by the combination of the elementary laser spots 62, 63 and 64, has a combined intensity profile 108, with - a central plateau 181a of intensity Imax corresponding to the central plateau 713; - two lateral plates 181b of intensity 0.5 x Imax corresponding to the central plates 712 and 714; - two combined side edges 182a each connecting the central plate to a side plate, one corresponding to the sum of the side edges 722 and 723, the other corresponding to the sum of the side edges 723 and 724; and, - two lateral edges 182b corresponding to the lateral edges 722 and 724.

[0034] Controlling the two laser sources 22 and 24 at 50% power allows the fiber F3 to be sufficiently heated over its entire width, its longitudinal edges being heated to at least 0.75 x Imax.

[0035] [Fig. 8] illustrates the case of the application on the application surface of only the first fiber Fb, all the other fibers being absent from the strip. In such a case, according to the invention, the control unit - drives at a power P'o the laser source 2i associated with the optical system 4i centered on said fiber Fi so that its central plate 711 is at the intensity Imax; - drives at a lower power of approximately 0.5 x Po the laser source 22 associated with the optical system 42 adjacent to the optical system 4i centered on said fiber, so that its central plate 712 is at 50% of the intensity Imax; and, - disables other laser sources so that they are at zero power.

[0036] The resulting combined laser spot, formed by the combination of the elementary laser spots 61 and 62, has a combined intensity profile 208, with - a first plateau 281a of intensity Imax corresponding to the central plateau 711; - a second plateau 281b of intensity 0.5 x Imax corresponding to the central plateau 712 - a combined lateral edge 282a connecting the two plates, corresponding to the sum of the lateral edges 72i and 722; and, - two lateral edges 282b, 282c corresponding respectively to the lateral edges 72 1 and 724.

[0037] Controlling the laser source 22 at 50% power allows the fiber Fi to be sufficiently heated over its entire width to at least 0.75 x Imax.

[0038] According to another embodiment, the heating means described above are mounted on a fiber placement machine for applying a strip formed of four fibers of width 2d, for example 12.7 mm (1 / 2 inch). [Fig. 9] is a diagram illustrating the elementary intensity profiles of the elementary tasks at the working plane in the longitudinal direction parallel to the axis of the compacting roller, when all laser sources are activated, as well as the corresponding combined intensity profile and the positioning of the 4 fibers F'rF'4 of width 2d. Two elementary central plates are then arranged at each fiber. [Fig.10] illustrates the case of the application on the application surface of only the second fiber F'2, all other fibers being absent from the belt. In such a case, the control unit - drives at a power Po the laser sources 23 and 24 associated with the central optical systems centered on said fiber F'2 so that the corresponding elementary central plates 713 and 714 are at the intensity Imax, - drives at a lower power, at approximately 0.5 x Po the two laser sources 22 and 25 associated with the optical systems adjacent to said optical systems centered on said fiber F'2, so that the corresponding plates 712, 715 are at 50% of the intensity I • max point 9 - disables other laser sources so that they are at zero power.

[0039] The resulting combined laser spot, formed by the combination of the elementary laser spots 62, 63, 64 and 65, has a combined intensity profile 308, with - a central plateau 381a of intensity Imax; - two lateral plates 381b of intensity 0.5 x Imax corresponding to the central plates 712 and 715; - two combined side edges 382a each connecting the central plate to a side plate, one corresponding to the sum of the side edges 722 and 723, the other corresponding to the sum of the side edges 724 and 725; and, - two side edges 382b corresponding to side edges 722 and 725.

[0040] Controlling the two laser sources 22 and 25 at 50% power allows the fiber F'2 to be sufficiently heated over its entire width, its longitudinal edges being heated to at least 0.75 x Imax.

[0041] With reference to [Fig. 11], in the case of the application on the application surface of only the first fiber F'b, the control unit drives the laser source 2i at a power P'o and the laser source 22 at a power Po, so that the corresponding plates 711, 712 are at the intensity Imax, drives the laser source 23 associated with the optical system 43 adjacent to the optical system 42 at a power of approximately 0.5 x Po, so that its central plate 713 is at 50% of the intensity Imax and deactivates the other laser sources so that they are at zero power. The resulting combined laser task, formed by the combination of the elementary laser tasks 61, 62, and 63, has a combined intensity profile 408, with a first plate 481a of intensity Imax; a second plateau 481b of intensity 0.5 x Imax corresponding to the central plateau 713; a combined lateral edge 482a connecting the two plateaus, corresponding to the sum of the lateral edges 722 and 723; and two side edges 482b, 482c corresponding respectively to the side edges 72i and 723.

[0042] Although the invention has been described in connection with different particular embodiments, it is quite obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

Claims

Claims

1. Fiber placement machine for producing composite material parts by applying strips formed from several continuous fibers (F) arranged side by side comprising - a fiber placement head (1), comprising a compacting roller (11) with a longitudinal axis (A) capable of applying several fibers side by side on an application surface (S), - laser heating means comprising several laser devices, each laser device being capable of emitting a laser beam (5) in the direction of the pinching zone between the compacting roller and the application surface, each laser device comprising a laser source (2) and an optical system (4) mounted on the placement head, and - a control unit (15) capable of controlling the laser devices independently of each other, characterized in that each optical system (4r48) is capable of forming an elementary laser task (6r68),at a working plane (PI) in the pinching zone, said elementary laser task having a width (Lb L2) in a longitudinal direction parallel to the axis (A) of the roller, and having in the longitudinal direction an elementary intensity profile (7 r78) of the flat plate type, comprising an elementary central plate (71 r718) and two lateral edges (72r728), said optical systems being arranged and defined so that at the working plane, the adjacent elementary laser tasks overlap outside their elementary central plates, at least partially by their lateral edges, each elementary central plate is arranged at a fiber, at least one elementary central plate being arranged on each fiber.,

2. Machine according to claim 1, characterized in that, at the level of the work plane (PI), the adjacent elementary laser tasks (7r78) overlap substantially entirely by their lateral edges (72r728), so that, when the laser sources (4r48) are controlled in power to obtain elementary central plates substantially at the same intensity level, the combined laser task (8), formed by the combination of the elementary laser tasks, has an intensity profile (108) combined with a flat plate.

3. Machine according to claim 1 or 2, characterized in that the laser heating means comprise a row of optical systems formed of central optical systems (42-47) arranged between two lateral optical systems (4b 48), - the central optical systems (42-47) being capable of forming substantially identical elementary laser tasks (62-67) having in the longitudinal direction a width Lb with elementary central plates (712-717) of width L'b - ​​the lateral optical systems (4b 48), being capable of forming substantially identical elementary laser tasks (6r68), having in the longitudinal direction a width L2 greater than the width Lb with elementary central plates (71b 718) of width L'2 greater than the width L'b

4. Machine according to claim 3, characterized in that the control unit (15) is capable of controlling the laser sources (22-27) associated with the central optical systems (42-47) at a first power (Po) and the laser sources (2b 28) associated with the lateral optical systems (4b 48) at a second power (P'o) greater than the first power, so that the elementary central plates of the corresponding elementary laser tasks are arranged substantially at the same intensity (Imax).

5. Machine according to claim 3 or 4, characterized in that the outer end of the elementary central plates (71b 718) of the lateral optical systems (4b 48) are arranged substantially at the level of the outer longitudinal edges of the outer fibers (Fb F8) of the strip of fibers.

6. Machine according to one of claims 1 to 5, characterized in that, when a first fiber (F3) is present in the strip and a second fiber (F2, F4) adjacent to the first fiber is absent, the control unit is capable of - controlling at a first power (Po) each first laser source (23) associated with a first optical system (43) having a first elementary central plate (713) arranged on the first fiber, and - controlling at a second power lower than the first power each second laser source (22, 24) associated with the optical system (42, 44) which is adjacent to a first optical system (43), and having a second elementary central plate (712, 714) arranged on the second absent fiber.

7. Machine according to claim 6, characterized in that the control unit is capable of controlling said second source (22, 24) at a power lower than the first power, so that the second elementary central plate is substantially arranged at less than 75% of the intensity of the first elementary central plate, preferably at less than 60%, better still of the order of 50%.

8. Machine according to one of claims 1 to 7, characterized in that the heating means comprise laser sources each capable of emitting radiation having a power of at least 500W.

9. Method for manufacturing a part made of composite material comprising the application of a strip of fibers to an application surface, characterized in that the application of the strips of fibers is carried out by means of a fiber placement machine according to one of claims 1 to 8, by relative movement of the fiber placement head with respect to the application surface along deposition trajectories.

10. Manufacturing method according to claim 9, characterized in that, during the application of each strip of fibers, when a first fiber (F3) is present in the strip and a second fiber (F2, F4) adjacent to the first fiber is absent, each first laser source (23) associated with a first optical system (43) having a first elementary central plate (713) arranged on the first fiber, is driven at a first power (Po), each second laser source (22, 24) associated with the optical system (42, 44) which is adjacent to a first optical system (43), and having a second elementary central plate (712, 714) arranged on the second absent fiber, is driven at a second power lower than the first power.

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