Multi-printing-nozzle automatic switching method, multi-color 3D printing system and computer storage medium

Abstract

The invention provides a multi-printing-nozzle automatic switching method, a multi-color 3D printing system and a computer storage medium. The multi-printing-nozzle automatic switching method is applied to a multi-color 3D printing system. The method comprises the steps that stopping coordinates and material color information of all nozzles are obtained; a printing instruction is responded, a tool head is used for clamping an initial nozzle to a calibration position to obtain reference coordinates of the initial nozzle, then the initial nozzle is moved to the position above a hot bed, the nozzle is heated to the melting temperature to complete the color printing task, heating is stopped after completion, and the nozzle is reset; and for the follow-up ith color task, the tool head clamps the corresponding ith spray head to the same calibration position to obtain the coordinates to be calibrated, the offset is calculated by using the coordinates to be calibrated and the reference coordinates, the coordinates of the spray head are calibrated, and finally the calibrated spray head is controlled to move to the hot bed to continue to execute the printing task. According to the method, the cost of the multi-color 3D printing system can be reduced, and meanwhile higher printing efficiency is achieved.

Description

Technical Field

[0001] This application relates to the field of multicolor 3D printing, and more specifically, to a method for automatic switching of multiple printheads, a multicolor 3D printing system, and a computer storage medium. Background Technology

[0002] In the three-dimensional (3D) printing industry, various multi-color solutions have emerged in recent years to meet the needs of multi-color printing and efficient color and material switching. However, these solutions still have several design flaws: For multi-tool head solutions, each tool head includes an extruder and a print head. Different colors of printing materials correspond to different tool heads, and multi-color printing is achieved by switching between different tool heads, but the cost of this technology is relatively high. For solutions that use dual print heads in conjunction with an Automatic Material System (AMS) multi-color box, two print heads are integrated into the tool head and a lifting device is used to switch between them. This achieves high printing efficiency while enabling two-color printing, but printing three or more colors requires reliance on the AMS multi-color box. Switching between different colors of printing materials also requires repeated steps such as cutting, filament extraction, and filament feeding, making the process complex. Furthermore, the tool head with dual print heads is relatively large.

[0003] Therefore, how to make multi-color 3D printing systems both lower in cost and higher in printing efficiency is an urgent problem to be solved. Summary of the Invention

[0004] This application provides a method for automatic switching of multiple printheads, a multi-color 3D printing system, and a computer storage medium, which enables the multi-color 3D printing system to have lower costs and higher printing efficiency.

[0005] Firstly, a method for automatic switching of multiple printheads is provided, applicable to a multi-color 3D printing system including a heated bed, a single tool head, and multiple printheads. Each printhead includes a printing nozzle. The method includes: acquiring a printing command; responding to a printing task based on the color information of a first printable material in the printing command; controlling the tool head to clamp the starting printhead and move it to a preset calibration position to obtain the reference coordinates of the starting printhead; controlling the tool head to move the starting printhead above the heated bed and initiating the printing task of the starting printhead; and after the starting printhead completes its printing task, responding to the printing... The instruction specifies the printing task for the color information of the i-th printing material. The control tool head clamps multiple printheads corresponding to the i-th printhead to be calibrated and moves them to a preset calibration position to obtain the i-th coordinates to be calibrated of the i-th printhead to be calibrated, where i∈[1,N], and N is any positive integer greater than 1. The coordinate offset between the i-th printhead to be calibrated and the starting printhead is calculated using the reference coordinates and the i-th coordinates to be calibrated. The coordinates of the i-th printhead to be calibrated are then calibrated using the coordinate offset, so that the calibrated i-th printhead to be calibrated can be moved above the heated bed to start the printing task.

[0006] Compared to multi-tool head technologies that combine a single tool head with a single printhead, the multi-color 3D printing system provided in this application can achieve multi-color printing with a single tool head and multiple printheads, effectively reducing costs. Furthermore, this application constructs different color printing channels using multiple printheads and multiple material trays. When switching between different colors, only the printhead needs to be switched, eliminating the need for a multi-color box and frequent filament cutting and feeding operations, significantly improving printing efficiency. In addition, the multi-color 3D printing system does not require pre-calibration of vision; instead, vision calibration is integrated into the printing process. Offset calibration and adjustment are performed after each printhead switch, improving the matching degree between the calibration results and the actual printing environment, thereby further improving the calibration accuracy of the printheads and ultimately enhancing the print quality of the multi-color 3D printing system.

[0007] Secondly, an automatic switching method for multiple printheads is provided, applicable to a multi-color 3D printing system including a heated bed, a single tool head, and N printheads. Each printhead includes a printing nozzle. The method includes: acquiring a printing command; responding to a printing task in the printing command with information on multiple colors of printing materials to determine a starting printhead and j printheads to be calibrated from the N printheads, where j ∈ [1, N], and N is any positive integer greater than 1; controlling the tool head to sequentially clamp the starting printhead and the j printheads to be calibrated and move them to a preset calibration position to obtain... Take the reference coordinates of the starting printhead and the j calibration coordinates of the j printheads to be calibrated; calculate the coordinate offsets of the j printheads to be calibrated relative to the starting printhead using the reference coordinates and the j calibration coordinates, and calibrate the coordinates of the j printheads to be calibrated to obtain the calibrated j printheads to be calibrated; respond to the printing order of the starting printhead and the j printheads to be calibrated in the printing command, control the tool head to sequentially clamp the starting printhead and the j printheads to be calibrated and move them above the heated bed to start the printing task.

[0008] The method provided in this application first performs uniform calibration on each printhead before starting the task. When a printhead is used multiple times during the printing process, it can avoid repeated calibration of the printhead during the printing process, which is beneficial to improving printing efficiency.

[0009] Thirdly, a multi-color 3D printing system is provided, comprising a heated bed, a single tool head, multiple printheads, multiple material trays, and a main board, wherein: the multiple material trays are respectively loaded with printing materials of different colors, and the printing materials on each material tray are respectively fed into each printhead so that the multiple printheads correspond one-to-one with the multiple material trays to form multiple printing channels with different colors; the tool head is used to selectively grip or release one of the multiple printheads for movement, and each printhead includes a printing nozzle on its underside; the main board is used to acquire printing instructions and execute the methods provided in the first and / or second aspects to control the heated bed, the tool head, and one or more of the multiple printheads to print 3D printed objects on the heated bed.

[0010] Fourthly, a computer storage medium is provided that stores computer program code, which, when run on the computer-readable storage medium, performs the methods provided in the first and / or second aspects. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of a 3D printing system provided in an embodiment of this application.

[0012] Figure 2 This is a schematic diagram of a multicolor 3D printing system provided in an embodiment of this application.

[0013] Figure 3 This is another schematic diagram of a multicolor 3D printing system provided in an embodiment of this application.

[0014] Figure 4 This is another schematic diagram of a multicolor 3D printing system provided in an embodiment of this application.

[0015] Figure 5 This is a schematic diagram of the structure of a printhead 240 provided in an embodiment of this application.

[0016] Figure 6 This is a schematic diagram of another printing nozzle 240 provided in an embodiment of this application.

[0017] Figure 7 This is a schematic diagram of the structure of another printhead 240 provided in the embodiments of this application.

[0018] Figure 8 This is a schematic diagram illustrating one implementation of a multicolor 3D printing system provided in this application.

[0019] Figure 9 This is a schematic diagram illustrating another implementation of a multicolor 3D printing system provided in this application.

[0020] Figure 10 This is a schematic diagram of the structure of the visual calibration device provided in the embodiments of this application.

[0021] Figure 11 This is a top view of the visual calibration device provided in the embodiments of this application.

[0022] Figure 12 This is a flowchart illustrating an automatic switching method for multiple printheads provided in an embodiment of this application.

[0023] Figure 13 This is a schematic flowchart of the visual calibration method provided in the embodiments of this application.

[0024] Figure 14 This is a single-frame reference contour image of the printing nozzle in the embodiments of this application.

[0025] Figure 15 These are side and top views of the printing nozzle provided in the embodiments of this application. Detailed Implementation

[0026] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0027] In the description of the embodiments in this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. In this application, "at least one" means one or more, and "more" means two or more.

[0028] The use of prefixes such as "first" and "second" in this application embodiment is solely for distinguishing different descriptive objects and does not limit the position, order, priority, quantity, or content of the described objects. The use of ordinal numbers and other prefixes to distinguish descriptive objects in this application embodiment does not constitute a limitation on the described objects. The description of the described objects is found in the claims or the context of the embodiments, and the use of such prefixes should not constitute unnecessary restrictions.

[0029] To keep the drawings concise, the figures in this application only schematically show the parts related to the corresponding embodiments, and they do not represent the actual structure of the product. In addition, to make the drawings concise and easy to understand, some figures only schematically show some structures or components, and there may actually be more or fewer identical or similar structures or components.

[0030] Figure 1 This is a schematic diagram of the structure of a 3D printing system 100 provided in an embodiment of this application. Figure 1 As shown, the 3D printing system 100 includes a material tray 101, an extruder 102, a printing nozzle 103, a heated bed 104, and a feeding pipe 105, which is connected to the material tray 101. During the printing process, the feeding pipe 105 picks up printing material from the material tray 101 and feeds it into the extruder 102. The extruder 102 includes one or more gears 1021. The printing material on the material tray 101 is fed into the printing nozzle 103 via the gears 1021 in the extruder 102. The printing nozzle 103 is used to heat-melt the printing material so that the molten printing material is extruded onto the heated bed 104. The heated bed 104 is used to hold the printing material. After the extruded printing material hardens and accumulates on the heated bed 104, a 3D printed object is formed.

[0031] Specifically, the printing material may also be referred to as filament and / or filament material, and its material includes, but is not limited to, at least one of the following: high molecular polymer, low melting point metal, other materials that can be formulated into a free-flowing paste (including, but not limited to, paste-like ceramics, high melting point metal powder mixtures, and cement).

[0032] In some implementations, the 3D printing system 100 also includes a motherboard ( Figure 1(Not shown in the image). As an example, the motherboard could be a control processing chip used to control the flow and speed of the printed material.

[0033] In one example, the 3D printing system 100 can form 3D printed objects through modeling, slicing and printing steps. The following is an exemplary printing process of the 3D printing system 100.

[0034] Step 1, Modeling

[0035] In the host computer, 3D printing models are generated through computer-aided design or 3D scanners.

[0036] Step 2, Slice

[0037] The created 3D printing model is processed into layers according to the printing order, dividing the 3D printing model into multiple layers to be printed, and obtaining the layer data of each layer to be printed. Finally, the relevant code of each layer to be printed is transmitted to the 3D printing system 100.

[0038] Step 3, Print

[0039] After obtaining the layer data of each layer to be printed, the 3D printing system 100 reads the relevant codes of each layer to be printed in sequence according to the printing order and generates the printing path for layer-by-layer printing. When all the layers to be printed of the 3D printing model have been printed and cooled and hardened, a 3D printed object can be formed.

[0040] In some related technologies, in order to enable 3D printed objects to have multiple colors and meet design requirements, existing technologies have provided various multi-color printing solutions. However, existing solutions still have several design flaws: For solutions using multiple tool heads, each tool head includes an extruder and a print head. Different colors of printing material correspond to different tool heads, and multi-color printing is achieved by switching between different tool heads, but the cost of related technologies is high. For solutions using dual print heads in conjunction with an Automatic Material System (AMS) multi-color box, two print heads are integrated into the tool head and a lifting device is used to achieve print head switching. This achieves high printing efficiency when printing two colors, but printing three or more colors requires reliance on the AMS multi-color box. Switching between different colors of printing material requires repeated steps such as cutting, filament extraction, and filament feeding, which is a relatively complex process, and the tool head with dual print heads is relatively large.

[0041] Based on this, this application addresses Figure 1An improvement was made to the 3D printing system 100, and a multi-color 3D printing system and an automatic switching method for multiple printing nozzles were proposed, thereby reducing costs and improving the feeding efficiency of the printing nozzles, while further improving the printing accuracy of the multi-color 3D printing system.

[0042] Figures 2 to 4 This is a schematic diagram of a multi-color 3D printing system 200 provided in an embodiment of this application. The multi-color 3D printing system 200 includes a main board 210, a heated bed 220, a tool head 230, multiple printing nozzles 240 (or N printing nozzles 240), multiple material trays 250, a feeding pipe 260, and an extruder (not shown in the figure). Further, the multi-color 3D printing system 200 also includes a printing tool (not shown in the figure, or printing software) configured on a host computer. The printing tool obtains the relevant codes of each printing layer of the 3D printed object to be printed, generates printing instructions, and sends them to the main board 210. The main board 210 is used to execute the multi-printing nozzle automatic switching method provided in one or more embodiments of this application according to the printing instructions to control one or more of the heated bed 220, tool head 230, and printing nozzles 240, so as to switch different printing nozzles 240 to print multi-color 3D objects on the heated bed 220. It should be understood that the host computer in this application is a processing terminal with a computing power greater than that of the motherboard 210 in the multicolor 3D printing system 200, such as a computer, desktop computer, cloud, or mobile phone.

[0043] The multi-color 3D printing system 200 includes one or more printheads 240, which are connected to a tool head 230. The multi-color 3D printing system 200 also includes one or more material trays 250, which are loaded with at least two different colors of printing material and fed into the printheads 240 through corresponding feed pipes 260 to form multiple printing channels.

[0044] One possible scenario is that one printhead corresponds to one tray to form a printing channel. Another possible scenario is that multiple printheads correspond to one printhead and one tray from multiple trays to form a printing channel. Thus, multiple printheads and multiple trays correspond one-to-one to form multiple printing channels with different colors, without relying on a multi-color box.

[0045] Tool head 230 includes a printed circuit board (PCB), a motor, and a clamping and fastening structure. Figures 2 to 4 (Not shown in the image). The PCB board, under the control of the motherboard 210, controls the tool head 230 to selectively pick up and release different printheads 240, switching between them to achieve multi-color printing. A clamping and locking structure is used to clamp and lock the printheads 240.

[0046] Figure 5This is a schematic diagram of the structure of a print head 240 provided in an embodiment of this application. The print head 240 includes a perforated structure 2401, a throat 2402, and a print nozzle 2403 arranged sequentially for melting printing material to print multi-color 3D objects on a heated bed 220. In some embodiments, the extruder includes one or more drive wheels and driven wheels for clamping the printing material located inside the print head 240 and pushing the printing material downward so that the print head 240 is loaded with printing material that passes sequentially through the perforated structure 2401, the throat 2402, and the print nozzle 2403 of the print head 240. Preferably, the drive wheel in the extruder can be located in the tool head, and the driven wheel can be located in the tool head or the print head. In this case, the PCB board also integrates a drive module. When the tool head 230 grips the print head 240, the drive wheel and the driven wheel cooperate to clamp the printing material located in the print head 240 through the hollow structure 2401. The drive module brakes the motor to drive the drive wheel to rotate, and the drive wheel drives the driven wheel to rotate, thereby applying a downward thrust to the printing material in the print head 240, causing the printing material to be conveyed downward. It should be understood that the PCB board can also implement, but is not limited to, at least one of the following: heating power supply, temperature ADC, and accelerometer.

[0047] In the extruder, one or more driven wheels include, but are not limited to, idler wheels. In one embodiment, the driven wheels are disposed in the tool head 230 (not shown in the figure). When the tool head 230 picks up the print head 240, the drive wheel and driven wheel in the tool head 230 clamp the printing material through the hollow structure 2401. The motor in the tool head 230 drives the drive wheel and driven wheel to rotate, so as to apply a downward force to the clamped printing material, so as to push the printing material towards the throat 2402 and the print nozzle 2403.

[0048] In another embodiment, one or more driven wheels 24011 are disposed in the hollow structure 2401 of each print head. Printing material enters the hollow structure 2401. When the tool head 230 picks up the print head 240, the driving wheel in the tool head 230 cooperates with the driven wheel 24011 in the hollow structure 2401 to clamp the printing material. The motor in the tool head 230 drives the driving wheel to rotate, causing the driven wheel 24011 in the hollow structure 2401 to rotate, applying a downward force to the clamped printing material, thus propelling the printing material towards the throat 2402. After entering the throat 2402, the printing material continues to be propelled towards the print nozzle 2403 under the action of the driving wheel and the driven wheel 24011. It should be understood that, compared to disposing the driven wheels in the hollow structure of each print head, disposing the driven wheels in the tool head eliminates the need to configure driven wheels in each print head, reducing the number of driven wheels and thus saving costs.

[0049] In this embodiment, different printing channels of different colors are formed by different printing nozzles and different material trays. An extruder is formed by the cooperation of the driving wheel and driven wheel of the tool head or the driving wheel of the tool head and the driven wheel in the hollow structure. The tool head is controlled to selectively pick up different printing nozzles and apply downward force to the printing material corresponding to the printing nozzles of different printing channels through the extruder, thereby realizing multi-color printing. This allows the multi-color 3D printing system to switch printing nozzles and printing materials without cutting the printing material, or removing old material and re-feeding new material, reducing printing material waste and improving 3D printing efficiency.

[0050] After the printing material enters the printing nozzle 2403, it needs to be heated to make it fluid, so that it can be extruded from the printing nozzle 2403 and hardened and deposited on the heated bed 220 according to a preset shape. To achieve heating of the printing material in the printing nozzle 2403, this application provides two implementation methods. One is to attach a heating module to the outside of the printing nozzle 2403, such as... Figure 7 As shown in the figure; secondly, a heating module (not shown) is integrated on the tool head 230. When the tool head 230 clamps the print head 240, the heating module is in close contact with the print nozzle 2403. The heating module is usually made of conductive ceramic material. By supplying power to the conductive ceramic material, heat is generated due to the resistance of the material. This heat energy is transferred to the heating module to uniformly heat the print nozzle 2403, thereby melting the printing material located inside the print nozzle 2403. This allows the fluid printing material to be extruded from the print nozzle 2403 and hardened and deposited on the heated bed 220.

[0051] Furthermore, to precisely control the heating module to heat the print nozzle 2403 to the preset melting temperature, the printing system 200 also needs to monitor the temperature of the print nozzle 2403 in real time, so as to adjust the heating state of the heating module in reverse according to the temperature of the print nozzle, thereby realizing a closed-loop heating control. To this end, this application also provides two methods for detecting the temperature of the print nozzle 2403. One method is to provide a temperature sensing component on the outside of the print nozzle 2403, such as... Figure 7 As shown, the temperature sensing component can be a thermistor, and the real-time temperature of the print nozzle 2403 can be detected by powering the temperature sensing component; the second is to integrate a temperature sensing component (not shown in the figure) in the tool head 230. In this case, the temperature sensing component can be a temperature sensor. When the tool head 230 clamps the print head 240, the temperature sensor contacts the print nozzle 2403 to detect the real-time temperature of the print nozzle 2403.

[0052] It should be understood that the aforementioned heating module and temperature measuring component can be integrated into either the tool head 230 or the print head 240. When each print head 240 integrates the heating module, temperature measuring component, and the driven wheel of the extruder, the heating speed of the print head can be increased. When a portion of the heating module and temperature measuring component is integrated into the shared tool head 230, and the print head 240 integrates another portion of the heating module and temperature measuring component, it is not necessary for each print head 240 to integrate a heating module or temperature measuring component, thereby reducing the overall cost of the printing system and further compressing the size of the print head. When both the heating module and temperature measuring component are integrated into the shared tool head 230, in addition to reducing costs and compressing the size of the print head, the reliability of the 3D printing system during long-term use can also be improved, given that no electrical connection is required between the print nozzle and the tool head.

[0053] When the heating module and temperature sensing component are both integrated in the print head 240, power supply is required for the heating module and temperature sensing component to function properly, and the heating state of the heating module needs to be adjusted in reverse according to the real-time temperature of the print nozzle 2403. Therefore, this application provides three methods for achieving power supply / data transmission, as follows:

[0054] One possible implementation involves powering and transmitting data to the heating module and temperature sensing component on the print head 240 via the tool head 230. Specifically, the PCB board of the tool head 230 has a power supply / data transmission module, and power supply and data transmission between the tool head 230 and the print head 240 are achieved through contact-based power supply and contact-based data transmission. In this case, the print head 240 also includes an electrical connector for electrical connection to the heating module and temperature sensing component, such as... Figure 6 As shown. When the tool head 230 clamps the print head 240, the power supply / data transmission module is electrically connected to the electrical connector to provide power and transmit data to the heating module and temperature sensing component via the PCB board of the tool head 230 under the control of the motherboard 210, thereby heating the print nozzle 2403 and detecting the temperature of the print nozzle 2403. After the temperature sensing component obtains the temperature of the print nozzle 2403, it sends temperature data to the PCB board through the power supply / data transmission module to monitor the temperature of the print nozzle 2403 in real time, so that the PCB board can provide feedback to the motherboard 210 as to whether the heating state of the heating module needs to be adjusted in reverse according to the real-time temperature of the print nozzle 2403. As an example, contact power supply and data transmission include, but are not limited to, Pogo Pin form and / or pin form (as an example, 2 heating pins and 2 temperature signal reading pins).

[0055] Another possible implementation is that the printhead 240 and the motherboard 210 are powered and transmit data via electrical connection lines, including but not limited to power lines and / or data lines. Figure 7This is a schematic diagram of the structure of another printhead 240 provided in the embodiments of this application, as shown below. Figure 7 As shown, the electrical connection cable runs from the top of the printhead 240 along the hollow structure 2401 and the throat 2402 to the print nozzle 2403, and is electrically connected to the temperature sensing component and the heating module, enabling power supply and data transmission to the temperature sensing component and the heating module. After detecting the real-time temperature of the print nozzle 2403, the temperature sensing component sends temperature data to the main board 210 through the electrical connection cable to monitor the temperature of the print nozzle 2403 in real time and to reversely regulate the heating module.

[0056] Another possible implementation involves wireless power supply and data transmission between the printhead 240 and the tool head 230. The printhead 240 integrates a metal sensor, a wireless power supply coil, and a first wireless communication chip, while the tool head 230's PCB board integrates a heating coil, a wireless power supply coil, and a second wireless communication chip. Given the embedded metal sensor (including but not limited to ferromagnetic materials) inside the printhead 240, when the tool head 230 clamps the printhead 240, the heating coil on the tool head 230 generates a high-frequency alternating magnetic field, causing eddy currents in the metal sensor within the printhead 240, thereby generating heat to heat the print nozzle 2403. Meanwhile, the first wireless power supply coil of the print head 240 and the second wireless power supply coil of the tool head 230 provide the necessary power to the first wireless communication chip in the print head 240 under the action of electromagnetic effect, so that the first wireless communication chip can transmit data with the second wireless communication chip in the PCB board of the tool head 230 to send the temperature of the print nozzle 2403 detected in real time by the temperature measuring component. The PCB board feeds back the temperature to the main board 210 to determine whether the print nozzle 2403 needs to be heated further.

[0057] In the embodiments of this application, there are multiple connection methods between the printing nozzle and the tool head, which can improve the flexibility of the 3D printing system.

[0058] In some implementations, such as Figures 5 to 7 As shown, the feeding pipe 260 above the print head 240 can be a Teflon tube. Specifically, the printing material on the tray 250 enters the print head 240 through the Teflon tube. When the print head 240 is initially fed or when a new material is replaced, the printing material needs to be pushed into the Teflon tube, allowing it to enter the print head 240 along the Teflon tube and reach the throat 2402 through the perforated structure 2401. After the tool head 230 locks the print head 240 through the clamping and fastening structure, the printing material at the perforated structure 2401 is pushed downward under the force of the tool head 230's drive wheel and the print head 24011's driven wheel, and is heated and melted by the print nozzle 2403 before being extruded from the print nozzle 2403.

[0059] In some embodiments, the tool head 230 is further provided with a cutting structure at the corresponding position of the hollow structure 2401 of the print head 240. When the print head 240 needs to replace the printing material and the old printing material is extracted from the print head 240, the old printing material is cut off by the cutting structure at the hollow structure 2401. The old printing material above the hollow structure 2401 is manually extracted or extracted with the assistance of an external motor before the new printing material is pushed in. The new printing material is pushed downward by the driving wheel of the tool head 230 and the driven wheel 24011 in the print head 240. During the downward movement of the new printing material, the old printing material below the hollow structure 2401 is heated, melted, and extruded.

[0060] During the heating process of the print nozzle 2403, in order to prevent the high temperature of the print nozzle 2403 from being transferred to the throat 2402, causing the printing material to melt and block the throat 2402, such as... Figures 5 to 7 As shown, a heat sink 24021 can also be provided on the outside of the throat tube 2402 to dissipate heat, prevent the printing material from melting in the throat tube 2402, and ensure that the printing material remains a hardened material at the throat tube 2402.

[0061] In some embodiments, to slow down the heat loss rate of the print nozzle 2403, the print head 240 may also be provided with a heat insulation shell 2404 for wrapping the structure of the print nozzle 2403, the heating module and the temperature measuring components, so as to improve heating efficiency.

[0062] In some embodiments, the multicolor 3D printing system 200 also includes a wiping structure, which can be located on any side of the bottom surface inside the cavity of the multicolor 3D printing system 200, for wiping residual printing material from the printing nozzles 2403 to ensure that there is no residual material at the outlet of the printing nozzles 2403. Specifically, before and / or after each printing operation, the main board 210 can control the printing nozzles 240 to move to the location of the wiping structure, so that the printing nozzles 2403 in the printing nozzles 240 touch the wiping structure to clean the residual, melted and hardened printing material on the printing nozzles 2403 through friction. This prevents the printing nozzles 240 from directly printing residual printing material onto the intact printing layer during the next printing operation, which would cause abnormal protrusions in the printing layer and reduce printing quality.

[0063] To enable the multi-color 3D printing system 200 to print from multiple dimensions and improve printing efficiency, the X and Y axes of the multi-color 3D system coordinate system are constructed parallel to the horizontal plane, with the X and Y axes perpendicular to each other, and the Z axis perpendicular to the horizontal plane, as shown below. Figures 2 to 4As shown, the multicolor 3D printing system 200 also includes a sliding rod 270 that can move along the Y-axis, a tool head 230 that is slidably mounted on the sliding rod 270 so that it can slide along the X-axis on the sliding rod 270, and a heated bed 220 that can move along the Z-axis.

[0064] In the embodiments of this application, the print head of the multicolor 3D printing system has three degrees of freedom of motion in three-dimensional space (also known as 3DOF). Through the combined motion of the three directions of XYZ, it accumulates printing material layer by layer to improve printing efficiency and finally builds a 3D printed model.

[0065] Since the multicolor 3D printing system 200 includes multiple printheads 240, to neatly arrange the multiple printheads 240, the multicolor 3D printing system 200 provided in this application also includes a docking station for attaching one or more printheads 240 to be used. Simultaneously, to facilitate the tool head 230 in clamping the printhead 240, the multicolor 3D printing system 200 also includes a crossbeam, which is arranged parallel to the sliding rod where the tool head 230 is located. The docking station is fixed to this crossbeam. Thus, the tool head 230 can precisely clamp the printhead through the cooperation of the sliding rod and its body in the first and second directions, without requiring movement in a third direction.

[0066] The docking station can also be equipped with a position sensor to sense whether the print head 240 is correctly attached to the docking station. It should be noted that the position of the docking station can be set on any one or more planes of the multi-color 3D printing system 200, which is determined by the movable direction of the tool head 230. This embodiment of the application does not limit this; however, when the multi-color 3D printing system 200 leaves the factory, the position of the print head 240 on the docking station needs to be calibrated and finely adjusted. Thus, the coordinates of the attachment points on the docking station are pre-planned and precisely processed, so that the tool head 230 can accurately find each print head 240 and stably attach it.

[0067] Corresponding to the three methods of power supply / data transmission described above, this application provides two such methods. Figure 8 and Figure 9 The docking station design shown. In one possible scenario, such as... Figure 8As shown, when the power supply and data transmission between the printhead 240 and the tool head 230 are conducted via contact and / or wireless methods, the dock also includes a preheating module. This preheating module is either a power supply / signal transmission module or a heating coil. The preheating module connects to the electrical connectors of all printheads 240 or generates eddy currents with the metal sensors in the printhead 240. Therefore, the print nozzles 2403 in the printhead 240 can be preheated before the tool head 230 clamps the printhead 240. When the tool head 230 clamps the printhead 240, the print nozzles 2403 are already at a relatively high temperature, thus shortening the heating waiting time of the printhead 240.

[0068] In another possible scenario, such as Figure 9 As shown, when the printhead 240 and the motherboard 210 are powered and transmit data via independent electrical connection lines, the corresponding electrical wire at the top of each print nozzle 2403 is connected to the docking station, and then connected to the power supply and signal interface of the motherboard 210 through the docking station, so that the motherboard 210 can supply power to each printhead 2403 and realize data transmission. Therefore, when the printhead 240 needs to be preheated, the temperature measuring component and heating module can be directly powered through the existing electrical wires to preheat the print nozzles 2403 of the printhead 240, without the need for an additional preheating module.

[0069] Furthermore, when a multi-color 3D printing system switches between different printheads to switch between different colored materials, mechanical and physical deviations can easily lead to spacing discrepancies between the switched printhead and the original printhead on the X, Y, and Z axes relative to the heated bed. This results in the material extruded from the switched printhead not landing precisely and seamlessly on the layer printed by the previous printhead. Current mainstream calibration methods fall into three categories: First, a method that uses the printheads before and after switching to print additional lines or graphics and then manually compares and adjusts them; however, this method requires manual intervention and cannot achieve fully automated calibration. Second, an eddy current sensing method, which measures the offset between the two nozzles using an eddy current sensor before printing; however, eddy current sensors are sensitive to external magnetic fields, and measurement accuracy is affected in strong magnetic field environments. Third, a method that uses a position sensor to determine position calibration based on the electrical signal generated by the nozzle contact; although this process can be fully automated, it requires high sensor accuracy, and the distance between the nozzle edge and the discharge port can easily cause errors. In addition, the above calibration schemes are all calibrated before printing, but not during the printing process. Due to the temperature difference between before and during printing, thermal expansion and contraction will cause the pre-calibrated offset to be inaccurate, and it can only rely on the initial assembly accuracy to control it, which makes the structural assembly tolerance requirements high.

[0070] Therefore, the multicolor 3D printing system 200 provided in this application also includes a visual calibration device 280, and this application also provides a visual calibration method applied to the system.

[0071] like Figure 2 and Figure 4 As shown, the vision calibration device 280 is used to acquire images of the print head 240 that the tool head 230 switches each time, so as to obtain the offset of the print head 240 after switching based on the acquired images for accurate calibration, thereby improving the accuracy of multicolor 3D printing and enhancing the printing quality of the multicolor 3D printing system.

[0072] Figure 10 This is a schematic diagram of the visual calibration device in an embodiment of this application. (Combined with...) Figure 4 and Figure 10 As shown, the visual calibration device 280 includes a reflective element 2801, a camera 2802, and a calibration tool (or "calibration software") applied to the host computer. During the multi-color 3D printing system 200 switching between different printheads for multi-color printing, when the motherboard controls the printhead to move to a preset calibration position, at this position, the reflective element 2801 deflects the light reflected from the bottom contour of the print nozzle 2403 on the underside of the printhead 240 in the multi-color 3D printing system 200 into the camera 2802. This light can carry... The image captures information such as the shape, color, and texture of the bottom contour of the printing nozzle 2403. A camera 2802 simultaneously captures light reflected from the bottom and side contours of the printing nozzle 2403, generating a single-frame contour image including the bottom and sides of the nozzle. A calibration tool receives this contour image and extracts the coordinates of the printing nozzle. The coordinates of the nozzle are then calculated by subtracting the coordinates from a reference value to obtain the coordinate offset of the bottom outlet of the printing nozzle 2403 along the XYZ axes. This coordinate offset is used to calibrate the print head 240 corresponding to the printing nozzle 2403. The single-frame contour image in this application includes both the bottom and side contours of the printing nozzle, which facilitates obtaining the coordinate offset of the printing nozzle in the three XYZ axes simultaneously, eliminating the need to acquire multiple contour images and improving calibration efficiency.

[0073] It should be understood that the calibration tool in this application and the printing tool in the aforementioned multicolor 3D printing system 200 can be integrated into one software or separated into two software programs. Integration into one software program is more advantageous for improving printing efficiency and user experience. Furthermore, both the printing tool and the calibration tool can be configured on a host computer. When the motherboard of the printing system has high computing power, they can also be mounted on the motherboard 210 of the printing system; this application does not impose any restrictions.

[0074] In some embodiments, camera 2802 can be a color camera including a Bayer filter. In this case, the single-frame contour image is a color image, which can provide additional color texture information of the side and bottom surfaces of the printing nozzle, which is beneficial for the algorithm to identify and locate the position of the printing nozzle 2403. However, color cameras require the motherboard to have image signal processing capabilities, which places higher demands on the platform. Camera 2802 can also be a monochrome camera without any filter. In this case, the single-frame contour image is a grayscale image including the brightness information of the side and bottom surfaces of the printing nozzle. Grayscale images have lower computing power requirements, and monochrome cameras are relatively cheaper because they do not include filters. In addition, camera 2802 can also be a depth camera based on the structured light principle, time-of-flight principle, or binocular principle. In this case, the single-frame contour image is a depth image including the depth information of the side and bottom surfaces of the printing nozzle. The coordinates of the printing nozzle 2403 in the Z-axis direction (also known as the third direction) in the coordinate system of the multicolor 3D printing system 200 can be directly obtained. However, compared with color cameras and monochrome cameras, depth cameras require additional projection devices or camera devices, which increases the cost.

[0075] The camera 2802 is located inside the system cavity, such as next to the heated bed 220, and cannot move with the heated bed 220. Its optical axis is parallel to the horizontal plane so as to receive the light reflected by the reflective element 2801 and simultaneously collect the light reflected by the side of the printing nozzle 2403 to obtain a single-frame contour image including the bottom and side of the printing nozzle 2403.

[0076] In some embodiments, the visual calibration device further includes a supplementary light 28021, which is disposed around the outer periphery of the camera 2802 or surrounds the outer periphery of the camera 2802 and is coaxial with the optical axis of the camera 2802. It is used for supplementary lighting to improve the image's resistance to ambient light interference and enhance the image's contrast and illumination consistency, facilitating subsequent algorithm processing. The supplementary light 28021 is preferably a light source type that can enter the camera 2802 for imaging, such as a visible light or near-infrared supplementary light. This application does not limit the number of supplementary lights 28021.

[0077] Figure 11 The image shown is a top view of a vision calibration apparatus according to an embodiment of this application. In some embodiments, the positions of the components in the vision calibration apparatus 280 are as follows: Figure 11As shown, the control tool head 230 moves the printing nozzle 2403 in the printing nozzle 240 to a preset calibration position located above the reflective element 2801. In the coordinate system of the multicolor 3D printing system 200, the coordinates of the preset calibration position on the X and Y axes can be denoted as (X_cal, Y_cal). The preset calibration position is related to the setting position of the reflective element 2801 so that the reflective element 2801 can accurately reflect the light reflected by the bottom contour of the printing nozzle 2403 in the printing nozzle 240 into the camera 2802 for imaging. When the printing nozzle 240 is moved to the preset calibration position, the reflective element 2801 reflects the light including the bottom contour information of the printing nozzle 2403 into the camera 2802.

[0078] Optionally, the reflective element 2801 is a mirror or a prism, which can be installed beside or on the heated bed 220. Preferably, the reflective element 2801 is a mirror or a 45° prism installed at an angle of 45° to the horizontal plane. The reflective element 2801 is preferably installed in a fixed position beside the heated bed 220 and does not move with the heated bed 220. It should be understood that the reflective element 2801 can also be installed on the heated bed 220, but this installation requires the heated bed 220 to be moved to a specific height for each calibration. Raising the heated bed 220 may cause the tool head 230 to touch the printed model, thereby reducing the print quality. Therefore, this application does not limit the position of the reflective element 2801 relative to the heated bed 220, and it can be designed according to the actual quality requirements.

[0079] In other embodiments, multiple reflective elements 2801 are included, and their placement is associated with the mounting position of the camera 2802. The camera 2802 can be mounted anywhere within the system. When the position of the camera 2802 is determined, the placement of each reflective element 2801 needs to be designed around the reflected light from the bottom and sides of the printing nozzle to deflect the reflected light from the bottom and sides of the printing nozzle into the camera 2802, ensuring that the camera 2802 can capture a single-frame contour image that simultaneously includes the bottom and sides of the printing nozzle. This design allows the camera 2802 to be placed not only beside the heated bed but also at the bottom or top of the system, improving the design flexibility of the multi-color 3D printing system. In addition, placing both the camera and reflective elements beside the heated bed prevents them from moving with the heated bed, improving calibration accuracy and avoiding damage to the printed model, thus ensuring printing quality.

[0080] The above, combined with Figures 2 to 11 The system provided in the embodiments of this application is described in detail below. Figures 12 to 15The methods provided in the embodiments of this application are described in detail. It should be understood that the descriptions of the method embodiments correspond to the descriptions of the system embodiments. Therefore, for content not described in detail, please refer to the above system embodiments. For the sake of brevity, they will not be repeated here.

[0081] Figure 12 This is a flowchart illustrating an automatic multi-printer head switching method 1200 provided in an embodiment of this application, applied to... Figure 2 The multicolor 3D printing system 200 shown includes a motherboard 210, and the method includes:

[0082] S1210: Obtain the docking coordinates of N printheads and the color information of the printed material of N printheads, where N is any positive integer greater than 1.

[0083] Specifically, the docking coordinates of the N printheads (also referred to as the docking coordinates of the i-th printhead to be calibrated) are the docking position coordinates of the printheads on the docking station in the multi-color 3D printing system 200; the print material color information of the printheads is the color information of the print material on the printing channel formed by the printhead and the corresponding material tray. It should be noted that before obtaining the docking coordinates of the printheads and the corresponding print material color information, the printheads and material trays in the multi-color 3D printing system 200 need to be pre-configured. The specific steps are as follows:

[0084] Step 1: Prepare the printhead and N trays containing different colored printing materials.

[0085] Hang all the printheads to be used on the dock. Manually or with the help of an external auxiliary motor, push the printing material from the N material trays to be used from the Teflon tubes corresponding to the printheads. The printing material passes through the hollow structure of the printhead to reach the throat. Insert the printing material into the lower position of the hollow structure to form multiple printing channels with different colors.

[0086] It should be noted that the coordinates [x_n, y_n] of the docking point of the print head N on the dock (also known as the docking coordinates) are automatically preset and stored by the 3D printing system at the factory. When the printing tool in the host computer communicates with the multi-color 3D printing system, it can read the above information from the multi-color 3D printing system, thereby guiding the tool head to unload and load specific print heads N at specific positions. It should be understood that the docking point coordinates can be customized by the user or restored to the production settings.

[0087] Step 2, Configure printhead and printing material information

[0088] Configure the nozzle orifice diameter, printing material color (also known as printing material color information), filament diameter, critical melting temperature, and optimal melting temperature of printing material for each nozzle 1 to N in the printing tool. This will allow you to set the preset melting temperature for each nozzle and better heat each nozzle in the future.

[0089] S1220: Obtain the printing instruction, respond to the printing task of the first printing material color information in the printing instruction, control the tool head to move to the docking coordinate of the starting printing nozzle corresponding to the N printing nozzles and clamp the starting printing nozzle to move to the preset calibration position, so as to obtain the reference coordinate of the starting printing nozzle.

[0090] As an example, the printing tool in the host computer sends a printing command to the motherboard 210 of the multicolor 3D printing system 200. The motherboard 210 controls the tool head 230 to move to the docking point coordinates [x_a, y_a] of the starting printing nozzle. The tool head 230 clamps and locks the starting printing nozzle through the clamping and fastening structure inside. The drive wheel cooperates with the driven wheel 24011 to clamp the printing material at the hollow structure above the starting printing nozzle and apply downward force to push the printing material towards the printing nozzle. The heated bed leveling and vibration compensation are started to ensure the flatness of the heated bed before the printing task is started, thereby improving the printing quality.

[0091] The reference coordinates are reference pixel coordinates. When the starting print head moves to the preset calibration position, the camera in the vision calibration device of the multicolor 3D printing system is controlled to acquire reference contour images including the bottom and side of the printing nozzle corresponding to the starting print head, so as to extract the reference pixel coordinates (X_p1, Y_p1, Z_p1) of the printing nozzle corresponding to the starting print head in the coordinate system of the multicolor 3D printing system from the reference contour images.

[0092] S1230: The control tool head moves the starting print head above the heated bed, heats the corresponding print nozzle of the starting print head to the preset melting temperature to start the printing task of the starting print head, and makes the printing material squeezed out from the print nozzle to complete the printing task.

[0093] Specifically, the tool head and / or printhead integrates a heating module and / or temperature sensing component. The heating module and temperature sensing component are powered via the PCB board in the tool head or the mainboard in the system to preheat the printhead and read the printhead temperature information in real time. Whether the PCB board in the tool head or the mainboard in the system can read the printhead temperature information in real time determines whether the circuit connection between the heating module and / or temperature sensing component and the tool head or mainboard is normal. If it is normal, the temperature information is used to control the heating state of the heating module on the printhead; if it is abnormal, the circuit connection between the heating module and / or temperature sensing component and the tool head or mainboard needs to be tested.

[0094] As an example, the heating module and temperature measuring component corresponding to the print head are powered on. The heating module heats the print nozzle, and the temperature measuring component monitors the temperature of the print nozzle in real time. The real-time temperature monitoring is used to reverse the heating state of the heating module on the print nozzle so that the print nozzle can accurately reach the optimal printing temperature, i.e., the preset melting temperature. The heated bed is heated simultaneously. After both the print nozzle and the heated bed reach the expected temperature, the printing task of the print head is started.

[0095] S1240: After the starting print head completes the printing task, stop heating the corresponding print nozzle of the starting print head, and control the tool head to move the starting print head to the docking coordinate of the starting print head to attach the starting print head.

[0096] Specifically, after the initial print head completes its printing task, heating is stopped, and the tool head is moved to the docking point coordinates [x_a, y_a] of the initial print head. The clamping and fastening structure, the driving wheel, and the driven wheel 24011 are released, and the initial print head is docked onto the dock. The position sensor on the dock determines whether the docking is successful. If the docking is successful, the tool head is controlled to clamp the next print head. If the docking is unsuccessful, the tool head is re-clamped and released to adjust the docking position of the initial print head, or the docking position of the initial print head is adjusted manually to facilitate accurate clamping by the tool head next time.

[0097] S1250: In response to the printing task of the i-th printing material color information in the printing instruction, control the tool head to hold N printing nozzles corresponding to the i-th printing nozzle to be calibrated and move them to the preset calibration position to obtain the i-th calibration coordinate of the i-th printing nozzle to be calibrated, where i∈[1,N].

[0098] Specifically, based on the printing task corresponding to the color information of the i-th printing material, the control tool head moves to the attachment point coordinates [x_i, y_i] of the i-th printhead to be calibrated, which has the corresponding color printing material. The control tool head clamps the i-th printhead to be calibrated and moves it to the same preset calibration position as the starting printhead. The i-th calibration coordinate is the i-th calibration pixel coordinate. When the i-th printhead to be calibrated is moved to the preset calibration position, the camera in the multi-color 3D printing system's visual calibration device acquires the i-th frame contour image, including the bottom and side of the print nozzle corresponding to the i-th printhead to be calibrated, to extract the i-th calibration pixel coordinate corresponding to the i-th printhead to be calibrated from the i-th frame contour image. In addition, the reference coordinate and the coordinate to be calibrated in this application can be not only pixel coordinates, but also camera coordinates in the camera coordinate system, world coordinates in the world coordinate system, or metric coordinates with scale units (such as metric coordinates with millimeters as the unit). All of these can be converted from pixel coordinates, as long as the reference coordinate and the coordinate to be calibrated are in the same coordinate system. This application does not impose any restrictions here.

[0099] It should be understood that the i-th printhead to be calibrated can be the starting printhead, because the printing layers corresponding to the 3D printed object have repeated color intervals. For example, the printing material corresponding to the starting printhead of a multi-color 3D printing system is red, and the colors of the multiple printing layers of the 3D printed object are red, yellow, green, red, etc. Therefore, after the red printing layer is printed by the starting printhead, it is necessary to switch to other printheads to print the yellow and green printing layers. After the yellow and green printing layers are printed, it is necessary to switch back to the starting printhead to print the red printing layer, thereby achieving repeated color printing.

[0100] S1260: Calculate the coordinate offset between the i-th printhead to be calibrated and the starting printhead using the reference coordinates and the i-th coordinate to be calibrated, and then calibrate the coordinates of the i-th printhead to be calibrated by using the coordinate offset, thereby controlling the calibrated i-th printhead to repeat steps S1230 and S1240 to continue printing to complete the printing task in the printing instruction.

[0101] To improve calibration accuracy and print quality, before the control tool head moves the starting print head or the i-th print head to be calibrated above the heated bed, the process includes: the control tool head clamping the print head to the wiping structure of the multi-color 3D printing system, so that the print head and the corresponding print nozzle touch the wiping structure to clean the residual consumables of the printed material in the previous printing task through friction, or controlling the print head to move above the wiping structure of the multi-color 3D printing system for preliminary printing to remove the residual consumables of the print nozzle, and then moving it above the heated bed for formal printing, to ensure that there are no residues obstructing the outlet of the print nozzle.

[0102] In this embodiment, the multi-color 3D printing system eliminates the need to cut off the printing material or remove old material and refill it when switching printheads and printing materials, reducing material waste and improving 3D printing efficiency. Furthermore, the multi-color 3D printing system does not require pre-calibration. During the printing process, offset calibration and adjustment are performed after each printhead switch, improving the matching degree between the calibration results and the actual printing environment. This further enhances the accuracy of printhead calibration and ultimately improves the print quality of the multi-color 3D printing system.

[0103] The above-described automatic multi-printer head switching method switches different printers for multi-color printing based on the calibration embedding system of each printer head. In some embodiments, all printers can be uniformly calibrated first, and then the calibrated printers can be used to start the printing task. This method includes: obtaining a printing command; responding to the printing task containing multi-color printing material information in the printing command to determine the starting printer head and j printers to be calibrated from N printers head, where j∈[1,N], and N is any positive integer greater than 1; and controlling the tool head to sequentially clamp the starting printer head and the j printers to be calibrated. The printhead moves to a preset calibration position to obtain the reference coordinates of the starting printhead and the j calibration coordinates of the j printheads to be calibrated. Using the reference coordinates and the j calibration coordinates, the coordinate offsets of the j printheads to be calibrated relative to the starting printhead are calculated, and the coordinates of the j printheads to be calibrated are calibrated using the coordinate offsets to obtain the calibrated j printheads to be calibrated. In response to the printing order of the starting printhead and the j printheads to be calibrated in the printing command, the control tool head sequentially clamps the starting printhead and the j printheads to be calibrated and moves them above the heated bed to start the printing task.

[0104] This embodiment performs a unified calibration on each printhead before starting the printing task. When a printhead is used multiple times during the printing process, it avoids repeated calibration of that printhead, thus improving printing efficiency. It should be understood that this embodiment only moves the calibration process for each printhead to before the multi-color 3D printing system starts its first printing task. The working methods of the tool head, printhead, and other components during the execution of the corresponding printing task by each printhead in this embodiment are the same as in the above embodiments, and will not be repeated here.

[0105] Optionally, in response to a printing command, the reference coordinates of the starting print head and the calibration coordinates of the print head to be calibrated are obtained, and the coordinate offset between the print head to be calibrated and the starting print head is calculated using the reference coordinates and the calibration coordinates. The coordinates of the print head to be calibrated are then calibrated using the coordinate offset. Alternatively, the visual calibration method 1300 provided in this application embodiment can be used.

[0106] Figure 13This is a flowchart illustrating the visual calibration method provided in an embodiment of this application. Figure 13 The method can be applied to Figure 4 , Figure 10 and Figure 11 The visual calibration device 280 and / or shown Figures 2 to 4 The motherboard 210 in the multicolor 3D printing system 200 shown, the method 1300 includes the following steps:

[0107] S1310, in response to the printing command, moves the starting print head among N print heads to a preset calibration position to obtain a single-frame reference contour image including the print nozzle corresponding to the starting print head, and processes the single-frame reference contour image to obtain the reference coordinates of the starting print head.

[0108] In some embodiments of this application, the tool head controls the starting printhead to move to a preset calibration position (X_cal, Y_cal). After reaching the preset calibration position, the camera is activated to capture an image of the printhead corresponding to the starting printhead, obtaining a single-frame reference contour image. The pixel coordinates of the bottom and side contours of the printhead in the single-frame reference contour image are obtained by an algorithm and denoted as (X_p1, Y_p1, Z_p1).

[0109] Specifically, the single-frame reference contour image includes the outlet contour of the bottom surface of the printing nozzle and the side contour of the printing nozzle. The bottom contour of the printing nozzle can be reflected into the camera by a reflective element. The camera is positioned to the side of the printing nozzle, allowing it to simultaneously capture both the bottom and side contours. Target recognition and extraction are performed on the single-frame reference contour image to obtain the bottom and side contour regions of the printing nozzle.

[0110] Figure 14 This is a single-frame reference contour image of the printing nozzle in the embodiments of this application, such as... Figure 14 As shown, a contour shape, such as a circle, corresponding to the outlet at the bottom of the print nozzle is fitted from the bottom contour region. The pixel coordinates of its center are obtained through this fitted contour shape, which are the pixel coordinate values ​​of the print nozzle on the X and Y axes, denoted as (X_p1, Y_p1). The bottom position of the print nozzle in the side contour region is located, and the pixel coordinate value of the print nozzle in the Z axis direction is obtained, denoted as Z_p1. Thus, by combining the pixel coordinate values ​​of the print nozzle on the X, Y, and Z axes, the three pixel coordinates corresponding to the outlet of the print nozzle can be extracted from a single image to obtain the reference pixel coordinates. After completing the calibration of the print nozzle in the initial print head, the print nozzle can continue to heat up and start the printing task. Using the pixel coordinates of the print nozzle in the initial print head as the reference value, the position of subsequent print nozzles is calibrated.

[0111] Understandably, the position coordinates of the starting print head are used as reference coordinates for other print heads. Here, the starting print head is the first print head to start a print job during the printing process.

[0112] Optionally, when the camera is a 2D camera, Z_p1 is typically the minimum value of the printing nozzle in the vertical direction of the side contour region, i.e., the minimum value of the side contour region in the Y-axis direction. When the camera is a depth camera, the single-frame reference contour image is a depth map, and Z_p1 can be directly obtained from the acquired contour depth map, i.e., the depth value of the pixel corresponding to the lowest point of the printing nozzle. Furthermore, contour fitting is only an optional method; other image processing methods can also be used to obtain the center coordinates of the contour graphic, such as template matching. This involves using a preset contour graphic of known size to perform template matching with the bottom contour region to fit the contour graphic of the discharge port. For example, a circle of known diameter can be used to perform template matching with the bottom contour region to obtain the coordinates of the circle's center. This application does not impose any limitations on this method.

[0113] S1320, Move the i-th printhead among N printheads to a preset calibration position to obtain the i-th single-frame contour image including the print nozzle corresponding to the i-th printhead, and process the i-th single-frame contour image to obtain the coordinates to be calibrated of the i-th printhead; where 1≤i≤N, i and N are both positive integers, and N is a positive integer greater than 1.

[0114] In this embodiment, after the initial printhead finishes printing, the control tool head switches to the second printhead and moves the second printhead to a preset calibration position (X_cal, Y_cal) to acquire a second single-frame contour image including the print nozzle corresponding to the second printhead. The second single-frame contour image also includes the outlet contour of the bottom surface of the print nozzle corresponding to the second printhead and the contour of the side surface of the print nozzle. The acquisition method is the same as that of the initial printhead. The calibration process of the initial printhead is repeated to obtain the pixel coordinates to be calibrated of the print nozzle corresponding to the second printhead, denoted as (X_p2, Y_p2, Z_p2).

[0115] Understandably, all print nozzles need to be calibrated before printing, and the initial print head calibration position is used as a reference. Therefore, the description here is only an example. The i-th print head to be calibrated is not limited to the second print head. It is determined from the N print heads by responding to the printing task of printing material information of multiple colors in the printing instruction to select j print heads to be calibrated. It can be any one of the j print heads, which is determined by the printing instruction. Before printing with each print head, it is necessary to refer to the calibration process of the second print head to calibrate and obtain the corresponding pixel coordinates to be calibrated, which are denoted as (X_pi, Y_pi, Z_pi), where 1≤i≤j≤N, i and j are both positive integers, and j>1.

[0116] It should be understood that the visual calibration method provided in this application can be embedded in the system to switch between different printheads for multi-color printing, or it can be used before the first printing task of the multi-color 3D printing system is started. When the visual calibration method is embedded in the process of switching between multiple printheads, after starting the printing task with the starting printhead, the corresponding printhead of the starting printhead is heated by the heating module to save heating time. However, the heating temperature of the printhead must not exceed the melting temperature of the material before calibration is completed to prevent the printhead from prematurely ejecting material and blocking the printhead and reflective elements, which would affect the calibration. Alternatively, the printhead can be wiped before calibration. When the visual calibration method is used before the first printing task of the multi-color 3D printing system is started, it is not necessary to continue heating the printhead.

[0117] When a visual calibration method is embedded in the switching process of multiple printheads, for the initial printhead or the i-th printhead to be calibrated, when using the inner circle of the nozzle's outlet as the center coordinate to obtain the reference pixel coordinates or the pixel coordinates to be calibrated, the outlet may be obstructed by the filamentous material ejected after thermal melting, leading to inaccurate XY-axis pixel coordinates. Therefore, markers can be placed around the printhead to assist in fitting the coordinate points of the outlet, such as adding a concentric circle or other feature pattern around the printhead to improve calibration accuracy. Figure 15 As shown, the center of the printing nozzle 2403 includes an outlet 24031. Since the outlet 24031 is not easily positioned accurately, a marker 24032 can be placed around the printing nozzle 2403. The marker 24032 is coaxially arranged with the outlet 24031. The outline of the marker is extracted to obtain its center coordinates, which are then used as the XY coordinates of the nozzle outlet. The method for extracting the outline of the marker in this application is similar to or the same as the method for fitting the outline of the outlet as described above, and will not be repeated here. It should be understood that... Figure 15 For illustrative purposes only, the marker 24032 can be circular, square, or other shapes, as long as it can be coaxially set with the discharge port 24031.

[0118] S1330, calculate the coordinate offset of the corresponding printing nozzle of the i-th printing nozzle to be calibrated and the starting printing nozzle on the XYZ axes in the coordinate system of the multicolor 3D printing system based on the coordinates to be calibrated and the reference coordinates.

[0119] When the above process yields the pixel coordinates of the corresponding printing nozzle, it is necessary to convert them into the absolute scale of the space where the multicolor 3D printing system is located, so as to realize the conversion of the obtained pixel coordinate offset into the coordinate axis offset of the multicolor 3D printing system. Specifically, the difference between the pixel coordinates to be calibrated and the reference pixel coordinates is calculated; the absolute scales of the pixels in the reference single-frame contour image and the single-frame contour image on the XYZ axes of the multicolor 3D printing system coordinate system are determined respectively; the difference and the absolute scale are combined to obtain the coordinate offset of the printing nozzle of the i-th printing nozzle to be calibrated from the starting printing nozzle on the XYZ axes of the multicolor 3D printing system coordinate system.

[0120] In some embodiments, the absolute scale corresponding to a single pixel is related to the object distance, i.e., it is associated with the print head moving to a preset calibration position for image acquisition. This scale can be calculated using the camera's intrinsic parameters calibrated at the factory and the actual object distance. Therefore, a lookup table can be constructed by associating the preset calibration position of the print head with the absolute scale of a single pixel in the camera. That is, when the print head moves to the preset calibration position, the object distance between the side and bottom contours of the print nozzle and the camera is fixed, and the absolute scale of a single pixel can be obtained through the lookup table. In this application, since the side contour of the print nozzle does not need to pass through a reflective element, its imaging distance from the camera, i.e., its object distance from the bottom contour, is different, and consequently, the absolute scale corresponding to a single pixel is also different. Therefore, for the X and Y axes, the first absolute scale corresponding to a single pixel is denoted as L1_p; for the Z axis, the second absolute scale corresponding to a single pixel is denoted as L2_p.

[0121] It should be noted that if the camera, reflective element, and print nozzle are manufactured according to... Figure 10 and Figure 11The positions of the nozzles are arranged such that the bottom contour of the printing nozzles enters the camera through a reflective element for image acquisition. The pixels in the X-axis direction of the i-th single-frame contour image correspond to the offset of the printing nozzle on the Y-axis in the multi-color 3D printing system coordinate system. This means that the difference between the pixel values ​​of the to-be-calibrated pixel coordinates and the reference pixel coordinates in the X-axis direction needs to be calculated to determine the difference between the corresponding printing nozzle of the i-th printing nozzle to be calibrated in the Y-axis direction of the image. Similarly, the pixel values ​​in the Z-axis direction correspond to the offset of the nozzle on the Z-axis in the multi-color 3D printing system coordinate system. This means that the difference between the pixel values ​​of the to-be-calibrated pixel coordinates and the reference pixel coordinates in the Z-axis direction needs to be calculated to determine the difference between the corresponding printing nozzle of the i-th printing nozzle to be calibrated in the Z-axis direction of the image. In other words, when using pixel coordinate offset calibration, the offset in the X-axis direction of the image corresponds to the calibration of the printing nozzle in the Y-axis direction in the coordinate system of the multi-color 3D printing system, and the offset in the Y-axis direction of the image corresponds to the calibration of the printing nozzle in the X-axis direction in the coordinate system of the multi-color 3D printing system. The correspondence between the image and the coordinate system will be different under different arrangement methods, and this application does not impose any restrictions.

[0122] After obtaining the differences in the XYZ axes, it is necessary to combine the differences with the absolute scale to obtain the coordinate offset of the nozzle of the i-th printhead to be calibrated relative to the starting printhead in the XYZ axis of the multicolor 3D printing system coordinate system. This includes: using the reference pixel coordinates of the nozzle corresponding to the starting printhead as the reference value, calculating the offset Δx_i of the nozzle corresponding to the i-th printhead to be calibrated relative to the nozzle corresponding to the starting printhead in the X-axis of the system using the first absolute scale and the difference in the X-axis direction; calculating the offset Δy_i of the nozzle corresponding to the i-th printhead to be calibrated relative to the nozzle corresponding to the starting printhead in the Y-axis of the system using the first absolute scale and the difference in the Y-axis direction; and calculating the offset Δz_i of the nozzle corresponding to the i-th printhead to be calibrated relative to the nozzle corresponding to the starting printhead in the Z-axis of the system using the second absolute scale and the difference in the Z-axis direction, thus obtaining the coordinate offset (Δx_i, Δy_i, Δz_i) of the nozzle corresponding to the i-th printhead to be calibrated in the XYZ axis.

[0123] Taking the nozzle corresponding to the second print head as an example, using the reference pixel coordinates (X_p1, Y_p1, Z_p1) of the nozzle corresponding to the first print head as the baseline, the offset of the nozzle corresponding to the second print head from the nozzle corresponding to the first print head on the X-axis of the image is Δx_2 = (Y_p2 - Y_p1) * L1_p, the offset on the Y-axis is Δy_2 = (X_p2 - X_p1) * L1_p, and the offset on the Z-axis is Δz_2 = (Z_p2 - Z_p1) * L2_p. This yields the coordinate offsets (Δx_2, Δy_2, Δz_2) of the nozzle corresponding to the second print head on the XYZ axes in the multi-color 3D printing system coordinate system. The coordinate offsets of the nozzles corresponding to other print heads are calculated similarly, resulting in the coordinate offsets (Δx_i, Δy_i, Δz_i) of the nozzle corresponding to the i-th print head to be calibrated. In this way, the pixel coordinates can be transformed into the coordinate system of a multi-color 3D printing system with scale, and the coordinates of the printing nozzles corresponding to the printing head can be calibrated using the coordinate offset with scale.

[0124] S1340, use coordinate offset to calibrate the coordinates of the i-th printhead to be calibrated on the XYZ axes in the coordinate system of the multicolor 3D printing system, so as to start the printing task using the calibrated i-th printhead to be calibrated.

[0125] When the vision calibration method embedding system switches between different printheads for multi-color printing, taking the second printhead as an example, based on the coordinate offset of the corresponding nozzle of the second printhead, the second printhead is moved by the corresponding coordinate offset so that the coordinates of the corresponding nozzle of the second printhead coincide with the coordinates of the corresponding nozzle of the first printhead. Then, the printhead is heated to start the printing task, thereby ensuring that the second printhead can seamlessly combine with the printing layer of the previous printhead for printing; and so on, after the other printheads are calibrated, the coordinate offset value is added to the moved coordinate point before starting the printing task. When the visual calibration method is embedded in the multicolor 3D printing system before starting the first printing task, the reference pixel coordinates of the printing nozzle corresponding to the starting printing nozzle are used as the benchmark. The pixel coordinates to be calibrated of the printing nozzle corresponding to each printing nozzle to be calibrated are obtained sequentially, and the difference between the pixel coordinates to be calibrated of each printing nozzle to be calibrated and the benchmark value is calculated to obtain the coordinate offset. The coordinates of each printing nozzle to be calibrated are then calibrated, and the printing task is started using the starting printing nozzle and the calibrated printing nozzles to be calibrated.

[0126] Using the above visual calibration method, the height offset information between different nozzles and the horizontal offset information can be obtained from a single frame image, which is beneficial to improving the quality of 3D printing.

[0127] In another embodiment of this application, the printhead includes a stress sensor. The camera can also collect the coordinate offset of the printhead in the XY axis direction and the stress sensor can be used to obtain the coordinate offset of the printhead in the Z axis direction. Specifically, the vision calibration device also includes a Z-axis calibration block, which can be positioned beside the heated bed and moves along the Z-axis with the heated bed. Under the control of the tool head, the starting printhead moves to a preset calibration position (X_cal, Y_cal). The Z-axis calibration block is located below the preset calibration position. The camera acquires a bottom reference contour image of the printhead corresponding to the starting printhead to obtain the coordinate values ​​(X_p1, Y_p1) of the reference pixel coordinates on the XY axis. The specific acquisition method is similar to that described above and will not be repeated here. Simultaneously, the heated bed is slowly raised until the printhead corresponding to the starting printhead contacts the Z-axis calibration block located beside the heated bed and triggers the stress sensor inside the printhead. When the stress sensor located inside the starting printhead is triggered, the movement of the heated bed stops, and the height of the heated bed corresponding to the starting printhead is recorded, which is the coordinate value of the reference pixel on the Z-axis.

[0128] After obtaining the reference pixel coordinates of the print nozzles corresponding to the starting print head, the control tool head switches to the i-th print head to be calibrated and moves it to the preset calibration position. The same process as obtaining the XYZ axis coordinates of the reference pixel coordinates for the starting print head is repeated to obtain the calibrated pixel coordinates of the i-th print head to be calibrated. It should be understood that this embodiment can also be embedded in the system's switching between different print heads for multi-color printing, or it can be executed before the first printing task is started in the multi-color 3D printing system; this application does not impose any limitations on this.

[0129] Optionally, the offset values ​​of the X-axis and Y-axis between the reference pixel coordinates and the pixel coordinates to be calibrated can be obtained by combining the absolute scale as described above, which will not be repeated here. For the offset of the Z-axis, it is not necessary to combine the absolute scale, but to directly calculate the difference between the Z-axis coordinate value of the reference pixel coordinates of the print nozzle corresponding to the starting print head and the Z-axis coordinate value of the print nozzle corresponding to the i-th print head to be calibrated.

[0130] It should be understood that when using a stress sensor to obtain the Z-axis offset, the camera in the vision calibration device can be positioned at the bottom of the multicolor 3D printing system to acquire an image of the bottom contour of the printing nozzle. In this case, there is no need for a reflective element to reflect the bottom contour image to the side camera, and the X and Y axis offset values ​​of the printing nozzle can be obtained from the bottom contour image. However, when using a pressure sensor solution to raise the heated bed, there is a probability that the printing nozzle may touch the object model being printed. Therefore, care should be taken to avoid damaging the printed object model when using this solution.

[0131] In this embodiment of the application, the camera can also be used to identify the state of the printing nozzle and to identify whether there are abnormalities such as wear, blockage, or nozzle clogging.

[0132] In the embodiments of this application, the order of the above processes does not imply the order of execution, and not all of the above processes need to be executed. The execution order of each process and whether or not it is executed should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0133] This application also provides a computer-readable storage medium storing computer program code. When the computer program code is executed on the computer-readable storage medium, the computer-readable storage medium performs the above-described embodiments and... Figure 12 and Figure 13 The methods provided in [the document / platform].

[0134] This application also provides a chip, which includes a processor and a data interface. The processor reads instructions stored in the memory through the data interface and executes the method provided in this application.

[0135] Optionally, as one implementation, the chip may further include a memory storing instructions, and the processor is used to execute the instructions stored in the memory. When the instructions are executed, the processor is used to perform the methods provided in the embodiments of this application.

[0136] It should be understood that the processor in any of the above embodiments of this application can be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method embodiments can be completed by integrated logic circuits in the processor's hardware or by instructions in software form. The processor can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. The steps of the method disclosed in the embodiments of this application can be directly embodied in the execution of a hardware decoding processor, or by a combination of hardware and software modules in the decoding processor. The software modules can reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory; the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method.

[0137] Furthermore, the memory in any of the above embodiments of this application can be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. The non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be random access memory (RAM). By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0138] It should be understood that the formulas in the embodiments of this application are merely examples and are not intended to limit the scope of the embodiments of this application. The formulas can be modified, and these modifications should also fall within the scope of protection of this application.

[0139] It should also be understood that the various implementation methods described in this specification can be implemented individually or in combination, and the embodiments of this application are not limited in this respect.

[0140] Unless otherwise stated, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0141] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0142] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for automatically switching between multiple printheads, the method comprising: Applied to a multi-color 3D printing system including a hot bed, a single tool head and N printing heads, the printing heads comprising printing nozzles, the method comprising: acquiring a printing instruction, in response to a printing task of first printing material color information in the printing instruction, controlling the tool head to hold a starting printing head among the N printing heads and to move to a preset calibration position to acquire a reference pixel coordinate of the starting printing head; controlling the tool head to hold the starting printing head to above the hot bed, and to start the printing task of the starting printing head; after the starting printing head completes the printing task, in response to a printing task of i-th printing material color information in the printing instruction, controlling the tool head to hold an i-th to-be-calibrated printing head among the N printing heads and to move to the preset calibration position to acquire an i-th to-be-calibrated coordinate of the i-th to-be-calibrated printing head; wherein i∈[1, N], N is any positive integer greater than 1; calculating a coordinate offset of the i-th to-be-calibrated printing head relative to the starting printing head by using the reference coordinate and the i-th to-be-calibrated coordinate, and calibrating the coordinate of the i-th to-be-calibrated printing head by using the coordinate offset, so as to move the calibrated i-th to-be-calibrated printing head to above the hot bed to start the printing task.

2. A method for automatically switching between multiple print heads, the method comprising: Applied to a multi-color 3D printing system including a hot bed, a single tool head and N printing heads, the printing heads comprising printing nozzles, the method comprising: acquiring a printing instruction, in response to a printing task of multi-color printing material information in the printing instruction to determine a starting printing head and j to-be-calibrated printing heads from the N printing heads, wherein j∈[1, N], N is any positive integer greater than 1; controlling the tool head to hold the starting printing head and the j to-be-calibrated printing heads in turn to move to a preset calibration position to acquire a reference coordinate of the starting printing head and j to-be-calibrated coordinates of the j to-be-calibrated printing heads; calculating a coordinate offset of the j to-be-calibrated printing heads relative to the starting printing head by using the reference coordinate and the j to-be-calibrated coordinates respectively, and calibrating the coordinates of the j to-be-calibrated printing heads by using the coordinate offsets, to obtain calibrated j to-be-calibrated printing heads; in response to a printing sequence of the starting printing head and the j to-be-calibrated printing heads in the printing instruction, controlling the tool head to hold the starting printing head and the j to-be-calibrated printing heads in turn to move to above the hot bed to start the printing task.

3. The method according to claim 1 or 2, characterized in that, Before the acquiring of the printing instruction, the method further comprises: acquiring parking coordinates of the N printing heads and printing material color information of the N printing heads, in response to a printing task of printing material color information in the printing instruction to determine the parking coordinates of the printing heads, controlling the tool head to move to the parking coordinates of the corresponding printing heads for head holding and to move to a preset calibration position.

4. The method of claim 3, wherein, The multi-color 3D printing system further comprises a material tray loaded with N kinds of printing materials and a parking dock, and before acquiring the parking coordinates of the N printing heads and the printing material color information of the N printing heads, the method further comprises: The N printing nozzles are hung on the docking station, and the printing materials in the N material trays are respectively pushed into the N printing nozzles to form a plurality of printing channels with different colors; The nozzle aperture, corresponding printing material color, printing material wire diameter, printing material melting critical temperature and printing material melting optimum temperature of the N printing nozzles are configured to set the preset melting temperature of each printing nozzle.

5. The method of claim 3, wherein, The multi-color 3D printing system further comprises an extruder comprising a driving wheel and a driven wheel, the tool head comprises a clamping and fastening structure, and the starting printing nozzle or the printing nozzle to be calibrated comprises a hollow structure located on the upper side of the printing nozzle; wherein the control of the tool head moving to the docking coordinates of the starting printing nozzle or the printing nozzle to be calibrated for clamping and moving to a preset calibration position comprises: The tool head is controlled to move to the docking coordinates of the starting printing nozzle or the printing nozzle to be calibrated, and the printing nozzle is clamped and fastened by the clamping and fastening structure; The starting printing nozzle or the printing nozzle to be calibrated is moved to a preset calibration position, the driving wheel cooperates with the driven wheel to clamp and apply a downward force to the printing material in the hollow structure of the starting printing nozzle or the printing nozzle to be calibrated, so that the printing material is pushed towards the printing nozzle.

6. The method of claim 5, wherein, The docking station is provided with a position sensor, after the printing nozzle to be calibrated completes the printing task, the tool head is controlled to move the starting printing nozzle or the printing nozzle to be calibrated to the docking coordinates of the starting printing nozzle or the printing nozzle to be calibrated to hang the starting printing nozzle or the printing nozzle to be calibrated, comprising: The tool head is controlled to move the starting printing nozzle or the printing nozzle to be calibrated to the docking coordinates of the starting printing nozzle or the printing nozzle to be calibrated, and the clamping and fastening structure, the driving wheel and the driven wheel are released to hang the starting printing nozzle or the printing nozzle to be calibrated on the docking station; Whether the starting printing nozzle or the printing nozzle to be calibrated is successfully hung is judged by the position sensor on the docking station, if successfully hung, the tool head clamps the next printing nozzle; if not successfully hung, the starting printing nozzle or the printing nozzle to be calibrated is adjusted by re-clamping and releasing by the tool head or the starting printing nozzle or the printing nozzle to be calibrated is adjusted by manual adjustment.

7. The method according to claim 1 or 2, characterized in that, The multi-color 3D printing system comprises a visual calibration device, wherein when the visual calibration device comprises a camera, the reference coordinates are reference pixel coordinates, the coordinates to be calibrated are to-be-calibrated pixel coordinates, the reference pixel coordinates of the starting printing nozzle are obtained or the to-be-calibrated pixel coordinates of the printing nozzle to be calibrated are obtained, comprising: controlling the camera to capture a reference profile image or a profile image including a bottom and a side of a corresponding printing nozzle of the starting printing nozzle or the printing nozzle to be calibrated, identifying the corresponding printing nozzle of the starting printing nozzle or the printing nozzle to be calibrated from the reference profile image or the profile image to obtain a reference pixel coordinate (X_p1, Y_p1, Z_p1) or a pixel coordinate (X_pi, Y_pi, Z_pi) of the printing nozzle in a coordinate system of the multi-color 3D printing system; or, when the visual calibration device includes a camera and a Z-axis calibration block arranged beside the hot bed and below the preset calibration position, and each printing nozzle is internally provided with a stress sensor, obtaining the reference coordinate of the starting printing nozzle or the pixel coordinate to be calibrated of the printing nozzle to be calibrated, comprising: controlling the camera to capture a reference profile image or a profile image including a bottom of a corresponding printing nozzle of the starting printing nozzle or the printing nozzle to be calibrated, identifying the corresponding printing nozzle of the starting printing nozzle or the printing nozzle to be calibrated from the reference profile image or the profile image to obtain a reference pixel coordinate (X_p1, Y_p1) or a pixel coordinate (X_pi, Y_pi) of the printing nozzle in a coordinate system of the multi-color 3D printing system; controlling the hot bed to be lifted until the corresponding printing nozzle of the starting printing nozzle or the printing nozzle to be calibrated contacts the Z-axis calibration block and triggers the stress sensor inside the printing nozzle, stopping the movement of the hot bed when the stress sensor is triggered, and recording the lifting height corresponding to the hot bed as a Z_p1 coordinate value of the reference pixel coordinate or a Z_pi coordinate value of the pixel coordinate to be calibrated.

8. The method of claim 1 or 2, wherein, The printing nozzle or the tool head includes a heating module and a temperature measuring assembly, or the printing nozzle integrates part of the heating module and the temperature measuring assembly, and the tool head integrates the other part of the heating module and the temperature measuring assembly; wherein, before the starting printing nozzle or the printing nozzle to be calibrated starts a printing task, the corresponding printing nozzle of the starting printing nozzle or the printing nozzle to be calibrated needs to be heated to a preset melting temperature, comprising: powering the heating module and the temperature measuring assembly, heating the corresponding printing nozzle of the starting printing nozzle or the printing nozzle to be calibrated by the heating module, and combining the temperature measuring assembly to detect the temperature information of the printing nozzle in real time; using the temperature information to reversely control the heating state of the printing nozzle by the heating module, so that the printing nozzle accurately reaches the preset melting temperature; synchronously heating the hot bed, and starting the printing task of the starting printing nozzle or the printing nozzle to be calibrated after the printing nozzle and the hot bed both reach the expected temperature.

9. The method of claim 8, wherein, The tool head includes a PCB board and / or the multi-color 3D printing system includes a main board, the heating module and the temperature measuring assembly are powered through the PCB board or the main board, and before the heating state of the printing nozzle by the heating module is reversely controlled using the temperature information, the method further comprises: Whether the heating module and / or temperature measuring component is in a normal state or not is determined by whether the PCB or the mainboard can read the temperature information of the printing nozzle in real time; If the heating module and / or temperature measuring component is in a normal state, the temperature information is used to reversely control the heating state of the printing nozzle; if the heating module and / or temperature measuring component is not in a normal state, the circuit connection between the heating module and / or temperature measuring component and the tool head or the mainboard needs to be detected.

10. The method of claim 1 or 2, wherein, The multi-color 3D printing system further comprises a wiping structure, before the tool head drives the starting printing nozzle or the printing nozzle to be calibrated to above the hot bed, the method further comprises: controlling the tool head to clamp the printing nozzle to the wiping structure, so that the printing nozzle corresponding to the printing nozzle touches the wiping structure to clean the residual consumables of the printing material in the historical printing task by friction; or, controlling the printing nozzle to move above the wiping structure to perform preliminary printing to remove the residual consumables on the printing nozzle, and then move above the hot bed to perform formal printing.

11. A multi-color 3D printing system, characterized by, The multi-color 3D printing system comprises a hot bed, a single tool head, a plurality of printing nozzles, a plurality of material trays and a mainboard, wherein: The plurality of material trays are loaded with different colors of printing materials respectively, and the printing materials on each material tray are sent into each printing nozzle respectively, so that the plurality of printing nozzles and the plurality of material trays form a plurality of printing channels with different colors one by one; The tool head is used to selectively clamp or release one of the plurality of printing nozzles for movement, and each printing nozzle corresponds to a printing nozzle on the lower side; The mainboard is used to obtain a printing instruction and execute the method of any one of claims 1-10 to control the hot bed, the tool head and one or more of the plurality of printing nozzles to print a 3D printing object on the hot bed.

12. A computer storage medium, characterized in that The computer readable storage medium stores computer program code, when the computer program code runs on the computer readable storage medium, the method of any one of claims 1-10 is executed. The computer readable storage medium stores computer program code, when the computer program code runs on the computer readable storage medium, the method of any one of claims 1-10 is executed.

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