A net drawing machine and a tension control method thereof

Abstract

This invention discloses a screen printing machine and its tension control method, relating to the field of screen printing equipment technology. The screen printing machine includes a frame, a clamping unit, and a tension control mechanism. Its core improvement lies in the addition of a distributed tension sensing system, a piezoelectric fine-tuning array, and a controller. The distributed tension sensing system detects the screen tension in real time in each area through tension sensors installed in the clamping unit. The piezoelectric fine-tuning array includes a piezoelectric drive unit that is drively connected to the clamping unit, which can drive the clamping unit to generate micron-level displacement. The controller receives the tension detection signal and, when the tension deviation in a certain area exceeds a threshold, applies a control voltage to the corresponding piezoelectric drive unit, driving the clamping unit in that area to perform a slight displacement, thereby achieving fine compensation of local tension. This realizes local, dynamic, and high-precision compensation of screen tension, improving the uniformity and stability of the screen tension.

Description

Technical Field

[0001] This invention relates to the field of screen printing plate-making equipment, and in particular to a screen stretching machine and a tension control method applied to the screen stretching machine. Background Technology

[0002] In the screen printing plate-making process, screen stretching is a crucial step. Its purpose is to evenly stretch and fix the screen onto the frame to obtain stable printing tension. Traditional screen stretching machines typically include a frame, multiple symmetrically arranged clamping units, and a stretching mechanism. The clamping units hold the edges of the screen, and the stretching mechanism drives the clamping units to move outward, thereby tightening the screen.

[0003] However, in practice, due to various factors such as the anisotropy of the screen material, the irregularity of the screen frame, uneven clamping force, and frictional resistance during the stretching process, even if the overall stretching displacement is consistent, the tension in different areas of the screen often exhibits uneven distribution. This localized tension deviation leads to uneven screen tension in the final printing process, affecting dimensional accuracy, ink transmittance, and printing durability. Especially in high-precision, multi-color printing processes, uneven tension can directly cause serious quality problems such as misregistration and image distortion. Summary of the Invention

[0004] The objective of this invention is achieved through the following technical solution:

[0005] This invention provides a screen stretching machine, including a frame, clamping units, and a tension control mechanism. The frame is provided with support units for placing screen frames. The clamping units are symmetrically arranged on the frame. The improvement lies in that the screen stretching machine further includes:

[0006] The distributed tension sensing system includes multiple tension sensors mounted on the clamping unit for real-time detection of the wire mesh tension value in the corresponding area.

[0007] The piezoelectric fine-tuning array includes multiple piezoelectric driving units that are drively connected to the clamping unit, and are used to drive the corresponding clamping unit to generate micron-level precision displacement.

[0008] The controller is electrically connected to both the distributed tension sensing system and the piezoelectric fine-tuning array. This controller receives detection signals from each tension sensor and, when the deviation between the detected tension value in a certain area and the preset target tension value exceeds a preset threshold, applies a control voltage to the corresponding piezoelectric drive unit to drive the clamping unit in that area to perform a slight advance or retraction, thereby achieving fine compensation for local tension.

[0009] Preferably, the clamping unit includes a main clamping part and a fine-tuning base. The main clamping part is mounted on the tensioning mechanism's mesh slider for performing large-amplitude tensioning actions. The fine-tuning base is slidably mounted on the main clamping part, and the piezoelectric drive unit is mounted between the main clamping part and the fine-tuning base. With this structure, the piezoelectric drive unit can drive the fine-tuning base to produce independent micro-displacements relative to the main clamping part, thereby correcting local tension without affecting the overall tensioning process.

[0010] Preferably, the piezoelectric drive unit is a stacked piezoelectric ceramic actuator. Its displacement output end is connected to the clamping unit, and its fixed end is connected to the pull net slider. The stacked piezoelectric ceramic actuator has the advantages of small size, large output force, high displacement resolution, and extremely fast response speed, making it very suitable for micron-level tension precision compensation.

[0011] Preferably, the tension sensor in the distributed tension sensing system is a thin-film pressure sensor, which is attached to the clamping surface of the clamping unit. This allows for the most direct and accurate sensing of tension changes in the wire mesh near the clamping point, improving detection accuracy.

[0012] Preferably, the controller includes a feedforward compensation module. This module generates a base control voltage in advance and applies it to the piezoelectric drive unit based on preset wire mesh material property curves (such as elastic modulus and tensile curve) and the total tensile target value. This can preemptively offset most of the nonlinear deformation caused by material properties, making subsequent feedback compensation more accurate and faster.

[0013] Preferably, the tension fine compensation performed by the controller is dynamic real-time compensation, with a system response time of less than 10 milliseconds. Leveraging the fast response characteristics of the piezoelectric drive unit, this invention achieves near real-time tension fluctuation suppression, significantly improving the stability of tension control.

[0014] This invention also provides a tension control method for a screen stretching machine, applicable to any of the screen stretching machines described above. The method includes the following steps:

[0015] Step S1: The current tension value of the corresponding area of ​​each clamping unit is collected in real time through the distributed tension sensing system.

[0016] Step S2: Calculate the deviation between the current tension value and the preset target tension value for each region.

[0017] Step S3: Determine whether the deviation value exceeds a preset threshold. If it does, identify the target area that needs adjustment.

[0018] Step S4: Calculate the compensation control voltage of the piezoelectric drive unit corresponding to the target area based on the magnitude and direction of the deviation value.

[0019] Step S5: Apply the compensation control voltage to the piezoelectric drive unit to generate a micron-level displacement, driving the corresponding clamping unit to perform a slight advance (to increase tension) or retraction (to reduce tension), thereby changing the local tension in the region.

[0020] Step S6: Repeat steps S1 to S5 to form a closed-loop control loop until the tension deviation values ​​of all areas converge within the preset threshold.

[0021] Preferably, in step S4, when calculating the compensation control voltage, the elastic modulus of the wire mesh material in that area is also introduced as a calculation parameter to establish a precise mapping relationship between the deviation value and the required compensation displacement. This converts the tension deviation into a precise displacement compensation amount, improving the control accuracy.

[0022] Preferably, in step S5, while compensating for the tension in the target area, the tensioning mechanisms in other areas are kept locked. This prevents adjustments in one area from interfering with neighboring areas that have already reached tension equilibrium, thus accelerating the convergence speed.

[0023] Preferably, the method further includes a self-learning step: recording the process data (such as deviation value, compensation voltage, response time) and final effects (such as residual deviation, settling time) for each compensation control. By analyzing this historical data, the control model (such as PID parameters or intelligent algorithm model) between the deviation value and the compensation voltage can be optimized, making the system increasingly intelligent with use and more adaptable to different materials and processes. Beneficial effects

[0024] Compared with the prior art, the present invention has the following significant advantages:

[0025] 1. Achieve high-precision compensation for local tension: By combining distributed sensing and piezoelectric fine-tuning array, it can accurately sense and correct minute tension unevenness in various areas of the screen, improving tension uniformity to an unprecedented level, which is especially suitable for high-precision screen printing.

[0026] 2. Fast response speed: The piezoelectric drive unit has a millisecond-level response speed. Combined with a high-speed controller, it can achieve dynamic real-time compensation and effectively suppress instantaneous tension fluctuations during the stretching process.

[0027] 3. High control precision: Piezoelectric drive can achieve displacement control at the nanometer to micrometer level. With feedforward compensation and accurate mathematical modeling, the tension control precision is far higher than that of traditional mechanical adjustment.

[0028] 4. High level of intelligence: By introducing a self-learning function, the control system can continuously optimize control parameters to adapt to different batches and materials of wire mesh, reducing the difficulty of operation and the dependence on the operator's experience.

[0029] 5. Compact structure and easy integration: The piezoelectric drive unit is small in size and can be easily integrated into the existing clamping unit structure without making major changes to the main structure of the screen stretching machine, resulting in relatively low cost. Attached Figure Description

[0030] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0031] Figure 1 This is a schematic diagram of the overall structure of the screen pulling machine in an embodiment of the present invention.

[0032] Figure 2 This is a diagram of the control system architecture for the net pulling machine of the present invention.

[0033] Figure 3 This is a flowchart of the tension control method for the screen pulling machine of the present invention.

[0034] Figure label:

[0035] 1-Frame, 2-Support unit, 3-Clamping unit, 31-Main clamping part, 32-Fine adjustment base, 4-Tension sensor, 5-Piezoelectric drive unit, 6-Screen pulling slider, 7-Controller, 71-Feedforward compensation module, 72-Self-learning module; 8-Wire mesh. Detailed Implementation

[0036] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0037] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0038] like Figure 1 As shown, this embodiment provides a wire mesh stretching machine. The machine mainly includes a frame 1. A support unit 2 for placing the wire mesh frame (not shown in the figure) is located in the center of the frame 1. Multiple clamping units 3 are symmetrically arranged around the frame 1. The clamping units 3 are used to clamp the edges of the wire mesh. The entire wire mesh stretching machine also includes a main stretching mechanism (not shown in detail in the figure, typically a motor-driven lead screw or linear motor), used to drive the clamping units 3 to move outward as a whole, completing the basic stretching of the wire mesh.

[0039] The core improvement of this invention lies in the introduction of a distributed tension sensing system, a piezoelectric fine-tuning array, and a controller.

[0040] Distributed tension sensing system: such as Figure 2 As shown, a thin-film pressure sensor 4 is attached to the clamping surface (i.e., the surface in contact with the wire mesh) of each clamping unit 3, serving as a distributed tension sensor. These pressure sensors can detect the pressure exerted by the wire mesh on their respective areas in real time and independently, and the pressure value reflects the wire mesh tension in that area.

[0041] Piezoelectric trimmer array: combined Figure 2 The piezoelectric fine-tuning array consists of multiple piezoelectric driving units 5, each corresponding to and connected to a clamping unit 3. Specifically, the clamping unit 3 can be designed as a combined structure, including a main clamping part 31 and a fine-tuning base 32. The main clamping part 31 is fixedly mounted on the mesh-pulling slider 6 of the stretching mechanism for performing large-amplitude stretching actions. The fine-tuning base 32 is slidably mounted on the main clamping part 31 via a guide rail or slider structure, and the clamping action of the mesh occurs on the fine-tuning base 32. The piezoelectric driving unit 5 is preferably a stacked piezoelectric ceramic actuator, with its fixed end mounted on the main clamping part 31 and its displacement output end connected to the fine-tuning base 32. When the piezoelectric driving unit 5 is energized to extend or shorten, it can drive the fine-tuning base 32 to produce a precise displacement at the micron or even nanometer level relative to the main clamping part 31, thereby finely adjusting the local tension of the mesh at the clamping point.

[0042] Controller: Controller 7 is electrically connected to all tension sensors 4 and all piezoelectric drive units 5. Controller 7 internally includes a signal acquisition module, a data processing module, a deviation judgment module, and a control output module. Its working principle will be explained in detail in conjunction with the control methods described below.

[0043] This invention provides a tension control method for a screen stretching machine, which can be applied to the aforementioned screen stretching machine. For example... Figure 3 As shown, the method includes the following steps:

[0044] Step S1: Real-time data acquisition. The controller 7 acquires the readings of the thin-film pressure sensor 4 on each clamping unit 3 at an extremely high frequency (e.g., 1000 times per second) through a distributed tension sensing system, thereby obtaining the real-time tension value T(i) of each area of ​​the wire mesh at the current moment (i represents the i-th clamping unit).

[0045] Step S2: Deviation Calculation. The controller 7 compares the real-time tension value T(i) of each region acquired with the target tension value T_target of that region pre-stored in the controller, and calculates the deviation value Ei = T(i) - T_target.

[0046] Step S3: Deviation Judgment and Region Identification. Controller 7 determines whether the absolute value of the deviation value Ei for each region exceeds a preset allowable threshold ΔT (e.g., 0.1 N / cm). If |Ei| ≤ ΔT, the tension in that region is considered acceptable and no adjustment is needed. If |Ei| > ΔT, the region is identified as the "target region" requiring adjustment, and the direction of the deviation is recorded (positive deviation indicates excessive tension, negative deviation indicates insufficient tension).

[0047] Step S4: Compensation Voltage Calculation. For each identified target area, the controller 7 calculates the required compensation displacement ΔLi based on its deviation value Ei. This calculation process introduces a key parameter—the elastic modulus k of the wire mesh material in that area.

[0048] For small deformations, the tension can be approximated as being proportional to the displacement, i.e., ΔLi = f(Ei, k) = α×Ei / k, where α is a correction coefficient that takes into account factors such as system stiffness. The controller 7 then converts the required compensation displacement ΔLi into the corresponding compensation control voltage Ui based on the voltage-displacement characteristic curve of the piezoelectric drive unit 5.

[0049] Step S5: Perform fine-tuning compensation. Controller 7 applies the compensation control voltage Ui calculated in step S4 to the piezoelectric drive unit 5 corresponding to the target area. If the deviation Ei is positive (excessive tension), a voltage is applied to contract the piezoelectric drive unit 5, driving the fine-tuning base 32 to retract slightly inward, thereby reducing the local tension in that area; conversely, if the deviation Ei is negative (insufficient tension), a voltage is applied to extend the piezoelectric drive unit 5, driving the fine-tuning base 32 to advance slightly outward, thereby increasing the local tension in that area. During this step, controller 7 ensures the main tensioning mechanism is locked and does not issue commands to clamping units in other non-target areas to avoid mutual interference.

[0050] Step S6: Closed-loop iteration. After one fine-tuning operation, the system immediately returns to step S1, re-collects the tension values ​​of all areas, and performs calculations, judgments, and adjustments again. This closed-loop control process repeats at an extremely high frequency (system response time less than 10 milliseconds) until the tension deviation values ​​|Ei| of all areas converge within the preset threshold ΔT. At this point, the entire wire mesh reaches a highly uniform tension state.

[0051] Further optimizations can be made based on the above. For example... Figure 2As shown, the controller 7 also integrates a feedforward compensation module 71. Before starting the aforementioned closed-loop feedback control, or while the main stretching mechanism is performing significant stretching, the feedforward compensation module 71 calculates a predictive base control voltage based on the pre-input wire mesh material characteristic curve (such as the elastic modulus-stress curve) and the total target stretching displacement, and pre-applies it to all piezoelectric drive units 5. This compensates for the uneven tension caused by the material's inherent properties (such as nonlinearity in the initial stretching stage), allowing the closed-loop feedback control to start from a more optimal point, thereby further accelerating the adjustment speed and improving the final accuracy.

[0052] In addition, the controller 7 also incorporates a self-learning module 72. After each net-pulling task is completed, the self-learning module 72 records key data from the entire process, including the initial deviation of each region, the compensation voltage sequence, the response time, and the final residual deviation. Through analysis and learning from a large amount of historical data, the self-learning module 72 can continuously optimize the mapping relationship model between the deviation value Ei and the compensation voltage Ui in step S4 (e.g., dynamically adjusting the correction coefficient α, or optimizing a neural network model), making the control more precise and efficient when processing the same or similar materials in the future.

[0053] In summary, this invention, by introducing distributed tension sensing and piezoelectric effect-based fine-tuning technology, achieves localized, precise, rapid, and intelligent closed-loop control of wire mesh tension, significantly improving the quality and efficiency of wire mesh production, and has high practical value.

[0054] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A screen stretching machine, comprising a frame, clamping units, and a tension control mechanism, wherein the frame is provided with support units for placing screen frames, and the clamping units are symmetrically arranged on the frame, characterized in that, Also includes A distributed tension sensing system includes tension sensors installed in the clamping unit for real-time detection of the wire mesh tension value in the corresponding area; The piezoelectric fine-tuning array includes a piezoelectric driving unit that is driven in connection with the clamping unit, for driving the clamping unit to generate micron-level displacement; The controller is electrically connected to the distributed tension sensing system and the piezoelectric fine-tuning array, respectively. It is used to receive the detection signals of each tension sensor and apply a control voltage to the corresponding piezoelectric drive unit when the deviation between the detected tension value and the target tension value in a certain area exceeds a preset threshold. This drives the clamping unit in that area to perform a slight advance or retraction, thereby achieving fine compensation of local tension.

2. The screen stretching machine according to claim 1, characterized in that, The clamping unit includes a main clamping part and a fine-tuning base; the main clamping part is mounted on the pull-out slider of the stretching mechanism and is used to perform the stretching action; the fine-tuning base is slidably mounted on the main clamping part, and the piezoelectric drive unit is mounted between the main clamping part and the fine-tuning base and is used to drive the fine-tuning base to produce a micro-displacement relative to the main clamping part.

3. The screen stretching machine according to claim 1, characterized in that, The piezoelectric drive unit is a stacked piezoelectric ceramic actuator, with its displacement output end connected to the clamping unit and its fixed end connected to the pull net slider.

4. The screen stretching machine according to claim 1, characterized in that, The tension sensor in the distributed tension sensing system is a thin-film pressure sensor, which is attached to the clamping surface of the clamping unit.

5. The screen stretching machine according to claim 1, characterized in that, The controller includes a feedforward compensation module, which generates a base control voltage based on a preset wire mesh material characteristic curve and a stretching target value, and applies it to the piezoelectric drive unit.

6. The screen stretching machine according to claim 1, characterized in that, The tension fine compensation performed by the controller is a dynamic real-time compensation with a response time of less than 10 milliseconds.

7. A tension control method for a screen stretching machine, applied to the screen stretching machine according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: Real-time acquisition of the current tension value of the corresponding area of ​​each clamping unit through a distributed tension sensing system; Step S2: Calculate the deviation between the current tension value and the preset target tension value in each region; Step S3: Determine whether the deviation value exceeds a preset threshold. If it does, identify the target area that needs to be adjusted. Step S4: Calculate the compensation control voltage of the piezoelectric drive unit corresponding to the target area based on the magnitude and direction of the deviation value; Step S5: Apply the compensation control voltage to the piezoelectric drive unit to generate a micron-level displacement, thereby driving the corresponding clamping unit to perform a slight displacement to change the local tension in the region. Step S6: Repeat steps S1 to S5 until the tension deviation values ​​of all regions converge within the preset threshold.

8. The control method according to claim 7, characterized in that, In step S4, when calculating the compensation control voltage, the elastic modulus of the material of the wire mesh in this area is also introduced as a calculation parameter to establish a mapping relationship between the deviation value and the compensation displacement.

9. The control method according to claim 7, characterized in that, In step S5, while compensating for the tension in the target area, the tensioning mechanisms in other areas are kept in a locked state.

10. The control method according to claim 7, characterized in that, The method also includes a self-learning step: recording the process data and final effect of each compensation control, and optimizing the control model between the deviation value and the compensation voltage.

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