Additive manufacturing process for three-dimensional objects

Abstract

A method (10) for additively manufacturing at least one three-dimensional object using at least one additive manufacturing device by filament extrusion, the method comprising a step (12) of controlling said additive manufacturing device for the fabrication of said object. During said control step (12): - printing speed and temperature commands for the extruder of said additive manufacturing device are generated during a slicing step (13) based on a map (C(T°, V)) of the printing speed dependent on the filament temperature and the evolution of the extruder temperature over time (t), said map (C(T°, V)) being specific to the extruded filament material; and - said printing speed and extruder temperature commands are transmitted to the additive manufacturing device during a transmission step (14). Figure for the abstract: Fig 1

Description

Title of the invention: Additive manufacturing process for three-dimensional objects

[0001] The present invention relates to the field of additive manufacturing.

[0002] More particularly, the invention relates to additive manufacturing by extrusion of a molten material, called "fused deposition modeling", acronym FDM in Anglo-Saxon terms.

[0003] It is known to use an extruder to produce a rod or wire of molten material from filaments of thermoplastic or composite material.

[0004] The printing parameters of an object manufactured using an additive manufacturing process are generally determined experimentally based on the material chosen and the additive manufacturing device or printer used. These parameters depend on the mechanical characteristics of the additive manufacturing device as well as the characteristics of the extruder. Objects with complex shapes may require several sets of parameters during their manufacture.

[0005] However, due to the extruder architecture, changes in printing speed are generally faster than changes in filament extrusion temperature. Therefore, a temperature change requires temporarily halting the manufacturing process until the extruder nozzle temperature reaches the new setpoint. Such a temporary stoppage in object manufacturing increases the object's manufacturing time and can lead to defects in the object's construction.

[0006] Thus, there is a need to improve the additive manufacturing processes of a three-dimensional object.

[0007] The objective of the invention is to optimize the manufacturing time of a three-dimensional object while maintaining a satisfactory level of manufacturing quality.

[0008] The present invention relates to a method for the additive manufacturing of at least one three-dimensional object using at least one additive manufacturing device by filament extrusion or "fused deposition modeling", acronym FDM in Anglo-Saxon terms,

[0009] The process includes a step of controlling said additive manufacturing device for the manufacture of said object.

[0010] During said control step, during a slicing step, printing speed and temperature commands for the extruder of said additive manufacturing device are generated based on a printing speed map dependent on filament temperature, and based on the evolution of The extruder temperature as a function of time. This mapping is specific to the material of the extruded filament.

[0011] Said printing speed and extruder temperature instructions are then transmitted, during a transmission step, to the additive manufacturing device.

[0012] This mapping allows for pre-recorded possible temperature ranges based on speed and depending on the filament material. This makes it possible to control the manufacturing of the object within achievable temperature and speed ranges while maintaining satisfactory quality of the manufactured object.

[0013] Furthermore, taking into account the evolution of the extruder's actual temperature over time allows for consideration of the extruder's thermal inertia and for anticipating variations in printing speed settings. Thus, the cooling or heating of the extruder can be anticipated by modeling the extruder temperature after the heating element is switched off.

[0014] The dynamics of the thermal variation of the extruder are therefore taken into consideration to determine the temperature and speed instructions to be transmitted to the additive manufacturing device.

[0015] Controlling the printing speed based on the actual temperature of the extruder makes it possible to avoid temporary stops in the manufacturing process, as well as manufacturing defects that such temporary stops can cause.

[0016] This makes it possible to reduce the manufacturing time of the object by optimizing printing speeds according to the temperature of the extruder nozzle.

[0017] For example, the additive manufacturing device includes an extruder comprising a screw, configured to extrude a filament of material. Other techniques for printing objects by additive manufacturing through filament extrusion could be used.

[0018] Preferably, when ordering the additive manufacturing device, a code is generated containing, in particular, printing speed instructions and extruder temperature instructions intended to be transmitted to the additive manufacturing device.

[0019] Advantageously, the process further includes a calibration step prior to the slicing step, during which the evolution of the extruder temperature as a function of time is determined by correlation between a mathematical model and the actual temperature of the extruder.

[0020] For example, during the calibration step, the extruder is modeled as a second-order system whose coefficients are, for example, determined experimentally. A second-order system is typically characterized by a second-order differential equation with constant coefficients such as the The natural frequency, damping factor, and static gain are determined. The second-order differential equation is obtained using the Laplace transform. The determination of the second-order differential equation and the constant coefficients is known and will not be described further.

[0021] Alternatively, the evolution of the extruder temperature could be determined directly as a function of the actual temperature of the extruder.

[0022] The process may, for example, include a step of modeling said object to be reproduced or manufactured before the step of ordering the additive manufacturing device.

[0023] Advantageously, during the slicing step, the object model obtained in the modeling step is converted into a series of several layers corresponding to the construction steps of the printed object.

[0024] Preferably, the process further includes a step of printing the object according to the printing speed instructions and the temperature instructions of the extruder determined in the control step of the additive manufacturing device.

[0025] Advantageously, the process further includes, before the slicing step, a mapping characterization step.

[0026] For example, the mapping characterization step includes: - a step of estimating a minimum estimated temperature of the extruder allowing the smooth and continuous extrusion of the filament; - a step to determine a temperature range within which a predetermined object can be printed without visible external defects; and - a step of verifying said temperature range by printing said object.

[0027] For example, during the estimation step, if the time required to extrude a length of filament in the extruder at an initial temperature is equal, to within 10%, to a theoretical loading time of the same length of filament in the extruder at a given loading speed, the initial temperature corresponds to the estimated minimum temperature of the extruder, otherwise the operation is repeated by decrementing the temperature by a value between 5°C and 10°C.

[0028] By "theoretical duration" we mean the length of filament to be extruded divided by the required loading speed.

[0029] For example, during the determination step, the printing speed is set, a first layer or set of layers is printed at the estimated minimum temperature, and successive layers are printed, increasing the temperature by a value between 5°C and 10°C for each layer or set of layers, for example, ten layers, until a maximum temperature is reached. The maximum temperature is determined based on the print quality; if, during the printing of a layer, the quality of the object is below a quality threshold, in particular the extraneous filament is not continuous, the maximum temperature corresponds to the printing temperature of the previous layer.

[0030] For example, during the minimum printing temperature verification step, for a given speed, a first layer or a first set of layers is printed at the minimum temperature determined during the estimation step and successive layers are printed by decrementing the temperature by a value between 5°C and 10°C at each layer or set of layers until a minimum temperature is reached, the minimum temperature being determined according to the quality of the print, if during the printing of a layer or set of layers, the quality of the object is below a quality threshold, in particular the extruded filament is not continuous and the successive printed layers are peeling off each other, the minimum temperature corresponds to the printing temperature of the previous layer.

[0031] Advantageously, the mapping characterization step includes a step of determining a range of maximum printing speeds as a function of the temperature range defined during the determination step and the verification step.During the step of determining a range of maximum printing speeds, a layer or set of layers with a rectangular or square cross-section is printed at a minimum printing speed for at least one out of two temperature values ​​in said temperature range, and successive layers or sets of successive layers with a rectangular or square cross-section are printed by increasing the printing speed by a value between 5mm / s and 10 mm / s until a maximum speed is reached, the maximum printing speed being determined according to the print quality; if, during the printing of a layer, the quality of the object is below a quality threshold, the maximum printing speed corresponds to the printing speed of the previous layer.

[0032] Advantageously, the mapping characterization step includes a step for determining a range of optimal printing speeds based on the temperature range defined during the determination step and the verification step. During the step for determining a range of optimal printing speeds, a layer or set of layers with a cylindrical cross-section is printed at a minimum printing speed for at least one out of every two temperature values ​​within said temperature range, and successive layers or sets of successive layers with a cylindrical cross-section are printed by increasing the printing speed by a value between 5 mm / s and 10 mm / s until an optimal printing speed is reached. This optimal printing speed is determined based on the print quality; if, during the printing of a layer or set of layers, the quality of the object is below a quality threshold, In particular, the extraneous filament is not continuous, the successive printed layers detach from each other, and the diameter of the printed object is not continuous, the optimal printing speed corresponds to the printing speed of the previous layer.

[0033] Advantageously, the mapping characterization step includes a compilation step of the steps of determining a temperature range in which an object is printable without visual defects and of determining a range of optimal printing speeds to obtain the mapping of achievable speeds as a function of temperature illustrating the temperature range in which an object is printable without visual defects at an optimal printing speed.

[0034] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0035] [Fig.1] represents the synoptic diagram of an additive manufacturing process for one or more three-dimensional objects according to the invention;

[0036] [Fig.2] represents in detail the step of determining a temperature map of the extruder as a function of the printing speed of the manufacturing process according to [Fig. 1]; and

[0037] [Fig.3] illustrates the temperature mapping of the extruder as a function of the printing speed of [Fig.2].

[0038] The additive manufacturing process 10 of one or more three-dimensional objects includes a step 11 of modeling an object to be reproduced or printed and a step 12 of controlling an additive manufacturing device (not shown) by extruding a filament.

[0039] For example, the additive manufacturing device includes an extruder comprising a screw, configured to extrude a filament of material.

[0040] The additive manufacturing device can also use a printing nozzle configured to calibrate the diameter of the molten material filament.

[0041] Such an extruder is generally moved in space, using a system controlled by an electronic control unit in order to deposit the extruded material onto a receiving tray.

[0042] Other techniques for printing objects by additive manufacturing by filament extrusion could be used.

[0043] Step 12 of the additive manufacturing device control includes a slicing step 13 during which the model of the object to be manufactured is converted into a a series of several layers, of varying thickness, corresponding to the different stages of construction of the printed object.

[0044] The slicing step 13 generates a code containing all the printing instructions transmitted to the additive manufacturing device.

[0045] The code generated in step 13 contains in particular the printing speed instructions V_cons and the temperature instructions T_cons of the extruder.

[0046] However, not all printing speeds are achievable for a given temperature.

[0047] Indeed, when the temperature of the extruder is higher than the degradation temperature of the printed material, a minimum flow rate is necessary to prevent the filament from remaining too long in the heating element, i.e. in the extruder, and the printed material from reaching its degradation temperature.

[0048] To remedy this drawback, the slicing step 13 generates the printing speed instructions V_cons and the temperature instructions T_cons of the extruder as a function of a mapping C(T°, V) of the printing speed V as a function of the temperature T° of the filament at the exit of the extruder and as a function of the evolution of the temperature of the extruder as a function of time t.

[0049] The C(T°, V) mapping allows for possible temperature ranges depending on the speed, pre-recorded and dependent on the filament material.

[0050] The C(T°, V) mapping is determined for a given extruded filament material during a characterization step 20, generating said mapping of achievable speeds as a function of temperature. The mapping characterization step 20 is performed before the slicing step 13.

[0051] Step 20 of mapping characterization will be described with reference to [Fig.2].

[0052] In order not to impact the printing time of the object, the slicing step 13 anticipates the variation in speed by taking into account the thermal inertia of the extruder.

[0053] To this end, the process includes a calibration step 15 during which the evolution of the temperature of the extruder is determined as a function of time t by correlation between a mathematical model M(T°real, t) and the evolution of the measured temperature T°_real of the extruder.

[0054] Calibration step 15 allows the need for temperature change to be predicted and the speed control setpoint to be adapted.

[0055] During calibration step 15, the extruder is modeled as a second-order system whose characteristics are determined experimentally.

[0056] Thus, the cooling or temperature rise of the extruder can be anticipated by modeling M (T°_real, D) the temperature of the extruder after the heating has stopped.

[0057] The dynamics of the thermal variation of the extruder are therefore taken into consideration deration to determine the temperature and speed instructions to be transmitted to the additive manufacturing device.

[0058] This also makes it possible to avoid any temporary stoppage of printing to reach a temperature setpoint, and therefore reduces the duration of printing the object.

[0059] Step 12 of the control of the additive manufacturing device further includes a step 14 of transmission of the printing speed instructions V_cons and the temperature instructions T_cons to the additive manufacturing device.

[0060] The additive manufacturing process 10 further includes a step 16 of printing the object according to the temperature and speed instructions determined in step 12 of controlling the additive manufacturing device.

[0061] Fig. 2 illustrates in detail step 20 of characterization of the C(T°, V) mapping.

[0062] The C(T°, V) mapping of achievable speeds as a function of temperature is de completed as follows:

[0063] In a first step 21, a minimum estimated temperature T_min_est of the extruder heating element is estimated to allow for the smooth and continuous extrusion of a filament. To do this, the time required to load a length of filament into the extruder without temperature constraints is compared with the time required to extrude a length of filament at an initial temperature, for example between 60° and 450°, for example between 200°C and 225°C, for example equal to 205°C, for example equal to 225°C.

[0064] If the time required to extrude a length of filament at an initial temperature is equal, to within 10%, to the theoretical time required to load the same length of filament at a given loading speed, the initial temperature corresponds to the minimum temperature of the extruder. The theoretical time corresponds to the same length of filament extruded divided by the loading speed.

[0065] In a second step 22, the printing speed is set and the temperature range in which a predetermined object can be printed without visible external defects is determined. For this, for a given speed, for example, equal to 5 mm / s, a first layer is printed at the estimated minimum temperature T_min_est and successive layers are printed by incrementing the temperature by an increment value, between 1°C and 5°C, for each layer, or a set of layers, for example ten layers, until a maximum temperature T_max is reached.

[0066] By way of non-limiting example, the maximum temperature T_max is between 10°C and 100°C relative to the minimum temperature T_min.

[0067] The maximum temperature T_max is determined based on the print quality visible from the outside. If, during the printing of a layer, the quality of the object is not satisfactory, for example, the extruded filament is not continuous, the The maximum temperature will be the printing temperature of the previous layer.

[0068] In a third step 23, the temperature range is checked by printing said object and in particular the minimum printing temperature.

[0069] For this, for a given speed, for example, equal to 5 mm / s, a first layer is printed at the minimum temperature T_min_est determined during the estimation step 21, and successive layers are printed by decrementing the temperature by a value between 1°C and 5°C at each layer until a minimum temperature T_min is reached.

[0070] The minimum temperature T_min is determined based on the print quality visible from the outside. If, during the printing of a layer, the quality of the printed object is unsatisfactory—for example, if the extruded filament is not continuous and successive printed layers detach from one another—the minimum temperature will be the printing temperature of the previous layer. The minimum temperature T_min may be equal to the estimated minimum temperature T_min_est.

[0071] This gives a range of temperature values ​​in which a predetermined object can be printed without visible external defects.

[0072] In a fourth step 24, a range of maximum printing speeds V_max is determined as a function of the temperature range determined in steps 22 and 23 by printing successive layers of rectangular or square cross-section.

[0073] In general, successive layers could be printed with a cross-section of a different geometric shape, provided that the geometric shape allows the printing speed to be achieved. For example, successive layers could be printed with a cross-section in the shape of a circle, oval, etc.

[0074] Thus, for each stored temperature value, or at least every other one, a layer or set of layers is printed at a minimum printing speed V_min, for example, 0 mm / s, and successive layers or sets of layers are printed by increasing the printing speed by 5 mm / s until a maximum speed Vmax is reached. The maximum printing speed Vmax is determined based on the print quality. If, during the printing of a layer, the quality of the printed object is unsatisfactory, for example, if the extruded filament is not continuous and the successive printed layers separate from each other, the maximum printing speed Vmax will be the printing speed of the previous layer.

[0075] In a fifth step 25, a range of optimal printing speeds V_opt is determined as a function of the temperature range determined in steps 23 and 24 by printing successive layers of cylindrical section.

[0076] Thus, for each stored temperature value, or at least one out of two, we Prints a layer or set of layers, for example ten layers, at a minimum printing speed V_min, for example 0 mm / s. Then, print successive layers or sets of layers, increasing the printing speed by 5 mm / s until an optimal printing speed V_opt is reached. The optimal printing speed V_opt is determined based on the print quality. If, during the printing of a layer, the object quality is unsatisfactory—for example, the extruded filament is not continuous, successive printed layers detach from each other, and the diameter of the printed object is not continuous—the optimal printing speed V_opt will be the printing speed of the previous layer.

[0077] Finally, in step 26, the different values ​​obtained in the previous steps 22, 23, 24 and 25 are compiled to obtain the C(T°, V) map of achievable speeds as a function of temperature illustrated in [Fig.3].

[0078] Fig. 3 represents the C(T°, V) mapping of attainable speeds as a function of temperature, comprising temperature T in degrees Celsius (°C) on the abscissa and speed V in mm / s on the ordinate.

[0079] The dotted area corresponds to an area in which the filament is degraded during printing. This area is therefore unusable for printing an object.

[0080] The hatched area corresponds to an area in which the printing speed is optimal V_opt to guarantee satisfactory print quality.

[0081] The dashed area corresponds to an area in which the printing speed is maximum V_max but does not guarantee satisfactory print quality.

[0082] For example, when the temperature of the extruder nozzle is at 265°C and the printing speed is 15 mm / s, in the case where it is necessary to reduce the printing speed to 10 mm / s, the temperature of the extruder must be reduced to 255°C.

[0083] Similarly, when the extruder temperature is at 245°C and the printing speed is 15 mm / s, if it is necessary to increase the printing speed to 20 mm / s, the extruder temperature must be increased to 250°C.

[0084] In the illustrated example, the temperature on the x-axis is limited to 275°C. However, if the material used allows it, the entire set of curves can be extended beyond 275°C.

[0085] Thanks to the additive manufacturing process according to the invention, the printing speed is controlled according to a printing speed and temperature map, specific to the material of the extruded filament, and according to the actual temperature of the extruder.

[0086] Controlling the printing speed based on the actual temperature of The extruder makes it possible to avoid temporary stops in the manufacturing process, as well as the manufacturing defects that such temporary stops can cause.

[0087] This makes it possible to reduce the manufacturing time of the object by optimizing printing speeds according to the temperature of the extruder nozzle.

Claims

Demands

1. A method (10) for additively manufacturing at least one three-dimensional object using at least one additive manufacturing device for filament extrusion, the method comprising a step (12) for controlling said additive manufacturing device to manufacture said object, characterized in that during said control step (12): - during a slicing step (13), printing speed commands (V_cons) and temperature commands (T_cons) for the extruder of said additive manufacturing device are generated as a function of a map (C(T°, V)) of the printing speed (V) dependent on the temperature of the extruder (T°), said map being specific to the material of the extruded filament, and as a function of the evolution of the actual temperature of the extruder as a function of time (t), and - during a transmission step (14),the aforementioned printing speed (V_cons) and temperature (T_cons) instructions from the extruder to the additive manufacturing device.

2. Method (10) according to claim 1, further comprising a calibration step (15) prior to the slicing step (13), during which the evolution of the temperature of the extruder is determined as a function of time (t) by correlation between a mathematical model and the actual temperature (T°_real) of the extruder.

3. Method (10) according to claim 2, wherein during the calibration step (15), the extruder of the additive manufacturing device is modeled as a second-order system.

4. Method (10) according to any one of the preceding claims, comprising a step (11) of modeling said object to be manufactured prior to the step (12) of controlling the additive manufacturing device.

5. Method (10) according to claim 4, wherein in the slicing step (13), the object modeling obtained in the modeling step (11) is converted into a series of several layers corresponding to the construction steps of the printed object.

6. Method (10) according to any one of the preceding claims, further comprising, before the slicing step (13), a mapping characterization step (20) (C(T°, V)).

7. Method (10) according to claim 6, wherein the step (20) of characterizing the mapping (C(T°, V)) comprises: - a step (21) of estimating an estimated minimum temperature (T_min_est) of the extruder allowing smooth and continuous extrusion of the filament; - a step (22) of determining a temperature range in which a predetermined object is printable without visible external defects; and - a step (23) of verifying said temperature range by printing said object.

8. Method (10) according to claim 7, wherein during the estimation step (21), if the time required to extrude a length of filament in the extruder at an initial temperature is equal, within 10%, to a theoretical time to load the same length of filament into the extruder at a given loading speed, the initial temperature corresponds to the estimated minimum temperature (T_min_est) of the extruder, otherwise the operation is repeated by decrementing the temperature by a value between 5°C and 10°C.

9. A method according to claim 7 or 8, wherein in the determination step (22), the printing speed is fixed, a first layer or a first set of layers is printed at the estimated minimum temperature (T_min_est) and successive layers are printed by incrementing the temperature by a value between 5°C and 10°C at each layer or set of layers until a maximum temperature (T_max) is reached, the maximum temperature (T_max) being determined according to the quality of the print, if during the printing of a layer, the quality of the object is below a quality threshold, in particular the extruded filament is not continuous, the maximum temperature (T_max) corresponds to the printing temperature of the previous layer.

10. A method according to claim 8 or 9, wherein, during the minimum printing temperature verification step (23), for a given speed, a first layer or set of layers is printed at the minimum temperature (T_min_est) determined during the estimation step (21), and successive layers are printed by decrementing the temperature by a value between 5°C and 10°C for each layer until a minimum temperature (T_min) is reached, the minimum temperature (T_min) being determined based on the print quality, if, during the printing of a layer or set of layers, the quality of the object is below a threshold of quality, in particular the extraneous filament is not continuous and the successive printed layers detach from each other, the minimum temperature (T_min) corresponds to the printing temperature of the previous layer.

11. A method according to any one of claims 7 to 10, comprising a step (24) of determining a range of maximum printing speeds (V_max) as a function of the temperature range defined in the determination step (22) and the verification step (23), in the step (24) of determining a range of maximum printing speeds (V_max), a layer or set of layers of rectangular or square cross-section is printed at a minimum printing speed (V_min) for at least one out of every two temperature values ​​in said temperature range, and successive layers or sets of layers of rectangular or square cross-section are printed by incrementing the printing speed by a value between 5 mm / s and 10 mm / s until a maximum speed (V_max) is reached, the maximum printing speed (V_max) being determined as a function of the print quality, if, during the printing of a layer,If the object quality is below a certain quality threshold, the maximum printing speed (V_max) corresponds to the printing speed of the previous layer.

12. A method according to any one of claims 7 to 11, comprising a step (25) of determining a range of optimal printing speeds (V_opt) as a function of the temperature range defined in the determination step (22) and the verification step (23), in the step (25) of determining a range of optimal printing speeds (V_opt), a layer or set of layers of cylindrical cross-section is printed at a minimum printing speed (V_min) for at least one of two temperature values ​​in said temperature range, and successive layers or sets of successive layers of cylindrical cross-section are printed by incrementing the printing speed by a value between 5 mm / s and 10 mm / s until an optimal printing speed (V_opt) is reached, said optimal printing speed (V_opt) being determined as a function of the print quality, if, during the printing of a layer or set of layers,the quality of the object is below a quality threshold, in particular the extruded filament is not continuous, successive printed layers are separating from each other, and the diameter of the printed object is not continuous, the optimal printing speed, (V_opt) corresponds to the printing speed of the previous layer.

13. A method according to claim 12, comprising a step (26) of compiling the steps (22, 25) of determining a temperature range in which an object is printable without visual defects and of determining a range of optimal printing speeds (V_opt) to obtain the mapping (C(T°, V)) of attainable speeds as a function of temperature illustrating the temperature range in which an object is printable without visual defects at an optimal printing speed (V_opt).