Printing machine capable of measuring solder paste allowance

Abstract

The invention relates to the technical field of solder paste printing, and particularly discloses a printing machine capable of measuring solder paste allowance. The air pressure supply system is used for injecting compressed air into a top cavity above the piston; the pressure sensor is used for monitoring air pressure data of the top cavity; the conveying pipeline is used for communicating a bottom outlet of the solder paste tank to the upper part of the steel mesh; the control system is used for controlling the air pressure supply system to start to inject compressed gas into the top cavity when solder paste needs to be supplemented; after the air pressure supply system begins to supply air and within a specified time period before the solder paste begins to flow out of the solder paste tank, acquiring air pressure data through the pressure sensor; and according to the air pressure data, the current solder paste allowance is obtained. According to the printing machine capable of measuring the solder paste allowance, the solder paste allowance detection cost can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tin paste printing, and particularly relates to a tin paste printing machine capable of measuring tin paste residue. BACKGROUND

[0002] The tin paste printing machine is a key equipment of a surface mount technology (SMT) production line, and is usually provided with a tin paste supply system for accurately printing tin paste on a PCB pad.

[0003] The tin paste supply system is usually composed of the following inherent components:

[0004] A tin paste tank, which is internally provided with a piston capable of moving up and down, and a cavity below the piston for containing tin paste;

[0005] A gas pressure supply system, including a gas source, a pressure regulating valve and a control solenoid valve, for injecting compressed gas into the top cavity above the piston;

[0006] A pressure sensor for monitoring the gas pressure of the top cavity;

[0007] A delivery pipeline for connecting the bottom outlet of the tin paste tank to above the steel mesh.

[0008] In this inherent system, the pressure sensor is part of the gas pressure control loop, and its inherent function is to maintain the stability of the tin paste supplement pressure.

[0009] The standard working process of the tin paste supply system is as follows:

[0010] When the control system of the printing machine determines that the tin paste needs to be supplemented, the control system sends a gas supplement instruction, the compressed gas enters the top space of the tin paste tank, pushes the piston to move downward, and then the tin paste is squeezed to the surface of the steel mesh through the delivery pipeline. In this process, the pressure sensor continuously monitors the gas pressure in the tank to ensure that the gas supplement pressure is stable, thereby ensuring that the tin paste output on the steel mesh is stable. That is, the traditional cooperation of the pressure sensor and the control system is only to cooperate with the gas pressure supply system to ensure that the gas pressure value in the tin paste tank is stable within the preset target range, so as to maintain the basic consistency of the tin paste output. After the tin paste is supplemented, the gas pressure supply system is turned off.

[0011] However, the inherent system does not traditionally have a tin paste residue detection function. Therefore, in order to realize the tin paste residue detection function, the existing printing machine needs to add special detection hardware outside the inherent system, thereby introducing the following defects:

[0012] (1) Laser ranging scheme

[0013] A light transmission hole is opened on the top cover of the solder paste tank, and a laser sensor is installed above the light transmission hole, the laser beam emitted by the laser sensor irradiates to the top surface of the piston through the light transmission hole, so as to calculate the displacement parameter of the piston, and finally the displacement parameter of the piston is combined with the size parameter of the solder paste tank to calculate the residual amount of solder paste in the tank.

[0014] This requires adding a hardware device (laser sensor), which increases the hardware cost.

[0015] (2) Magnetic scale detection scheme

[0016] A precise magnetic scale is installed at the piston, and a magnetic scale reading head is installed on the solder paste tank. After the piston drives the magnetic scale to move, the magnetic scale reading head can obtain the displacement parameter of the piston, and then calculate the residual amount of solder paste in the tank.

[0017] This also requires adding hardware devices (magnetic scale and magnetic scale reading head). Moreover, the solder paste tank is a standard part, and most solder paste tanks do not have magnetic scale and magnetic scale reading head, so the modification cost is very high.

[0018] In summary, the existing solder paste residual amount detection scheme of the printing machine needs to add additional detection hardware, which directly increases the manufacturing cost and structural complexity of the equipment. Therefore, the existing printing machine needs to be improved to solve the problem of high cost of solder paste residual amount detection.

[0019] The above information disclosed in the background section is only included to enhance the understanding of the background of the present disclosure, and therefore can contain information that is not prior art known to those of ordinary skill in the art at the time of the present disclosure. SUMMARY

[0020] An object of the present application is to provide a printing machine capable of measuring the residual amount of solder paste, which can effectively reduce the detection cost of the residual amount of solder paste.

[0021] To achieve the above object, the present application provides a printing machine capable of measuring the residual amount of solder paste, comprising:

[0022] A solder paste tank is internally provided with a piston that can move up and down, and a cavity below the piston is used to contain solder paste;

[0023] A gas pressure supply system is connected to the top of the solder paste tank and used to inject compressed gas into the top cavity above the piston;

[0024] A pressure sensor is connected to the solder paste tank through the gas pressure supply system and used to monitor the gas pressure data of the top cavity;

[0025] A delivery pipeline is connected from the bottom outlet of the solder paste tank to above the steel mesh;

[0026] A control system is communicatively connected to the air pressure supply system and the pressure sensor, respectively, for:

[0027] When the tin paste needs to be replenished, the control system controls the air pressure supply system to start injecting compressed air into the top cavity;

[0028] Within a specified time period before the tin paste starts to flow out of the tin paste pot after the air pressure supply system starts to supply air, the pressure sensor acquires air pressure data;

[0029] According to the air pressure data, the current tin paste remaining amount is obtained.

[0030] Optionally, according to the air pressure data, the current tin paste remaining amount is obtained, including the following steps:

[0031] According to the air pressure data, a gas pressure change characteristic value is determined;

[0032] Based on the pre-stored corresponding relationship between the gas pressure change characteristic value and the tin paste remaining amount, the current tin paste remaining amount is obtained;

[0033] The gas pressure change characteristic value is the air pressure rise value of the gas in the top cavity within the specified time period Or the pressure rise rate .

[0034] Optionally, the pre-stored corresponding relationship between the gas pressure change characteristic value and the tin paste remaining amount is obtained through the following calibration process:

[0035] When the tin paste pot is in a plurality of different known tin paste remaining amount states, the control system controls the air pressure supply system to supply air to the top cavity at a plurality of air supply flow rates;

[0036] Within the specified time period of each air supply, the pressure sensor acquires air pressure data to calculate a gas pressure change characteristic value;

[0037] According to a plurality of air supply flow rates, a plurality of known tin paste remaining amounts, and the calculated gas pressure change characteristic values, a first database is created to represent the corresponding relationship between the air supply flow rate, the tin paste remaining amount, and the gas pressure change characteristic value.

[0038] Optionally, it further includes a temperature sensor communicatively connected to the control system for monitoring the air supply temperature of the compressed gas in the top cavity;

[0039] The pre-stored corresponding relationship between the gas pressure change characteristic value and the tin paste remaining amount is obtained through the following calibration process:

[0040] For different air supply temperatures, when the tin paste pot is in a plurality of different known tin paste remaining amount states, the control system controls the air pressure supply system to supply air to the top cavity at a plurality of air supply flow rates;

[0041] In the specified time period of each gas supply, the pressure change characteristic value is calculated by acquiring the pressure data through the pressure sensor;

[0042] According to the multiple gas supply temperatures, the multiple gas supply flow rates, the multiple known solder paste residual amounts, and the calculated pressure change characteristic values, a second database is made to represent the corresponding relationship among the gas supply temperature, the gas supply flow rate, the solder paste residual amount, and the pressure change characteristic value.

[0043] Optionally, the current solder paste residual amount is acquired according to the pressure data, including the following steps:

[0044] The gas volume V above the piston is calculated according to the physical model (1) g :

[0045] (1) ;

[0046] The current solder paste residual amount V is calculated according to the physical model (2) s :

[0047] (2) ;

[0048] Wherein,

[0049] V total is the internal volume of the solder paste tank after removing the piston, V g is the gas volume above the piston, V s is the solder paste volume below the piston, used to represent the solder paste residual amount;

[0050] k is the adiabatic index, R is the gas constant, and T is the gas temperature above the piston;

[0051] A e is the gas flow cross-sectional area when the gas pressure supply system outputs compressed gas;

[0052] pz is the pressure data monitored by the pressure sensor;

[0053] p u is the set output pressure of the gas pressure supply system;

[0054] t start is the start time of the specified time period, t end is the end time of the specified time period.

[0055] Optionally, the start time t of the specified time period start is 10 milliseconds after starting gas supply, and the end time t of the specified time period end is 40 milliseconds after starting gas supply.

[0056] Optionally, the control system is further configured to:

[0057] Controlling solder replenishment time: Based on the calculated current solder paste balance, determine the total solder replenishment time t required to maintain a stable solder paste output. 总 .

[0058] Optionally, based on the calculated current solder paste balance, determine the total solder replenishment time t required to maintain a stable solder paste output. 总 ,include:

[0059] The time required to replenish solder paste to reach the specified amount when the solder paste balance is at its maximum value is taken as the reference air supply time t0.

[0060] Based on the calculated current solder paste balance and the pre-stored correspondence between solder paste balance and time compensation value, obtain the time compensation value t corresponding to the current solder paste balance. 补 Wherein, the solder paste balance and the time compensation value t 补 There is a negative correlation;

[0061] Calculate the total resoldering time t corresponding to the current solder paste balance. 总 =Base gas supply time t0 + Time compensation value t 补 And according to the total solder replenishment time t 总 Control the start and stop of the air pressure supply system to ensure that the amount of solder paste dispensed each time is consistent.

[0062] Optionally, the control system is further configured to:

[0063] Reference time calibration: After each new solder paste container is filled, a complete set of steps is performed to trigger solder replenishment, acquire data, and calculate the remaining amount. The calculated remaining amount of solder paste is then calibrated as the maximum remaining amount of solder paste in this container.

[0064] Optionally, the control system is further configured to:

[0065] If the current solder paste balance is lower than a preset threshold, a warning signal is generated and output.

[0066] The beneficial effects of this invention are as follows: It provides a solder paste balance measuring printer, and the specific working process is as follows:

[0067] When the control system determines that the steel mesh needs to be supplemented with tin paste, it will issue an instruction to the air pressure supply system to start the process of injecting compressed gas into the top cavity of the tin paste tank. The key innovation of this process lies in the precise selection of the detection timing: the control system strictly limits the detection window to a very short specified time period after the start of gas supply and before the tin paste starts to flow out. During this window, since the compressed gas has just entered the tank and is only used to establish pressure, it has not yet been able to significantly push the piston to move and cause the tin paste to flow out, so the tin paste in the tank can be approximated as a rigid body. At this time, the air pressure data monitored by the pressure sensor is mainly related to the gas space volume above the piston (i.e. the volume of the top cavity). This gas space volume has a clear correspondence with the tin paste remaining amount (the more the remaining amount, the smaller the gas space).

[0068] The tin paste remaining amount measuring printer provided by the present application can realize online monitoring of the tin paste remaining amount without increasing special detection hardware by reconstructing and cooperatively controlling the functions of the inherent components of the printer (tin paste tank, air pressure supply system, pressure sensor, delivery pipeline, control system), thereby effectively reducing the cost of tin paste remaining amount detection. BRIEF DESCRIPTION OF DRAWINGS

[0069] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0070] Figure 1 The structure diagram of the tin paste remaining amount measuring printer provided by the embodiment.

[0071] In the figure:

[0072] 1, tin paste tank; 101, piston;

[0073] 2, air pressure supply system;

[0074] 3, pressure sensor;

[0075] 4, delivery pipeline

[0076] 5, steel mesh;

[0077] 6, temperature sensor. DETAILED DESCRIPTION

[0078] The term "embodiment" mentioned in the present application means that the specific features, structures or properties described in connection with the embodiment can be included in at least one embodiment of the present application. The term "embodiment" appearing at various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit the independence or association between other embodiments. In principle, in the present application, each technical feature mentioned in each embodiment can be combined in any manner as long as there is no technical contradiction or conflict, to form a corresponding implementable technical solution.

[0079] Unless otherwise defined, the meanings of the technical terms used herein are the same as those commonly understood by those skilled in the art to which the present application belongs; the use of related terms herein is only for the purpose of describing specific embodiments, and is not intended to limit the present application.

[0080] In the description of the present application, the phrase "and / or" is a description of the logical relationship between objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases: A exists, B exists, and A and B exist at the same time. In addition, the character " / " herein generally represents that the associated objects before and after are a "or" logical relationship.

[0081] In the present application, terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, primary and secondary or order relationship between the entities or operations.

[0082] Without more limitations, in the present application, the phrases "include", "contain", "have" or other similar expressions used in the sentence are intended to cover non-exclusive inclusion, and these expressions do not exclude the presence of other elements in the process, method or product including the described elements, so that the process, method or product including a series of elements can not only include those limited elements, but also include other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0083] As the same understanding as in the "Guidelines for Examination", in the present application, the expressions "greater than", "less than", "exceed" and the like are understood as not including the number; the expressions "above", "below", "within" and the like are understood as including the number. In addition, the meaning of "multiple" in the description of the embodiments of the present application is more than two (including two), and similar expressions related to "multiple" are also understood in this way, for example, "multiple groups", "multiple times" and the like, unless otherwise specifically limited.

[0084] In the description of the embodiments of the present application, the spatial relative expressions such as "central", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the orientation or positional relationship shown in the specific embodiments or the drawings, and are only used to facilitate the description of the specific embodiments of the present application or to facilitate the understanding of the reader, and do not indicate or imply that the indicated device or component must have a particular position, a particular orientation, or be constructed or operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0085] Unless otherwise explicitly specified or limited, in the description of the embodiments of the present application, the terms "mount", "connect", "connect", "fix", "set", and the like should be understood broadly. For example, the "connection" can be a fixed connection, or a detachable connection, or an integral setting; it can be a mechanical connection, or an electrical connection, or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art to which the present application belongs, the specific meaning of the above-mentioned terms in the embodiments of the present application can be understood according to the specific circumstances.

[0086] Embodiment 1

[0087] Reference Figure 1 The tin paste residual amount printing machine provided by the embodiment comprises:

[0088] A tin paste tank 1 is internally provided with a piston 101 which can move up and down, and a cavity below the piston 101 is used to accommodate tin paste;

[0089] A gas pressure supply system 2 is communicated to the top of the tin paste tank 1 and is used to inject compressed gas into the top cavity above the piston 101;

[0090] A pressure sensor 3 is communicated to the tin paste tank 1 through the gas pressure supply system 2 and is used to monitor the gas pressure data of the top cavity;

[0091] A delivery pipeline 4 is communicated from the bottom outlet of the tin paste tank 1 to above the steel mesh 5;

[0092] A control system is respectively communicated to the gas pressure supply system 2 and the pressure sensor 3, and is used to:

[0093] S10: Trigger tin supplement: when it is necessary to supplement tin paste, control the gas pressure supply system to start injecting compressed gas into the top cavity;

[0094] S20: Obtain data: After the air pressure supply system starts to supply air, within a specified time period before the solder paste starts to flow out of the solder paste tank, obtain air pressure data through the pressure sensor;

[0095] S30: Calculate the remaining amount: According to the air pressure data, obtain the current solder paste remaining amount.

[0096] The specific working process of the solder paste remaining amount measurable printing machine is as follows:

[0097] When the control system determines that the solder paste needs to be supplemented to the steel mesh, it will issue an instruction to the air pressure supply system to start the process of injecting compressed gas into the top cavity of the solder paste tank. The key innovation of this process lies in the accurate selection of the detection time: the control system strictly limits the detection window to a very short specified time period after the air supply starts and before the solder paste starts to flow out. Within this window, since the compressed gas has just entered the tank and is only used to establish pressure without being able to significantly push the piston to move and cause the solder paste to flow out, the solder paste in the tank can be approximated as a rigid body. At this time, the air pressure data monitored by the pressure sensor is mainly related to the gas space volume above the piston (i.e. the volume of the top cavity). This gas space volume has a clear corresponding relationship with the solder paste remaining amount (the more the remaining amount, the smaller the gas space). Subsequently, the control system calculates the current solder paste remaining amount according to the air pressure data obtained within this specific time period through the built-in algorithm.

[0098] The solder paste remaining amount measurable printing machine provided by the present application can realize online monitoring of the solder paste remaining amount without increasing special detection hardware by reconstructing and cooperatively controlling the functions of the inherent components of the printing machine (solder paste tank, air pressure supply system, pressure sensor, delivery pipeline, and control system), thereby effectively reducing the cost of solder paste remaining amount detection.

[0099] In this embodiment, optionally, the specified time period is within 40 milliseconds from when the air pressure supply system starts to supply air. Further, the start time t start of the specified time period is the 10th millisecond after the air supply starts, and the end time t end of the specified time period is the 40th millisecond after the air supply starts.

[0100] The setting of this time window is not arbitrary, but is based on a deep understanding of the fluid dynamics and system response characteristics of the solder paste supplementing process.

[0101] In the working process, from the opening of the gas pressure supply system to the start of the tin paste flowing driven by the gas to overcome the static friction force, there is a short gas pressure establishment stage. The starting point of the detection window is set at the 10th millisecond after the gas supply starts, the purpose is to avoid the pressure impact and initial unstable flow field that may be generated by the opening moment of the electromagnetic valve in the gas pressure supply system, to ensure that the signal-to-noise ratio of the collected gas pressure data is high, and the compression process of the gas in the tank can be truly reflected. The termination point of the window is strictly limited to the 40th millisecond, in order to ensure that the detection must be completed before the tin paste starts to flow significantly.

[0102] Once the tin paste starts to flow, the complex viscous characteristics of the tin paste as a non-Newtonian fluid will introduce a large number of interference factors that are difficult to model and compensate, which will seriously destroy the clear and stable one-to-one correspondence between the gas pressure change and the gas volume. Therefore, this detection window accurate to the millisecond can successfully simplify the complex problem into a controllable model, directly ensuring the feasibility of the detection principle and the reliability of the results. Thus it ensures the singularity and stability of the causal relationship between the detection signal (gas pressure establishment rate) and the target parameter (gas volume / tin paste remaining amount), and lays a solid foundation for high-precision detection.

[0103] Optionally, the pressure sensor is connected to the control system through an industrial field bus, and the data acquisition period of the control system is less than or equal to 1 millisecond.

[0104] In this embodiment, the control system is also used for:

[0105] S40: Control the tin supplement time: according to the calculated current tin paste remaining amount, determine the total tin supplement time t required to maintain stable paste output 总 .

[0106] In specific implementation, after completing the calculation of the current tin paste remaining amount, the control system will immediately start the tin supplement time control logic. The core decision mechanism is: since the reduction of the tin paste remaining amount will lead to the decrease of the paste output pressure in the same gas supplement time, it is necessary to dynamically adjust the tin supplement gas supply time according to the current remaining amount. For example, when it is detected that the remaining amount is low (such as less than 50%), the system will automatically prolong the opening time of the gas pressure supply system of this tin supplement operation, that is, the total tin supplement time t 总 , more gas is injected to compensate for the slow pressure establishment caused by the increase of the gas cavity, so as to ensure that the volume of the tin paste extruded each time is basically constant. This dynamic compensation mechanism directly improves the consistency of the tin paste printing process and the product quality. It effectively solves the industry pain point of gradually reduced printing amount caused by tin paste consumption, avoids the welding defects caused thereby, realizes the "precise" printing in the true sense, and greatly improves the intelligent level and process guarantee capability of the measurable tin paste remaining amount printing machine.

[0107] The implementation of S40 realizes the deep integration and synchronous operation of the tin paste residue detection and the tin supplement operation link, without interrupting the production process.

[0108] Further, S40 comprises:

[0109] When the tin paste residue is at the maximum value, the tin supplement time required for the paste output to reach the specified value is taken as the reference air supply time t0;

[0110] According to the calculated current tin paste residue, and based on the pre-stored corresponding relationship between the tin paste residue and the time compensation value, the time compensation value t corresponding to the current tin paste residue is obtained 补 ; wherein the tin paste residue and the time compensation value t 补 are in a negative correlation relationship;

[0111] The total tin supplement time t corresponding to the current tin paste residue is calculated 总 = reference air supply time t0+ time compensation value t 补 , and the air pressure supply system is controlled to start and stop according to the total tin supplement time t 总 so that the paste output of each tin supplement remains consistent.

[0112] The specific working process is as follows: first, the system presets a "reference air supply time t0", which usually corresponds to the best air supply time required to reach the target paste output when the tin paste tank is full (residue 100%). This t0 is a basic value. Then, the control system will query a pre-stored "tin paste residue-time compensation value" corresponding relationship table or curve function according to the real-time calculated current tin paste residue, and retrieve the corresponding "time compensation value t 补 ". The corresponding relationship is designed to be "tin paste residue and the time compensation value t 补 " in a negative correlation, that is, the less the residue, the larger the time t 补 compensation required. Finally, the system adds the reference time and the compensation time (t 总 = t0+ t 补 ), obtains the total tin supplement time actually executed this time, and accurately controls the start and stop of the air pressure supply system accordingly. Thus, a complex dynamic control problem can be decomposed into a stable basic value and a predictable compensation amount, with clear logic, convenient parameter setting, and very easy to implement in the controller, further ensuring the accuracy of control and the stability of the system.

[0113] Further, the control system is further used for:

[0114] Reference time calibration: after a new tin paste tank is loaded each time, a complete tin supplement triggering, data acquisition, and residue calculation step is performed, and the calculated tin paste residue value this time is calibrated as the maximum value of the tin paste residue of the tin paste tank.

[0115] In each time the operator loads a new, full solder paste tank, the control system can automatically or by user instruction trigger a "reference time calibration" process. This process will perform a complete refill, detection cycle: i.e. control the air supply system to supply air, get air pressure data within the specified time period, and calculate the current solder paste remaining amount based on this data. Since this is a new tank loaded, the system can force the value of the calculated remaining amount to be "maximum" (such as 100%), and use it as the reference zero point for all subsequent remaining amount calculation and refill time compensation. At the same time, the air supply time required to make the paste output meet the standard under the full tank state can also be updated as the new "reference air supply time t0". This embodiment gives the device the ability of self-learning and self-calibration, effectively eliminates the system error caused by changing consumables (solder paste tank), ensures the accuracy and reliability of long-term use, reduces the dependence on manual calibration, and reflects the high intelligence and user-friendly of the device.

[0116] Optionally, the control system is further configured to generate and output a warning signal if the current solder paste remaining amount is lower than a preset threshold.

[0117] In specific implementation, the control system will continuously compare the calculated current solder paste remaining amount with one or more preset thresholds (for example, the remaining amount is lower than 15%). Once the remaining amount is lower than the threshold, the system will immediately generate a warning signal and output clear warning information to the operator through various forms such as human-machine interface (such as touch screen), indicator light, sound alarm or upper production management system interface, prompting the need to prepare to replace the solder paste tank. This realizes the forward-looking avoidance of production interruption, gives the operator sufficient preparation time, and thus ensures the continuous and stable operation of the production line, avoids the batch waste caused by sudden lack of paste during printing, and has significant value for improving overall equipment efficiency (OEE).

[0118] Optionally, the control system is further configured to receive user input of solder paste tank and / or solder paste model selection instructions, and call the corresponding relationship matched with the selected solder paste tank and / or solder paste model for remaining amount calculation.

[0119] This function is a key intelligent feature designed by the present application to adapt to the flexible production requirements of modern SMT production lines. Different types of solder paste (such as different metal content, different alloy powder particle size, and different flux formula) have significant differences in rheological properties, specifically in viscosity and yield stress parameters. These differences will directly affect the ease of solder paste flow under the same air pressure conditions and the resistance during the flow process, resulting in different air pressure establishment characteristic values even under the same solder paste residual amount and detection conditions. In addition to adapting to different solder paste types, the control system can also receive user input of solder paste tank type instructions, call the corresponding relationship matching the specific tank structure parameters for residual amount calculation. This function enables the device to flexibly adapt to different volume and internal size of solder paste tanks, greatly improving the versatility and device compatibility of the scheme.

[0120] To solve this problem, the control system is configured to have the ability to receive user input and adaptively switch parameters. In specific implementation, the software interface of the control system provides a solder paste type selection menu, in which several common or supported solder paste types are pre-set. When the operator changes the solder paste type according to the current production task, the corresponding solder paste type selection instruction is input through the human-machine interface (HMI).

[0121] After receiving the instruction, the control system immediately calls the "corresponding relationship" uniquely matched with the specific solder paste type from its internal memory, which can be a database obtained through experimental calibration or a physical model obtained through theoretical derivation.

[0122] Subsequently, in all subsequent residual amount detection calculations, the system will use the parameter set matched with the selected solder paste type for operation until the user changes the type instruction again.

[0123] The beneficial effects of this embodiment are extremely prominent. It greatly improves the versatility and application range of the measurable solder paste residual amount printer, enabling a device to accurately adapt to multiple solder paste materials, avoiding the trouble of detection inaccuracy or the need for complex recalibration due to the change of solder paste type. This not only ensures the consistency of detection accuracy when switching different products, but also greatly simplifies the operation process, improves production efficiency and the intelligent level of the device, and is an important support for realizing the concepts of "flexible manufacturing" and "one-key line switching".

[0124] In this embodiment, two specific implementation directions are provided for S30:

[0125] I. Implementation Direction One: Obtaining Solder Paste Residual Amount Based on Air Pressure Change Characteristic Value

[0126] Optionally, S30 includes the following steps:

[0127] S3011: determining a gas pressure change characteristic value according to the gas pressure data;

[0128] S3012: obtaining the current solder paste residual amount based on a pre-stored correspondence between the gas pressure change characteristic value and the solder paste residual amount;

[0129] The gas pressure change characteristic value is the gas pressure rise value of the top cavity within the specified time period or the pressure rise rate These two parameters are direct and effective indicators of the speed of gas pressure establishment.

[0130] During operation, after capturing the gas pressure raw data within the specified time period, the control system first calculates the gas pressure change characteristic value in real time through simple subtraction operation (final pressure minus initial pressure) or differential operation. Then, the real-time gas pressure change characteristic value calculated is compared and interpolated with the "gas pressure change characteristic value-solder paste residual amount" standard curve or database pre-stored in the control system, so that the current solder paste residual amount can be quickly and accurately deduced. This method converts the complex physical modeling problem into a robust table lookup problem, greatly reducing the dependence on system parameter accuracy, improving the reliability and real-time performance of detection, and is particularly suitable for deployment and operation in industrial control environment.

[0131] In this embodiment, the pre-stored correspondence between the gas pressure change characteristic value and the solder paste residual amount has the following two acquisition methods

[0132] (1) Method one: without considering temperature influence

[0133] Specifically, the pre-stored correspondence between the gas pressure change characteristic value and the solder paste residual amount is obtained through the following calibration process:

[0134] While the solder paste tank is in a plurality of different known solder paste residual amounts, the gas supply system is controlled to supply gas to the top cavity at a plurality of gas supply flow rates;

[0135] Within the specified time period of each gas supply, the gas pressure data is obtained through the pressure sensor to calculate the gas pressure change characteristic value;

[0136] According to the plurality of gas supply flow rates, the plurality of known solder paste residual amounts, and the calculated gas pressure change characteristic values, a first database is made to represent the correspondence among the gas supply flow rate, the solder paste residual amount, and the gas pressure change characteristic value.

[0137] This calibration process is essentially a system learning and self-modeling behavior.

[0138] In practice, a series of supervised learning experiments need to be conducted in the laboratory or production site for the specific model of the tin paste tank and the gas pressure supply system. First, the tin paste tank is artificially set to multiple known and different tin paste residual states (e.g., full tank 100%, half tank 50%, low residual 20%, etc.). In each residual state, the gas pressure supply system is controlled to supply gas to the tank at multiple different gas flow rates (e.g., high, medium, and low). During each gas supply process, the control system records the data of the pressure sensor within the specified time period and calculates the corresponding gas pressure change characteristic value (such as the gas pressure rise value ΔP). Finally, all experimental data, i.e., different gas flow rates, known tin paste residuals, and their corresponding gas pressure change characteristic values, are associated to construct a multi-dimensional lookup table (i.e., the first database) and permanently burned into the non-volatile memory of the control system.

[0139] The embodiment has the beneficial effect that, through the pre-system calibration, the influence of the physical parameters that are difficult to accurately measure in real time in actual work of the device (such as small fluctuations in gas flow rate, differences in tin paste viscosity, etc.) is all absorbed and solidified in the empirical relationship of the first database. This makes it unnecessary to pay attention to these complex and variable intermediate parameters during actual detection, and high-precision residual results can be obtained directly by looking up the table, significantly improving the engineering applicability and anti-interference ability of the method.

[0140] (2) Method two: directly considering the influence of temperature on tin paste residual

[0141] Optionally, the tin paste residual printing machine further comprises a temperature sensor 6 in communication connection with the control system, for monitoring the gas supply temperature of the compressed gas in the top cavity;

[0142] At this time, the pre-stored corresponding relationship between the gas pressure change characteristic value and the tin paste residual is obtained through the following calibration process:

[0143] ① For different gas supply temperatures, control the gas pressure supply system to supply gas to the top cavity at multiple gas flow rates when the tin paste tank is in multiple different known tin paste residual states;

[0144] ② During the specified time period of each gas supply, the gas pressure change characteristic value is calculated by acquiring the gas pressure data through the pressure sensor;

[0145] ③ According to multiple gas supply temperatures, multiple gas flow rates, multiple known tin paste residuals, and the calculated gas pressure change characteristic values, a second database is made to represent the corresponding relationship between the gas supply temperature, the gas flow rate, the tin paste residual, and the gas pressure change characteristic value.

[0146] In the present calibration process, a temperature compensation dimension is introduced on the basis of Method One, which is an important optimization measure for the change of industrial field environment. Specifically, all the calibration steps described in Method One need to be repeated at multiple different environmental temperatures (for example, 15°C, 25°C, 35°C). This is because temperature changes will significantly affect the physical properties of the gas (such as density, viscosity) and the rheological properties of the solder paste itself, resulting in a drift in the measured gas pressure change characteristic value even at the same gas supply flow rate and solder paste residual amount. By performing multi-dimensional calibration, a more accurate and robust second database can be established, which clearly represents the complex mapping relationship between the gas supply temperature, gas supply flow rate, solder paste residual amount, and gas pressure change characteristic value.

[0147] In the actual detection phase, after calculating the real-time gas pressure change characteristic value, the control system synchronously reads the current gas supply temperature measured by the temperature sensor, and then queries the second database based on these two variables to obtain a more accurate solder paste residual amount after temperature correction. The beneficial effect of this implementation is that it greatly improves the long-term stability and measurement accuracy of the detection system under all-weather and different seasonal working conditions, avoids false alarms or detection failures caused by environmental temperature fluctuations, and makes the present application scheme reliable for industrial applications.

[0148] It should be noted that when using Method One to obtain the corresponding relationship between the pre-stored gas pressure change characteristic value and the solder paste residual amount, the following steps can be added between step S301 and step S302:

[0149] S3011a: Obtain the corresponding relationship between the gas supply temperature and the gas pressure change characteristic value through experimental calibration;

[0150] S3011b: Obtain the corrected gas pressure change characteristic value based on the pre-stored corresponding relationship between the gas supply temperature and the gas pressure change characteristic value according to the calculated gas pressure change characteristic value.

[0151] That is, the calculated gas pressure change characteristic value is first corrected in combination with the corresponding relationship between the gas supply temperature and the gas pressure change characteristic value, and then the gas pressure change characteristic value considering the correction of the gas supply temperature is substituted into the first database to obtain the solder paste residual amount considering the influence of the gas supply temperature, which can also reduce the adverse effects caused by changes in the gas supply temperature.

[0152] II. Implementation Direction Two: Obtaining Solder Paste Residual Amount Based on Physical Model

[0153] In this implementation direction, S30 includes the following steps:

[0154] S3021: Calculate the gas volume V above the piston according to the physical model (1) g:

[0155] (1);

[0156] S3022: Calculate the current tin paste remaining amount V according to the physical model (2) s :

[0157] (2);

[0158] wherein,

[0159] V total is the internal volume of the tin paste tank after removing the piston, V g is the gas volume above the piston, V s is the tin paste volume below the piston, used to characterize the tin paste remaining amount;

[0160] k is the adiabatic index, R is the gas constant, and T is the gas temperature above the piston;

[0161] A e is the gas flow cross-sectional area when the gas pressure supply system outputs compressed gas (which can be the valve port area of the electromagnetic valve or the nozzle outlet area of the gas pressure supply system, etc.);

[0162] pz is the gas pressure data monitored by the pressure sensor;

[0163] p u is the set output gas pressure of the gas pressure supply system;

[0164] t start is the start time of the specified time period, t end is the end time of the specified time period.

[0165] Example 2

[0166] This embodiment aims to formula derivation and explanation of the physical model (1) in Example 1.

[0167] This derivation process aims to establish a quantitative relationship between the gas volume V g in the cavity at the top of the tin paste tank and the measurable parameters, and the theoretical foundation is the ideal gas state equation and the critical flow (choke flow) principle in compressible fluid mechanics.

[0168] Step 1: Establish the basic equation of the dynamic process

[0169] Start with the ideal gas state equation: P V = n R T (A)

[0170] wherein:

[0171] P: gas pressure;

[0172] V: gas volume;

[0173] n: number of moles of gas;

[0174] R: ideal gas constant;

[0175] T: thermodynamic temperature;

[0176] In the initial very short time of the tinning process (e.g., t < 30 ms), it is reasonable to assume that:

[0177] 1. The process is isothermal (temperature T is constant).

[0178] 2. The solder paste has not yet flowed, so the volume occupied by the gas Vg remains constant.

[0179] Differentiate both sides of the equation of state (1) with respect to time t: d(P V) / dt = d(n R T) / dt;

[0180] Since V and T are constant, the above equation simplifies to:

[0181] Vg * (dpz / dt) = R T * (dn / dt) (B);

[0182] Where:

[0183] dpz / dt: rate of change of pressure pz in the solder paste tank with respect to time (i.e., the rate of pressure rise ).

[0184] dn / dt: number of moles of gas flowing into the gas cavity per unit time, i.e., the molar flow rate.

[0185] Step 2: Introduce the critical flow condition to determine the molar flow rate

[0186] In a pneumatic system, when the flow velocity reaches the speed of sound at the nozzle or valve, critical flow (or choked flow) occurs. In this state, the mass flow rateṁ (unit: kg / s) reaches a maximum value and is determined only by the upstream pressure pu, regardless of the downstream pressure pz. Its formula is:

[0187] ṁ= Ae * pu * √[ k / (R T) * (2 / (k+1))^((k+1) / (k-1)) ] (C)

[0188] Where:

[0189] Ae: effective flow area of the nozzle;

[0190] pu: upstream pressure (output pressure of the gas supply system);

[0191] k: adiabatic index of the gas (for air, k ~ 1.4);

[0192] The relation between the molar flow dn / dt and the mass flow ṁ is: dn / dt = ṁ / M; where M is the molar mass of the gas. Substituting equation (C) and combining the constant terms, we get the expression for the molar flow:

[0193] dn / dt = C * Ae * pu (D);

[0194] where C is a combined constant:

[0195] C = (1 / M) * √[ k / (R T) * (2 / (k+1))^((k+1) / (k-1)) ].

[0196] Step three: Simultaneous equations and integration

[0197] Substitute the molar flow equation (D) into the dynamic equation (B): Vg * (dpz / dt) = R T * (C * Ae * pu);

[0198] Combine the constant terms, let K = R T * C * Ae, then the equation simplifies to:

[0199] dpz / dt = (K / Vg) * pu (E);

[0200] Now, integrate both sides of equation (E) over a specified time period, from t start to t end :

[0201] ;

[0202] The left side integrates to the rise in gas pressure in the tin can from t start to t end . If measured in bar and the initial pressure p z (t start ) is 0 (or taken as a reference), then the left side equals p z (the pressure at time t end ).

[0203] In the right side integration, K / V g is a constant, is the upstream pressure p u integrated over time from t start to t end .

[0204] Thus, after integration, we get: pz = (K / Vg) * ;

[0205] Rearranging the above equation, we solve for the gas volume Vg:

[0206] Vg = (K / p z ) * (F);

[0207] Step four: Get the final form

[0208] Expand the constant K back to its definition: K = R T * Ae * C = R T * Ae * (1 / M) * √[ k / (R T)* (2 / (k+1))^((k+1) / (k-1)) ];

[0209] After combining and simplifying, we get:

[0210] K = Ae * √[ k^3 *R T * (2 / (k+1))^((k+1) / (k-1)) ];

[0211] Vg = (K / p z ) * = (1)。

[0212] This derivation starts from the basic physical laws, by introducing the critical flow as a key condition, establishes the direct mathematical relationship between the gas volume V g and the measurable physical quantity (the upstream pressure p u integral over time). The formula theoretically proves the feasibility of detecting the solder paste residue using the inherent parameters of the system.

[0213] Finally, it needs to be noted that although the above embodiments have been described in the specification and drawings of the present application, this does not limit the scope of patent protection of the present application. Any equivalent structure or equivalent process substitution or modification based on the essential concept of the present application, using the content described in the specification and drawings, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are all included in the scope of patent protection of the present application.

Claims

1. A solder paste balance measuring printing machine, characterized in that, include: Solder paste container, with an internal piston that can move up and down, the lower cavity of the piston is used to hold solder paste; A pneumatic supply system is connected to the top of the solder paste container and is used to inject compressed gas into the top cavity above the piston; A pressure sensor, connected to the solder paste container via the air pressure supply system, is used to monitor the air pressure data of the top cavity; The delivery pipeline connects the bottom outlet of the solder paste container to the area above the stencil; The control system is communicatively connected to both the air pressure supply system and the pressure sensor, and is used for: When solder paste needs to be replenished, the air pressure supply system is controlled to start injecting compressed gas into the top cavity; During a specified time period after the air pressure supply system starts supplying air and before the solder paste begins to flow out of the solder paste container, air pressure data is acquired by the pressure sensor. Based on the air pressure data, obtain the current solder paste balance.

2. The measurable solder paste balance printing machine according to claim 1, characterized in that, Based on the air pressure data, the current solder paste balance is obtained, including the following steps: Determine a pressure change characteristic value based on the pressure data; Based on the pre-stored correspondence between air pressure change characteristic values ​​and solder paste balance, the current solder paste balance is obtained; The characteristic value of the air pressure change is the increase in air pressure of the gas in the top cavity within the specified time period. or boost rate .

3. The solder paste balance measuring printer according to claim 2, characterized in that, The correspondence between the pre-stored air pressure change characteristic value and the solder paste balance is obtained through the following calibration process: With the solder paste container in multiple different known solder paste balance states, the air pressure supply system is controlled to supply air to the top cavity at multiple air flow rates. During the specified time period of each gas supply, the pressure data acquired by the pressure sensor is used to calculate the characteristic value of the pressure change. Based on multiple air supply flow rates, multiple known solder paste balances, and the calculated characteristic values ​​of air pressure changes, a first database is created to characterize the correspondence between air supply flow rate, solder paste balance, and characteristic values ​​of air pressure changes.

4. The solder paste balance measuring printer according to claim 2, characterized in that, It also includes a temperature sensor that is communicatively connected to the control system for monitoring the supply temperature of the compressed gas in the top cavity; The correspondence between the pre-stored air pressure change characteristic value and the solder paste balance is obtained through the following calibration process: For different gas supply temperatures, when the solder paste container is in multiple different known solder paste balance states, the gas supply system is controlled to supply gas to the top cavity at multiple gas flow rates; During the specified time period of each gas supply, the pressure data acquired by the pressure sensor is used to calculate the characteristic value of the pressure change. Based on multiple gas supply temperatures, multiple gas supply flow rates, multiple known solder paste balances, and the calculated characteristic values ​​of gas pressure changes, a second database is created to characterize the correspondence between the four factors: gas supply temperature, gas supply flow rate, solder paste balance, and characteristic values ​​of gas pressure changes.

5. The measurable solder paste balance printing machine according to claim 1, characterized in that, Based on the air pressure data, the current solder paste balance is obtained, including the following steps: Calculate the gas volume V above the piston based on the physical model (1). g : （1）； Calculate the current solder paste balance V based on the physical model (2). s : （2）； in, V total V is the internal volume of the solder paste container after removing the piston. g V is the gas volume above the piston. s The volume of solder paste below the piston is used to characterize the remaining amount of solder paste. k is the adiabatic index, R is the gas constant, and T is the gas temperature above the piston; A e The cross-sectional area of ​​the gas flow when the gas supply system outputs compressed gas; pz is the air pressure data monitored by the pressure sensor; p u The set output air pressure of the air supply system; t start t is the start time of the specified time period. end The end time of the specified time period.

6. The measurable solder paste balance printing machine according to claim 1, characterized in that, The start time t of the specified time period start The specified time period t is the 10th millisecond after the start of gas supply. end This is the 40th millisecond after gas supply begins.

7. The measurable solder paste balance printing machine according to claim 1, characterized in that, The control system is also used for: Controlling solder replenishment time: Based on the calculated current solder paste balance, determine the total solder replenishment time t required to maintain a stable solder paste output. 总 .

8. The solder paste balance measuring printer as described in claim 7, characterized in that, Based on the calculated current solder paste balance, determine the total solder replenishment time t required to maintain a stable solder paste output. 总 ,include: The time required to replenish solder paste to reach the specified amount when the solder paste balance is at its maximum value is taken as the reference air supply time t0. Based on the calculated current solder paste balance and the pre-stored correspondence between solder paste balance and time compensation value, obtain the time compensation value t corresponding to the current solder paste balance. 补 Wherein, the solder paste balance and the time compensation value t 补 There is a negative correlation; Calculate the total resoldering time t corresponding to the current solder paste balance. 总 =Base gas supply time t0 + Time compensation value t 补 And according to the total solder replenishment time t 总 Control the start and stop of the air pressure supply system to ensure that the amount of solder paste dispensed each time is consistent.

9. The measurable solder paste balance printing machine as described in claim 8, characterized in that, The control system is also used for: Reference time calibration: After each new solder paste container is filled, a complete set of steps is performed to trigger solder replenishment, acquire data, and calculate the remaining amount. The calculated remaining amount of solder paste is then calibrated as the maximum remaining amount of solder paste in this container.

10. The measurable solder paste balance printing machine according to claim 1, characterized in that, The control system is also used for: If the current solder paste balance is lower than a preset threshold, a warning signal is generated and output.

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