Intelligent leveling device and control method for powder bed additive equipment

Abstract

The present invention relates to the field of additive manufacturing technology, and in particular to an intelligent leveling device and a control method for a powder bed additive device. The intelligent leveling device comprises an equipment bracket, a molding platform, a leveling lifting mechanism, a powder spreading scraper, a powder spreading mechanism and a scraper adjustment mechanism. By adding a laser ranging module at the front end of the powder spreading scraper structure, the distances of four positioning points of a substrate are monitored, and an electromechanical 4-point leveling lifting device is equipped at the bottom of the substrate for leveling to ensure that the substrate remains parallel to the equipment platform; through the scraper adjustment mechanism, relying on the signal fed back by the sensor, the bottom of the rubber strip is adjusted to be parallel to the substrate to ensure the uniformity and horizontality of the powder spreading layer, so as to improve the quality and printing efficiency of the printed parts.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to an intelligent leveling device and a control method for powder bed additive equipment. Background Art

[0002] The existing powder bed additive equipment's substrate needs to be adjusted and tested repeatedly during manual leveling to find the best substrate position, which is time-consuming and inaccurate, leading to low overall printing efficiency. In addition, most powder bed additive equipment's powder scrapers currently use rubber strips, and deviations are inevitable during the installation and replacement of the rubber strips, causing the rubber strips to be non-parallel to the substrate plane, resulting in the powder layer surface not being horizontal, which in turn affects the accuracy and quality of the print. In view of the above problems, this case arises. Summary of the invention

[0003] An object of the present invention is to solve at least the above-mentioned problems through an intelligent leveling device and a control method for a powder bed additive device.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: the intelligent leveling device of the powder bed additive equipment includes an equipment bracket, a molding platform, a leveling lifting mechanism, a powder spreading scraper, a powder spreading mechanism and a scraper adjustment mechanism. A base plate is provided on the top of the molding platform, and the molding platform is lifted and lowered by the leveling lifting mechanism. The powder spreading scraper is located above the base plate, and the powder spreading scraper is moved laterally by the powder spreading mechanism and is leveled by the scraper adjustment mechanism.

[0005] Preferably, the powder spreading mechanism includes a powder spreading rod slide and a transverse bracket, the powder spreading rod slide is driven by a powder spreading servo motor, the transverse bracket is fixedly connected to the slider of the powder spreading rod slide, the powder spreading scraper is arranged on the transverse bracket, the leveling lifting mechanism includes a plurality of lifting and leveling legs and a laser ranging module, the lifting and leveling legs include guide rails, leveling nuts, leveling screws, leveling connecting rods, springs and leveling servo motors, the leveling servo motor drives the leveling screw to rotate, the guide rails and leveling screws are arranged in parallel, the leveling nut is threadedly connected to the leveling screw and is slidably connected to the guide rails, the lower end of the leveling connecting rod is connected to the leveling nut by a floating joint, and the upper end is hinged to the forming platform, the top of the spring is fixedly connected to the forming platform, and the bottom is fixedly connected to the leveling nut, and the laser ranging module is fixedly arranged on the transverse bracket.

[0006] Preferably, the lifting and leveling legs are provided with four and are arranged around the forming platform.

[0007] Preferably, the laser ranging module includes three laser displacement sensors, one of which is located in the middle of the transverse moving bracket, and the other two laser displacement sensors are symmetrically arranged on both sides of the transverse moving bracket.

[0008] Preferably, the scraper adjustment mechanism includes a scraper adjustment servo motor, a worm, a worm wheel, a tool holder, a horizontal detection assembly and an angle sensor. The worm and the worm wheel are rotatably arranged on a transverse bracket. The scraper adjustment servo motor drives the worm to rotate, and the worm and the worm wheel are meshed. The powder spreading scraper is fixed to the bottom of the tool holder, and the tool holder is fixed to the rotating shaft of the worm wheel. The horizontal detection assembly is used to detect the horizontal state of the powder spreading scraper, and the angle sensor is arranged on the rotating shaft of the worm wheel.

[0009] Preferably, the horizontal detection assembly includes a contact displacement sensor, a contact cross bar and a contact screw slide, the contact screw slide is fixed on the equipment bracket, the contact cross bar is horizontally fixed on the slider of the contact screw slide, and the contact displacement sensors are provided with two, which are symmetrically arranged at both ends of the contact cross bar.

[0010] Preferably, it also includes a fine-tuning mechanism, the molding platform also includes a support plate located below the base plate, the fine-tuning mechanism includes an upper wedge block, a lower wedge block, a horizontal displacement sensor, a vertical displacement sensor, a base plate vertical guide mechanism, a fine-tuning screw rod, a fine-tuning nut, a fine-tuning support rod and a fine-tuning servo motor, the base plate vertical guide mechanism includes a vertical guide rod and a vertical guide seat, the vertical guide rod and the top of the upper wedge block are both fixedly connected to the base plate, the vertical guide seat with a guide hole is fixedly mounted on the support plate, the lower end of the vertical guide rod slides in the guide hole, the lower wedge block is slidably connected to the support plate through a dovetail groove, and the fine-tuning nut is fixedly mounted on the lower wedge block , and is threadedly connected with the fine-tuning screw, the fine-tuning servo motor drives the fine-tuning screw to rotate, the lower surface of the upper wedge block and the upper surface of the lower wedge block are inclined planes with the same gradient, the upper wedge block and the lower wedge block are in contact with each other through the inclined planes and can slide relatively along the inclined planes, the horizontal displacement sensor and the vertical displacement sensor are fixed on the support plate, and are respectively used to monitor the horizontal motion error of the lower wedge block and the vertical displacement error between the base plate and the support plate, the top of the fine-tuning support rod is fixedly connected to the base plate, and the bottom is connected to the leveling connecting rod and spring of two oppositely arranged lifting and leveling legs, and the leveling connecting rods and springs of the other two oppositely arranged lifting and leveling legs are connected to the support plate.

[0011] According to the control method of the intelligent leveling device of the powder bed additive equipment, the following steps are included:

[0012] 1. Substrate leveling: The positioning point of the substrate is measured by the laser displacement sensor. The controller reads the signals of the laser displacement sensor after A / D and filtering, judges the signals, and calculates the average height of the four lifting and leveling legs. The internal program of the controller calculates the stroke control strategy, generates a control signal and sends it to the driver of the leveling servo motor by DAC, sends a certain amount of pulses to control the rotation of the leveling servo motor, and the screw nut pair converts the rotational motion of the motor into the linear motion of the leveling nut, thereby adjusting the four lifting and leveling legs to the same target height, realizing the four-point leveling of the molding platform;

[0013] 2. Scraper leveling: The powdering scraper moves to the top of the contact displacement sensor. The contact displacement sensor rises under the drive of the contact screw slide until the contact displacement sensor at one or both ends touches the powdering scraper and stops. At this time, the angle sensor returns to zero. The scraper adjustment servo motor drives the worm to rotate, and the worm gear transmission drives the shaft to rotate, so that the shaft rotates in the opposite direction until the contact displacement sensor at the other end also touches the powdering scraper. The angle of the shaft during this period is recorded by the angle sensor, and then the scraper adjustment servo motor is controlled to reverse half of the angle value, and the scraper leveling is completed.

[0014] Preferably, the software control method of the laser displacement sensor is as follows: the first step is to initialize the system, wake up the connection between the controller and the laser displacement sensor, pull up the pin of the laser displacement sensor, and complete the wake-up response of the laser displacement sensor; the second step is for the controller to send a distance measurement string so that the laser displacement sensor can emit laser light to the substrate; the third step is for the signal recovery system of the laser displacement sensor to process and calculate the recovered optical signal to obtain the distance to the substrate measured by the laser displacement sensor; the fourth step is for the controller to save the measured data and then wait for the calculation of the next position;

[0015] The software control method of the servo motor is as follows: first determine the initial position of the servo motor, that is, the corresponding stator position, and use the controller to take the average value of the distance feedback from the laser displacement sensor, and calculate the difference between the distance of each point on the substrate and the average value to obtain the movement distance of the servo motor, which is then converted into the angle that the servo motor needs to rotate through the controller.

[0016] Preferably, the control system of the intelligent leveling device of the powder bed additive equipment includes a controller, an operation display panel, an external interface unit and an acquisition module. The controller is signal-connected to the operation display panel and the external interface unit. The output interface of the external interface unit is signal-connected to the driver of the leveling servo motor, the scraper adjustment servo motor, the fine-tuning servo motor and the powder spreading servo motor. The laser displacement sensor, the angle sensor, the contact displacement sensor, the horizontal displacement sensor and the vertical displacement sensor are signal-connected to the input interface of the external interface unit through the acquisition module.

[0017] From the above description, it can be seen that the intelligent leveling device and control method of the powder bed additive equipment provided by the present invention have the following beneficial effects: the present invention monitors the distances of the four positioning points of the substrate by adding a laser ranging module to the front end of the powder scraper structure, and equips the bottom of the substrate with an electromechanical 4-point leveling and lifting device for leveling to ensure that the substrate remains parallel to the equipment platform; the present invention also innovatively designs the lifting mechanism of the substrate, and designs a macro / micro lifting mechanism mainly composed of a fine-tuning mechanism, a lead screw, a servo motor and a detection element, which improves the precise displacement of the workbench in the Z-axis direction; the present invention designs a scraper adjustment mechanism, which relies on the signal fed back by the sensor to adjust the bottom of the rubber strip to be parallel to the substrate through the scraper adjustment mechanism, thereby ensuring the uniformity and horizontality of the powder layer to improve the quality of the print and the printing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the three-dimensional structure of the intelligent leveling device of the powder bed additive equipment of the present invention.

[0019] Figure 2 for Figure 1 A magnified schematic diagram of a local area.

[0020] Figure 3 This is a schematic diagram of the structure of the intelligent leveling device of the powder bed additive equipment.

[0021] Figure 4 for Figure 1 Front view of.

[0022] Figure 5 It is the structural diagram of the control system.

[0023] Figure 6 Control flow chart for substrate leveling.

[0024] Figure 7 This is the control flow chart of the laser displacement sensor.

[0025] Figure 8 This is the control flow chart of the servo motor.

[0026] Fig. 9 This is the control flow chart of substrate leveling based on fuzzy PID control algorithm. DETAILED DESCRIPTION

[0027] The present invention is further described below through specific implementation modes.

[0028] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0029] like Figure 1-4 As shown, the intelligent leveling device of the powder bed additive equipment of the present invention comprises an equipment support 1, a molding platform, a leveling lifting mechanism, a powder spreading scraper 4, a powder spreading mechanism and a scraper adjustment mechanism. A substrate 21 is provided on the top of the molding platform, and the molding platform is lifted and lowered by the leveling lifting mechanism. The powder spreading scraper 4 is located above the substrate 21. The powder spreading scraper 4 is moved laterally by the powder spreading mechanism and is leveled by the scraper adjustment mechanism. An equipment housing is provided on the outside of the equipment support 1. The leveling lifting mechanism and the powder spreading mechanism are arranged on the equipment support 1. The substrate 21 on the top of the molding platform is used to carry additives. During the printing process, the molding platform is driven to descend by the leveling lifting mechanism, and the powder spreading scraper 4 is moved laterally to achieve powder spreading. Before printing, the molding platform and the powder spreading scraper 4 need to be leveled. The molding platform is horizontally leveled by the leveling lifting mechanism. After the rubber strip of the powder spreading scraper 4 is replaced, the powder spreading scraper 4 is horizontally leveled by the scraper adjustment mechanism to ensure that the powder spreading scraper 4 and the molding platform remain parallel to ensure the processing quality. There are powder supply bin and waste powder bin at the front and back of the forming platform.

[0030] like Figure 1 and 3 The powder spreading mechanism includes a powder spreading rod slide 51 and a transverse bracket 52. The powder spreading rod slide 51 is driven by a powder spreading servo motor 53. The transverse bracket 52 is fixedly connected to the slider of the powder spreading rod slide 51. The transverse bracket 52 moves under the drive of the powder spreading rod slide 51. Figure 4 The powder spreading scraper 4 is arranged on the transverse moving bracket 52, and the powder spreading scraper 4 moves and spreads powder under the driving of the powder spreading rod slide 51. The leveling and lifting mechanism includes a plurality of lifting and leveling legs 31 and a laser ranging module, such as Figure 2The lifting and leveling leg 31 includes a guide rail 311, a leveling nut 312, a leveling screw 313, a leveling connecting rod 314, a spring 315 and a leveling servo motor 316. The leveling servo motor 316 drives the leveling screw 313 to rotate. The guide rail 311 and the leveling screw 313 are arranged in parallel. The leveling nut 312 is threadedly connected to the leveling screw 313 and is slidably connected to the guide rail 311. The lower end of the leveling connecting rod 314 is connected to the leveling nut 312 through a floating joint, and the upper end is hinged to the forming platform. The top of the spring 315 is fixed to the forming platform, and the bottom is fixed to the leveling nut 312. The laser ranging module is fixed on the transverse moving bracket 52. There are two vermicelli laying rod slides 51, and the transverse moving bracket 52 is movably arranged between the two vermicelli laying rod slides 51. The vermicelli laying rod slide 51 is fixedly arranged on the equipment bracket 1. The vermicelli laying rod slide 51 is driven by the powder laying servo motor 53, which drives the transverse moving bracket 52 to move horizontally and drives the powder laying scraper 4 to lay powder on the molding platform. The laser ranging module moves with the transverse moving bracket 52 to detect the height of each point on the molding platform. Therefore, the transverse moving plane of the laser ranging module is parallel to the equipment base platform, which is used as the basic surface for leveling; the transverse moving process of the laser ranging module The average height of the top surface of the molding platform is calculated, and then the various points are adjusted to the specified average height by lifting the leveling legs 31 to complete the leveling of the molding platform; an electromechanical 4-point leveling device is installed at the bottom of the molding platform for leveling and lifting to ensure that the molding platform and the equipment base platform remain parallel. The specific working method is: the leveling servo motor 316 drives the leveling screw 313 to rotate, converts the rotational motion into the lifting motion of the leveling nut 312, and drives the height adjustment of the molding platform through the connecting rod and spring 315, so that the molding platform as a whole is in the same horizontal plane. Since the height of the four points can be adjusted, the adjustment accuracy is relatively high. At the same time, when the equipment is printing, the molding platform is also driven by the leveling lifting mechanism to lift and lower, and the displacement of the molding platform in the Z-axis direction is accurately controlled.

[0031] There are four lifting and leveling legs 31 arranged around the molding platform. The four positions at the bottom of the molding platform are connected and supported by the leveling connecting rods 314 and springs 315 and the leveling nuts 312, respectively. With the weight of the molding platform, the molding platform can be stably maintained at the set position. The molding platform is supported and leveled by the 4-point leveling device, so that the molding platform is maintained on the same horizontal plane, ensuring the stability of the molding platform and the accuracy of adjustment.

[0032] like Figure 1The laser distance measurement module includes three laser displacement sensors 32, one of which is located in the middle of the transverse bracket 52, and the other two laser displacement sensors 32 are symmetrically arranged on both sides of the transverse bracket 52. The laser displacement sensor 32 in the middle is above the center line of the substrate 21, and the laser displacement sensors 32 on both sides are above the inner side of the edge of the substrate 21. The distance measurement positioning point is located in the middle position of the inner side of the four edges of the substrate 21. When the laser distance measurement module and the transverse bracket 52 scan the substrate 21, the three laser displacement sensors 32 detect the height information of the middle of the four edges of the substrate 21, and support and level the substrate 21 through the 4-point leveling device, so that the substrate 21 is kept on the same horizontal plane.

[0033] like Figure 4 The scraper adjustment mechanism includes a scraper adjustment servo motor 61, a worm 62, a worm wheel 63, a knife holder 64, a horizontal detection component and an angle sensor. The worm 62 and the worm wheel 63 are rotatably arranged on the transverse bracket 52. The scraper adjustment servo motor 61 drives the worm 62 to rotate, and the worm 62 and the worm wheel 63 are meshed. The powder spreading scraper 4 is fixed to the bottom of the knife holder 64, and the knife holder 64 is fixed to the rotating shaft of the worm wheel 63. The horizontal detection component is used to detect the horizontal state of the powder spreading scraper 4, and the angle sensor is arranged on the rotating shaft of the worm wheel 63. The scraper adjustment servo motor 61 is connected to the worm 62 through a coupling, and the worm 62 is connected to the transverse bracket 52 through a deep groove ball bearing. The worm wheel 63 is rotatably arranged on the transverse bracket 52 through a rotating shaft. The knife holder 64 of the powder spreading scraper 4 is fixedly connected to the rotating shaft by bolts, and the angle sensor is used to detect the rotation angle of the rotating shaft of the worm wheel 63.

[0034] The horizontal detection component can have a variety of structural forms, specifically including two technical solutions based on a contact displacement sensor 65 and based on an optical fiber sensor.

[0035] As shown in the accompanying drawings, when the horizontal detection component adopts the technical solution of the contact displacement sensor 65, the specific solution is as follows: Figure 1As shown, the horizontal detection component includes a contact displacement sensor 65, a contact cross bar 66 and a contact screw slide 67, wherein the contact screw slide 67 is fixed on the equipment bracket, the contact cross bar 66 is horizontally fixed on the slider of the contact screw slide 67, and the contact displacement sensor 65 is provided with two, which are symmetrically arranged at the two ends of the contact cross bar 66; its working principle is: the powder spreading scraper 4 moves to the top of the contact displacement sensor 65, and the contact displacement sensor 65 rises under the drive of the contact screw slide 67 until the contact displacement sensor 65 at one end or both ends contacts the powder spreading scraper 4 and stops, at which time the angle sensor Return to zero, drive the worm 62 to rotate through the scraper adjustment servo motor 61, and drive the shaft to rotate through the worm gear transmission, so that the shaft rotates in the opposite direction until the contact displacement sensor 65 at the other end also contacts the powder spreading scraper 4, and record the angle of rotation of the shaft during the period through the angle sensor, and then control the scraper adjustment servo motor 61 to reverse half of the angle value, and the scraper leveling is completed. The contact displacement sensor 65 is used. Since the contact cross bar 66 is in a horizontal state, it does not rely on the leveling of the substrate 21. Therefore, the scraper can be leveled before or after the substrate 21 is leveled, which is more flexible to use.

[0036] When the horizontal detection component adopts the technical solution of optical fiber sensor, the specific solution is as follows: two optical fiber sensors are provided, which are placed at the two ends of the rubber strip. The optical fiber coupler of the optical fiber sensor is installed on the powder scraper 4 through flanges and screws. Inside the two ends of the rubber strip of the powder scraper 4, a reference arm optical fiber is provided at the center part of the circle, and nine sensor arm optical fibers are evenly distributed in the circumferential direction. A reflector is connected to the tail of the optical fiber. The two ends of the rubber strip are respectively connected to the optical fiber coupler through optical fiber flange joints, and the optical fiber coupler is externally connected to a laser emitter and a laser detector. After the substrate leveling of the forming platform is completed, the powder spreading scraper 4 is controlled to move above the substrate 21, and then the substrate 21 is slowly raised by the leveling lifting mechanism until the optical fiber sensor at one end of the rubber strip detects a changed signal, which proves that this end has been in contact with the substrate 21. At this time, the angle sensor is reset to zero, and the scraper adjustment servo motor 61 is used to drive the worm 62 to rotate, and the worm gear transmission is used to drive the shaft to rotate, so that the shaft rotates in the opposite direction until the optical fiber sensor at the other end of the rubber strip detects a changed signal, and the angle of the shaft during the period is recorded by the angle sensor, and then the scraper adjustment servo motor 61 is controlled to reverse half of the angle value, and then the shaft angle is fine-tuned in combination with the difference in the phase change of the optical fibers at both ends of the rubber strip. After the scraper leveling is completed, pre-powdering is performed, and the laser displacement sensor 32 is used to detect whether the thickness of the pre-powder layer is uniform. If it is uneven, the scraper adjustment servo motor 61 is used to control the shaft for fine-tuning.

[0037] like Figure 4The intelligent leveling device of the powder bed additive equipment also includes a fine-tuning mechanism, and the molding platform also includes a support plate 22 located below the substrate 21. The fine-tuning mechanism includes an upper wedge block 71, a lower wedge block 72, a horizontal displacement sensor, a vertical displacement sensor, a substrate vertical guide mechanism, a fine-tuning screw rod, a fine-tuning nut, a fine-tuning support rod and a fine-tuning servo motor 73. The substrate vertical guide mechanism includes a vertical guide rod and a vertical guide seat. The top of the vertical guide rod and the upper wedge block 71 are both fixedly connected to the substrate 21. The vertical guide seat with a guide hole is fixedly mounted on the support plate 22. The lower end of the vertical guide rod slides in the guide hole. The lower wedge block 72 is slidably connected to the support plate 22 through a dovetail groove. The fine-tuning nut is fixedly mounted on the lower wedge block 72 and is threaded with the fine-tuning screw rod. The fine-tuning servo motor 73 drives the fine-tuning screw to rotate, the lower surface of the upper wedge block 71 and the upper surface of the lower wedge block 72 are inclined planes with the same gradient, the upper wedge block 71 and the lower wedge block 72 are in contact with each other through the inclined planes and can slide relatively along the inclined planes, the horizontal displacement sensor and the vertical displacement sensor are fixed on the support plate 22, and are respectively used to monitor the horizontal motion error of the lower wedge block 72 and the vertical displacement error between the base plate 21 and the support plate 22, the top of the fine-tuning support rod is fixedly connected to the base plate 21, and the bottom is connected to the leveling connecting rod 314 and the spring 315 of two oppositely arranged lifting and leveling legs 31, and the leveling connecting rod 314 and the spring 315 of the other two oppositely arranged lifting and leveling legs 31 are connected to the support plate 22. The fine-tuning servo motor 73 is fixedly connected to the support plate 22 through the motor seat, and its output shaft is connected to the fine-tuning screw through a coupling and placed horizontally, the supports at both ends of the fine-tuning screw are fixedly connected to the upper surface of the support plate 22, and the fine-tuning nut is sleeved inside the lower wedge block 72 and fixedly connected thereto, so that the fine-tuning screw drives the lower wedge block 72 to move horizontally, and the protruding part (dovetail slider) at the lower end of the lower wedge block 72 is connected to the support plate 22 through a dovetail groove, and the direction of the dovetail groove is consistent with the transmission direction of the screw, which plays a guiding role in the movement of the wedge block. The fine-tuning servo motor 73 drives the fine-tuning screw to rotate, and then drives the fine-tuning nut. The fine-tuning nut drives the lower wedge block 72 to move horizontally and linearly along the dovetail groove. The inclined surfaces between the upper wedge block 71 and the lower wedge block 72 are also provided with a dovetail slider and a dovetail groove structure that cooperate with each other, that is, one of the wedge blocks is provided with a dovetail slider and the other wedge block is provided with a dovetail groove, and the movement direction of the dovetail slider in the dovetail groove is parallel to the inclined surface. The upper wedge block 71 and the lower wedge block 72 rely on the dovetail groove structure to keep their inclined surfaces in contact at all times, so that the horizontal movement of the lower wedge block 72 is converted into the vertical lifting movement of the upper wedge block 71. The slope ratio of the contact inclined surface of the wedge block is designed to be 1:A, so the horizontal displacement of the lower wedge block 72 is A times the vertical displacement of the upper wedge block 71, and A can be 50-60. There are four vertical guide mechanisms for the substrate, which are arranged at the four corners of the forming platform and are used to connect the substrate 21 and the support plate 22. The substrate 21 and the support plate 22 are restricted to move only in the vertical direction relative to each other. The lower wedge block 72 is slidably connected to the support plate 22 through a dovetail groove, so the lower wedge block 72 can only move laterally relative to the top surface of the support plate 22.The lifting and lowering movement of the molding platform along the Z-axis direction in the molding chamber is divided into two types of movement: one is a rapid lifting and lowering movement, which is driven by the lifting and leveling legs 31 installed around the molding platform. The rapid lifting and lowering movement can be used to quickly rise the molding platform after processing, and can also be used for the lifting and lowering of the molding platform for four-point leveling; the other is a small displacement movement of the workbench downward before powder laying, which is completed by the fine-tuning mechanism; the fine-tuning servo motor 73 is equipped with a brake. When the brake is working, the fine-tuning screw rod is locked, which can limit the relative movement of the upper wedge block 71 and the lower wedge block 72. Before the molding platform is leveled, the brake of the fine-tuning servo motor 73 is started. During the leveling process, the relative position of the base plate 21 and the support plate 22 does not change; the four lifting and leveling legs 31 are also provided with brakes, which can lock the leveling screw rod 313, and then lock the position of the leveling nut 312, and because two of them are lifted in opposite directions The leveling legs 31 are directly connected to the support plate 22, and the other two opposite lifting and leveling legs 31 are directly connected to the base plate 21. The two sets of lifting and leveling legs 31 are locked alternately at different times, so that when the forming platform is spreading powder layer by layer, one of the base plate 21 and the support plate 22 is locked in the Z-axis direction. The vertical distance between the base plate 21 and the support plate 22 is fine-tuned by the fine-tuning servo motor 73, fine-tuning screw rod, fine-tuning nut and upper and lower wedge blocks 72 of the fine-tuning mechanism, so as to achieve the purpose of moving the unlocked base plate 21 or the support plate 22 downward. The specific working process is as follows: After the support plate 22 is locked, the base plate 21 moves slightly downward under the drive of the fine-tuning mechanism. After the powder spreading scraper 4 completes the powder spreading, the support plate 22 is unlocked, while the base plate 21 is locked. The support plate 22 moves slightly downward under the drive of the fine-tuning mechanism, and the above process is repeated to achieve layer-by-layer powder spreading.

[0038] A control method for an intelligent leveling device of a powder bed additive device comprises the following steps:

[0039] 1. Baseboard leveling: Figure 6 The positioning point of the substrate 21 is measured by the laser displacement sensor 32. The controller reads the signals of the laser displacement sensor 32 after A / D and filtering processing, judges the signals, and calculates the average height of the four lifting and leveling legs 31. The internal program of the controller calculates the stroke control strategy, generates a control signal and sends it to the driver of the leveling servo motor 316 by DAC, sends a certain amount of pulses to control the rotation of the leveling servo motor 316, and the screw nut pair converts the rotational motion of the motor into the linear motion of the leveling nut 312, thereby adjusting the four lifting and leveling legs 31 to the same target height, and realizing the four-point leveling of the molding platform;

[0040] 2. Scraper leveling: The powdering scraper 4 moves to the top of the contact displacement sensor 65. The contact displacement sensor 65 rises under the drive of the contact screw slide 67 until the contact displacement sensor 65 at one or both ends contacts the powdering scraper 4 and then stops. At this time, the angle sensor returns to zero, and the scraper adjustment servo motor 61 drives the worm 62 to rotate, and the worm gear transmission drives the shaft to rotate, so that the shaft rotates in the opposite direction until the contact displacement sensor 65 at the other end also contacts the powdering scraper 4. The angle of the shaft rotation during this period is recorded by the angle sensor, and then the scraper adjustment servo motor 61 is controlled to reverse half of the angle value, and the scraper leveling is completed.

[0041] After leveling, during printing, the precise displacement in the Z-axis direction is achieved by the movement of the fine-tuning mechanism along the Z-axis in the molding chamber: after the support plate 22 is locked, the substrate 21 is displaced downward under the drive of the fine-tuning mechanism, and after the powder spreading scraper 4 completes a layer of powder spreading, the support plate 22 is unlocked and the substrate 21 is locked, and the support plate 22 is driven by the fine-tuning mechanism to move slightly downward, and the above process is repeated to achieve layer-by-layer powder spreading. The inchworm-like movement of the fine-tuning mechanism along the Z-axis in the molding chamber directly ensures that the motion error of the powder spreading molding platform can be controlled within ±0.5um each time.

[0042] The software control method of the laser displacement sensor 32 is as follows: Figure 7 The first step is to initialize the system, wake up the connection between the controller and the laser displacement sensor 32, pull up the pin of the laser displacement sensor 32, and complete the wake-up response of the laser displacement sensor 32; the second step is for the controller to send a distance measurement string so that the laser displacement sensor 32 can emit laser light to the substrate 21; the third step is for the signal recovery system of the laser displacement sensor 32 to process and calculate the recovered optical signal to obtain the distance to the substrate 21 measured by the laser displacement sensor 32; the fourth step is for the controller to save the measured data and wait for the calculation of the next position;

[0043] The software control method of the servo motor is as follows: Figure 8 First, determine the initial position of the servo motor, that is, the corresponding stator position. The controller averages the distance fed back by the laser displacement sensor 32, and calculates the difference between the distance of each point of the substrate 21 and the average value to obtain the movement distance of the servo motor, which is then converted into the angle that the servo motor needs to rotate through the controller. In the program of the controller controlling the movement of the servo motor, forward and reverse rotation should be taken into account. When the measured distance is greater than the target distance, the servo motor needs to reverse upward, otherwise forward rotation downward, so as to realize the function of automatic leveling of the substrate 21.

[0044] like Figure 5The control system of the intelligent leveling device of the powder bed additive equipment includes a controller, an operation display panel, an external interface unit and an acquisition module. The controller is connected to the operation display panel and the external interface unit by signal. The output interface of the external interface unit is connected to the driver signal of the leveling servo motor 316, the scraper adjustment servo motor 61, the fine-tuning servo motor 73 and the powder spreading servo motor 53. The laser displacement sensor 32, the angle sensor, the contact displacement sensor 65, the horizontal displacement sensor and the vertical displacement sensor are connected to the input interface of the external interface unit through the acquisition module. The system hardware consists of three parts: control, acquisition and execution. In the control part, STM312F103ZET6 is selected as the controller. The external interface unit contains 112 I / O ports, which are matched with the 512kB FLASH (flash memory) of the W25Q64 chip to meet the development requirements. The acquisition part includes an acquisition module, a laser displacement sensor 32, an angle sensor, a contact displacement sensor 65, and an optical fiber sensor. The acquisition module includes A / D, transmission, filtering and other units. According to the analog signal output of the sensor, a suitable ADC (analog-to-digital converter) is selected, such as the 24-bit high-precision HX711. The execution part consists of servo motors and their servo motor drivers, brakes, ball screws, worm gears, guide rods, etc. In terms of software, the leveling method and process are programmed through Keil5 software, and the host computer is developed with the help of LabVIEW. The communication includes two parts: between STM312 and the operation panel and between STM312 and the host computer. Communication can be achieved through RS2312, RS485, and USB serial ports.

[0045] In order to ensure the accuracy of leveling, the leveling control system adopts a fully closed-loop structure. Fig. 9The leveling algorithm of the leveling system adopts a fuzzy PID control algorithm based on particle swarm optimization. When the substrate is leveled, the ideal state is that the surface of the substrate 21 is parallel to the platform. The deviation e of the laser sensor and its deviation change rate de / dt are used as the input variables of the fuzzy PID control. Δkp, Δki, and Δkd are the correction values ​​of the PID parameters. During operation, the control parameters are corrected in real time by continuously detecting the distance deviation to adapt to the requirements of the control parameters for the position deviation at different times. A larger threshold value e1 and a smaller threshold value e2 are set here, and the deviation value is compared with the threshold value to determine which control method to adopt. The present invention adds a laser ranging module to the front end of the powder spreading scraper 4 structure to monitor the distances of the four positioning points of the substrate 21, and equips the bottom of the substrate 21 with an electromechanical 4-point leveling and lifting device for leveling to ensure that the substrate 21 remains parallel to the equipment platform; the present invention also innovatively designs the lifting mechanism of the substrate 21, and designs a macro / micro lifting mechanism mainly composed of a fine-tuning mechanism, a lead screw, a servo motor and a detection element, which improves the precise displacement of the workbench in the Z-axis direction; the present invention designs a scraper adjustment mechanism, which relies on the signal fed back by the sensor to adjust the bottom of the rubber strip to be parallel to the substrate 21 through the scraper adjustment mechanism, thereby ensuring the uniformity and horizontality of the powder spreading layer, so as to improve the quality of the printed parts and the printing efficiency.

[0046] The above are only some specific implementation methods of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. An intelligent leveling device for a powder bed additive device, characterized in that: It includes an equipment support, a molding platform, a leveling and lifting mechanism, a powder spreading scraper, a powder spreading mechanism and a scraper adjustment mechanism. A base plate is provided on the top of the molding platform. The molding platform is lifted and lowered by the leveling and lifting mechanism. The powder spreading scraper is located above the base plate. The powder spreading scraper is moved laterally by the powder spreading mechanism and is leveled by the scraper adjustment mechanism. The powder spreading mechanism includes a powder spreading rod slide and a transverse bracket. The powder spreading rod slide is driven by a powder spreading servo motor. The transverse bracket is fixedly connected to the slider of the powder spreading rod slide. The powder spreading scraper is arranged on the transverse bracket. The lifting mechanism includes a plurality of lifting and leveling legs and a laser ranging module. The lifting and leveling legs include a guide rail, a leveling nut, a leveling screw, a leveling connecting rod, a spring and a leveling servo motor. The leveling servo motor drives the leveling screw to rotate. The guide rail and the leveling screw are arranged in parallel. The leveling nut is threadedly connected to the leveling screw and is slidably connected to the guide rail. The lower end of the leveling connecting rod is connected to the leveling nut through a floating joint, and the upper end is hinged to the molding platform. The top of the spring is fixedly connected to the molding platform, and the bottom is fixedly connected to the leveling nut. The laser ranging module is fixedly arranged on the transverse moving bracket. The scraper adjustment mechanism includes a scraper adjustment servo motor, a worm, a worm wheel, a tool holder, a horizontal detection component and an angle sensor. The worm and the worm wheel are rotatably arranged on the transverse support. The scraper adjustment servo motor drives the worm to rotate, and the worm and the worm wheel are meshed. The powder spreading scraper is fixed to the bottom of the tool holder, and the tool holder is fixed to the rotating shaft of the worm wheel. The horizontal detection component is used to detect the horizontal state of the powder spreading scraper, and the angle sensor is arranged on the rotating shaft of the worm wheel. The horizontal detection assembly includes a contact displacement sensor, a contact cross bar and a contact screw slide, wherein the contact screw slide is fixed on the equipment bracket, the contact cross bar is horizontally fixed on the slider of the contact screw slide, and the contact displacement sensor is provided with two, which are symmetrically arranged at both ends of the contact cross bar; The intelligent leveling device of the powder bed additive equipment also includes a fine-tuning mechanism, and the molding platform also includes a support plate located below the substrate. The fine-tuning mechanism includes an upper wedge, a lower wedge, a horizontal displacement sensor, a vertical displacement sensor, a substrate vertical guide mechanism, a fine-tuning screw rod, a fine-tuning nut, a fine-tuning support rod and a fine-tuning servo motor. The substrate vertical guide mechanism includes a vertical guide rod and a vertical guide seat. The top of the vertical guide rod and the upper wedge are both fixedly connected to the substrate. The vertical guide seat with a guide hole is fixedly installed on the support plate. The lower end of the vertical guide rod slides in the guide hole. The lower wedge is slidably connected to the support plate through a dovetail groove. The fine-tuning nut is fixedly installed. On the lower wedge block, and threadedly connected with the fine-tuning screw, the fine-tuning servo motor drives the fine-tuning screw to rotate, the lower surface of the upper wedge block and the upper surface of the lower wedge block are inclined surfaces with the same gradient, the upper wedge block and the lower wedge block are in contact with each other through the inclined surfaces and can slide relatively along the inclined surfaces, the horizontal displacement sensor and the vertical displacement sensor are fixed on the support plate, and are respectively used to monitor the horizontal motion error of the lower wedge block and the vertical displacement error between the base plate and the support plate, the top of the fine-tuning support rod is fixedly connected to the base plate, and the bottom is connected to the leveling connecting rod and spring of two oppositely arranged lifting and leveling legs, and the leveling connecting rod and spring of the other two oppositely arranged lifting and leveling legs are connected to the support plate.

2. The intelligent leveling device for powder bed additive equipment according to claim 1, characterized in that: The lifting and leveling legs are provided with four and are arranged around the forming platform.

3. The intelligent leveling device for powder bed additive equipment according to claim 2, characterized in that: The laser distance measurement module includes three laser displacement sensors, one of which is located in the middle of the transverse moving bracket, and the other two laser displacement sensors are symmetrically arranged on both sides of the transverse moving bracket.

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