SMT quality control method and system

Abstract

The invention relates to the technical field of SMT, and discloses an SMT quality control method and system, and the method comprises the steps: calculating a PCB rotation deviation angle and a PCB translation deviation, and superposing the PCB rotation deviation angle and the PCB translation deviation for a target mounting point coordinate, and obtaining a component position deviation value; when the position deviation value of the component exceeds an allowable deviation threshold value, calculating an additional displacement value generated by the rotation action, and deducting the additional displacement value from the position deviation value of the component to obtain a comprehensive compensation displacement value; and a rotation instruction is sent to a rotating head servo motor according to the component position deviation amount, a stepping pulse signal is sent to a gantry stepping motor according to the comprehensive compensation displacement amount, and a rotating head and a gantry execute compensation actions in parallel to complete component alignment. The problem that in the prior art, fixed coordinate mapping cannot adapt to PCB position changes is solved, the double-gantry cooperation efficiency is improved, and the overall production period is shortened.

Description

Technical Field

[0001] This invention relates to the field of SMT (Surface Mount Technology) technology, and in particular to an SMT quality control method and system. Background Technology

[0002] As a core process in electronic manufacturing, surface mount technology (SMT) assembly directly impacts product quality and production efficiency. Current technologies often employ single-point or dual-point measurement methods for component position detection, which can only constrain translational freedom but cannot simultaneously determine rotational orientation. This leads to accumulated angular deviations that affect assembly accuracy. Coordinate system transformations typically use fixed mapping relationships, failing to consider the actual mounting deviation of the PCB on the conveyor belt. When the PCB rotates or translates, it's impossible to accurately calculate the true deviation between the component and the target pad.

[0003] During alignment and correction, existing methods treat rotation compensation and translation compensation as independent actions, ignoring the objective fact that there is an eccentricity between the rotation center of the rotating head and the center of the component. This results in the additional displacement caused by the rotation not being corrected, and positional errors still exist after compensation. For high-speed pick-and-place machines equipped with dual gantry machines, the existing scheduling strategy uses a static area division method to allocate tasks, without considering the differences in the actual alignment and correction time of each component. This causes one gantry to have an excessively long operation time while the other gantry completes its work ahead of time and enters an idle waiting state, reducing the collaborative efficiency of the dual gantry machines and the overall production capacity. Summary of the Invention

[0004] This invention provides a method and system for SMT placement quality control. This invention solves the problem that fixed coordinate mapping in the prior art cannot adapt to changes in PCB position, and improves the efficiency of dual-gantry collaboration and the overall production cycle.

[0005] In a first aspect, the present invention provides a method for SMT (Surface Mount Technology) component placement quality control, the method comprising: Calculate the PCB rotation deviation angle and the PCB translation deviation, and superimpose the PCB rotation deviation angle and the PCB translation deviation onto the target mounting point coordinates to obtain the component position deviation. When the position deviation of the component exceeds the allowable deviation threshold, the additional displacement generated by the rotation action is calculated and the additional displacement is subtracted from the position deviation of the component to obtain the comprehensive compensation displacement. The rotating head servo motor is sent a rotation command based on the component position deviation, and the gantry stepper motor is sent a stepping pulse signal based on the comprehensive compensation displacement. The rotating head and gantry perform compensation actions in parallel to complete the component alignment.

[0006] In conjunction with the first aspect, in a first implementation of the first aspect of the present invention, before calculating the PCB rotation deviation angle and the PCB translation deviation, the method further includes: The center pixel coordinates of four Mark reference points in the PCB are extracted from the image acquired by the fixed camera, and edge detection is performed on the components in the image to obtain the pixel coordinates of the center points of the components. Calculate the first pixel distance, second pixel distance, third pixel distance, and fourth pixel distance between the pixel coordinates of the center point of the component and the center pixel coordinates of the four Mark reference points, respectively.

[0007] In conjunction with the first aspect, in a second implementation of the first aspect of the present invention, the PCB rotation deviation angle and the PCB translation deviation are calculated, and the PCB rotation deviation angle and the PCB translation deviation are superimposed on the target mounting point coordinates to obtain the component position deviation, including: Multiply the center pixel coordinates of the four Mark reference points and the pixel coordinates of the component center point by the camera's pixel scale factor to obtain the measured physical coordinates of the four Mark reference points and the physical coordinates of the component center point. Calculate the PCB rotation deviation angle and PCB translation deviation based on the measured physical coordinates; The target position coordinates are obtained by superimposing the PCB rotation deviation angle and the PCB translation deviation on the target mounting point coordinates. The component position coordinates are obtained by superimposing the physical coordinates of the component center point on the camera offset in the machine coordinate system. The component position deviation is calculated based on the target position coordinates and the component position coordinates.

[0008] In conjunction with the first aspect, in a third implementation of the first aspect of the present invention, calculating the PCB rotation deviation angle and the PCB translation deviation based on the measured physical coordinates includes: Calculate the first ordinate difference and the first abscissa difference between the measured physical coordinates of the Mark reference point, and calculate the second ordinate difference and the second abscissa difference in the machine coordinate system; Calculate the PCB rotation deviation angle based on the first vertical coordinate difference, the first horizontal coordinate difference, the second vertical coordinate difference, and the second horizontal coordinate difference; Calculate the difference between the third ordinate and the third abscissa between the measured physical coordinates and the theoretical coordinates of the Mark reference point; Multiply the difference between the third vertical coordinate and the difference between the third horizontal coordinate by the cosine and sine of the PCB rotation deviation angle, respectively, to obtain the X-axis translation deviation. Multiply the difference between the third vertical coordinate and the difference between the third horizontal coordinate by the negative sine and cosine of the PCB rotation deviation angle, respectively, to obtain the Y-axis translation deviation. Generate the PCB translation deviation based on the X-axis translation deviation and the Y-axis translation deviation.

[0009] In conjunction with the first aspect, in a fourth implementation of the first aspect of the present invention, when the positional deviation of the component exceeds the allowable deviation threshold, the additional displacement generated by the rotational action is calculated and the additional displacement is subtracted from the positional deviation of the component to obtain a comprehensive compensation displacement, including: When the position deviation of the component exceeds the allowable deviation threshold, the radial position vector after rotation is calculated by rotation transformation based on the radial position vector of the component center relative to the rotation axis and the rotation angle deviation, and the difference between the radial position vectors before and after rotation is calculated to obtain the additional displacement generated by the rotation action. The X-axis translational deviation of the component position deviation is subtracted from the X-axis component of the additional displacement to obtain the compensation displacement of the gantry X-axis. The Y-axis translational deviation is subtracted from the Y-axis component of the additional displacement to obtain the compensation displacement of the gantry Y-axis. The compensation displacement of the X-axis of the gantry and the compensation displacement of the Y-axis of the gantry are taken as the comprehensive compensation displacement.

[0010] In conjunction with the first aspect, in a fifth implementation of the first aspect of the present invention, a rotation command is sent to the rotary head servo motor according to the component position deviation, and a stepping pulse signal is sent to the gantry stepper motor according to the comprehensive compensation displacement. The rotary head and the gantry perform compensation actions in parallel to complete component alignment, including: Based on the rotation angle deviation in the component position deviation, a rotation command is sent to the rotary head servo motor. Divide the compensation displacement of the gantry X-axis in the comprehensive compensation displacement by the step distance of the X-axis stepper motor to obtain the X-axis step pulse count. Divide the compensation displacement of the gantry Y-axis in the comprehensive compensation displacement by the step distance of the Y-axis stepper motor to obtain the Y-axis step pulse count. Send the corresponding step pulse signals to the gantry X-axis and gantry Y-axis stepper motors. The rotary head servo motor and the gantry stepper motor perform rotation compensation and translation compensation actions in parallel, and calculate the maximum value of the rotation time and the translation time as the alignment correction time.

[0011] In conjunction with the first aspect, in a sixth implementation of the first aspect of the present invention, the SMT placement quality control method further includes: The average of the minimum and maximum X-coordinates of the PCB in the machine coordinate system is calculated as the centerline position, and the X-coordinates of the component mounting positions are compared with the centerline position. Components with X-coordinates less than the centerline position are assigned to the first gantry, and components with X-coordinates greater than or equal to the centerline position are assigned to the second gantry. Calculate the moving distance of each component from the material position to the placement position, divide the fixed material suction time and the moving distance by the maximum moving speed of the first gantry or the second gantry, the fixed placement time and the alignment correction time, and sum them up to obtain the estimated total operation time of the first gantry and the estimated total operation time of the second gantry. Calculate the difference in operating time between the estimated total operating time of the first gantry and the estimated total operating time of the second gantry; The alternating work cycle of the first gantry and the second gantry is set according to the difference in the work time, and the cycle scheduling is implemented.

[0012] In conjunction with the first aspect, in the seventh implementation of the first aspect of the present invention, setting the alternating working cycle of the first gantry and the second gantry based on the work time difference and implementing periodic scheduling includes: Based on the difference in the operation time, select components whose X-axis coordinate distance from the centerline position is less than a preset distance threshold and whose alignment correction time is greater than the median. Calculate the difference change amount for transferring the component. When the difference change amount is negative, perform the transfer operation and update the gantry task set. Calculate the alternating working cycle of the gantry. The first gantry starts to perform placement at the initial moment, and the second gantry performs material preparation and suction simultaneously. When the first gantry completes placement, the second gantry starts placement and the first gantry suctions material simultaneously. The ratio of the number of completed components to the total allocated quantity of the first gantry is calculated as the completion progress ratio of the first gantry. At the same time, the completion progress ratio of the second gantry is calculated, and the progress ratio difference is calculated based on the completion progress ratio of the first gantry and the completion progress ratio of the second gantry. Based on the progress ratio difference, a preset number of components with the shortest alignment and correction time are taken from the end of the remaining task queue of the gantry with a large completion progress ratio and transferred to the gantry with a small completion progress ratio.

[0013] In conjunction with the first aspect, in the eighth implementation of the first aspect of the present invention, the ratio of the number of completed components in the first gantry to the total allocated quantity is calculated as the completion progress ratio of the first gantry; simultaneously, the completion progress ratio of the second gantry is calculated; and a progress ratio difference is calculated based on the completion progress ratios of the first and second gantry, including: The completion progress percentage of the first gantry is obtained by dividing the number of components that have been mounted on the first gantry by the total number of components allocated to the first gantry. Similarly, the completion progress percentage of the second gantry is obtained by dividing the number of components that have been mounted on the second gantry by the total number of components allocated to the second gantry. Calculate the difference between the progress percentages of the first gantry and the second gantry.

[0014] Secondly, the present invention provides an SMT (Surface Mount Technology) quality control system, the SMT quality control system comprising: The deviation calculation module is used to calculate the PCB rotation deviation angle and the PCB translation deviation, and to superimpose the PCB rotation deviation angle and the PCB translation deviation on the target mounting point coordinates to obtain the component position deviation. The comprehensive compensation module is used to calculate the additional displacement generated by the rotation action and subtract the additional displacement from the component position deviation when the component position deviation exceeds the allowable deviation threshold, so as to obtain the comprehensive compensation displacement. The execution module is used to send rotation commands to the rotary head servo motor according to the component position deviation, and send stepping pulse signals to the gantry stepper motor according to the comprehensive compensation displacement. The rotary head and gantry perform compensation actions in parallel to complete the component alignment.

[0015] The technical solution provided by this invention establishes the spatial geometric relationship between the component center and four Mark reference points on the PCB through multi-point distance measurement. The four-point distance vector can simultaneously constrain the translational and rotational degrees of freedom of the component, eliminating the measurement ambiguity of the rotation angle compared to the single-point or double-point measurement of the prior art. By comparing the measured physical coordinates of the Mark reference points with the theoretical coordinates of the machine coordinate system, the rotational deviation angle and translational deviation of the PCB are calculated, and these deviations are superimposed on the target mounting point coordinates for correction, realizing dynamic compensation for the actual mounting deviation of the PCB and solving the problem that the fixed coordinate mapping in the prior art cannot adapt to changes in the PCB position. In the alignment correction stage, this invention calculates the additional displacement generated by the rotation action based on the radial position vector of the component center relative to the rotation axis, and subtracts this additional displacement from the translational deviation in the component position deviation to obtain the actual compensation displacement that the gantry needs to perform. This achieves decoupled control of rotational compensation and translational compensation, avoiding the problem of over- or under-compensation caused by ignoring the rotational coupling effect in the prior art. In terms of dual-gantry scheduling, this invention incorporates the alignment correction time of each component as an attribute parameter into the operation time calculation. Through dynamic task redistribution, the difference in the expected total operation time between the two gantry is kept within the load balancing threshold. During operation, the progress ratio is monitored in real time. When the progress difference exceeds the preset threshold, the component with shorter correction time is immediately transferred to the lagging gantry, ensuring that the two gantry always complete synchronously and avoiding unilateral idle waiting. Compared with the static area division strategy of the prior art, this invention improves the collaborative efficiency of dual-gantry and the overall production cycle. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the steps of the SMT placement quality control method in an embodiment of the present invention; Figure 2 This is a schematic diagram of the SMT placement quality control system in an embodiment of the present invention. Detailed Implementation

[0018] This invention provides an SMT (Surface Mount Technology) assembly quality control method and system. The terms "first," "second," "third," "fourth," etc. (if present)," in the specification, claims, and accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" or "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0019] For ease of understanding, the specific process of the embodiments of the present invention is described below. Please refer to [link / reference]. Figure 1 One embodiment of the SMT placement quality control method in this invention includes: Step S1: Calculate the PCB rotation deviation angle and PCB translation deviation, and superimpose the PCB rotation deviation angle and PCB translation deviation onto the target mounting point coordinates to obtain the component position deviation. Step S2: When the component position deviation exceeds the allowable deviation threshold, calculate the additional displacement generated by the rotation action and subtract the additional displacement from the component position deviation to obtain the comprehensive compensation displacement. Step S3: Send a rotation command to the rotary head servo motor according to the component position deviation, and send a stepping pulse signal to the gantry stepper motor according to the comprehensive compensation displacement. The rotary head and gantry perform compensation actions in parallel to complete the component alignment.

[0020] In one specific embodiment, before calculating the PCB rotation deviation angle and the PCB translation deviation, the method further includes: The center pixel coordinates of four Mark reference points in the PCB are extracted from the image acquired by the fixed camera, and edge detection is performed on the components in the image to obtain the pixel coordinates of the center points of the components. Calculate the first pixel distance, second pixel distance, third pixel distance, and fourth pixel distance between the pixel coordinates of the component center point and the center pixel coordinates of the four Mark reference points.

[0021] In this embodiment, image preprocessing operations are performed on the image data captured by a fixed camera, including grayscale conversion, filtering and noise reduction, and contrast enhancement. For the identification of the Mark reference points, a grayscale threshold segmentation algorithm is used to distinguish high-contrast areas in the image from the background. Morphological operations such as erosion and dilation are used to enhance the boundary features of the Mark graphics, thereby locating the outer contour of the Mark points. A contour centroid calculation algorithm is used, which calculates the geometric moments of the extracted closed boundary regions and the ratio of their first-order central moment to their zero-order moment, to obtain the center pixel coordinates of each Mark point, denoted as (u1, v1), (u2, v2), (u3, v3), and (u4, v4), where u represents the horizontal coordinate of the image pixel, v represents the vertical coordinate of the image pixel, and the four points correspond to the theoretical installation positions of the upper left, upper right, lower right, and lower left corners of the PCB, respectively, and have a symmetrical geometric arrangement in the image. For the identification of the component body region, edge detection is performed on the image. The Canny edge detection algorithm is used to perform multi-level filtering and non-maximum suppression on the gradient information of the image to extract the edge contour of the component. For the extracted edge contour, contour closure analysis and main contour selection mechanism are used to select the main contour boundary with the largest area or that matches the shape template of the component, and the geometric center position of the main contour is calculated, denoted as (u c , v c ), which serves as the center pixel coordinates of the component. Using the Euclidean distance formula between the center coordinates and the center pixel coordinates of the Mark point, the distances to the first, second, third, and fourth pixels are calculated, i.e., d1 = √[(u c -u1) 2 +(v c -v1) 2 ],d2=√[(u c -u2) 2 +(v c -v2) 2 ],d3=√[(u c -u3) 2 +(v c -v3) 2 ],d4=√[(u c -u4) 2 +(vc -v4) 2 These four distances represent the geometric distances from the center point of the component to the four reference Mark points in the image coordinate system. The above calculation results constitute a distance vector D = [d1, d2, d3, d4], which describes the spatial distribution of the component in the image relative to the corner points of the PCB boundary.

[0022] Before calculating the PCB rotation deviation angle and PCB translation deviation, the process includes: constructing a four-point distance ratio based on the first pixel distance, second pixel distance, third pixel distance, and fourth pixel distance; calculating the distance ratio between adjacent Mark reference points and the distance ratio between diagonal Mark reference points; determining the component posture abnormality type by the deviation of the ratio; when the deviation of the distance ratio exceeds the preset posture abnormality threshold, calculating the main offset direction of the component based on the difference between the maximum and minimum pixel distances in the four-point distance vector; determining whether the dominant deviation component of the component position deviation is translation deviation or rotation deviation; and increasing the calculation weight of the PCB rotation deviation angle when the dominant deviation component is rotation deviation, and increasing the calculation weight of the PCB translation deviation when the dominant deviation component is translation deviation.

[0023] In one specific embodiment, the PCB rotation deviation angle and PCB translation deviation are calculated, and the PCB rotation deviation angle and PCB translation deviation are superimposed on the target mounting point coordinates to obtain the component position deviation, including: Multiply the center pixel coordinates of the four Mark reference points and the pixel coordinates of the component center point by the camera's pixel scale factor to obtain the measured physical coordinates of the four Mark reference points and the physical coordinates of the component center point. Calculate the PCB rotation deviation angle and PCB translation deviation based on the measured physical coordinates; The target position coordinates are obtained by superimposing the PCB rotation deviation angle and PCB translation deviation on the coordinates of the target mounting point. The component position coordinates are obtained by superimposing the physical coordinates of the component center point on the offset of the camera in the machine coordinate system. The component position deviation is calculated based on the target position coordinates and the component position coordinates.

[0024] In this embodiment, the center pixel coordinates (u1,v1), (u2,v2), (u3,v3), and (u4,v4) of four Mark reference points and the pixel coordinates (u4,v4) of the component center point are used. c ,v cCombined with the pixel scale factors px and py obtained during the camera calibration phase, all pixel coordinates are mapped to measured physical coordinates in the camera coordinate system. Here, px and py represent the actual physical length of each pixel in the X and Y directions, respectively, in millimeters per pixel. During the conversion, the horizontal component of each pixel coordinate is multiplied by px, and the vertical component by py, resulting in (X1,Y1) = (u1·px, v1·py), (X2,Y2) = (u2·px, v2·py), (X3,Y3) = (u3·px, v3·py), and (X4,Y4) = (u4·px, v4·py). The physical coordinates of the component's center point are (X... c ,Y c ) = (u c ·px, v c This unifies all key data to the physical quantity dimension. Based on the theoretical coordinates of the Mark points in the PCB design, the rotational deviation angle and global translational deviation of the PCB at the current mounting station are calculated. Taking the line connecting Mark points M1 and M2 as a reference, the direction vector of this line is calculated in both the image physical coordinate system and the machine coordinate system. The difference between the two directions is then used to obtain the difference in the rotational angle, where the direction angle difference is expressed as tan(α). P c β )=[(Y2 Y1) (Y m2 Y m1 )] / [(X2 X1) (X m2 X m1 Then, the rotational deviation angle α is obtained from the arctangent function. p c β The measured physical coordinates of Mark point M1 are rotated around this rotation angle and compared with its theoretical machine coordinates to obtain the translational deviation ΔX of the PCB. p c β and ΔY p c β Its expression is ΔX p c β = (X1 X m1 )·cos(α p c β ) + (Y1 Y m1 )·sin(α p c β ), ΔY p c β = (X1 X m1 )·sin(α p c β ) + (Y1 Y m1 )·cos(α p c β To convert the target placement point coordinates from the PCB design coordinate system to the machine coordinate system in the current actual assembly state, the original design coordinates (X...) are... t ,Y t ,θ t Spatial reconstruction is performed by superimposing rotational and displacement deviations, with the specific transformation relationship being X. t ′ = X t ·cos(α p c β ) Y t ·sin(α p c β )+ ΔX p c β Y t ′ = X t ·sin(α p c β ) + Y t ·cos(α p c β ) + ΔY p c β θ t ′ = θ t + α p c β Obtain the target location coordinates (X) t ′, Y t ′, θ t The accurate position of the component in the machine coordinate system after compensating for PCB mounting errors. However, relative to the target position, the current position of the component also needs to consider the structural offset of the camera itself within the entire mounting system. This offset has been determined through calibration during the equipment assembly stage and is denoted as X. cam With Y cam Therefore, the physical coordinates (X and Y) of the components need to be... c ,Y c Adding this offset, we obtain its actual position coordinates (X, Y) in the machine coordinate system. cm , Y cm , θ cm ) = (X c + X cam , Y c + Y cam , θc By performing coordinate difference between the target mounting position and the actual position of the component, the three-dimensional positional deviation ΔX = X is calculated. t ′ X cm ΔY = Y t ′ Y cm Δθ = θ t ′ θ cm .

[0025] After calculating the component position deviation based on the target position coordinates and component position coordinates, the process further includes: mapping the component position coordinates through inverse transformation using PCB rotation deviation angle and PCB translation deviation to obtain the theoretical pixel coordinates of the component in the camera coordinate system; calculating the pixel deviation between the theoretical pixel coordinates and the pixel coordinates of the component center point; calculating the verification distance vector from the theoretical pixel coordinates to the center pixel coordinates of the four Mark reference points; comparing the verification distance vector with the first pixel distance, second pixel distance, third pixel distance, and fourth pixel distance calculated in step two; and recalculating the PCB rotation deviation angle and PCB translation deviation when the distance deviation exceeds the preset verification threshold.

[0026] In one specific embodiment, calculating the PCB rotational deviation angle and PCB translational deviation based on measured physical coordinates includes: Calculate the first ordinate difference and the first abscissa difference between the measured physical coordinates of the Mark reference point, and calculate the second ordinate difference and the second abscissa difference in the machine coordinate system; Calculate the PCB rotation deviation angle based on the difference between the first vertical coordinate, the difference between the first horizontal coordinate, the difference between the second vertical coordinate, and the difference between the second horizontal coordinate. Calculate the difference between the third ordinate and the third abscissa between the measured physical coordinates and the theoretical coordinates of the Mark reference point; Multiply the difference between the third vertical coordinate and the difference between the third horizontal coordinate by the cosine and sine of the PCB rotation deviation angle, respectively, to obtain the X-axis translation deviation. Multiply the difference between the third vertical coordinate and the difference between the third horizontal coordinate by the negative sine and cosine of the PCB rotation deviation angle, respectively, to obtain the Y-axis translation deviation. Generate the PCB translation deviation based on the X-axis and Y-axis translation deviations.

[0027] In this embodiment, the center pixel coordinates of four Mark reference points are extracted from the camera image and converted into measured physical coordinates in the camera coordinate system using a pixel scale factor. Mark points M1 and M2 form a key reference line for calculating the deviation. The longitudinal coordinate difference between M1 and M2 is defined as the first longitudinal coordinate difference. The corresponding horizontal coordinate difference is defined as the first horizontal coordinate difference value. This represents the direction vector of the connection line in the physical coordinate system of the measured image; simultaneously, based on the theoretical position coordinates of M1 and M2 in the machine coordinate system according to the PCB design parameters, the difference in the second ordinate is calculated. Difference from the second horizontal axis The theoretical direction vector is obtained. Based on the angle difference between the direction vectors, the angle between the two coordinate systems is calculated, which is the rotational deviation angle of the PCB relative to the ideal mounting direction. The formula for calculating the deviation angle is: The angle difference between the measured and theoretical directions is calculated using the arctangent function. After obtaining this angle, the difference in the third abscissa between the measured and theoretical coordinates of point M1 is calculated. Difference from the third ordinate .right and Perform coordinate transformations using the formula for two-dimensional rotation transformations, multiplying by... and Coefficient. In the calculation of X-axis translational deviation, the coefficient will be... Multiply ΔY3 multiplied by Adding the two together gives In the calculation of the Y-axis translational deviation, ΔX3 is multiplied by ΔY3 multiplied by Adding the two together gives ,Will and The combined vectors form the translational deviation vector of the current PCB, which describes the overall drift of the coordinate system caused by the rotation and positional offset of the PCB during actual installation.

[0028] After generating the PCB translation deviation based on the X-axis and Y-axis translation deviations, the process also includes: calculating the area of ​​the PCB region enclosed by the four Mark reference points; dividing the PCB region into four triangular sub-regions along the lines connecting the four Mark reference points; calculating the triangular sub-region where the target mounting point coordinates are located; calculating the weight coefficient of the target mounting point relative to the three vertex Mark reference points based on the centroid coordinates of the target mounting point in the triangular sub-region; multiplying the translation deviations of the three vertex Mark reference points by their corresponding weight coefficients and summing them to obtain the local translation correction amount for the target mounting point; and performing a second correction by superimposing the local translation correction amount on the target position coordinates to obtain the final target position coordinates considering the local deformation of the PCB.

[0029] In one specific embodiment, when the component position deviation exceeds the allowable deviation threshold, the additional displacement generated by the rotational action is calculated and the additional displacement is subtracted from the component position deviation to obtain the comprehensive compensation displacement, including: When the positional deviation of a component exceeds the allowable deviation threshold, the radial position vector after rotation is calculated by rotation transformation based on the radial position vector of the component center relative to the rotation axis and the rotation angle deviation. The difference between the radial position vectors before and after rotation is then calculated to obtain the additional displacement generated by the rotation action. The X-axis translational deviation of the component position deviation is subtracted from the X-axis component of the additional displacement to obtain the compensation displacement of the gantry X-axis. The Y-axis translational deviation is subtracted from the Y-axis component of the additional displacement to obtain the compensation displacement of the gantry Y-axis. The compensation displacement of the gantry X-axis and the compensation displacement of the gantry Y-axis are used as the comprehensive compensation displacement.

[0030] In this embodiment, it is determined whether the current deviations of the components in the X and Y directions and the rotation angle, ΔX, ΔY, and Δθ, exceed the allowable deviation threshold ΔX set in the system configuration. th ΔY th and Δθ th If any of these parameters exceeds the threshold, it indicates that the error between the current position and the target position is not negligible, and the alignment correction process needs to be initiated. During the alignment correction process, rotation compensation not only changes the angle of the component but also introduces additional translational displacement because its center point does not coincide with the rotation axis. At this point, a radial vector is constructed based on the initial position of the component's center point relative to the rotation center of the rotating head's spindle, denoted as r = (r... x ,r y The radial vector, determined by the nozzle structure and the orientation of components during the suction process, is a static vector. After the rotational action deviates by an angle Δθ, the radial vector rotates in space, and the transformed coordinates are obtained using the two-dimensional coordinate rotation transformation formula: The difference in position before and after rotation, i.e., the X and Y components of the additional displacement, is expressed as: Additional displacements (δx, δy) are natural displacements caused by the rotation of the rotating head around its own axis. If not compensated, these displacements will be directly superimposed on the gantry translation path, leading to overcompensation or inaccurate offset. To ensure that the final component center is aligned with the target pad center, these additional displacements are removed from the gantry XY axis translation compensation command. The net compensation displacement to be performed on the gantry X-axis is... The net compensation displacement that the gantry Y-axis should perform is ΔX and ΔY represent the actual error values ​​between the current and target positions of the component. These two compensation values ​​ΔX... final and final This constitutes a comprehensive compensation displacement, which instructs the X and Y axes of the gantry system to move to the ideal mounting position after eliminating deviations, while maintaining independent rotational compensation.

[0031] In one specific embodiment, a rotation command is sent to the rotary head servo motor based on the component position deviation, and a stepping pulse signal is sent to the gantry stepper motor based on the comprehensive compensation displacement. The rotary head and gantry perform compensation actions in parallel to complete the component alignment, including: Based on the rotation angle deviation in the component position deviation, a rotation command is sent to the rotary head servo motor. Divide the gantry X-axis compensation displacement in the comprehensive compensation displacement by the X-axis stepper motor step distance to obtain the X-axis step pulse count. Divide the gantry Y-axis compensation displacement in the comprehensive compensation displacement by the Y-axis stepper motor step distance to obtain the Y-axis step pulse count. Send the corresponding step pulse signals to the gantry X-axis and gantry Y-axis stepper motors. The rotary head servo motor and the gantry stepper motor perform rotation compensation and translation compensation actions in parallel, and calculate the maximum value of the rotation time and the translation time as the alignment correction time.

[0032] In this embodiment, based on the component rotation angle deviation Δθ, the control system generates a corresponding rotation compensation command and sends this angle value and the appropriate rotation speed parameter as command parameters to the servo motor controller configured on the rotating head. The rotation speed is controlled in stages based on the absolute value of the angle deviation. For example, when |Δθ| < 1°, low-speed rotation is used to prevent the component from slipping on the nozzle, while medium-high speed rotation is used when the angle deviation is large to shorten the rotation time. Specifically, three rotation speeds ω1, ω2, and ω3 are set, in degrees per second. After the rotation compensation action is initiated, the servo motor executes the angle adjustment with Δθ as the target according to the command and provides real-time position feedback in a closed loop. Simultaneously, the comprehensive compensation displacement ΔX is... final with ΔY final Perform step size conversion and read the step distance parameters S of the X-axis and Y-axis stepper motors of the gantry from the system configuration. x With S y The unit is mm / pulse, representing the actual translation distance corresponding to each pulse emitted. Let ΔX... final Divide by S x The number of step pulses required for the X-axis of the gantry: Similarly, the number of Y-axis step pulses is: The calculation result is rounded up to ensure accurate compensation and avoid minor residual deviations caused by rounding errors. The control system sends N to the stepper drivers of the X and Y axes respectively. x With N y A pulse signal is generated, and the pulse frequency is set according to the displacement to match the moving speed. For example, a lower frequency f1 is used when the compensation is small to ensure smoothness, while a higher frequency f2 is used when the displacement is large to improve response efficiency. The product of the pulse frequency and the step distance is the current moving speed of the motor. This corresponds to the movement speed along the X and Y axes. During the compensation execution phase, the rotary head servo motor and the gantry X and Y axis stepper motors are uniformly scheduled by the control system to synchronously initiate rotation and translation compensation operations in parallel. The two compensations overlap to the maximum extent in time, thereby shortening the overall placement cycle. To evaluate the time cost of the compensation process, the time T required for the rotation action is calculated separately. 旋转 = |Δθ| / ω i The time T required for translation movement 平移 = max(|ΔX final |, |ΔY final |) / v i , where v i The effective moving speed in the corresponding direction. The maximum of the two is taken as the total time T for the current component alignment correction. 对齐 .

[0033] After taking the compensation displacement of the X-axis and Y-axis of the gantry as the comprehensive compensation displacement, the process also includes: determining whether the absolute value of the rotation angle deviation in the component position deviation exceeds a preset large angle deviation threshold; if it exceeds the threshold, decomposing the rotation angle deviation into multiple segmented rotation angles; calculating the segmented additional displacement generated by each segmented rotation action according to the segmented rotation angles; summing the segmented additional displacements to obtain the total additional displacement; subtracting the total additional displacement from the translational deviation in the component position deviation to obtain the graded compensation displacement; sending multiple rotation commands to the rotary head servo motor according to the segmented rotation angles; and sending a staged compensation pulse signal to the gantry stepper motor according to the corresponding segmented additional displacement after each rotation is completed.

[0034] In one specific embodiment, the SMT placement quality control method further includes: Calculate the average of the minimum and maximum X-coordinates of the PCB in the machine coordinate system as the centerline position, and compare the X-coordinates of each component mounting position with the centerline position. Components with X-coordinates less than the centerline position are assigned to the first gantry, and components with X-coordinates greater than or equal to the centerline position are assigned to the second gantry. Calculate the moving distance of each component from the material position to the placement position, divide the fixed material suction time and moving distance by the maximum moving speed of the first gantry or the second gantry, the fixed placement time and the alignment correction time, and sum them up to obtain the estimated total operation time of the first gantry and the estimated total operation time of the second gantry. Calculate the difference in operating time between the estimated total operating time of the first gantry and the estimated total operating time of the second gantry; The alternating work cycle of the first and second gantry is set according to the difference in work time, and the cycle scheduling is implemented.

[0035] In this embodiment, the target position coordinate information of all components to be mounted in this batch is extracted from the PCB mounting process, including the distribution range of their X-axis coordinates in the PCB design coordinate system. These mounting point coordinates are then converted to absolute positions in the machine coordinate system. The X-axis coordinates of all mounting points are iterated and filtered, and the minimum and maximum values ​​are extracted, denoted as... and Calculate the average of the two values ​​as the PCB centerline position: The centerline represents the baseline for task allocation in the X direction of the gantry system, used to achieve spatial task separation between the two gantry systems. The mounting position coordinates of each component are determined individually. Is it less than the midline position? If satisfied If the condition is met, the component will be assigned to the first gantry (left gantry); otherwise, when... At that time, the components are assigned to the second gantry (right gantry), forming two component sets, each corresponding to a placement task queue to be executed by one of the two gantryes. The calculation of each component's position from its designated location is then performed. To the mounting position The spatial distance traveled is expressed as: Then divide the spatial movement distance by the maximum movement speed of the corresponding gantry. and with a fixed feeding time T 吸料 Fixed placement time T 贴装 And the previously recorded component alignment correction time T 对齐i The operation time of the component is calculated by summing the results. The operation time of all components belonging to the first gantry allocation set will be determined. Summing each term, we obtain the estimated total operation time for the first gantry. Similarly, calculate the total operation time for the second gantry task set. The difference between the two values ​​is the time difference for the gantry operation. This is used to assess whether the task allocation between the two ganks is balanced. If the difference significantly exceeds a threshold percentage, such as exceeding 15% of the total time, it indicates that tasks need to be reassigned; if it is within an acceptable range, it is based on the current... and Set the alternation cycle of the gantry. Define the cycle scheduling parameters to allocate the action execution windows of the two gantry in an alternating sequence, with the cycle length set as follows: During operation, the first and second gantry are scheduled to perform task sequences alternately according to the cycle. At any given time, only one gantry is in the placement stage, while the other gantry is in the material suction or positioning preparation stage. The dual-gantry collaboration is optimized through cycle mutual exclusion scheduling, effectively avoiding resource conflicts and job waiting.

[0036] In one specific embodiment, the alternating working cycle of the first gantry and the second gantry is set according to the difference in working time, and periodic scheduling is implemented, including: Based on the difference in operation time, select components whose X-axis coordinate distance from the centerline position is less than a preset distance threshold and whose alignment correction time is greater than the median. Calculate the difference change for transferring the component. When the difference change is negative, execute the transfer operation and update the gantry task set. Calculate the alternating working cycle of the gantry. The first gantry starts to perform placement at the initial moment, and the second gantry performs material preparation and suction simultaneously. When the first gantry completes placement, the second gantry starts placement and the first gantry suctions material simultaneously. The ratio of the number of completed components to the total allocated quantity of the first gantry is calculated as the completion progress ratio of the first gantry. At the same time, the completion progress ratio of the second gantry is calculated, and the progress ratio difference is calculated based on the completion progress ratio of the first gantry and the completion progress ratio of the second gantry. Based on the difference in progress percentage, the preset number of components with the shortest alignment and correction time are taken from the end of the remaining task queue of the gantry with the larger progress percentage and transferred to the gantry with the smaller progress percentage.

[0037] In this embodiment, based on the gantry operation time difference, the source gantry with a heavier workload and the target gantry with a lighter workload are identified. All component tasks assigned to the source gantry are iterated, and components meeting two conditions are selected: the absolute value of the X-axis coordinate distance of their mounting position from the centerline is less than a set spatial distance threshold (e.g., 20% of the PCB width), and their alignment correction time is higher than the median value of the current component set. These components, being close to the centerline, have lower spatial costs for cross-regional transfer and higher correction times, thus significantly impacting load balancing. These components are marked as candidate transfer units and sorted from highest to lowest alignment correction time. For each sorted candidate component, the change in operation time difference ΔT resulting from transferring it to the target gantry is evaluated.new That is, calculate the reduction in the total operation time T of the source gantry after the component is removed from the source gantry. k The time T added to the target gank k ′, where T k This includes the time for material suction, placement, calibration, and the time corresponding to the original path travel distance, T. k The new path travel time D caused by the different positions of the target gantry feeder needs to be considered. trans / V max If ΔT new = |T 1new T 2new If |<ΔT, it indicates that this transfer operation helps to reduce the load difference. The transfer operation is then executed, removing the component from the source gantry's task queue and adding it to the target gantry's task queue. The total operating time of both gantry queues is updated as a new baseline. This evaluation and transfer process is repeated until the load difference falls below a set percentage threshold or no more suitable components are available. After initial allocation and balancing optimization, the cycle scheduling phase begins, with the gantry alternation work cycle set as follows: A periodic execution control mechanism is activated, causing the first gantry to begin placing the first component at t=0. Simultaneously, the second gantry initiates a material preparation process in the background. After the first gantry completes its placement, execution switches to the second gantry, and the first gantry prepares for the next component. This achieves alternating placement and suction by both gantry, maintaining a continuous and smooth system cycle. The progress of each gantry is tracked in real-time. Let the number of components completed by the first gantry be 'completed1', and the total number of tasks be 'total1'. Then, the completion percentage is: Similarly, the completion progress percentage of the second gantry is: The difference in the progress ratio between the two is ΔP = |P1 P2|, if ΔP exceeds the set threshold (e.g., 20%), it is determined that there is an imbalance in the work progress. At this time, a preset number of n components with the shortest alignment and correction time will be selected from the end of the remaining task queue of the gantry with faster completion progress, and transferred to the task queue of the gantry with slower progress in turn. With the help of low-load tasks, the tasks on the slower gantry can be quickly digested, thereby dynamically catching up with the task progress of the two, continuously maintaining the symmetry and real-time performance of the alternating rhythm, and achieving the optimal coordination of the dual gantry system in both time and rhythm dimensions.

[0038] Before setting the alternating work cycle of the first and second gantry based on the difference in work time and implementing cycle scheduling, the process also includes: calculating the percentage of components in the component set allocated to the first gantry whose alignment correction time exceeds a preset time threshold, calculating the percentage of components in the component set allocated to the second gantry whose alignment correction time exceeds a preset time threshold, and calculating the difference in the percentage of high-time-consuming components between the two gantry; when the difference in the percentage of high-time-consuming components exceeds a preset percentage threshold, setting a reduced movement speed coefficient for the gantry with a higher percentage of high-time-consuming components and setting an increased movement speed coefficient for the gantry with a lower percentage of high-time-consuming components, compensating for the difference in alignment correction time through speed differences; recalculating the estimated total work time of the first and second gantry based on the movement speed coefficients, and updating the difference in work time.

[0039] Before calculating the average of the minimum and maximum X-coordinates of the PCB in the machine coordinate system as the centerline position, the process includes: calculating the moving distance based on the placement coordinates and material position coordinates of each component; querying the average alignment correction time of similar components from the historical alignment correction database based on the component type and size specifications to obtain the predicted alignment correction time for each component; dividing the moving distance of each component by the maximum gantry speed and adding the fixed material feeding time, fixed placement time, and predicted alignment correction time to calculate the single-piece operation time of each component; summing the single-piece operation times of all components to obtain the total operation time; iteratively adjusting the X-coordinate value of the centerline position with the goal of minimizing the difference between the expected total operation times of the two gantry units; and using the X-coordinate value of the centerline position as the minimum difference between the cumulative single-piece operation time of the components on the left and right sides of the centerline position as the optimized centerline position.

[0040] In one specific embodiment, the ratio of the number of completed components to the total allocated quantity of the first gantry is calculated as the completion progress ratio of the first gantry. Simultaneously, the completion progress ratio of the second gantry is calculated, and the progress ratio difference is calculated based on the completion progress ratios of the first and second gantry, including: The completion progress percentage of the first gantry is obtained by dividing the number of components that have been mounted on the first gantry by the total number of components allocated to the first gantry. Similarly, the completion progress percentage of the second gantry is obtained by dividing the number of components that have been mounted on the second gantry by the total number of components allocated to the second gantry. Calculate the difference in progress percentage between the first gantry and the second gantry.

[0041] In this embodiment, during the placement process, whenever the first gantry completes a component placement action and confirms the placement completion signal, the control system increments the completion count for the first gantry. Simultaneously, when the second gantry completes a placement action, the completion count for the second gantry is incremented. Throughout the entire placement cycle, the current number of completed components for both gantry is continuously obtained. At any given scheduling evaluation moment, the control system reads the number of completed components for the first gantry and the total number of components allocated to the first gantry, and calculates the ratio to obtain the completion progress ratio for the first gantry. Similarly, it reads the number of completed components for the second gantry and the total number of components allocated to the second gantry, and calculates the ratio to obtain the completion progress ratio for the second gantry. Both completion progress ratios characterize the proportion of placement tasks completed by each gantry at the current moment relative to its total tasks. As the placement process progresses, this ratio gradually changes from zero to one. The difference between the completion progress ratios of the first and second gantry is calculated, and the absolute value of the difference is taken as the progress ratio difference, which quantifies the synchronization of the two gantry placement rhythms. When the progress ratio difference is within a preset allowable range, it indicates that the placement progress of the first and second gantry is basically consistent, and the alternating execution of the two gantry is in a stable and coordinated state. However, when the progress ratio difference exceeds a preset threshold, it indicates that the placement progress of one gantry is significantly faster than that of the other gantry. Based on this, a dynamic task adjustment and load balancing strategy is triggered to bring the completion progress ratios of the two gantry closer together, ensuring the coordination and continuity of the dual-gantry placement operation in the time dimension, and avoiding premature idleness or long waiting times for one gantry.

[0042] The SMT placement quality control method in the embodiments of the present invention has been described above. The SMT placement quality control system in the embodiments of the present invention is described below. Please refer to [link / reference]. Figure 2 One embodiment of the SMT placement quality control system of the present invention includes: The deviation calculation module is used to calculate the PCB rotation deviation angle and PCB translation deviation, and to superimpose the PCB rotation deviation angle and PCB translation deviation on the target mounting point coordinates to obtain the component position deviation. The comprehensive compensation module is used to calculate the additional displacement generated by the rotational motion and subtract the additional displacement from the component position deviation to obtain the comprehensive compensation displacement when the component position deviation exceeds the allowable deviation threshold. The execution module is used to send rotation commands to the rotary head servo motor based on the component position deviation and to send stepping pulse signals to the gantry stepper motor based on the comprehensive compensation displacement. The rotary head and gantry perform compensation actions in parallel to complete the component alignment.

[0043] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0044] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0045] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for SMT (Surface Mount Technology) assembly quality control, characterized in that, include: Calculate the PCB rotation deviation angle and the PCB translation deviation, and superimpose the PCB rotation deviation angle and the PCB translation deviation onto the target mounting point coordinates to obtain the component position deviation. When the position deviation of the component exceeds the allowable deviation threshold, the additional displacement generated by the rotation action is calculated and the additional displacement is subtracted from the position deviation of the component to obtain the comprehensive compensation displacement. The rotating head servo motor is sent a rotation command based on the component position deviation, and the gantry stepper motor is sent a stepping pulse signal based on the comprehensive compensation displacement. The rotating head and gantry perform compensation actions in parallel to complete the component alignment.

2. The SMT placement quality control method according to claim 1, characterized in that, Before calculating the PCB rotational deviation angle and PCB translational deviation, the following is also included: The center pixel coordinates of four Mark reference points in the PCB are extracted from the image acquired by the fixed camera, and edge detection is performed on the components in the image to obtain the pixel coordinates of the center points of the components. Calculate the first pixel distance, second pixel distance, third pixel distance, and fourth pixel distance between the pixel coordinates of the center point of the component and the center pixel coordinates of the four Mark reference points, respectively.

3. The SMT placement quality control method according to claim 2, characterized in that, Calculate the PCB rotation deviation angle and PCB translation deviation, and superimpose the PCB rotation deviation angle and PCB translation deviation onto the target mounting point coordinates to obtain the component position deviation, including: Multiply the center pixel coordinates of the four Mark reference points and the pixel coordinates of the component center point by the camera's pixel scale factor to obtain the measured physical coordinates of the four Mark reference points and the physical coordinates of the component center point. Calculate the PCB rotation deviation angle and PCB translation deviation based on the measured physical coordinates; The target position coordinates are obtained by superimposing the PCB rotation deviation angle and the PCB translation deviation on the target mounting point coordinates. The component position coordinates are obtained by superimposing the physical coordinates of the component center point on the camera offset in the machine coordinate system. The component position deviation is calculated based on the target position coordinates and the component position coordinates.

4. The SMT placement quality control method according to claim 3, characterized in that, The PCB rotational deviation angle and PCB translational deviation are calculated based on the measured physical coordinates, including: Calculate the first ordinate difference and the first abscissa difference between the measured physical coordinates of the Mark reference point, and calculate the second ordinate difference and the second abscissa difference in the machine coordinate system; Calculate the PCB rotation deviation angle based on the first vertical coordinate difference, the first horizontal coordinate difference, the second vertical coordinate difference, and the second horizontal coordinate difference; Calculate the difference between the third ordinate and the third abscissa between the measured physical coordinates and the theoretical coordinates of the Mark reference point; Multiply the difference between the third vertical coordinate and the difference between the third horizontal coordinate by the cosine and sine of the PCB rotation deviation angle, respectively, to obtain the X-axis translation deviation. Multiply the difference between the third vertical coordinate and the difference between the third horizontal coordinate by the negative sine and cosine of the PCB rotation deviation angle, respectively, to obtain the Y-axis translation deviation. Generate the PCB translation deviation based on the X-axis translation deviation and the Y-axis translation deviation.

5. The SMT placement quality control method according to claim 1, characterized in that, When the positional deviation of the component exceeds the allowable deviation threshold, the additional displacement generated by the rotational motion is calculated, and the additional displacement is subtracted from the positional deviation of the component to obtain a comprehensive compensation displacement, including: When the position deviation of the component exceeds the allowable deviation threshold, the radial position vector after rotation is calculated by rotation transformation based on the radial position vector of the component center relative to the rotation axis and the rotation angle deviation, and the difference between the radial position vectors before and after rotation is calculated to obtain the additional displacement generated by the rotation action. The X-axis translational deviation of the component position deviation is subtracted from the X-axis component of the additional displacement to obtain the compensation displacement of the gantry X-axis. The Y-axis translational deviation is subtracted from the Y-axis component of the additional displacement to obtain the compensation displacement of the gantry Y-axis. The compensation displacement of the X-axis of the gantry and the compensation displacement of the Y-axis of the gantry are taken as the comprehensive compensation displacement.

6. The SMT placement quality control method according to claim 1, characterized in that, Based on the component position deviation, a rotation command is sent to the rotary head servo motor, and based on the comprehensive compensation displacement, a stepping pulse signal is sent to the gantry stepper motor. The rotary head and gantry perform compensation actions in parallel to complete component alignment, including: Based on the rotation angle deviation in the component position deviation, a rotation command is sent to the rotary head servo motor. Divide the compensation displacement of the gantry X-axis in the comprehensive compensation displacement by the step distance of the X-axis stepper motor to obtain the X-axis step pulse count. Divide the compensation displacement of the gantry Y-axis in the comprehensive compensation displacement by the step distance of the Y-axis stepper motor to obtain the Y-axis step pulse count. Send the corresponding step pulse signals to the gantry X-axis and gantry Y-axis stepper motors. The rotary head servo motor and the gantry stepper motor perform rotation compensation and translation compensation actions in parallel, and calculate the maximum value of the rotation time and the translation time as the alignment correction time.

7. The SMT placement quality control method according to claim 6, characterized in that, The SMT placement quality control method further includes: The average of the minimum and maximum X-coordinates of the PCB in the machine coordinate system is calculated as the centerline position, and the X-coordinates of the component mounting positions are compared with the centerline position. Components with X-coordinates less than the centerline position are assigned to the first gantry, and components with X-coordinates greater than or equal to the centerline position are assigned to the second gantry. Calculate the moving distance of each component from the material position to the placement position, divide the fixed material suction time and the moving distance by the maximum moving speed of the first gantry or the second gantry, the fixed placement time and the alignment correction time, and sum them up to obtain the estimated total operation time of the first gantry and the estimated total operation time of the second gantry. Calculate the difference in operating time between the estimated total operating time of the first gantry and the estimated total operating time of the second gantry; The alternating work cycle of the first gantry and the second gantry is set according to the difference in the work time, and the cycle scheduling is implemented.

8. The SMT placement quality control method according to claim 7, characterized in that, Based on the time difference of the operations, the alternating working cycle of the first gantry and the second gantry is set and the cycle scheduling is implemented, including: Based on the difference in the operation time, select components whose X-axis coordinate distance from the centerline position is less than a preset distance threshold and whose alignment correction time is greater than the median. Calculate the difference change amount for transferring the component. When the difference change amount is negative, perform the transfer operation and update the gantry task set. Calculate the alternating working cycle of the gantry. The first gantry starts to perform placement at the initial moment, and the second gantry performs material preparation and suction simultaneously. When the first gantry completes placement, the second gantry starts placement and the first gantry suctions material simultaneously. The ratio of the number of completed components to the total allocated quantity of the first gantry is calculated as the completion progress ratio of the first gantry. At the same time, the completion progress ratio of the second gantry is calculated, and the progress ratio difference is calculated based on the completion progress ratio of the first gantry and the completion progress ratio of the second gantry. Based on the progress ratio difference, a preset number of components with the shortest alignment and correction time are taken from the end of the remaining task queue of the gantry with a large completion progress ratio and transferred to the gantry with a small completion progress ratio.

9. The SMT placement quality control method according to claim 8, characterized in that, The ratio of the number of completed components to the total allocated quantity is calculated as the completion progress ratio of the first gantry. Simultaneously, the completion progress ratio of the second gantry is calculated, and the progress ratio difference is calculated based on the completion progress ratios of the first and second gantry, including: The completion progress percentage of the first gantry is obtained by dividing the number of components that have been mounted on the first gantry by the total number of components allocated to the first gantry. Similarly, the completion progress percentage of the second gantry is obtained by dividing the number of components that have been mounted on the second gantry by the total number of components allocated to the second gantry. Calculate the difference between the progress percentages of the first gantry and the second gantry.

10. An SMT (Surface Mount Technology) placement quality control system, characterized in that, A method for performing SMT placement quality control as described in any one of claims 1-9, comprising: The deviation calculation module is used to calculate the PCB rotation deviation angle and the PCB translation deviation, and to superimpose the PCB rotation deviation angle and the PCB translation deviation on the target mounting point coordinates to obtain the component position deviation. The comprehensive compensation module is used to calculate the additional displacement generated by the rotation action and subtract the additional displacement from the component position deviation when the component position deviation exceeds the allowable deviation threshold, so as to obtain the comprehensive compensation displacement. The execution module is used to send rotation commands to the rotary head servo motor according to the component position deviation, and send stepping pulse signals to the gantry stepper motor according to the comprehensive compensation displacement. The rotary head and gantry perform compensation actions in parallel to complete the component alignment.

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