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

Abstract

An extruder for an additive manufacturing machine has an extrusion duct (6) extending along a longitudinal axis (A1); a first feeding system (7) configured to feed a first flow rate of a first material along the extrusion duct (6); a heating assembly (8) configured to heat the first material in the extrusion duct (6) to a defined temperature so as to determine a change in the rheological properties of the first material; at least one second feeding system (9; 38) configured to feed a second flow rate of an additive component, preferably into the extrusion duct (6); a mixing chamber (10), which is at least partially recessed in the extrusion duct (6) and is configured to allow a mixing between the first material and the additive component so as to make a second material; a nozzle (11), which is arranged at one end of the extrusion duct (6) and is configured to dispense the second material; and a control unit (12) configured to control in a coordinated manner the first feeding system (7), the second feeding system (9; 38) and the heating assembly (8).

Description

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

[0002] Cross-Reference to Related Applications

[0003] This Patent Application claims priority from Italian Patent Application No.

[0004] 102025000000306 filed on January 10, 2025, the entire disclosure of which is incorporated herein by reference.

[0005] Field of the Art

[0006] The present invention relates to an additive manufacturing machine and to an extruder for said additive manufacturing machine.

[0007] Furthermore, the present invention relates to an additive manufacturing method.

[0008] Background of the Invention

[0009] In the field of additive manufacturing, in order to produce objects or semi-finished products having a desired shape and structure, it is commonly known to employ additive manufacturing machines provided with an extruder configured to modify the rheology of a feed material and to deposit filaments of said molten material in layers on a worktable, according to a predefined three-dimensional digital model. Once dispensed from the nozzle, each layer of molten material solidifies and bonds to an adjacent layer of material. The succession of superimposed layers thus forms a single solid structure or final object having the desired shape.

[0010] By way of example, known additive manufacturing machines in the "Material Extrusion (MEX)" category according to ISO / ASTM 52900 may employ the so-called "Fused Filament Fabrication (FFF)" technique, in which a thermoplastic filament wound on a spool supplies the feed material to the extruder, or may employ the so-called "FusedGranular Fabrication (FGF)" technique, in which the feed material is supplied to the extruder in granular form.

[0011] However, when it is necessary to produce final objects made of a material having variable chemical-physical properties such as objects made of polymeric foam with variable internal porosity currently known additive manufacturing machines prove to be inefficient, because the extruders of such additive manufacturing machines are designed to extrude a specific material having predetermined chemical-physical properties.

[0012] Summary of the Invention

[0013] A purpose of the present invention is to provide an extruder for an additive manufacturing machine that mitigates the drawbacks of the prior art highlighted above. In accordance with the present invention, an extruder for an additive manufacturing machine is provided, the extruder comprising:

[0014] - an extrusion duct extending along a longitudinal axis;

[0015] - a first feeding system configured to feed a first flow rate of a first material along the extrusion duct;

[0016] - a heating assembly configured to heat the first material in the extrusion duct to a defined temperature so as to cause a change in the rheological properties of the first material;

[0017] - at least one second feeding system configured to feed a second flow rate of an additive component, preferably into the extrusion duct;

[0018] - a mixing chamber, which is at least partially recessed in the extrusion duct and is configured to allow a mixing between the first material and the additive component so as to obtain a second material;

[0019] - a nozzle, which is arranged at one end of the extrusion duct and is configured to dispense the second material; and- a control unit configured to control in a coordinated manner the first feeding system, the second feeding system, and the heating assembly.

[0020] Thanks to the present invention, during the extrusion process it is possible to precisely and in real time control the chemical-physical characteristics such as porosity, density, and mechanical or optical properties of the second material dispensed from the nozzle. In other words, the extruder makes it possible to produce final objects having highly customized chemical-physical structures in a simple and cost-effective manner.

[0021] Such versatility makes it possible to combine the physical expansion of the material with the addition of blowing agents or additives capable of modifying the properties of the first material in real time.

[0022] In practice, the second feeding system allows additive components to be injected directly into the extruder, for example through a mixing chamber, thereby enabling the production of lightweight structures or materials having density gradients, such as polymeric foams with variable internal porosity or composite materials. In particular, the extruder allows structures with gradient porosity to be created, i.e., with locally controlled porosity along the volume of the final object.

[0023] Furthermore, the extruder made in accordance with the present invention can be used both in additive manufacturing machines employing "Fused Filament Fabrication (FFF)" techniques and in additive manufacturing machines employing "Fused Granular Fabrication (FGF)" techniques.

[0024] A further purpose of the present invention is to provide an additive manufacturing machine that mitigates the drawbacks of the prior art highlighted above. In accordance with the present invention, an additive manufacturing machine is provided comprising the extruder as described above.

[0025] A further purpose of the present invention is to provide an additive manufacturing method that mitigates the drawbacks of the prior art highlighted above.In accordance with the present invention, an additive manufacturing method is provided, comprising the steps of:

[0026] - feeding a first flow rate of a first material along an extrusion duct of an extruder by means of a first feeding system;

[0027] - heating the first material in the extrusion duct to a defined temperature by means of a heating assembly so as to cause a change in the rheological properties of the first material;

[0028] - feeding a second flow rate of an additive component into the extrusion duct by means of a second feeding system;

[0029] - mixing the first material and the additive component so as to obtain a second material; - dispensing the second material from a nozzle arranged at one end of the extrusion duct; and

[0030] - controlling in a coordinated manner the first feeding system, the second feeding system, and the heating assembly.

[0031] Thanks to the present method, final objects can be produced in a simple and rapid manner while precisely controlling the chemical-physical characteristics of the material forming the produced final objects.

[0032] In particular, the present invention can be used to modify known extruders and / or known additive manufacturing machines in order to improve their ductility in terms of the chemical-physical characteristics of the final objects produced.

[0033] Brief Description of the Drawings

[0034] Further features and advantages of the present invention will become apparent from the following description of non-limiting embodiments thereof, with reference to the Figures of the accompanying drawings, in which:

[0035] - Figure 1 is a perspective view, with parts removed for clarity and parts shownschematically, of an additive manufacturing machine made in accordance with the present invention;

[0036] - Figure 2 is a sectional view, with parts removed for clarity and parts shown schematically, of an extruder of the additive manufacturing machine of Figure 1;

[0037] - Figure 3 is a sectional view, with parts removed for clarity and parts shown schematically, of a variant of the extruder of Figure 2;

[0038] - Figure 4 is a flow diagram of a method for controlling the extruder of Figure 2;

[0039] - Figures 5-8 are sectional views, with parts removed for clarity and parts shown schematically, of respective details of the extruder of Figure 2 made in accordance with further respective embodiments of the present invention; and

[0040] - Figure 9 is a sectional view, with parts removed for clarity and parts shown schematically, of the extruder of Figure 2 during a step of producing an object by means of an additive manufacturing method in accordance with the present invention.

[0041] Description of the Invention

[0042] With reference to Figure 1, the numeral 1 indicates, as a whole, an additive manufacturing machine used to produce objects based on a three-dimensional digital model of the object to be made.

[0043] In particular, the additive manufacturing machine 1 is configured to employ an additive manufacturing technique of the Fused Granular Fabrication (FGF) type and / or an additive manufacturing technique of the Fused Filament Fabrication (FFF) type.

[0044] In greater detail, the additive manufacturing machine 1 is configured to produce objects made of an expanded polymeric material such as an expanded polymeric foam and / or of a metallic material and / or of a ceramic material and / or of a composite polymeric material and / or a fiber-reinforced material.In the embodiment described and illustrated herein, which does not limit the scope of the present invention, the additive manufacturing machine 1 comprises a frame 2, a worktable 3 supported by the frame 2, an extruder 4 configured to deposit filaments of material in layers on the worktable 3, and a handling system 5 configured to move the extruder 4 at a working speed relative to the worktable 3. In particular, the handling system 5 is configured to move the extruder 4 along three mutually orthogonal axes X, Y, Z of a Cartesian reference system XYZ.

[0045] Furthermore, the additive manufacturing machine 1 may comprise an articulated arm, not shown in the accompanying Figures, which is carried by the handling system 5 and in turn carries the extruder 4 in a movable manner. In particular, said articulated arm is configured to move the extruder 4 along additional axes and / or to rotate the extruder 4 about additional axes.

[0046] According to an alternative embodiment, not shown in the accompanying Figures, the additive manufacturing machine 1 comprises an anthropomorphic robot, which carries the extruder 4 and controls the position and orientation of the extruder 4 relative to a worktable.

[0047] With reference to Figure 2, the extruder 4 comprises an extrusion duct 6 extending along a longitudinal axis Al; a feeding system 7 configured to feed a first flow rate of a first material along the extrusion duct 6; a heating assembly 8 configured to heat the first material in the extrusion duct 6 to a defined temperature so as to cause a change in the rheological properties of the first material; a feeding system 9 configured to feed a second flow rate of an additive component into the extrusion duct 6; a mixing chamber 10, which is at least partially recessed within the extrusion duct 6 and is configured to allow a mixing between the first material and the additive component so as to obtain a second material; a nozzle 11, which is arranged at one end of the extrusion duct 6 and is configured to dispense the second material; and a control unit 12, which isin communication with the feeding system 7, the feeding system 9, and the heating assembly 8, and is configured to control in a coordinated manner the feeding system 7, the feeding system 9, and the heating assembly 8.

[0048] In accordance with one embodiment, the control unit 12 is configured to control in a coordinated manner the first feeding system 7, the second feeding system 9, and the handling system 5 (Figure 1) so as to adjust the working speed of the extruder 4 as a function of the flow rate of the first material and of the additive component.

[0049] In this way, it is possible to ensure a constant dispensing speed of the second material and, consequently, to maintain a uniform volume of the dispensed second material so as to avoid defects caused by variations in the dispensing speed.

[0050] In particular, the control unit 12 is configured to define a working trajectory for the extruder 4; calculate the volume of the second material required for the defined working trajectory; and control the handling system 5 (Figure 1) to dynamically adjust and / or adapt the working speed of the extruder 4 so as to keep constant the volume of the second material dispensed along the working trajectory.

[0051] In particular, the first material and the additive component exhibit different physical and / or chemical characteristics. By way of example, the first material is polymeric, ceramic, or metallic, and the additive component is in liquid or gaseous or granular form, or is a microfiller or a nanofiller.

[0052] It is understood that the extruder made in accordance with the present invention may employ a first material and an additive component having chemical-physical characteristics different from those indicated above merely by way of example.

[0053] As used herein, the term chemical-physical characteristics refers, for example, to the chemical composition of the material, the chemical phase of the material, the density of the material, the mechanical properties of the material, the porosity of the material, thelight refraction properties of the material, or the electrical / magnetic properties or chromatic properties of the material.

[0054] In particular, the heating assembly 8 comprises a plurality of heating elements 13 arranged around the extrusion duct 6.

[0055] In the embodiment described and illustrated herein, each heating element 13 is annular in shape and is fitted around the extrusion duct 6. In particular, each heating element 13 comprises a respective electrical resistance.

[0056] In particular, the mixing chamber 10 is at least partially recessed within the nozzle 11 and comprises a static mixer 14 arranged inside the nozzle 11.

[0057] According to variants of the present invention not shown in the accompanying Figures, the mixing chamber comprises both a static mixer and a dynamic mixer, or only a dynamic mixer, or only a static mixer, or is devoid of any mixer.

[0058] In the embodiment described and illustrated herein, which does not limit the scope of the present invention, the mixing chamber 10 is recessed partially within the nozzle 11 and partially within the extrusion duct 6.

[0059] It is understood that, according to variants of the present invention not shown in the accompanying Figures, the mixing chamber 10 may be recessed entirely within the nozzle 11, or alternatively entirely within the extrusion duct 6.

[0060] In particular, the extrusion duct 6 has a substantially tubular shape and comprises a heating portion 15, on which the heating assembly 8 is arranged, and a mixing portion 16, in which the mixing chamber 10 is partially recessed.

[0061] In the embodiment described and illustrated herein, which does not limit the scope of the present invention, the extrusion duct 6 comprises a lateral opening 17 connected to the feeding system 9 so as to allow the additive component to enter the mixing chamber 10. In particular, the lateral opening 17 is arranged upstream of the mixing chamber 10, namely between the heating portion 15 and the mixing portion 16.In greater detail, the feeding system 7 comprises a conveying element 18, preferably a worm screw, arranged inside the extrusion duct 6 and configured to convey the first material toward the nozzle 11.

[0062] In particular, the conveying element 18 comprises a mixing portion 19, which is arranged in the mixing chamber 10 and is configured to mix the first material and the additive component, and a conveying portion 20, which is arranged in the heating portion 15 of the extrusion duct 6, upstream of the mixing portion 19, and is configured to convey the first material toward the mixing chamber 10.

[0063] Furthermore, the feeding system 7 comprises an actuator 21, such as an electric motor, which is controlled by the control unit 12 and is configured to actuate the conveying element 18.

[0064] According to one embodiment, the extruder 4 comprises an inlet duct, not shown in the accompanying Figures, configured to feed the first material in granular form into the extrusion duct 6.

[0065] In particular, the feeding system 9 comprises a tank 22 configured to contain the additive component; a feeding duct 23, which connects the tank 22 to the extrusion duct 6; and a conveying device 24, which is in communication with the control unit 12 and is configured to control the feeding of the additive component from the tank 22 to the extrusion duct 6. According to one embodiment, the conveying device 24 is configured to control the physical and fluid-dynamic properties of the additive component, such as, for example, the pressure, the temperature, and the flow rate of the additive component.

[0066] In greater detail, the feeding duct 23 is connected to the lateral opening 17 of the extrusion duct 6 so as to allow the additive component to pass into the extrusion duct 6.According to one embodiment, the tank 22 is configured to contain the additive component in gaseous form. In accordance with this configuration, the conveying device 24 comprises a pneumatic machine, such as a compressor or a blower, or a device for controlling the flow of the additive component, such as a flow meter or a pressure regulator.

[0067] According to a further embodiment, the tank 22 is configured to contain the additive component in liquid form. In accordance with this configuration, the conveying device 24 comprises a hydraulic machine, such as a pump, or a device for controlling the flow of the additive component, such as a flow meter.

[0068] According to a further embodiment, the tank 22 is configured to contain the additive component in solid form, preferably in granules or powder. In accordance with this configuration, the conveying device 24 comprises a mechanical conveyor, such as a worm screw or a conveyor belt or a piston.

[0069] According to a variant of the present invention, shown in Figure 3, the extruder 4 comprises a plurality of feeding systems 38 arranged in parallel with each other. In this way, it is possible to feed simultaneously into the extrusion duct 6 an additive component in gaseous form, an additive component in liquid form, and an additive component in solid form.

[0070] In particular, each feeding system 38 is provided with a respective conveying device 39, which is in communication with the control unit 12 and comprises an extruder 40 analogous to the extruder 4 of Figure 2.

[0071] According to one non-limiting embodiment of the present invention, the feeding systems 38 are configured to feed into the extrusion duct 6 additive components having RGB colors.

[0072] With reference to Figure 2, the nozzle 11 has a dispensing opening 25 with variable diameter.In accordance with the present invention, the control unit 12 comprises a memory 26 configured to store a digital model of an object to be produced by additive manufacturing. The control unit 12 is configured to control the feeding system 7, the feeding system 9, and the heating assembly 8 based on said stored digital model.

[0073] In particular, said stored digital model may be created using a CAD (Computer-Aided Design) program or a CAM slicing program, and comprises a plurality of chemicalphysical parameters indicative of the chemical-physical characteristics of each portion of the object to be produced. For example, such chemical-physical parameters may indicate a porosity or a density gradient or a color gradient of the object to be produced.

[0074] In accordance with one form of implementation, the control unit 12 is configured to process or modify said digital model according to the desired chemical-physical characteristics of the object to be produced using optimization algorithms, such as a "topology optimization" algorithm.

[0075] Furthermore, the control unit 12 is configured to process G-code commands or another machine language for the extruder 4 based on said stored digital model. In greater detail, said processed G-code commands are indicative of the position and / or the working speed of the extruder 4 relative to the worktable 3 (Figure 1) and / or of the chemical-physical characteristics of the object to be produced, and are used to control the feeding system 7, the feeding system 9, and the heating assembly 8.

[0076] According to one embodiment, the memory 26 of the control unit 12 is configured to store a predictive algorithm, which associates with each change in the chemical and / or physical characteristics of the second material a respective change in the first flow rate of the first material, a respective change in the second flow rate of the additive component, and a respective change in the temperature of the first material in the extrusion duct 6. The control unit 12 is configured to control the feeding system 7,the feeding system 9, and the heating assembly 8 as a function of said predictive algorithm.

[0077] In particular, the extruder 4 comprises a flow rate sensor 27, which is in communication with the control unit 12 and is configured to detect the first flow rate of the first material in the extrusion duct 6; a flow rate sensor 28, which is in communication with the control unit 12 and is configured to detect the second flow rate of the additive component; and a temperature sensor 29, which is in communication with the control unit 12 and is configured to detect the temperature of the first material in the extrusion duct 6.

[0078] Furthermore, the extruder 4 comprises a quality detector 30, which is in communication with the control unit 12 and is configured to detect chemical-physical parameters indicative of the chemical and / or physical characteristics of the second material dispensed from the nozzle 11. By way of example, the quality detector 30 may comprise an ultrasonic sensor and / or a lidar sensor and / or a laser sensor and / or a profilometer and / or a camera and / or a thermal camera and / or a color sensor and / or an infrared sensor. The control unit 12 is configured to control the feeding system 7, the feeding system 9, and the heating assembly 8 as a function of said detected chemicalphysical parameters.

[0079] With reference to Figure 4, the control unit 12 is configured to: - calculate a first reference flow rate of the first material (block 34), a second reference flow rate of the additive component (block 35), and a reference temperature of the first material in the extrusion duct 6 (block 36) in order to reproduce the chemical and / or physical characteristics of each portion of the object to be produced as a function of the chemical-physical parameters of said stored digital model;

[0080] - control the feeding system 7 (block 37) so that the first flow rate of the first material converges toward said first reference flow rate;- control the feeding system 9 (block 38) so that the second flow rate of the additive component converges toward said second reference flow rate; and

[0081] - control the heating assembly 8 (block 39) so that the temperature of the first material in the extrusion duct 6 converges toward said reference temperature.

[0082] According to a non-limiting embodiment of the present invention, the control unit 12 is configured to control in a closed loop the feeding system 7, the feeding system 9, and the heating assembly 8 so that the detected first flow rate of the first material, the detected second flow rate of the additive component, and the detected temperature of the first material respectively converge toward the first reference flow rate of the first material, the second reference flow rate of the additive component, and the reference temperature of the first material.

[0083] In particular, the control unit 12 is configured to control the feeding system 7, the feeding system 9, and the heating assembly 8 by means of respective Proportional-Integral-Derivative (PID) control algorithms.

[0084] In greater detail, the control unit 12 is configured to regulate the power supplied to the actuator 21 so as to control the conveying element 18 and, consequently, the first flow rate of the first material. Furthermore, the control unit 12 is configured to control the conveying device 24 so as to regulate the second flow rate of the additive component in the feeding duct 23.

[0085] According to a variant of the present invention not shown in the accompanying Figures, the extruder 4 comprises an additional temperature sensor configured to detect a temperature of the additive component prior to the entry of said additive component into the extrusion duct 6, and an additional heating assembly configured to heat the additive component so as to vary the rheological properties of the additive component.In accordance with this variant, the control unit 12 is also configured to control said additional heating assembly as a function of the temperature of the additive component detected by the additional temperature sensor.

[0086] With reference to Figure 5, the extruder 4 is shown in accordance with a further embodiment, in which the feeding duct 23 is at least partially recessed within the conveying element 18 and extends along the longitudinal axis Al. In particular, the feeding duct 23 comprises a channel 31, which is formed within the conveying element 18 and flows into the mixing chamber 10.

[0087] In greater detail, in addition to enabling the feeding of the additive component into the mixing chamber 10, the channel 31 is also configured to allow the extraction of fluids from the extrusion duct 6. In this way, it is possible to control the humidity level inside the extrusion duct 6.

[0088] With reference to Figure 6, the extruder 4 is shown according to a further embodiment, in which the additive component is in gaseous or liquid form. In accordance with this configuration, the extruder 4 comprises a permeable membrane 32, which is arranged in the extrusion duct 6, comprises a porous wall 33, and is configured to allow the passage of gases and / or liquids through the porous wall 33 while blocking the passage of the first material through the porous wall 33. In this way, the first material can be contained within the porous wall 33 while simultaneously feeding the additive component in gaseous or liquid form inside the porous wall 33, thereby allowing the mixing of the first material and the additive component within the porous wall 33.

[0089] With reference to Figure 7, the extruder 4 is shown according to a further embodiment, in which the extruder 4 comprises a blocking device 37, which is arranged at the lateral opening 17 and is configured to prevent an outflow of the first material or the second material from the extrusion duct 6. In particular, the blocking device 37 may be a valve, preferably of the non-return type, or a porous membrane, or a filter.According to a variant of the present embodiment, the blocking device 37 is constituted by a portion of the conveying element 18 arranged at the lateral opening 17 and shaped so as to reduce the pressure of the first material at the lateral opening 17.

[0090] With reference to Figure 8, the extruder 4 is shown according to a further embodiment in which the extrusion duct comprises a restriction 41. In particular, the restriction 41 is interposed between the heating portion 15 of the extrusion duct and the mixing chamber 10. In this way, thanks to the restriction 41, it is possible to increase the amount of heat transferred to the first material and, at the same time, to reduce the pressure of the first material and of the additive component in the mixing chamber 10, thereby preventing a backflow of the first material and / or of the additive component from the mixing chamber 10 toward the heating portion 15.

[0091] In use, and with reference to Figure 4, the control unit 12 stores the digital model of the object to be produced (block 40) and calculates a first reference flow rate of the first material (block 34), a second reference flow rate of the additive component (block 35), and a reference temperature of the first material in the extrusion duct 6 (block 36) in order to reproduce the chemical and / or physical characteristics of each portion of the object to be produced as a function of the chemical-physical parameters of said stored digital model. In greater detail, the control unit 12 processes control commands in G-code or in another machine language as a function of said stored digital model.

[0092] At this point, the control unit 12 controls the feeding system 7 (block 37) so as to feed the first material along the extrusion duct 6.

[0093] Simultaneously and in a coordinated manner, the control unit 12 controls the heating assembly 8 (block 39) so as to heat the first material in the extrusion duct 6, thereby causing a change in the rheological properties of the first material, and controls the feeding system 9 (block 38) so as to feed the additive component into the extrusion duct 6.In particular, the flow rate sensor 27 detects the first flow rate of the first material in the extrusion duct 6 (block 41). The control unit 12 compares said detected first flow rate with the first reference flow rate (block 42) and controls the feeding system 7 (block 37) so that the first flow rate of the first material converges toward said first reference flow rate.

[0094] At the same time, the flow rate sensor 28 detects the second flow rate of the additive component entering the extrusion duct 6 (block 43). The control unit 12 compares said detected second flow rate with the second reference flow rate (block 44) and controls the feeding system 9 (block 38) so that the second flow rate of the additive component converges toward said second reference flow rate.

[0095] Furthermore, the temperature sensor 29 detects the temperature of the first material in the extrusion duct 6 (block 45). The control unit 12 compares said detected temperature with the reference temperature (block 46) and controls the heating assembly 8 (block 39) so that the temperature of the first material converges toward said reference temperature.

[0096] Once inside the mixing chamber 10, the first material and the additive component are mixed— for example by means of the mixing portion 19 of the conveying element 18, or by means of the static mixer 14— so as to obtain the second material, which is subsequently dispensed from the nozzle 11.

[0097] With reference to Figure 9, an example of a printed object 34 directly obtainable by means of the additive manufacturing method implemented through the extruder 4 is shown.

[0098] The printed object 34 comprises an inner layer 35 made of gradient foam, and a plurality of layers 36 of different materials arranged above and below the inner layer 35.

[0099] In particular, the additive manufacturing method described and illustrated herein makes it possible to produce a wide range of different manufactured products. By wayof example, it is possible to produce protective helmets, shin guards, shoe insoles, components for customized packaging, sound-absorbing panels, interior decorative elements, medical prostheses, scaffolds for tissue engineering, personal protective equipment such as knee pads or elbow pads, supports for electronic devices, thermal and acoustic insulation panels, floating elements for marine applications, lightweight structural parts for the automotive and aerospace sectors, customized ergonomic seats, sports equipment such as rackets or grips, impact-absorbing materials, designer furniture, urban furnishing elements, devices for fluid flow control, as well as functional accessories such as protective cases for instruments or sensitive equipment, purification filters with controlled porosity and fillers, and lightweight molds for composite materials.

Claims

CLAIMS1. An extruder for an additive manufacturing machine, the extruder (4) comprising:an extrusion duct (6) extending along a longitudinal axis (Al);a first feeding system (7) configured to feed a first flow rate of a first material along the extrusion duct (6);a heating assembly (8) configured to heat the first material in the extrusion duct (6) to a defined temperature so as to determine a change in the rheological properties of the first material;at least one second feeding system (9; 38) configured to feed a second flow rate of an additive component, preferably into the extrusion duct (6);a mixing chamber (10), which is at least partially recessed in the extrusion duct (6) and is configured to allow a mixing between the first material and the additive component so as to make a second material;a nozzle (11), which is arranged at one end of the extrusion duct (6) and is configured to dispense the second material; anda control unit (12) configured to control in a coordinated manner the first feeding system (7), the second feeding system (9; 38) and the heating assembly (8).

2. The extruder as claimed in claim 1, wherein the heating assembly (8) comprises a plurality of heating elements (13) arranged around the extrusion duct (6).

3. The extruder as claimed in claim 1 or 2, wherein the mixing chamber (10) is at least partially recessed in the nozzle (11) and comprises a static mixer (14), preferably arranged within the nozzle (11).

4. The extruder as claimed in any one of the foregoing claims, wherein the first feeding system (7) comprises a conveying element (18), preferably a worm screw, which is arranged within the extrusion duct (6) and is configured to convey the firstmaterial towards the nozzle (11); preferably the conveying element (18) comprising a mixing portion (19), which is arranged in the mixing chamber (10) and is configured to mix the first material and the additive component; preferably the first feeding system (7) comprising an actuator (21) configured to actuate the conveying element (18).

5. The extruder as claimed in claim 4, wherein the second feeding system (9; 38) comprises a tank (22) configured to contain the additive component, preferably in gaseous form; a feeding duct (23), which connects the tank(22) to the extrusion duct (6), is preferably at least partially recessed within the conveying element (18), and preferably extends along the longitudinal axis (Al); and a conveying device (24; 39) configured to control the feeding of the additive component from the tank (22) to the extrusion duct (6).

6. The extruder as claimed in any one of the foregoing claims, wherein the nozzle (11) has a variable diameter dispensing opening (25).

7. The extruder as claimed in any one of the foregoing claims, wherein the control unit (12) comprises a memory (26) configured to store a digital model of an object to be made by additive manufacturing; the control unit (12) being configured to control the first feeding system (7), the second feeding system (9; 38) and the heating assembly (8) as a function of said stored digital model; preferably the stored digital model comprising a plurality of chemical / physical parameters indicative of chemical and / or physical characteristics of each portion of the object to be made.

8. The extruder as claimed in claim 7, wherein the control unit (12) is configured to:calculate a first reference flow rate of the first material, a second reference flow rate of the additive component, and a reference temperature of the first material in the extrusion duct (6) to reproduce the chemical and / or physical characteristics of each portion of the object to be made as a function of thechem ica l / physical parameters of said stored digital model;control the first feeding system (7) so that the first flow rate of the first material converges toward said first reference flow rate;control the second feeding system (9; 38) so that the second flow rate of the additive component converges toward said second reference flow rate; and control the heating assembly (8) so that the temperature of the first material in the extrusion duct (6) converges toward said reference temperature.

9. The extruder as claimed in claim 8, and comprising a first flow rate sensor (27), which is in communication with the control unit (12) and is configured to detect the first flow rate of the first material; a second flow rate sensor (28), which is in communication with the control unit (12) and is configured to detect the second flow rate of the additive component; a temperature sensor (29), which is in communication with the control unit (12) and is configured to detect the temperature of the first material in the extrusion duct (6); the control unit (12) being configured to control in a closed-loop the first feeding system (7), the second feeding system (9; 38) and the heating assembly (8) so that said detected first flow rate, said detected second flow rate and said detected temperature converge towards the first reference flow rate, towards the second reference flow rate and towards the reference temperature of the first material, respectively.

10. The extruder as claimed in any one of claims 7 to 9, wherein the memory (26) of the control unit (12) is configured to store a predictive algorithm, which associates to each change in the chemical and / or physical characteristics of the second material a respective change in the first flow rate of the first material, in the second flow rate of the additive component, and in the temperature of the first material in the extrusion duct (6); the control unit (12) being configured to control the first feeding system (7), thesecond feeding system (9; 38) and the heating assembly (8) as a function of said predictive algorithm.

11. The extruder as claimed in any one of the foregoing claims, and comprising a quality detector (30), which is in communication with the control unit (12) and is configured to detect chemical / physical parameters indicative of chemical and / or physical characteristics of the second material dispensed from the nozzle (11); the control unit (12) being configured to control the first feeding system (7), the second feeding system (9; 38) and the heating assembly (8) as a function of said detected chemical / physical parameters.

12. An additive manufacturing machine comprising the extruder (4) as claimed in any one of the foregoing claims.

13. The additive manufacturing machine as claimed in claim 12, and comprising a frame (2), a worktable (3) supported by the frame (2), and a handling system (5) configured to move the extruder (4) at a working speed with respect to the worktable (3); the control unit (12) being configured to control in a coordinated manner the first feeding system (7), the second feeding system (9; 38) and the handling system (5) so as to adjust the working speed of the extruder (4) as a function of the flow rate of the first material and of the additive component.

14. The additive manufacturing machine as claimed in claim 13, wherein the control unit (12) is configured to:define a working trajectory for the extruder (4);calculate the volume of the second material required for the defined working trajectory; andcontrol the handling system (5) to dynamically adjust and / or adapt the working speed of the extruder (4) so as to keep constant the volume of the second material dispensed along the working trajectory.

15. An additive manufacturing method comprising the steps of: feeding a first flow rate of a first material alongan extrusion duct (6) of an extruder (4) by means of a first feeding system (7);heating the first material in the extrusion duct (6) to a defined temperature by means of a heating assembly (8) so as to determine a change in the rheological properties of the first material;feeding a second flow rate of an additive component into the extrusion duct (6) by means of a second feeding system (9; 38);mixing the first material and the additive component to make a second material;dispensing the second material from a nozzle (11) arranged at one end of the extrusion duct (6); andcontrol in a coordinated manner the first feeding system (7), the second feeding system (9; 38) and the heating assembly (8).

16. The additive manufacturing method as claimed in claim 15, and comprising the steps of storing a digital model of an object to be made by additive manufacturing, wherein said stored digital model comprises a plurality of chemical / physical parameters indicative of chemical and / or physical characteristics of each portion of the object to be made; and controlling the first feeding system (7), the second feeding system (9; 38) and the heating assembly (8) as a function of said stored digital model.

17. The additive manufacturing method as claimed in claim 16, and comprising the steps of:calculating a first reference flow rate of the first material, a second reference flow rate of the additive component, and a reference temperature of the first material in the extrusion duct (6) to reproduce chemical and / or physical characteristicsof each portion of the object to be made as a function of the chemical / physical parameters of said stored digital model;controlling the first feeding system (7) so that the first flow rate of the first material converges toward said first reference flow rate;controlling the second feeding system (9; 38) so that the second flow rate of the additive component converges toward said second reference flow rate;controlling the heating assembly (8) so that the temperature of the first material in the extrusion duct (6) converges towards said reference temperature;preferably storing a predictive algorithm, which associates to each change in the chemical and / or physical characteristics of the second material a respective change in the first reference flow rate of the first material, in the second reference flow rate of the additive component and in the reference temperature of the first material in the extrusion duct (6); andpreferably controlling the first feeding system (7), the second feeding system (9; 38) and the heating assembly (8) as a function of said predictive algorithm.

18. The additive manufacturing method as claimed in claim 17, and comprising the steps of:detecting the first flow rate of the first material;detecting the second flow rate of the additive component; detecting the temperature of the first material in the extrusion duct (6); andcontrolling in a closed-loop the first feeding system (7), the second feeding system (9; 38), and the heating assembly (8) such that said detected first flow rate, said detected second flow rate, and said detected temperature of the first material converge toward the first reference flow rate, the second reference flow rate, and the reference temperature of the first material, respectively.

19. The additive manufacturing method as claimed in any one of claims 15 to 18, and comprising the steps of detecting chemical / physical parameters indicative of chemical and / or physical characteristics of the second material dispensed from the nozzle (11); and controlling the first feeding system (7), the second feeding system (9; 38) and the heating assembly (8) as a function of said detected chemical / physical parameters.

20. A computer program configured to control an extruder and directly loadable into a memory of a computer to carry out the method steps of any one of claims 15 to 19 when the program is implemented by the computer.

21. A program product comprising a readable medium on which the program of claim 20 is stored.

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