Method and system for manufacturing three-dimensional porous structures

Abstract

A method and system for manufacturing a three-dimensional porous structure. Filaments are deposited in a predetermined interconnecting arrangement in a plurality of stacked layers to form a porous structure having interconnected pores. A pressure value indicative is monitored during deposition of the filaments, the pressure value being indicative of a pressure exerted on a build material in a build material reservoir of a nozzle used for deposition. A processing unit is configured to adjust at least one extrusion parameter to compensate for irregular rises and / or falls in the pressure value.

Description

Technical Field

[0001] This invention relates to a method and system for manufacturing three-dimensional porous structures by extruding filaments. The invention also relates to a computer program product. Background Technology

[0002] Additive manufacturing is widely used and encompasses various technologies. It allows for the layer-by-layer construction of structures, which can be used in a wide range of applications.

[0003] Extrusion-based additive manufacturing methods have been used to fabricate porous structures. Materials (e.g., pastes, polymers, hydrogels, etc.) are extruded through a nozzle in the form of filaments. During deposition, a specific arrangement of the filaments is achieved by moving the nozzle relative to the print bed. During material extrusion, the filaments are extruded from the nozzle and positioned relative to each other according to a predetermined pattern, thereby providing the desired properties of the fabricated porous structure. The layup pattern is determined by the print path and has a significant impact on the properties of the printed structure. In this way, complex geometries and porous structures with fully interconnected pore networks can be obtained, which may be required for certain applications.

[0004] The printing process does not always produce the desired porous structure. Anomalies or deviations during printing can result in printed porous structures that do not possess the expected properties. The ability to objectively determine and adjust the quality of the printing process is necessary to ensure one or more properties of the manufactured porous structure (e.g., structural integrity, porosity, etc.).

[0005] When the final porous structure is obtained, potential deformities within the porous structure are often not easily observed. These deformities may not be visible externally. However, they can significantly impact the specifications and / or quality of the porous structure. Therefore, producing porous structures with high precision and reproducibility using conventional printing processes can be challenging. Furthermore, the mechanical and porous properties of porous structures can be quite difficult to predict.

[0006] Existing systems and methods can be cumbersome and difficult to implement in the field. There is a need for improved printing processes to manufacture porous structures using extrusion-based printing techniques with build materials including inorganic particulate materials. A less complex, cumbersome, and / or expensive system and method is required. Furthermore, there is a desire to improve the applicability and print quality of printing porous structures for a wider range of applications. Summary of the Invention

[0007] The purpose of this invention is to provide a method and system for eliminating at least one of the above-mentioned disadvantages.

[0008] Alternatively, the object of the present invention is to improve the additive manufacturing process for three-dimensional porous structures made using building materials comprising at least one inorganic particulate material.

[0009] Alternatively, the purpose of this invention is to better ensure the printing quality or quality of porous structures.

[0010] Alternatively, an object of the present invention is to improve the efficiency of extrusion-based additive manufacturing processes that utilize building materials comprising at least one inorganic particulate material to create porous structures.

[0011] Therefore, the present invention provides a method for manufacturing a three-dimensional porous structure, the method comprising the steps of: providing an extrusion unit including a nozzle having a nozzle outlet and a build material reservoir in fluid communication with the nozzle outlet, the build material comprising inorganic material particles dispersed in a binder and at least one solvent; depositing filaments of the build material in a predetermined interconnected arrangement in a plurality of stacked layers by the extrusion unit to form a three-dimensional porous structure having interconnected pores; monitoring pressure values ​​by a measurement unit, the pressure values ​​indicating the pressure applied to the build material in the build material reservoir during the extrusion of the build material through the nozzle to achieve the deposition of the filaments; and processing the monitored pressure values ​​by a processing unit to detect one or more deposition irregularities by identifying irregular rises and / or falls in the pressure values ​​relative to a steady-state level reached during extrusion, wherein during an irregular rise, the pressure value instantaneously surges and then returns to its steady-state level, wherein during an irregular fall, the pressure value instantaneously decreases and then returns to its steady-state level, and wherein the processing unit is configured to adjust at least one extrusion parameter to compensate for the irregular rises and / or falls in the pressure values.

[0012] Advantageously, by compensating for pressure value irregularities as they gradually develop, potential printing errors can be prevented. As an alternative to sudden process interruptions due to irregularities already formed in the printing structure, the present invention can adjust printing parameters and / or conditions to compensate for or even prevent irregularities in the build material dispensed by the nozzle, thereby providing, for example, stable printing operation without (or at least with reduced) printing errors. The severity of printing errors can be effectively reduced.

[0013] The evolution of pressure values ​​over time during filament deposition can indicate deposition quality. Fluctuations can indicate irregular extrusion of build material from the nozzle and / or irregular deposition of the filaments, leading to irregularities in the deposited filaments. Based on how pressure values ​​(or other values ​​indicating pressure, such as force) diverge or fluctuate during filament deposition, the risk of deposition defects in the fabricated porous structure, as well as the severity or extent of these defects, can be inferred. Events or patterns in the pressure value data can be identified to determine the causes of deposition defects.

[0014] Advantageously, the present invention provides an accurate method that not only detects potential problems early but also compensates for, prevents, or minimizes these problems during filament deposition, thereby preventing or minimizing errors during extrusion. Specifically, the invention provides a method for adjusting one or more deposition parameters as the build material travels toward and through the nozzle, such that problems present during the travel of the build material through and / or extrusion from the nozzle can be compensated to a desired degree before filament deposition. In this way, the presence of poorly printed portions or defects in the deposited filament can be minimized, or at least the severity of such portions or defects can be reduced. Therefore, the present invention provides a method for reducing or even preventing poorly printed portions or defects in the deposited filament during filament production. This better ensures optimal structural integrity of the porous structure. Using pressure / force data is particularly advantageous compared to using flow data from a flow sensor because it allows for simpler and more cost-effective designs.

[0015] By monitoring one or more of the parameters mentioned above, the risk of forming one or more poorly printed portions, such as those affecting structural quality and / or integrity, can be determined more accurately. During the printing process, cost-effective management allows for better and faster identification of potential printing defects. Therefore, post-printing inspection of porous structures is no longer necessary. Potential defects can be detected and at least partially compensated for during the printing process. This reduces material loss, particularly reducing the severity of defects and / or the number of three-dimensional structures containing defects. Defects in porous structures can be associated with deposition defects identified using the method according to the invention.

[0016] Pressure values ​​can be monitored during filament discharge through the extrusion unit. Based on the pressure monitoring data, the deposition quality of the filament can be evaluated. This can be performed in real time, and one or more filament deposition parameters can be adjusted in real time. For example, during normal filament deposition, the pressure value can remain within a steady-state level (which can be a range or envelope). In other words, the pressure value can vary within a predetermined range or envelope. In some examples, the pressure value has a substantially linear slope. However, a sudden spike or dip in the pressure value relative to the steady-state level of the pressure value (see breaking the range or envelope) can indicate irregular discharge of build material through the nozzle opening. Such irregular discharge is associated with impending deposition defects that affect the properties of the manufactured porous structure. This invention is capable of... Adjusting extrusion parameters and This can at least partially mitigate the severity of such depositional defects, or even prevent them altogether.

[0017] Discharge irregularities can significantly impact the properties and mechanical characteristics of the manufactured porous structure, such as integrity, mechanical strength, and pressure resistance. The amount of pressure applied to the build material in the build material reservoir for discharge through the nozzle opening can be monitored and processed to effectively identify the risk of forming one or more discharge irregularities. Data processing enables accurate and objective characterization of the forming porous structure. Discharge irregularities are associated with irregular rises and / or falls in data indicating the pressure applied to the build material in the fluid reservoir.

[0018] Patterns in the monitored pressure data can be correlated with irregularities during extrusion. For example, when the data is represented as a graph over time, unexpected spikes or troughs can be observed. Such spikes or troughs in the data can indicate that at the moment of their occurrence, filament deposition was irregular.

[0019] The properties of the porous structure being manufactured can be affected by the conditions during the deposition of filaments through a nozzle, and in this invention, these conditions can be adjusted during filament deposition to control the deposition process toward the desired properties of the porous structure. Potential deposition errors in the manufactured structure can be effectively prevented.

[0020] For example, a nozzle may incorrectly deposit filaments due to blockage at the nozzle opening or in the supply line leading to the nozzle. Due to the blockage, pressure can build up, the supply line or nozzle may become partially blocked, and less build-up material can be deposited through the nozzle opening. If sufficient pressure has built up, some build-up material can be discharged through the nozzle opening to overcome the blockage. This irregular deposition of the filaments results in localized deformation and / or varying diameters. This can be associated with porous structural defects that can significantly affect the quality of the manufactured product. Advantageously, the processing unit can control the extrusion unit to, for example, adjust extrusion parameters to compensate for irregular increases and / or decreases in pressure values.

[0021] Air voids within the build material can also lead to detectable deposition irregularities. These air voids can cause a sudden drop in pressure relative to the steady-state level on the build material. If the air voids are removed through the nozzle opening during deposition, the pressure level can recover to near the steady-state level after the sudden drop (see negative peak). However, due to the irregular drop / reduction relative to the steady-state level, irregular deposition of the filaments may have occurred, which can affect the quality of the manufactured product. Irregular deposition can introduce defects in the resulting porous structure.

[0022] The monitored pressure values ​​may have a first set of fluctuations falling within the range of the steady-state level and a second set of fluctuations that at least partially reach values ​​outside the range of the steady-state level, wherein the second set of fluctuations is used to identify depositional irregularities. A (local) minimum point can be reached when the pressure value decreases (i.e., drops). A (local) maximum point can be reached when the pressure value reaches its peak.

[0023] When filamentous material is deposited under normal conditions, it can reach pressure values ​​that fall within the steady-state level. A sudden decrease or increase in pressure values ​​outside the steady-state level can indicate depositional irregularities.

[0024] The processing unit can be configured to perform peak analysis on the monitored pressure values. Positive and / or negative peaks that deviate from steady-state levels can be identified, indicating deposition irregularities associated with (manufacturing) defects in the porous structure.

[0025] The processing unit is configured to control the extrusion unit to, for example, adjust the extrusion parameters to compensate for irregular increases and / or decreases in pressure values.

[0026] Optionally, adjusting the extrusion parameters includes at least one of the following: adjusting the pressure of the build material applied to the build material reservoir and / or the pressure of the build material applied to the nozzle; adjusting the viscosity of the build material in the build material reservoir and / or the viscosity of the build material in the nozzle; adjusting the flow rate of the build material; adjusting the opening of the nozzle; adjusting the actuation of the extrusion screw in the nozzle; or providing vibration to the build material.

[0027] It should be understood that the pressure applied to the build material can be adjusted at any point on the build material supply line before the printing material leaves the nozzle.

[0028] The printing material can be subjected to vibration in different ways. In some examples, piezoelectric actuators are used. The amplitude of the vibration can be adjusted based on the identified pressure irregularities. In some examples, the frequency of the vibration is adjusted based on the identified irregularities.

[0029] Optionally, the viscosity of the building material in the building material reservoir can be adjusted by at least one of the following methods: adjusting the temperature of the building material; adjusting the amount of solvent contained in the building material; or adding a release agent.

[0030] Heating / cooling can be implemented in the build material reservoir and / or nozzle. However, it should be understood that heating / cooling can be implemented at any point on the build material supply line before the build material leaves the nozzle.

[0031] It should be understood that heating and / or cooling of the building materials can be achieved in various ways, such as using resistance heating, microwave heating, using Peltier elements, using induction heating, etc.

[0032] Optionally, the measuring unit includes a load sensor, which can be positioned at... Construct material storage The location is between the material reservoir and the nozzle, and / or at the nozzle.

[0033] The load sensor can be configured to measure data indicating pressure, wherein the processing unit is configured to process the data provided by the load sensor.

[0034] Optionally, the measuring unit is configured to monitor pressure values ​​that indicate the pressure applied to the building material at multiple locations.

[0035] Advantageously, this method can significantly improve measurement accuracy, thereby providing improved control to, for example, avoid potential printing irregularities in a timely manner through early compensation. Optionally, the measurement unit is configured to monitor pressure values ​​in the build material reservoir and nozzle.

[0036] Optionally, when the ratio of steady-state to peak pressure is greater than 15%, more preferably greater than 20%, or even more preferably greater than 25%, irregular increases and / or decreases in pressure relative to the steady-state level reached during deposition are identified. These sudden fluctuations in pressure can be considered key events that can lead to defects in the porous structure being manufactured.

[0037] Alternatively, the steady-state level is a substantially stable level (see range, band, envelope, etc.). It should be understood that a steady state can be understood as a region where a quantity remains level or stable over a period of time. A steady state can have a substantially stable level. However, the steady-state level can also be slightly sloping (e.g., gradually decreasing or increasing).

[0038] Optionally, the processing unit is configured to associate one or more identified deposition irregularities with one or more deposition defects in the porous structure, wherein the severity of the deposition defect is determined based on the magnitude and / or shape of the irregular rise and / or fall of the pressure value relative to the steady-state level reached during deposition.

[0039] The magnitude and / or shape of irregular rises and / or falls in pressure values ​​can indicate the impact on deposition. This can be considered when determining how severe the defects in a porous structure are. Additionally or alternatively, as noted above, the location of deposition irregularities can also be considered to determine the severity of deposition defects.

[0040] The difference in amplitude between the baseline and (positive or negative) peak of the steady-state level can provide an indication of the severity of depositional defects.

[0041] Optionally, the number of times the pressure value rises and / or falls irregularly relative to the steady-state level can be considered to determine the severity of defects in the manufactured porous structure.

[0042] Optionally, the processing unit is configured to determine the location of the identified deposition defects in the porous structure based on the position of the nozzle in the printing path when deposition irregularities are detected.

[0043] During filament deposition, the print bed (e.g., print platform, print surface) and nozzles move relative to each other. For example, the nozzles may move relative to the print bed during deposition. Alternatively, the print bed may move relative to the nozzles during deposition. Therefore, the location of deposition defects caused by deposition irregularities can be determined, for example, by monitoring the movement of the print bed and / or nozzles.

[0044] In the example, the location of deposition defects within the porous structure is determined based on the time step or time interval in which deposition irregularities occur. The location of these irregularities during printing can be determined based on the time step or time interval and the printing path. This indicates the impact of deposition defects on the porous structure. Optionally, this impact can be quantified or associated with a specific defect classification.

[0045] Optionally, the processing unit is configured to determine one or more defect (e.g., weak) regions in the fabricated porous structure based on the location of one or more identified deposition defects in the porous structure.

[0046] Build materials with desired properties can be prepared depending on the application in which the build material will be used (see Applications of Porous Structures). The pressure applied to the build material reservoir during the (normal) discharge of the filaments can be at a certain steady-state level. This steady-state level can be a range that allows for small variations. The processing unit can be configured to process data acquired during filament deposition to identify patterns associated with extrusion irregularities. This pattern can be a sudden or steep peak or trough that breaks out of the range of the steady-state level. Such sudden fluctuations in pressure indicate deposition irregularities, thereby indicating defects generated in the porous structure.

[0047] Optionally, the processing unit is configured to estimate the impact of one or more defect (e.g., weak) regions on the structural integrity of the porous structure based on at least one of the location and severity of the deposited defects at the defect region, wherein the processing unit is configured to determine or estimate whether the printed porous structure meets the target properties, particularly whether it meets one or more of the strength and geometric effects, based on the estimate of the impact of the one or more weak regions on the structural integrity of the porous structure.

[0048] Optionally, the processing unit is configured to adjust the extrusion parameters based on observed pressure fluctuations and estimates of the impact of one or more weak zones on the structural integrity of the porous structure to compensate for irregular increases and / or decreases in pressure values.

[0049] In some cases, adjusted extrusion parameters may not completely prevent the formation of deposition irregularities. Deposition irregularities can introduce defects into the resulting porous structure that can affect its structural integrity. Based on the detected defects in the porous structure, it can be determined whether the porous structure meets the target quality or strength requirements for the manufactured porous structure.

[0050] Optionally, the processing unit employs a computational model to determine or estimate the impact of one or more weak zones on the structural integrity of the porous structure, wherein the filaments are modeled at the locations of one or more detected deposition defects using the corresponding detected irregular rise or fall diameter based on pressure values.

[0051] The location of defects in a porous structure can be determined based on the moment when deposition irregularities occur during manufacturing. The severity of the defects can depend particularly on their location. This can be assessed by the processing unit using computational models. For example, computational models can be based on analytical models, empirical models, and / or numerical models (e.g., the finite element method). Hybrid models can also be used. Alternatively, artificially trained networks can be used to determine whether a porous structure with identified deposition defects meets desired properties. Other models can also be used. For example, a model can correlate the location and / or size of defects with a predetermined influence factor indicating the severity of the defects. It is also envisioned to use multiple models to assess the impact of identified defects on the quality of the porous structure.

[0052] Optionally, if it is identified that one or more deposition defects in the porous structure are caused by one or more deposition irregularities, the fabrication of the porous structure is cancelled early.

[0053] During the fabrication of porous structures, one or more depositional irregularities may occur, leading to one or more defects in the porous structure. These defects can result in a porous structure with different properties or characteristics compared to the porous structure to be fabricated.

[0054] Even during the extrusion process, process parameters can be followed to detect deposition errors or defects at any time. Deposition errors or defects can be caused by one or more deposition irregularities that cause irregular rises and / or falls in pressure values. This can be caused, for example, by at least one of gas or vapor bubbles, air bubbles, or nozzle blockage. Advantageously, in this way, the quality of the resulting printed porous structure can be significantly improved.

[0055] Optionally, during the deposition of filaments to create a porous structure, the impact of one or more weak zones is estimated, and the extrusion parameters are adjusted or the manufacturing process is canceled early based on the estimates of the impact.

[0056] The processing unit can adjust one or more extrusion parameters to compensate for irregular increases and / or decreases in pressure values. Alternatively, if printing irregularities are too severe, the processing unit can stop the printing process. In this way, manufacturing efficiency can be significantly improved. If printing irregularities result in unacceptable properties or characteristics of the porous structure compared to the desired properties or characteristics of the porous structure to be manufactured, then it is no longer necessary to complete the printing of the porous structure.

[0057] Optionally, the measuring unit includes a load sensor that can be positioned at the build material reservoir, between the build material reservoir and the nozzle, and / or at the nozzle. The load sensor is configured to measure data indicating pressure in the build material reservoir, wherein the processing unit is configured to process the data provided by the load sensor.

[0058] A load sensor provides a simple way to obtain pressure values, indicating the pressure applied to the build material in the build material reservoir for discharge through the nozzle opening. Sensor data from the load sensor can be easily analyzed and processed by a processing unit. In this way, a cost-effective solution for monitoring pressure values ​​is obtained.

[0059] Optionally, the sensor is a load sensor including a transducer arranged to generate an electrical signal whose magnitude is proportional to the force being measured, wherein the load sensor is arranged to measure the force applied to discharge the build material out of the nozzle.

[0060] Load sensors can be easily integrated into nozzles. They are also robust and can be used to monitor the load / pressure applied to porous structures in real time. Many types of load sensors exist and can be used. The use of multiple load sensors in a nozzle is also envisioned.

[0061] Deposition defects can be more easily identified by using a load sensor at the nozzle to receive data indicating the pressure value applied to the build material in the build material reservoir.

[0062] Potential deposition irregularities can be identified as irregular increases and / or decreases in pressure values ​​relative to a steady-state level reached during filament deposition. This invention provides an early compensation method to, for example, compensate for irregular increases and / or decreases in pressure values. The steady-state level can be a range of pressures from which build-up material is consistently extruded from the nozzle opening. A load sensor can be arranged and configured to determine what force is applied to the build-up material (e.g., a paste) and how that force changes over time during filament deposition. During the initialization of filament deposition, a stabilization time may be required for the pressure to change gradually. The controller can be arranged to take this into account and wait until a steady-state level is reached. The pressure value can be substantially stabilized at this steady-state level, such that it remains within a band or range (see envelope) during normal deposition. If the pressure value deviates from the steady-state level due to a sudden spike or drop, this can be identified as an impending or effective deposition defect caused by malfunction of the nozzle. A reservoir can be filled with build-up material. This can be performed while minimizing the amount of air introduced into the reservoir. The nozzle can be selected for extruding the build-up material to deposit filaments of a certain thickness. A pump can be used to push a constant flow from the reservoir out of the nozzle.

[0063] Different types of pumps can be used, such as injection pumps. Injection pumps may include stepper motors configured to operate at a constant speed using a spindle to achieve a substantially constant volumetric flow rate discharged from the nozzle opening.

[0064] The reservoir can have the same diameter as a standard syringe that can be used in a pump. This ensures better flow rate. Inside the reservoir, the paste can be sealed at the top, for example, by the rubber of a plastic syringe acting as a piston. The piston can be driven by a spindle to force the paste through the nozzle opening of the nozzle.

[0065] The printing process can be controlled by a load sensor. During printing, the load sensor can be used to determine the force applied to the build material in the reservoir. The load sensor can be placed between the pump that rotates the spindle and the reservoir. It should be understood that other arrangements are also possible. For example, the load sensor can be configured to operate based on a Wheatstone bridge.

[0066] Optionally, the measuring unit further includes a flow sensor configured to measure a flow value indicating the flow rate of the build-up material extruded through the nozzle outlet, wherein the processing unit is configured to process the flow data to determine one or more flow irregularities, which are formed by irregular increases and / or decreases in flow rate relative to the steady-state flow rate level during deposition.

[0067] Flow rate also provides an indication of the deposition quality during printing. Therefore, data provided by the flow sensor can be used to achieve an improved assessment of deposition defects.

[0068] Alternatively, the flow sensor is arranged to perform non-contact flow measurement to determine the flow rate of the building material discharged through the nozzle opening of the nozzle. Non-contact flow measurement is particularly advantageous because the building material can be a viscous paste, which can be quite sticky.

[0069] Alternatively, the flow sensor is a microfluidic flow sensor. This type of microfluidic sensor is capable of measuring flow rates of a few microliters per minute (µL / min).

[0070] Alternatively, the flow sensor is a laser Doppler vibratory flow meter.

[0071] Alternatively, the flow sensor is a thermally based flow meter, which is configured to provide a thermal pulse to the building material and detect the temperature of the building material further downstream. The flow rate can be determined based on the temperature change.

[0072] Alternatively, flow sensors are arranged to determine flow rate based on recorded balance. In this way, flow rate can be determined based on mass density.

[0073] Optionally, the final manufactured structure is further characterized by a vision system, such as a camera system.

[0074] Optionally, the processing unit is configured to control the extrusion unit to, for example, adjust extrusion parameters (e.g., pressure applied to the printing material) to compensate for irregular increases and / or decreases in pressure values ​​detected by the measuring unit. In some examples, in the event of detected irregular increases and / or decreases in pressure values, the extrusion unit may be configured to apply greater or less pressure to the build material in a timely manner during filament deposition.

[0075] When a sudden drop / peak is detected, the operable nozzle can apply greater pressure to the build material to discharge it through the nozzle opening. A sudden peak may indicate that the nozzle opening is blocked, so intervening by applying greater pressure can overcome this problem more quickly. In this way, the severity of defects in the porous structure can be reduced. In the event of a sudden drop or decrease in pressure, the pressure can be increased to release the gas pressure within the build material more quickly.

[0076] A feedback loop can be configured to control the pressure based on the measured pressure value. When deposition irregularities are detected, immediate action can be taken to control the operating parameters of the porous structure, thereby adjusting the pressure applied to the build material.

[0077] Optionally, the steady-state level has a baseline envelope that forms segments with upper and lower limits, wherein irregular increases and / or decreases in the pressure value relative to the steady-state level are identified when the pressure value breaks through the baseline envelope of the steady-state level.

[0078] Monitor the pressure values ​​that indicate the pressure applied to the build material in the build material reservoir over time. Irregular increases and / or decreases in pressure values ​​can be identified if actual measurements during deposition fall outside the baseline envelope of the steady-state level.

[0079] Optionally, the method further includes evaluating the quality of the extruded porous structure, wherein the quality is based on the number and / or severity of compensatory actions following the identification of deposition defects.

[0080] The overall quality of the porous structure can be objectively quantified based on compensatory actions and / or defects detected within the porous structure. These compensatory actions and / or defects are determined by a processing unit that processes data acquired during filament deposition to identify patterns in the data associated with extrusion irregularities. Patterns can be identified based on one or more fluctuations resulting from spikes or drops in pressure values ​​relative to a steady-state level (which may be a range or band).

[0081] Optionally, the controller takes into account the settling time required for the pressure to fully build up and stabilize at a steady-state level. The settling time may depend on the material properties of the building materials.

[0082] It should be understood that fluctuations can be considered as irregular increases or decreases relative to the steady-state level by a significant amount. A significant change relative to the baseline steady-state level can be, for example, greater than 10%, greater than 15%, greater than 20%, or greater than 30%.

[0083] Optionally, in the pressure data, the ratio between the (negative or positive) peak at the irregular rise / fall and the steady-state level is greater than 1.2, more preferably greater than 1.2, and even more preferably greater than 1.3.

[0084] Optionally, the processing unit is configured to identify deposition defects in real time by analyzing pressure value data. In this example, pressure value data can be measured and analyzed in real time. By analyzing the pressure values, porous structure defects caused by irregular deposition can be accurately identified and compensated for. Pressure values ​​can be measured, monitored, and processed in real time during filament deposition. In this embodiment, the pressure values ​​can be adjusted in real time during filament deposition.

[0085] Optionally, the processing unit is configured to perform (positive or negative) peak detection to identify deposition irregularities in the measured pressure data and adjust extrusion parameters. A peak detection algorithm that identifies the locations of (local) maximum and minimum pressure data can also be employed.

[0086] According to one aspect, the present invention provides an additive manufacturing system for fabricating a three-dimensional porous structure, the system comprising: an extrusion unit including a nozzle having a nozzle outlet and a build material reservoir in fluid communication with the nozzle outlet, the build material comprising inorganic material particles dispersed in a binder and at least one solvent; an extrusion unit configured to deposit filaments of the build material in a predetermined interconnected arrangement in a plurality of stacked layers to form a three-dimensional porous structure having interconnected pores; and a measurement unit configured to monitor a pressure value indicating the pressure at which the build material is extruded through the nozzle to achieve a three-dimensional porous structure. The present invention includes: pressure applied to the build material in a build material reservoir during the deposition of filaments; and a processing unit configured to process the monitored pressure values ​​to detect one or more deposition irregularities by identifying irregular increases and / or decreases in the pressure values ​​relative to a steady-state level reached during extrusion, wherein during an irregular increase, the pressure value surges instantaneously and then returns to its steady-state level, wherein during an irregular decrease, the pressure value decreases instantaneously and then returns to its steady-state level, and wherein the processing unit is configured to adjust at least one extrusion parameter to compensate for the irregular increases and / or decreases in the pressure values. Optionally, the processing unit is configured to adjust the extrusion parameters to compensate for the irregular increases and / or decreases in the pressure values ​​and to associate one or more identified deposition irregularities with the risk of one or more deposition defects occurring in the porous structure.

[0087] This invention enables the early detection of potential future errors that would otherwise occur if no action is taken. Instead of post-detection of errors that have already occurred, this invention compensates for irregularities in pressure values ​​to, for example, minimize serious printing errors. By monitoring pressure values, future printing irregularities can be detected before they occur (thus enabling compensation for future printing irregularities). This invention provides a method that not only detects problems early but also compensates for, prevents, or minimizes them early in the deposition of filaments, thereby preventing or minimizing errors during extrusion. This invention allows adjustment of one or more deposition parameters as the build material travels toward and through the nozzle, such that problems present during the travel of the build material through and / or extrusion of the nozzle can be compensated for to a desired extent before the deposition of filaments from the nozzle.

[0088] Compared to known systems, the system according to the present invention is easier to apply, more accurate, provides better identification of deposition defects, and is more cost-effective.

[0089] Pressure values ​​can be monitored to detect sudden fluctuations that deviate from a certain steady-state level (e.g., range or band). These sudden fluctuations can be identified based on one or more peaks and / or valleys in the pressure data, which can be associated with extrusion irregularities and thus with defects in the porous structure being manufactured.

[0090] Extrusion conditions can be analyzed during filament deposition to detect one or more deposition defects as a porous structure forms. Therefore, the printing process can be processed in real time by analyzing pressure values ​​monitored during filament deposition. During deposition, pressure values ​​can remain at a steady-state level. Sudden positive or negative peaks (valleys in the graph) that break through the steady-state level indicate deposition irregularities, requiring adjustment of extrusion parameters to compensate for such breaks.

[0091] The steady-state level can be a range with a baseline and upper and lower limits (see band / segment / envelope). Depositional irregularities can be identified at the moment when the pressure value suddenly breaks out of the steady-state level range. Pressure values ​​can have positive and / or negative peaks that fall within the steady-state level and are not identified as depositional irregularities, as well as positive and / or negative peaks that break out of the steady-state level and are identified as depositional irregularities.

[0092] Pressure data can be collected throughout the entire period of filament deposition. Optionally, the predetermined interval can be specified by the user.

[0093] According to one aspect, the present invention provides a computer program product configured to perform the steps of the method according to the present invention when run on a controller.

[0094] When fabricating porous structures, computer program products can provide a tool for monitoring quality or structural integrity by offering immediate feedback during filament deposition. In this example, the computer program product runs on a processing unit.

[0095] Pressure data (or data indicating pressure values, such as force data) can be collected via a measuring unit. The collected pressure data can be stored in a memory. A processing unit receives the collected pressure data for specific data analysis. For example, the data analysis may involve identifying certain events or patterns in the data. These events may be specifically associated with deposition defects. Advantageously, the present invention provides a method for determining the specific cause of defects in a porous structure by detecting sudden fluctuations in pressure data.

[0096] It can automatically identify and eliminate erroneous data points. For example, it can automatically discard outliers and / or outliers. In the example, a curve fitting algorithm is used to identify relevant data points.

[0097] The processing unit can be configured to perform peak characterization to determine the impact of pressure fluctuations on deposition. Irregular rises and / or falls can be local maxima or minima relative to a baseline of steady-state levels.

[0098] When fabricating porous structures, pressure data can be collected at predetermined time intervals during the deposition of the filaments. These predetermined time intervals may include, for example, user-defined time periods. It is also envisioned that pressure data be collected until one or more events or patterns (e.g., fluctuations) are identified by the processing unit.

[0099] The method may further include generating output data, which includes a representation (e.g., a summary) of the type of identified defect (e.g., structural weakness), the affected portion of the porous structure, the severity of the defect, etc. For example, the type of deposition defect may include reduced filament diameter, filament deformation, discontinuity in filament deposition, etc.

[0100] According to one aspect, the present invention provides a system for manufacturing porous structures, the system comprising: an extrusion unit including a nozzle having a nozzle outlet and a build material reservoir in fluid communication with the nozzle outlet, wherein the extrusion unit is arranged to deposit filaments in a predetermined interconnected arrangement in a plurality of stacked layers through the nozzle outlet to form a porous structure with interconnected pores; a measurement unit including at least one sensor for monitoring a pressure value during discharge of the filaments through the extrusion unit, the pressure value being applied to the build material in the build material reservoir of the nozzle for discharge of the build material through the nozzle outlet; and a processing unit configured to process the monitored pressure value to identify irregular increases and / or decreases in the pressure value relative to a steady-state level of pressure reached during discharge, wherein... The processing unit is also configured to control the extrusion unit to, for example, adjust the extrusion parameters. This compensates for irregular increases and / or decreases in pressure values. During the irregular rise, the pressure value surges instantaneously, and during the irregular fall, the pressure value drops instantaneously.

[0101] Sensors may occupy multiple locations within the build material reservoir, but additional sensors may be provided, for example, at the nozzle or any other suitable location. In some examples, sensors are at least directly or indirectly coupled to the nozzle and / or the build material reservoir to, for example, monitor pressure values ​​indicating the pressure applied to the build material in the reservoir during the extrusion of build material through the nozzle to achieve filament deposition.

[0102] It should be understood that the pressure value can be an indication of the pressure or load (e.g., force) applied to the build material in the build material reservoir of the nozzle.

[0103] Pressure values ​​can be correlated with extrusion flow rate or deposition rate. It should be understood that other values, parameters, and / or quantities related to deposition can also be monitored. Deposition irregularities can be detected using at least one of a load sensor (e.g., a load cell), a flow meter, or an imaging system. By monitoring quantities related to deposition, the quality of the deposition can be assessed.

[0104] According to one aspect, the present invention provides a method for evaluating the quality of structures manufactured by extrusion.

[0105] According to one aspect, the present invention provides a method for detecting defects in a porous structure under manufacturing.

[0106] According to one aspect, the present invention provides a method for evaluating the structural integrity of a porous structure manufactured by extrusion.

[0107] According to one aspect, the present invention provides a method for analyzing the extrusion of porous structures.

[0108] According to one aspect, the present invention provides a method for evaluating the quality of a structure manufactured by extrusion, the method comprising: providing a measuring unit including at least one sensor for measuring data indicating a deposition rate; and processing the data acquired during the deposition of the filament by a processing unit to identify patterns associated with extrusion irregularities, wherein the patterns are identified based on sudden peaks and / or valleys in the data.

[0109] According to one aspect, the present invention provides a computer program product configured to receive data from a measurement unit, wherein the computer program product is configured to identify patterns in the data associated with extrusion irregularities, wherein the patterns are identified based on sudden peaks and / or valleys in the data and sudden peaks and / or valleys in the data that have been compensated for.

[0110] According to one aspect, the present invention also provides the use of a system according to the above aspects of the invention for evaluating the quality of structures manufactured by extrusion.

[0111] Different types of extrusion additive manufacturing arrangements can be used, such as filament feed extrusion, screw extrusion or syringe extrusion of viscous dispersions or viscous pastes. Combinations of these technologies are also possible.

[0112] The additive manufacturing method of the present invention may also be referred to as 3D printing, 3DFD, fiber deposition, filament deposition, robotic casting, micro extrusion, etc., or a combination of two or more of these items.

[0113] In a syringe extruder, material is placed into a syringe, and the printer presses the plunger at a controlled rate to extrude filaments through a nozzle. For example, the syringe may be filled with a viscous material. In some examples, a heated sheath may be used to heat the syringe to melt the material (e.g., polymer granules) in situ before printing. Different types of syringe extrusion systems may exist. Pneumatic pressure may be applied to the plunger. Alternatively, the plunger may be pressed by mechanical displacement (e.g., via an electric motor). Mechanical displacement allows for more direct control of the volumetric extrusion rate, whereas in pneumatic printers, the extrusion rate may also depend on the interplay between the needle geometry, material viscosity, pneumatic pressure, and resistance from previously extruded filaments. Other alternative designs may also exist.

[0114] In a screw extruder, material is fed into a screw surrounded by a tightly fitted sleeve (called a barrel). As the screw rotates, the molten polymer is forced through a nozzle at the end of the barrel. The rate at which material is extruded from the nozzle depends on the screw rotation speed. Screw extruders can accommodate materials in paste form; however, polymer granules can also be used, for example.

[0115] It should be understood that any aspects, features, and options described in connection with this method are equally applicable to the system, the described computer program product, and the three-dimensional porous structure. It will also be apparent that any one or more of the foregoing aspects, features, and options can be combined. Attached Figure Description

[0116] The invention will be further illustrated based on exemplary embodiments shown in the accompanying drawings. Exemplary embodiments are given by way of non-limiting description. It should be noted that the drawings are merely illustrative representations of embodiments of the invention given by way of non-limiting example.

[0117] In the attached diagram: Figure 1 shows a schematic diagram of the extrusion process; Figure 2 shows a schematic diagram of an embodiment of the porous structure; Figure 3 A perspective view showing a schematic diagram of an embodiment of the porous structure; Figure 4 shows a schematic diagram of an embodiment of the porous structure; Figure 5 A schematic diagram of an embodiment of the nozzle is shown; Figure 6 A schematic diagram of an embodiment of the nozzle structure is shown; Figure 7 A schematic diagram of an embodiment of the nozzle is shown; Figure 8 shows a graph of the monitored values; Figure 9 A graph showing the monitored values ​​is provided. Figure 10 A graph showing the monitored values ​​is provided. Figure 11 A graph showing the monitored values ​​is provided. Figure 12 A graph showing the monitored values ​​is provided; and Figure 13 A schematic diagram of the method is shown. Detailed Implementation

[0118] Figure 1 illustrates a schematic diagram of the printing path during the extrusion process for fabricating a three-dimensional porous structure 1. The printing path illustrates how filaments of the porous structure are deposited on multiple layers. The method involves depositing interconnected filaments in a predetermined arrangement in multiple stacked layers. The filaments of the continuous layers are connected to each other to obtain a porous structure with interconnected pores. Furthermore, the filaments of the continuous layers are at an angle relative to each other.

[0119] In this example, filaments with one or more brittle regions are obtained by following a specific printing path. The predetermined arrangement of the interconnected filaments is configured to give the porous structure a desired porosity level.

[0120] During the extrusion process, nozzle 1 is scanned along the printing bed 3, which deposits the filaments, following the illustrated printing path 5. It should be understood that it is also contemplated that the printing bed 3 is moved, rather than nozzle 1 (kinematic reversal). Combinations may also exist. In an alternative example, nozzle 1 and printing bed 3 may be moved during at least a portion of the deposition process.

[0121] Figure 1a shows the printing path 5 of the first layer on the printing bed 3. Figure 1b shows the printing path 5 of two layers. Figure 1c shows the printing path 5 of the fourth layer, which is not yet complete. It should be understood that various printing path arrangements are possible in order to define one or more brittle regions in the porous structure to be manufactured.

[0122] By altering the deposition pattern, the local mechanical properties of the porous structure are locally changed. In this example, the printed porous structure has non-uniform filament-to-filament spacing.

[0123] If the nozzle malfunctions (clogging, excessive paste deposition, etc.), the structural integrity of the porous structure can be affected. For example, deposition irregularities can result from air voids within the build material deposited through the nozzle opening.

[0124] Pressure data can be collected during filament deposition, i.e., during the extrusion-based manufacturing of porous structures. The system can predict the occurrence of defects and / or deformities in porous structures by objectively quantifying the pressure values ​​during filament deposition. The measurement unit can be arranged to wirelessly transmit the pressure data to a processing unit, for example, located at a remote location. The remote location may include one or more processing units. Optionally, the measurement unit wirelessly transmits the pressure data to a server (e.g., in the cloud), which acts as the processing unit (for performing data analysis). Historical data can also be stored on a remote server accessible, for example, a mobile phone. It should be understood that other devices can also be used instead of mobile phones, such as computers, laptops, handheld devices, tablets, etc. A signal processing unit can also be integrated into the measurement unit. The processing unit can be configured to build or maintain a historical database. Knowledge related to previous and current deposition defects can be of significant value in preventing future deposition defects. Furthermore, it prevents deposition defects from being noticed too late.

[0125] The method of the present invention may include: measuring a pressure value by means of a first measuring unit, the first measuring unit being used to measure a first pressure value indicating the pressure applied to the build material in a build material reservoir; and measuring at least one second pressure value by means of at least one second measuring unit located at different locations. The method of the present invention further includes determining / calculating a difference between the first pressure value and at least one second pressure value, and adjusting extrusion parameters based on the difference.

[0126] Advantageously, this method can even better compensate for potential deposition irregularities. It should be understood that pressure values ​​can be measured at even more locations within the material reservoir, for example, using additional measuring units.

[0127] The processing unit can be arranged to collect pressure data over a total time interval during the deposition of the filaments. Alternatively, pressure data can be collected over an unrestricted time interval during deposition, for example, based on the total deposition time of the filaments.

[0128] The processing unit may be arranged to collect pressure values ​​determined by a first measuring unit (the first measuring unit is used to measure a first pressure value indicating the pressure applied to the building material in the building material reservoir) and at least one second pressure value determined by at least one second measuring unit located at different locations, to calculate the difference between the first pressure value and at least one second pressure value, and to adjust the extrusion parameters based on the difference.

[0129] The system is also able to adjust one or more printing parameters during the filament deposition process, preferably after the pressure value has been quantified, to compensate for the pressure value and minimize the occurrence of defects and / or deformities in the porous structure.

[0130] Figure 2 shows a schematic diagram of an embodiment of the porous structure 10. Figure 2a shows a cross-sectional side view, and Figure 2b shows a cross-sectional top view. The porous structure 10 can be obtained by an extrusion unit including a nozzle having a nozzle outlet and a build material reservoir. The build material reservoir is in fluid communication with the nozzle outlet. The extrusion unit can be used to deposit filaments 2 in a predetermined interconnected arrangement in a plurality of stacked layers 11 to form a porous structure 10 with interconnected pores 15.

[0131] The measuring unit may include one or more devices arranged to measure an amount indicating pressure or load applied to the build material in a build material reservoir at the nozzle for discharge of build material through the nozzle opening. Different types of devices or sensors may be used for this purpose. The measuring unit can be used for structural monitoring of extrusion quality during filament deposition. Advantageously, pressure values ​​can be monitored to determine structural integrity problems caused by deposition defects by processing the monitored data using a processing unit.

[0132] The processing unit can be configured to perform data analysis. The processing unit can load or receive one or more pressure value data from one or more sensors of the measuring unit. The processing unit can be configured to execute data analysis algorithms, wherein the results may optionally be provided to a reporting device (e.g., on a computer, laptop, smartphone, tablet, cloud, network, etc.).

[0133] The processing unit can also be configured to adjust one or more printing parameters during the filament deposition process, preferably after quantifying the pressure value, to objectively minimize the risk of defects and / or deformities in the porous structure.

[0134] Figure 3 A perspective view illustrating an embodiment of the porous structure 10 is shown. During the fabrication of the porous structure 10, a measuring unit can be used to monitor pressure values, which indicate the pressure applied to the build material in the build material reservoir of the nozzle during filament deposition. In this way, it can be ensured that the porous structure does not contain deposition defects. Therefore, when no deposition defects are identified during the fabrication of the porous structure 10, the quality or structural integrity of the porous structure can be ensured.

[0135] It should be understood that the pressure value provides an indication of the pressure in the build material reservoir of the nozzle. The pressure value can also be considered as a force value or extrusion force value, which can be viewed as the mechanical load applied to the porous structure to enable the discharge of build material (e.g., a paste) through the nozzle opening. Various sensors can be used to record the extrusion force / pressure applied to the build material. Additionally or alternatively, the flow rate of the build material discharged through the nozzle opening is monitored.

[0136] The processing unit can be configured to monitor one or more process parameters of the extrusion process (e.g., extrusion force, extrusion pressure, flow rate, etc.) to identify one or more deposition defects in the printed porous structure. Advantageously, through this invention, it becomes known how to form the porous structure 10, and even how to form the porous structure 10 from within. This insight can be obtained without the need for destructive methods, such as slicing the porous structure 10.

[0137] It should be understood that the porous structure 10 can be used in a variety of applications. Some exemplary applications are catalytic combustion of substances, environmental catalysis, heat exchangers, medical implants, etc. Advantageously, the production process of the porous structure can be monitored to analyze the porous structure formed during the process. In this way, the structural integrity suitable for a particular application can be better guaranteed.

[0138] Figure 4 shows a schematic cross-sectional side view of an embodiment of a porous structure 10, which has multiple layers 11 consisting of deposited filaments 2 stacked on top of each other. The filaments 2 have a filament diameter D and a filament-to-filament distance A. The layers may have a height H. This height may substantially correspond to the filament diameter D. However, it can also be varied. For example, the height H may be reduced at one or more brittle regions.

[0139] The building material can be extruded in the form of a first layer comprising multiple filaments 2. For example, the filaments 2 can be part of elongated threads of the deposited building material. In this example, the elongated threads are deposited continuously. However, the filaments can also be deposited discontinuously. Furthermore, one or more additional layers can be extruded, each additional layer stacked vertically on top of the previously extruded layer, and also including multiple filaments 2 angled relative to the previous layer. A predetermined pattern is provided to define the three-dimensional structure / object being manufactured.

[0140] The porous structure 10 has interconnected pores 15, thereby ensuring quality transfer for a wide range of applications. The geometry and arrangement of the filaments 2 affect the porosity and mechanical properties of the porous structure. The position and orientation of the filaments 2 in the filament arrangement (i.e., the layup pattern) obtained by deposition along the printing path can be adjusted according to the desired structural characteristics of the porous structure being manufactured. For example, the distance A (spacing) between filaments can be adjusted. The mechanical properties are affected by the relative orientation of the filaments 2 on multiple layers 11.

[0141] Monitoring and analyzing the 3D extrusion printing process is crucial for detecting one or more deposition errors during filament deposition. Deposition errors can affect structural parameters such as fiber thickness and interfiber spacing in the manufactured porous structure. In this way, the overall structural integrity of the porous structure can be compromised.

[0142] Pressure values ​​can be monitored during the deposition of filaments. The monitored pressure values ​​can be analyzed to detect one or more deposition irregularities in the formed porous structure by identifying irregular increases and / or decreases in pressure values ​​relative to the steady-state level reached during deposition. One or more identified deposition irregularities can then be correlated with one or more deposition defects 50 in the porous structure 10. Figure 4A and Figure 4B The porous structures depicted exhibit different deposition defects 50, each with varying degrees of severity. The severity can be estimated based on monitored pressure values ​​to determine its impact on the quality and / or structural integrity of the fabricated porous structure.

[0143] The measured pressure data can be used to analyze at least the magnitude of peaks in the pressure values ​​and correlate specific patterns (i.e., the variation patterns of pressure value over time) with the type of defects and / or disturbances in the manufactured porous structure. One or more pressure value distributions can be obtained from the pressure data. The system provides an accurate assessment that may be difficult to predict based on visual inspection. Visual inspection may not provide a simple way to accurately assess deposition defects.

[0144] The diameter of the extruded fiber and the distance between two adjacent fibers can be determined or estimated based on the monitored pressure value to determine whether one or more deposition defects exist in the formed porous structure.

[0145] Figure 5 A schematic cross-sectional side view of an embodiment of nozzle 1 is shown. The nozzle includes a nozzle opening 1a and a build material reservoir 1b. Nozzle 1 includes an actuation device 1c for applying force / pressure to the build material within the build material reservoir 1b. As a result of this load, build material can be discharged through the nozzle opening 1a. Nozzle 1 includes a measuring unit arranged to monitor pressure values ​​indicating the pressure applied to the build material in the build material reservoir 1b of nozzle 1 during the deposition of filaments 2. Different types of measuring units may be employed.

[0146] In this example, the measuring unit includes a load sensor positionable at the build material reservoir, configured to measure data indicating pressure within the build material reservoir, wherein the processing unit is configured to process the data provided by the load sensor. More specifically, the sensor is a load sensor including a transducer arranged to generate an electrical signal whose magnitude is proportional to the force being measured, wherein the load sensor is arranged to measure the force applied to discharge build material out of nozzle 1. For example, the load sensor may be arranged at the actuation device 1c. Advantageously, a simple design is obtained to provide an accurate indication of the pressure applied to the build material in the reservoir 1b of nozzle 1.

[0147] The pressure value can be determined using a highly sensitive force sensor. The measurement unit provides accurate feedback on the pressure / force applied during the deposition of filaments to create a porous structure.

[0148] Figure 6 A schematic cross-sectional side view of an embodiment of nozzle 1 is shown. Sensors, such as force or pressure transducers, can be arranged to measure the force / pressure applied to the build-up material during filament deposition. The force / pressure value sensor of the measuring unit can be detachable relative to the nozzle. Pressure sensors can also be integrated with the nozzle. The pressure value sensor (e.g., a load sensor) can be compact enough to avoid interfering with, for example, the normal movement or function of the nozzle.

[0149] In this example, the measuring unit further includes a flow sensor 51 configured to measure a flow value indicating the flow rate of the build-up material extruded through nozzle outlet 1a. The processing unit is configured to process the flow data to determine one or more flow irregularities, which are formed by irregular increases and / or decreases in flow rate relative to a steady-state flow rate level during deposition.

[0150] Different types of flow sensors 51 can be used. For example, flow measurement can be implemented based on thermal pulses. This technique is more suitable for use with highly viscous building materials. Alternatively, flow can be indicated by weight measurement. For example, weight can be measured as a function of time through recorded balance. Based on the mass recorded over a period of time and the determined mass density of the paste, the flow rate discharged from the nozzle opening can be identified. Alternatively, flow can be measured by a non-contact system, such as including at least one of a laser or a camera. For example, a profilometer that operates based on interferometry can be used. The dimensions of the extruded filament can be determined, and based on this, the volume and therefore the flow rate can be determined. It should be understood that other techniques may also be used.

[0151] Figure 7 A schematic cross-sectional side view of an embodiment of nozzle 1 is shown. In this example, the measuring unit further includes an imaging device 53 configured to image filaments deposited through the nozzle opening 1a of the nozzle. The imaging device may include at least one of a camera or a laser imaging device.

[0152] Figure 8 shows a graph 100 of the monitored values, indicating the pressure of the build material applied to the nozzle in the build material reservoir. The force used to build pressure in the build material reservoir to extrude the filaments through the nozzle opening is plotted over time. Therefore, the monitored force indicates the pressure value applied to the build material. Time-domain analysis of the pressure value data is possible. The processing unit is configured to process the monitored time-force / pressure values ​​to detect one or more deposition irregularities in the formed porous structure by identifying irregular increases 101a and / or decreases 101b of the pressure value relative to the steady-state level 103 reached during deposition. During an irregular increase, the pressure value (see force F) surges instantaneously and then returns to its steady-state level 103. During an irregular decrease, the pressure value (see force F) decreases instantaneously and then returns to its steady-state level 103. The processing unit is configured to correlate one or more identified deposition irregularities with one or more deposition defects in the porous structure 10. The processing unit is also configured to adjust deposition parameters to compensate for the irregular increases or decreases in the pressure value.

[0153] In this example, the steady-state level 103 is a range with an upper limit 105a and a lower limit 105b. Depositional irregularities can be identified at the moment when the pressure value suddenly exceeds the steady-state level range 103. Pressure values ​​may have positive and / or negative peaks falling within the steady-state level 103 without being identified as depositional irregularities, as well as positive and / or negative peaks exceeding the steady-state level 103 (see range or envelope) and being identified as depositional irregularities by the processing unit. The processing unit is also configured to adjust depositional parameters to prevent positive and / or negative peaks exceeding the steady-state level and to prevent depositional irregularities.

[0154] Steady-state level 103 can be a region where the pressure value remains stagnant over time. During such a steady-state phase, the pressure can remain relatively stable, staying near the baseline of the steady-state level.

[0155] The pressure value can remain substantially constant within a certain range or bandwidth. The upper and lower limits of this range can be located at +20% and -20% of the baseline of the steady-state level, more preferably at +10% and -10% of the steady-state level, and even more preferably at +5% and -5% of the baseline of the steady-state level.

[0156] It should be understood that the assessment of filamentous deposition may involve detecting and / or identifying deposition irregularities determined using pressure values ​​monitored during filamentous deposition. For example, structural weaknesses or other structural integrity conditions of porous structures may be identified.

[0157] A graph indicating pressure / force values ​​provides a visual indication of the irregular rise and / or fall of pressure values ​​relative to the steady-state level reached during deposition. However, analysis can also be performed numerically without a visual representation. It should be understood that pressure values ​​may deviate slightly but will still fall within the steady-state level (see range, band, or envelope).

[0158] This invention enables improved characterization of the manufactured porous structures by using process monitoring to indicate the value of the pressure or force applied to the build material in the nozzle to achieve filament deposition. Advantageously, the quality can even be checked or monitored during the printing of the porous structure.

[0159] Examples of deposition parameters that can be adjusted during printing to compensate for irregular rises or falls in pressure values ​​include, but are not limited to: adjusting (i.e., increasing or decreasing) the pressure applied to the printing material, for example, in the build material reservoir or nozzle, or at any location on the print material supply line, before the printing material leaves the nozzle; adjusting the viscosity of the printing material before it leaves the nozzle, for example, by heating or cooling the printing material, by adjusting the amount of solvent contained in the printing material, by supplying a release agent at any location on the reservoir, nozzle, or print material supply line; adjusting the flow rate of the printing material to subject it to vibration; adjusting the nozzle opening, etc. Adjustments can vary over time (e.g., instantaneous / temporary adjustment of extrusion parameters). To enable early compensation for irregular rises or falls in pressure values, the measurement unit may include a load sensor that can be positioned at the build material reservoir, between the build material reservoir and the nozzle, or at the nozzle.

[0160] Figure 9 A graph 100 showing the monitored values ​​indicates the pressure of the build material applied to the build material reservoir of the nozzle for discharge of build material through the nozzle opening. In this example, the force applied by an actuator to push the build material out of the build material reservoir is plotted over time. This force may represent, or at least indicate, a pressure value indicating the pressure applied to the build material reservoir of the nozzle during filament deposition.

[0161] The height and / or width of peaks / valleys in the monitored data can indicate the severity of depositional irregularities. Pressure values ​​that vary over time and / or location can be monitored. As a result, abrupt patterns of change leading to depositional defects (see fluctuations) can be correlated with specific locations within the porous structure.

[0162] In the illustrated graph 100, three time intervals, T1, T2, and T3, are identified, each with a different steady-state level 103. This could be, for example, the result of different depositional parameters. In the first time interval T1, the steady-state level is a substantially linear range. There are no force peaks / valleys deviating from the steady-state level 103 in the first time interval T1. In the second time interval T2, the steady-state level 103 is slightly inclined. There is a valley 101b that deviates from the steady-state level range 103. The processing unit is arranged to identify this peak as a depositional irregularity. In the third time interval T3, the steady-state level 103 extends almost horizontally. There are two peaks 101a that deviate from the steady-state level range 103. The processing unit is arranged to identify these peaks as depositional irregularities associated with depositional defects, and to adjust depositional parameters to counteract these peaks once they deviate from the steady-state level range 103. Furthermore, the processing unit can determine the severity of depositional defects based at least on the magnitude and / or shape of the irregular rise and / or fall of force relative to the steady-state level 103.

[0163] Figure 10 A graph 100 showing the monitored values ​​indicates the force (indicating pressure) applied to the build material reservoir in the nozzle to allow the filaments to be discharged through the nozzle opening. The graph shows the initialization time interval T0, during which the force stabilizes towards a steady-state level 103. The force values ​​indicating the pressure are monitored by the processing unit to identify local peaks 101a and / or valleys 101b. Peaks may have different characteristics (e.g., shape, peak amplitude, etc.), which can be further considered to determine the severity of deposition defects in the porous structure associated with these characteristics.

[0164] Due to nozzle clogging, the pressure can increase instantaneously or rapidly until sufficient pressure is obtained to expel the clogged build material from the nozzle. In the example shown, the nozzle clogged three times over a relatively long period. Due to the clogging, the build material could no longer flow normally (flow rate decreased), and the pressure or force used to expel the build material from the nozzle increased significantly and abruptly. As pressure built up, the nozzle opening cleared, and a large amount of build material flowed out of the nozzle all at once. The pressure stabilized again, and printing could continue, with the force / pressure value remaining at a steady-state level.

[0165] The processing unit can be configured to detect the locations of irregular rises and / or falls in pressure values, estimate the locations of weak points resulting from deposition defects, and determine or estimate the overall strength of the porous structure. In some examples, a model is used to determine the overall strength.

[0166] It should be understood that a spike or peak in the pressure / force value can be considered as a sharp rise (i.e., a sudden and rapid increase) followed by a sharp fall. This instantaneous and rapid increase in the pressure value, or the value indicating the pressure, can lead to irregularities in deposition. The opposite description also applies to the fall (see negative peak).

[0167] A smaller nozzle diameter can require a greater force F than a larger nozzle diameter. When build-up materials of the same viscosity are extruded through a smaller opening, a greater force is required to expel the build-up material from the nozzle opening. With a smaller nozzle diameter, the initial time to obtain force may also be longer. This initial time is measured from the moment pressure begins to build up (and thus the piston contacts the build-up material) until the pressure stabilizes. This can be due to the fact that the set flow rate for that diameter may also be smaller, thus allowing the spindle to rotate more slowly, and consequently requiring a longer time to reach the specified pressure. For a smaller nozzle diameter, the time and force required to stabilize the flow (see stabilization time T0) may be greater. The controller can be arranged to take this into account when performing the method according to the invention.

[0168] Figure 11 A graph 100 showing the monitored force values ​​indicates the pressure of the build material applied to the nozzle in the build material reservoir. Graph 100 represents a magnified portion of the peak 101a.

[0169] The force surges instantaneously and breaks through the steady-state level range 103, then returns to its value within the steady-state level range 103. This is identified by the processing unit as an irregular rise in force relative to the steady-state level range 103. One or more irregular rises and / or falls can be associated with deposition defects in the porous structure. Advantageously, the location of deposition defects can also be determined.

[0170] Figure 12 A graph 100 shows the monitored force values, indicating the pressure of the build material applied to the nozzle in the build material reservoir. The force has different steady-state levels at different time intervals. The flow rate of the build material discharged through the nozzle opening can be set by a controller. The applied force can vary to maintain a substantially constant flow rate. For example, a greater force / pressure may be required to push more build material out of the same opening area of ​​the nozzle. Furthermore, if filament deposition continues for a longer period, the load sensor may indicate different values. For example, the same flow rate may be obtained in region E as in region A. However, as the amount of build material in the reservoir decreases, the measured force may decrease slightly, which affects the frictional force applied to the reservoir walls during filament deposition. If less build material is present in the reservoir during filament deposition, the force forcing the paste through the reservoir may be smaller.

[0171] for Figure 12 In the example shown, the nozzle diameter is 400 micrometers, and regions A to E in graph 100 have the following set flow rates:

[0172] Figure 13 A schematic diagram of a method 1000 for fabricating a three-dimensional porous structure is shown. In a first step 1001, an extrusion unit is provided, the extrusion unit including a nozzle having a nozzle outlet and a build material reservoir in fluid communication with the nozzle outlet. In a second step 1002, filaments are deposited in a predetermined interconnected arrangement in a plurality of stacked layers by the extrusion unit to form a porous structure with interconnected pores. In a third step 1003, a pressure value is monitored by a measuring unit, the pressure value indicating the pressure applied to the build material in the build material reservoir of the nozzle during the deposition of the filaments. In a fourth step 1004, the monitored pressure value is processed by a processing unit to detect one or more deposition irregularities in the formed porous structure by identifying irregular rises and / or falls in the pressure value relative to a steady-state level reached during deposition. During an irregular rise, the pressure value surges instantaneously and then returns to its steady-state level. During an irregular fall, the pressure value decreases instantaneously and then returns to its steady-state level. Furthermore, the processing unit associates one or more identified depositional irregularities with one or more depositional defects in the porous structure.

[0173] The present invention provides a method for evaluating whether the structural condition of a manufactured porous structure is suitable for a specific function based on results obtained through a processing unit.

[0174] Advantageously, the monitored pressure data is used to detect and / or monitor deposition defects in porous structures. The measuring unit may include at least one load sensor that provides a measurement of the dynamic pressure applied to the build material in the build material reservoir during filament deposition. In the resulting pressure value distribution, a steady-state level may be reached during deposition. One or more positive peaks (see spikes) or negative peaks (see valleys) exceeding the steady-state level can be detected. The pressure value peaks are primarily a result of anomalies occurring during deposition. For example, spikes may occur when the nozzle opening is at least partially blocked. Furthermore, valleys may occur when air gaps pass through the nozzle opening. Using the system according to the invention, the source of such imbalances in the pressure values ​​can be accurately assessed. In this way, defects in porous structures can be detected or assessed. Furthermore, the fabrication of porous structures can be accelerated because if one or more detected defects are too severe, the process can be canceled and restarted from the cancellation point. Pressure values ​​can be monitored and effectively adjusted, for example, to compensate for identified pressure irregularities.

[0175] It should be understood that the method can be at least partially computerized. The processing unit may include at least one processor configured to receive one or more signals, including one or more pressure value data representing one or more loads or pressures applied to the building material during filament deposition to form a porous structure. The processing unit may include a data acquisition device configured to collect the one or more pressure value data from the received one or more signals.

[0176] Optionally, the measurement data is wirelessly transmitted to one or more remote devices including a processing unit. Optionally, the one or more remote devices are configured to perform further analysis of the measurement data.

[0177] The measurement unit may also include a signal output device for outputting measurement data. Optionally, the system is also configured to generate output data that includes an overview of the affected locations, defect types, and / or severity of defects in the porous structure. In this example, the system also includes a reporting unit.

[0178] Optionally, the system includes at least one display unit for reading out the pressure values ​​measured by the system. The display unit can be configured to display the analyzed pressure value data (e.g., detected events, fluctuations, or patterns). The system may also include a transmission device for transmitting measurement data and / or analysis data.

[0179] Optionally, the system includes a pressure value indicating unit, which includes a display device arranged to provide acoustic and / or tactile feedback, for example, via a speaker and / or piezoelectric element, upon detecting an irregular rise and / or fall in the pressure value relative to a steady-state level. It should be understood that such feedback can also be transmitted via a mobile device (e.g., a smartphone). One or more users may receive a notification. Other notification methods may also exist.

[0180] The system may include a storage unit configured to store the measured pressure data. For example, the storage unit may be housed in a preferably removable or detachable storage medium such as a memory card. The measurement data can also be taken out via a physical output device such as a network cable or USB cable. Alternatively, the measured data may be transmitted to the cloud via the Internet. The system may include a transmission device for wirelessly transmitting the measurement data to a storage server (e.g., the cloud) or computer for storage.

[0181] According to one aspect, the present invention provides a data carrier including instructions configured to perform the steps of the method according to the present invention when executed on a programmable device of a controller.

[0182] It should be understood that a trough can be considered as a momentary decrease in the level of quantity, followed by a return to its steady-state level. A trough may include a brief downward slope followed by an upward slope.

[0183] It should be understood that the steady-state level can be a band or range within which the pressure values ​​are expected to be normal during the deposition of filaments. Sudden anomalies in pressure values ​​can cause the pressure values ​​to exceed the range of the steady-state level, resulting in deposition irregularities, which can introduce defects into the formed porous structure.

[0184] The fabrication / printing process of the porous structure 10 can be based on extruding a viscous build-up material through fine needle-like prongs. For example, the build-up material can be a highly viscous paste. The structure can be built layer by layer by performing extrusion motions in three dimensions. One or more nozzles can be used to deposit filaments during the extrusion process. One important process parameter is the force applied to the build-up material (e.g., the paste) to discharge the build-up material from the nozzle opening. Additionally or alternatively, the flow rate of the build-up material propelled outside the nozzle opening can also be considered an important process parameter. Optionally, both parameters are monitored during fabrication using force / pressure sensors (e.g., load sensors) and flow meters. However, it is also envisioned that only one of the two parameters is used, such as only force / pressure sensors or only flow meters. These measurement units can be implemented in various ways. In some examples, one or more measurement units are integrated at or within the nozzle.

[0185] It should be understood that the method may include computer-implemented steps. All of the above steps may be computer-implemented steps. Embodiments may include a computer device, wherein the process is performed in the computer device. The invention also extends to computer programs suitable for practicing the invention, particularly computer programs on or in a carrier. The program may be in the form of source code or object code, or any other form suitable for implementing the process according to the invention. The carrier may be any entity or device capable of carrying the program. For example, the carrier may include a storage medium, such as a ROM, such as a semiconductor ROM or a hard disk. Furthermore, the carrier may be a transmissible carrier, such as an electrical or optical signal, that can be transmitted via cable or optical fiber, or wirelessly or otherwise (e.g., via the Internet or the cloud).

[0186] For example, some embodiments may be implemented using a machine or a tangible computer-readable medium or article that may store instructions or a set of instructions that, if executed by a machine, may cause the machine to perform the methods and / or operations according to the embodiments.

[0187] Various embodiments can be implemented using hardware components, software components, or a combination of both. Examples of hardware components may include processors, microprocessors, circuits, application-specific integrated circuits (ASICs), programmable logic devices (PLDs), digital signal processors (DSPs), field-programmable gate arrays (FPGAs), logic gates, registers, semiconductor devices, microchips, chipsets, etc. Examples of software may include software components, programs, applications, computer programs, application programs, system programs, machine programs, operating system software, mobile applications, middleware, firmware, software modules, routines, subroutines, functions, computer implementation methods, programs, software interfaces, application programming interfaces (APIs), methods, instruction sets, computational code, computer code, etc.

[0188] The invention is described herein with reference to specific examples of embodiments thereof. However, it will be apparent that various modifications, variations, substitutions, and alterations can be made therein without departing from the spirit of the invention. For the purpose of clarity and concise description, features are described herein as part of the same or different embodiments; however, alternative embodiments having combinations of all or some of the features described in these different embodiments are also contemplated, and these alternative embodiments should be understood to fall within the framework of the invention as set forth in the claims. Therefore, the specification, drawings, and examples should be regarded as illustrative rather than restrictive. The invention is intended to include all substitutions, modifications, and variations falling within the spirit and scope of the appended claims. Furthermore, many of the elements described are functional entities that can be implemented in any suitable combination and in any suitable location as discrete or distributed components or in combination with other components.

[0189] In the claims, any reference numerals placed between parentheses should not be construed as limiting the claims. The word 'comprising' does not exclude the presence of features or steps other than those listed in the claims. Furthermore, the words 'a' and 'an' should not be construed as limited to 'only one,' but are used to indicate 'at least one,' and do not exclude plurals. The mere fact that certain measures are recited in mutually different claims does not imply that a combination of these measures cannot be used advantageously.

Claims

1. A method for manufacturing a three-dimensional porous structure, the method comprising the following steps: An extrusion unit is provided, the extrusion unit including a nozzle having a nozzle outlet and a build material reservoir in fluid communication with the nozzle outlet, the build material comprising inorganic material particles dispersed in a binder and at least one solvent; The filaments of the building material are deposited in a predetermined interconnected arrangement in multiple stacked layers through the extrusion unit to form a three-dimensional porous structure with interconnected pores. The pressure value is monitored by a measuring unit, and the pressure value indicates the pressure applied to the build material in the build material reservoir during the extrusion of the build material through the nozzle to achieve the deposition of the filaments; as well as The monitored pressure values ​​are processed by a processing unit to detect one or more deposition irregularities by identifying irregular increases and / or decreases in the pressure values ​​relative to a steady-state level reached during extrusion, wherein during the irregular increase, the pressure values ​​surge instantaneously and then return to their steady-state level, wherein during the irregular decrease, the pressure values ​​decrease instantaneously and then return to their steady-state level, and wherein the processing unit is configured to adjust at least one extrusion parameter to compensate for the irregular increases and / or decreases in the pressure values.

2. The method according to claim 1, wherein, Adjusting extrusion parameters includes at least one of the following: Adjust the pressure of the build material applied to the build material reservoir and / or the pressure of the build material applied to the nozzle; Adjust the viscosity of the building material in the building material reservoir and / or the viscosity of the building material in the nozzle; Adjust the flow rate of the building material; Adjust the opening of the nozzle; Adjust the actuation of the extrusion screw in the nozzle; or Vibrations are provided to the building material.

3. The method according to claim 2, wherein, The viscosity of the building material in the building material reservoir is adjusted by at least one of the following methods: adjusting the temperature of the building material; adjusting the amount of solvent contained in the building material; or adding a release agent.

4. The method according to claim 1, 2 or 3, wherein, The measuring unit includes a load sensor that can be positioned at the build material reservoir, between the build material reservoir and the nozzle, and / or at the nozzle.

5. The method according to any one of claims 1 to 3, wherein, The measuring unit is configured to monitor pressure values ​​that indicate pressure applied to the building material at multiple locations.

6. The method according to any one of claims 1 to 3, wherein, The processing unit is configured to associate one or more identified deposition irregularities with one or more deposition defects in the porous structure, wherein the severity of the deposition defect is determined based on the magnitude and / or shape of the irregular rise and / or fall of the pressure value relative to a steady-state level reached during deposition.

7. The method according to any one of claims 1 to 3, wherein, The processing unit is configured to determine the location of the identified deposition defects in the porous structure based on the position of the nozzle in the printing path when the deposition irregularity is detected.

8. The method according to claim 6, wherein, The processing unit is configured to determine one or more defect regions in the fabricated porous structure based on the location of one or more identified deposition defects in the porous structure.

9. The method according to claim 8, wherein, The processing unit is configured to estimate the impact of one or more defect regions on the structural integrity of the porous structure based on at least one of the location and severity of the deposited defects at the defect regions, wherein the processing unit is configured to determine or estimate whether the printed porous structure meets the target properties based on the estimate of the impact of the one or more weak regions on the structural integrity of the porous structure.

10. The method according to claim 9, wherein, The processing unit employs a computational model to determine or estimate the impact of the one or more defect regions on the structural integrity of the porous structure, wherein, at the location of one or more detected deposition defects, the filaments are modeled using the diameter of the corresponding detected irregular rise or fall based on the pressure value.

11. The method according to any one of claims 1 to 3, wherein, If it is identified that one or more deposition defects in the porous structure are caused by one or more deposition irregularities, then the manufacturing of the porous structure is cancelled early.

12. The method according to claim 9 or 10, wherein, During the deposition of the filaments to create the porous structure, the impact of the one or more weak regions is estimated, wherein the manufacturing process is cancelled early based on the estimate of the impact.

13. The method according to claim 4, wherein, The load sensor includes a transducer arranged to generate an electrical signal whose magnitude is proportional to the force being measured, wherein the load sensor is arranged to measure the force applied to discharge the building material outside the nozzle.

14. The method according to any one of claims 1 to 3, wherein, The measuring unit further includes a flow sensor configured to measure a flow value indicating the flow rate of the build material extruded through the nozzle outlet, wherein the processing unit is configured to process the flow data to determine one or more flow irregularities formed by irregular increases and / or decreases in the flow rate relative to a steady-state flow rate level during deposition.

15. The method according to any one of claims 1 to 3, wherein, The pressure value is determined by a first measuring unit and a second measuring unit, which are located at different positions. The first measuring unit is configured to measure a first pressure value indicating the pressure applied to the building material in the building material reservoir. The second measuring unit is configured to measure at least one second pressure value. The method further includes determining a difference between the first pressure value and at least one second pressure value, and adjusting extrusion parameters based on the determined difference.

16. The method according to any one of claims 1 to 3, wherein, The steady-state level has a baseline envelope that forms segments with upper and lower limits, wherein when the pressure value exceeds the baseline envelope of the steady-state level, an irregular rise and / or fall of the pressure value relative to the steady-state level is identified.

17. An additive manufacturing system for fabricating three-dimensional porous structures, the system comprising: An extrusion unit includes a nozzle having a nozzle outlet and a build material reservoir in fluid communication with the nozzle outlet, the build material comprising inorganic material particles dispersed in a binder and at least one solvent; An extrusion unit configured to deposit filaments of the building material in a predetermined interconnected arrangement in a plurality of stacked layers to form a three-dimensional porous structure with interconnected pores; A measuring unit configured to monitor a pressure value indicating the pressure applied to the build material in the build material reservoir during the extrusion of the build material through the nozzle to achieve the deposition of the filaments; as well as A processing unit configured to process monitored pressure values ​​to detect one or more deposition irregularities by identifying irregular increases and / or decreases in the pressure values ​​relative to a steady-state level reached during extrusion, wherein during the irregular increase, the pressure value surges instantaneously and then returns to its steady-state level, wherein during the irregular decrease, the pressure value drops instantaneously and then returns to its steady-state level, and wherein the processing unit is configured to adjust at least one extrusion parameter to compensate for the irregular increases and / or decreases in the pressure values.

18. A computer program product configured to perform the steps of the method according to any one of claims 1 to 16 when run on a controller.

Images