Additive manufacturing machine, extruder for said machine and method of additive manufacturing

Abstract

An extruder for an additive manufacturing machine has a first and second extrusion duct (6, 7) separated from each other; a first and a second feeding system (8, 9), configured to feed a first and a second material into the first and the second extrusion duct (6, 7); a first and a second heating assembly (10, 11) configured to heat the first and the second material so as to determine the melting of the first and the second material; a mixing chamber (12), which is configured to allow the mixing of the first and of the second melt material exiting from the first and from the second extrusion duct (6, 7); and a control unit (14), configured to independently control the first and the second feeding system (8, 9) and the first and the second heating assembly (10, 11).

Description

[0001] "ADDITIVE MANUFACTURING MACHINE , EXTRUDER FOR SAID MACHINE AND METHOD OF ADDITIVE MANUFACTURING"

[0002] Cross-Reference to Related Applications

[0003] This Patent Appl ication claims priority from Italian Patent Application No . 102024000006898 filed on March 27 , 2024 , the entire disclosure of which is incorporated herein by reference .

[0004] Field of the Art

[0005] The present invention relates to an additive manufacturing machine and an extruder for said additive manufacturing machine .

[0006] Further, the present invention relates to a method of additive manufacturing .

[0007] State of the Art

[0008] As is well known, additive manufacturing is used to make products and semi- finished products , even large-si zed ones , which require lightness , strength and have complex geometries such as , for example , bodies and frames in the nautical , aeronautical and automotive industries , machinery components and architectural structures from a digital three-dimensional model file created using a CAD modelling system .

[0009] By way of example , additive manufacturing techniques using fused deposition modelling technology ( FDM) or Fused Filament Fabrication ( FFF) or Fused Granular Fabrication ( FGF) are known .

[0010] Typically, known additive manufacturing techniques are based on the use of a printhead equipped with an extruder having a noz zle from which filaments of melted material emerge . Speci fically, these filaments of melted material are laid in layers on a work surface , according to a predefined three-dimensional pattern .

[0011] Once laid down by the noz zle , the layer of melted material solidi fies immediately and bonds to an adj acent layer of material . The succession of superimposed layers thus forms a single solid structure or final obj ect of a desired shape .

[0012] In order to manufacture large obj ects , additive manufacturing machines are known to employ Fused Granular Fabrication techniques , which involve the steps of feeding a material in granular form into the extruder, heating said material inside an extruder heating chamber so as to melt the material , conveying said melted material to the extruder noz zle by means of a conveyor device such as a worm screw, and dispensing melted filaments of the material from said noz zle .

[0013] In general , the speed of making the final obj ect is a parameter of fundamental importance for additive manufacturing techniques and becomes even more important when said final obj ect is large .

[0014] In order to achieve high melt flow rates and, consequently, increase the speed o f production of the final obj ect , additive manufacturing machines employing Fused Granular Fabrication techniques are generally equipped with an extruder of considerable si ze and length, which limits the working volume and increases the footprint of the additive manufacturing machine . Furthermore , large extruders have di f ficulty maintaining a homogeneous melt flow when feeding low material flow rates . Generally, when the flow rate fed by the extruder falls below 20% of the maximum flow rate , the melt coming out of the noz zle is typically inhomogeneous .

[0015] In addition, known additive manufacturing machines are inflexible because they are designed to extrude one particular material at a time , with constant chemical and physical characteristics .

[0016] Summary of the Invention

[0017] An obj ect of the present invention is to provide an extruder for an additive manufacturing machine that mitigates the drawbacks of the prior art disclosed herein .

[0018] In accordance with the present invention, an extruder for an additive manufacturing machine is provided, the extruder comprising :

[0019] - a first extrus ion duct and a second extrusion duct separated from each other ;

[0020] - a first feeding system and a second feeding system, which are configured to feed a first material into the first extrusion duct and a second material into the second extrusion duct , respectively; a first heating assembly and a second heating assembly, which are configured to heat the first material in the first extrusion duct and the second material in the second extrusion duct , respectively, so as to determine the melting of the first and of the second material ;

[0021] - a mixing chamber, which is in fluidic communication with the first and the second extrusion duct and is configured to allow the mixing of the first and of the second melt material exiting from the first and from the second extrusion duct ;

[0022] - a noz zle , which is fluidically connected to the mixing chamber and is configured to dispense mixed melt filaments of the first and of the second materials ; and

[0023] - a control unit , which is in communication with the first and the second feeding system and with the first and the second heating assembly and is configured to independently control the first and the second feeding system and to independently control the first and the second heating assembly .

[0024] Thanks to the present invention, it is possible to increase the speed at which the additive manufacturing machine produces the final obj ects and, at the same time , precisely adj ust the chemical-physical characteristics of the material of the final obj ects .

[0025] In practice , the extruder compri ses two independent extrusion ducts arranged in parallel so as to double the flow rate of melt material fed to the noz zle .

[0026] Furthermore , the fact that the first and second extrusion ducts are separate allows the control unit to independently regulate the temperature and flow rate of the first and second material in order to control the chemical and physical properties , such as viscosity, of the first and second material .

[0027] In other words , it is possible to extrude two di f ferent materials simultaneously and in various configurations . In this way, the shape and relative proportions of the two materials can be varied and calibrated as desired . By way of example , it is possible to obtain a third material comprising an inner core composed of the first material and an outer layer composed of the second material .

[0028] Speci fically, the extruder comprises a first inlet duct and a second inlet duct configured to feed the first and second material in granular form into the first and second extrusion ducts , respectively .

[0029] Thus , it is possible to carry out the process of Fused Granular Fabrication by means of the extruder made in accordance with the present invention .

[0030] Speci fically, the first heating assembly comprises a plurality of first heating elements arranged around the first extrusion duct and the second heating assembly comprises a plurality of second heating elements arranged around the second extrusion duct .

[0031] In this way, the heating elements can be switched on and of f independently of each other to precisely regulate the temperature o f the first and second material inside the first and second extrusion duct respectively .

[0032] In particular, the first feeding system comprises a first transport member, preferably a first worm screw, which is arranged within the first extrusion duct and is configured to convey the first material towards the mixing chamber ; the second feeding system comprises a second transport member, preferably a second worm screw, which is arranged within the second extrusion duct and is configured to convey the second material towards the mixing chamber .

[0033] In this way, the flow rate of the first material and the second material in the first and second extrusion duct respectively can be precisely and independently regulated .

[0034] In particular, the extruder comprises a first flow rate sensor, which is in communication with the control unit and is configured to detect a first flow rate of the first material within the first extrusion duct , and a second flow rate sensor, which is in communication with the control unit and is configured to detect a second flow rate of the second material within the second extrusion duct ; the control unit being configured to control the first and second feed systems according to the first and / or second flow rates detected .

[0035] In this way, it is possible to precisely and independently control the flow rates of the first and second material fed by the first and second extrusion duct respectively .

[0036] In particular, the extruder comprises a first temperature sensor, which is in communication with the control unit and is configured to detect a first temperature of the first material within the first extrusion duct , and a second temperature sensor, which is in communication with the control unit and is configured to detect a second temperature of the second material within the second extrusion duct ; the control unit being configured to control the first and second heating assemblies according to the first and / or second temperature detected .

[0037] In this way, the temperatures of the first and second material in the first and second extrusion duct can be precisely and independently controlled . In more detail , it is possible to provide closed-loop temperature control of the first material and the second material in the f irst and second extrusion duct respectively, by feedback of the first and second temperatures detected by the first and second temperature sensor .

[0038] In particular, the extruder comprises a first pressure sensor, which is in communication with the control unit and is configured to detect a first pressure of the first material within the first extrusion duct , and a second pressure sensor, which is in communication with the control unit and is configured to detect a second pressure of the second material within the second extrusion duct ; the control unit being configured to control the first and the second feeding system according to the first and / or the second pressure detected .

[0039] In particular, the first extrusion duct comprises a first end section, which flows into the mixing chamber, and the second extrusion duct comprises a second end section, which flows into the mixing chamber ; the first and second end sections being mutually inclined at a V angle .

[0040] This facilitates the mixing of the first and second material in the mixing chamber .

[0041] In accordance with a variant of the present invention, the first and second end sections are substantially parallel .

[0042] In this way, the extruder can be easily tilted in use and additional elements can be added to the extruder by placing them in the space between the first and second extrusion ducts .

[0043] A further obj ect of the present invention is to provide an additive manufacturing machine that mitigates the drawbacks of the prior art highlighted herein .

[0044] In accordance with the present invention, an additive manufacturing machine comprising the extruder as previously described is provided .

[0045] A further obj ect of the present invention is to provide a method of additive manufacturing that mitigates the drawbacks of the prior art highlighted herein .

[0046] In accordance with the present invention, an additive manufacturing method is provided comprising the steps of :

[0047] - feeding a first material into a first extrusion duct via a first feeding system;

[0048] - feeding a second material into a second extrusion duct separated from the first extrusion duct through a second feeding system;

[0049] - independently controlling the first and the second feeding system;

[0050] - heating the f irst material in the first extrusion duct through a first heating assembly so as to determine the melting of the first material ;

[0051] - heating the second material in the second extrusion duct through a second heating assembly so as to determine the melting of the second material ;

[0052] - independently controlling the first and the second heating assembly;

[0053] - mixing the first and the second melt material exiting from the first and from the second extrusion duct respectively; and

[0054] - dispensing mixed melt filaments of the first and of the second material from a noz zle . Thanks to this method, final obj ects can be produced quickly and the chemical-physical material properties of the final obj ects can be precisely regulated .

[0055] Brief Description of the Drawings

[0056] Further characteristics and advantages of the present invention will become clear from the following description of non-limiting examples of embodiment thereof , with reference to the figures of the attached drawings , in which :

[0057] - Figure 1 is a perspective view, with parts removed for clarity' s sake and parts shown schematically, of an additive manufacturing machine made in accordance with the present invention;

[0058] - Figure 2 is a perspective view, with parts removed for clarity ' s sake , of an extruder of the additive manufacturing machine in Figure 1 ;

[0059] - Figure 3 is a sectional view, with parts removed for clarity' s sake and parts shown schematically, of the extruder in Figure 2 ; and

[0060] - Figure 4 is a perspective view, with parts removed for clarity' s sake , of the extruder in Figure 2 made in accordance with a variant of the present invention .

[0061] Detailed Description of the Invention

[0062] With reference to Figure 1 , the number 1 denotes an additive manufacturing machine used to make obj ects from a material preferably of the polymer or composite type .

[0063] In accordance with a non-limiting embodiment of the present invention, the additive manufacturing machine 1 is used to manufacture an obj ect by means of Fused Granular Fabrication ( FGF) techniques and employs a three-dimensional model of the obj ect to be manufactured .

[0064] The additive manufacturing machine 1 comprises a printhead 2 equipped with an extruder 3 , and a robot 4 , speci fically an anthropomorphic robot , to support the printhead 2 and control the position and orientation of the extruder 3 . In particular, the robot 4 comprises a plurality of articulated arms 5 , rotating about respective axes of rotation .

[0065] With reference to Figures 2 and 3 , the extruder 3 comprises an extrusion duct 6 and an extrusion duct 7 separated from each other ; a feeding system 8 and a feeding system 9 , which are configured to respectively feed a first material into the extrusion duct 6 and a second material into the extrusion duct 7 ; a heating assembly 10 and a heating assembly 11 , which are configured to respectively heat the first material in the extrusion duct 6 and the second material in the extrusion duct 7 so as to determine the melting of the first and second materials ; a mixing chamber 12 , which is in fluidic communication with the extrusion ducts 6 and 7 and is configured to allow mixing of the first and second melt materials exiting the extrusion ducts 6 and 7 ; a noz zle 13 , which is fluidically connected to the mixing chamber 12 and is configured to dispense mixed melt filaments of the first and second materials ; and a control unit 14 , which is in communication with the feeding systems 8 and 9 and the heating as semblies 10 and 11 and is configured to independently control the feeding systems 8 and 9 and to independently control the heating assemblies 10 and 11 . In accordance with a non-limiting embodiment of the present invention, the first and second materials have di f ferent physical and / or chemical characteristics . In more detail , the first and second materials are polymeric .

[0066] In particular, the heating assembly 10 comprises a plurality of heating elements 15 arranged around the extrusion duct 6 and the heating assembly 11 comprises a plurality of heating elements 16 arranged around the extrusion duct 7 .

[0067] In the case described and illustrated here , each heating element 15 , 16 is annular-shaped and is fitted around the respective extrus ion duct 6 , 7 . In particular, each heating element 15 , 16 comprises a respective ceramic resistor .

[0068] Speci fically, the extrusion duct 6 extends along a longitudinal axis Al and the extrusion duct 7 extends along a longitudinal axis A2 transverse to the longitudinal axis Al .

[0069] In more detail , the extrusion duct 6 comprises an end section 21 , which flows into the mixing chamber 12 , and the extrusion duct 7 comprises an end section 22 , which flows into the mixing chamber 12 . The end sections 21 and 22 are mutually inclined at a V angle .

[0070] With reference to Figure 3 , the feeding system 8 comprises a transport member 23 , which is arranged within the extrusion duct 6 and is configured to convey the first material towards the mixing chamber 12 . The feeding system 9 comprises a transport member 24 , which is arranged within the extrusion duct 7 and is configured to convey the second material towards the mixing chamber 12 . In particular, the feeding system 8 comprises an actuator 25 , such as an electric motor, configured to drive the transport member 23 , and the feeding system 9 comprises an actuator 26 , such as an electric motor, configured to drive the transport member 24 .

[0071] In more detail , the feeding system 8 comprises a transmission 27 , which mechanically connects the actuator 25 to the transport member 23 . The feeding system 9 comprises a transmission 28 , which mechanically connects the actuator 26 to the transport member 24 .

[0072] In the non-limiting embodiment of the present invention described and illustrated herein, each transport member 23 , 24 comprises a respective worm gear 29 , 30 .

[0073] In more detail , in addition to conveying the first and second material towards the mixing chamber 12 , the worm screws 29 and 30 contribute to heating the first material in the extrusion duct 6 and the second material in the extrusion duct 7 , respectively .

[0074] Further, the extruder 3 comprises an inlet duct 32 and an inlet duct 33 configured to feed the first and second material in granular form into the respective extrus ion ducts 6 and 7 , respectively .

[0075] Speci fically, each inlet duct 32 , 33 extends along a respective longitudinal axis A3 , A4 substantially transverse to the longitudinal axes Al and A2 .

[0076] In other words , each inlet duct 32 , 33 is in fluidic communication with the respective extrusion duct 6 , 7 .

[0077] In accordance with the present invention, the extruder 3 comprises a flow rate sensor 34 , which is in communication with the control unit 14 and is configured to detect a first flow rate of the first material in the extrusion duct 6 , and a flow rate sensor 35 , which is in communication with the control unit 14 and is configured to detect a second flow rate of the second material in the extrusion duct 7 . The control unit 14 is configured to control the feeding systems 8 and 9 according to the first and / or second flow rate detected .

[0078] In particular, the flow rate sensors 34 and 35 are configured to respectively emit a first flow rate signal indicative of the first flow rate of the first material in the extrusion duct 6 , and a second flow rate signal indicative of the second flow rate of the second material in the extrusion duct 7 .

[0079] In more detail , the control unit 14 is configured to set a first reference value of the flow rate of the first material in the extrusion duct 6 and a second reference value of the flow rate of the second material in the extrusion duct 7 . The control unit 14 is configured to control the feeding system 8 so that the first flow rate signal converges towards the first flow rate reference value and to control the feeding system 9 so that the second flow rate signal converges towards the second flow rate reference value .

[0080] In accordance with a non-limiting embodiment of the present invention, the control unit 14 is conf igured to regulate the power output of the actuators 25 and 26 so as to regulate the rotational speed of the worm screws 29 and 30 . In particular, the flow rate of the first material in extrusion duct 6 and the flow rate of the second material in extrusion duct 7 are directly proportional to the rotational speed of the respective worm screws 29 and 30 .

[0081] In accordance with a non-limiting embodiment of the present invention, the flow sensor 34 comprises a level detector 38 configured to detect a maximum level of the first material in the extrusion duct 6 , and a level detector 39 configured to detect a minimum level of the first material in the extrusion duct 6 . The flow sensor 35 comprises a level detector 40 configured to detect a maximum level of the second material in the extrusion duct 7 , and a level detector 41 configured to detect a minimum level of the second material in the extrusion duct 7 . The flow rate sensors 34 and 35 are configured to process and emit their respective flow signals according to the levels detected by the respective level detectors 38 , 39 , 40 and 41 .

[0082] Further, the extruder 3 comprises a temperature sensor 36 , which is in communication with the control unit 14 and is configured to detect a first temperature of the first material within the extrusion duct 6 , and a temperature sensor 37 , which is in communication with the control unit 14 and is configured to detect a second temperature of the second material within the extrusion duct 7 . The control unit 14 is configured to control the heating assemblies 10 and 11 according to the first and / or second temperature detected .

[0083] In particular, the temperature sensors 36 and 37 are configured to emit a first temperature signal indicative of the first temperature of the first material within the extrusion duct 6 , and a second temperature signal indicative of the second temperature of the second material within the extrusion duct 7 , respectively .

[0084] In more detail , the control unit 14 is configured to set a first reference value of the temperature of the first material within the extrusion duct 6 and a second reference value of the temperature of the second material within the extrusion duct 7 . The control unit 14 is configured to control the heating assembly 10 so that the first temperature signal converges towards the first temperature reference value and to control the heating assembly 11 so that the second temperature signal converges towards the second temperature reference value .

[0085] Speci fically, the control unit 14 is configured to control the heating assemblies 10 and 11 through respective control algorithms of the Proportional- Integral-Derivative ( PID) type .

[0086] In accordance with a non-limiting embodiment of the present invention, the control unit 14 is conf igured to independently regulate the temperature of each heating element 15 , 16 .

[0087] In particular, the temperature sensor 36 comprises a plurality of temperature detectors 42 , e . g . three temperature detectors 42 , which are distributed along the extrusion duct 6 and are configured to detect the temperature of the first material at respective sections of the extrusion duct 6 . The temperature sensor 37 comprises a plurality of temperature detectors 43 , e . g . , three temperature detectors 43 , which are distributed along the extrusion duct 7 and are configured to detect the temperature of the second material at respective sections of the extrusion duct 7 .

[0088] The temperature sensors 36 and 37 are configured to process and emit the respective temperature signals according to the temperatures detected by the respective temperature detectors 42 and 43 . In particular, the temperature detectors 42 and 43 allow a thermal profile of the first and second material to be defined along the respective extrusion ducts 6 and 7 .

[0089] Additionally or alternatively, the extruder 3 comprises a pressure sensor 44 , which is in communication with the control unit 14 and is configured to detect a first pressure of the first material within the extrusion duct 6 , and a pressure sensor 45 , which is in communication with the control unit 14 and is configured to detect a second pressure of the second material within the extrusion duct 7 . The control unit 14 is configured to control the feeding systems 8 and 9 according to the first and / or second pressure detected .

[0090] In particular, the flow rate sensors 44 and 45 are configured to respectively emit a first pressure signal indicative of the first pressure of the first material in the extrusion duct 6 , and a second pressure signal indicative of the second pressure of the second material in the extrusion duct 7 .

[0091] In more detail , the control unit 14 is configured to set a first reference value of the pressure of the first material in the extrusion duct 6 and a second reference value of the pressure o f the second material in the extrusion duct 7 . The control unit 14 is configured to control the feeding system 8 so that the first pressure signal converges towards the first pressure reference value and to control the feeding system 9 so that the second pressure signal converges towards the second pressure reference value .

[0092] In accordance with a non-limiting embodiment of the present invention, the control unit 14 is conf igured to regulate the power output of the actuators 25 and 26 so as to regulate the rotational speed of the worm screws 29 and 30 . In this way, the feeding speed of the first material and the second material can be adj usted dynamically and independently .

[0093] In accordance with an embodiment , the control unit 14 is configured to independently control the feeding systems 8 , 9 and the heating assemblies 10 , 11 respectively according to the first and / or second pressure detected and according to the first and / or second temperature detected .

[0094] With reference to Figure 4 , a variant of extruder 3 is shown, in which the extrusion duct 6 extends along the longitudinal axis Al and the extrusion duct 7 extends along the longitudinal axis A2 substantially parallel to the longitudinal axis Al . In practice , the end section 21 of the extrusion duct 6 and end section 22 of the extrusion duct 7 are essentially parallel to each other .

[0095] Further, the extruder 3 comprises a support 46 , which supports the extrusion ducts 6 and 7 in an aligned manner, extends in a direction substantially perpendicular to the longitudinal axes Al , A2 and is provided with a connector 47 at one end .

[0096] In particular, the connector 47 is configured to be coupled to an articulated arm of an anthropomorphic robot . In more detail , the extrusion duct 6 is arranged between the connector 47 and the extrusion duct 7 .

[0097] In use and with reference to Figure 3 , the control unit 14 independently controls the feeding systems 8 and 9 so as to feed the first and second material respectively into the extrusion ducts 6 and 3 via the respective inlet ducts 32 and 33 .

[0098] In particular, the flow sensors 34 and 35 detect the first flow rate o f the first material in the extrus ion duct 6 and the second flow rate of the second material in the extrusion duct 7 , respectively, and the control unit 14 controls the feeding systems 8 and 9 according to the first and / or second flow rate detected .

[0099] In addition or alternatively, the pressure sensors 44 and 45 detect the first pressure of the first material in the extrusion duct 6 and the second pressure of the second material in the extrusion duct 7 , respectively, and the control unit 14 controls the feeding systems 8 and 9 according to the first and / or second pressure detected .

[0100] At the same time , the control unit 14 independently controls the heating assemblies 10 and 11 to heat the first material in the extrusion duct 6 and the second material in the extrusion duct 7 , respectively, to determine the melting of the first and second material .

[0101] In particular, the temperature sensors 36 and 37 detect the first temperature of the first material within the extrusion duct 6 and the second temperature of the second material within the extrusion duct 7 , respectively, and the control unit 14 controls the heating assemblies 10 and 11 according to the first and / or second temperature detected .

[0102] The first and second melt material flow from the extrusion ducts 6 and 7 respectively into the mixing chamber 12 , in which the first and second materials are mixed .

[0103] At this point , mixed melt filaments of the first and second material are dispensed from the nozzle 13 to produce superimposed layers of melt material .

[0104] In particular, the superposition of the layers of melt material is carried out according to a predefined three- dimensional model stored in the control unit 14 .

[0105] Finally, it is apparent that the present invention comprises further variants of the disclosed embodiments included in the scope of protection of the appended claims .

Claims

CLAIMS1. An extruder for an additive manufacturing machine, the extruder (3) comprising:- a first extrusion duct (6) and a second extrusion duct (7) separated from each other;- a first feeding system (8) and a second feeding system (9) , which are configured to respectively feed a first material into the first extrusion duct (6) and a second material into the second extrusion duct (7) ;- a first heating assembly (10) and a second heating assembly (11) , which are configured to respectively heat the first material in the first extrusion duct (6) and the second material in the second extrusion duct (7) so as to determine the melting of the first and of the second material; a mixing chamber (12) , which is in fluidic communication with the first and the second extrusion duct (6, 7) and is configured to allow the mixing of the first and of the second melt material exiting from the first and from the second extrusion duct (6, 7) ;- a nozzle (13) , which is fluidically connected to the mixing chamber (12) and is configured to dispense mixed melt filaments of the first and of the second materials; and- a control unit (14) , which is in communication with the first and the second feeding system (8, 9) and with the first and the second heating assembly (10, 11) and is configured to independently control the first and the second feeding system (8, 9) and to independently control the first and the second heating assembly (10, 11) .

2. The extruder as claimed in Claim 1, and comprisinga first inlet duct (32) and a second inlet duct (33) configured to respectively feed the first and the second material in granular form into the first and the second extrusion duct (6, 7) .

3. The extruder as claimed in Claim 1 or 2, wherein the first heating assembly (10) comprises a plurality of first heating elements (15) arranged around the first extrusion duct (6) and the second heating assembly (11) comprises a plurality of second heating elements (16) arranged around the second extrusion duct (7) .

4. The extruder as claimed in any one of the foregoing Claims, wherein the first feeding system (8) comprises a first transport member (23) , preferably a first worm screw (29) , which is arranged within the first extrusion duct (6) and is configured to convey the first material towards the mixing chamber (12) ; the second feeding system (9) comprising a second transport member (24) , preferably a second worm screw (30) , which is arranged within the second extrusion duct (7) and is configured to convey the second material towards the mixing chamber (12) .

5. The extruder as claimed in Claim 4, wherein the first feeding system (8) comprises a first actuator (25) configured to drive the first transport member (23) , and the second feeding system (9) comprises a second actuator (26) configured to drive the second transport member (24) .

6. The extruder as claimed in Claim 5, wherein the first feeding system (8) comprises a first transmission (27) , which mechanically connects the first actuator (25) to the first transport member (23) ; the second feeding system (9)comprising a second transmission (28) , which mechanically connects the second actuator (26) to the second transport member (24 ) .

7. The extruder as claimed in any one of the foregoing Claims, and comprising a first flow rate sensor (34) , which is in communication with the control unit (14) and is configured to detect a first flow rate of the first material in the first extrusion duct (6) , and a second flow rate sensor (35) , which is in communication with the control unit (14) and is configured to detect a second flow rate of the second material in the second extrusion duct (7) ; the control unit (14) being configured to control the first and the second feeding systems (8, 9) according to the first and / or to the second flow rate detected.

8. The extruder as claimed in any one of the foregoing Claims, and comprising a first temperature sensor (36) , which is in communication with the control unit (14) and is configured to detect a first temperature of the first material within the first extrusion duct (6) , and a second temperature sensor (37) , which is in communication with the control unit (14) and is configured to detect a second temperature of the second material within the second extrusion duct (7) ; the control unit (14) being configured to control the first and the second heating assembly (10, 11) according to the first and / or to the second temperature detected .

9. The extruder as claimed in any one of the foregoing Claims, and comprising a first pressure sensor (44) , which is in communication with the control unit (14) and isconfigured to detect a first pressure of the first material within the first extrusion duct (6) , and a second pressure sensor (45) , which is in communication with the control unit (14) and is configured to detect a second pressure of the second material within the second extrusion duct (7) ; the control unit (14) being configured to control the first and the second feeding system (8, 9) according to the first and / or the second pressure detected.

10. The extruder as claimed in any one of the foregoing Claims, wherein the first extrusion duct (6) comprises a first end section (21) , which flows into the mixing chamber (12) and the second extrusion duct (7) comprises a second end section (22) , which flows into the mixing chamber (12) ; the first and second end sections (21, 22) being mutually inclined at a V angle or being substantially parallel.

11. The extruder as claimed in any one of the foregoing Claims, wherein the first and the second materials have different physical and / or chemical characteristics.

12. An additive manufacturing machine comprising the extruder (3) as claimed in any one of the foregoing Claims.

13. A method of additive manufacturing comprising the steps of:- feeding a first material into a first extrusion duct (6) through a first feeding system (8) ;- feeding a second material into a second extrusion duct (7) separated from the first extrusion duct (6) through a second feeding system (9) ;- independently controlling the first and the second feeding system (8, 9) ;- heating the first material in the first extrusion duct (6) through a first heating assembly (10) so as to determine the melting of the first material;- heating the second material in the second extrusion duct (7) through a second heating assembly (11) so as to determine the melting of the second material;- independently controlling the first and the second heating assembly (10, 11) ;- mixing the first and the second melt material exiting from the first and from the second extrusion duct (6, 7) respectively; and- dispensing mixed melt filaments of the first and of the second material from a nozzle (13) .

14. The method as claimed in Claim 13, and comprising the steps of feeding the first material in granular form into the first extrusion duct (6) ; and feeding the second material in granular form into the second extrusion duct (7) .

15. The method as claimed in Claim 13 or 14, and comprising the steps of detecting a first flow rate of the first material in the first extrusion duct (6) ; detecting a second flow rate of the second material in the second extrusion duct (7) ; and controlling the first and the second feeding system (8, 9) according to the first and / or the second flow rates detected.

16. The method as claimed in any one of Claims 13 to 15, and comprising the steps of detecting a first temperature of the first material within the first extrusion duct (6) ; detecting a second temperature of the second material withinthe second extrusion duct (7) ; and controlling the first and the second heating assembly (10, 11) according to the first and / or the second detected temperatures.

17. The method as claimed in any one of Claims 13 to 16, and comprising the steps of detecting a first pressure of the first material within the first extrusion duct (6) ; detecting a second pressure of the second material within the second extrusion duct (7) ; and controlling the first and the second feeding system (8, 9) according to the first and / or the second detected pressures.

Images