Digital pulse ultra-low spatter gas shielded MIG welding system and control method

Abstract

The application discloses a control method of a digital pulse ultra-low spatter gas protection MIG welding system, and comprises the following operation steps: S1, a self-checking step; S2, a process parameter calling step; S3, a pre-delivery gas step; S4, a wire drawing and arc striking step, wherein a wire feeding motor is controlled by a DSP digital main control board to reversely draw back the welding wire at a speed of 1-5 m / min by 3-15 mm, then the wire feeding motor is controlled by the DSP digital main control board to forwardly feed the wire at a high speed of 8-20 m / min, and after the welding wire is in contact with the workpiece and is short-circuited, an arc is ignited under an arc striking current of 20-80 A; S5, an NTS ultra-low spatter waveform control welding step; S6, an arc signal dynamic correction step, wherein during the welding process, the DSP digital main control board dynamically adjusts the PWM output duty ratio through a PID closed loop algorithm according to the real-time collected arc voltage and current signals, corrects the current waveform, and maintains the arc stability; and S7, a receiving arc step. The application has the advantages of reducing CO2 welding spatter, providing a welding current range and high load, and meeting the welding of various working conditions.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a digital pulsed ultra-low spatter gas-protected MIG welding system and control method. Background Technology

[0002] Arc welding, as one of the most widely used fusion welding methods in industrial production, plays an irreplaceable role in industries such as steel structure manufacturing, shipbuilding, pressure vessels, petrochemical pipelines, automobile manufacturing, and construction machinery. With the manufacturing industry's increasing demands for welding quality, production efficiency, and environmental protection, the requirements for welding equipment are gradually rising.

[0003] Currently, arc welding itself has inherent limitations in its applications; 1. Welding spatter using pure carbon dioxide gas cannot be completely eliminated. The short-circuit transition principle determines that the bursting of molten droplets will produce metal spatter, and the workpiece surface needs to be ground and cleaned, which increases the time and consumables of grinding wheels; even in digital models, spatter will still be produced in thin plates with low current and intermittent spot welding, which can only be improved by relying on argon gas mixture, which increases the cost of gas.

[0004] 2. Welding thin plates is difficult to control. The lower limit of current for conventional models is too high, making it easy to burn through thin steel plates less than 1.5mm thick; the arc is too soft for low current, making it easy to break the arc and stick to the conductive nozzle. The pulse model can improve this, but the equipment is more expensive.

[0005] 3. Shortcomings in wire feeding technology Cable length limits welding distance. With a single-wire drive wire feeder, if the welding torch cable exceeds 5 meters, the wire feeding will become stuck or intermittent due to pipe bends or twists in the wiring. For long-distance operations, a dual-drive wire feeder assembly must be selected, which increases equipment investment. Consumable parts are frequently worn, including contact tips, distributors, nozzles, and wire feed hoses, which are routine consumables. Copper powder from the welding wire accumulates inside the hose, causing wire blockage over time, requiring regular disassembly and cleaning. The selection of welding wire has a low tolerance for error; changes in wire thickness require readjustment of the arc inductance parameters. Bending or uneven coating of the welding wire directly lead to wire skipping and unstable arcs. Moisture and rust in stored spools of welding wire directly cause poor welding.

[0006] 4. Carbon dioxide cylinders freeze at low temperatures. When the temperature is low, the pressure reducing valve of the cylinder is prone to freezing and blocking the gas outlet. A gas heater must be installed, and additional accessories are required. The gas supply pipeline is cumbersome, the gas cylinders take up space, the pipeline layout is messy, and the 5S management and control of the workshop is difficult; aging pipelines leak gas, and production costs increase over time. The purchase price of mixed gas is much higher than that of ordinary carbon dioxide.

[0007] 5. Current Status and Shortcomings of Digital Control Technology While existing digital welding machines have improved welding performance to some extent, they still lack the ability to precisely segment and control the entire droplet transfer process, and cannot implement effective current pre-control within the millisecond timescale of short circuit occurrence; their multi-material adaptability is poor, ordinary single-pulse welding machines are only suitable for carbon steel welding and cannot stably weld non-ferrous metals such as aluminum, while dedicated aluminum welding machines cannot meet the low spatter welding requirements of carbon steel and stainless steel; power protection is inadequate, lacking comprehensive RC absorption protection and large-capacity bus filtering, and IGBT modules are easily broken down by switching spikes during high-power welding.

[0008] Currently, a patent with publication number "CN202398926U" discloses a digital welding machine control device with good welding waveform, which prevents spatter by timely detection of welding status and control of output current. However, this solution only uses basic current detection and PWM control, lacking the ability to perform fine segmented control over the entire droplet transfer process, and still has significant shortcomings in multi-material adaptation, grid voltage fluctuation compensation, and power device protection. Summary of the Invention

[0009] The purpose of this invention is to provide a digital pulsed ultra-low spatter gas-protected MIG welding system and control method, which has the advantages of reducing CO2 welding spatter, providing a wide range of welding currents and high loads, and meeting the welding needs of various working conditions.

[0010] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system includes the following operation steps: S1. Power-on self-test procedure; S2. Process parameter retrieval steps: Select the welding process mode and call the JOB process program through the operation display panel to retrieve the corresponding process's pre-stored waveform parameters and control parameters. S3, Pre-gas delivery procedure; S4. Wire drawing and arc ignition steps: The DSP digital main control board controls the wire feeding motor to first reverse the wire by 3-15mm at a speed of 1-5m / min, and then feed the wire forward at a high speed of 8-20m / min. After the wire contacts the workpiece and short-circuits, the arc is ignited under an arc ignition current of 20-80A. The S5 and NTS ultra-low spatter waveform control welding steps, after entering stable welding, the DSP digital main control board acquires welding current and arc voltage signals in real time with a sampling period of 100μs to 500μs, and executes NTS four-segment current control: During the short-circuit prediction stage, when the droplet is about to short-circuit based on the current change rate di / dt, the welding current is rapidly reduced from the welding set value I_set to the first current value I1 with a first slope of 50 to 200 A / ms. I1 is 15% to 30% of I_set. During the short-circuit current limiting phase, the welding current is further reduced and maintained at the second current value I2, where I2 is 10% to 20% of I_set; During the liquid bridge transition phase, the welding current is increased back to the third current value I3 with a second slope, where I3 is 60% to 80% of I_set; During the arc recovery phase, the welding current is restored to the welding set value I_set with the third slope to re-establish a stable arc state; The four stages cycle continuously within a single droplet transition period, achieving smooth droplet transition and ultra-low spatter welding. S6. Arc signal dynamic correction step: During the welding process, the DSP digital main control board dynamically adjusts the PWM output duty cycle according to the real-time collected arc voltage and current signals, corrects the current waveform, and maintains arc stability through a PID closed-loop algorithm. S7, Arc Closure Step.

[0011] The preferred option is as follows: Preferred: In step S1, After the device is powered on, the DSP digital main control board performs system initialization, performs self-tests on the power circuit, drive circuit, sampling circuit, wire feed encoder and communication interface, and enters standby mode after confirming that each module is working normally.

[0012] Preferred: In step S2, When the HD-Pulse high-speed pulse welding mode is selected, the waveform parameters retrieved by the DSP digital main control board are as follows: Pulse peak current 300~600A, pulse width 1~3ms, pulse base current 50~150A, pulse frequency 50~500Hz; During the peak pulse phase, the droplet transition is maintained to provide sufficient penetration depth. During the base pulse phase, the arc is stabilized and the heat input is controlled. A narrow and short arc is used to achieve high-speed welding of thin plates without burn-through, as well as root welding of large-gap workpieces with single-sided welding and double-sided forming.

[0013] Preferred: In step S3, When the welding torch trigger is pulled, the DSP digital main control board first controls the solenoid valve to open, delivering protective gas to the welding area at a set flow rate. The pre-gas delivery time is 0.3 to 2.0 seconds, which purges the air from inside the welding torch.

[0014] Preferred: In step S4, The process of drawing wire and initiating an arc involves the following five steps. S41, Reverse retraction step: The DSP digital main control board controls the wire feeding motor to reverse retract the welding wire by 3-15mm at a speed of 1-5m / min, so that the end of the welding wire is separated from the previous welding break point. S42. After the reverse retraction is completed, the DSP digital main control board immediately controls the wire feeding motor to feed the wire forward at a speed of 8-20 m / min, and the welding wire quickly approaches the surface of the workpiece. S43. Contact short-circuit arc ignition step: After the welding wire comes into contact with the workpiece, a short-circuit loop is formed. The arc ignition current is in the range of 20 to 80A. The short-circuit current rises rapidly, the end of the welding wire is heated and melted, and an electric arc is established under the combined action of electromagnetic contraction force and electrothermal force. S44. Arc ignition confirmation step: After the arc is established, the DSP digital main control board detects that the arc voltage rises to the range of 10-30V, determines that the arc ignition is successful, and switches to normal welding control mode. S45, Arc ignition failure retry step: If no arc voltage is detected within the preset arc ignition time, the arc ignition is determined to have failed. The DSP digital main control board will automatically return to step S41 to re-execute the wire drawing and arc ignition. The maximum number of retries is 3. If all three retries fail, an arc fault alarm will be displayed on the operation display panel and the inverter output will be blocked.

[0015] Preferred: In step S5, It also includes a dual-drive wire feeding closed-loop control sub-step. The encoder detects the actual speed of the wire feeding motor in real time and transmits it to the DSP digital main control board. The DSP digital main control board compares the set wire feeding speed with the actual wire feeding speed and calculates the correction amount of the PWM duty cycle of the wire feeding motor drive through the PID controller. When the wire feeding speed deviation is detected to exceed ±3% of the set value, the wire feeding force level is automatically adjusted. The adaptive adjustment is performed within the range of 20 wire feeding force levels to ensure stable wire feeding under long wire feeding tubes and multiple bends.

[0016] Preferred: In step S7, After releasing the welding torch trigger, the DSP digital main control board controls the wire feeding motor to stop feeding the wire, outputs the arc-extinguishing buffer current to melt the metal ball at the end of the welding wire, and then closes the protective gas solenoid valve after a delay to complete the arc-extinguishing process.

[0017] Preferably, it also includes temperature monitoring and power protection steps. The DSP digital main control board reads the temperature signal of the heat sink substrate collected by the temperature sensor in real time. When the temperature of the heat sink reaches 65℃, the speed of the heat sink fan is increased to full speed. When the temperature of the heat sink reaches 85°C, the cut-off protection is activated, blocking the IGBT drive signal, cutting off the welding power output, and displaying over-temperature alarm information on the operation display panel.

[0018] Preferably, it also includes welding data management steps. During the welding process, the DSP digital main control board uploads real-time welding current, arc voltage, welding duration, and fault code data to the host computer system or cloud server through the multi-protocol industrial communication interface module. The host computer system uses the collected data to trace the entire welding process, evaluate production performance, and count equipment uptime. It also pushes reminders to replace vulnerable parts based on the cumulative welding time to achieve preventative maintenance.

[0019] A digital pulsed ultra-low spatter gas-shielded MIG welding system, comprising, The input power supply module includes a three-phase input air switch, a three-phase rectifier bridge module, and a bus electrolytic capacitor bank; The three-phase input air switch is used to connect to a 380V three-phase AC power supply; The three-phase rectifier bridge module has its AC input terminal connected to the output terminal of the three-phase input air switch via a copper busbar, which rectifies the three-phase AC power into high-voltage DC power. The bus electrolytic capacitor bank is connected to the DC output terminal of the three-phase rectifier bridge module for bus filtering and energy storage, and is connected in parallel with a resistor-capacitor absorption plate to suppress bus voltage spikes. The core inverter power module includes an IGBT power inverter module, a main inverter transformer, a secondary fast recovery rectifier diode module, and a DC filter reactor; The IGBT power inverter module has its DC bus input terminal connected to the bus electrolytic capacitor bank, and converts DC power into medium frequency AC power under the control of the drive signal. The primary side of the main inverter transformer is connected to the intermediate frequency AC output terminal of the IGBT power inverter module, which steps down the intermediate frequency AC power into low-voltage, high-current intermediate frequency AC power. The input terminal of the secondary fast recovery rectifier diode module is connected to the secondary side of the main inverter transformer through a copper busbar, which rectifies the intermediate frequency AC power into welding DC power. The DC filter reactor has its input terminal connected to the positive output of the secondary fast recovery rectifier diode module, which is used to smooth the current ripple of the welding DC power and suppress short-circuit inrush current. The digital control module includes a DSP digital main control board, a driver board, an operation display panel, and a current sampling Hall transformer; The DSP digital main control board outputs a PWM drive signal to the IGBT power inverter module through the driver board; The operation display panel is connected to the DSP digital main control board via a ribbon cable; The current sampling Hall transformer has its signal output terminal connected to the DSP digital main control board, which is used to collect welding current signals in real time to form a digital current closed loop. The DSP digital main control board stores the NTS ultra-low splash waveform control program.

[0020] The preferred option is as follows: Preferred: The NTS ultra-low splash waveform control program adopts a four-segment current control strategy, which divides each droplet transition cycle into a short-circuit prediction stage, a short-circuit current limiting stage, a liquid bridge transition stage, and an arc recovery stage; The welding current is acquired in real time by the current sampling Hall transformer with a sampling period of 100μs to 500μs, and the PWM duty cycle is dynamically corrected with a current control accuracy of ±2A.

[0021] Preferred configuration: The DSP digital main control board has a built-in unified expert parameter database and a JOB process program storage module; By operating the display panel, you only need to set the welding current and plate thickness parameters. The DSP digital main control board automatically matches the corresponding arc voltage, wire feed speed, pulse parameters and waveform control parameters according to the pre-stored unified expert parameter database. The JOB process program storage module supports storing multiple sets of welding process recipes, allowing for one-click recall of the corresponding process parameters when changing products.

[0022] In summary, the present invention has the following beneficial effects: 1. Through a four-stage current control setting, the current is actively reduced before the molten droplet short circuit, the energy is limited during the short circuit, the recovery rate is controlled during the liquid bridge transition, and the arc is stably rebuilt during the arc recovery. CO2 pure gas welding spatter is reduced by about 85%, which can significantly reduce the grinding process and grinding wheel consumables, the workpiece surface is clean, no additional cleaning is required before painting, and the labor cost is reduced. 2. By setting the short arc mode, the heat input is precisely controllable, supporting root welding, single-sided welding, double-sided forming, and deep arc welding. It can achieve the effect of welding thin plates (0.8-1.5mm) without burning through, reducing the amount of beveling for thick plates, producing uniform fish scale pattern in the weld, improving the flaw detection pass rate, and reducing the need for rework. 3. By setting the reverse wire drawing logic for arc initiation, it can stably initiate arcs even with long cables, mobile conditions, and coiled cables, with an arc initiation success rate of nearly 100%. When the arc is terminated, it automatically fills the arc crater, eliminates shrinkage cavities, and prevents sticking to the conductive tip, thus reducing wear on the conductive tip and nozzle. 4. Through the setting of fully digital DSP precise waveform control and unified adjustment, the fully digital waveform control combined with the unified parameter adjustment function can achieve the effect of not having to manually readjust the inductor parameters when changing the welding wire diameter or welding conditions, shortening the changeover and debugging time from tens of minutes to a few minutes, and greatly improving the efficiency of flexible production. 5. With the dual-drive high-precision wire feeding setting, it can achieve encoder feedback closed-loop control with 20 levels of adjustable wire feeding force, and the wire feeding speed deviation is controlled within ±3%. The wire feeding is stable and does not slip under long wire feeding tubes and multi-bend working conditions, reducing wire consumption and significantly reducing weld defects. 6. Through the setting of power protection and heat dissipation system, the triple protection of RC absorption plate, bus electrolytic capacitor group and DC filter reactor can effectively suppress IGBT switching spikes, smooth current ripple, buffer short circuit inrush current, and the independent air duct design is suitable for high temperature workshops and dusty construction sites. The three-level temperature protection ensures the safe and stable operation of the equipment. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments.

[0024] Example 1: A digital pulsed ultra-low spatter gas-protected MIG welding system, comprising an input power supply module, an inverter power core module, and a digital control module.

[0025] Input power supply module: It includes a three-phase input air switch, a three-phase rectifier bridge module, and a bus electrolytic capacitor bank.

[0026] Three-phase input air switch with overload and short circuit protection functions, used for connecting to 380V three-phase 50Hz AC power supply; The three-phase rectifier bridge module adopts a three-phase full-bridge rectifier circuit. Its AC input terminal is connected to the output terminal of the three-phase input air switch through a copper busbar, which rectifies the 380V three-phase AC power into approximately 540V pulsating high-voltage DC power. The bus electrolytic capacitor bank, located between the three-phase rectifier bridge module and the IGBT power inverter module, consists of multiple 450V / 680μF electrolytic capacitors connected in parallel, with a total capacity of not less than 4700μF, and is used for bus filtering and energy storage. A resistor-capacitor (RC) absorption plate is also connected in parallel on the bus electrolytic capacitor bank. The RC absorption plate includes a series branch of resistor and capacitor, which is used to absorb the voltage spikes generated by the IGBT power inverter module during high-speed switching, protect the IGBT device from being broken down, and ensure the stability of the bus voltage.

[0027] Inverter power core module: Includes IGBT power inverter module, main inverter transformer, secondary fast recovery rectifier diode module and DC filter reactor; The IGBT power inverter module is vertically fixed to the front of a large aluminum heat sink, equipped with thermal grease, and adopts a full-bridge inverter topology. Its DC bus input terminal is connected to the bus electrolytic capacitor bank. Under the control of the PWM drive signal of the DSP digital main control board, it inverts 540V high-voltage DC power into 20kHz~50kHz medium-frequency square wave AC power. In this embodiment, the inverter frequency is set to 25kHz, the inverter efficiency reaches 76.0%, and the no-load loss is low, which is significantly more energy-saving than the old-fashioned power frequency welding machine. The main inverter transformer uses nanocrystalline iron core material. Its primary side is connected to the intermediate frequency AC output terminal of the IGBT power inverter module to step down the intermediate frequency AC power into low-voltage, high-current intermediate frequency AC power. The input terminal of the secondary fast recovery rectifier diode module is connected to the secondary side of the main inverter transformer through a copper busbar, which performs high-frequency rectification on the medium-frequency low-voltage high-current AC and outputs welding DC power. The DC filter reactor uses 5×16 copper bars wound with 6.5 turns and has an inductance of 10μH to 100μH. Its input terminal is connected to the positive output of the secondary fast recovery rectifier diode module. It is used to smooth the current ripple of the welding DC power supply and suppress the short-circuit inrush current to ensure the stability of the welding arc.

[0028] Digital control module: Includes a DSP digital main control board, a driver board, an operation display panel, and a current sampling Hall transformer; The DSP digital main control board uses a TITMS320F28335 digital signal processor with a main frequency of 150MHz and an ADC sampling rate of 200kSPS. The DSP digital main control board outputs PWM drive signals to the IGBT power inverter module through the driver board. The driver board achieves strong and weak electrical signal isolation through optocoupler isolation and amplifies the PWM waveform output by the DSP to drive the IGBT gate. The operation display panel uses a 5.7-inch color LCD touch screen, which is connected to the DSP digital main control board through a ribbon cable to realize parameter adjustment, JOB program storage and fault code display. The current sampling Hall current transformer is set on the negative output cable of the DC filter reactor. It adopts a closed-loop Hall current sensor with a range of 0 to 600A. Its signal output terminal is connected to the current sampling port of the DSP digital main control board to collect welding current signals in real time and form a digital closed loop of current. The DSP digital main control board stores the NTS ultra-low splash waveform control program. The NTS ultra-low splash waveform control program adopts a four-segment current control strategy, which divides each droplet transition cycle into a short-circuit prediction stage, a short-circuit current limiting stage, a liquid bridge transition stage, and an arc recovery stage. Welding current is collected in real time by a current sampling Hall transformer with a sampling period of 100μs to 500μs, and the PWM duty cycle is dynamically corrected with a current control accuracy of ±2A to achieve fine segmented control of the entire droplet transfer process. The DSP digital main control board has a built-in unified expert parameter database and a JOB process program storage module. The unified expert parameter database covers three materials: carbon steel, stainless steel, and aluminum. Each material covers three welding wire diameters: 1.0mm, 1.2mm, and 1.6mm. Each combination has a pre-stored parameter mapping table covering the full range from minimum to maximum current. By simply setting the welding current and plate thickness parameters through the operation display panel, the DSP digital main control board automatically matches the corresponding arc voltage, wire feed speed, pulse parameters, and waveform control parameters based on the pre-stored unified expert parameter database, eliminating the need for manual readjustment of inductor parameters. The JOB process program storage module supports storing no fewer than 100 sets of welding process recipes. Each recipe includes a complete set of settings such as material type, welding wire specification, welding current, arc voltage, welding mode, pulse parameters, and arc termination parameters. When changing products, the corresponding process parameters can be recalled with a single click.

[0029] The input power supply module effectively suppresses IGBT switching spikes through a resistor-capacitor absorption plate; the inverter power core module adopts a medium-frequency inverter topology, which has high inverter efficiency and small size; the digital control module uses DSP as the core to realize fully digital waveform control, and with the unified adjustment function, the changeover and debugging time is shortened from tens of minutes to a few minutes.

[0030] Example 2: A control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system. This embodiment takes the NTS ultra-low spatter welding of a thin carbon steel plate with a thickness of 2mm as an example. S1. Power-on self-test procedure. After the device is powered on, the DSP digital main control board performs system initialization, and performs self-tests on the power circuit, drive circuit, sampling circuit, wire feed encoder and communication interface. Specifically, when the three-phase input air switch is closed, 380V three-phase AC power is input to the three-phase rectifier bridge module through the air switch, and rectified into approximately 540V DC power, charging the bus electrolytic capacitor bank to a stable voltage; The auxiliary power driver board starts working, outputting DC24V, DC15V, and DC5V power supplies. After the DSP digital main control board is powered on, it executes a system self-test program to sequentially test the working status of the IGBT drive circuit, the arc sampling circuit, the wire feeder communication interface, and the multi-protocol communication interface. After the self-test is passed, the operation display panel shows the ready screen and the device enters standby mode. S2. Procedure for retrieving process parameters Operators can select welding process modes and call up JOB process programs through the operation display panel, and retrieve the corresponding pre-stored waveform parameters and control parameters. In this embodiment, The operator selects the NTS ultra-low spatter welding mode, selects the welding wire specification ER50-6 with a diameter of 1.0mm, and sets the welding current to 120A and the plate thickness to 2mm. The DSP digital main control board automatically retrieves the pre-stored waveform parameters and control parameters of the NTS process from the unified expert parameter database, including the arc voltage of 18.5V, wire feed speed of 6.5m / min, NTS four-segment control parameters and other complete welding parameters, without the need for operators to manually set them one by one. S3, Pre-air supply procedure. When the welding torch trigger is pulled, the DSP digital main control board first controls the solenoid valve to open, delivering CO2 shielding gas to the welding area at a set flow rate of 15L / min. The pre-gas delivery time is 0.5 seconds, which purges the air inside the welding torch, ensuring sufficient shielding atmosphere at the moment of arc initiation and preventing porosity in the weld. S4, the wire drawing and arc initiation steps. The DSP digital main control board controls the wire feeding motor to first reverse the wire by 5mm at a speed of 2m / min to eliminate residual metal balls at the end of the wire. Then, the wire is fed forward at a high speed of 12 m / min, and the welding wire quickly approaches the surface of the workpiece along the welding gun hose. After the welding wire comes into contact with the workpiece, a short circuit is formed. Under the arc ignition current of 30A, the short circuit current rises rapidly. The end of the welding wire is rapidly heated and melted under the combined action of resistance heat and arc heat. A stable plasma arc is established under the combined action of electromagnetic contraction force and electrothermal force. The DSP digital main control board detects that the arc voltage has risen from close to 0V to 18V, determines that the arc ignition is successful, and immediately switches to normal welding control mode. S5 and NTS ultra-low spatter waveform control welding steps After entering stable welding, the DSP digital main control board collects welding current and arc voltage signals in real time at a sampling rate of 200kHz and a sampling period of 5μs, and executes NTS four-segment current control with welding set value I_set=120A. During the short-circuit prediction stage, the DSP digital main control board collects the welding current in real time at a sampling rate of 200kHz. When the rate of change of current di / dt exceeds the set threshold, it is determined that the molten droplet is about to short-circuit with the molten pool. At the first slope of 100A / ms, the welding current is rapidly reduced from I_set=120A to the first current value I1=24A, which is 20% of I_set. The key to this stage is to release the electromagnetic force between the molten droplet and the molten pool in advance, so that the molten droplet begins to transition to the molten pool under the action of a smaller force. During the short-circuit current limiting stage, after the molten droplet actually contacts the molten pool and short-circuits, the DSP digital main control board further reduces the welding current and maintains it at the second current value I2=18A, 15% of I_set, with the short-circuit current limiting duration being 150μs. During this time, the short-circuit energy is controlled at the lowest level, and the liquid metal bridge will not burst due to excessive electromagnetic force, thus fundamentally eliminating the mechanical conditions caused by spatter. During the liquid bridge transition phase, after the short-circuit current limiting is maintained, the DSP digital main control board gradually increases the welding current from I2=18A to the third current value I3=84A, which is 70% of I_set, at a second slope of 80A / ms. At the I3 current level, the surface tension and electromagnetic contraction force work together to smoothly pull the liquid metal bridge into the molten pool, completing the liquid bridge transition. During the arc recovery phase, after the liquid bridge has fully transitioned, the DSP digital control board restores the welding current from I3=84A to the welding setpoint I_set=120A at a third slope of 150A / ms, re-establishing a stable arc state. The entire recovery process takes approximately 0.24ms. The above four stages cycle continuously for 8–12 ms within one droplet transfer cycle, repeating dozens to hundreds of times per second. Actual measurements show that using this NTS four-stage control method reduces CO2 pure gas welding spatter by approximately 85% compared to traditional welding machines, resulting in a smooth and flat weld surface that requires almost no subsequent grinding. S6. Dynamic correction steps for electric arc signal During welding, the DSP digital main control board dynamically adjusts the PWM output duty cycle based on the real-time collected arc voltage and current signals using a PID closed-loop algorithm (Kp=2.5, Ki=0.15, Kd=0.02) to correct the current waveform and maintain a stable output current of 120A±2A, achieving a current control accuracy of ±2A. When changes in arc length, cable voltage drop, or grid voltage fluctuations occur, the DSP digital main control board corrects the output power within milliseconds to maintain arc stability. S7, Arc-closing steps. After the operator releases the welding torch trigger, the DSP digital main control board controls the wire feeding motor to stop feeding wire, outputs an arc-extinguishing buffer current of 80A for 0.5s to melt the metal ball at the end of the welding wire, the wire feeding motor stops running after a 2s delay to replenish the arc crater filling, the electromagnetic gas valve continuously supplies gas for 3s to isolate the high-temperature weld seam from the air, and finally blocks the IGBT drive PWM signal, the inverter stops, the arc is extinguished, and one welding cycle is completed. After the cooling fan continues to run for 30 seconds to remove the residual heat, it runs at low speed and the equipment returns to standby mode. After welding, the weld surface was smooth and flat, the spatter was reduced by about 85% compared with ordinary CO2 welding machines, the fish scale pattern of the weld was uniform, and the flaw detection pass rate reached the first-class weld standard.

[0031] Example 3: Wire drawing and arc initiation control This embodiment uses ER50-6 solid welding wire with a diameter of 1.2mm and a welding current of 180A as an example. The wire drawing and arc initiation process includes the following five steps: S41, Reverse pullback step. The DSP digital main control board controls the wire feeding motor of the dual-drive wire feeding assembly to reverse and retract the welding wire at a speed of 3m / min, with a retraction length of 8mm, so that the end of the welding wire is separated from the previous welding break point, eliminating metal balls and residual adhesion at the end of the welding wire, and ensuring a clean arc starting point. S42, Forward high-speed wire feeding step. After the reverse retraction is completed, the DSP digital main control board immediately controls the wire feeding motor to feed the wire forward at a speed of 15m / min, and the welding wire quickly approaches the workpiece surface along the welding gun hose; High-speed wire feeding ensures reliable contact short circuits, making it particularly suitable for long cables exceeding 7m and mobile applications; S43. Contact short circuit arc ignition procedure. After the welding wire comes into contact with the workpiece, a short circuit is formed. The arc ignition current is controlled at 50A. The short circuit current rises rapidly. The end of the welding wire is rapidly heated and melted under the combined action of resistance heat and arc heat. Under the combined action of electromagnetic contraction force and electrothermal force, a stable plasma arc is established between the end of the welding wire and the workpiece. S44. Arc triggering confirmation procedure. After the arc is established, the DSP digital main control board detects that the arc voltage rises from close to 0V to 18V, determines that the arc ignition is successful, and immediately switches to the NTS ultra-low spatter waveform control welding mode. S45, Retry Procedure for Failed Arc Attempt If the arc voltage is not detected to rise above 10V within the preset arc ignition time, the arc ignition is determined to have failed, and the DSP digital main control board will automatically return to step S41 to re-execute the wire drawing and arc ignition. The maximum number of retries is 3. If all 3 retries fail, the DSP digital main control board will block the IGBT drive signal and display an arc ignition fault alarm message on the operation display panel, prompting the operator to check whether the welding wire is broken, whether the wire feeding pipeline is blocked, or whether the workpiece surface is severely corroded.

[0032] This embodiment eliminates residual metal balls at the end of the welding wire by reverse retraction, ensuring a clean arc ignition point; forward high-speed wire feeding ensures reliable contact and short circuit; it is suitable for scenarios where arc ignition is difficult, such as long cables, mobile working conditions, and coiled cables; the retry mechanism greatly improves the arc ignition success rate, which is close to 100%; when the arc is terminated, it automatically fills the arc crater, with no shrinkage cavities and no sticking to the conductive tip, reducing the wear of the conductive tip and nozzle.

[0033] Example 4: HD-Pulse high-speed pulse welding mode Taking the welding of 1.0mm carbon steel sheet as an example, the operator selects the HD-Pulse high-speed pulse welding mode through the operation display panel; The waveform parameters retrieved by the DSP digital main control board are: peak pulse current 400A, pulse width 2ms, base pulse current 80A, pulse frequency 200Hz, current rising edge slope 300A / ms, and current falling edge slope 300A / ms.

[0034] During the peak pulse phase, at 400A for 2ms, the arc exhibits a droplet transfer mode, with the tip of the welding wire transitioning to the molten pool at high speed as small molten droplets, providing sufficient penetration depth. During the base pulse phase, the arc maintains a narrow, short, conical shape, the heat input is significantly reduced, the molten pool cools moderately but the arc does not extinguish. Due to the pulse frequency of up to 200Hz, 200 pulse cycles are completed per second, and the arc shape exhibits stable high-frequency pulsating characteristics.

[0035] HD-Pulse high-speed pulse welding mode achieves high-speed welding of thin plates up to 1.0mm without burn-through through a narrow and short arc, with precise and controllable heat input; the weld has a uniform and beautiful fish-scale pattern, improving the pass rate of flaw detection; it has strong adaptability to large-gap workpieces, and root welding can achieve single-sided welding and double-sided forming; the pulse peak stage maintains droplet transition to provide sufficient penetration depth, and the pulse base stage maintains arc stability and controls the amount of heat input.

[0036] It should be noted that the pulse parameters of HD-Pulse mode are as follows: peak pulse current 300-600A, pulse width 1-3ms, base pulse current 50-150A, and pulse frequency 50-500Hz. The DSP digital main control board automatically matches the optimal pulse parameter combination from a unified expert parameter database based on the plate thickness and welding current set by the operator.

[0037] Example 5: Dual-drive wire feeding closed-loop control During the NTS ultra-low spatter waveform control welding process in step S5, the dual-drive wire feeding assembly of the welding system works simultaneously. The dual-drive wire feeding assembly includes two wire feeding motors that drive the active wire feeding wheel and the driven wire feeding wheel respectively. An encoder is installed on the shaft end of the wire feeding motor to detect the actual speed of the wire feeding motor in real time.

[0038] The encoder transmits the actual rotation speed signal to the DSP digital main control board in real time. The DSP digital main control board compares the set wire feeding speed with the actual wire feeding speed and calculates the correction amount of the PWM duty cycle of the wire feeding motor drive through the PID controller. When the wire feeding speed deviation is detected to exceed ±3% of the set value, the DSP digital main control board automatically adjusts the wire feeding force level and performs adaptive adjustment within the range of 20 wire feeding force levels. Specifically, when the wire feeding speed is too low, the DSP digital main control board automatically increases the PWM duty cycle of the wire feeding motor drive to improve the wire feeding force level; when the wire feeding speed is too high, the wire feeding force level is reduced to ensure that the wire feeding speed deviation is always controlled within ±3%.

[0039] The dual-drive wire feeding closed-loop control features encoder feedback closed-loop control with 20 levels of adjustable wire feeding force, keeping the wire feeding speed deviation within ±3%. It ensures stable wire feeding without slippage even in long wire feeding tubes and multi-bend conditions. It reduces wire loss and significantly decreases weld defects. It is adaptable to welding wires of different diameters and materials, eliminating the need for manual adjustment of the wire feeding force.

[0040] Example 6: Temperature monitoring and power protection The DSP digital main control board reads the temperature signal of the heat sink substrate collected by the temperature sensor in real time. The temperature sensor is installed on the IGBT heat sink base and uses an NTC thermistor to detect the heat sink temperature in real time.

[0041] When the temperature of the heat sink substrate reaches the first temperature threshold of 65℃, the DSP digital main control board controls the speed of the heat sink fan to increase to full speed, increase the heat dissipation air volume, and prevent the power devices from overheating. The heat sink fan is located at the air outlet at the upper rear of the chassis, forming a directional independent air duct for all the power devices on the heat sink. An insulating partition is provided between the power device area and the weak current control area to achieve strong and weak current isolation. When the temperature of the heat sink substrate reaches the second temperature threshold of 85℃, the DSP digital main control board performs cut-off protection: blocking the drive signal of the IGBT power inverter module, cutting off the welding power output, and at the same time displaying the "over-temperature alarm" information on the operation display panel, prompting the operator to check whether the heat dissipation air duct is blocked, whether the ambient temperature is too high, or whether the welding load exceeds the rated range of the equipment. When the temperature of the heat sink substrate drops below 60°C, the DSP digital main control board automatically deactivates the over-temperature protection, the equipment returns to standby mode, and the operator can resume the soldering operation.

[0042] In this embodiment, temperature monitoring and power protection are implemented by having the cooling fan operate at low speed within the normal temperature range. The fan runs at full speed when the temperature reaches 65℃. Power output is cut off when the temperature reaches 85℃.

[0043] Ensure that the equipment operates safely and stably in harsh environments such as high-temperature workshops and dusty construction sites.

[0044] Example 7: Welding Data Management During the welding process, the DSP digital main control board uploads real-time welding current, arc voltage, welding time, fault codes and other data to the host computer system or cloud server through the multi-protocol industrial communication interface module.

[0045] The multi-protocol industrial communication interface module supports PROFINET, EtherCAT, DeviceNet and RS485 interfaces, allowing for flexible selection of the docking method based on the communication protocol of the field automation system.

[0046] The host computer system performs the following functions based on the collected data: The entire welding process is traceable, recording the actual welding parameter waveforms of each product. It supports searching historical welding data by product number, production date, and operator, meeting the requirements for quality traceability and factory audit. Production performance evaluation involves compiling statistics on the daily / weekly / monthly welding time, pass rate, and equipment utilization rate for each welding machine and each operator, and generating production performance reports. Equipment utilization rate statistics calculate the utilization rate of each welding machine, the actual welding time / planned working time, and the overall equipment efficiency (OEE) to provide data support for production scheduling and equipment procurement. Preventive maintenance involves the host computer system automatically calculating the remaining lifespan of vulnerable parts based on the cumulative welding time of each welding machine. When the cumulative usage of the contact tip reaches a set threshold of 200 hours, a replacement reminder is automatically sent. When the cumulative usage of the wire feeding hose reaches a set threshold of 500 hours, a cleaning or replacement reminder is sent. Preventive maintenance reduces welding quality problems and unplanned downtime caused by the aging of vulnerable parts.

[0047] Record the cumulative welding time of each welding machine, the actual current and voltage waveform data of each welding operation, the abnormal fault codes and their occurrence time, to achieve complete recording and intelligent management of welding process data.

[0048] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system, characterized in that, The following steps are included: S1. Power-on self-test procedure; S2. Process parameter retrieval steps: Select the welding process mode and call the JOB process program through the operation display panel to retrieve the corresponding process's pre-stored waveform parameters and control parameters. S3, Pre-gas delivery procedure; S4. Wire drawing and arc ignition steps: The DSP digital main control board controls the wire feeding motor to first reverse the wire by 3-15mm at a speed of 1-5m / min, and then feed the wire forward at a high speed of 8-20m / min. After the wire contacts the workpiece and short-circuits, the arc is ignited under an arc ignition current of 20-80A. The S5 and NTS ultra-low spatter waveform control welding steps, after entering stable welding, the DSP digital main control board acquires welding current and arc voltage signals in real time with a sampling period of 100μs to 500μs, and executes NTS four-segment current control: During the short-circuit prediction stage, when the droplet is about to short-circuit based on the current change rate di / dt, the welding current is rapidly reduced from the welding set value I_set to the first current value I1 with a first slope of 50 to 200 A / ms. I1 is 15% to 30% of I_set. During the short-circuit current limiting phase, the welding current is further reduced and maintained at the second current value I2, where I2 is 10% to 20% of I_set; During the liquid bridge transition phase, the welding current is increased back to the third current value I3 with a second slope, where I3 is 60% to 80% of I_set; During the arc recovery phase, the welding current is restored to the welding set value I_set with the third slope to re-establish a stable arc state; The four stages cycle continuously within a single droplet transition period, achieving smooth droplet transition and ultra-low spatter welding. S6. Arc signal dynamic correction step: During the welding process, the DSP digital main control board dynamically adjusts the PWM output duty cycle according to the real-time collected arc voltage and current signals, corrects the current waveform, and maintains arc stability through a PID closed-loop algorithm. S7, Arc Closure Step.

2. The control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 1, characterized in that: In step S1, After the device is powered on, the DSP digital main control board performs system initialization, performs self-tests on the power circuit, drive circuit, sampling circuit, wire feed encoder and communication interface, and enters standby mode after confirming that each module is working normally.

3. The control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 2, characterized in that: In step S2, When the HD-Pulse high-speed pulse welding mode is selected, the waveform parameters retrieved by the DSP digital main control board are as follows: Pulse peak current 300~600A, pulse width 1~3ms, pulse base current 50~150A, pulse frequency 50~500Hz; During the peak pulse phase, the droplet transition is maintained to provide sufficient penetration depth. During the base pulse phase, the arc is stabilized and the heat input is controlled. A narrow and short arc is used to achieve high-speed welding of thin plates without burn-through, as well as root welding of large-gap workpieces with single-sided welding and double-sided forming.

4. The control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 3, characterized in that: In step S3, When the welding torch trigger is pulled, the DSP digital main control board first controls the solenoid valve to open, delivering protective gas to the welding area at a set flow rate. The pre-gas delivery time is 0.3 to 2.0 seconds, which purges the air from inside the welding torch.

5. The control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 4, characterized in that: In step S4, The process of drawing wire and initiating an arc involves the following five steps. S41, Reverse retraction step: The DSP digital main control board controls the wire feeding motor to reverse retract the welding wire by 3-15mm at a speed of 1-5m / min, so that the end of the welding wire is separated from the previous welding break point. S42. After the reverse retraction is completed, the DSP digital main control board immediately controls the wire feeding motor to feed the wire forward at a speed of 8-20 m / min, and the welding wire quickly approaches the surface of the workpiece. S43. Contact short-circuit arc ignition step: After the welding wire comes into contact with the workpiece, a short-circuit loop is formed. The arc ignition current is in the range of 20 to 80A. The short-circuit current rises rapidly, the end of the welding wire is heated and melted, and an electric arc is established under the combined action of electromagnetic contraction force and electrothermal force. S44. Arc ignition confirmation step: After the arc is established, the DSP digital main control board detects that the arc voltage rises to the range of 10-30V, determines that the arc ignition is successful, and switches to normal welding control mode. S45, Arc ignition failure retry step: If no arc voltage is detected within the preset arc ignition time, the arc ignition is determined to have failed. The DSP digital main control board will automatically return to step S41 to re-execute the wire drawing and arc ignition. The maximum number of retries is 3. If all three retries fail, an arc fault alarm will be displayed on the operation display panel and the inverter output will be blocked.

6. The control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 5, characterized in that: In step S5, It also includes a dual-drive wire feeding closed-loop control sub-step. The encoder detects the actual speed of the wire feeding motor in real time and transmits it to the DSP digital main control board. The DSP digital main control board compares the set wire feeding speed with the actual wire feeding speed and calculates the correction amount of the PWM duty cycle of the wire feeding motor drive through the PID controller. When the wire feeding speed deviation is detected to exceed ±3% of the set value, the wire feeding force level is automatically adjusted. The adaptive adjustment is performed within the range of 20 wire feeding force levels to ensure stable wire feeding under long wire feeding tubes and multiple bends.

7. The control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 6, characterized in that: In step S7, After releasing the welding torch trigger, the DSP digital main control board controls the wire feeding motor to stop feeding the wire, outputs the arc-extinguishing buffer current to melt the metal ball at the end of the welding wire, and then closes the protective gas solenoid valve after a delay to complete the arc-extinguishing process.

8. The control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 7, characterized in that: It also includes temperature monitoring and power protection procedures. The DSP digital main control board reads the temperature signal of the heat sink substrate collected by the temperature sensor in real time. When the temperature of the heat sink reaches 65℃, the speed of the heat sink fan is increased to full speed. When the temperature of the heat sink reaches 85°C, the cut-off protection is activated, blocking the IGBT drive signal, cutting off the welding power output, and displaying over-temperature alarm information on the operation display panel.

9. The control method for a digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 8, characterized in that: It also includes welding data management steps, During the welding process, the DSP digital main control board uploads real-time welding current, arc voltage, welding duration, and fault code data to the host computer system or cloud server through the multi-protocol industrial communication interface module. The host computer system uses the collected data to trace the entire welding process, evaluate production performance, and count equipment uptime. It also pushes reminders to replace vulnerable parts based on the cumulative welding time to achieve preventative maintenance.

10. A digital pulsed ultra-low spatter gas-shielded MIG welding system, used for the control method of the digital pulsed ultra-low spatter gas-shielded MIG welding system as described in claim 9, characterized in that: include, The input power supply module includes a three-phase input air switch, a three-phase rectifier bridge module, and a bus electrolytic capacitor bank; The three-phase input air switch is used to connect to a 380V three-phase AC power supply; The three-phase rectifier bridge module has its AC input terminal connected to the output terminal of the three-phase input air switch via a copper busbar, which rectifies the three-phase AC power into high-voltage DC power. The bus electrolytic capacitor bank is connected to the DC output terminal of the three-phase rectifier bridge module for bus filtering and energy storage, and is connected in parallel with a resistor-capacitor absorption plate to suppress bus voltage spikes. The core inverter power module includes an IGBT power inverter module, a main inverter transformer, a secondary fast recovery rectifier diode module, and a DC filter reactor; The IGBT power inverter module has its DC bus input terminal connected to the bus electrolytic capacitor bank, and converts DC power into medium frequency AC power under the control of the drive signal. The primary side of the main inverter transformer is connected to the intermediate frequency AC output terminal of the IGBT power inverter module, which steps down the intermediate frequency AC power into low-voltage, high-current intermediate frequency AC power. The input terminal of the secondary fast recovery rectifier diode module is connected to the secondary side of the main inverter transformer through a copper busbar, which rectifies the intermediate frequency AC power into welding DC power. The DC filter reactor has its input terminal connected to the positive output of the secondary fast recovery rectifier diode module, which is used to smooth the current ripple of the welding DC power and suppress short-circuit inrush current. The digital control module includes a DSP digital main control board, a driver board, an operation display panel, and a current sampling Hall transformer; The DSP digital main control board outputs a PWM drive signal to the IGBT power inverter module through the driver board; The operation display panel is connected to the DSP digital main control board via a ribbon cable; The current sampling Hall transformer has its signal output terminal connected to the DSP digital main control board, which is used to collect welding current signals in real time to form a current digital closed loop. The DSP digital main control board stores the NTS ultra-low splash waveform control program.

11. A digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 10, characterized in that: The NTS ultra-low spatter waveform control program adopts a four-stage current control strategy, which divides each droplet transition cycle into a short-circuit prediction stage, a short-circuit current limiting stage, a liquid bridge transition stage, and an arc recovery stage. The welding current is acquired in real time by the current sampling Hall transformer with a sampling period of 100μs to 500μs, and the PWM duty cycle is dynamically corrected with a current control accuracy of ±2A.

12. A digital pulsed ultra-low spatter gas-shielded MIG welding system according to claim 11, characterized in that: The DSP digital main control board has a built-in unified expert parameter database and a JOB process program storage module; By operating the display panel, you only need to set the welding current and plate thickness parameters. The DSP digital main control board automatically matches the corresponding arc voltage, wire feed speed, pulse parameters and waveform control parameters according to the pre-stored unified expert parameter database. The JOB process program storage module supports storing multiple sets of welding process recipes, allowing for one-click recall of the corresponding process parameters when changing products.