Additive manufacturing process by adding plasma-activated thermoplastic layers

Abstract

Additive manufacturing process by adding plasma-activated thermoplastic layers. One aspect of the invention relates to an additive manufacturing process by adding layers (14) based on thermoplastic material (8), superimposed one on top of the other, in which the thermoplastic material of each layer of rank n in the stack is activated by plasma before being covered by the layer of rank n+1, this activation taking place before, during, or after the addition of the layer of rank n. Another aspect of the invention relates to an additive manufacturing machine (1) for implementing this process, which includes a device for creating the layers based on thermoplastic material, and an activation device (15) comprising at least one plasma nozzle (16) arranged to activate the thermoplastic material of each layer of rank n before it is covered by the layer of rank n+1. Figure to be published with the abstract: Figure 1

Description

Title of the invention: Additive manufacturing process by adding plasma-activated thermoplastic layers. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of additive manufacturing by adding successive layers of polymer or composite materials. The invention relates to additive manufacturing by extrusion, in particular by filament deposition, as well as to manufacturing by strip deposition, or even to laser sintering of powders.

[0002] The present invention relates to a manufacturing process by adding successive plasma-activated thermoplastic layers. It also relates to a machine enabling the implementation of this process. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] To manufacture parts from thermoplastic or thermoplastic composite materials, numerous additive manufacturing processes have been developed. These are iterative processes involving the addition of superimposed layers, which allow parts to be built layer by layer. With each new layer, the heat of the newly added material causes it to bond with the previous layer, thus giving the parts overall cohesion. The resulting parts are therefore made up of a stack of superimposed layers of material bonded to one another.

[0004] However, regardless of the additive manufacturing process used, it is observed that the mechanical properties of the resulting part are not identical in all directions. They are significantly reduced when the part is stressed along the layer stacking axis, rather than in a direction belonging to the deposition plane, with the reduction potentially reaching 30 to 50%.

[0005] This degradation of mechanical properties is due to the poor quality of the weld between the layers. Indeed, during manufacturing, the lower layer is not sufficiently heated by contact with the hot material of the next layer for the weld to be satisfactory.

[0006] The situation is even worse with semi-crystalline thermoplastic polymer materials that crystallize and solidify upon cooling. The heat supplied by the subsequent layer is also insufficient to melt the crystallites or spherulites formed during cooling, which block the mobility of the polymer chains and hinder welding. Summary of the invention

[0007] The invention teaches an additive manufacturing process by adding successive thermoplastic polymer layers, which improves the mechanical properties of the product obtained in directions not belonging to the deposition plane, in particular its resistance to inter-laminar shear and fatigue.

[0008] The invention also teaches an additive manufacturing machine for carrying out this process.

[0009] A first aspect of the invention relates to an additive manufacturing process by adding layers based on thermoplastic polymer material, said layers being added one on top of the other so as to form a superposition of N layers, with N > 2, each layer having a rank in the superposition from 1 to N. According to this process, the thermoplastic polymer material of each layer of rank n, with l <n<N, est activé par plasma avant d’être recouvert par la couche de rang n+1, cette activation se faisant avant, pendant ou après l’ajout de la couche de rang n.

[0010] N and n, being numbers of layers, are obviously integers.

[0011] Plasma is an electrically neutral ionized gas which, when projected onto a thermoplastic polymer-based layer, increases the surface energy of that layer. This plasma activation causes the breaking of certain molecular bonds on the surface of the treated layer, thus creating highly reactive sites that bind much more readily with the molecules of the next layer when they come into contact. The bond between the two thermoplastic polymer-based layers is thus greatly enhanced, and the resulting weld is of much higher quality.

[0012] This plasma activation of the thermoplastic polymer material results in an increase in the surface tension of the material which improves the adhesion between the layers.

[0013] In addition, plasma treatment creates nano or microporosity on the surface which further increases this adhesion.

[0014] Thus, we observe a reinforced cohesion between the adjacent layers, which improves the overall mechanical properties of the resulting part in the direction of layer stacking.

[0015] Advantageously, in the case of semi-crystalline polymer materials, plasma activation, in addition to creating reactive sites within the material, at least partially melts the interface crystallites and spherulites that may have formed during material cooling. By eliminating these crystalline phases, plasma activation allows for greater mobility of the polymer chains, improving their reactivity, and promotes bonding between layers.

[0016] When the material contains fibers, particularly carbon fibers, plasma activation also makes it possible to remove transcrystallinity zones which tend to form around these fibers. The free volume is increased and greater mobility of the polymer chains is obtained, improving their reactivity and thus the quality of the interlayer bonding.

[0017] In the context of the invention, the plasma treatment of the layers based on thermoplastic polymer material is not a simple cleaning of these layers, which consists of breaking down the molecules of polluting substances found on the surface of the layers in order to detach them, but a real activation of the material constituting the layers themselves, that is to say of the thermoplastic polymer material belonging to these layers.

[0018] The thermoplastic polymer material used in the process according to the invention can be any material, provided that it is compatible with additive manufacturing and is capable of being activated by plasma. Preferred examples include polyaryletherketones (PAAEK), polyetherimides (PEI), polyethersulfones (PESU), polyphenylene sulfides (PPS), polyphenylene sulfones (PPSU), polycarbonates (PC), and polyamides (PA).

[0019] The layers may be composed solely of one or more thermoplastic polymer materials.

[0020] These layers may also contain other elements in addition, for example fillers and / or fibers, in particular glass, carbon or aramid fibers, giving complementary properties to the part manufactured according to the intended applications.

[0021] These layers can also be made from composite strips, formed from any suitable material impregnated with thermoplastic polymer resin.

[0022] Once a layer is activated by plasma, it is covered by the next layer so that the reactive sites created in the thermoplastic polymer material of that layer react and bond with the molecules of the next layer.

[0023] If the treated layer is left untreated, the reactive sites gradually disappear as they react with each other and with their environment. However, plasma activation treatment advantageously offers a long effective duration, on the order of one or more hours with a thermoplastic polymer material, which is significantly longer than the operational durations encountered in additive manufacturing. Once the thermoplastic polymer material has been activated by plasma, it is therefore not necessary for the activated layer to be immediately covered by the next layer.

[0024] The duration of effectiveness is called the period which begins at the time of activation by plasma and which lasts as long as the activation is sufficient for the welding to be satisfactory.

[0025] The plasma activation treatment of the thermoplastic polymer material can therefore be carried out indifferently before, during or after the addition of the layer concerned.

[0026] During the process, the thermoplastic polymer material of the nth layer can be activated by plasma before the step of adding the nth layer.

[0027] In this case, the activation can advantageously be carried out on the material before it reaches the layer-making device, for example at the exit of the storage area or just before its passage into the layer-making device.

[0028] The duration of effectiveness of the activation treatment is largely sufficient for the material to then reach the layer making device, for layer n to be added by it, and then be covered by layer n+1, without losing the benefit of the activation treatment, the whole of these steps lasting only a few seconds to a few minutes depending on the type of additive manufacturing and the size of the part made.

[0029] Thus, the activation device can advantageously be fixed, independent of the layer-making device, and placed far from it, in a less cluttered area where it will not hinder the movement of the layer-making device. The activation device will be technically simpler to manufacture and less expensive.

[0030] Alternatively, the thermoplastic polymer material of the rank n layer can be activated by plasma during the step of adding the rank n layer to an already added portion of the rank n layer.

[0031] Alternatively, the thermoplastic polymer material of the rank n layer can be activated by plasma during the step of adding the rank n+1 layer to a portion not yet covered by the rank n layer.

[0032] In these last two cases, plasma activation is advantageously carried out after the thermoplastic material has passed through the layer-making device. Therefore, the activation efficiency is not likely to be diminished by the treatment the material undergoes in this device.

[0033] Furthermore, plasma activation is also carried out after the thermoplastic material has begun to cool. If the thermoplastic polymer material is semi-crystalline or contains fibers, the plasma activation treatment advantageously reduces the crystalline phases or transcrystallinity zones, which form a few hundredths of a second to a few seconds after the start of cooling.

[0034] Furthermore, the activation process is performed simultaneously with the layer addition step, whether it be layer n or layer n+1. The activation device can then advantageously be coupled to the layer creation device, for example integrated onto it and / or placed on the same robotic arm. The two devices can be piloted simultaneously, which facilitates the piloting operation and simplifies the machine.

[0035] During the process, plasma activation can only be carried out on the face of the layer of rank n intended to be in contact with the layer of rank n+1.

[0036] In this case, activation is only done on one side of each layer, which is easy to achieve with simple and inexpensive equipment, such as a plasma nozzle of the strip type for example.

[0037] The activation is nevertheless sufficient because it creates reactive sites in the part of layer n which will be in contact with layer n +1. At each interface between two successive layers, one of the layers therefore has on its contact face reactive sites improving the bonding between the two layers.

[0038] According to another example, plasma activation can be carried out on all faces of the nth layer.

[0039] In this case, activation is complete on all outer faces of the layers. At each interface between two successive layers, both layers have reactive sites on their contact face. The bond between the two layers is therefore further improved.

[0040] The process according to the invention is advantageously compatible with any type of additive manufacturing by adding superimposed layers based on thermoplastic polymer material.

[0041] This may be, for example, an additive manufacturing process by extrusion (“Extrusion Additive Manufacturing” in English), whether by filament deposition, also called fused filament fabrication (“Fused Filament Fabrication” or “Filament Deposition Molding”™ in English), or by extrusion from other types of solid or liquid material, in particular from cylindrical cartridges, paste or granules (fused granular fabrication or “Fused Granular Fabrication” in English).

[0042] It may also be a strip-depositing additive manufacturing process, that is to say a layer-by-layer deposition of strips of any width previously formed, in particular composite strips impregnated with thermoplastic polymer resin, such as an automated fiber placement process (“Automated Fiber Placement” or “micro Automated Fiber Placement” in English), or an automated tape layup process (“Automated Tape Layup” in English).

[0043] This may also be, for example, an additive manufacturing process by powder sintering such as selective laser sintering (“Selective Laser Sintering” in English).

[0044] A second aspect of the invention relates to an additive manufacturing machine enabling the implementation of such a process. This machine comprises a device of layer fabrication capable of adding layers of thermoplastic polymer material on top of each other to form a superposition of N layers, with N > 2, each layer having a rank in the superposition from 1 to N, and an activation device comprising at least one plasma nozzle arranged to activate the thermoplastic polymer material of each layer of rank n, with l <n<n, avant que ce matériau soit recouvert par la couche de rang n+1.

[0045] This machine may be, for example, an additive manufacturing machine by extrusion, in particular a manufacturing machine by deposition of filaments, molten wires or molten granules, or an additive manufacturing machine by deposition of pre-formed strips, in particular an automated fiber placement machine, automated micro-fiber placement machine or automated strip overlay machine, or an additive manufacturing machine by selective laser sintering.

[0046] Advantageously, the plasma nozzle of this machine can be a rotary nozzle or an annular nozzle.

[0047] In a rotary nozzle, the plasma exit angle is adjustable, which advantageously allows for the processing of a greater width of material and the uniform distribution of the plasma effect over the entire surface to be treated. With a single rotary nozzle, it is thus possible to process wide strips or several strips or filaments simultaneously, particularly if the machine has several extrusion heads, or the forward and reverse feeds of the same filament. This avoids the need to use multiple plasma nozzles.

[0048] An annular nozzle advantageously allows for activation treatment on all faces of the layer to be treated. Indeed, the annular nozzle projects the plasma from its circumference towards the inside of the ring through which the thermoplastic material passes, thus activating all faces of the corresponding layer.

[0049] Alternatively, a rotating nozzle capable of rotating around the thermoplastic material also makes it possible to carry out such treatment on all faces of the layer concerned.

[0050] Advantageously, the plasma nozzle can be linked directly or indirectly to the layer making device, so that the plasma nozzle moves with the layer making device.

[0051] The plasma nozzle is thus controlled with the layer making device, which simplifies the machine.

[0052] The plasma nozzle can, for example, be placed directly on the layer preparation device or on the same robotic arm as the latter. It is generally attached there by standard means, in particular by screwing or clipping. In case of obstruction, the plasma nozzle can also be offset from the layer delivery device.

[0053] When connected to the layer building device, the plasma nozzle can, for example, be positioned upstream of this device. In this case, the nozzle projects plasma onto the uncoated portion of the previously added layer n, while the layer building device adds layer n+1.

[0054] According to another example, the plasma nozzle can be positioned downstream of the layer-building device. In this case, the nozzle projects plasma onto the portion of layer n that the layer-building device has just added.

[0055] According to yet another example, the plasma nozzle can be positioned alternately upstream and downstream of the layer making device.

[0056] This situation occurs when the plasma nozzle is linked to a layer preparation device which does not pivot when it reaches the end of its stroke, but goes back in the opposite direction after having shifted laterally.

[0057] Upstream and downstream are defined with respect to the direction of movement of the layer making device.

[0058] Advantageously, the plasma nozzle of this machine can also be arranged so as to be able to activate the thermoplastic polymer material before it reaches the layer-making device.

[0059] In this case the plasma nozzle can advantageously be fixed and independent of the layer making device.

[0060] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0061] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0062] [Fig.1], [Fig.2] and [Fig.3] are schematic perspective views of three variants of a filament deposition additive manufacturing machine with a single extrusion head, with respectively a plasma nozzle upstream of the layer building device, a plasma nozzle downstream of the layer building device, and an annular plasma nozzle.

[0063] [Fig.4] is a schematic perspective view of an additive manufacturing machine by depositing filaments with two extrusion heads with a plasma nozzle upstream of the layer making device.

[0064] [Fig.5], [Fig.6] and [Fig.7] are schematic side views of a machine Additive manufacturing by automated fiber placement, with a plasma nozzle that activates a layer already deposited upstream for [Fig. 5] and downstream for the [Fig.6] of the layer making device, and a plasma nozzle which activates a layer not yet deposited for the [Fig.7].

[0065] [Fig.8] and [Fig.9] are schematic perspective views of two variants of a selective laser sintering additive manufacturing machine, with respectively a plasma nozzle that activates a layer already solidified by laser in the build tank and a plasma nozzle that activates the powder in the reserve tank. DETAILED DESCRIPTION

[0066] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0067] Several examples of additive manufacturing machines 1 according to the invention are shown in the figures: an additive manufacturing machine by filament deposition 2 in figures 1 to 4, a machine by automated fiber placement 3 in figures 5 to 7 and a machine by selective laser sintering 31 in figures 8 and 9.

[0068] Although the invention has only been illustrated in this context, it is obviously possible to implement it with other types of additive manufacturing machines.

[0069] The filament deposition additive manufacturing machine 2 shown comprises an enclosure 4 containing a vertically movable platform 5 on which an object 6 is manufactured.

[0070] A layer making device 7, which is here a deposition device, deposits layer by layer, on the platform 5, the constituent material of the object 6. This material, based on a thermoplastic polymer material 8, is in this example in the form of a filament 9 unwound from a spool 10 and pulled to an extrusion head 11 of the layer making device 7.

[0071] The extrusion head 11 includes heating elements 12 which melt the filament material and an extrusion nozzle 13 through which the molten material is extruded.

[0072] By moving above the plate 5 in the horizontal plane, the extrusion head 11 deposits a bead of material which forms by juxtaposition a layer 14 of the object 6.

[0073] The transition from one layer to the next in the stack is achieved by a downward vertical movement of the plate 5 or an upward vertical movement of the extrusion head 11. Moving in the horizontal plane, the extrusion head 11 then deposits the bead of material constituting the upper layer n+1 on top of the previous layer n. This process is repeated until the object 6 is completely manufactured.

[0074] In the example shown, the layers 14 of the object 6 are horizontal. However, with more sophisticated tooling, it is possible to make them non-planar by superimposing them according to the same principle on the surface of a non-planar support, until the complete fabrication of the desired object.

[0075] The filament deposition additive manufacturing machine 2 further includes an activation device 15 comprising a plasma nozzle 16 which emits a plasma jet 17 capable of activating the thermoplastic polymer material 8.

[0076] Different plasma nozzles 16 can be used, for example a bar-type nozzle, an annular nozzle 18 or a rotary nozzle 19.

[0077] In the examples in Figures 1 and 2, the plasma nozzle 16 is linked to the extrusion head 11 so as to follow its movement symbolized by arrow 20.

[0078] In [Fig. 1], the plasma nozzle 16 is placed upstream of the extrusion head 11. It projects its plasma jet 17 onto the previously deposited layer n-1, just before it is covered by the new bead coming out of the extrusion head 11 which deposits the next layer n of the superposition.

[0079] In [Fig.2], the plasma nozzle 16 is arranged downstream of the extrusion head 11. It projects its plasma jet 17 onto the bead that the extrusion head 11 has just extruded, and therefore onto the layer n that the extrusion head 11 is depositing.

[0080] In the example of [Fig. 3], the plasma nozzle 16 is independent of the extrusion head. It is an annular nozzle 18 that defines a hollow internal volume 20 in which the plasma jet is generated. The filament 9 from the spool 10 passes through this hollow internal volume 21 and undergoes plasma activation of its thermoplastic polymer material 8, before reaching the extrusion head 11.

[0081] In the example of [Fig.4], the layer 7 fabrication device of the filament deposition additive manufacturing machine 2 is a deposition device which includes two extrusion heads 11, each with heating elements 12 and an extrusion nozzle 13, each of these extrusion heads 11 being fed by a filament 9a, 9b from a different spool 10a, 10b.

[0082] Such a machine makes it possible, for example, to produce more complex objects 6 with cantilevered parts. One of the filaments, called the main filament 9a, is used to print the object 6, while the second filament, called the support filament 9b, is used to print a support structure 22 which serves as a support for the cantilevered layers of the object 6. Once the fabrication is complete, this support structure 22 is removed from the object 6, for example by dissolving it in a suitable solvent.

[0083] The machine further includes an activation device 15 comprising a plasma nozzle 16 which activates the thermoplastic polymer material 8 of the main filament 9a.

[0084] Advantageously, the plasma nozzle 16 can be a rotating nozzle 19, capable of activating the thermoplastic polymer material of the two filaments 9a and 9b by a variation of the exit angle of the plasma jet 17.

[0085] Alternatively, it is possible to provide two plasma nozzles 16, one for each of the filaments 9a and 9b, or a wide jet plasma nozzle capable of simultaneously activating both filaments 9a and 9b.

[0086] In the example of [Fig.4], the plasma nozzle 16 is linked to the extrusion heads 11 and arranged upstream of them.

[0087] The automated fiber placement additive manufacturing machine 3 shown in Figures 5 to 7 includes a support tooling 23 on which a layer making device 7 stacks strips 24 impregnated with thermoplastic polymer material to constitute the different layers 14 of the object 6 to be manufactured.

[0088] The layer making device 7 includes a laser source 25 and a compaction roller 26 which move in the direction of the arrow 27.

[0089] During the step of adding a strip 24 belonging to layer n of the stack, the laser source 25 heats by its laser radiation 28 the lower face 29 of the strip 24 of the layer n being added and the upper face 30 of the strip 24 of the layer n-1 previously added, to locally melt the thermoplastic polymer material of these strips.

[0090] The lower face 29 of the strip 24 of layer n and the upper face 30 of the strip of layer n-1 are then brought into contact and pressed against each other by the compaction roller 26 to weld them together.

[0091] The machine 3 also includes an activation device 15 with at least one plasma nozzle 16.

[0092] In the example of [Fig.5], the plasma nozzle 16 moves with the layer making device 7. It is for example fixed to the arm carrying the laser source 25.

[0093] The plasma nozzle 16 is arranged upstream of the layer making device 7 and activates by its plasma jet 17 the upper face 30 of the band 24 of the layer n-1 already added, before it is heated by the laser radiation 28 and covered by the band 24 of the layer n being added.

[0094] In the example of [Fig.6], the plasma nozzle is arranged downstream of the layer making device 7 and activates by its plasma jet 17 the upper face 30 of the band 24 of the layer n being added.

[0095] The plasma nozzle 16 is linked to the layer formation device 7 and moves with it. For example, it is fixed to the support of the compaction roller 26.

[0096] In the example of [Fig.7], the plasma nozzle 16 activates a portion of the strip 24 which has not yet reached the layer making device 7 and therefore before it has been heated by the laser radiation 28 and pressed by the compaction roller 26.

[0097] The laser powder sintering additive manufacturing machine 31 (“Selective Laser Sintering” or SLS in English) shown in figures 8 and 9 allows the object 6 to be manufactured to be built layer by layer from a thermoplastic polymer material 8 in powder form 32.

[0098] The machine 31 includes a reserve bin 33 which serves as a storage tank for the powder not yet used, a build bin 34 which is the main bin in which the additive manufacturing takes place and a recovery bin 35 in which the excess powder is recovered.

[0099] The bottoms, respectively 36, 37 and 38, of the reserve 33, construction 34 and recovery 35 bins are vertically movable in order to increase or decrease the capacity of the bin concerned.

[0100] The layer making device 7 includes a laser source 25, the beam of which 39 is precisely directed by an inclined mirror 40 towards the surface of the build tray 34, and a scraper 41 which moves horizontally on the surface of the trays pushing the powder.

[0101] To produce the nth layer 14 of the manufacturing process, the scraper 41 begins by spreading powder 32 from the reservoir 33 onto the surface of the build hopper 34. Then the laser source 25 solidifies this nth layer by heating and locally fusing the thermoplastic polymer material 8 of the powder 32 only according to the path of the nth layer of the object 6.

[0102] The bottom 37 of the construction tank then descends by the thickness of a layer 14, as does that of the recovery tank 38, while the bottom 36 of the reserve tank 33 rises. The process can then begin again in the same way for the next layer n+1.

[0103] The machine 31 also includes an activation device 15 with at least one plasma nozzle 16.

[0104] In the example of [Fig.8], the plasma nozzle 16 activates by its plasma jet 17 the thermoplastic polymer material 8 which is in the build tank 34.

[0105] The plasma nozzle 16 can, as shown, be placed downstream of the laser beam 39 and activate the layer 14 of rank n already solidified by the laser source 25. In this case, the activation therefore takes place after the addition of the layer of rank n.

[0106] Alternatively, the plasma nozzle can be arranged upstream of the laser beam 39 and activate the powder 32, already placed by the scraper 40 to form the layer 14 of rank n, but before its solidification by the laser source 25. In this case, the activation takes place during the addition of the layer of rank n.

[0107] In the example of [Fig.9], the plasma nozzle 16 activates the thermoplastic polymer material 8 of the powder 32 which is in the reservoir 33, before the scraper 40 carries it into the build hopper 34. The activation therefore takes place before the addition of the layer of rank n.

[0108] Advantageously, the invention is not limited to a particular type of plasma, and different plasma sources can be used satisfactorily. One can For example, the Openair-Plasma® solution marketed by the company PLASMATREAT can be cited as being perfectly suited.

[0109] Since the power of the plasma source is generally fixed and varies depending on the device used, a person skilled in the art can easily optimize the other activation parameters, namely the distance between the plasma nozzle 16 and the material 8 to be activated, as well as the speed of movement (speed of filament advance, of strip deposition or of movement of the plasma nozzle...), in order to adapt them to the power of the plasma source used and to the nature of the thermoplastic polymer material 8 considered in order to obtain a satisfactory activation of the latter.

[0110] To do this, it will suffice, for example, to compare the initial surface tension of the material to that of the same material after plasma treatment by varying these parameters and then apply, for additive manufacturing, the parameter setting that gives the highest surface tension. This surface tension can be measured conventionally using calibrated inks or a goniometer.

[0111] By way of example, with a thermoplastic polymer material 8 in polyetherimide (PEI) and an Openair-Plasma® type plasma source of about 5kW power, a preferential distance of between 15 and 25 mm was determined, with a scroll speed of 10 to 50 mm per second for treatment with a conventional nozzle of 3 to 5 mm (quasi “spot” treatment) or of 100 mm per second with two juxtaposed nozzles (treatment over a greater length).

[0112] With such parameters, the surface tension of the PEI advantageously changes from a value of 56mN / m initially measured to a value greater than 75 mN / m measured after treatment.

Claims

Demands

1. An additive manufacturing process by adding layers (14) based on a thermoplastic polymer material (8) one on top of the other so as to form a superposition of N layers (14), with N > 2, each layer (14) having a rank in the superposition from 1 to N, a process characterized in that it is an additive manufacturing process by strip deposition and in that the thermoplastic polymer material (8) of each layer (14) of rank n, with l <n<N, est activé par plasma, au moyen d’une buse rotative à angle de sortie du plasma modifiable, avant d’être recouvert par la couche de rang n +1, cette activation pouvant se faisant avant, pendant ou après l’ajout de la couche de rang n.

2. Additive manufacturing method according to claim 1 characterized in that the thermoplastic polymer material (8) of the layer (14) of rank n is plasma activated before the step of adding the layer (14) of rank n.

3. An additive manufacturing process according to claim 1 characterized in that the thermoplastic polymer material (8) of layer (14) of rank n is plasma-activated during the step of adding layer (14) of rank n onto a portion of layer (14) of rank n that has already been added.

4. 11. Additive manufacturing process according to claim 1 characterized in that the thermoplastic polymer material (8) of the layer (14) of rank n is activated by plasma during the step of adding the layer (14) of rank n+1, on a portion not yet covered of the layer (14) of rank n.

5. An additive manufacturing process according to any one of the preceding claims, characterized in that the plasma activation is carried out on all faces of the layer (14) of rank n or only on the face of the layer (14) of rank n which is intended to be in contact with the layer (14) of rank n+1.

6. A strip-deposition additive manufacturing machine (1) enabling the implementation of the process according to any one of the preceding claims, characterized in that it comprises a layer-building device (7) capable of adding layers (14) based on thermoplastic polymer material (8) one on top of the other so as to form a superposition of N layers (14), with N > 2, each layer (14) having a rank in the superposition from 1 to N, and an activation device (15) comprising at least one plasma nozzle (16) which is a rotating nozzle (19) with an adjustable plasma outlet angle and which is arranged so as to be able to activate the thermoplastic polymer material (8) of each layer (14) of rank n, with l <n<n, avant qu’il ne soit recouvert par la couche de rang n+1.

7. Additive manufacturing machine (1) according to claim 6 characterized in that the plasma nozzle (16) is linked directly or indirectly to the layer making device (7), so that the plasma nozzle (16) moves with the layer making device (7).

8. Additive manufacturing machine (1) according to claim 7 characterized in that the plasma nozzle (16) is positioned upstream or downstream or alternately upstream and downstream of the layer building device (7), relative to the direction of movement of the layer building device (7).

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