A large-area laser milling composite machining device and method based on visual positioning

Abstract

The application discloses a large-area laser milling composite machining device and method based on visual positioning, and belongs to the machining field.The device comprises a laser unit and a milling unit, the laser unit comprises a laser, an optical path, a camera, a protective cover and a fixing frame, and the milling unit comprises a machine tool spindle and a mechanical platform.The application also provides a laser milling composite machining method based on visual positioning, according to a workpiece installation angle, a machining pattern and a tool path are transformed, a laser machining pattern is divided into sub-patterns, the sub-patterns are machined, a splicing position molten pool feature is extracted, subsequent machining parameters are optimized, a splicing position machining pattern is compensated to reduce a machining molten pool, and milling machining is carried out on a machining surface.The application drives a laser galvanometer by a mechanical platform, cooperates with laser milling machine linkage control, realizes precise large-area pattern laser splicing machining and composite milling machining at the same time, guarantees high-precision coincidence of the laser pattern and the milling path, and guarantees large-area machining quality of the microstructure.

Description

Technical Field

[0001] The present invention relates to the field of laser milling composite processing, and in particular to a large-area laser milling composite processing device and a processing method for visual positioning. Background Art

[0002] In recent years, laser processing and micro-milling have been increasingly used in aerospace, defense, medical biology, and electronic communications. Laser processing, due to its high processing quality, minimal heat-affected zone, and high processing efficiency, is an excellent method for processing microstructures. Similarly, micro-milling, as a form of cold processing, uses minimal cutting parameters under lubricated cutting conditions to effectively avoid changes in the material's physical and chemical properties, allowing the processing of microstructures with minimal impact on the substrate.

[0003] However, when processing microstructures over a large area, multiple processes are often required, which places extremely high demands on their positioning accuracy. The current manual positioning method for processing microstructures is highly random, and it is difficult to place the workpiece directly in the appropriate position when placing it. It cannot meet the position and angle requirements of the workpiece and requires repeated manual adjustments. The positioning accuracy is low and the time consumption is long, which seriously reduces the processing efficiency and processing accuracy. In addition, the processing range of the laser galvanometer is limited (no more than 100mm*100mm), and its large-area processing requires the coordinated movement of the mechanical platform. However, the laser galvanometer and the mechanical platform are currently both independent control systems, and the linkage control of the two cannot be achieved. If manual positioning is used, the processing quality is low and the processing efficiency is poor. At the same time, the splicing patterns before and after laser splicing are affected by multiple factors such as laser switch, galvanometer deflection, and start and stop of the motion platform, which can easily cause the splicing molten pool to be too deep or the laser pattern to be not spliced ​​in place, resulting in poor processing quality at the splicing point, which seriously limits the large-area microstructure laser processing.

[0004] Therefore, visual recognition of the position and angle of microstructure workpieces and the equipment and control of laser galvanometer mechanical platforms are the key to achieving large-scale preparation of microstructures. They can effectively expand the processing area, improve processing accuracy and efficiency, and are of great significance for achieving continuous and precise processing of large-area microstructures. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a large-area laser milling composite processing device and method with visual positioning.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A large-area laser milling composite processing device with visual positioning includes a laser unit and a milling unit. The laser unit includes a laser, an optical path and a camera. The laser generates and emits laser light into the optical path. The optical path changes the laser transmission path and processes the laser light, and finally irradiates it vertically downward to the workpiece surface. The camera observes the position of the laser processing area and extracts the workpiece position information. The milling unit includes a machine tool spindle and a mechanical platform. The mechanical platform can move in the X, Y, and Z axis directions relative to the machine tool spindle. The laser unit is fixed on the machine tool spindle and moves together with the machine tool spindle. The workpiece is placed on the mechanical platform.

[0008] To optimize the above technical solutions, specific measures taken also include:

[0009] The above-mentioned mechanical platform includes a base, a Y-axis drive, a machine tool platform, a heightening platform and an arch frame. The base is placed on the ground, the Y-axis drive is fixed in the center of the base, the machine tool platform is slidingly set on the Y-axis drive, and the Y-axis drive can drive the machine tool platform to move in the Y-axis direction. The heightening platform is fixed on one side of the machine tool platform to adjust the workpiece processing height. The arch frame is fixed in the upper middle part of the base to support the machine tool spindle and the laser unit on it.

[0010] The above-mentioned machine tool spindle includes a tool, a tool holder, a Z-direction drive, a nozzle, a spindle, an X-direction drive and a spindle housing. The tool is clamped in the tool holder, the tool holder is clamped at the bottom of the spindle, the nozzle is fixed on the bottom side of the spindle, the nozzle is used to spray cutting fluid, the spindle is fixed to the X-direction drive through the Z-direction drive, the X-direction drive is fixed to the arch frame, the X-direction drive is used to drive the Z-direction drive to move in the X-axis direction, the Z-direction drive is used to drive the spindle to move in the Z-axis direction, and the spindle housing covers the outside of the spindle to protect the spindle.

[0011] The above-mentioned laser includes a laser generator, a transmission optical fiber and a laser emission head. The laser generator is fixed on the main shaft of the machine tool. The laser generator can emit a laser beam. The transmission optical fiber connects the laser generator and the laser emission head. The transmission optical fiber can transmit the laser beam. The laser emission head is facing the laser light path.

[0012] The above-mentioned optical path includes a first reflector, a galvanometer mirror and a second reflector. The first reflector refracts the laser beam emitted from the laser emission head into the galvanometer mirror, and the second reflector is used to refract the laser beam emitted from the galvanometer mirror onto the workpiece surface.

[0013] The above-mentioned laser unit also includes a protective cover and a fixing frame. The optical path is fixed on the fixing frame, and the fixing frame is fixedly installed on the base. The protective cover is wrapped around the outside of the laser and the optical path to prevent liquid and dust from contacting the laser and the optical path. The camera is a high-magnification coaxial CCD. The camera is fixed on the camera fixing frame, and the camera fixing frame is fixed on the second fixing frame.

[0014] The protective cover is provided with a ring light and infrared glass. The ring light is used to illuminate the laser processing area and provide a clear field of view for the camera.

[0015] A large-area laser milling composite processing device with visual positioning also includes a control unit, which includes a laser control unit, a machine tool control unit and a computer. The laser control unit is used to control the operation of the laser, optical path and camera, and the machine tool control unit is used to control the movement and milling of the milling unit. The laser control unit and the machine tool control unit are both connected to the computer, and the computer is used to receive information from the laser control unit and the machine tool control unit and send instructions to the laser control unit and the machine tool control unit.

[0016] A large-area laser milling composite processing method with visual positioning, using the large-area laser milling composite processing device mentioned above, specifically includes the following steps:

[0017] Step 1: Fix the workpiece on the mechanical platform and draw the laser processing graphics and milling processing path on the computer;

[0018] Step 2: Drive the mechanical platform and the machine tool spindle to move the corner of the workpiece into the range of the camera lens;

[0019] Step 3: The camera identifies the vertex and two sides of the workpiece corner within the lens range, obtains the X, Y difference between the camera center coordinates and the workpiece corner vertex position coordinates in the current field of view, reads the current coordinates of the machine tool based on the fixed X, Y position relationship between the machine tool spindle center and the camera center, converts the workpiece vertex coordinates in the field of view into the workpiece vertex coordinates in the absolute coordinate system of the machine tool using the two X, Y relative relationships, and establishes the workpiece coordinate system in the machine tool with the workpiece corner vertex as the origin;

[0020] Step 4: Based on the identified workpiece installation angle, the computer automatically transforms the drawn laser processing graphics and milling tool path, and rotates the laser processing graphics and milling tool path by the identified angle according to the installation direction to form the transformed laser processing graphics and tool path;

[0021] Step 5: The computer divides the transformed laser processing pattern into a grid according to the set size, obtaining several rows and columns of sub-patterns, and generates the corresponding machine tool movement path based on the segmentation size and the workpiece coordinate system position;

[0022] Step 6: The laser unit first moves to the top of the first segmented sub-area. The camera retains the unprocessed surface topography image of this area. At this time, the laser processable area has completely covered this sub-area, and the laser processing of the graphics in this sub-area is carried out.

[0023] After the sub-region is processed, the camera identifies the processed surface morphology of the sub-region, compares it with the unprocessed surface morphology image, identifies the actual processed pattern, and extracts the processed pattern at the edge segmentation of the sub-region;

[0024] Step 7: The laser unit moves to the next sub-area for processing, identifies the images before and after processing, and extracts the actual processing graphics after processing of both sub-areas;

[0025] Step 8: Compare the appearance of the front and rear sub-areas at the segmentation point to determine the overall pattern deviation of the actual laser processing, and generate a processing compensation parameter m for the galvanometer processing height and galvanometer sub-area positioning. When processing the next sub-area, automatically adjust the machine tool and galvanometer movement parameters according to the compensation parameter m and process;

[0026] At the same time, the size of the laser processing molten pool at the joint of the two sub-areas is judged, and a compensation parameter n is generated to compensate for the line length at the edge connection of each sub-area, reducing the impact of the laser processing molten pool overlap on the processing quality of the joint. When processing the next sub-area, the processing parameters are automatically adjusted according to the compensation parameter n and processing is carried out;

[0027] Step 9: Repeat steps 7 and 8, continuously identifying and compensating the processed graphics until all segmented areas are processed, completing the splicing processing of large-area graphics that exceed the processing range of a single laser galvanometer;

[0028] Step 10: The computer sends the tool path with the changed angle to the machine tool control system, and further performs milling on the surface of the workpiece after laser processing to achieve high-precision matching between the laser processing pattern and the milling processing path.

[0029] In step eight, the appearance of the front sub-region and the rear sub-region is compared to determine the deviation of the overall pattern of the actual laser processing. The specific method for generating the processing compensation parameter m for the galvanometer processing height and the positioning of the galvanometer sub-region is as follows:

[0030] Compare the front and back sub-area images to obtain the actual processing graphics, dynamically identify the line width of the actual processing graphics, generate the processing graphics center line, and use this line width to determine the edge endpoint position of the center line at the splicing point;

[0031] According to the theoretical processing graph, the theoretical processing starting endpoints of the rear sub-region after the melt pool compensation calculation at the endpoint of the front sub-region dividing line are set as the a sequence a1, a2, a3..., and the starting endpoints after the actual melt pool compensation are marked as the b sequence b1, b2, b3...;

[0032] First, the Y-direction error of the galvanometer sub-region positioning is compensated. By comparing the theoretical processing pattern with the endpoints of the b-sequence, the actual segmentation edge of this sub-region is located. The Y-direction deviation of the segmentation edge midpoints of the previous and next sub-regions is compared. The Y-axis positioning of the galvanometer in the sub-region is compensated, and a sub-region compensation model after the galvanometer positioning Y-direction compensation is generated. The compensated b-sequence is recorded as the b' sequence.

[0033] Secondly, the rotation error of the galvanometer sub-area positioning is compensated. The angle error between the b' sequence dividing line and the a sequence dividing line is identified by the difference in the X-direction coordinates of the corresponding endpoints of the a and b' sequences. The error identified by the segmentation edge line is converted to the rotation angle compensation of the sub-area galvanometer positioning center. The corresponding Y-axis compensation caused by the angle compensation is generated by multiplying the sine value of the identified rotation angle by half of the length of the segmented area. The Y-axis compensation is also added to the Y-axis compensation of the galvanometer positioning.

[0034] Finally, compensate for the galvanometer processing height error by using the Y-direction coordinate difference of the corresponding endpoints of the a and b' sequences. If the value is smallest near the center of the dividing line and the value on both sides of the dividing line increases continuously, it means that there is a deviation in the galvanometer processing height. If the Y difference of the first pair of endpoints is greater than zero and the Y difference of the last pair of endpoints is less than zero, then the compensation is to reduce the galvanometer processing height. If the Y difference of the first pair of endpoints is less than zero and the Y difference of the last pair of endpoints is greater than zero, then the compensation is to increase the galvanometer processing height.

[0035] Multiple processing and multiple compensations are performed, and the compensation parameter m is continuously iterated to make the endpoints of most laser processing trajectories connected;

[0036] In step eight, the size of the laser processing molten pool at the junction of the two sub-areas is determined, and the specific method for generating the compensation parameter n is as follows:

[0037] Compare the front and back sub-area images to obtain the actual processing graphics, dynamically identify the line width of the actual processing graphics, generate the processing graphics center line, and use this line width to determine the edge endpoint position of the center line splicing;

[0038] Assume that the average line width of the actual processing is 2r, the bending angle of the line segment to be connected on both sides of the dividing line is α, the remaining unprocessed area when the rear line segment is normally compensated is φ1, and the remaining unprocessed area when the line segment is tangent to the front line segment is φ2. According to the recognized connection angle, the inward compensation distance of the line segment is different.

[0039] When α≥90°, keep processing the line segments of the old sub-region to the endpoint of the dividing line, and shorten the line segments of the new sub-region to the inner region by a distance n1=r~2r, so that the connection is overlapped slightly without expanding the molten pool, and reduce the unprocessed area between the two line segment endpoints and the molten pool, so that φ1≤75%φ2, and obtain the most continuous connection edge possible;

[0040] When α<90°, keep processing the line segments of the old sub-region to the end point of the dividing line, and shorten the line segments of the new sub-region inward by a distance n2, 5r>n2>2r, φ1≤75%φ2;

[0041] When the front and rear sub-areas are spliced ​​together, multiple line segments are spliced ​​together. For multiple groups of line segments with α≥90°, n1 is used to compensate, and for multiple groups of line segments with α<90°, n2 is used to compensate.

[0042] The beneficial effects of the present invention are as follows: the present invention effectively expands the laser processing area and reduces the workpiece repositioning error by combining the laser unit and the milling unit using a motion platform; visual recognition is adapted to the laser processing of a variety of different materials; continuous proofreading and multiple compensations improve the overall accuracy of the splicing processing sub-patterns and large-area patterns, while reducing the size of the molten pool at the connection and improving the quality of the splicing edge lines; and improving the processing accuracy and efficiency of continuous and precise processing of large-area microstructures. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the overall structure of the large-area laser milling composite processing device with visual positioning of the present invention.

[0044] Figure 2 This is a schematic diagram of the laser unit structure of the large-area laser milling composite processing device with visual positioning of the present invention.

[0045] Figure 3 This is a schematic diagram of a control unit of the large-area laser milling composite processing device with visual positioning according to the present invention.

[0046] Figure 4 This is a schematic diagram of the transmission optical fiber channel of the large-area laser milling composite processing device with visual positioning of the present invention.

[0047] Figure 5 This is a flow chart of the large-area laser milling composite processing method with visual positioning of the present invention.

[0048] Figure 6 This is a processing and machining diagram of the large-area laser milling composite machining method with visual positioning of the present invention.

[0049] Figure 7 This is a flow chart of the compensation method for the large-area laser milling composite processing method with visual positioning of the present invention.

[0050] Figure 8 This is a schematic diagram of the molten pool compensation method of the large-area laser milling composite processing method with visual positioning of the present invention.

[0051] Explanation of reference numerals: 1. Laser unit; 2. Milling unit; 3. Control unit; 11. Mechanical platform; 12. Machine spindle; 111. Base; 112. Y-axis drive; 113. Machine platform; 114. Heightening platform; 115. Arch; 121. Tool; 122. Tool holder; 123. Z-axis drive; 124. Nozzle; 125. Spindle; 126. X-axis drive; 127. Spindle housing; 21. Laser; 22. Optical path; 23. Camera; 2 4. Protective cover; 25. Fixing frame; 211. Laser generator; 212. Transmission optical fiber; 213. Laser emission head; 221. First reflector; 222. Galvanometer; 223. Second reflector; 231. Camera fixing frame; 232. High-magnification coaxial CCD; 241. Transmitter head cover; 242. Transparent film; 243. Acrylic shell; 244. Ring light; 245. Infrared glass; 31. Laser control unit; 32. Machine tool control unit; 33. Computer. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts are within the scope of protection of this application.

[0053] Obviously, the drawings described below are merely examples or embodiments of the present application. Those skilled in the art can, without inventive effort, apply the present application to other similar scenarios based on these drawings. Furthermore, it is also understood that, although the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, changes in design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as an insufficiency of the content disclosed in this application.

[0054] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments unless there is a conflict.

[0055] Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person of ordinary skill in the technical field to which this application belongs. The words "a", "an", "a", "the" and the like used in this application do not indicate a limit on quantity and may indicate the singular or plural. The terms "include", "comprise", "have" and any variations thereof used in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or units (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units that are inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The words "multiple" / "several" used in this application refer to two or more. "And / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, or B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific order for the objects.

[0056] like Figure 1-4 As shown, the present invention provides a large-area laser milling composite processing device with visual positioning, comprising:

[0057] Laser unit 2 and milling unit 1.

[0058] The laser unit 2 includes a laser 21, an optical path 22, a camera 23, a protective cover 24 and a fixing frame 25. The laser 21 generates and emits laser light into the optical path 22. The optical path 22 changes the laser transmission path and processes the laser light, and finally irradiates it vertically downward to the surface to be processed. The optical path 22 is fixed in the fixing frame 25. The camera 23 observes the position of the laser processing area and extracts the workpiece position information. The protective cover 24 provides light and wraps the exposed part of the laser unit to prevent liquid and dust from damaging the laser unit 2.

[0059] The milling unit 1 includes a machine tool spindle 12 and a mechanical platform 11. The machine tool spindle 12 can move in the X-axis and Z-axis directions, and the mechanical platform 11 can move in the Y-axis direction. The laser unit 2 is fixed on the machine tool spindle 12 and moves together with the machine tool spindle 12.

[0060] The mechanical platform 11 comprises a base 111, a Y-axis drive 112, a machine platform 113, a raised platform 114, and an arch 115. The base 111 is placed on the ground, the Y-axis drive 112 is fixed in the center of the base 111, the machine platform 113 is the target platform for the Y-axis drive 112 to move and control, the raised platform 114 is fixed to one side of the machine platform 113 and is used to adjust the workpiece processing height. The arch 115 is fixed to the upper center of the base 111 and supports the machine spindle 12 and the laser unit 2 thereon, and provides space for the machine spindle 12 to move in the X direction. When the Y-axis drive 112 moves, the machine platform 113 and the raised platform 114 move in the Y direction to the set position according to the travel distance.

[0061] The machine tool spindle 12 includes a tool 121, a tool holder 122, a Z-direction drive 123, a nozzle 124, a spindle 125, an X-direction drive 126 and a spindle housing 127. The tool 121 is clamped in the tool holder 122, the tool holder 122 is clamped at the bottom of the spindle 125, and the lower left side of the spindle 125 is close to the fixed nozzle 124 for spraying cutting fluid. The spindle 125 is fixed to the X-direction drive 126 through the Z-direction drive 123, and the X-axis is fixed to the arch frame 115. The spindle housing 127 is fixed to the X-direction drive 126 and moves with the spindle 125 in the X direction. When the spindle 125 is raised or lowered, the spindle housing 127 does not move up and down with the spindle 125, but only serves to shield the upper part.

[0062] The laser 21 includes a laser generator 211, a transmission optical fiber 212, and a laser emission head 213. The laser generator 211 is fixed to the fixed part on the top rear side of the machine tool spindle 12. The laser generator 211 can emit a laser beam. The transmission optical fiber 212 connects the laser generator 211 and the laser emission head 213. The transmission optical fiber 212 can transmit the laser beam. The laser emission head 213 is fixed in front of the machine tool spindle 12, facing the laser optical path 22.

[0063] The optical path 22 includes a first reflector 221, a galvanometer mirror 222, and a second reflector 223. The first reflector 221 is fixed to the right side of the laser emission head 213. The optical path is rotated downward 90° so that the optical path is vertically downwardly transmitted into the galvanometer mirror 222. The galvanometer mirror 222 is fixed to the outside of the second fixed frame 25 and the light outlet is facing the positive direction of the Y axis. The optical path is rotated inward 90°. The second reflector 223 is fixed to the inside of the second fixed frame 25 and aligned with the light outlet of the galvanometer mirror 222. The optical path is rotated downward 90° and irradiated to the surface to be processed.

[0064] The camera 23 is a high-magnification coaxial CCD 232 , which is fixed to a camera fixing frame 231 with bolts. The camera fixing frame 231 is fixed to the rear side of the second fixing frame 25 .

[0065] The protective cover 24 includes a transmitter cover 241, a transparent film 242, an acrylic shell 243, a ring light 244, and an infrared glass 245. The transmitter cover 241 is a thin-walled aluminum alloy shell, the transparent film 242 is an oil-proof and water-proof PET film, and the infrared glass 245 is JGS3 infrared quartz glass. The transmitter cover 241 wraps the laser transmitter head 213 of the laser unit 2, the acrylic shell 243 wraps most of the regular-shaped parts of the laser unit 2, and the transparent film 242 wraps the remaining irregular parts of the laser unit 2. The laser processing area is illuminated by a ring light 244 fixed on the infrared glass 245 to provide a clear field of view for the high-magnification coaxial CCD 232. The infrared glass 245 is fixed in the center of the bottom opening of the acrylic shell 243. The centers of the high-magnification coaxial CCD 232, the second reflector 223, the ring light 244 and the infrared glass 245 are coaxial.

[0066] In addition, a channel for the transmission optical fiber 212 is provided inside the machine tool spindle 12 to prevent the transmission optical fiber 212 from rubbing against the spindle housing 127 and being damaged when the machine tool spindle 12 moves on the Z-axis driver 123 .

[0067] The large-area laser milling composite processing device also includes a control unit 3, wherein the machine tool control unit 32 is fixed on the right side of the base 111 to control the movement of the machine tool, and the laser control unit 31 is fixed on the upper part of the arch frame 115 to control the laser processing. The computer 33 is placed next to the base, and the machine tool control unit 32 is connected to the laser control unit 31 and the computer 33.

[0068] The present invention also provides a large area laser milling composite processing method with visual positioning, such as Figure 5 As shown, the following steps are included:

[0069] Fix the workpiece on the mechanical platform 11 and draw the laser processing graphics and milling processing path on the computer;

[0070] Drive the mechanical platform 11 and the machine tool spindle 12 to move the corner of the workpiece into the range of the high-magnification coaxial CCD232 lens;

[0071] The high-magnification coaxial CCD232 identifies the vertex and two sides of the workpiece corner within the lens range, obtains the X, Y difference between the center coordinates of the high-magnification coaxial CCD232 and the position coordinates of the workpiece corner vertex in the current field of view, reads the current coordinates of the machine tool based on the fixed X, Y position relationship between the machine tool spindle center and the high-magnification coaxial CCD232 center, converts the workpiece vertex coordinates in the field of view by the two X, Y relative relationships to obtain the workpiece vertex coordinates in the absolute coordinate system of the machine tool, and establishes the workpiece coordinate system in the machine tool with the workpiece corner vertex as the origin;

[0072] By the recognized workpiece installation angle, the computer automatically transforms the drawn laser processing pattern and the milling processing tool path, rotates the laser processing pattern and the milling processing tool path according to the recognized angle in the installation direction, and forms the transformed laser processing pattern and the tool path;

[0073] The computer divides the transformed laser processing pattern in a grid form according to the set size, obtains a plurality of rows and columns of small-size sub-patterns, and generates corresponding machine tool movement paths according to the division size and the workpiece coordinate system position;

[0074] For example, Figure 6 The laser processing pattern and the milling path processing and processing method is as follows: draw the original laser pattern and the milling path, rotate the laser pattern and the milling path by a certain angle θ, and expand the edges of the original pattern and the path to new edges, divide the transformed pattern according to the set division size, and finally laser process the divided pattern according to a specific order.

[0075] The laser unit 2 first moves to the top of the first divided sub-region, and the high-magnification coaxial CCD 232 retains the unprocessed surface topography image of this region. At this time, the laser processable region has completely covered this small square sub-region, and the laser processing of the sub-region pattern is carried out;

[0076] After the processing of this sub-region is completed, the high-magnification coaxial CCD 232 identifies the surface topography after processing of this sub-region, compares it with the unprocessed surface topography image, identifies the actual processing pattern, and extracts the processing pattern at the edge division of the sub-region;

[0077] The laser unit 2 moves to the next small square sub-region for processing again, identifies the images before and after processing, and extracts the actual processing pattern after the processing of both sub-regions is completed;

[0078] By comparing the appearances at the division of the previous sub-region and the subsequent sub-region, the deviation of the actual laser processing overall pattern is judged, and the processing compensation parameters m for the processing height of the galvanometer and the positioning of the sub-region of the galvanometer are generated. In the processing of the next sub-region, the machine tool and the galvanometer movement parameters are automatically adjusted according to the compensation parameters m and processed;

[0079] At the same time, the size of the laser processing molten pool at the splicing position of the two sub-regions is judged, the compensation parameters n are generated, the line length at the edge connection of each sub-region is compensated, and the influence of the overlapping of the laser processing molten pool on the processing quality at the splicing position is reduced. In the processing of the next sub-region, the processing parameters are automatically adjusted according to the compensation parameters n and processed;

[0080] In this way, Figure 7 The processing pattern is continuously recognized and compensated until all the divided regions are processed, and the splicing processing of the large-area pattern exceeding the single laser galvanometer processing range is completed.

[0081] The computer sends the tool path with changed angles to the machine tool control system, and further performs milling on the surface of the workpiece after laser processing, achieving high-precision matching between the laser processing graphics and the milling processing path.

[0082] Among them, the overall compensation method for extracting the cutting line segments and sub-region patterns is:

[0083] Compare the front and back sub-area images to obtain the actual processing graphics, dynamically identify the line width of the actual processing graphics, generate the processing graphics center line, and use this line width to determine the edge endpoint position of the center line at the splicing point;

[0084] The theoretical optimal overlap of two stitching lines should be almost endpoint overlap. Depending on the connection angle, there may be a small amount of edge overlap near the endpoints. Therefore, when the length of the splicing is not compensated, the actual processing image should only have the minimum melt pool expansion at the coincident endpoints, while the rest of the area should only be a single processing melt pool.

[0085] In actual processing, there may be overlapping or non-overlapping patterns at the edge of the graphics. By comparing the images before and after processing, the splicing endpoints of two or more lines at the edge can be identified.

[0086] According to the theoretical processing graph, the theoretical processing starting endpoints of the rear sub-region after the calculation of the molten pool compensation at the endpoint of the front sub-region dividing line are set as the a sequence (a1, a2, a3...), and the starting endpoints after the actual molten pool compensation are marked as the b sequence (b1, b2, b3...);

[0087] First, compensate for the Y-direction error in the galvanometer mirror positioning of the sub-region. By comparing the endpoints of the b-sequence with the theoretical processing pattern, locate the actual segmentation edge of this sub-region. Compare the Y-direction deviation of the segmentation edge midpoints of the front and rear sub-regions. Compensate the Y-axis positioning of the galvanometer mirror within the sub-region so that the Y-axis coordinate deviation of the midpoint of the segmentation edge line of the front and rear sub-regions is less than 20μm. Then generate a sub-region compensation model after the galvanometer mirror positioning is compensated in the Y direction. The compensated b-sequence is recorded as the b' sequence.

[0088] Secondly, the rotation error of the galvanometer mirror area positioning is compensated. The angular error between the b' sequence dividing line and the a sequence dividing line is identified by the X-direction coordinate difference of the corresponding endpoints of the a and b' sequences. The error identified by the segmentation edge line is converted to the rotation angle compensation of the sub-region galvanometer positioning center. The corresponding Y-axis compensation caused by the angle compensation is generated by multiplying half of the segmentation area length by the sine value of the identified rotation angle. The Y-axis compensation is also added to the Y-axis compensation of the galvanometer positioning. After multiple compensations, the X-direction deviation of the a and b sequences is less than 20μm.

[0089] Finally, the height error of the galvanometer is compensated by the Y coordinate difference of the corresponding end points of a and b' sequences. If the Y coordinate difference of the first pair of end points is greater than zero and the Y coordinate difference of the last pair of end points is less than zero, the height of the galvanometer is lowered. If the Y coordinate difference of the first pair of end points is less than zero and the Y coordinate difference of the last pair of end points is greater than zero, the height of the galvanometer is raised. After multiple compensations, the Y direction deviation of a and b sequences is less than 20 μm.

[0090] After multiple processing and multiple compensation, the compensation parameter m is iterated to make most of the end points of the laser processing trajectories connected, to minimize the overall deviation between the laser processing sub-patterns, and to improve the laser splicing processing precision.

[0091] Meanwhile, the molten pool connection compensation method for the edge line segments of each sub-pattern is as follows:

[0092] The front and rear sub-area images are compared to obtain the actual processing pattern, the line width of the actual processing pattern is dynamically identified, the center line of the processing pattern is generated, and the edge end point position of the center line splicing place is determined according to the line width.

[0093] The theoretical optimal overlap mode of the two splicing lines should only be end point overlap, but at this time, a larger molten pool defect will appear at the connection place of the two line segments, and the length of the line segment at the connection place of each sub-pattern needs to be compensated to reduce the molten pool expansion area.

[0094] Suppose the average line width of the actual processing is 2r, the bending angle of the line segment on both sides of the division line is α, the remaining unprocessed area of the line segment after normal compensation of the rear line segment is φ1, and the remaining unprocessed area of the line segment after tangential compensation of the front line segment is φ2. According to the identified connection angle, the line segment is compensated inwardly by different distances, such as Figure 8 ;

[0095] When α≥90°, the processed part of the line segment of the old sub-area is processed to the end point of the division line, the line segment of the new sub-area is shortened inwardly by a distance n1=r~2r, so that the connection place has a small overlap under the condition of no expansion of the molten pool, the unprocessed area between the end point circles of the two line segments is reduced, φ1≤75%φ2, and a continuous connection edge is obtained.

[0096] When α<90°, the processed part of the line segment of the old sub-area is processed to the end point of the division line, and the line segment of the new sub-area is shortened inwardly by a distance n2, n2>2r, so as to reduce the unprocessed area between the end point circles of the two line segments as much as possible, φ1≤75%φ2, and a continuous connection edge is obtained. However, in order to prevent excessive compensation, n2<5r is limited.

[0097] When splicing the front and rear sub-areas, multiple line segments are spliced. According to the actual processing material conditions, for multiple groups of line segments with α≥90°, n1 can be used for compensation. For multiple groups of line segments with α<90°, n2 with a suitable angle should be used at each connection point.

[0098] In the overall area compensation method, the positioning weight for α≥90° is set to 0.8, and the positioning weight for α<90° is set to 0.2. The lines with the smallest theoretical curvature are mainly used to locate the pattern and judge the angle, in order to reduce the error caused by the increase in the angle in the judgment of the overall compensation parameter m of the sub-area.

[0099] After multiple processing and multiple compensations, the expansion of the molten pool caused by repeated single-point processing should be reduced, and the line segment connection at the cutting point should be made as smooth as possible to improve the accuracy of laser splicing processing.

[0100] In addition, the size of the automatically segmented small square area of ​​the graphics in this embodiment is 80 mm×80 mm.

[0101] It is understandable that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solution described in the implementation of the calculation method of the present invention. Ordinary technicians in this field should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the requirements of the calculation method are met, they are within the scope of protection of the present invention.

Claims

1. A large-area laser milling composite processing method with visual positioning, characterized in that: A large-area laser milling composite processing device using visual positioning is provided. The large-area laser milling composite processing device using visual positioning comprises a laser unit (2) and a milling unit (1). The laser unit (2) comprises a laser (21), an optical path (22) and a camera (23). The laser (21) generates and emits laser light into the optical path (22). The optical path (22) changes the laser transmission path and processes the laser light, and finally irradiates the workpiece surface vertically downward. The camera (23) observes the position of the laser processing area and extracts the workpiece position information. The milling unit (1) comprises a machine tool spindle (12) and a mechanical platform (11). The mechanical platform (11) can move in the X, Y and Z axis directions relative to the machine tool spindle (12). The laser unit (2) is fixed on the machine tool spindle (12) and moves together with the machine tool spindle (12). The workpiece is placed on the mechanical platform (11). The processing method specifically comprises the following steps: Step 1: Fix the workpiece on the mechanical platform (11) and draw the laser processing graphics and milling processing path on the computer; Step 2: driving the mechanical platform (11) and the machine tool spindle (12) to move the corner of the workpiece to within the range of the camera (23); Step 3, the camera (23) identifies the vertex and two sides of the workpiece corner within the lens range, obtains the X, Y difference between the center coordinates of the camera (23) and the position coordinates of the workpiece corner vertex in the current field of view, reads the current coordinates of the machine tool based on the X, Y position relationship fixed between the machine tool spindle center and the camera (23) center, converts the workpiece vertex coordinates in the field of view by two X, Y relative relationships to obtain the workpiece vertex coordinates in the absolute coordinate system of the machine tool, and establishes the workpiece coordinate system in the machine tool with the workpiece corner vertex as the origin; Step 4: Based on the identified workpiece installation angle, the computer automatically transforms the drawn laser processing graphics and milling tool path, and rotates the laser processing graphics and milling tool path by the identified angle according to the installation direction to form the transformed laser processing graphics and tool path; Step 5: The computer divides the transformed laser processing pattern into a grid according to the set size, obtaining several rows and columns of sub-patterns, and generates the corresponding machine tool movement path based on the segmentation size and the workpiece coordinate system position; Step 6: The laser unit (2) first moves to the top of the first segmented sub-region, and the camera (23) retains the unprocessed surface topography image of this region. At this time, the laser processable area has completely covered this sub-region, and the laser processing of the sub-region pattern is carried out; After the sub-region is processed, the camera (23) identifies the surface morphology of the processed sub-region, compares it with the unprocessed surface morphology image, identifies the actual processed pattern, and extracts the processed pattern at the edge segmentation of the sub-region; Step 7: The laser unit (2) moves to the next sub-area for processing, identifies the images before and after processing, and extracts the actual processing graphics after the two sub-areas have been processed; Step 8: Compare the appearance of the front and rear sub-areas at the segmentation point to determine the overall pattern deviation of the actual laser processing, and generate a processing compensation parameter m for the galvanometer processing height and galvanometer sub-area positioning. When processing the next sub-area, automatically adjust the machine tool and galvanometer movement parameters according to the compensation parameter m and process; At the same time, the size of the laser processing molten pool at the joint of the two sub-areas is judged, and a compensation parameter n is generated to compensate for the line length at the edge connection of each sub-area, reducing the impact of the laser processing molten pool overlap on the processing quality of the joint. When processing the next sub-area, the processing parameters are automatically adjusted according to the compensation parameter n and processing is carried out; Step 9: Repeat steps 7 and 8, continuously identifying and compensating the processed graphics until all segmented areas are processed, completing the splicing processing of large-area graphics that exceed the processing range of a single laser galvanometer; Step 10: The computer sends the tool path with the changed angle to the machine tool control system, and further performs milling on the surface of the workpiece after laser processing to achieve high-precision matching between the laser processing pattern and the milling processing path.

2. The large-area laser milling composite processing method with visual positioning according to claim 1 is characterized by: The mechanical platform (11) includes a base (111), a Y-axis drive (112), a machine tool platform (113), a heightening platform (114) and an arch frame (115). The base (111) is placed on the ground, the Y-axis drive (112) is fixed at the center of the base (111), the machine tool platform (113) is slidably arranged on the Y-axis drive (112), and the Y-axis drive (112) can drive the machine tool platform (113) to move in the Y-axis direction. The heightening platform (114) is fixed on one side of the machine tool platform (113) to adjust the workpiece processing height. The arch frame (115) is fixed at the upper middle part of the base (111) to support the machine tool spindle (12) and the laser unit (2) thereon.

3. The large-area laser milling composite processing method with visual positioning according to claim 2 is characterized by: The machine tool spindle (12) includes a tool (121), a tool handle (122), a Z-direction drive (123), a nozzle (124), a spindle (125), an X-direction drive (126) and a spindle housing (127). The tool (121) is clamped in the tool handle (122), the tool handle (122) is clamped at the lower part of the spindle (125), the nozzle (124) is fixed at the lower side of the spindle (125), and the nozzle (124) is used to spray cutting fluid. The spindle (125) is fixed to the X-direction driver (126) via the Z-direction driver (123), and the X-direction driver (126) is fixed to the arch frame (115). The X-direction driver (126) is used to drive the Z-direction driver (123) to move in the X-axis direction, and the Z-direction driver (123) is used to drive the spindle (125) to move in the Z-axis direction. The spindle housing (127) is covered outside the spindle (125) to protect the spindle (125).

4. The large-area laser milling composite processing method with visual positioning according to claim 3 is characterized by: The laser (21) comprises a laser generator (211), a transmission optical fiber (212) and a laser emission head (213); the laser generator (211) is fixed on the machine tool spindle (12); the laser generator (211) can emit a laser beam; the transmission optical fiber (212) connects the laser generator (211) and the laser emission head (213); the transmission optical fiber (212) can transmit the laser beam; and the laser emission head (213) faces the laser optical path (22).

5. The large-area laser milling composite processing method with visual positioning according to claim 1 is characterized by: The optical path (22) comprises a first reflector (221), a galvanometer mirror (222) and a second reflector (223); the first reflector (221) refracts the laser beam emitted from the laser emission head (213) into the galvanometer mirror (222); and the second reflector (223) refracts the laser beam emitted from the galvanometer mirror (222) onto the surface of a workpiece.

6. The large-area laser milling composite processing method with visual positioning according to claim 1 is characterized by: The laser unit (2) further comprises a protective cover (24) and a fixing frame (25), wherein the optical path (22) is fixed on the fixing frame (25), and the fixing frame (25) is fixedly mounted on the machine tool spindle (12), and the protective cover (24) is wrapped around the outside of the laser (21) and the optical path (22) to prevent liquid and dust from contacting the laser (21) and the optical path (22), and the camera (23) is a high-magnification coaxial CCD (232), and the camera (23) is fixed on the camera fixing frame (231), and the camera fixing frame (231) is fixed on the fixing frame (25), and the protective cover (24) is provided with a ring light (244) and an infrared glass (245), and the ring light (244) is used to illuminate the laser processing area and provide a clear field of view for the camera (23).

7. The large-area laser milling composite processing method with visual positioning according to claim 1 is characterized by: The invention also includes a control unit (3), which includes a laser control unit (31), a machine tool control unit (32) and a computer (33). The laser control unit (31) is used to control the operation of the laser (21), the optical path (22) and the camera (23). The machine tool control unit (32) is used to control the movement and milling of the milling unit (1). The laser control unit (31) and the machine tool control unit (32) are both connected to the computer (33). The computer (33) is used to receive information from the laser control unit (31) and the machine tool control unit (32) and send instructions to the laser control unit (31) and the machine tool control unit (32).

8. The large-area laser milling composite processing method with visual positioning according to claim 1 is characterized in that: In step eight, the appearance of the front sub-region and the rear sub-region is compared to determine the deviation of the overall pattern of the actual laser processing. The specific method for generating the processing compensation parameter m for the galvanometer processing height and the positioning of the galvanometer sub-region is as follows: Compare the front and back sub-area images to obtain the actual processing graphics, dynamically identify the line width of the actual processing graphics, generate the processing graphics center line, and use this line width to determine the edge endpoint position of the center line at the splicing point; According to the theoretical processing graph, the theoretical processing starting endpoints of the rear sub-region after the melt pool compensation calculation at the endpoint of the front sub-region dividing line are set as the a sequence a1, a2, a3..., and the starting endpoints after the actual melt pool compensation are marked as the b sequence b1, b2, b3...; First, the Y-direction error of the galvanometer sub-region positioning is compensated. By comparing the theoretical processing pattern with the endpoints of the b-sequence, the actual segmentation edge of this sub-region is located. The Y-direction deviation of the segmentation edge midpoints of the previous and next sub-regions is compared. The Y-axis positioning of the galvanometer in the sub-region is compensated, and a sub-region compensation model after the galvanometer positioning Y-direction compensation is generated. The compensated b-sequence is recorded as the b' sequence. Secondly, the rotation error of the galvanometer sub-area positioning is compensated. The angle error between the b' sequence dividing line and the a sequence dividing line is identified by the difference in the X-direction coordinates of the corresponding endpoints of the a and b' sequences. The error identified by the segmentation edge line is converted to the rotation angle compensation of the sub-area galvanometer positioning center. The corresponding Y-axis compensation caused by the angle compensation is generated by multiplying the sine value of the identified rotation angle by half of the length of the segmented area. The Y-axis compensation is also added to the Y-axis compensation of the galvanometer positioning. Finally, compensate for the galvanometer processing height error by using the Y-direction coordinate difference of the corresponding endpoints of the a and b' sequences. If the value is smallest near the center of the dividing line and the value on both sides of the dividing line increases continuously, it means that there is a deviation in the galvanometer processing height. If the Y difference of the first pair of endpoints is greater than zero and the Y difference of the last pair of endpoints is less than zero, then the compensation is to reduce the galvanometer processing height. If the Y difference of the first pair of endpoints is less than zero and the Y difference of the last pair of endpoints is greater than zero, then the compensation is to increase the galvanometer processing height. Multiple processing and multiple compensations are performed, and the compensation parameter m is continuously iterated to make most of the laser processing trajectory endpoints connected.

9. The large-area laser milling composite processing method with visual positioning according to claim 8 is characterized in that: In step eight, the sizes of the laser processing molten pools at the division points of the front sub-region and the rear sub-region are compared to determine the compensation parameter n. The specific method is as follows: Compare the front and back sub-area images to obtain the actual processing graphics, dynamically identify the line width of the actual processing graphics, generate the processing graphics center line, and use this line width to determine the edge endpoint position of the center line splicing; Assume that the average line width of the actual processing is 2r, the bending angle of the line segment to be connected on both sides of the dividing line is α, the remaining unprocessed area when the rear line segment is normally compensated is φ1, and the remaining unprocessed area when the line segment is tangent to the front line segment is φ2. According to the recognized connection angle, the inward compensation distance of the line segment is different. When α≥90°, keep processing the line segments of the old sub-region to the endpoint of the dividing line, and shorten the line segments of the new sub-region to the inner region by a distance n1=r~2r, so that the connection is overlapped slightly without expanding the molten pool, and reduce the unprocessed area between the two line segment endpoints and the molten pool, so that φ1≤75%φ2, and obtain the most continuous connection edge possible; When α<90°, keep processing the line segments of the old sub-region to the end point of the dividing line, and shorten the line segments of the new sub-region inward by a distance n2, 5r>n2>2r, φ1≤75%φ2; When the front and rear sub-areas are spliced ​​together, multiple line segments are spliced ​​together. For multiple groups of line segments with α≥90°, n1 is used to compensate, and for multiple groups of line segments with α<90°, n2 is used to compensate.

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