Optimization method for printing height of special-shaped medium based on multi-point height measurement and edge compensation

Abstract

This invention relates to a method for optimizing the printing height of irregularly shaped media based on multi-point height measurement and edge compensation. The method involves obtaining the boundary position of the irregularly shaped media on the printing platform; setting multiple height measurement points located outside, at, and inside the boundary along the direction traversing the boundary position; and measuring the height in the order of outside, boundary, and inside height measurement points to obtain the outside height value, boundary height value, and inside height value; determining whether the boundary height value is a valid height measurement value based on the relationship between the outside, boundary, and inside height values; determining the edge compensation basis based on the valid height measurement value; and determining the printhead gap height corresponding to the printing area of ​​the irregularly shaped media based on the edge compensation basis. This invention can simultaneously reflect the height changes of the platform area, the edge transition area, and the media body area, providing a more complete and reliable data foundation for printhead gap setting.

Description

Technical Field

[0001] This invention relates to a method for optimizing the printing height of irregularly shaped media, specifically a method for optimizing the printing height of irregularly shaped media based on multi-point height measurement and edge compensation. Background Technology

[0002] Inkjet printing is a non-contact imaging method. The jet gap between the printhead and the substrate directly affects the droplet trajectory, landing accuracy, and final image quality. For irregularly shaped media such as glass, metal, ceramics, leather, packaging, and decorative parts, the printing surface is often not a regular plane. Especially at the edges of the media, there are often steps, chamfers, local curved surfaces, edge warping, or abrupt changes in thickness, causing significant changes in the relative height between the printhead and the media surface in the edge area. In recent years, the publicly available patent CN118269355A has pointed out that traditional inkjet printing technology is mainly suitable for flat objects, and printing on objects with high drops or irregular shapes poses a significant challenge. Existing methods for adapting to high-drop printing often increase the printhead operating voltage to increase the droplet drop speed, but this method increases the amplitude of the piezoelectric ceramic inside the printhead, which is detrimental to the printhead's lifespan. At the same time, the patent document also states that the suitable printing height for common printheads is generally within a small range. As the height increases, the droplets are affected by air resistance, resulting in a decrease in speed and easy dispersion, which in turn leads to uneven printing. Therefore, in applications involving irregularly shaped media, especially those with significant edge height differences, balancing printhead safety and print quality has become a technical problem that needs to be continuously addressed in the inkjet printing field.

[0003] On the other hand, existing technologies have proposed several compensation schemes based on height measurement information to address height errors during the printing process. For example, CN115742313A discloses a 3D printing quality compensation method and system based on height information. This method acquires height information through a non-contact height measurement component located on one side of the print head, measures the actual height value after each layer is printed, compares it with the ideal height value, and corrects the printing flow rate for the next layer to improve problems such as over-extrusion, under-extrusion, and insufficient interlayer adhesion caused by layer height errors. This type of scheme demonstrates that using non-contact height measurement components in print control can improve printing accuracy to a certain extent and avoid interference caused by contact detection. However, this technology mainly focuses on layer height control, overall height compensation, or forming process correction. Its measurement objects are more focused on the printed layers or the entire plane to be processed, and it does not specifically address the reliability of edge height measurement when transitioning from the platform to the medium body at the boundary of irregularly shaped media. For flatbed inkjet printers, when the height measurement path crosses the media boundary, the measured values ​​often contain a mixture of the height outside the platform, the edge transition height, and the actual height inside the media. Without a determination of the validity of the boundary height measurement values, it is difficult to use the measured results directly and stably for printhead gap setting.

[0004] Furthermore, CN118269355A also reveals the non-uniformity problem in printing on irregularly shaped surfaces from another perspective. Due to the curvature, bending, and unevenness of the printed surface, the amount of ink droplets received per unit area varies in different regions, easily leading to uneven printing thickness and decreased surface quality. Although this document calculates printing parameters using the ratio of surface area to projected area to achieve more uniform printing on surfaces with high elevation differences, its technical focus is on adjusting ink volume or grayscale parameters based on the geometric relationship of the irregular surfaces, rather than optimizing the cross-boundary height measurement and printhead safety gap for the actual placement boundary of the irregular media on the printing platform. In actual production, irregularly shaped media not only exhibit surface variations but also often involve random placement, irregular edges, local warping, rounded or chamfered edges, etc., causing the single-point height measurement value at the boundary to be easily distorted. If the distorted boundary height is directly used as the basis for printhead height adjustment, it can result in excessive printhead gap, ink droplet diffusion, and blurry edge imaging; in severe cases, it may cause the printhead to rub against the media edge, affecting the stability of continuous printing. Therefore, existing technologies still need to provide a height optimization method suitable for printing on irregular media. This method should first determine the location of the media boundary, then perform multi-point height measurement along the direction of crossing the boundary, and determine the validity of the height values ​​measured at the boundary. Based on this, a more reliable edge compensation basis can be formed to determine the nozzle gap height corresponding to the printing area. Summary of the Invention

[0005] The purpose of this invention is to provide a method for optimizing the printing height of irregular media based on multi-point height measurement and edge compensation, thereby solving some of the drawbacks and shortcomings pointed out in the background art.

[0006] The technical solutions adopted by the present invention to solve the above-mentioned technical problems include:

[0007] Obtain the boundary position of the irregularly shaped medium on the printing platform;

[0008] Multiple elevation measurement points are set up along the direction of crossing the boundary, located outside the boundary, at the boundary, and inside the boundary. The elevation is measured in the order of the outer elevation measurement point, the boundary elevation measurement point, and the inner elevation measurement point to obtain the outer elevation value, the boundary elevation value, and the inner elevation value.

[0009] Based on the relationship between the outer height value, the boundary height value, and the inner height value, determine whether the boundary height value is a valid height measurement value; determine the edge compensation basis based on the valid height measurement value, and determine the nozzle gap height corresponding to the irregular media printing area based on the edge compensation basis.

[0010] Furthermore, along the height measurement path that crosses the boundary position, the height is measured sequentially in the direction from the outside of the boundary to the inside of the boundary and in the direction from the inside of the boundary to the outside of the boundary, respectively, to determine the first position and the second position where the change in height value between the two measurements exceeds a preset threshold, and the boundary position is determined based on the first position and the second position.

[0011] Furthermore, for two sets of height measurement points arranged adjacent to each other along the boundary extension direction, the difference between the outer height value and the boundary height value is calculated to form a first difference value, and the difference between the inner height value and the boundary height value is calculated to form a second difference value. When the first difference value in both sets of height measurement points is greater than the second difference value, or when both are less than the second difference value, the boundary height value is determined to be a valid height measurement value. When the magnitudes of the first difference value and the second difference value in the two sets of height measurement points are inconsistent, the boundary height value is determined to be an invalid height measurement value.

[0012] Further, a first effective height measurement value and a second effective height measurement value are determined along the direction from the outside of the boundary to the inside of the boundary and along the direction from the inside of the boundary to the outside of the boundary, respectively; the first effective height measurement value and the second effective height measurement value are compared, and the effective height measurement value with the larger value is determined as the edge compensation basis, and the nozzle gap height is determined according to the edge compensation basis.

[0013] Furthermore, during the height measurement process from the outside of the boundary to the inside of the boundary, the first of three consecutive height measurement points where the height difference between adjacent height measurement points exceeds the preset threshold twice is determined as the first position; during the height measurement process from the inside of the boundary to the outside of the boundary, the first of three consecutive height measurement points where the height difference between adjacent height measurement points exceeds the preset threshold twice is determined as the second position.

[0014] Furthermore, the preset threshold is determined based on the outer reference height and the inner reference height on the same altimetry path; wherein, the outer reference height is the average height of two adjacent altimetry points outside the boundary, the inner reference height is the average height of two adjacent altimetry points inside the boundary, and the preset threshold is a preset ratio of the difference between the outer reference height and the inner reference height.

[0015] Furthermore, when the distance between the first position and the second position is greater than the preset boundary width threshold, the height is measured again between the first position and the second position at a distance less than the initial height measurement point distance, and the boundary position is updated according to the position where the height value changes more than the preset threshold during the second measurement.

[0016] Further, multiple boundary height values ​​are obtained along the direction from the outer side of the boundary to the inner side of the boundary in a first direction, and the maximum value among the boundary height values ​​that continuously satisfy a preset size relationship is determined as the first effective height measurement value; multiple boundary height values ​​are obtained along the direction from the inner side of the boundary to the outer side of the boundary in a second direction, and the maximum value among the boundary height values ​​that continuously satisfy the preset size relationship is determined as the second effective height measurement value.

[0017] Further, the difference between the first effective height measurement value and the second effective height measurement value is calculated; when the difference is less than or equal to a preset difference threshold, the sum of the edge compensation basis and the preset safety gap is determined as the nozzle gap height; when the difference is greater than the preset difference threshold, the sum of the edge compensation basis, the preset safety gap, and the additional gap determined according to the difference is determined as the nozzle gap height.

[0018] Further, the ratio of the difference to the preset difference threshold is calculated; the corresponding additional gap level is determined according to the preset interval in which the ratio is located; and the preset gap increment corresponding to the additional gap level is determined as the additional gap.

[0019] This invention first obtains the boundary position of the irregularly shaped medium on the printing platform, and then sequentially sets multiple height measurement points on the outer side, the boundary itself, and the inner side of the boundary along the points where the medium crosses the boundary, forming a multi-point height measurement mechanism across the boundary. Compared to adjusting the nozzle height based solely on a single-point height measurement result, this method can simultaneously reflect the height changes of the platform area, the edge transition area, and the medium body area, providing a more complete and reliable data basis for setting the nozzle gap.

[0020] This invention further determines whether the boundary height value is a valid measurement value based on the relationship between the outer height value, the boundary height value, and the inner height value, and determines the edge compensation basis based on the valid measurement value, thereby determining the printhead gap height corresponding to the printing area of ​​irregularly shaped media. This can reduce printhead rubbing or excessive gap caused by edge misjudgment, ensuring printing safety while improving printing clarity, imaging consistency, and equipment operation stability in the edge area of ​​irregularly shaped media. Attached Figure Description

[0021] Figure 1 This is a flowchart of the edge height measurement of irregular media and nozzle gap control of the present invention.

[0022] Figure 2 This is a diagram showing the relationship between the outer reference height, the inner reference height, the height difference between the inner and outer sides, and the preset threshold in Embodiment 1.

[0023] Figure 3This is the initial bidirectional height measurement sequence and the preliminary boundary judgment diagram corresponding to the first and second positions in this embodiment 1.

[0024] Figure 4 This is a diagram showing the convergence of the boundary interval and the determination of the final boundary position after the 0.25mm encrypted retest in Example 1.

[0025] Figure 5 This is a schematic diagram of the height change and outlier identification of adjacent altimeter groups in the first direction in Embodiment 2.

[0026] Figure 6 This is a schematic diagram of the comparison between the first and second differences in both directions and the determination of the effective sequence in Embodiment 2.

[0027] Figure 7 This is a schematic diagram illustrating the determination of edge compensation based on the nozzle gap height in Embodiment 2. Detailed Implementation

[0028] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0029] Combined with appendix Figure 1 As shown, in this embodiment, to improve the accuracy of height measurement in the edge region of irregularly shaped media and further ensure the stability of the gap between the printhead and the media during printing, multiple height measurement points are set along the direction of crossing the boundary. These multiple height measurement points include at least an outer height measurement point located outside the boundary, a boundary height measurement point located at the boundary, and an inner height measurement point located inside the boundary. During height measurement, the outer height measurement point, the boundary height measurement point, and the inner height measurement point are measured sequentially from the outside in, thereby obtaining the outer height value, the boundary height value, and the inner height value, respectively. Through this point layout and measurement method, height change information on both sides of the boundary and the boundary region can be obtained simultaneously along the same height measurement path, facilitating the identification of abnormal measurement results caused by media edge undulations, abnormal reflections, or instantaneous detection deviations in the boundary region.

[0030] Furthermore, after obtaining the outer, boundary, and inner height values, the magnitude patterns among these three values ​​are compared to determine whether the boundary height value accurately reflects the height status at the edge of the irregularly shaped medium. When the boundary height value satisfies a preset magnitude pattern with both the outer and inner height values, it is determined to be a valid height measurement; otherwise, it is deemed an invalid height measurement. This preset magnitude pattern refers to the boundary height value matching the height variation trends of the outer and inner sides of the boundary, reflecting the actual transition relationship of the medium's edge region. Using this method, abnormal boundary measurement data can be effectively eliminated, improving the reliability of subsequent height compensation.

[0031] After determining the boundary height as an effective height measurement value, this effective height measurement value is used as the basis for edge compensation, or multiple effective height measurement values ​​are combined to determine the edge compensation basis. The edge compensation basis is used to characterize the height reference value that needs to be considered in the edge area of ​​irregularly shaped media during printing. Based on this edge compensation basis, the nozzle gap height corresponding to the printing area of ​​irregularly shaped media can be further calculated. Specifically, a preset safety gap is added to the edge compensation basis so that the nozzle can avoid rubbing against the media when passing through the edge area of ​​irregularly shaped media, while maintaining a suitable printing distance, thereby improving printing clarity and operational stability. Through the above implementation method, effective height measurement, outlier identification, and nozzle gap optimization control of the edge area of ​​irregularly shaped media are achieved, which is suitable for printing media with irregular edge shapes, significant thickness variations, or complex edge transitions.

[0032] In this embodiment, to more accurately determine the boundary position of the irregularly shaped medium, bidirectional height measurement is performed along the height measurement path crossing the boundary position. Specifically, firstly, multiple height measurement points are measured sequentially from the outside of the boundary to the inside of the boundary, and the height value change corresponding to each height measurement point is recorded; then, the height measurement is performed in reverse from the inside of the boundary to the outside of the boundary at the same height measurement points. By analyzing the two height measurement results, the first position and the second position where the height value change exceeds a preset threshold can be determined respectively, and the first position and the second position are used as the reference basis for boundary determination, thereby determining the boundary position.

[0033] Furthermore, during the elevation measurement process from the outside to the inside of the boundary, the height differences between adjacent elevation measurement points are compared sequentially according to the measurement order. When the height difference between adjacent elevation measurement points exceeds a preset threshold twice consecutively for the first time, the first elevation measurement point among the corresponding three consecutive elevation measurement points is determined as the first position. That is, when the height difference between a certain elevation measurement point and the next elevation measurement point exceeds the preset threshold, and the height difference between the next elevation measurement point and the one after that also exceeds the preset threshold, it can be considered that the elevation measurement path enters the boundary abrupt change region at that point, and the first elevation measurement point among the three consecutive elevation measurement points is designated as the first position. Correspondingly, during the elevation measurement process from the inside to the outside of the boundary, the height differences between adjacent elevation measurement points are compared sequentially in the reverse elevation measurement order. When the height difference between adjacent elevation measurement points exceeds a preset threshold twice consecutively for the first time, the first elevation measurement point among the corresponding three consecutive elevation measurement points is determined as the second position.

[0034] In this embodiment, the preset threshold is not fixed, but adaptively determined based on the outer and inner reference heights along the same elevation measurement path. The outer reference height can be taken as the average height of two adjacent elevation measurement points outside the boundary, and the inner reference height can be taken as the average height of two adjacent elevation measurement points inside the boundary. After obtaining the outer and inner reference heights, the height difference between them is calculated, and a preset ratio of this height difference is determined as the preset threshold. Since the thickness, edge shape, and placement of different irregularly shaped media may vary, using the above-described proportional setting method based on the height difference between the inner and outer reference heights allows the preset threshold to be adjusted according to the height characteristics of the actual measured object, thereby balancing boundary recognition sensitivity and anti-interference capability.

[0035] Furthermore, when the distance between the first and second positions determined by bidirectional elevation measurement is greater than a preset boundary width threshold, it can be considered that the current boundary recognition result has a boundary region that is too wide or the positioning is not precise enough. In this case, elevation measurement is performed again between the first and second positions at a distance smaller than the initial elevation measurement point distance to increase the sampling density in this interval. After the re-elevation measurement is completed, the height changes of each elevation measurement point in the re-measurement area are re-analyzed, and the boundary positions are updated based on the positions where the height value changes exceed the preset threshold.

[0036] For each set of elevation measurement points, the corresponding outer elevation value, boundary elevation value, and inner elevation value are obtained. The difference between the outer elevation value and the boundary elevation value is calculated as the first difference, and the difference between the inner elevation value and the boundary elevation value is calculated as the second difference. By comparing the magnitude of the first difference and the second difference in adjacent sets of elevation measurement points, it can be determined whether the current boundary elevation value can accurately reflect the elevation status of the boundary area.

[0037] Furthermore, when the first difference in both sets of adjacent altimeters is greater than the second difference, it indicates that the relationship between the boundary height value and the outer and inner height values ​​remains consistent in adjacent positions, and the height transition in the boundary area is continuous. In this case, the corresponding boundary height value can be determined as a valid altimeter value. When the first difference in both sets of adjacent altimeters is less than the second difference, it also indicates that the trend of the boundary height value is consistent in adjacent positions, and the corresponding boundary height value can also be determined as a valid altimeter value. Conversely, when one set of altimeters shows that the first difference is greater than the second difference, while the other set shows that the first difference is less than the second difference, it indicates that the height relationship between the two sets of altimeters is inconsistent, and the change in the boundary height value lacks stable continuity. There may be abnormal measurements, edge interference, or local misjudgment. Therefore, this boundary height value is determined as an invalid altimeter value.

[0038] In this embodiment, to make the selection of edge compensation criteria more robust and to ensure that the nozzle gap height can adapt to the actual height changes in the edge region of the irregularly shaped medium, the height measurement results of the boundary region can be screened and determined along both the direction from the outer edge to the inner edge and the direction from the inner edge to the outer edge. Specifically, multiple boundary height values ​​are obtained along the direction from the outer edge to the inner edge, and each boundary height value is continuously judged to meet a preset size relationship. Among the boundary height values ​​that continuously meet the preset size relationship, the boundary height value with the largest value is selected as the first effective height measurement value. Multiple boundary height values ​​are obtained along the direction from the inner edge to the outer edge, and the boundary height values ​​in the second direction are screened in the same way. Among the boundary height values ​​that continuously meet the preset size relationship, the boundary height value with the largest value is selected as the second effective height measurement value. By extracting effective height measurement values ​​in both directions, the possibility of a single measurement direction being affected by local edge morphology, measurement order, and occasional errors can be reduced, thereby improving the reliability of the height representation of the edge region.

[0039] After obtaining the first and second effective height measurements, they are compared, and the larger effective height measurement is determined as the edge compensation criterion. Using the larger value as the edge compensation criterion prioritizes safety avoidance requirements when the nozzle passes through the edge area of ​​irregularly shaped media, preventing interference between the nozzle and the media due to local protrusions or fluctuations in edge height. Based on this, the nozzle clearance height is further determined according to the edge compensation criterion. Specifically, the difference between the first and second effective height measurements is first calculated and compared with a preset difference threshold. When the difference is less than or equal to the preset difference threshold, it indicates that the effective height results measured in both directions are relatively close, and the height change in the boundary area is relatively stable. In this case, the sum of the edge compensation criterion and the preset safety clearance can be determined as the nozzle clearance height. When the difference is greater than the preset difference threshold, it indicates that there is a significant difference between the effective height results measured in both directions. There may be large undulations, local warping, or uneven edge transition in the boundary area. In this case, based on the edge compensation basis and the preset safety gap, an additional gap determined by the difference needs to be introduced. The sum of the edge compensation basis, the preset safety gap, and the additional gap is determined as the nozzle gap height to improve the safety margin during the printing process.

[0040] Furthermore, to better adapt the additional gap setting to varying degrees of boundary fluctuations, the ratio between the difference and a preset difference threshold can be calculated, and the corresponding additional gap level can be determined based on the preset range in which this ratio falls. Different additional gap levels correspond to different preset gap increments, and the preset gap increment corresponding to the current additional gap level is determined as the additional gap. In other words, when the ratio is in a lower range, it indicates that although there is a difference in the effective height measurements in both directions, the difference is small, corresponding to a lower level of additional gap; when the ratio is in a higher range, it indicates a stronger inconsistency in the height of the boundary area, corresponding to a higher level of additional gap. Through this graded determination method, the printhead gap height can be dynamically adjusted according to the actual height fluctuation of the boundary area, ensuring printing safety while also considering printing accuracy and imaging quality.

[0041] Example 1:

[0042] This embodiment relates to a method for optimizing the printing height of irregularly shaped media based on multi-point height measurement and edge compensation. The irregularly shaped media is placed on the surface of the printing platform, and the printhead assembly is equipped with a non-contact height sensor. The height sensor moves along a height measurement path that traverses the boundary of the irregularly shaped media. The height measurement path sequentially passes through the outer boundary region, the boundary region, and the inner boundary region to obtain height abrupt change information at the edge of the irregularly shaped media, and determines the boundary position accordingly.

[0043] In this embodiment, the edge segment to be measured is first determined based on the contour of the irregularly shaped medium on the printing platform, and then a height measurement path intersecting with this edge segment is selected. Multiple height measurement points are sequentially arranged along the direction from the outer side of the boundary to the inner side, according to a preset initial height measurement point spacing of 1.0 mm. The height sensor continuously collects height values ​​starting from the exposed area of ​​the printing platform until it enters the printing surface area of ​​the irregularly shaped medium, obtaining a forward height measurement sequence. After completing the forward height measurement, the height is measured again along the same path from the inner side of the boundary to the outer side, obtaining a reverse height measurement sequence. Through bidirectional height measurement, unidirectional errors caused by mechanical hysteresis, local edge chamfering, and sensor response hysteresis can be reduced.

[0044] To ensure that the boundary abrupt change determination matches the medium thickness, the average height of two adjacent height measurement points on the outer side of the boundary is selected as the outer reference height along the same height measurement path, and the average height of two adjacent height measurement points on the inner side of the boundary is selected as the inner reference height. A preset threshold is determined according to a preset ratio of the difference between the two. The calculation formula is as follows: ;

[0045] In the formula, and The height values ​​of two adjacent elevation measurement points outside the boundary, in units of . ; and The height values ​​of two adjacent elevation measurement points inside the boundary, in units of . ; The outer reference height is used to characterize the stable height of the exposed area of ​​the printing platform; This is the inner reference height, used to characterize the stable height of irregularly shaped media surfaces; This is the proportionality coefficient; This is a preset threshold, in units of This formula uses the actual height difference between the platform area and the medium area as the threshold benchmark, and then controls the sensitivity through a proportional coefficient, so that the boundary detection threshold can adaptively change with the medium thickness.

[0046] like Figure 2 As shown, in this embodiment, the outer reference height, the inner reference height, the height difference between the inner and outer sides, and the preset threshold calculated by the proportional coefficient constitute the same threshold determination data chain. Whether the height difference between subsequent adjacent points exceeds the threshold is compared with this threshold.

[0047] After obtaining a preset threshold, the height difference between adjacent points on the same path is calculated to identify abrupt boundary changes. The calculation formula is as follows:

[0048] ;

[0049] In the formula, and The first on the altimeter path The and the first The height values ​​of each measuring point, in units of... ; The height difference between two adjacent altimetry points, in units of 1. The reason for using this formula is that the edge of an irregularly shaped medium usually corresponds to a rapid change in the height of multiple consecutive measuring points. A single anomaly may be caused by noise, while two consecutive occurrences exceeding a preset threshold better reflect the true boundary transition. Therefore, during the height measurement process from the outside to the inside of the boundary, when the height difference between adjacent measuring points exceeds a preset threshold twice consecutively for the first time... When measuring height from the inside of the boundary to the outside of the boundary, the first height measurement point among the three consecutive height measurement points is determined as the first position; during the height measurement process from the inside of the boundary to the outside of the boundary, the second position is determined according to the same rule.

[0050] This embodiment provides a set of measured data. An irregularly shaped plastic medium is placed on an aluminum alloy printing platform. The heights of two adjacent measuring points on the outer side of the boundary are 0.18mm and 0.20mm, respectively, while the heights of two adjacent measuring points on the inner side of the boundary are 1.56mm and 1.60mm, respectively. The scaling factor is... Take 0.12. Substituting this into the formula, we can obtain the outer reference height. for Inner reference height for The difference between the two is Preset threshold for In engineering applications .

[0051] Along the direction from the outer side of the boundary to the inner side, the height values ​​of seven consecutive measuring points were measured sequentially at an initial interval of 1.0 mm. These values ​​were 0.19 mm, 0.21 mm, 0.23 mm, 0.46 mm, 1.14 mm, 1.57 mm, and 1.58 mm. Based on the formula for calculating the height difference between adjacent points, the following values ​​were obtained sequentially: , , , , , Comparing the above results with the threshold of 0.167 mm, the first instance of exceeding the threshold twice consecutively is... and The three consecutive height measurement points are point 3, point 4, and point 5. Therefore, point 3 is determined as the first position. If the starting point coordinate of the height measurement path is 0mm, then point 1 is located at 0mm, point 2 at 1.0mm, and point 3 at 2.0mm. Therefore, the first position is 2.0mm.

[0052] The elevation was measured again along the same path from the inside to the outside of the boundary. At the same interval between measurement points, the elevation values ​​of seven consecutive points were measured as follows: 1.59mm, 1.58mm, 1.55mm, 1.08mm, 0.39mm, 0.22mm, and 0.20mm. The elevation differences between adjacent points were calculated as follows: 0.01mm, 0.03mm, 0.47mm, 0.69mm, 0.17mm, and 0.02mm. Compared with the threshold of 0.167mm, the first two consecutive measurements exceeding the threshold were 0.47mm and 0.69mm, corresponding to points 3, 4, and 5 in the reverse sequence. Therefore, point 3 in the reverse sequence was determined as the second position. Since the reverse and forward elevation measurements used the same path and the measurement interval length was 6.0mm, the first point in the reverse sequence corresponded to a forward coordinate of 6.0mm, the second point to 5.0mm, and the third point to 4.0mm. Therefore, the second position was 4.0mm.

[0053] Combination Figure 3 It can be seen that both forward and reverse height measurements exhibit continuous threshold-crossing transition segments between 2.0 mm and 4.0 mm in the same coordinate system. Therefore, the initial boundary interval can fall between 2.0 mm and 4.0 mm.

[0054] After obtaining the first and second positions, the segment between the two positions is used as the initial boundary interval, and the distance between them is compared. In this embodiment, the first position is 2.0 mm, the second position is 4.0 mm, and the distance between them is... The device's preset boundary width threshold is 1.2mm. Since 2.0mm is greater than 1.2mm, it indicates that the boundary transition zone identified under the initial height measurement point spacing is too wide, which may include extended areas caused by medium chamfers, edge burrs, or sensor spot coverage. Therefore, it is necessary to perform encrypted re-measurement within this range.

[0055] Between 2.0mm and 4.0mm, the spacing between the remeasurement points was reduced to 0.25mm, and the height was measured again along the direction from the outside to the inside of the boundary. The remeasured height values ​​were: 0.24mm at 2.00mm, 0.29mm at 2.25mm, 0.37mm at 2.50mm, 0.61mm at 2.75mm, 1.02mm at 3.00mm, 1.41mm at 3.25mm, 1.56mm at 3.50mm, 1.58mm at 3.75mm, and 1.59mm at 4.00mm. The height differences between adjacent points were calculated sequentially, yielding 0.05mm, 0.08mm, 0.24mm, 0.41mm, 0.39mm, 0.15mm, 0.02mm, and 0.01mm. The first two consecutive measurements exceeding the threshold of 0.167mm were 0.24mm and 0.41mm, corresponding to three consecutive height measurement points of 2.50mm, 2.75mm and 3.00mm. Therefore, the first position after the update was determined to be 2.50mm.

[0056] Subsequently, within the same interval, the height was measured again along the direction from the inside to the outside of the boundary at intervals of 0.25 mm. The height values ​​obtained from the reverse remeasurement were as follows: 1.59 mm at 4.00 mm, 1.58 mm at 3.75 mm, 1.57 mm at 3.50 mm, 1.43 mm at 3.25 mm, 1.28 mm at 3.00 mm, 0.80 mm at 2.75 mm, 0.35 mm at 2.50 mm, 0.28 mm at 2.25 mm, and 0.24 mm at 2.00 mm. The height differences between adjacent points were calculated sequentially, yielding 0.01 mm, 0.01 mm, 0.14 mm, 0.15 mm, 0.48 mm, 0.45 mm, 0.07 mm, and 0.04 mm. Comparing the above results with the threshold of 0.167mm, the first two consecutive times exceeding the threshold were 0.48mm and 0.45mm, corresponding to three consecutive height measurement points of 3.00mm, 2.75mm and 2.50mm. Therefore, the updated second position is determined to be 3.00mm.

[0057] After retesting and updating, the first position is 2.50mm, the second position is 3.00mm, and the distance between them is... The width of the boundary is now less than the preset boundary width threshold of 1.2mm. Therefore, the section between 2.50mm and 3.00mm can be identified as the updated boundary region, and the midpoint of this section, 2.75mm, is taken as the boundary position corresponding to the altimeter path. Compared to the initial 2.0mm wide boundary interval obtained from the altimeter measurement, the boundary interval after the remeasurement converges to 0.50mm, significantly improving boundary recognition accuracy.

[0058] like Figure 4 As shown, after encryption and retesting, the continuous threshold range converged from the initial 2.0mm to 4.0mm to 2.50mm to 3.00mm, and the final boundary position was taken as the midpoint of 2.75mm, which can be directly used as the boundary positioning basis for subsequent nozzle height compensation.

[0059] By adopting the above technical approach, the preset threshold can adaptively change with the height difference between the inside and outside of the medium, which can maintain the stability of boundary change judgment; bidirectional height measurement can reduce the position deviation caused by unidirectional measurement; when the distance between the first position and the second position is too large, local densification height measurement can be implemented by reducing the distance between the remeasurement points, which can avoid boundary misjudgment caused by the boundary transition zone being too wide, and provide more reliable boundary basis data for subsequent nozzle height control.

[0060] Based on the updated boundary position, the printhead safety clearance corresponding to the printing area can be further determined by combining the effective height value measured at the boundary.

[0061] Example 2:

[0062] The boundary location has been obtained through prior height measurement. At this boundary location, outer height measurement points, boundary height measurement points, and inner height measurement points are arranged along the direction crossing the boundary, and multiple groups of adjacent height measurement points are set along the boundary extension direction. Each group of height measurement points includes outer height measurement points, boundary height measurement points, and inner height measurement points, used to characterize the height changes of the exposed area of ​​the printing platform, the edge transition area, and the irregularly shaped media surface area.

[0063] In this embodiment, the height sensor acquires multiple sets of boundary height values ​​along a first direction from the outer side of the boundary to the inner side, and then acquires multiple sets of boundary height values ​​again along a second direction from the inner side of the boundary to the outer side. For each set of height measurement points, the difference between the outer height value and the boundary height value is first calculated to form a first difference value, and then the difference between the inner height value and the boundary height value is calculated to form a second difference value. If the first difference value and the second difference value in two adjacent sets of height measurement points maintain the same magnitude pattern, the corresponding boundary height value is determined to be a valid height measurement value; if the magnitude pattern is reversed, the corresponding boundary height value is determined to be an outlier and discarded.

[0064] This embodiment uses the following formula to calculate the difference, the effective value of the direction, and the classification parameters:

[0065] ;

[0066] In the formula, This is the outer height value, in mm, used to characterize the actual height of one side of the printing platform; This is the boundary height value, in mm, used to characterize the measured height of the edge region; This is the inner height value, in mm, used to characterize the actual height of the irregularly shaped medium surface; The first difference, in mm, reflects the degree of deviation of the boundary height value from the outer height value. The second difference, in mm, reflects the degree of deviation of the boundary height value from the inner height value. This is the first valid elevation measurement value in the first direction, in mm; This is the second effective elevation measurement value in the second direction, in mm; The difference between the effective height measurements in two directions, in mm; As the basis for edge compensation, the larger of the two effective height measurements is taken; This is a preset difference threshold, in mm. This is the ratio of the difference to a preset difference threshold. (Comparison) and The purpose is to determine whether the relative positional relationship of the boundary height value between the outer and inner regions remains stable. If the magnitudes are consistent, it indicates that the transition relationship between the boundary height value and adjacent measuring points is normal; if the magnitudes are inconsistent, it indicates that the boundary height value may be affected by edge burrs, local depressions, or instantaneous fluctuations of the sensor.

[0067] In the first direction, multiple boundary height values ​​that continuously satisfy a preset size pattern constitute a first effective sequence, and the maximum boundary height value from this first effective sequence is taken as the first effective height measurement value. In the second direction, a second effective sequence is formed using the same method, and the maximum boundary height value from the second effective sequence is taken as the second effective height measurement value. Selecting the maximum effective height measurement value in each direction ensures that edge compensation is based on the most unfavorable true effective height in that direction, thereby covering the risk of height bias caused by slight edge warping, local protrusions, and differences in scanning direction. Then from... and Take the larger value as This allows the edge compensation basis to be consistent with the actual higher boundary state.

[0068] The nozzle gap height is determined using the following formula:

[0069] ;

[0070] In the formula, This refers to the nozzle gap height, in mm. Preset safety clearance, unit: mm; This refers to the additional clearance, expressed in mm. If the difference between the effective height measurements in the two directions does not exceed a preset difference threshold, it indicates good consistency between the height measurement results in both directions, requiring only the addition of a preset safety clearance to the edge compensation basis. If the difference exceeds the preset difference threshold, it indicates directional sensitivity or local instability in the boundary area, necessitating the introduction of an additional clearance to increase the safety margin when the nozzle passes through the edge. Ratio Used to characterize the degree of deviation. The larger the value, the more significant the difference in boundary conditions measured in the two directions, and the higher the corresponding additional clearance level.

[0071] This embodiment provides a set of actual test data. An irregularly shaped plastic medium is placed on a printing platform, and four groups of adjacent height measurement points are set along a first direction at the boundary. The outer height of the first group is 0.22mm, the boundary height is 1.08mm, and the inner height is 1.62mm; the outer height of the second group is 0.24mm, the boundary height is 1.15mm, and the inner height is 1.66mm; the outer height of the third group is 0.23mm, the boundary height is 1.22mm, and the inner height is 1.69mm; the outer height of the fourth group is 0.24mm, the boundary height is 0.74mm, and the inner height is 1.68mm. Combined with... Figure 5 It can be seen that the height of the first three sets of boundaries in the first direction increases along the measurement sequence, while the height of the fourth set of boundaries drops significantly.

[0072] like Figure 5 As shown, the above data in the first direction are calculated group by group. In the first group, the first difference is... mm, the second difference is mm, satisfying In the second group, the first difference is mm, the second difference is mm, satisfying In the third group, the first difference is mm, the second difference is mm, satisfying In the fourth group, the first difference is mm, the second difference is mm, satisfying Therefore, the magnitude patterns of the first to third groups are consistent, while the fourth group exhibits a reversed pattern. Consequently, the fourth group's boundary height value of 0.74 mm is considered an outlier and is not included in the valid sequence. The continuous valid boundary height values ​​in the first direction are 1.08 mm, 1.15 mm, and 1.22 mm, with the maximum value of 1.22 mm determined as the first valid height measurement value. .

[0073] Three groups of adjacent height measurement points were set along the second direction. The outermost height of the first group was 0.21 mm, the boundary height was 0.96 mm, and the innermost height was 1.59 mm; the outermost height of the second group was 0.22 mm, the boundary height was 1.02 mm, and the innermost height was 1.61 mm; the outermost height of the third group was 0.23 mm, the boundary height was 1.08 mm, and the innermost height was 1.63 mm. (Combined with...) Figure 6 It can be seen that the first difference of each group in the second direction is higher than the second difference, and there is no reversal of the size pattern.

[0074] like Figure 6 As shown, the corresponding calculations are as follows: In the first group, the first difference is... mm, the second difference is mm, satisfying In the second group, the first difference is mm, the second difference is mm, satisfying In the third group, the first difference is mm, the second difference is mm, satisfying The three sets of data show a consistent pattern, therefore the boundary height values ​​of 0.96mm, 1.02mm, and 1.08mm constitute the continuous effective boundary height values ​​in the second direction, with the maximum value of 1.08mm determined as the second effective height measurement value. .

[0075] After obtaining the effective elevation measurements in two directions, the basis for edge compensation is first determined. The first effective elevation measurement is 1.22mm, and the second effective elevation measurement is 1.08mm; therefore, the basis for edge compensation is... for mm. Then calculate the difference between the effective height measurements in the two directions. mm. In this embodiment, a preset difference threshold is used. Set to 0.08mm, preset safety clearance. Set to 0.30mm. Combined Figure 7 It can be seen that the difference in response to edge height in the two directions has exceeded the allowable fluctuation range, and an additional gap needs to be introduced.

[0076] Additional clearances are determined using a tiered approach. The equipment has a pre-set additional clearance tier table, where when... When, corresponding to the first-level additional clearance, the clearance increment is 0.05mm; when When, corresponding to the secondary additional clearance, the clearance increment is 0.10mm; when At that time, corresponding to the third-level additional clearance, the clearance increment is 0.15mm. Substituting the data from this embodiment, we can obtain... The ratio is located at Within this range, the additional clearance level is therefore determined to be Level II, corresponding to the additional clearance. It is 0.10mm. For example... Figure 7 As shown, there is a monotonic correspondence between the ratio classification and the additional gap classification. The higher the degree of deviation, the larger the additional gap, so as to ensure that the nozzle has sufficient safety margin when crossing the edge.

[0077] like Figure 7 As shown, substituting the above parameters into the formula for calculating the nozzle gap height yields the nozzle gap height. mm. If in this embodiment... If the difference does not exceed the preset threshold, the nozzle gap height will only be adjusted according to... The calculation does not include additional gaps. This embodiment uses a differential grading mechanism to ensure that the nozzle gap setting simultaneously reflects the highest effective height at the edge and the consistency of height measurement in both directions, avoiding insufficient safety margins due to relying solely on height measurement results in a single direction.

[0078] Using the above method, abnormal boundary height measurements can be identified and eliminated, preventing abnormal boundary heights from participating in subsequent control calculations. When there are significant differences between the height measurement results in both directions, the safety margin can be increased by linking the difference threshold with the additional gap level. Through graded additional gap control, the risk of the printhead scraping the edge of irregularly shaped media can be reduced. At the same time, since the edge compensation is based on continuous and effective height measurements, the printhead gap height will not be excessively amplified, ensuring both printing safety and gap control accuracy.

Claims

1. A method for height optimization of a shaped media print based on multi-point height measurement and edge compensation, characterized in that, include: Obtain the boundary position of the irregularly shaped medium on the printing platform; wherein, along the height measurement path crossing the boundary position, the height is measured sequentially in the direction from the outside of the boundary to the inside of the boundary and in the direction from the inside of the boundary to the outside of the boundary, respectively, to determine a first position and a second position where the change in height value between the two measurements exceeds a preset threshold, and the boundary position is determined based on the first position and the second position; when the distance between the first position and the second position is greater than a preset boundary width threshold, the height is measured again between the first position and the second position at a distance smaller than the initial height measurement point distance, and the boundary position is updated based on the position where the change in height value between the two measurements exceeds the preset threshold; Multiple elevation measurement points are set up along the direction of crossing the boundary, located outside the boundary, at the boundary, and inside the boundary. The elevation is measured in the order of the outer elevation measurement point, the boundary elevation measurement point, and the inner elevation measurement point to obtain the outer elevation value, the boundary elevation value, and the inner elevation value. Based on the relationship between the outer height value, the boundary height value, and the inner height value, it is determined whether the boundary height value is a valid height measurement value. Specifically, for two sets of height measurement points adjacent to each other along the boundary extension direction, the difference between the outer height value and the boundary height value is calculated to form a first difference value, and the difference between the inner height value and the boundary height value is calculated to form a second difference value. When the first difference value in both sets of height measurement points is greater than the second difference value, or both are less than the second difference value, the boundary height value is determined to be a valid height measurement value. When the magnitudes of the first difference value and the second difference value in the two sets of height measurement points are inconsistent, the boundary height value is determined to be an invalid height measurement value. The edge compensation basis is determined based on the effective height measurement value, and the nozzle gap height corresponding to the irregular media printing area is determined based on the edge compensation basis; wherein, a first effective height measurement value and a second effective height measurement value are determined along the direction from the outside of the boundary to the inside of the boundary and the direction from the inside of the boundary to the outside of the boundary, respectively; the first effective height measurement value and the second effective height measurement value are compared, and the effective height measurement value with the larger value is determined as the edge compensation basis, and the nozzle gap height is determined based on the edge compensation basis.

2. The method for optimizing the printing height of irregularly shaped media based on multi-point height measurement and edge compensation according to claim 1, characterized in that, During the height measurement process from the outside of the boundary to the inside of the boundary, the first height measurement point among three consecutive height measurement points where the height difference between adjacent height measurement points exceeds the preset threshold twice is determined as the first position; during the height measurement process from the inside of the boundary to the outside of the boundary, the first height measurement point among three consecutive height measurement points where the height difference between adjacent height measurement points exceeds the preset threshold twice is determined as the second position.

3. The method for optimizing the printing height of irregularly shaped media based on multi-point height measurement and edge compensation according to claim 1, characterized in that, The preset threshold is determined based on the outer reference height and the inner reference height on the same altimetry path; wherein, the outer reference height is the average height of two adjacent altimetry points outside the boundary, the inner reference height is the average height of two adjacent altimetry points inside the boundary, and the preset threshold is a preset ratio of the difference between the outer reference height and the inner reference height.

4. The method for optimizing the printing height of irregularly shaped media based on multi-point height measurement and edge compensation according to claim 1, characterized in that, Multiple boundary height values ​​are obtained along a first direction from the outer side of the boundary to the inner side of the boundary, and the maximum value among the boundary height values ​​that continuously satisfy a preset size relationship is determined as the first effective height measurement value; multiple boundary height values ​​are obtained along a second direction from the inner side of the boundary to the outer side of the boundary, and the maximum value among the boundary height values ​​that continuously satisfy the preset size relationship is determined as the second effective height measurement value.

5. The method for optimizing the printing height of irregularly shaped media based on multi-point height measurement and edge compensation according to claim 1, characterized in that, Calculate the difference between the first valid height measurement value and the second valid height measurement value; When the difference is less than or equal to a preset difference threshold, the sum of the edge compensation basis and the preset safety gap is determined as the nozzle gap height; When the difference is greater than the preset difference threshold, the sum of the edge compensation basis, the preset safety gap, and the additional gap determined according to the difference is determined as the nozzle gap height.

6. The method for optimizing the printing height of irregularly shaped media based on multi-point height measurement and edge compensation according to claim 5, characterized in that, Calculate the ratio of the difference to the preset difference threshold; determine the corresponding additional gap level based on the preset interval in which the ratio falls; and determine the preset gap increment corresponding to the additional gap level as the additional gap.

Images