Multi-galvanometer and double-scraper partition SLM 3D printing cooperative control system and method thereof

Abstract

The invention discloses an SLM 3D printing cooperative control system with multiple galvanometers and double scraper partitions and a method of the SLM 3D printing cooperative control system. The system comprises a left forming area and a right forming area which are physically independent, double-scraper assemblies which are correspondingly and independently driven, and multi-galvanometer scanning units which are arranged in a longitudinal line. An upper computer establishes an asynchronous parallel mechanism of laser scanning and powder laying actions through a partition time sequence collaborative scheduling module: when laser scanning is carried out on a region on one side, the region on the other side is synchronously driven to execute powder laying and layer thickness reduction, and circulation and alternation are carried out so as to minimize laser waiting time. Aiming at large incident angle light spot distortion caused by longitudinal arrangement, a dynamic correction module is arranged in the system, the laser power, the scanning speed and the dynamic focusing focal length are adjusted in real time based on the incident angle, and an airflow disturbance model is combined to carry out anti-interference cooperative control on a scraper and laser. According to the invention, the printing efficiency is obviously improved while the forming quality of a large picture is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal additive manufacturing and industrial automation control, in particular to a multi-mirror and double-blade partitioned SLM 3D printing collaborative control system and method thereof. BACKGROUND

[0002] With the increasing demand for large-size and integrated complex metal components in the fields of aerospace, energy power and automobile manufacturing, metal additive manufacturing equipment based on selective laser melting (SLM) technology is rapidly evolving towards ultra-large forming width and multi-laser collaborative operation. In order to meet the manufacturing needs of meter-size parts and ensure printing efficiency, the equipment usually adopts multi-mirror splicing scanning and double-direction / double-zone powder laying architecture.

[0003] In the attempt to improve the forming width, a common architecture is to arrange multiple mirror units in a vertical column along the depth direction of the forming chamber. However, this layout, while expanding the width, also poses serious optical challenges. Unlike the traditional central radiation layout, the vertical column arrangement results in a significant increase in the incidence angle of the laser beam when scanning to the far end edge of the forming width, especially on the two sides perpendicular to the arrangement direction. According to the principle of optical imaging, large-angle incidence will cause geometric distortion of the laser spot projected on the powder bed plane, stretching from a standard circle to an ellipse. This change in spot shape not only causes the melt pool to widen and the dimensional accuracy to decrease, but more seriously, it causes the energy density in the unit area to decay sharply, resulting in insufficient density or decreased metallurgical performance in the edge area of the formed part. In addition, the severe change in optical path difference also causes the focal plane to separate from the working surface, resulting in defocusing. The existing general control system often does not configure high-order spot dynamic correction and energy compensation algorithms for this vertical column large-width architecture, making it difficult to ensure consistent quality across the entire width.

[0004] On the other hand, in the optimization of powder laying efficiency, although existing devices begin to be equipped with a double-blade system to address the time-consuming problem of large-area powder laying, the control logic usually adopts a serial processing method. Most systems only use the double-blade as a physical extension and still use a scanning-powder laying serial logic or a simple static mutual exclusion mechanism in control. That is, when one side is laying powder, the laser is often in a complete stop state waiting for the powder laying to be completed in order to prevent mechanical interference or vibration. For large-size devices, the single-layer powder laying time can be tens of seconds, and this frequent laser waiting causes the laser system to be in an idle state for a considerable part of the entire printing cycle, severely restricting the upper limit of the device's productivity. At the same time, if the high-speed running double-blade is not configured with a fine air flow field management, the turbulence generated by it can easily interfere with the adjacent working laser thermal field, causing thermal lens effect or dust defects.

[0005] Therefore, it is urgent to develop a control system capable of deeply adapting to the optical characteristics of longitudinal multi-mirror and realizing the full-time asynchronous cooperation of double doctor blades and multiple lasers through timing overlap logic, so as to maximize the printing efficiency under the premise of ensuring the large-format printing precision. SUMMARY

[0006] The application aims to provide a multi-mirror and double doctor blade partitioned SLM 3D printing cooperative control system and method to solve the problems pointed out in the background art.

[0007] In a first aspect, the application provides a multi-mirror and double doctor blade partitioned SLM 3D printing cooperative control system, The system comprises an upper computer interactive control unit, a lower computer real-time motion control unit, a multi-mirror laser scanning unit and a forming chamber actuator; The forming chamber actuator is divided into a left forming area and a right forming area which are independent of each other in physical space, the left forming area is provided with an independently driven first forming cylinder and a first doctor blade assembly, and the right forming area is provided with an independently driven second forming cylinder and a second doctor blade assembly; The multi-mirror laser scanning unit comprises at least one group of mirrors arranged in a longitudinal or matrix arrangement, and the scanning range covers the left forming area and the right forming area; The upper computer interactive control unit is provided with a partitioned timing cooperative scheduling module, which is configured to execute the following cooperative control logic: Establish a timing overlap mechanism: divide the printing process into laser scanning period and powder laying and falling period, and establish an asynchronous job queue for the left and right areas; Perform asynchronous alternating control: when the multi-mirror laser scanning unit concentrates on laser scanning processing of the left forming area, the system synchronously drives the second doctor blade assembly to perform powder laying and falling actions in the right forming area in parallel, and controls the second forming cylinder to complete the layer thickness reduction; When it is monitored that the left forming area scanning is completed and the right forming area powder laying is ready, the system controls the multi-mirror laser scanning unit to seamlessly switch to the right forming area for laser scanning processing, while synchronously driving the first doctor blade assembly to perform powder laying and falling actions in the left forming area in parallel, and controlling the first forming cylinder to complete the layer thickness reduction; The system cyclically executes the above alternating process to minimize the idle time of the laser waiting for powder.

[0008] Optionally, the multi-mirror laser scanning unit adopts a longitudinal arrangement, and in order to solve the problems of large incidence angle of laser beams at the edge of the forming surface and spot elliptical caused by longitudinal arrangement, the system is provided with a large-format spot distortion dynamic correction module. The correction module is configured to: based on the geometric relationship between the galvanometer center coordinates and the current scanning point coordinates, calculate the incident angle of the laser beam in real time; according to the incident angle, dynamically focus compensation and spot shape correction of the laser spot are carried out through the galvanometer control algorithm, so that the energy density of the laser beam in the full width of the forming surface is maximally consistent; at the same time, combined with the laser offset algorithm, micron-level position compensation is carried out on the scanning path to correct the geometric distortion caused by the incident angle.

[0009] Optionally, the lower computer real-time motion control unit comprises a double-independent scraper path planning module. The first scraper assembly and the second scraper assembly have independent powder taking positions, powder dropping positions and waste powder recycling positions respectively; during cooperative control, the system monitors the position state of the double-sided scrapers in real time, and ensures that when a single scraper enters its corresponding forming area to perform powder laying action, the other side area is in laser scanning or waiting state, and the actions of the two sides do not interfere with each other in physical space through logical interlocking.

[0010] Optionally, the partition time sequence cooperative scheduling module further comprises dynamic load balancing and pre-waiting logic. If the laser scanning time of one side area is less than the powder laying action time of the other side area, the system controls the laser scanning unit to enter a microsecond-level standby state after completing the scanning of the current side, until receiving a powder laying completion signal of the other side; If the laser scanning time of one side area is greater than the powder laying action time of the other side area, the system controls the scraper of the side that has completed powder laying to stop at a preset safe waiting position, and activates the action of the next level immediately after receiving a laser scanning switching signal.

[0011] Optionally, the large-format spot distortion dynamic correction module further comprises laser energy-speed dynamic coupling compensation logic. For the change of optical path difference caused by longitudinal arrangement, the system establishes an optical path-energy attenuation model; during scanning, the output power of the laser or the jump speed of the galvanometer is dynamically adjusted according to the real-time optical path length and spot deformation rate, to ensure the consistency of the metallurgical properties of the formed parts in different areas.

[0012] Optionally, the scanning area of each galvanometer of the multi-galvanometer laser scanning unit covers a set range of areas in the front-rear direction, and covers the complete left forming area or right forming area in the left-right direction, so as to realize large-format coverage through longitudinal splicing of multiple galvanometers.

[0013] Optionally, the lower computer real-time motion control unit is further configured to control the forming cylinder shaft and the powder cylinder shaft. For the powder cylinder shaft, the system calculates the upper limit position alarm position in real time according to the stroke parameter and the preset minimum powder threshold; when the feedback position of the powder cylinder shaft reaches the upper limit position alarm position, the powder shortage early warning is triggered; the system supports configuring the acceleration and deceleration parameters of the S-shaped speed curve for the motor shaft, so as to smooth the mechanical vibration when the shaft starts and stops.

[0014] Optionally, the multi-mirror laser scanning unit is configured with a mirror geometry correction module; The mirror geometry correction module is used for reading a preset mirror correction file, and the file includes an X-direction proportional coefficient, a Y-direction proportional coefficient and a coordinate rotation angle parameter; the system performs real-time coordinate transformation and pillow distortion compensation on the scanning instruction of the mirror group according to the parameters.

[0015] Optionally, the system further comprises a power-off continuous printing and state recovery module; The module is configured to record the current printing layer number, the mirror scanning index pointer and the state of each shaft position in the non-volatile memory in real time during the system operation; when the system abnormal power-off or the automatic shutdown program is monitored, the breakpoint recording information is read at the next start, and each motion component is reset to the safe position and the cooperative control logic is recovered.

[0016] In the second aspect, the embodiment of the present application provides a multi-mirror and double-blade partitioned SLM 3D printing cooperative control method based on the system of any one of the first aspect, and the method comprises the following steps: Step S1: system initialization, dividing the forming platform into independent left and right work areas, and resetting the left and right forming cylinders and scraper assemblies; Step S2: reading slice data, planning a scanning path according to the multi-mirror vertical layout, and applying a light spot distortion correction algorithm to generate a corrected scanning instruction; Step S3: entering a cooperative working cycle: State A: controlling the multi-mirror laser scanning unit to scan and form the left work area; at the same time, controlling the right forming cylinder to descend one layer and driving the second scraper assembly to complete the powder taking, powder laying and powder falling actions; State switching: monitoring the left and right task states, and switching to state B when the left scanning is completed and the right powder laying is ready; State B: controlling the multi-mirror laser scanning unit to scan and form the right work area; at the same time, controlling the left forming cylinder to descend one layer and driving the first scraper assembly to complete the powder taking, powder laying and powder falling actions; Step S4: repeating step S3 until the printing task is completed.

[0017] The present application has the following beneficial effects: The physical interface asynchronous cooperation is realized, and the equipment safety and time efficiency are improved. The system can allow the double scrapers to independently and high-speed run in the non-interference area under the premise of ensuring the physical safety by constructing the dynamic virtual fence which is mapped with the physical space in real time in the memory and combining the interlocking scheduling of the FPGA hardware bottom, the interlocking waiting time is maximally compressed, and the asynchronous parallel operation is realized.

[0018] The airflow disturbance model based on fluid mechanics is introduced, and the spatial correlation of the scraper speed, turbulent flow radius and laser scanning area is established. Through the dynamic avoidance logic, the system can force the scraper to slow down to the laminar flow threshold or suspend the scanning task when passing through the laser scanning area, avoid the thermal lens effect and powder dust problem caused by airflow disturbance, and ensure the consistency of the organization performance of the complex workpiece at the partition interface.

[0019] Relying on the parallel long guide rail design throughout the forming chamber and the abnormal interruption adaptive takeover module, when the unilateral scraper fails, the system can automatically cut off the fault source and correct the stroke parameters of the normal side scraper to cover the full width, and through the degradation operation strategy, the continuity of the printing task can be maintained, and the printing task failure can be avoided.

[0020] Through the segmented control of the pre-docking position parameters, the long-distance empty moving time of the scraper is hidden in the laser scanning time, the seamless connection of scanning and powder laying is realized. Meanwhile, the dynamic load balancing calculation can flexibly adjust the logical boundary according to the actual geometric distribution of each layer slice, balance the work load of the multi-vibrating mirror, and minimize the waste of laser resources caused by fixed partition.

[0021] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the application. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims hereof.

[0022] The technical solutions of the present application will be further described in detail below with the help of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application together with the embodiments, and are used to explain the present application, and do not constitute a limitation on the present application. In the drawings: Figure 1 The system hardware architecture and partition layout schematic diagram provided for the embodiments of the present application; Figure 2 The collaborative control method logic flowchart provided for the embodiments of the present application. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0025] Example 1: This embodiment provides a collaborative control system for SLM (Selective Laser Melting) 3D printing with multiple galvanometers and dual scraper partitions.

[0026] like Figure 1 As shown, the collaborative control system consists of four parts: an upper computer interactive control unit, a lower computer real-time motion control unit, a multi-mirror laser scanning unit, and a molding chamber actuator. They are connected through a high-speed industrial fieldbus (such as EtherCAT) and achieve data interaction and action synchronization through a layered protocol stack.

[0027] The forming chamber actuator is physically and logically divided into a left forming area and a right forming area. To support this efficient left-right partitioned operating architecture, the system is equipped with two completely independent forming cylinder drive mechanisms, corresponding to the left and right forming areas respectively. Both are independently controlled by the lower-level machine, enabling independent layer thickness reduction actions. Simultaneously, the system features physically separate and independently driven first and second scraper assemblies. The first scraper assembly is located on one side of the forming chamber (e.g., the left side), equipped with an independent drive motor and guide rail system, and its effective stroke strictly covers the left forming area and the corresponding powder drop / recovery position. The second scraper assembly is located on the other side of the forming chamber (e.g., the right side), also equipped with an independent drive motor and guide rail system, and its effective stroke strictly covers the right forming area and the corresponding powder drop / recovery position. The first and second scraper assemblies are physically independent and incompatible, lacking full-width cross-coverage capability in terms of mechanical stroke; that is, the left scraper does not cover the right area, and the right scraper does not cover the left area. This design simplifies the mechanical structure, avoids the cumulative error of ultra-long guide rails, and ensures a high response speed for powder spreading in a single area.

[0028] The multi-mirror laser scanning unit is arranged in a vertical manner (front-back direction) instead of a horizontal manner as in conventional devices. The optical assembly includes four (or more) laser scanning mirror units arranged in sequence along the depth direction (Y-axis / front-back direction) of the forming chamber. The optical scanning range of each mirror unit is configured to cover a set of area strips in the front-back direction (Y-axis) and the entire left or right forming area in the left-right direction (X-axis). To address the optical challenges that may arise from the vertical arrangement, such as the significant increase in laser incidence angle when the laser beam scans to the left and right edges of the forming surface (especially away from the center of the mirror), the system includes a dynamic focusing unit and a spot distortion dynamic correction module integrated with the host computer. By adjusting the focal length and mirror deflection in real time, the system can correct the spot shape and ensure the uniformity of the full-width energy density. It is particularly worth mentioning that, in order to support the dynamic load balancing and partition splicing functions described in subsequent embodiments, the multi-mirror laser scanning unit is configured in the optical design as follows: the mirror group responsible for scanning the left forming area and the mirror group responsible for scanning the right forming area have a physical overlap area with a predetermined width (e.g., 40-60 mm, covering the center line on both sides) at the center dividing line of the forming chamber. In this physical overlap area, both the left and right mirror groups have effective optical coverage and focusing accuracy. In addition, to avoid light path obstruction caused by vertical arrangement, each mirror unit adopts a Z-axis staggered mounting structure, with the optical exit point of the rear mirror higher than that of the front mirror, and a large focal depth F-Theta field lens is used to ensure that the scanning light paths do not interfere with each other in physical space.

[0029] The host computer interaction control unit runs on a high-performance industrial control computer and is responsible for slice data analysis, path planning algorithm generation for vertical multi-mirror, spot distortion correction operation, and global cooperative scheduling. The host computer has a partition timing cooperative scheduling module configured to perform the core timing overlap control logic: establishing an asynchronous parallel mechanism for laser scanning period and powder laying and falling period. Specifically, when the multi-mirror laser scanning unit concentrates on laser scanning processing of the left forming area, the host computer instructs the slave computer to synchronously drive the second scraper assembly to perform powder laying and falling actions in the right forming area, and controls the right forming cylinder to complete the layer thickness reduction; once it is monitored that the left forming area scanning is completed and the right forming area powder is ready, the system immediately controls the multi-mirror laser scanning unit to seamlessly switch to the right forming area for laser scanning processing, while synchronously driving the first scraper assembly to perform powder laying and falling actions in the left forming area.

[0030] The lower machine real-time motion control unit is responsible for receiving the macro instruction issued by the upper machine and converting it into pulse / direction signals for controlling the motor driver. The lower machine performs microsecond-level real-time control on the left and right scraper motors and the two forming cylinder motors, and processes the limit and interlock signals of various sensors to ensure that the left and right regions perform high-frequency and high-precision asynchronous actions in a physically isolated state.

[0031] Embodiment Two: Further, during the SLM printing process, the metal powder particles are extremely small (usually between 15-53 microns) and are extremely susceptible to air flow and can be blown away. At the same time, high-power lasers produce metal vapor and condensate when melting metal, and these fumes need to be discharged through the air field system. If the scraper moves at high speed in the forming chamber, its leading edge will push the air to form strong turbulence. This turbulence, if it affects the area where the laser is melting, will cause two problems: one is to blow away the unmelted powder bed, resulting in uneven powder laying or lack of powder; the second is to interfere with the protective gas layer flow on the laser light path, causing local gas density changes, which in turn produces a thermal lens effect, causing the laser focal spot to deform or the focal point to shift, which seriously affects the density and surface quality of the printed part.

[0032] To this end, the dynamic avoidance logic of the system is configured to perform the following operations: The system first pre-establishes or imports an air flow disturbance model based on the principles of fluid mechanics. This model is a mathematical function whose input quantities include the current motion speed of the scraper, the windward area of the scraper, and the gas circulation wind speed in the forming chamber; the output quantity is the air flow turbulence radius generated by the leading edge of the scraper (i.e., the distance of the air flow affected area). During the printing process, the system real-time collects the current motion speed of the first scraper assembly or the second scraper assembly. Based on the above model, the system real-time calculates the air flow turbulence radius under the current speed, and dynamically generates an air flow disturbance area that moves with the scraper in the global virtual coordinate system. The specific calculation formula is: wherein is the turbulence radius, is the real-time speed of the scraper, is the diffusion coefficient based on the fluid viscosity (e.g., 0.15 s), is the basic safety margin (e.g., 20 mm). At the same time, the system also real-time acquires the current scanning coordinates of the multi-vibrating mirror laser scanning unit (i.e., the position of the laser spot). Among them, is not a fixed value, but a dynamic variable that is negatively related to the system's real-time monitoring of the forming chamber gas circulation wind speed . The system has a pre-set wind speed-diffusion coefficient table, and when the circulating wind speed fed back by the sensor is high (fume dissipation is fast), the system automatically adjusts the diffusion coefficient The value is adjusted upwards if the value is lower; conversely, it is increased if the value is lower. The system inputs the current scraper speed at a frequency of 1kHz. With the revised Value, real-time calculation of dynamic turbulence radius This allows for the construction of precise electronic fences.

[0033] When the system detects a working galvanometer scanning spot within the area covered by the airflow interference zone, the system will take action according to a preset priority strategy, as follows: Strategy 1 (Quality Priority Mode): If the laser scan is of a critical contour or delicate thin-walled structure of a part, to ensure metallurgical quality, the system will send a command to suspend the scanning task of the corresponding galvanometer group. Specifically, the laser immediately shuts off its output, the galvanometer stops rotating and records the current vector position. The scanning will only resume automatically from the breakpoint after the scraper assembly and its associated airflow interference zone have completely moved out of the scanning area and the airflow has stabilized (typically with an additional stabilization delay of several hundred milliseconds).

[0034] Strategy Two (Efficiency-First Mode): If the laser scans an internal filling area or support structure with low airflow sensitivity, the system can forcibly reduce the movement speed of the scraper assembly on that side to below the laminar flow threshold. The laminar flow threshold refers to the experimentally determined maximum speed at which airflow maintains a stable laminar flow state without generating severe turbulence. By reducing the scraper speed, the airflow disturbance radius is reduced, allowing the scraper to pass through simultaneously with the laser scan. Although this sacrifices a slight powder spreading speed, it avoids laser interruptions and maintains the continuity of the overall thermal field.

[0035] Example 3: In traditional dual-laser or multi-laser printing systems, the partitioning is often fixed (e.g., a 50% / 50% physical centerline division). However, the actual shapes of printed models are mostly different, and there may be situations where the left side needs to be scanned for a very large area, while the right side is very small. Fixed partitioning means that after the right-side laser and squeegee complete their work in a very short time, they must remain idle for a long time while waiting for the left side to finish, resulting in a serious waste of laser resources and time resources.

[0036] The system's partitioned collaborative scheduling module is configured to perform dynamic load balancing calculations before the start of each layer's printing task (typically during the toner return journey of the previous layer). The system first reads the slice data of the current layer (usually in CLI or SLC format) and parses out all scan vector paths. Then, the system calculates the total scan vector length (or total estimated time) in the left region and the total scan vector length in the right region under the default partitioning settings. Combining this with the set process parameters (such as scan speed, jump delay, and on / off light delay), the system accurately calculates the estimated job time for both the left and right sides. Estimated job time ,in For vector length, For scanning speed, For jump delay, This represents the number of redirects.

[0037] When the calculated difference in estimated job times between the left and right sides exceeds a preset efficiency threshold (e.g., a time difference exceeding 5% or an absolute time difference exceeding 10 seconds), the system determines that the current load is severely unbalanced. At this point, the system initiates a dynamic adjustment algorithm. Within the physical range of the overlap buffer (typically determined by the optical coverage limit of the galvanometer, e.g., 20mm to the left and right of the center line), the system shifts the logical boundary line towards the side with the shorter job time, in preset steps (e.g., 1mm). During this shift, some of the overlapping scan vectors originally belonging to the high-load area (e.g., the left side) are reassigned to the galvanometer group in the low-load area (e.g., the right side). The system iteratively executes this assignment process and recalculates the estimated job times on both sides after the shift, until the difference in job times between the two sides is minimized, or the logical boundary line reaches the physical edge of the overlap buffer. After determining the new boundary line, the system performs vector trimming and stitching on parts crossing the new boundary line to ensure the integrity of the scanning task. Through this dynamic adjustment, the system can ensure that the first and second galvanometer groups complete the scanning task as simultaneously as possible, thereby reducing the waiting time for each layer and improving the overall printing efficiency.

[0038] Example 4: In practical applications, to maximize efficiency, it's crucial to optimize not only scanning time but also the toner spreading time. Traditional toner spreading typically involves moving from the origin to the destination and back to the origin without interruption. However, in multi-laser collaborative systems, situations may arise where laser scanning on one side is complete and toner spreading is needed immediately, but overlapping areas or the other side may be restricted. Alternatively, to reduce the waiting time for laser toner spreading, the scraper can be pre-positioned to be closest to the working area.

[0039] Therefore, the lower-level machine of this system has a built-in motor shaft parameter configuration module. This module allows the user or the upper-level machine to configure the pre-stop position parameters for the first and second scraper assemblies respectively. This is defined as the physical coordinate position of the scraper from the origin to a specified intermediate waiting point. This intermediate position is usually set at the edge of the forming cylinder, that is, the critical point where powder spreading is about to begin but before entering the forming zone.

[0040] In the control logic for executing the powder spreading action, the system first detects the laser scanning task status of the corresponding area. If the laser scanning task of the corresponding area (or associated overlapping area) is not yet completed, in order to save subsequent time, the lower-level real-time motion control unit will drive the scraper to quickly move to the position corresponding to the pre-stop position parameter at a preset first speed (Speed ​​1, usually high-speed movement in non-working state), and maintain the servo lock (position lock) state at this position, entering the pre-powder spreading mode. At this time, the scraper is actually ready. Once the upper-level computer receives the laser output completion signal and confirms that the safety interlock is released, it will immediately send a continue command to the lower-level computer. The lower-level computer does not need to perform a long-distance acceleration process, but immediately drives the scraper to start from position V1 and complete the remaining powder spreading action at a preset second speed (Speed ​​2, usually the precision powder spreading speed required by the process, which must ensure powder flatness). This segmented control logic (from fast forward to waiting position to waiting and then to powder spreading at the process speed) masks the return and feed time of the scraper within the laser scanning time, reducing the idle time of the laser waiting for the scraper to arrive.

[0041] Example 5: In traditional single-galvanometer or transversely parallel dual-galvanometer systems, the incident angle of the laser beam is relatively small, and changes in the spot shape are often ignored. However, in the four-galvanometer (or more) longitudinal arrangement architecture used in this system, in order to cover the ultra-long forming area, the angle between the laser beam and the powder bed plane increases significantly when the galvanometers at the edge of the array scan the far end of their field of view (especially the extreme positions on the left and right sides). This large incident angle physically causes the laser spot projected onto the working surface to be stretched from a standard circle to an ellipse. The change in spot shape will cause two serious process problems: first, the laser energy density per unit area decreases as the spot area increases, resulting in insufficient melting of the metal powder in the edge area and producing incomplete fusion defects; second, the effective melting width of the spot in the long axis direction increases, resulting in deviations in the part contour dimensions.

[0042] To address the aforementioned issues, the control system in this embodiment incorporates a real-time compensation algorithm based on an optical geometric model. The system first establishes a three-dimensional geometric mapping table in memory between the center point of the galvanometer and each pixel on the forming plane. During scanning, the control algorithm calculates the incident angle θ of the current laser beam and the theoretical deformation rate of the light spot in real time. Based on this calculation, the system performs dynamic coupling compensation of laser energy and velocity: when the laser beam moves towards a large angle region, the system dynamically increases the output power of the laser through the FPGA high-speed interface according to the increase ratio of the light spot area. Alternatively, reduce the scanning jump speed of the galvanometer proportionally. To maintain the energy density received per unit area of ​​the molten pool Constant. Its control logic follows the energy density formula. ,in For laser power, For scanning speed, This refers to the scanning spacing. It is dynamically adjusted. and The ratio of the two values ​​allows the system to offset the energy attenuation caused by the deformation of the light spot, thereby ensuring that the formed part has consistent metallographic properties at the center and edge of the surface.

[0043] Furthermore, to address the dimensional accuracy issues caused by ellipticized laser spots, this embodiment also incorporates a dynamic laser offset compensation algorithm. During fine contour scanning, the system no longer uses a fixed spot radius compensation value. Instead, it calculates the effective spot width in real-time based on the angle between the spot's major axis and the scanning vector direction, and dynamically adjusts the offset of the scanning path. For example, when the major axis of the elliptical spot is perpendicular to the scanning direction, the system automatically increases the path indentation to compensate for the widened melt path width. Simultaneously, in conjunction with the dynamic focusing unit in the optical components, the system drives the dynamic focusing lens to move at a microsecond-level response speed based on the real-time calculated optical path difference (Z-axis distance), fine-tuning the focal length in real-time to suppress defocus and astigmatism at the physical optics level, controlling the ellipticity of the spot within the threshold range allowed by the process. Through the deep collaboration between the aforementioned software algorithm and optical hardware, this system effectively overcomes the optical distortion challenges brought about by vertical column arrangement, achieving high-precision, consistent printing across the entire large-format field.

[0044] Furthermore, in response to the physical phenomenon of spot ellipticization caused by large incident angles, this embodiment adopts an energy-focusing dual coupling compensation strategy.

[0045] First, execute Z-axis dynamic focus locking. The system establishes a full-field optical path mapping model. ( The coordinates of the current scanning point relative to the center of the galvanometer are: (The vertical distance from the center of the galvanometer to the forming plane) is used to drive the dynamic focusing unit to move along the optical axis in real time via a lookup table using the FPGA. This ensures that the focus always falls precisely on the powder bed plane. While this cannot physically change the geometric ellipticity produced by large-angle projection, it prevents defocusing of the light spot due to field curvature, keeping the light spot at the diffraction limit size at the current angle.

[0046] Second, perform dynamic energy density compensation. (Light spot area) With the angle of incidence Increase and approximately according to Proportional stretching. To maintain a constant energy density per unit area of ​​the molten pool, the system dynamically adjusts the laser output power based on the following nonlinear gain model. : ; in, As the reference power, This is the area stretching compensation coefficient (value ranges from 0.8 to 1.0). This is the lens transmittance attenuation compensation coefficient. This algorithm ensures that even in the edge regions where the light spot becomes elliptical, the input energy density remains largely consistent with the central circular light spot region.

[0047] Example 6: The process package file is a core data set stored in a local database or encrypted file system, containing customized parameters for different metal materials (such as titanium alloys, aluminum alloys, stainless steel, etc.). The laser strategy data defines microscopic physical parameters such as laser power (determining the molten pool depth), scanning speed (determining the molten pool width and stability), laser-on delay (compensating for laser response lag), laser-off delay (preventing overheating at the end), and jump delay (stabilization time during galvanometer idle movement).

[0048] The filling strategy data defines the macroscopic scan path planning. This system adopts a partition-independent strategy when generating the scan command stream. The system associates the left and right forming areas with independent process parameter groups. In R&D mode, users can even conduct comparative experiments using different parameters on the left and right sides. In normal production mode, to address the mechanical performance seam problem at the splicing of multiple galvanometers, the system generates a special scan path within the overlap buffer based on the filling strategy data. Specifically, the system does not directly truncate the scan lines of the left and right galvanometers on a straight line, but instead generates non-linear sawtooth, wavy, or random finger-shaped splicing paths. Specifically, the splicing path uses a sinusoidal wave modulated boundary, and its wave function is defined as... .in, The coordinates of the current scan path point. The center coordinates of the logical boundary between the left and right forming regions are used to splice the amplitude. Set to 0.3mm-0.8mm, cycle Set to 1.0mm-2.0mm, and interlayer phase A random offset is introduced. When the vector scan reaches this boundary, the system extends the overlap to both sides at the breakpoint. (0.05mm-0.1mm), and in conjunction with the light-off delay and light-on delay commands, the melting channels on the left and right sides form a micro-interlocking structure.

[0049] This splicing path creates an interlocking pattern between the molten metal on both sides, avoiding stress concentration at straight seams and ensuring that the mechanical strength (tensile strength, yield strength) of the printed part at the splicing location is consistent with the solid part. Furthermore, the system supports checkerboard or strip scanning strategies and automatically adjusts the priority of scan lines based on the airflow direction (previously set X / Y directions), ensuring that the smoke generated by laser scanning is always discharged along the airflow direction and does not contaminate the laser window in unscanned areas.

[0050] Example 7: In SLM printing, toner supply is crucial. The system's control of the toner cylinder shaft goes beyond simple upward toner feeding; it includes intelligent toner level monitoring. The system memory records the initial loading height, cross-sectional area, and bulk density of the metal powder in the toner cylinder. As the number of printed layers increases, the toner cylinder shaft rises continuously. Based on the current stroke parameters of the toner cylinder shaft and a preset minimum toner level threshold (which typically corresponds to the amount of toner required to ensure complete placement of the last few layers), the system calculates and updates the upper limit alarm position in real time.

[0051] Before each toner supply action, the system compares the current position with the alarm position. When the feedback position of the toner cylinder shaft reaches or exceeds the upper limit alarm position, the system immediately triggers a toner shortage warning. At this time, the system suspends the current printing job and controls the three-color alarm light or sends a remote notification to the operator. The operator can replenish toner without stopping the machine (if the equipment supports online toner refilling) or while the machine is paused, and then resume printing, thus avoiding dry printing due to toner shortage. In addition, to ensure smooth movement and prevent powder from splashing or unevenly compacting due to vibration, the system supports fine configuration of the movement type of all motor shafts (including the doctor blade, forming cylinder, and toner cylinder). Configuration options include horizontal speed change mode (for the doctor blade) and vertical lifting mode (for the cylinder). The system uses an S-shaped speed curve algorithm at its core, allowing users to set acceleration (acceleration) and deceleration (deceleration) parameters. The S-shaped curve smooths the second derivative of the speed, enabling a smooth transition of the motor during start-up and stop, avoiding the mechanical shock and vibration that may be caused by a trapezoidal speed curve.

[0052] Example 8: Furthermore, given that this system employs a special architecture with four (or more) mirrors arranged longitudinally along the front-to-back direction, the optical path difference at the edge of the field of view changes more drastically compared to the traditional central-radial layout. Therefore, it is necessary to rely on high-precision software algorithms and optical hardware in tandem to minimize the nonlinear distortion and defocusing caused by the physical optical path.

[0053] In optical principles, when a laser beam is refracted by an F-Theta field lens or dynamic focusing lens, the scanning trajectory projected onto a plane is essentially part of a sphere. In large-format printing equipment with vertically arranged lenses, when the galvanometer scans to the far edge of its coverage area, the laser incident angle is extremely large, causing the focal plane to separate from the actual powder bed plane, resulting in severe defocus spots and pincushion geometric distortion. Therefore, the geometric correction module of this system is configured to read and parse a preset high-order correction file (usually a dataset in .cor or xml format). This file not only contains basic X / Y linear scaling coefficients and rotation angle parameters, but more importantly, it contains a nonlinear compensation matrix based on the full-field grid points. During printing, the host computer uses a bilinear interpolation algorithm to calculate the corresponding physical galvanometer deflection voltage compensation value in real time based on the current logical coordinates, actively correcting pincushion or barrel distortion caused by the characteristics of the optical lenses, ensuring that the scanned straight lines remain straight at the micrometer level and that the square shape is accurately formed.

[0054] More importantly, this embodiment introduces Z-axis dynamic focusing compensation technology to address the issues of spot ellipticization and depth-of-focus variation caused by biased printing. The system establishes a three-dimensional spatial model of the distances between the galvanometer center and various points on the forming chamber plane. While the laser beam scans the plane, the control algorithm calculates the change in optical path length corresponding to the current spot position in real time and synchronously drives the dynamic zoom beam expander in the optical components to move at high frequency along the optical axis. This dynamically compensates for focal length deviations caused by changes in the incident angle, forcibly setting the laser focus on a flat powder bed and preventing further spot divergence and a sharp drop in energy density due to defocusing. Through this three-dimensional dynamic correction, even in the outermost regions of the vertically arranged array, the system can maintain high focusing accuracy and suppress the ellipticization trend of the spot as much as possible.

[0055] Furthermore, to ensure seamless splicing of multiple galvanometers within the overlap buffer, the system incorporates an automated splicing calibration process. During equipment commissioning, the system controls two adjacent galvanometer groups to print high-precision crosshair or vernier caliper calibration patterns at specific locations (such as the center line and four corners) within the overlap area. The first galvanometer group prints the horizontal portion of the crosshair, and the second galvanometer group prints the vertical portion. By measuring the overlap error of the crosshair center using a high-resolution machine vision system or a manual microscope, the system automatically reverse-calculates and updates the coordinate translation and rotation parameters in the calibration file.

[0056] Example 9: In industrial production environments, unexpected power outages, voltage fluctuations leading to system restarts, or emergency stops triggered for safety reasons may occur. To address these situations, the module is configured to perform high-frequency breakpoint recording operations during system operation. The system utilizes non-volatile memory (such as NVRAM, ferroelectric memory, or SSD partitions with power-loss protection) to record current critical status information in real time. This information includes, but is not limited to: the current print layer number, the galvanometer scan index pointer within the current layer (precisely indicating which vector line has been scanned), the real-time encoder positions of each axis (scraper, forming cylinder, powder cylinder), and the current process parameter group ID.

[0057] Upon detecting an abnormal power outage (triggered by a UPS signal) or executing an automatic shutdown procedure, the system ensures that the last state data is completely written. After the next power restoration, system restart, and self-test, the software automatically checks for any incomplete breakpoint records. If any exist, the system prompts the user to resume the last print. If the user confirms resumption, the system reads the breakpoint record information. The system controls the first and second scraper assemblies and each cylinder axis to execute a reset and zeroing procedure, but immediately after zeroing, it moves to the safe position recorded before the breakpoint (i.e., the Z-axis height at the moment of power failure). For the galvanometer system, the system loads the scan index at the breakpoint. To ensure fusion quality, the system may automatically backtrack several scan lines for overlapping scans to minimize potential melt pool defects caused by the power outage. Subsequently, the system restores the collaborative control logic and continues executing the remaining printing tasks.

[0058] Example 10: like Figure 2 As shown, this embodiment provides a specific execution flow for the collaborative control method of multi-mirror and dual-scraper partitioned SLM 3D printing based on the above hardware architecture: Step S1: System initialization, dividing the molding platform into independent left and right working areas, and resetting the molding cylinders and scraper assemblies on the left and right sides respectively; Step S2: Read the slice data, plan the scanning path according to the multi-mirror column layout, and apply the spot distortion correction algorithm to generate the corrected scanning command; Step S3: Enter the collaborative work cycle: Status A: Control the multi-mirror laser scanning unit to scan and shape the left working area; at the same time, control the right forming cylinder to descend one layer, and drive the second scraper assembly to complete the powder picking, spreading and dropping actions; Status switching: Monitor the task status on both sides. When the left side scan is completed and the right side powder application is ready, switch to status B. Status B: Control the multi-mirror laser scanning unit to scan and shape the right working area; at the same time, control the left forming cylinder to descend one layer, and drive the first scraper assembly to complete the powder picking, powder spreading and powder falling actions; Step S4: Repeat step S3 until the printing task is completed.

[0059] Specifically, after system initialization and self-test, the control flow first enters the data preprocessing stage. The host computer reads the slice data of the model to be printed and calls the aforementioned dynamic correction module for light spot distortion. For the system's unique multi-galvanometer vertical arrangement architecture, the algorithm no longer simply cuts the large image into regular rectangular blocks, but generates scanning path instructions that have undergone geometric distortion compensation and energy density correction based on the optical field limit and incident angle distribution of the galvanometers. The system calculates the scanning vector sets of the left and right forming areas for each layer, determines the optimal left / right switching node based on the load balancing algorithm, and preloads the processed instruction stream into the lower-level control card.

[0060] Subsequently, the system enters its core asynchronous alternating printing cycle, which can be described as a seamless transition between left scan-right powder laying and right scan-left powder laying. In the first stage, the system controls the multi-mirror laser scanning unit to focus on laser melting of the left forming area. Simultaneously, the system drives the independent hardware of the right forming area to execute the powder laying cycle via asynchronous commands: the right forming cylinder shaft descends by one layer thickness, the second scraper assembly on the right picks up powder from the powder outlet, completes the powder laying of the right area at the set process speed, and returns to the safe waiting position. During this period, the laser remains in a high-frequency emission state, completely unaffected by the mechanical movements on the right.

[0061] Once the system detects that the scanning task in the left forming area is complete, the control logic immediately triggers an interlock status check. At this time, since the powder spreading action in the right area has been completed synchronously during the previous scanning phase and is in a ready state, the system does not need to perform any mechanical waiting. It directly controls the optical path of the galvanometer group to jump to the right forming area and immediately starts laser emission, entering the second phase. In this phase, the laser beam melts the right forming area, while the hardware in the left forming area is simultaneously activated: the left forming cylinder shaft descends, and the first scraper assembly on the left performs powder picking and spreading actions, preparing for the next round of scanning.

[0062] The system repeatedly performs the state switching between the two phases described above. Throughout the printing process, except for a very short galvanometer jump time, the laser remains in a state of effectively processing one side of the area. Only after all slice layers on both sides have been printed will the system stop laser output and reset each motion axis, thus completing the entire efficient collaborative printing task.

[0063] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A collaborative control system for SLM 3D printing with multiple galvanometers and dual scrapers, the system comprising an upper computer interactive control unit, a lower computer real-time motion control unit, a multiple galvanometer laser scanning unit, and a forming chamber actuator; The molding chamber actuator is physically divided into a left molding area and a right molding area. The left molding area is equipped with an independently driven first molding cylinder and a first scraper assembly, and the right molding area is equipped with an independently driven second molding cylinder and a second scraper assembly. The multi-mirror laser scanning unit includes at least one set of galvanometers arranged longitudinally or in a matrix, and its scanning range covers the left forming area and the right forming area; The host computer interactive control unit is equipped with a partitioned timing collaborative scheduling module, which is configured to execute the following collaborative control logic: Establish a timing overlap mechanism: decompose the printing process into a laser scanning cycle and a toner application and dispensing cycle, and establish asynchronous job queues for the left and right sides. Asynchronous alternating control is performed: when the multi-mirror laser scanning unit performs laser scanning processing on the left forming area, the system synchronously drives the second scraper assembly to perform powder spreading and powder dropping actions in the right forming area, and controls the second forming cylinder to complete the layer thickness reduction. When the scanning of the left forming area is completed and the powder is ready in the right forming area, the system controls the multi-mirror laser scanning unit to seamlessly switch to the right forming area for laser scanning processing. At the same time, the system synchronously drives the first scraper assembly to perform powder spreading and powder dropping actions in the left forming area, and controls the first forming cylinder to complete the layer thickness reduction. The system repeats the above alternating process in a loop to minimize the idle time of the laser while waiting for powder to be spread.

2. The multi-mirror and dual-scraper partitioned SLM 3D printing collaborative control system according to claim 1, characterized in that, The multi-mirror laser scanning unit adopts a vertical arrangement. To address the issues of large incident angle and elliptic spot of the laser beam at the edge of the forming surface caused by the vertical arrangement, the system is equipped with a large-format spot distortion dynamic correction module. The correction module is configured to: calculate the incident angle of the laser beam in real time based on the geometric relationship between the center coordinates of the galvanometer and the coordinates of the current scanning point; perform dynamic focusing compensation and spot shape correction on the laser spot through the galvanometer control algorithm according to the incident angle, so that the energy density of the laser beam remains consistent to the greatest extent in the entire forming surface; at the same time, combined with the laser offset algorithm, perform micron-level position compensation on the scanning path to correct the geometric distortion caused by the incident angle.

3. The multi-mirror and dual-scraper partitioned SLM 3D printing collaborative control system according to claim 1, characterized in that, The lower-level real-time motion control unit includes dual independent scraper path planning modules; The first scraper assembly and the second scraper assembly each have independent powder picking position, powder dropping position and waste powder recycling position; during the collaborative control process, the system monitors the position status of the two scrapers in real time, and ensures through logical interlocking that when a single scraper enters its corresponding forming area to perform the powder spreading action, the other side area is in laser scanning or waiting state, and the actions of the two sides do not interfere with each other in physical space.

4. The multi-mirror and dual-scraper partitioned SLM 3D printing collaborative control system according to claim 1, characterized in that, The partitioned time-series collaborative scheduling module also includes dynamic load balancing and pre-waiting logic; If the laser scanning time of one side is less than the powder spreading time of the other side, the system controls the laser scanning unit to enter a microsecond-level standby state after completing the current side scan, until the powder spreading completion signal of the other side is received; If the laser scanning time on one side is longer than the powder spreading time on the other side, the system controls the scraper on the side that has completed powder spreading to stop at the preset safe waiting position. Once the laser scanning switching signal is triggered, the next level of action will be activated immediately.

5. The multi-mirror and dual-scraper partitioned SLM 3D printing collaborative control system according to claim 2, characterized in that, The large-format light spot distortion dynamic correction module also includes laser energy-velocity dynamic coupling compensation logic. To address the optical path difference variation caused by the longitudinal arrangement, the system establishes an optical path-energy attenuation model. During the scanning process, the output power of the laser or the galvanometer rotation speed is dynamically adjusted based on the real-time optical path length and the spot deformation rate to ensure the consistency of the metallurgical properties of the formed parts in different regions.

6. The multi-mirror and dual-scraper partitioned SLM 3D printing collaborative control system according to claim 1, characterized in that, Each galvanometer of the multi-mirror laser scanning unit covers a set area in the front-to-back direction and a complete left or right forming area in the left-to-right direction, achieving large-format coverage through the vertical splicing of the multi-mirror units.

7. The multi-mirror and dual-scraper partitioned SLM 3D printing collaborative control system according to claim 1, characterized in that, The lower-level real-time motion control unit is also configured to control the molding cylinder shaft and the powder cylinder shaft; For the powder cylinder shaft, the system calculates the upper limit alarm position in real time based on the stroke parameters and the preset minimum powder quantity threshold; when the feedback position of the powder cylinder shaft reaches the upper limit alarm position, a powder shortage warning is triggered; the system supports configuring acceleration and deceleration parameters of S-shaped speed curves for the motor shaft to smooth the mechanical vibration when the shaft starts and stops.

8. The multi-mirror and dual-scraper partitioned SLM 3D printing collaborative control system according to claim 1, characterized in that, The multi-mirror laser scanning unit is equipped with a mirror geometry correction module; The galvanometer geometry correction module is used to read a preset galvanometer correction file, which includes X-axis scaling factor, Y-axis scaling factor and coordinate rotation angle parameters; the system performs real-time coordinate transformation and pincushion distortion compensation on the scanning command of the galvanometer group according to the parameters.

9. The multi-mirror and dual-scraper partitioned SLM 3D printing collaborative control system according to claim 1, characterized in that, The system also includes a power-off resume and status recovery module; The module is configured to record the current print layer number, galvanometer scan index pointer, and position status of each axis to a non-volatile memory in real time during system operation. When an abnormal power outage or automatic shutdown procedure is detected, the system reads the breakpoint record information upon the next startup, controls each moving component to reset to a safe position, and restores the collaborative control logic.

10. A method for coordinated control of SLM 3D printing based on the system of any one of claims 1 to 9, characterized in that, The method includes the following steps: Step S1: System initialization, dividing the molding platform into independent left and right working areas, and resetting the molding cylinders and scraper assemblies on the left and right sides respectively; Step S2: Read the slice data, plan the scanning path according to the multi-mirror column layout, and apply the spot distortion correction algorithm to generate the corrected scanning command; Step S3: Enter the collaborative work cycle: Status A: Control the multi-mirror laser scanning unit to scan and shape the left working area; at the same time, control the right forming cylinder to descend one layer, and drive the second scraper assembly to complete the powder picking, spreading and dropping actions; Status switching: Monitor the task status on both sides. When the left side scan is completed and the right side powder application is ready, switch to status B. Status B: Control the multi-mirror laser scanning unit to scan and shape the right working area; at the same time, control the left forming cylinder to descend one layer, and drive the first scraper assembly to complete the powder picking, powder spreading and powder falling actions; Step S4: Repeat step S3 until the printing task is completed.

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