WO2024224269A1

WO2024224269A1 - Equipment and process for the three-dimensional printing of composite materials

Info

Publication number: WO2024224269A1
Application number: PCT/IB2024/053903
Authority: WO
Inventors: Giuseppe GARABELLI; Gabriele Ottavio DE IACO; Gabriele NATALE; Tommaso GERI
Original assignee: Moi Composites S.R.L.
Priority date: 2023-04-24
Filing date: 2024-04-22
Publication date: 2024-10-31
Also published as: IT202300008037A1

Abstract

Equipment and a process for the three-dimensional printing of composite materials are described, said equipment comprising: - a feeding head for feeding at least one continuous filiform element; said continuous filiform element comprising at least one dispersed phase and at least one continuous phase - a movement assembly for the relative movement between the feeding head (50) and the three-dimensional object (20) to be printed and/or supporting surface (9); - at least one energy source (8) configured to deliver a pre-set amount of energy to said continuous filiform element (4); characterised in that said feeding head (50) comprises: at least one cutting device (2) arranged inside said feeding head (50).

Description

“EQUIPMENT AND PROCESS FOR THE THREE-DIMENSIONAL PRINTING OF COMPOSITE MATERIALS”

Field of the invention

The present invention refers to the field of the three-dimensional printing of composite materials.

In particular, the present invention refers to equipment and a method for the three- dimensional printing of fibre composite materials and thermoplastic or thermosetting matrix.

Known art

As known, the term “composite” generally means a material obtained by combining two or more components so that the end product has properties that differ from those of the individual constituents. In the technical field, in order to better identify what the term “composite” means, it is customary to limit the class of composite materials to reinforced materials only, in which at least one component, usually in the form of fibres, has much higher mechanical characteristics than the others.

In general, “composite material” or simply “composite” may be defined as the joining, by adhesion or cohesion, of two or more components different in shape and chemical composition, which are insoluble in each another and separated by an interface.

Composites generally consist of a continuous phase (called matrix) and a dispersed phase (often in the form of a reinforcing element). The dispersed phase is mainly responsible for mechanical properties of the material (strength and rigidity), whereas the continuous phase, on the other hand, is responsible for the task of transferring external loads applied to the dispersed phase. This transmission takes place due to shear stresses acting at the interface between dispersed phase and continuous phase. In addition, the matrix not only compressively stabilises the composite but also has the task of holding together and protecting the fibres and of shaping of the piece.

Ultimately, a composite material is a multiphase material that can be artificially created and is different from the constituents: depending on the principle of combined actions, the optimisation of a property is achieved by the careful and designed combination of two or more different materials. On the basis of the matrix material that constitutes the continuous phase, the composites are classified as metal matrix, ceramic matrix and polymer matrix.

The polymer matrix composites generally consist of reinforcing fibres (e.g. carbon, nylon, aramid or glass) embedded in a polymer matrix which surrounds, protects and binds the fibres. Typically, fibres constitute about 50/60% by volume of a polymer matrix composite.

In turn, inside the polymer matrix category, there are two subclasses of materials that compose the polymer matrix, which are: thermoplastic polymers and thermosetting polymers.

Thermoplastic polymers are a group of plastic materials that gain malleability under the action of temperature. Subject to the action of temperature, thermoplastic polymers can be moulded or formed into finished objects and, therefore, once cooled, revert to being rigid structures. Viscosity in fact decreases with the increasing of temperature but also with the increasing of the shear rate and shear stress. This heating/cooling cycle can theoretically be repeated multiple times depending on the qualities of the different plastic materials; in practice, it is possible to repeat the cycle for a limited number of times as too many heating cycles can degrade the polymers.

Thermosetting polymer materials have a cross-linked molecular structure formed by covalent bonds. The thermosetting polymers are cross-linked by means of a process called "curing", through which the resin in the fluid state undergoes a series of chemical transformations by passing through a gelled or gummy state until passing to the vitreous state. Some thermosetting resins are cross-linked by means of heat or through combined heat and pressure. In other cases, the chemical reaction may take place at room temperature (cold thermosets) by means of light radiation, evaporation of substances, activation by means of moisture and, finally, caused by the forced mixing of two elements (usually resin and catalyst).

Although thermosetting resin manufactured articles can soften by the effect of heat (Tg, glass transition temperature), the covalent bonds of the lattice prevent them from returning to the fluid state that existed before crosslinking, even better, if heating results in the degradation temperature being exceeded, they decompose by carbonising. Thermosetting materials cannot therefore be heated again and then melted as happens with thermoplastics.

Processes for the three-dimensional printing of composite materials are described, for example, in US9987798, US 10011073 and US9126367.

The Applicant observed that the processes for the three-dimensional printing of composite materials with continuous fibre reinforcement that are implemented with the aid of numerically controlled deposition systems or robots equipped with three or more degrees of freedom may have limitations in terms of the effectiveness of the cutting systems used to severe the filiform element.

In this case, the Applicant observed that cutting systems placed downstream of the end deposition apparatus are often used, however they are cumbersome and, therefore, limiting in terms of relative movement range between the deposition head and the object to be printed during the construction step.

This aspect limits the feasibility of making some three-dimensional objects to be printed, due to the bulkiness of the deposition head. Furthermore, since this type of cutting systems could involve a sequence of operations comprising the interruption of the deposition, the movement of the deposition head away from the three-dimensional object to be printed or from the supporting surface, the cutting of the filiform element and a new movement of approaching the deposition head to the three-dimensional object to be printed or said supporting surface, this causes an increase in the processing time for the printing of each three-dimensional object to be printed, in particular for the printing of three-dimensional objects, the making of which requires the filiform element to be severed during the same printing.

In addition, printing equipment that acts according to the sequence of operations described above makes it impossible to severe the filiform element at the exact point of contact between the end deposition apparatus and the three-dimensional object or the supporting surface. As a result, two portions of filiform elements are obtained, one of which, called severed flap, connected to the component being manufactured, is not processed similarly to the rest of the filiform element processed along the entire deposition trajectory, the other, called resulting flap, placed at the end of the reserve filiform element coming from the deposition head, will constitute the anchor point when starting the new deposition trajectory. This characteristic is limiting in terms of reproducibility and homogeneity of the process, thus introducing the risk of producing defects in the manufactured article.

Furthermore, the use of known cutting systems could be limiting as it is based on an extrusion operation following the cut of the filiform element, in order to ensure the correct repositioning of the severed flap. This solution is limiting in terms of materials that can be processed to only filiform elements that are intrinsically characterised by sufficient rigidity to ensure the extrusion. Limitations in miniaturisation of this type of configuration cause a minimum length of filiform element that is severed but still has to be laid, thus constraining the minimum length of the deposition trajectory that can be produced.

Therefore, the Applicant raised the issue of proposing equipment and a method for the three-dimensional printing of continuous fibre composite materials that solves the drawbacks of the known art, in particular in terms of limitations resulting from the known cutting systems and methods.

Summary of the invention

Therefore, in its first aspect, the invention concerns equipment for the three- dimensional printing of continuous fibre composite materials, comprising:

- a feeding head for feeding at least one continuous filiform element; said continuous filiform element comprising at least one dispersed phase and at least one continuous phase; said feeding head comprising at least one deposition apparatus arranged in its end portion;

- a movement assembly for the relative movement between the feeding head and the three-dimensional object to be printed and/or a supporting surface;

- an energy source configured to deliver a pre-set amount of energy to said continuous filiform element;

- characterised in that said deposition apparatus comprises:

- at least one cutting device arranged inside said feeding head; at least one conveyor movable between a retracted position, in which it is away from said cutting edge, and an intermediate position in which it is arranged substantially aligned with the extension direction of the continuous filiform element.

For the purposes of the present invention, the following definitions apply.

“Section of a filiform element” means the plane curve resulting from the intersection of the filiform element being laid with the plane having as normal the axis tangent to the deposition path. Said section is characterised by its own shape, area and perimeter.

“Longitudinal direction” generally means a direction parallel to the sliding direction of the continuous filiform element inside the deposition apparatus.

The present invention, in the aforesaid aspect, may have at least one of the preferred features described hereunder.

Preferably, the cutting device comprises at least one supporting arm and at least one cutting edge, which is movable between a retracted position in which, in plan view, said cutting edge is away from the extension direction of the continuous filiform element and a cutting position, in which the cutting edge intersects the extension direction of said continuous filiform element.

Conveniently, said cutting edge is partially or entirely made of materials and/or coatings adapted to severe the filiform element and wear resistant. For example, these can be chosen from steel alloys, ceramic materials, such as alumina, silicon carbide, tungsten carbide, boron nitride, silicon nitride and similar, ceramic matrix composites, metal matrix composites, metal, organo-ceramic and ceramic coatings.

Conveniently, the said at least one conveyor in intermediate position is arranged substantially aligned with the extension direction of the continuous filiform element, above the continuous filiform element and substantially below the cutting edge, when said cutting edge is in its cutting position.

Advantageously, the aforesaid at least one conveyor is, moreover, movable between a retracted position and a forward position and vice versa; the forward position movement causing the positioning of a resulting flap of the continuous filiform element, placed at the end of the filiform element of the reserve coming from the feeding head.

Preferably, the conveyor has, in plan view, a width equal to or greater than the width, in plan view, of the continuous filiform element.

The equipment advantageously comprises a movement assembly for moving said cutting device, configured to translate said cutting edge from the retracted position to the cutting position and vice versa.

Conveniently, the movement assembly comprises an actuator configured to move the supporting arm of the cutting edge.

Conveniently, the equipment comprises a movement assembly of said at least one conveyor, comprising at least one actuator configured to translate said conveyor from said retracted position to said intermediate position and vice versa.

According to another aspect, the present invention concerns a process for the three-dimensional printing of continuous fibre composite materials with the equipment referred to above and comprising the steps of:

- feeding at least one continuous filiform element to a deposition apparatus; said filiform element comprising at least one dispersed phase and at least one continuous phase capable of undergoing chemical and/or physical changes as a result of an energy delivery. The continuous filiform element may be wrapped around specially designed bobbins or may come from an impregnation device, not described as being of a known type, placed upstream of the outlet mouth and in such a way that at least one movement axis is interposed between said outlet mouth and said impregnation device;

- setting the aforesaid device to vary the shape of the section of the continuous filiform element,

- laying the continuous filiform element on a supporting surface or three- dimensional object;

- delivering a pre-set amount of energy to said filiform element so as to induce a chemical and/or physical change of said filiform element and, as a result of said change, producing an anchor point between said filiform element being laid and said supporting surface or three-dimensional object. Said continuous phase, constituting said filiform element, is selected to be capable of quickly producing said anchor point as a result of said chemical and/or physical change, thus making it possible to build the three- dimensional object. - displacing said feeding head with respect to the anchor point according to a preset path defining the object to be printed while exerting a tractive force onto said continuous filiform element. Said tractive force drives the outflow of said filiform element from the outlet mouth of the deposition apparatus and is generated as a result of the relative movement between the feeding head and said anchor point on the supporting surface and/or three-dimensional object;

- during the laying step, inducing said chemical and/or physical change in a new portion of the filiform element laid by said feeding head and, as a result of said change, producing, minute by minute, a new anchor point between said filiform element being laid and said supporting surface and/or three-dimensional object.

- cutting the continuous filiform element preferably inside the feeding head; during said cutting step, displacing at least one conveyor from a retracted position, in which it is away from said at least one cutting edge to an intermediate position where it is arranged substantially aligned with the extension direction of the continuous filiform element.

Preferably, the cutting step further comprises:

- displacing the said at least one conveyor from a retracted position, in which it is away from said at least one cutting edge, to an intermediate position in which it is under the cutting edge, when the latter is in its cutting position.

Preferably, in this conveyor position, the continuous filiform element wraps around the cutting edge and a head portion of the conveyor, thus forming an “s”.

Advantageously, the cutting step further comprises:

- displacing the said cutting edge from said cutting position to the retracted position and, in said movement, coming into contact with the continuous filiform element, so as to cause it to be cut.

Conveniently, the cutting step further comprises:

- displacing the said at least one conveyor from an intermediate position to a forward position, causing the positioning of the resulting flap from the continuous filiform element which has now been severed.

Preferably, the cutting step further comprises: - displacing the said at least one conveyor from a forward position to a retracted position, once a new anchor point between the filiform element being laid and the supporting surface or the three-dimensional object has been produced.

Further characteristics and advantages of the invention will become more apparent from the detailed description of some preferred, but not exclusive, embodiments of an apparatus and a process for the three-dimensional printing of fibre composite materials according to the present invention.

Brief description of the drawings

Such description will be set forth hereunder with reference to the accompanying drawings provided by way of example only and thus not limiting, in which:

- Figure 1 shows equipment for the three-dimensional printing of composite materials, comprising a movement assembly and feeding head, a supporting surface and a three-dimensional object and which implements the method according to the present invention;

- Figure 2 shows the feeding head of the equipment for the three-dimensional printing of composite materials of figure 1;

- figures 3a-3b show two bottom views, respectively in solid lines and in transparency, of an end portion of the feeding head according to the present invention;

- Figures 4a to 8b show subsequent moments of the cutting step of a continuous filiform element inside the end length of the feeding head;

- Figure 9 shows an inner perspective view of the deposition apparatus according to the present invention;

- Figure 10 shows an inner exploded perspective view of the deposition apparatus of figure 9, in which some components responsible for the cutting of the continuous filiform element have been omitted for the sake of representational clarity.

Detailed description of embodiments of the invention

With reference to the figures, equipment for the three-dimensional printing of fibre composite materials is denoted in its entirety by the reference numeral 100. In particular, the equipment 100 is adapted to the printing of a composite material starting from a continuous filiform element 4 consisting of at least one continuous phase and at least one dispersed phase.

The equipment 100 comprises a feeding head 50 of a continuous filiform element 4, a supporting surface 9 on which the continuous filiform element 4 is laid to make the preferably three-dimensional 20 object to be printed, a movement assembly for the relative movement between the feeding head 50 and the supporting surface 9, so as to exert traction on the continuous filiform element 4, at least one energy source 8 configured to deliver a pre-set amount of energy to the continuous filiform element 4. Said energy delivered to the continuous filiform element 4 causes a chemical and/or physical change thereof as a result of which an anchor point is produced between said continuous filiform element being laid and said supporting surface 9 and/or three- dimensional object 20. The relative movement between the feeding head and said supporting surface 9 and/or three-dimensional object 20 causes a tractive force on the same filiform element which causes it to flow out from the outlet mouth 10 of said deposition apparatus 1.

In the embodiment shown in the figures, the feeding head has a deposition apparatus 1 which is shown as a tubular element tapered in the direction of the outlet mouth 10 of the continuous filiform element 4.

The feeding head 50 further comprises internally a cutting device 2 comprising at least one cutting edge 3.

In the embodiment shown in the figures, the cutting device 2 comprises a supporting arm 6 for said cutting edge 3, which is movable between a retracted position (figs. 4a-4b) in which, in plan view, it is away from the extension direction X-X of the continuous filiform element 4, and a cutting position (figs. 5a-5b) in which the cutting edge 3 intersects the extension direction X-X of the continuous filiform element 4.

The supporting arm 6 extends substantially in accordance with the extension direction X-X of the continuous filiform element 4. In other words, in plan view, the supporting arm 6 is arranged substantially parallel or slightly inclined (less than 45°) to the extension direction X-X.

The supporting arm 6 has the aforesaid cutting edge 3 at one of its ends.

In another embodiment not shown in the figures, the cutting device 2 comprises, in addition to the supporting arm 6 and the cutting edge 3, an elastic element that allows the relative movement between the supporting arm 6 and the cutting edge 3. Preferably, the relative movement is of the rotary type and allows the cutting edge 3 to retract, thus allowing the step of moving forward toward the cutting position of the supporting arm 6 even in the event that the extension direction of the supporting arm 6 is intersecting with the extension direction X-X of the continuous filiform element 4. Preferably, the elastic element is a harmonic steel element arranged laterally to the supporting arm 6. Advantageously, the cutting edge 3 comprises a portion with a cam profile which, through the contact with the elastic element, allows the repositioning of the cutting edge 3 after the step of interacting with the continuous filiform element 4. Furthermore, advantageously, the cutting edge 3 comprises a portion counteracting the supporting arm 6, such as to allow a reaction force during the cutting step of the continuous filiform element 4 as the supporting arm 6 is retracted. According to this embodiment, the cutting device 2 cannot be moved away sideways from the extension direction X-X of the continuous filiform element and, since it is not necessary to avoid intersections between the extension direction of the supporting arm 6 and the extension direction X-X of the continuous filiform element 4, it is possible to vary the total length of the deposition apparatus 1 whenever advantageous, thus favouring the compactness of the feeding head 50 and/or the freedom of movement of the feeding head 50.

At the remaining end, the supporting arm 6 is functionally combined with a movement assembly 13 comprising an actuator 16 to move the supporting arm and, consequently, the same cutting edge.

In the embodiment shown in the figure, the actuator 16 is of the pneumatic type and comprises a piston cylinder 17 connected to the supporting arm 6 of the cutting edge 3, so that the movement of the piston cylinder 17 translates the supporting arm 6 and, consequently, the cutting edge 3 forwards or backwards.

The deposition apparatus 1 further comprises a conveyor 5 that is movable between a retracted position (figure 4a-4b), in which it is away from the cutting edge 3, an intermediate position (figure 6a-6b), in which it is arranged at least partially under said cutting edge and places the filiform element 4 in interference with the cutting edge 3, when the cutting edge 3 is in its cutting position, and a forward position (figure 8a-8b).

In the embodiment shown in the figures, the conveyor 5 is shown as a thin bar, which can be translated along the extension direction X-X of the continuous filiform element 4.

The conveyor 5 has, in plan view, a width L equal to or greater than the width, in plan view, of the filiform element 4, when this is considered to be upstream of the forming system.

The conveyor 5, at one of its leading heads 11, has an engagement portion 12 for engaging the continuous filiform element 4.

At the remaining end, the conveyor 5 is functionally combined with a movement assembly of the same conveyor comprising at least one actuator 18 that causes the translation of the conveyor 5 from its retracted position to the intermediate position and to its forward position, and vice versa.

In the embodiment shown in the figures, the actuator 18 comprises an electric motor 19 which actuates, by means of return pulleys 22, a conveying cable 21 combined with the conveyor 5.

The actuation of the electric motor shaft 19 in a direction brings the conveyor 5 forward, while the rotation of the electric motor shaft 19 in the opposite direction brings the conveyor 5 backward.

The feeding head 50 can be mounted on a rotary joint 30, which allows the infinite rotation of the feeding head 50 with respect to an end axis, such as, e.g., shown in figure 2.

The feeding head 50 may further comprise a device 40 to vary the shape of the section of the filiform element configured to impart a pre-set shape to the section of the filiform element being laid.

In other words, the device 40 for varying the shape of the section of the filiform element is adapted to reduce the number of gaps between side-by-side and/or overlapping filiform elements.

The device 40 for varying the shape of the section of the continuous filiform element comprises at least one surface configured to be placed in contact with the continuous filiform element 4 being laid, thus occupying at least one portion of the outer perimeter of the continuous filiform element 4 so as to define an empty portion on the outer perimeter of the forming element equal to or greater than 5% of the outer perimeter of the filiform element 4 being laid.

Thanks to the device 40 for varying the shape of the section of the continuous filiform element, the shape of the section of the continuous filiform element 4 is imparted by the combined containment action of at least one wall of the device 40 and the previously laid continuous filiform element and/or supporting surface.

Advantageously, for this purpose, the device 40 for varying the shape of the section of the continuous filiform element 4 comprises movable walls 41, 42, 43 arranged around the continuous filiform element 4. The latter slides between the movable walls 41, 42, 43 during the laying step on the supporting surface 9 and/or the three-dimensional object 20.

The movable walls 41, 42, 43 are movable, at least partially, towards or away from each other, to modify the aspect shape ratio of the section of the continuous filiform element 4.

In an embodiment shown for example in figures 8,9,10, there are at least two movable walls 41,42,43 configured to be in contact with the continuous filiform element 4 being laid, thus occupying at least one portion of the perimeter of the section of said continuous filiform element 4.

In detail, there are two side walls 41, 42 and an upper wall 43.

The side walls 41, 42 and the upper wall 43 are configured and arranged to cover at least 30% of the perimeter, in plan view, of the continuous filiform element 4.

The movable walls 41, 42, 43 are movable away from or closer to each other by means of specific actuators which are synchronously or asynchronously movable and can be independently actuated.

In the embodiment shown in figures 9-10, the side walls 41, 42 are like two elongated blades arranged internally inside the deposition apparatus 1 so as to be opposed to the continuous filiform element 4 when the latter is being laid.

The two side walls 41, 42 are configured to be in contact with the continuous filiform element 4 for at least one of their portion.

In particular, each side wall 41, 42 comprises a free end 41a, 42a and an end 41b constrained 42b to a head 44.

Preferably, the two side walls 41, 42 are configured to be in contact with the continuous filiform element 4 for at least 60% of the longitudinal extension of their said free end.

Even more preferably, the two side walls 41, 42 are configured to be in contact with the continuous filiform element 4 for at least 70% of the longitudinal extension of their said free end.

At their constrained end 41b, 42b, each side wall 41, 42 is functionally combined with a movement assembly of the same side wall, which comprises at least one actuator 45 which causes the translation of the side walls 41, 42, according to an inclination angle with respect to the longitudinal extension direction of the continuous filiform element 4.

The translation of the side walls 41, 42 brings at least the free ends 41a, 42a of the side walls closer to or away from each other, thus compressing the continuous filiform element 4 or allowing the lateral expansion thereof during or just before being laid.

In the embodiment shown in the figures, each actuator 45 comprises an electric motor 46 which drives, by means of a return pulley 47, a return cable 48 combined with a side wall 41, 42 by means of an elastic element 49.

The actuation of the electric motor shaft 46 in one direction exerts traction on the return cable 48 and a consequent compression on the elastic element 49, so that the side walls 41, 42 translate toward the electric motor 46, thus bringing their own free ends 41a, 42a away from each other. Conversely, the actuation in the opposite direction of the electric motor shaft 46 exerts a release on the return cable 48 and the elastic recovery of the elastic element 49, which is no longer counteracted by the tension of the return cable 48, causes the side walls 41, 42 to translate away from the electric motor 46, thus bringing the free ends 41a, 42a closer to each other and laterally compressing the continuous filiform element 4.

The upper wall 43 is also shown as an elongated blade arranged inside the deposition apparatus 1 so that to be positioned orthogonally to the two side walls 41, 42 and, with reference to the figures, above the continuous filiform element 4 when the latter is being laid.

The upper wall 43 is configured to be in contact with the continuous filiform element 4 for at least a portion thereof.

In particular, each upper wall 43 comprises a free end 43 a and an end 43b constrained to a head 52.

Preferably, the upper wall 43 is configured to be in contact with the continuous filiform element 4 for at least 60% of the longitudinal extension of said free end thereof.

Even more preferably, the upper wall 43 is configured to be in contact with the continuous filiform element 4 for at least 70% of the longitudinal extension of said free end thereof.

At its constrained end 43b, the upper wall 43 is functionally combined with a movement assembly of the same upper wall comprising at least one actuator 53 which causes the translation of the upper wall 43, with respect to the extension direction of the continuous filiform element 4.

The translation of the upper wall 43 compresses or allows the expansion of the continuous filiform element section according to a direction orthogonal to the side walls 41, 42 during or shortly before being laid.

In the embodiment shown in the figures, the actuator 53 comprises an electric motor 54 which drives, by means of a return pulley 55, a return cable 56 combined with the upper wall 43 by means of an elastic element 57.

The actuation of the electric motor shaft 54 in one direction exerts traction on the return cable 56 and a consequent compression on the elastic element 57, so that the upper wall 43 translates toward the electric motor 54, thus allowing the vertical expansion, i.e. denoted by the arrow F in the figure, of the shape of the section of the continuous filiform element 4. Conversely, the actuation in the opposite direction of the electric motor shaft 54 exerts a release on the return cable 56 and the elastic recovery of the elastic element 57, which is no longer counteracted by the tension of the return cable 56, causes the upper wall 43 to translate away from the electric motor 54, thus compressing the section of the continuous filiform element 4 vertically. The feeding head 50 is advantageously supported by a movement assembly for the relative movement between the same feeding head 50 and the three-dimensional object 20 to be printed or said supporting surface 9.

During the feeding of the continuous filiform element 4, the movement assembly exerts a tractive force on the continuous filiform element 4 and, consequently, transfers it to the continuous fibres contained therein.

It should be noted that this tractive force causes the outflow of said continuous filiform element 4 from the outlet mouth 10 of the deposition apparatus 1.

Consequently, the higher the relative speed, the faster the forward movement of the continuous filiform element 4.

According to an alternative embodiment, the feeding of the continuous filiform element 4 takes place by means of extrusion thereof from the feeding head 50.

According to an alternative embodiment, the tension caused on the filiform element as a result of the tractive force applied is modulated as a result of extrusion systems positioned upstream of the outlet mouth 10.

In further detail, the movement means comprise at least one machine with numerically controlled movement on at least three axes.

According to a first embodiment, the numerical control machine comprises a motorised arm 23 to support the feeding head 50 mentioned above at a respective end portion.

The motorised arm 23, which is not described in detail as it is of a known type, is adapted to move the feeding head in at least three spatial axes, by orienting the feeding head according to any position with respect to the object 20 or supporting surface 9.

It should be noted that the supporting surface 9, depicted as arranged under the feeding head 50, can, in turn, be relatively movable with respect to said feeding head 50. Said supporting surface 9 may consist of said continuous filiform element 4 previously laid in the course of making the three-dimensional object 20.

The equipment further comprises at least one energy source 8 specially configured to deliver a pre-set amount of energy to the continuous filiform element 4. According to a first embodiment, the aforesaid at least one energy source 8 may consist of a heat emission source provided to heat the continuous filiform element 4 and/or to cause the activation of chemical species causing a polymerisation reaction.

The energy sources 8 of this type may be based on the supply of a hot airflow, as those depicted in the figures.

Alternatively, the aforesaid at least one energy source 8 may be a source of electromagnetic radiation used to heat said filiform element and/or to cause the activation of chemical species causing a polymerisation reaction. In this case, the energy source 8 may, e.g., consist of at least one source of electromagnetic radiation source in the field of infrared and/or ultraviolet, depending on the type of material of which the continuous filiform element 4 is composed. The energy source 8 is positioned downstream of the deposition apparatus 1 and is configured to deliver energy to the continuous filiform element 4.

Preferably, the aforesaid at least one energy source 8 is constituted by an energy source with adjustable power and/or by a movement device configured to modify the relative distance between the energy source 8, or one of its elements, and the continuous filiform element 4 being laid.

For example, if the energy source 8 is based on the generation of a hot airflow adapted to strike the continuous filiform element 4 being laid, process stability can be achieved by modulation of the airflow, in terms of flow rate and/or temperature and/or the use of a movement device that modifies the relative distance between the energy source 8 and the continuous filiform element 4.

For example, if the energy source 8 is an electromagnetic radiation source focused by means of an optical element, the modification in the geometric configuration of the radiation incident the continuous filiform element 4 can be achieved either by means of a movement device that modifies the relative distance between the energy source 8 and the continuous filiform element 4 (i.e. moving away/closer) or by using an actuated optical element, i.e. capable of modifying its position.

Another problem inside systems for the three-dimensional printing of composite material manufactured articles with continuous fibre reinforcement, with the aid of numerically controlled deposition systems or robots equipped with 3 or more degrees of freedom, is the lack of control over the tension shown by the filiform element being laid.

For this purpose, the equipment according to the present invention further comprises a device for controlling the tension shown by the continuous filiform element 4 being laid.

Said device comprises at least one tension sensor, for the measurement of the tension of the continuous filiform element 4, and at least one actuating element configured for compensating unwanted tension variations of the continuous filiform element 4.

The aforesaid at least one sensor may be a sensor configured to measure tension directly, as in the case of using force sensors, or a sensor configured for an indirect tension measurement, preferably through the synergistic use of an angular and/or linear position sensor and at least one elastic element.

Preferably, the aforesaid at least one sensor is a sensor configured for an indirect measurement of the tension.

In these cases, it is conveniently possible to provide the control device with a counterweight having a mass equivalent to the sum of the mass of the system to be counterbalanced. The addition of a counterweight allows the continuous filiform element 4 to have lower tensions since, despite the accelerations of the numerical control machine, the inertia of the system is compensated by the inertia of the counterweight. This ensures that the elastic element, which is part of the tension measurement sensor of said continuous filiform element 4, will undergo a variation in its characteristic length solely caused by the tension present on the continuous filiform element 4.

The actuating elements may act by rotating the bobbin(s) on which the filiform element is wound, thus causing the filiform element to unwind, resulting in the feeding of said continuous filiform element 4 and/or imparting a tractive force on the continuous filiform element 4.

The latter effect can be achieved, e.g., by using two counter-rotating rollers or by means of a series of rollers, at least one of which is actuated, which operate by the effect of friction with the continuous filiform element 4. In this last case, moreover, the last rollers of the series of rollers may be equipped with a one-way clutch to ensure tension on the continuous filiform element 4 in the event of retraction thereof. The present invention further relates to a method for the three-dimensional printing of composite materials that comprises the steps of:

- feeding at least one continuous filiform element 4 to a deposition apparatus 1; said continuous filiform element 4 comprising at least one dispersed phase and at least one continuous phase capable of undergoing chemical and/or physical changes as a result of an energy delivery.

- setting the aforesaid device to vary the shape of the section of the continuous filiform element;

- laying the continuous filiform element on a supporting surface or three- dimensional object, by imparting a shape to the section of said continuous filiform element by means of combined containment action of the at least one wall of the said device and of the previously laid continuous filiform element and/or supporting surface.

- delivering a pre-set amount of energy to said filiform element so as to induce a chemical and/or physical change in said filiform element and, as a result of said change, to produce an anchor point between said filiform element being laid and said supporting surface and/or three-dimensional object. Said continuous phase, constituting said continuous filiform element 4, is selected to be capable of quickly producing said anchor point as a result of said chemical and/or physical change, making it possible to build the three-dimensional object.

- displacing said feeding head with respect to the anchor point according to a preset path defining the object to be printed while exerting a tractive force onto said continuous filiform element. Said tractive force drives the feeding of said filiform element through the feeding head and is generated as a result of the relative movement between the feeding head and said anchor point on the supporting surface or three-dimensional object.

- during the laying step, inducing said chemical and/or physical change in a new portion of the filiform element laid by said feeding head and, as a result of said change, determining, minute by minute, a new anchor point between said filiform element being laid and said supporting surface or three-dimensional object.

- cutting the continuous filiform element inside the feeding head. The feeding and laying steps are carried out by exerting a dragging force on the continuous filiform element 4 made by means of relative movement between the feeding head 50 and the three-dimensional object 20 to be printed or between the feeding head 50 and the supporting surface 9.

In other words, by displacing the feeding head 50 by means of the action of the numerical control machine, the continuous filiform element 4 is gradually laid on the supporting surface 9 or on a previously made portion of said three-dimensional object 20 which is produced by feeding the continuous filiform element 4 and producing subsequent anchor points.

The deposition of the continuous filiform element 4 may then proceed according to predefined paths and trajectories adapted to form the three-dimensional object 20 to be printed.

The anchor point thus formed allows the continuous filiform element 4 to be arranged on the supporting surface 9 according to a precise path and to draw the object to be printed 20 while the numerical control machine is moving.

The feeding head 50 is thus displaced by the numerical control machine according to a pre-set path that defines the object 20 to be printed.

This path is determined by suitable management software which is not described in the present description since it does not fall within the scope of the invention.

At the end of the printing process, or in any case when the continuous feeding of the continuous filiform element 4 has to be interrupted, said filiform element is cut by a cutting device 2 advantageously placed inside the feeding head 50.

In order to implement the cutting step, the cutting edge 3 is displaced from a retracted position in which, in plan view, it is away from the extension direction X-X shown in figures 4a-4b of the continuous filiform element 4, to a second cutting position shown in figures 5a-5b, in which the cutting edge 3 intersects the extension direction X- X of the continuous filiform element 4.

In the retracted position, the cutting edge 3 and the supporting arm 6 are arranged laterally with respect to the extension direction X-X.

In particular, the supporting arm 6 is arranged so that its extension forms an angle a less than or equal to 45° with the extension direction X-X.

Instead, in the cutting position, as shown in figures 5a-5b, the cutting edge 3 is below the continuous filiform element 4, preferably without touching it and thus intersecting the extension direction X-X.

To move the cutting edge 3, the actuator 16 is operated, which actuator displaces the supporting arm 6 and consequently the cutting edge 3 shown in figure 5a, 5b, by bringing it to the cutting position.

In the retracted position of the conveyor 5, figures 4a, 4b, the latter is arranged substantially aligned with the extension direction X-X of the continuous filiform element 4, above and without being in interference with the continuous filiform element 4.

In other words, when considering a vertical direction such as the one represented by the vertical axis Z-Z, the continuous filiform element 4 is above the cutting edge 3 but below the conveyor 5.

At this point, the conveyor 5, which is operated by a specific actuating system 18, also moves from its retracted position, in which it is away from the cutting edge 3 (shown in figures 5a, 5b) to an intermediate position shown in figures 6a, 6b, in which it is under the cutting edge 3, when the latter is in its cutting position.

In the intermediate position of the conveyor 5, figure 6a, 6b, the latter is arranged substantially aligned with the extension direction X-X of the continuous filiform element 4.

In this position of the conveyor 5, the continuous filiform element 4, in particular its length arranged in proximity of the engagement portion 12, wraps the cutting edge 3 and the head portion 11 of the conveyor 5, thus forming an “s”.

At this point, the cutting edge 3 is brought again to the retracted position, during this movement the cutting edge 3 comes into contact with the continuous filiform element 4, thus resulting in the cutting thereof, figures 7a, 7b.

Subsequently, the conveyor 5 is further moved forward, i.e. further away from the retracted position, to a forward position shown in figures 8a, 8b. In this position, the continuous filiform element 4 is now cut, while the leading head 11 of the conveyor comprising the engagement portion 12 comes out frontally from the outlet mouth 10 of the deposition apparatus 1, thus engaging the resulting flap of the filiform element for its new positioning to form a new anchor point for the subsequent laying step.

In the forward position, the conveyor 5 is substantially under the cutting edge 3, which is in its retracted position. The continuous filiform element 4 is below the conveyor 5, except for its free end portion.

At the exit of the outlet mouth 10, before or after cutting, the energy source 8 delivers a pre-set amount of energy to said continuous filiform element 4 so as to induce a chemical and/or physical change in said filiform element and, as a result of said change, to produce one anchorage point between said filiform element being laid and said supporting surface 9 and/or three-dimensional object 20. The transformation of the continuous filiform element 4 into the composite material is triggered in proximity and downstream of the outlet mouth 10, thus consequently determining an anchor point between the continuous filiform element 4 being laid and the supporting surface 9 and/or three-dimensional object 20.

Before or during the laying step of the continuous filiform element 4 according to the pre-set trajectory, the continuous filiform element 4 may undergo a forming step to change the shape of the section.

For this purpose, the forming device 40 is set by moving the aforesaid movable walls 41, 42, 43 towards or away from each other.

With reference to the embodiment shown in the figures, the side walls 41, 42 and/or the upper wall 43 may be at least partially moved towards/away from each other in order to compress the continuous filiform element 4 both laterally and vertically.

As previously mentioned, the setting step can be implemented during the laying step.

Alternatively or in a combined way, the setting step can be implemented upstream of the laying step.

Advantageously, the method described may be applied to the making of geometries characterised by curvatures in the stratification direction of the three- dimensional object by setting said forming device 40 dynamically, during the laying step of said continuous filiform element 4. Advantageously, the method described may be applied to the deposition of continuous filiform element(s) having deposition trajectory(s) at least partially intersecting on the same plane or surface, by dynamically setting said forming device 40 during the laying step of said continuous filiform element 4. The invention, as can be clearly inferred from the above description, allows to overcome the limitations of the equipment and processes for the three-dimensional printing of fibre composite materials, which are known particularly in terms of limitations of the methods for forming the continuous filiform element.

Several modifications can be made to the embodiments described in detail, all anyhow remaining within the protection scope of the invention, as defined by the following claims.

Claims

1. Equipment (100) for the three-dimensional printing of continuous fibre composite materials, comprising:

-a feeding head (50) for feeding at least one continuous filiform element (4); said continuous filiform element (4) comprising at least one dispersed phase and at least one continuous phase;

-a movement assembly for the relative movement between the feeding head (50) and the three-dimensional object to be printed (20) or supporting surface (9);

-at least one energy source (8) configured to deliver a pre-set amount of energy to said continuous filiform element (4); characterised in that said deposition apparatus (1) comprises:

-at least one cutting device (2) arranged internally to said feeding head (50); at least one conveyor (5) movable between a retracted position, in which it is away from said cutting edge (3), and an intermediate position in which it is arranged substantially aligned with the extension direction (X-X) of the continuous filiform element (4).

2. Equipment (100) for the three-dimensional printing of continuous fibre composite materials according to claim 1, characterised in that said cutting device (2) comprises at least one supporting arm (6) and at least one cutting edge (3) which can be moved between a retracted position in which, in plan view, said cutting edge (3) is away from the extension direction (X-X) of the continuous filiform element (4) and a cutting position wherein said cutting edge (3) intersects the extension direction (X-X) of said continuous filiform element (4), and vice versa.

3. Equipment (100) for the three-dimensional printing of continuous fibre composite materials according to claim 1, characterised in that said at least one conveyor (5), in said intermediate position, is arranged substantially aligned with the extension direction (X-X) of the continuous filiform element (4), above the continuous filiform element (4) and substantially below said cutting edge (3), when said cutting edge is in its cutting position, and vice versa.

4. Equipment (100) for the three-dimensional printing of continuous fibre composite materials according to claim 3, characterised in that said at least one conveyor (5) is further movable between a retracted position and a forward position, and vice versa; the forward position movement causing the positioning of a flap resulting from the continuous filiform element (4) placed at the end of the filiform element of the reserve coming from the feeding head (50).

5. Equipment (100) for the three-dimensional printing of continuous fibre composite materials according to claim 1, characterised in that said conveyor (5) has, in plan view, a width (L) equal to or greater than the width in plan view of said continuous filiform element (4).

6. Equipment (100) for the three-dimensional printing of continuous fibre composite materials according to any one of preceding claims 1 to 5, characterised by comprising a movement assembly for moving said cutting device (2) comprising an actuator (16) configured to move said cutting edge (3).

7. Equipment (100) for the three-dimensional printing of continuous fibre composite materials according to any one of preceding claims 1 to 6, characterised by comprising a movement assembly (18) for moving said at least one conveyor (5) comprising at least one actuator (19) configured to move said conveyor (5) from said retracted position to said intermediate and forward position and vice versa.

8. Process for the three-dimensional printing of continuous fibre composite materials with the equipment (100) according to any one of the preceding claims, comprising the steps of:

- feeding at least one continuous filiform element (4) to a feeding head (50); said continuous filiform element (4) comprising at least one dispersed phase and at least one continuous phase:

- laying the continuous filiform element (4) on a supporting surface (9) and/or on a three-dimensional object (20);

- delivering a pre-set amount of energy to said continuous filiform element (4) so as to induce a chemical and/or physical change of said filiform element and, as a result of said change, to produce at least one anchor point between said continuous filiform element being laid and said supporting surface and/or three-dimensional object; - displacing said feeding head (50) with respect to the anchor point according to a pre-set path which defines the object to be printed (20);

- cutting the continuous filiform element (4) inside the feeding head (50); in said cutting step, displacing said at least one conveyor (5) from a retracted position, in which it is away from said at least one cutting edge (3), to an intermediate position in which it is arranged substantially aligned with the extension direction (X-X) of the continuous filiform element (4).

9. Process for the three-dimensional printing of continuous fibre composite materials according to claim 8, characterised in that said cutting step comprises:

- displacing the said cutting edge (3) from a retracted position in which, in plan view, it is away from the extension direction (X-X) of the continuous filiform element (4) to a cutting position in which the said cutting edge (3) intersects the extension direction (X-X) of the continuous filiform element (4).

10. Process for the three-dimensional printing of continuous fibre composite materials according to claim 8 or 9, characterised in that in said cutting step the said conveyor (5) is displaced to an intermediate position, in which it is under the cutting edge (3), when the latter is in its cutting position.

11. Process for three-dimensional printing of continuous fibre composite materials according to claim 10, characterised in that in said intermediate position of the conveyor (5), the continuous filiform element (4) wraps around the cutting edge (3) and a head portion (11) of the conveyor (5), thus forming an “s”.

12. Process for the three-dimensional printing of continuous fibre composite materials according to claim 10, characterised in that said cutting step comprises:

- displacing said cutting edge (3) from said cutting position to the retracted position and, in said movement, coming into contact with the continuous filiform element (4), so as to cause it to be cut.

13. Process for the three-dimensional printing of continuous fibre composite materials according to claim 10, characterised in that said cutting step comprises:

- displacing the said at least one conveyor (5) from an intermediate position to a forward position, causing the positioning of a resulting flap from the continuous filiform element (4) which has now been severed.