阅读说明：本技术 逐层制造零件的方法以及可逐层制造的零件 (Method for producing a part layer by layer and part that can be produced layer by layer ) 是由 亚松森·布特拉格尼奥-马丁尼兹 吉列尔莫·埃尔奈斯洛佩斯 何塞·桑切斯-戈麦斯 于 2021-03-23 设计创作，主要内容包括：本发明提供了一种适用于结构性应用的使用增材制造技术逐层制造零件的方法。所述方法包括选择性地沉积至少第一类型长丝和第二类型长丝,其中,所述第二类型长丝至少在截面尺寸上与所述第一类型长丝不同。本发明还提供了一种根据所述方法使用增材制造技术的可逐层制造的零件。(The present invention provides a method of manufacturing a part layer by layer using additive manufacturing techniques suitable for structural applications. The method comprises selectively depositing at least a first type of filament and a second type of filament, wherein the second type of filament differs from the first type of filament at least in cross-sectional dimension. The invention also provides a part manufacturable layer by layer using additive manufacturing techniques according to the method.)

1. -a method of manufacturing a part layer by layer using an additive manufacturing technique, wherein the method comprises performing at least one of the following steps:

a. forming a layer by depositing filaments of a first type (1), at least a portion of the filaments of the first type (1) being deposited alongside one another, thereby creating at least one channel (3), and

b. depositing at least a portion of the filaments of the second type (2) along the channel (3);

wherein the second type of filaments (2) differs from the first type of filaments (1) at least in cross-sectional dimension.

2. -the method according to claim 1, wherein the filaments of the first type (1) comprise a larger cross-sectional dimension than the filaments of the second type (2).

3. -the method according to any of claims 1 or 2, wherein at least one filament of the first type (1) and/or at least one filament of the second type (2) has a cross-sectional shape that is circular, triangular or elliptical.

4. -method according to any of claims 2 or 3, wherein the filaments of the first type (1) and/or the filaments of the second type (2) are made of a reinforcement of fibrous material embedded within a meltable material, preferably the meltable material is a thermoplastic material.

5. -the method according to any one of claims 1 to 4, wherein at least one of the filaments of the second type (2) is discontinuous, in the form of pellets or balls.

6. -the method according to any one of claims 4 or 5, wherein the fibrous material reinforcement of the second type of filaments (2) is in the form of fibrils, nanofibers, carbon fillers or staple fibers.

7. -method according to any one of claims 4 to 6, wherein the fibre volume content of the filaments (1) of the first type is higher than 50% and the fibre volume content of the filaments (2) of the second type is lower than 50%.

8. -method according to any one of the preceding claims, wherein at least a portion of the filaments of the second type (2) are deposited along the filaments of the first type (1) so as to fill the channels (3) that will be created by a subsequent pair of filaments of the first type (1) deposited alongside one another.

9. -method according to any of the preceding claims, wherein the cross-sectional dimensions and/or the length of the filaments (2) of the second type are selected to fill voids (3.1, 3.2) introduced during the process.

10. -the method according to any of the preceding claims, wherein the first type of filaments (1) is deposited at a first temperature and the second type of filaments (2) is deposited at a second temperature.

11. -method according to claim 10, wherein the method further comprises the step of cooling down the part at a predetermined cooling rate, preferably selected for such part to reach a crystallinity of at least 32%.

12. -method according to any one of the preceding claims, wherein a portion of the part is manufactured by performing steps a) and b) alternately a certain number of times on the partially manufactured part.

13. -the method according to any of claims 1 to 12, wherein the method further comprises the step of:

c. depositing at least a portion of the filaments of the second type (2) along the channels (3) formed by the filaments of the first type (1) so as to form a portion of the outer wall of the part.

14. -method according to claim 13, wherein the outer wall of the part is entirely made of at least one layer of filaments (2) of the second type.

15. -a layer-by-layer manufacturable part using additive manufacturing techniques according to the method of any one of the preceding claims.

Technical Field

The invention is in the field of manufacturing, and in particular, to the field of manufacturing low porosity or void free parts using additive manufacturing techniques.

More particularly, the present invention has particular application in the manufacture of printed parts for structural applications where conventional compaction is not feasible.

Background

In the past, aircraft parts with structural applications have been made from aluminum alloys. Over the past several decades, with the development of composite fabrication techniques, such structural parts have been fabricated using different techniques, such as co-bonding or co-curing of Carbon Fiber Reinforced Plastic (CFRP) component parts.

However, all of these manufacturing techniques require that the components undergo different stages of operation in order to separately manufacture the different component parts that will subsequently be assembled together. This is a time consuming process and predetermines the productivity of the aircraft. As a result, the final part is obtained after a series of different manufacturing steps, which increases manufacturing costs and time.

This drawback, along with the high duplication/non-duplication costs associated with these conventional manufacturing techniques, has prompted the emergence of aerospace Additive Manufacturing (AM) technology.

Typically, these AM techniques use computers with 3D modeling software (computer aided design or CAD), additive manufacturing tools (e.g., machine equipment), and layered material filaments. The CAD sketch is a 3D electronic model of the final 3D object build. The AM tool is capable of reading in data (both cross-sectional geometry and surface pattern) from a CAD file and laying down or depositing successive filaments of liquid, powder, sheet, etc. (then forming layers) in a layer-by-layer manner through at least one head to fabricate a 3D object.

Thus, the possibility of reducing the purchase-to-fly ratio (i.e. the ratio between the mass of material required to produce the part and the mass of material in the final aeronautical structure) while achieving rapid prototyping sets a promising roadmap for layer-by-layer printing of polymer parts.

However, it is well known that the mechanical properties of printed composite parts are still far inferior to aluminum parts or composite parts manufactured by conventional techniques. This is due, on the one hand, to the inherent defects of conventional printed parts, such as voids, pores, and, on the other hand, to the poor adhesion between continuous filaments from the same or different layers.

The formation of voids or process-induced voids is primarily due to the generally circular cross-section of the filaments of the stacked layers, and typically these voids extend in the direction of printing. Another typical local defect is that there is no polymer chain interfusion between adjacent filaments, which makes the interlaminar shear strength ('ILSS') very low and results in weaker printed parts when subjected to certain stresses.

Thus, these voids and print defects may act as stress concentrators when these conventionally printed parts are tested or put into service, thereby causing premature part failure.

Current solutions mostly provide an in-situ pinch mechanism based on a roller that typically applies pressure to the deposited layer against the print bed to close the gap and enhance adhesion. The latest solutions rely on a vacuum bed to assist the printing process, and although consolidated pieces are available, tight dimensions are not yet achievable.

However, it is not always possible to benefit from these available compaction solutions because the complex geometry makes it difficult for the rollers to roll extensively and uniformly, or because some printing tools are not compatible with these compaction devices.

There is therefore a need in the industry for an easy and efficient manufacturing of structural printed parts which can ensure that mechanical properties are imparted in order to meet structural requirements and which can be widely applied whether or not a compaction system is used and for any desired geometry.

Disclosure of Invention

The present invention provides a solution to the above-described problems by a method of manufacturing a part layer by layer using additive manufacturing techniques as described below. In the following, preferred embodiments of the invention are also defined.

In a first aspect of the invention, the invention provides a method of manufacturing a part layer by layer using an additive manufacturing technique, wherein the method comprises selectively depositing at least a first type of filament and a second type of filament.

Throughout this document, "additive manufacturing techniques" (AM) will be understood as those techniques for building 3D objects by adding material layer by layer, wherein the material (a meltable material or a matrix material in the case of a reinforcing material) becomes liquid upon application of heat and solidifies (or hardens) into a solid upon cooling.

Prior to printing, a digital CAD sketch of a 3D part is sliced into multiple horizontal sections or layers. The printer controller then uses the generated slices to sequentially manufacture the part by bonding or adhering each layer to the previous one layer at a time (i.e., layer by layer).

Many techniques are involved in additive manufacturing techniques, depending on the materials used and the form of the machine technology. Among these, Selective Laser Sintering (SLS), Stereolithography (SLA), multi-jet modeling (MJM) or fuse fabrication (FFF) may be noted.

Fuse Fabrication (FFF) is a process-oriented fabrication that includes the use of material in the form of filaments that are injected onto a build sheet through at least one indexing nozzle. The nozzle(s) track the surface pattern of each particular layer and the material hardens before the next layer is deposited. This process is repeated until the piece is complete, i.e., printed.

In a preferred embodiment of the method of the present invention, the part is printed using fuse fabrication (FFF). In FFF, each deposition layer is formed from a set of oriented filaments. As is well known, FFF is a specific example of 3D printing (3 DP).

According to the invention, the second type of filaments differs from the first type of filaments at least in cross-sectional dimension.

For those printer tools that allow setting the layer height, this cross-sectional dimension of the first type of filament or the second type of filament is understood as the height setting that determines the height of each layer formed by the filament. Setting a thicker layer height will cause the printed part to have coarse (i.e., less fine) details, making the layer more visible. On the other hand, setting a thinner layer height allows the part to have a higher level of detail, but delays production time.

In addition to this, if the filaments (first type or second type) have a non-constant cross-sectional shape, the cross-sectional dimension will be understood as the measured cross-sectional area or value at the thickest point of such a filament.

Thus, the method comprises performing at least once the following steps:

a. forming the layer by depositing filaments of a first type, at least a portion of the filaments of the first type being deposited alongside one another, thereby creating at least one channel, an

b. Depositing at least a portion of the second type of filaments along the channel,

wherein the second type of filaments differs from the first type of filaments at least in cross-sectional dimension.

That is, the slicing procedure of the printing tool provides for uneven slicing of the 3D CAD part, because the layers now have different heights by alternating the layers formed by the first type of filament or the second type of filament for at least a portion of the part. In other words, steps a) and b) are alternated.

Thus, a "layer" is understood as a group of filaments deposited during the same deposition step. According to the invention, the layer may comprise filaments and/or spaced apart filaments deposited side by side to each other. The layer of filaments of the first type has at least some filaments deposited side-by-side with one another, while the layer of filaments of the second type may be formed of spaced apart filaments. For example, in 2.5D manufacturing, each filament contained in the same layer is at the same height from the die.

A pair of filaments of the first type are deposited alongside one another over a length creating a groove, notch or channel therebetween that extends along the length.

According to the invention, a second type of filament with a different cross-sectional dimension is deposited on such a channel, so that it simultaneously contacts two previously deposited filaments of the first type.

Thus, unlike prior art manufacturing processes where subsequent layer deposition of the first type of filaments introduces interstitial voids, the present invention fills or occupies such voids with the second type of filaments.

Conventional manufacturing processes typically include: depositing a first type of filament onto a channel created by two filaments of the same type deposited alongside one another, or similarly, depositing a pair of filaments of the first type onto two filaments of the same type deposited alongside one another.

Since the part is made of a polymeric material, the molten filaments are ejected from the nozzle and thus tend to flatten out as they are deposited. The melted second type of filament may then better conform to the channel shape created by the pair of hardened first type of filaments to further reduce porosity. In other words, the parts made by the present invention are closer to the homologous parts.

Avoiding or reducing voids allows the filaments to contact along more areas, which, combined with the fact that the printing process is typically performed at high temperatures, promotes filament bonding and polymer fusion, thus improving the inter-layer adhesion.

As a result, not only are the mechanical properties of the printed part, such as ILSS, tensile strength, compressive strength, etc., greatly improved, but dimensional tolerances are also improved.

Balancing the deposition of the first type of filament or the second type of filament does not jeopardize manufacturing lead time because the entire part does not need to be finely sliced. Therefore, the present invention shortens the time compared to the fine printing.

In short, the consolidated printed part made by the method according to the present invention has a high resolution surface, fewer pores or voids, and no interfaces as compared to conventional printed parts.

For example, aerospace parts (and thus interfaces) that are typically manufactured in pieces and then assembled together can be integrally manufactured at one time and meet any structural specifications in accordance with the present invention. This leaves the part without an interface (i.e., integral or self-sealing). The resulting tightness advantageously reduces water absorption problems and bond debonding due to the tendency of thermoplastic printing materials to absorb moisture. Furthermore, since the printed part has better structural properties, the operation can be enhanced.

The undesirable effects of water absorption are emphasized in the aerospace field where structural parts are exposed to humid environments during use.

Thus, in a preferred embodiment, the printed part is an aerospace part.

In a preferred embodiment, the first type of filament comprises a larger cross-sectional dimension than the second type of filament.

In a particular embodiment, the at least one filament of the first type and/or the at least one filament of the second type have a cross-sectional shape that is circular, triangular or elliptical.

In particular embodiments, the first type of filaments are deposited at a first temperature and the second type of filaments are deposited at a second temperature.

The head typically includes an extruder that uses a torque and clamping system to feed and retract the fed filaments in order to drive the desired amount of material deposition. The head may also include a heating block for heating the meltable material to any precise temperature. Once the material is heated, its diameter is reduced and forced out of the nozzle, thereby allowing the material to be deposited more accurately.

Thus, according to this embodiment, two heads, one for each filament type, may be used to eject the filaments at different temperatures. Alternatively, in the case of a single head, the heating block selectively heats the first type of filaments or the second type of filaments to their respective precise temperatures.

Either way, it is preferred that at least the second temperature (at which the second type of filaments will be deposited) is higher than the glass transition temperature of the second type of filaments in order to better accommodate the channel shape when laid.

Furthermore, as already mentioned, when depositing a single filament or a pair of filaments of the first type on a channel created by two filaments of the same type deposited alongside one another, voids introduced in the process are created, respectively substantially triangular voids or substantially kite-shaped voids.

Thus, in a particular embodiment, at least a portion of the filaments of the second type are deposited along (and on) the filaments of the first type so as to fill the channel that would be created by a subsequent pair of filaments of the first type deposited alongside one another.

Thus, in certain embodiments, the cross-sectional dimension and/or length of the second type of filament is selected to fill such voids, i.e., there should be no shortage or excess of filler material in the voids.

In this regard, due to the strong temperature dependence when forming bonds (diffusion-based fusing) between adjacent filaments/layers, typical printing tools preheat their printing chamber or ambient environment in order to reach and maintain an operating printing temperature determined by the selected material.

Thus, according to the invention, the method is performed at a suitable operating printing temperature for the material of the first type of filaments and/or the second type of filaments.

Preferably, this operating temperature is the glass transition temperature of the printed part material, in order to soften and slightly enable shaping of the deposited filaments. If the first type of filament and the second type of filament are different materials, the operating temperature will be the lowest glass transition temperature of the glass transition temperatures of the two materials.

Typical values for the glass transition temperature are, for example, 143 ℃ for PEEK (polyetheretherketone), 50 ℃ for PA66 (e.g.nylon) and 105 ℃ for ABS (acrylonitrile-butadiene-styrene copolymer). Although the exact value of the glass transition temperature depends on the measurement technique, all known results provide values sufficiently similar to apply the present invention.

Furthermore, since the printing speed sets the residence time of the molten filaments on the filaments that have previously hardened, the printing speed may affect the convective heat exchange between the filaments/layers. However, for the purposes of the present invention as it contemplates, it has been found that with the use of conventional values, the impact of print speed on final performance is minimal.

The reduction of the temperature of the printed part from the operating temperature (usually defined in ℃/minute) then causes its solidification and, therefore, as the material shrinks and internal stresses begin, its final mechanical properties are affected. If the cooling rate is sufficiently slow, residual thermal stresses on the printed parts can mostly be avoided.

Accordingly, in a particular embodiment, the method further comprises the steps of: and cooling the part at a predetermined cooling rate. Preferably, this cooling rate is selected for such parts to achieve a certain degree of crystallinity. Most preferably, this crystallinity is at least 32%.

In a particular embodiment, the filaments of the first type and/or the filaments of the second type are made of a reinforcement of fibrous material embedded in a meltable material.

By depositing the fibrous material reinforcement with the meltable material, a lightweight design is achieved, since less material is needed to meet the structural requirements than if only meltable material is used.

According to the invention, the fibrous material reinforcement may be in the form of, for example, fibrils (very short and/or irregular fibers), nanofibers, carbon fillers, short fibers (length <1mm) or continuous fibers (extending continuously along the entire filament and thus along the entire length/width of the part at the time of manufacture). Preferably, the fibrous material reinforcement is in the form of continuous and/or short fibers, with continuous fibers being preferred.

Additionally, the fibrous material reinforcement may be glass fibers, carbon fibers, polymer fibers, or any other conventional material used as reinforcement. Among them, carbon fiber is preferable.

According to the invention, the meltable material may be a thermoplastic material, such as PA (polyamide), PPS (polyphenylene sulfide), PA66, ABS (acrylonitrile butadiene styrene), PEEK (polyether ether ketone), PAEK (polyaryletherketone) or PEKK (polyetherketoneketone). In a preferred embodiment, the meltable material is in the form of filaments for better storage and handling.

In a preferred embodiment, the meltable material is any one of the following thermoplastic materials: PEKK, PPS, PAEK, or PEEK. More preferably, the meltable material is PAEK or PEEK. Most preferably, the meltable material is PEEK or PPS.

In a preferred embodiment, the first type of filaments has a fiber volume content higher than 50% and the second type of filaments has a fiber volume content lower than 50%.

Advantageously, a fiber volume content of at least 50% enhances the mechanical properties of the final part, as this increases the hardness/weight ratio of the part. The fact that the second filaments have a smaller fiber volume content makes it easier to fill the voids without significantly reducing the mechanical properties of the final part.

In a particular embodiment, at least one of the second type of filaments is discontinuous, in the form of pellets or balls.

Preferably, the filaments of this second type in the form of pellets or balls are deposited uniformly on the channel.

If the second type of filament is a fibrous material reinforcement embedded within a meltable material in the form of pellets or balls, the fibrous material reinforcement is preferably in the form of fibrils, nanomaterials, carbon fillers or short fibers.

Further, some layers may be formed from a second type of filament having only a meltable material, other layers may be formed from a second type of filament having a fibrous material reinforcement embedded within a meltable material, or a combination of both.

Likewise, some layers may be formed of continuous second type filaments, while other layers may be formed of second type filaments in the form of pellets or balls, or a combination of both forms.

The part being manufactured may be formed entirely by alternating layers of filaments of the first type and filaments of the second type. That is, steps a) and b) are repeated to manufacture the entire part.

On the other hand, only a portion of the part may be printed by alternating the two layers (e.g., performing steps a) and b) only a certain number of times on the partially fabricated part). Thus, these alternating layers are deposited to better meet future load requirements during manufacturing and use. Thus, an optimized structural arrangement is achieved while saving printing time.

For example, any structural part designed with an overload zone or a critical zone that is typically oversized for safety reasons may benefit from the present invention by alternating the layers of two different filament types within this vulnerable section.

To further improve the tightness or reduce the problems of water absorption and adhesive detachment, in a particular embodiment, the method further comprises the steps of:

c. depositing at least a portion of the second type of filaments along the channel formed by the filaments having the first cross-sectional dimension to form a portion of the outer wall of the part.

Furthermore, in this embodiment, the outer wall of the part may be made entirely of the layer(s) of the second type of filaments, in order to further improve the dimensional tolerances.

It is noted that in this embodiment, the "layer" of filaments of the second type also comprises a bundle of non-layered filaments of the second type.

Advantageously, this allows the layer of filaments of the first type to be oriented according to the expected load, while the additional layer(s) of filaments of the second type are provided to compensate for the theoretical dimensions of the part. In other words, the strength requirements are not limited by dimensional tolerances.

In embodiments, a third type of filament or other type of filament may also be selectively deposited with the first type of filament and the second type of filament. Accordingly, this makes the method more versatile in application.

This third type of filament, or any other type of filament, has at least a different cross-sectional dimension than the first type of filament and the second type of filament, and may benefit from any feature defined with respect to the second type of filament, such as a discontinuity or cross-sectional area.

In a second inventive aspect, the present invention provides a layer-by-layer manufacturable part using additive manufacturing techniques according to any of the embodiments of the first inventive aspect. In a preferred embodiment, the part is an aerospace part.

All of the features described in this specification (including any accompanying claims, description and drawings), and/or all of the steps of the methods described, may be combined in any combination, except combinations where such features and/or steps are mutually exclusive.

Drawings

These and other features and advantages of the present invention will be clearly understood in view of the detailed description of the invention which follows, with reference to the accompanying drawings, which are given by way of example only and are not limiting of the preferred embodiments of the present invention.

Figure 1 this figure shows a layer made of filaments of a first type deposited alongside one another, with triangular voids introduced in the process.

Figure 2 this figure shows a layer made of filaments of the first type deposited alongside one another, with kite-shaped voids introduced in the process.

Fig. 3a, 3b fig. 3a shows a cross-sectional view of an alternately deposited layer made of filaments of a first type and filaments of a second type, fig. 3b shows a cross-sectional view of the same layer as fig. 3a, but with melted filaments of the second type filling the voids.

Figure 4 this figure shows a layer made of filaments of the second type arranged to compensate for external dimensions.

Detailed Description

Those skilled in the art will recognize that aspects described herein may be embodied as a method of making a part, or as a part itself.

The invention defines a method for layer-by-layer manufacturing of a part using additive manufacturing techniques, wherein the method comprises performing at least once the following steps:

a. forming a layer by depositing filaments of a first type, at least a portion of the filaments of the first type (1) being deposited alongside one another, thus creating at least one channel (3), an

b. Depositing at least a portion of the filaments of the second type (2) along the channel (3),

wherein the second type of filaments (2) differs from the first type of filaments (1) at least in cross-sectional dimension.

The method according to the invention uses an additive manufacturing tool comprising a printing chamber in turn containing a build sheet and at least one head configured to move over said build sheet and deposit a first type of filament (1) or a second type of filament (2).

If there is only one head, the head may be equipped with different nozzles that are interchangeable during the printing process, or with a single nozzle having a variable geometry and/or size. As mentioned, the head(s) may also comprise a heating block for heating the meltable filaments (1, 2) to any precise temperature.

The tool may further comprise a reel(s) for storing the filaments (1, 2).

In an embodiment, the head is configured to move along three translational axes (X, Y, Z) and/or rotate (about X, Y, Z) on the build sheet to print more complex geometries. Alternatively, the head(s) may be constrained to move over the build sheet only in the horizontal direction (X, Y), while movement in the vertical Z direction is performed by the build sheet, thereby enabling so-called 2.5D manufacturing. These movements are typically performed by actuators and/or servos, one for each direction and/or rotation.

Fig. 1 depicts layers made of filaments of the first type (1) deposited side by side to each other, these layers having triangular voids (3.1) created.

The triangular voids (3.1) introduced in the process occur when a single filament of the first type (1) is deposited on a channel (3) which is created by two filaments (1) of the same type deposited alongside one another.

It is to be noted that the channel (3) is, for the purposes of the present invention, produced when two filaments (1) of the same type are alongside one another, whereas the gap (3.1) introduced in the process needs to be produced by arranging further filament(s) (1) onto the two filaments, i.e. a closed perimeter is required.

Fig. 2 depicts layers made of filaments of the first type (1) deposited alongside one another, these layers having kite-shaped voids (3.2) created.

The kite-shaped interstices (3.2) occur when a pair of filaments (1) of the first type, which are arranged alongside one another, are deposited on a channel (3) which is created by two further filaments (1) of the same type, which are also deposited alongside one another.

Fig. 1 and 2 depict that the mechanisms that occur during hardening, which are dependent on gravity and temperature, cause the first type of filaments (1) to flatten.

Fig. 3a depicts a cross-sectional view of a hypothetical situation, where layers made of filaments of the first type (1) alternate with layers made of filaments of the second type (2), but not yet melted.

In this example, it can be observed that both the filaments of the first type (1) and the filaments of the second type (2) have a circular cross-sectional shape. However, other cross-sectional shapes may be selected or combined to maximize fill.

As can be seen in fig. 3a, the filaments of the second type (2) have been deposited along a channel (3) formed by a pair of filaments of the first type (1) deposited alongside one another below the filaments of the second type. In addition, two filaments of the second type are shown, which have been deposited thereon along two filaments of the first type, respectively, in order to fill the channel that would be created by a subsequent pair of filaments of the first type deposited alongside one another on the filaments of the second type.

Further, it can be seen that the first type of filaments (1) have a larger cross-sectional dimension than the second type of filaments (2). In fact, the specific cross-sectional dimensions of the second type of filaments are selected to fill such voids (3.1, 3.2) formed during deposition, thus taking into account the thermal expansion and contraction of the filaments (1, 2) during melting and hardening.

This situation of the second type of filaments (2) filling the previous voids during the deposition step can be seen in fig. 3 b.

As mentioned above, although not shown in the figures, a third or other type of filament may also be selectively deposited with the first type of filament and the second type of filament.

Fig. 4 depicts a layer of filaments of a first type (1) filled with filaments of a second type (2) oriented in a first direction. In addition, a set of layers made of filaments (2) of a second type oriented in a second direction different from the first direction can be seen in order to compensate for the external dimensions. Further, since these second type filaments (2) oriented in the second direction can be used as a support material, the printing process is facilitated.

Since the layer(s) of filaments (1) of the first type, which are usually reinforcing, can thus be oriented according to the expected load, these additional layer(s) of filaments (2) of the second type are provided to compensate for the theoretical dimensions of the part. As a result, the strength requirements may not be limited by dimensional tolerances.

Further, the method may comprise the steps of: depositing at least a portion of the filaments of the second type (2) along the channels (3) formed by the filaments of the first type (1) to form a portion of the outer wall of the part.

This embodiment may be suitable, for example, for producing localized rovings or fillers, and thus any area required for the final shape of the part, allowing more complex shapes to be produced.

In aeronautical parts, in particular 'T-profile' composite parts such as stringers, the roving is a composite filler adapted to fill the space between the two feet (i.e. the separation points of the two halves of the 'T-profile' composite part). Thus, a 'roving' is to be understood as a bundle of filaments of the second type, which may be unidirectional, non-woven or otherwise shaped in a pattern to provide structural continuity and avoid voids.

Furthermore, if the outer wall of the part is made entirely of the layer(s) of the second type of filaments (2), not only is the dimensional tolerance improved, but also the tightness that is produced prevents water absorption and bonding detachment.