System and method for more integrating interlayer bonding in additive manufacturing

Abstract

To provide systems and methods for more integrated layer-to-layer bonding in additive manufacturing.SOLUTION: An additive manufacturing apparatus includes an extruder configured to receive a thermoplastic material and an applicator assembly located downstream of the extruder, the applicator assembly including nozzles for depositing the thermoplastic material as multiple layers. The additive manufacturing apparatus includes a temperature sensor configured to detect a temperature of at least a portion of the deposited layers, a positioning assembly configured to vary an angular position of the temperature sensor, and a controller.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Aspects of the disclosure of the present invention generally relate to apparatus and methods for manufacturing components. In some examples, aspects of the disclosure of the present invention relate to apparatus and methods for manufacturing components (e.g., patterns, molds, and similar products, etc.) using additive manufacturing techniques or apparatus.

Background Art

[0002] To create net-shaped or near-net-shaped (NNS) objects, additive manufacturing techniques and processes generally involve stacking one or more materials, as opposed to subtractive manufacturing methods. Although "additive manufacturing" is an industrial and standard term (ASTM F2792), additive manufacturing encompasses various manufacturing and prototyping techniques known by various names, including freeform fabrication, 3D printing, rapid prototyping / tooling, etc. Recent 3D printers for additive manufacturing include large-scale 3D printers for manufacturing very large parts, molds, patterns, etc. These items can be made from fiber-reinforced thermoplastic materials. For example, a method for manufacturing these items utilizes a polymer extruder that generates beads of molten thermoplastic material that are added to the part to produce one layer at a time. These layers are modified and flattened into wide beads using devices such as a press plate or rollers during the lamination process. To effectively use this method, the previous layer needs to be cooled and cured to an amount sufficient to support the new layer and withstand the forces generated by pressing rollers, tampers, etc., and also maintain sufficient heat to remelt and fully fuse with the new layer being printed. In some processes, including this method referred to as 3D printing or additive manufacturing, the part is made slightly larger than required, and after the part has cooled and hardened, the part is machined to its final dimensions and shape.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Thermoplastic materials used in 3D printing processes, including large-scale printers, soften when heated above their melting points and harden again when cooled. The 3D printing of these materials may require fusing layer to layer to form a structure without solid voids. The quality of the resulting structure is generally determined by the integrity of the bonds between the printed layers. If the layers are fully fused to each other, the resulting structure exhibits the same physical strength and mechanical properties as the polymer located beneath the printed layers. However, if the bond between multiple layers is incomplete, the final physical strength of the printed structure may be determined by the bond strength between the layers. Thus, when the bond between layers is relatively weak, the resulting part itself will have relatively low physical strength.

[0004] At least some applications of components that are additively manufactured on a large scale, such as industrial assembly jigs or casting patterns, do not require perfect interlayer bonding, as even imperfectly bonded parts that do not meet ideal interlayer bonding have sufficient strength for the intended applications. However, there are many components that may be produced using additive manufacturing, such as aircraft components, in which case perfect or nearly perfect bonding between layers is desired and required.

[0005] Generally, each polymer has a temperature range for the previously printed layer to produce an acceptable interlayer bond with the newly printed layer. When a layer is printed, the layer begins to cool. The cooling rate depends on several factors, such factors including the polymer itself, the temperature of the polymer when printing, the temperature of the environment in which the part is printed, and the physical shape of the component being printed. After a period of time that varies based on these factors, the printed layer is cooled to a temperature within the ideal range for printing the next layer. Often, the amount of time to cool the layer to the required temperature range tends to be constant for a particular polymer. Some systems adjust the printing speed when the geometry of the part changes to print each layer in the same amount of time. This is applied when it is desirable to cool each layer over a similar amount of time regardless of the shape or size of the part being printed. However, fluctuations in the geometry of the part can affect the cooling rate or cause variations in the temperature of the layer when cooled over a particular amount of time. Since there is a temperature range that produces an acceptable bond, generally, these effects do not cause the temperature of the layer to be outside the temperature range used.

[0006] In some devices, this temperature range is monitored using a thermography camera. This enables the operator to visually monitor the overall temperature of the part while printing the part. In at least some of these devices, the display of the thermography camera is adjusted so that the surface is displayed in a distinct color when the surface is within the desired temperature range, thereby facilitating the analysis of and maintenance of the proper temperature.

[0007] While there is a temperature range that produces generally acceptable interlayer bonding, an important factor in achieving ideal interlayer bonding is the temperature of the previously printed layer at the exact time the new layer is deposited. For each polymer, there is an ideal temperature or relatively narrow temperature range that produces the best interlayer bonding. While the methods described above are acceptable for some applications, they may not be suitable for other applications because the layer cannot be steadily printed and deposited when the underlying layer is at the ideal temperature.

Means for Solving the Problem

[0008] Aspects of the disclosure of the present invention relate in particular to methods and apparatus for manufacturing components by additive manufacturing techniques. Each of the plurality of aspects disclosed in the specification may include one or more features described in relation to any other aspect disclosed in the specification. In particular, exemplary aspects of the disclosure of the present invention include tools useful for facilitating control of the printing temperature during the printing process, such tools measuring, for example, the temperature of the bead of the previously deposited material and adjusting the rate at which the material is deposited based on the measured temperature.

[0009] The aspects described herein are directed to a rotation mechanism and software system that control a drive mechanism, such as a servo motor, to rotate a pressing roller around the printing nozzle of an additive manufacturing apparatus. By this mechanism, the pressing roller is preferably rotated so that at each point in time during the printing process, the pressing roller is maintained in a position behind the direction of movement of the printing nozzle and perpendicular to such direction of movement.

[0010] At least some of the forms described herein include a temperature sensor attached to a mechanism for rotating a pressure roller. This temperature sensor is attached at a position in front of the print nozzle and above the previously printed print bead, and otherwise may be fixed. The temperature sensor at this position may be configured to read or detect the temperature of the previously printed layer immediately before depositing the next layer. This mechanism and its associated control components reduce cost and complexity in at least some forms.

[0011] The temperature sensor may be directed towards the previously deposited bead to measure the temperature of the previously deposited bead at the moment immediately before the printing function that deposits a new bead of material on top of the previously deposited bead occurs. When printing some parts, the temperature sensor may be directed to face the free air immediately adjacent to the print nozzle or otherwise detect the temperature of such free air before the print nozzle reaches a sharp corner, when it encounters a sharp corner. Once the nozzle begins to move in a new direction, the rotation mechanism that positions the pressure roller and the temperature sensor quickly realigns with the new direction of the bead, thereby enabling the temperature sensor to detect the temperature of the previously deposited bead again. Since the temperature difference of the free air with respect to the previously printed bead may be relatively large, appropriate software may be able to ignore or discard temperature readings that are not aligned with the previously printed bead.

[0012] The systems and methods described herein provide the ability to read the temperature of previously printed beads with relatively high accuracy just before new beads are printed on top of the previously printed beads. Further, the temperature sensor provides a continuous data stream (e.g., real-time or near real-time temperature data) or other information indicating the temperature of the entire area of each printed layer. This data stream or a portion of the information contained in the data stream is used in one or more ways to improve the quality of the printing process. For example, the average temperature of each layer (e.g., the overall average temperature of one layer) is accurately determined and used to automatically adjust the timing of layer printing. This timing adjustment includes, for example, increasing or decreasing the movement speed of a nozzle or other mechanism for depositing the material. Thereby, the material can be deposited on top of the previously deposited layer while the previously deposited layer has a temperature at or near a predetermined desired temperature, or while having a temperature within or near a predetermined desired temperature range.

[0013] In one aspect, a stereolithography apparatus may include an extruder configured to receive a thermoplastic material and an applicator assembly located downstream of the extruder, the applicator assembly including a nozzle for depositing the thermoplastic material as a plurality of layers. The stereolithography apparatus may include a temperature sensor configured to detect the temperature of at least a portion of the deposited layer and a positioning assembly configured to vary the angular position of the temperature sensor. Further, the stereolithography apparatus may include a controller configured to receive a temperature signal from the temperature sensor and compare the current detected temperature with the previous detected temperature. The controller may further be configured to change the movement speed of the applicator assembly when the current detected temperature is lower than the previous detected temperature by a first temperature difference, and to ignore a second temperature signal when a second temperature is lower than a second previous detected temperature by a second temperature difference greater than the first temperature difference.

[0014] In another aspect, the additive manufacturing system may include an additive manufacturing apparatus. The additive manufacturing apparatus may include an extruder configured to receive a material, an applicator assembly positioned downstream of the extruder, and a temperature sensor configured to generate a temperature signal indicative of the temperature of at least a portion of a first layer deposited while moving the applicator assembly. The additive manufacturing system may include a controller, and the controller may be configured to receive the temperature signal from the temperature sensor and vary the moving speed of the applicator assembly based on the temperature signal.

[0015] In yet another aspect, the additive manufacturing method may include heating a thermoplastic material with an extruder, supplying the heated thermoplastic material to an applicator assembly, and depositing the heated thermoplastic material on a surface below the applicator assembly to form a first layer. The method may also include detecting, with a temperature sensor while moving the temperature sensor, the temperature of at least a portion of the first layer, increasing or decreasing the moving speed of the applicator assembly based on the detected temperature, and depositing the heated thermoplastic material on the first layer to form a second layer.

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary aspects of the disclosure of the present invention and serve to explain the principles of the disclosure of the present invention together with the specification.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0018] The disclosure of the present invention is particularly directed to methods and apparatuses for manufacturing a number of components using additive techniques. Specifically, the methods and apparatuses described herein include tools used to assist in achieving a desired or ideal printing temperature during an additive manufacturing process such as printing.

[0019] Referring to FIG. 1, the additive manufacturing apparatus 1 (e.g., a CNC machine) is preferably part of an additive manufacturing system that includes a control system or controller 2, and the control system or controller 2 is configured to generate commands to control the CNC machine 1 to perform each of the functions described herein. The additive manufacturing apparatus 1 includes a bed 20 fixed between a pair of laterally spaced sidewalls 21, 22. The additive manufacturing apparatus 1 also includes a printing gantry 23 supported on the pair of sidewalls 21, 22, a carriage 24 attached to the printing gantry 23, a carrier 25 attached to the carriage 24, an extruder 61, and an applicator assembly, i.e., an applicator head 43, attached to the carrier 25. A horizontal work table 27 includes a support surface and is disposed to extend in the X-Y plane and is supported above the bed 20 between the pair of sidewalls 21, 22. The printing gantry 23 is disposed along the Y-axis and is supported by the pair of sidewalls 21, 22 at both ends of the printing gantry 23. The printing gantry 23 is fixed to a pair of guide rails 28, 29 provided at the upper ends of the pair of sidewalls 21, 22. The printing gantry 23 is movable along the X-axis and the pair of guide rails 28, 29 by a pair of servo motors, and such servo motors are attached to the printing gantry 23 and operatively coupled to tracks provided on the pair of sidewalls 21, 22 fixed to the bed 20. The carriage 24 is supported by the printing gantry 23 and has a support member 30 movably attached to one or more guide rails (e.g., guide rails 31, 32, 33) fixed to the printing gantry 23. The carriage 24 is movable along the Y-axis by sliding on one or more guide rails (e.g., guide rails 31, 32, 33). This sliding movement is caused by the operation of a servo motor, and such servo motor is attached to the printing gantry 23 and operatively coupled to the support member 30. The carrier 25 is attached to a set of guide rails 34, 35 that are spaced apart and extend in the vertical direction.The guide rails 34, 35 are supported by the carriage 24 to move the carrier 25 and the components coupled to the carrier 25 along the Z-axis with respect to the carriage 24. The carrier 25 is movable along the z-axis by a servo motor which is attached to the carriage 24 and operably coupled to the carrier 25.

[0020] As shown in FIG. 2, the extruder 61 is attached to the carrier 25 on a set of guide rails 34, 35 and bearings so as to be linearly movable with respect to the carrier 25. The servo motor 38 drives the extruder 61 via a gear box 39 attached to the moving housing 37. The extruder 61 receives the thermoplastic pellets at the supply housing 40. This material is fed to the extruder screw of the extruder 61 which transfers the material through the barrel 42 and is melted by the friction of the screw and by the heater 41. The extruder 61 causes the melted thermoplastic material to flow into a positive displacement melt pump or gear pump 62.

[0021] As shown in FIG. 3, a gear pump 62 is mounted so as to be fixed to the bottom of the carrier 25. The gear pump 62 is driven by a servo motor 63 via a gear box 64. The gear pump 62 receives molten plastic from the extruder 61 (FIG. 2) and supplies a thermoplastic material accurately metered for printing parts to the nozzle 51 at a predetermined flow rate. The applicator head 43 is mounted below the gear pump 62 so as to be located downstream of the extruder 61 and the gear pump 62 for receiving the thermoplastic material from the extruder 61 and the gear pump 62. Also, a bead forming roller 59 is mounted on the applicator head 43 and below the gear pump 62. The bead forming roller 59 is rotatably mounted on the carrier bracket 47 so as to constitute a mechanism for flattening and equalizing a fairly large bead of a fluid material (e.g., molten thermoplastic) extruded from a fairly large nozzle 51. The carrier bracket 47 is preferably moved in the rotational direction by a servo motor 60 via a pulley or sprocket 56, and the pulley or sprocket 56 is connected to the servo motor 60 by a configuration of a belt or chain 65. The pulley or sprocket 56 is preferably a plate-shaped rotating member configured to position the sensor 49 and the roller 59 at different angular positions and rotate the sensor 49 and the roller 59 around the nozzle 51.

[0022] The additive manufacturing apparatus 1 and the controller 2 may utilize the above-described rotation mechanism or positioning assembly (e.g., the servo motor 60, the belt or chain 65, and the sprocket 56) to correct the position of the roller 59. In particular, the controller 2 is programmed in software to drive a system including the servo motor 60 to rotate the pressing roller 59 relative to the printing nozzle 51. In particular, the pressing roller 59 may be rotated (e.g., in response to a command from the controller 2) so that it is always positioned behind the moving direction of the printing nozzle 51 and perpendicular to such a moving direction.

[0023] As shown in FIGS. 4 and 5, the temperature sensor 49 is attached to the bottom of the applicator 43 (e.g., the bottom surface of the sprocket 56) for angular positioning by the operation of the above-described positioning assembly (e.g., the servo motor 60, the belt or chain 65, the sprocket 56), in particular, by the rotation of the sprocket 56. The temperature sensor 49 extends into the inner hub 76 and is fixed in a block 48 protruding from the bottom surface of the applicator head 43. This position is preferably in front of the print nozzle 51 with respect to the direction in which the print nozzle 51 moves when depositing the material. The block 48 preferably houses the temperature sensor 49 such that the temperature sensor 49 is directed to face the printed bead deposited previously. In the exemplary form, the temperature sensor 49 is inclined towards the previously printed bead (e.g., at an angle between about 15 degrees and about 60 degrees from the vertical direction). If desired, the temperature sensor 49 may be directed downward so as to be substantially aligned with the vertical direction.

[0024] Referring to FIG. 5, the applicator head 43 includes a housing 46, which has a rotary joint fixed therein. The rotary joint includes coolant joints 67, 68 (e.g., barb joints), and the coolant joints 67, 68 are in fluid communication with a coolant passage 70, which surrounds the inner hub 76 of the rotary joint and runs once through the interior of the outer housing 75 of the rotary joint. The coolant passage 70 may extend through a quick-connect fitting 72 to supply coolant to the interior of the shaft 73 of the pressure roller 59. A pulley or sprocket 56 may be machined onto the inner hub 76 of the rotary joint. The inner hub 76 has an opening with a diameter sized such that the heated print nozzle 51 can pass through the inner hub 76. The inner hub 76 is rotated on a set of bearings 54 housed in the outer housing 75 of the rotary joint. Both the pressure roller assembly and the temperature sensor 49 are attached to the inner hub 76 of the rotary joint, and as a result, both the pressure roller 59 and the temperature sensor 49 rotate relative to the print nozzle 51. For example, the temperature sensor 49 and the pressure roller 59 are positioned on opposite sides of the nozzle 51. With this positioning, the temperature sensor 49 may be configured to read the temperature of the previously printed layer 53 immediately prior to depositing the next layer. In particular, the temperature sensor 49 may detect the temperature of the previously printed layer 53 using an exemplary sensing beam 50 (e.g., laser light, infrared light). If desired, the temperature sensor 49 may be configured as an optical system. Using the temperature sensor 49 and / or the controller 2 to control the apparatus 1 based on the temperature of the deposited material may reduce the cost and complexity of the system, as will be described later.

[0025] In an exemplary form, the temperature sensor 49 is powered by a battery (e.g., a battery within the temperature sensor 49 and / or a battery positioned within the applicator head 43). Additionally or alternatively, power may be supplied to the temperature sensor 49 by an external power source (e.g., the controller 2, or an independent power source separate from the device 1 and the controller 2) outside the temperature sensor 49. Information indicating the temperature detected by the temperature sensor 49 is preferably provided to an analysis system (e.g., the controller 2) via a wireless connection according to an appropriate standard such as a radio frequency (e.g., RF, BLUETOOTH®, Wi-Fi, mobile phone, near-field wireless communication, etc.). In some aspects, it may be convenient to supply the temperature data continuously or substantially continuously (e.g., as a data stream).

[0026] In an exemplary form, the temperature sensor 49 may transmit data and / or receive power via a wired signal transmission mechanism. For example, as shown in FIG. 5, the applicator head 43 includes a rotary slip ring assembly 52. The slip ring assembly 52 may receive a signal and / or power cable extending from the temperature sensor 49 to supply power to the sensor and transmit temperature data to a suitable recording and processing device such as the controller 2. The slip ring assembly 52 enables unrestricted rotation of the temperature sensor 49 by a guiding cable from the rotating part of the applicator head including the sensor 49 to the non-rotating part of the applicator head 43 (e.g., the outer housing 75 and the upper surface of the applicator head 43).

[0027] FIG. 6 is a flowchart of an exemplary additive manufacturing method according to an aspect of the disclosure of the present invention. As shown in FIG. 6, in step 81, the temperature sensor 49 detects the temperature of the previously deposited bead 53, and a new bead of the material is deposited by the nozzle 51 on this bead 53. However, when the temperature sensor 49 encounters a sharp corner (for example, when depositing the material for a layer located at or near the edge of the part), it may detect the temperature at a position outside the deposited material. For example, the temperature sensor 49 may detect the temperature of the work table 27, the temperature of the air adjacent to the part, etc. This temperature is much lower than the temperature of the bead of the previously deposited material. The temperature sensor 49 generates a signal (for example, data or information) indicating the detected temperature. This signal may be received by a control system such as the controller 2 or by an additional control system external to the controller 2.

[0028] Step 82 includes determining whether the temperature detected in step 81 represents the actual temperature of the previously deposited part or, instead, represents the temperature outside the bead, layer, and / or part. This may include using the controller 2 to determine whether the detected temperature is within a predetermined maximum range of previous data. For example, the controller 2 determines whether the detected temperature is lower than the previous detected temperature by a predetermined temperature difference (e.g., 50, 40, 30, 20, or 10 °C or more than that temperature difference). In addition to or as an alternative to this, step 82 may include comparing the detected temperature with a predetermined minimum expected temperature value associated with the bead of the material (e.g., the lowest temperature expected to be encountered during printing, such as 37, 50, or 90 °C, etc.) and determining whether the detected temperature is higher than the minimum expected temperature value. The temperature differences and minimum expected temperature values described above are examples and may vary significantly depending on the type of material being deposited and the amount of temperature change that can occur without adversely affecting the interlayer bond. These values may be predefined and stored in the controller 2 based on a material qualification process and may be monitored by the controller 2 during operation of the apparatus 1. In at least some forms, the predefined temperature difference and / or minimum expected temperature value may change over time. For example, the controller 2 is configured to set and / or change a predefined temperature difference, minimum expected temperature value, or both based on the material being deposited, ambient temperature, desired deposition temperature, melting point of the material being deposited, etc. The predefined temperature difference, minimum expected temperature value, or both may be set by the user by interacting with the controller 2 (e.g., by directly setting one or both of these values, by entering the type of material supplied to the apparatus 1).

[0029] When the determination in step 82 is negative, the controller 2 determines that the detected temperature does not represent the temperature of the deposited material (e.g., the detected temperature exceeds a predetermined temperature difference, is lower than the lowest expected temperature value, or both). When this occurs, step 83 includes ignoring the data that the controller 2 received in step 81. The method then returns to step 81 to resume the process of sampling the temperature data.

[0030] When the determination in step 82 is positive, the detected temperature indicates the actual temperature of the bead of the material previously deposited. This occurs, for example, when the nozzle 51 follows a path without sharp turns and when the nozzle 51 begins to move in a new direction following a sharp curve after the rotation mechanism realigns the pressing roller 59 and the temperature sensor 49 with the new direction of the bead 53. Step 84 includes analyzing the temperature data to determine whether the speed of the operation of the apparatus 1 should be adjusted (e.g., by increasing or decreasing the operating speed of the nozzle 51).

[0031] Step 85 includes determining whether the temperature data is within a predetermined minimum range of a data set (e.g., one or more previous detected temperatures). Step 85 includes determining whether the detected temperature is lower than one or more previous detected temperatures and is separated from one or more previous detected temperatures by a predetermined amount or more. When the determination in step 85 is positive (when the detected temperature is separated from one or more previous temperatures by only an allowable amount), the additive manufacturing apparatus 1 maintains the speed at a constant or nearly constant value. The method then returns to step 86.

[0032] When the determination in step 85 is negative (when the detected temperature is separated from the previous detected temperature of 1 or 2 or more by an unacceptable amount), the method proceeds to step 87. Step 87 includes determining whether the detected temperature in the data received from the temperature sensor 49 is lower or higher than a predetermined set point. This set point (for example, the temperature data set point) may be the predetermined desired temperature of the previously deposited bead, or it may be the predetermined desired temperature range. The predetermined set point may be based on the material to be deposited, or it may be based on the characteristics (for example, melting point) of the material to be deposited. In some aspects, the predetermined set point may be input by the user.

[0033] When the detected temperature is greater than, i.e., higher than, the temperature data set point (for example, when it is greater than the maximum set point temperature), step 88 is executed. In step 88, the controller 2 decreases the speed of the additive manufacturing apparatus 1 (for example, one or more of the moving speeds of the nozzle 51 and the applicator head 43, the operating speed of the extruder 61, and the operating speed of the gear pump 62) by an appropriate amount. In some aspects, the amount by which the speed is decreased may be based on the difference between the detected temperature and the set point such that the decrease in speed increases as the difference between the detected temperature and the set point increases. The method then returns to step 81 and continues to sample the temperature data.

[0034] When the detected temperature is less than, i.e., lower than, the predetermined set point (for example, when it is less than the minimum set point temperature), step 89 is executed. In step 89, the controller 2 increases the speed of the additive manufacturing apparatus 1 by an appropriate amount and returns to sampling the data of step 89. In some aspects, the amount by which the speed is increased may be based on the difference between the detected temperature and the set point such that the increase in speed increases as the difference between the detected temperature and the set point increases.

[0035] In some aspects, the difference between the temperature of the air and the temperature of the previously printed bead can be large, and when the temperature sensor 49 is not aligned with the previously printed bead, step 82 can be reliably executed by appropriate software for ignoring the temperature data. Additionally, the controller 2 may be provided with appropriate programming (e.g., software) for reliably controlling the speed of the additive manufacturing apparatus 1 such that a new layer is printed on top of the previous layer at an appropriate time and temperature.

[0036] Also, to identify each location where the temperature sensor 49 is not directed at the previously printed bead, appropriate software can be utilized to analyze the geometric shape of the bead associated with the detected temperature and the rotational direction position of the assembly coupled with the temperature sensor 49 (e.g., by analyzing the path of the applicator head 43 to identify sharp turns). This additional analysis is executed instead of or in addition to step 82 of the method described above, and by this additional analysis, accurate temperature readings can be taken while reliably ignoring data points that do not indicate the actual temperature of the deposited material. When the analysis of the geometric shape of the part is executed as step 82 or as part of step 82, the remainder of the method is executed as described above.

[0037] The systems and methods described herein provide, in at least some embodiments, the ability to accurately detect and identify the temperature of a previously printed bead immediately prior to a new bead of material being printed on top of the previously deposited bead. At least some aspects provide a continuous data stream that accurately reflects the overall temperature of each printed layer or the overall temperature of a portion of each printed layer.

[0038] In at least some embodiments, data streams or other forms of temperature measurements as described herein may be used to improve the quality of the printing process. For example, while discarding information that does not indicate the actual temperature of the deposited material, the instantaneous temperature and / or average temperature of each layer can be accurately determined to automatically adjust the timing of the printing layer. This can result in a printing layer that is closer to the ideal temperature when receiving a new bead than existing methods. In addition or alternatively, the use of a prediction algorithm using temperature data (e.g., an ongoing data stream) may adjust the printing speed within one layer as described above with respect to FIG. 6. This performance is beneficial, for example, to researchers using the additive manufacturing apparatus 1 and can improve the printing process. As another example, the printing temperature data described herein may form the basis of a quality assurance procedure to verify the integrity of manufactured parts, such as parts intended for use in critical applications. By measuring the printing temperature at all points for each layer of the part, it is possible to have a high level of certainty that there are no defects in the interlayer bonding in the part.

[0039] From the detailed description above, it is clear that there are many variations, adaptations, and modifications of the disclosure of the present invention that fall within the scope of those skilled in the art related to the technology of the disclosure of the present invention. However, it is intended that all such variations that do not depart from the spirit of the disclosure of the present invention be considered within the scope of the disclosure of the present invention as limited by the claims.

Description of the Reference Numerals

[0040] 1 Additive manufacturing apparatus 2 Controller 43 Applicator head (applicator assembly) 49 Temperature sensor 51 Nozzle 56 Pulley or sprocket 59 Pressing roller 61 Extruder 63 Servo motor

Claims

1. A stereolithography apparatus comprising: An extruder configured to receive a thermoplastic material; An applicator assembly located downstream of the extruder, the applicator assembly including a nozzle for depositing the thermoplastic material as a plurality of layers; Further comprising a temperature sensor configured to detect the temperature of at least a portion of the deposited layer; A positioning assembly configured to vary the angular position of the temperature sensor; And a controller, The controller is configured to receive a temperature signal from the temperature sensor and determine whether the detected temperature indicates the actual temperature of at least a portion of the deposited layer. When the detected temperature indicates the actual temperature of at least a portion of the deposited layer, the controller adjusts the moving speed of the applicator assembly based on the detected temperature, and when the detected temperature does not indicate the actual temperature of at least a portion of the deposited layer, the controller is configured to ignore the detected temperature. A stereolithography apparatus.

2. The stereolithography apparatus according to claim 1, wherein the positioning assembly is configured to rotate the temperature sensor around the nozzle.

3. The stereolithography apparatus according to claim 1 or 2, wherein the temperature sensor is fixed to the bottom surface of the applicator assembly.

4. The stereolithography apparatus according to any one of claims 1 to 3, wherein the temperature sensor is inclined toward a position adjacent to the nozzle.

5. The stereolithography apparatus according to any one of claims 1 to 4, wherein the nozzle is disposed between the temperature sensor and a pressing device.

6. The stereolithography apparatus according to claim 5, wherein the pressing device includes a pressing roller.

7. The positioning assembly includes a rotating member and a servo motor, and the servo motor is configured to rotate the rotating member to position the pressing device and the temperature sensor. The additive manufacturing apparatus according to claim 5.

8. An additive manufacturing method, comprising: heating a thermoplastic material with an extruder; supplying the heated thermoplastic material to an applicator assembly; depositing the heated thermoplastic material on a lower surface of the applicator assembly to form a first layer; while moving a temperature sensor around a nozzle of the applicator assembly, detecting a temperature of at least a portion of the first layer with a temperature sensor fixed to a bottom of the applicator assembly; determining whether the detected temperature indicates an actual temperature of at least a portion of the first layer; when the detected temperature indicates an actual temperature of at least a portion of the first layer, adjusting a moving speed of the applicator assembly based on the detected temperature; when the detected temperature does not indicate an actual temperature of at least a portion of the first layer, ignoring the detected temperature; and depositing the heated thermoplastic material on the first layer based on the adjustment of the moving speed to form a second layer. The additive manufacturing method includes.

9. Moving the temperature sensor includes changing an angular position of the temperature sensor. The additive manufacturing method according to claim 8.

10. The temperature sensor is inclined toward a position adjacent to a nozzle of the applicator assembly. The additive manufacturing method according to claim 8 or 9.

11. The nozzle is disposed between the temperature sensor and a pressing device. The additive manufacturing method according to claim 10.

12. Furthermore, when the detected temperature indicates a temperature lower than the temperature of a predetermined set point, increasing the moving speed of the applicator assembly when depositing at least a portion of the second layer, the additive manufacturing method according to any one of claims 8 to 11. **Claim 13** Furthermore, when the detected temperature indicates a temperature higher than the temperature of a predetermined set point, decreasing the moving speed of the applicator assembly, the additive manufacturing method according to any one of claims 8 to 12. **Claim 14** Adjusting the moving speed of the applicator assembly is based on the difference between the detected temperature and the temperature of a predetermined set point, and as this difference increases, the adjustment of the moving speed becomes greater, the additive manufacturing method according to any one of claims 8 to 13. **Claim 15** Furthermore, in order to identify a location where the temperature sensor is not directed towards the bead, analyzing the geometric shape of the bead associated with the detected temperature and the rotational direction position of the temperature sensor, and ignoring the temperature detected at the location, the additive manufacturing method according to any one of claims 8 to 14.

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