Wuxi Wondery Industry Equipment Co., Ltd

I. Project Background and Equipment Specifications This case study involves a fully automatic intelligent ion nitriding furnace, model WDL-IV-75A, employing a vertical single-bell-jar single-station structure. The equipment is capable of ion nitriding and soft ion nitriding of alloy steels, mold steels, and stainless steels. The effective working zone of the furnace body measures 600 mm in diameter and 800 mm in height, with a maximum loading capacity of 400 kg. The common operating temperature range is 500 to 600°C, with a maximum operating temperature not exceeding 650°C. The ultimate vacuum degree is no greater than 6.7 Pa, the pressure rise rate is no greater than 5 Pa/h, and the time required to evacuate from atmospheric pressure to ultimate vacuum does not exceed 30 minutes. The furnace shell surface temperature rise does not exceed 55°C. In the model designation, IV represents the fourth-generation digital control system, 75 represents the maximum average current of the pulse power supply at 75 amperes, and A represents the fully automatic intelligent type. II. Matching Relationship Between Large-Volume Chamber and Power Supply Capacity From the 30A model to the 75A model, the maximum average current of the pulse power supply increases by a factor of 1.5, while the effective chamber volume expands from approximately 28 liters to approximately 226 liters, a factor of about 8. This non-proportional change reveals a design principle of ion nitriding equipment: expansion of chamber volume does not require the power supply current to increase proportionally with volume, because the heating power for ion nitriding depends primarily on the workpiece surface area and the required current density, rather than the chamber spatial volume. The abnormal glow discharge current density range given in the proposal is 0.1 to 5 mA/cm². Based on this range, for a workpiece combination with a loading capacity of 400 kg and a relatively large surface area, the maximum average current of 75 A provides a clear design margin for the upper limit of supportable workpiece surface area. Meanwhile, the pulse power supply output voltage is continuously adjustable from 0 to 800 V with no sudden jump above 200 V, and the duty cycle is continuously adjustable within the range of 10% to 85%. III. Duty Cycle Adjustment Logic of the Pulse Power Supply Gas discharge, as a power source, presents a load with negative resistance characteristics. The workpiece, acting as the cathode, has its surface shape and stacking method both affecting the surface current density. Ion nitriding has a minimum threshold condition: to satisfy the current density required for uniform glow coverage, the heating power may exceed the power required to maintain workpiece temperature. This contradiction is particularly prominent for thin-walled, lightweight workpieces. After the pulse power supply introduces an adjustable duty cycle, the average heating power equals the peak voltage multiplied by current, then multiplied by the duty cycle. By reducing the duty cycle, the average heating power can be lowered while maintaining sufficient peak voltage to sustain glow coverage, thereby resolving the aforementioned contradiction. This mechanism is the core reason why this series of equipment can simultaneously process heavy workpieces and thin, lightweight workpieces. The implementation path for fast arc extinguishing is as follows: utilizing the principle of electromagnetic induction in the discharge circuit to rapidly detect the arcing signal, then immediately controlling the high-speed electronic switch of the main current circuit through high-speed digital logic devices, extinguishing the arc within 2 μs. IV. Thermal Insulation and Temperature Uniformity Design of the Large-Volume Furnace Body The bell cylinder adopts a water-cooled double-wall structure and multi-channel water cooling system to ensure furnace temperature uniformity. The inner insulating liner of the cylinder is made of stainless steel, while the inner and outer cylinder walls are made of high-quality carbon steel plates. The furnace body is equipped with two layers of 304 stainless steel heat shields, each layer 2 mm thick, and two layers of 304 stainless steel heat shields are also installed on the upper part of the furnace bottom plate. Compared with the six-layer heat shield configuration of the previous case, this model has fewer heat shield layers. This difference stems from the change in the ratio of chamber volume to surface area – a large-volume chamber has a relatively smaller heat dissipation area, and the heat loss proportion decreases accordingly, so the number of insulating layers can be appropriately reduced while ensuring long-term high-temperature operation. The cathode plate is supported on the furnace base by three sets of high-quality cast mica, with adjustable height. The cathode plate is made of carbon steel plate with a thickness of no less than 30 mm; the material tray fixture frame in contact with the workpiece is also made of high-quality carbon steel. The cathode connection device is designed as a rigid connection to avoid overheating problems caused by loose quick-connect couplings. The cathode structure includes cathode PTFE insulation, cathode insulating mica, cathode conductor connection socket, cathode connection fitting, and M10 stud bolt fixed connection cable lug. Two thermocouples are introduced from the furnace bottom plate and positioned in the middle of the cathode plate to simulate the temperature measuring head. One is used for temperature control by the ion heating pulse power supply, and the other is connected to the alarm instrument for multi-directional temperature monitoring. Three observation windows are arranged on the outer circumference of the furnace shell for multi-directional observation of conditions inside the furnace. V. Vacuum System and Pressure Closed-Loop Control The vacuum system is used for pre-vacuuming of the furnace body and for atmosphere replacement and exhaust gas discharge during the nitriding process. The pump set consists of one 2X-15 rotary vane pump, one electromagnetic vacuum pump with an inflation valve, and one high-vacuum butterfly valve. The rotary vane pump is a Guangdong Xunda 2X series unit, resistant to process gas corrosion, controlled by a frequency converter, and equipped with a GI-50 high-vacuum butterfly valve as the main control valve. The pressure closed-loop control principle is as follows: the pressure transmitter measures furnace pressure and outputs a standard current signal to the digital controller. The controller performs PID calculations based on the set pressure value and real-time sampled values, then outputs a standard current signal to the frequency converter. By adjusting the vacuum pump motor speed, the pumping speed is adjusted, thereby keeping the furnace pressure constant at the process set value. This control method achieves a pressure control accuracy of ±1 Pa. The combined use of the vacuum pump and frequency converter greatly reduces mechanical wear of the pump body during startup, and long-term low-speed operation can significantly extend service life. Vacuum measurement employs a ZJ-1C type capacitive diaphragm absolute pressure transmitter, with a range of 0 to 1000 Pa, output of 4 to 20 mA, and power supply of 15 to 30 VDC. This vacuum gauge is not affected by the type and composition of the measured medium, and the measured value is displayed by a digital display instrument and participates in furnace pressure control. VI. Gas Distribution and Cooling Water Systems The gas distribution system is used to control the introduction of process gas into the furnace. Gas sources include nitrogen, hydrogen, and other process gases, provided by the user. The gases pass through mass flow meters and are then introduced into the furnace body through a dedicated mixing tank according to the process formula. This model is equipped with two dedicated mass flow meters, controlling nitrogen and hydrogen flow separately – this is the main difference from the single flow meter configuration of the 30A model, corresponding to the higher requirements for atmosphere composition adjustment precision in a large-volume chamber. The mass flow meters are Japanese HORIBA S500 series units, with a response time of less than 0.3 ±2% seconds from fully closed state to reaching the setpoint when control begins and when the setpoint is changed during control. The control range covers 1 to 100% full scale, operating from a single universal DC24V power supply, with the internal power circuit isolated from input and output circuits. Cooling water requirements: inlet water temperature not exceeding 31°C, inlet water pressure of 0.15 to 0.25 MPa, and total flow rate of 20 m³/h. Each cooling water branch is equipped with separate inlet and outlet valves. All cooling water pipes, valves, and fittings attached to the equipment are made of stainless steel. An electrical contact pressure gauge is installed on the main inlet pipe for alarms in case of abnormal inlet pressure. A backup water inlet valve is installed at the main water inlet pipe, connected to the user's tap water pipe, so that the furnace body can be cooled by tap water in the event of an unexpected power outage or water outage. VII. Three-Parameter Closed-Loop Architecture of the Control System The control system uses an FX3G series programmable logic controller and a Kunlun Tongtai TPC1231Ni touch screen as the main control center. The PLC has a program memory capacity of 32K steps, a basic instruction processing speed of 0.21 μs, and two high-speed communication interfaces (RS422 and USB). The touch screen is a 12-inch TFT LCD with a resolution of 1920×1080, four-wire resistive touch, a main frequency of 1 GHz, and pre-installed McgsPro configuration software. The system adopts a multi-task centralized management and distributed control fully digital architecture, capable of simultaneously achieving closed-loop control of three key parameters in ion nitriding: temperature control accuracy of ±1°C, pressure control accuracy of ±1 Pa, and flow control accuracy of ±0.5%. Temperature control employs Japanese Shimaden SRS13 series digital controllers with PID regulation, forming a temperature closed-loop regulation system with the temperature control circuit and thermocouple. Pressure control also employs Shimaden SRS13 digital controllers, forming a pressure closed-loop regulation system with a frequency converter and pressure sensor. In automatic operation mode, the system automatically starts the maintaining pump and pre-evacuation pump, opens the baffle valve and solenoid valve to extract a vacuum. Once the vacuum reaches the working pressure for glow discharge activation, the glow discharge voltage and resistance-assisted heating are automatically activated to perform the initial workpiece arcing and cleaning process. After arcing ends, the system automatically enters the heating stage, automatically adjusting flow rate, pressure, voltage, duty cycle, and current according to the process curve design steps. When the temperature reaches the process temperature, the system enters the temperature maintenance stage, maintaining according to the set process holding time. After the holding period, the system shuts down the vacuum pump and all valves on the extraction pipeline. Once the furnace temperature drops to the set temperature, all switches automatically turn off, and the system enters a stop state.

I. Project Background and Equipment Application Positioning This case study involves a cart-type degreasing and carbonization furnace, model RT3-360-5, a cycle-operated furnace with a chamber working dimension of 6,000 mm in length, 2,000 mm in width, and 2,000 mm in height. The equipment serves two purposes: first, degreasing metal cylinders and pipes of different diameters; second, burning off rubber insulation and lining inside cylinders and pipes of varying diameters in carbonization processes. The common feature of these two processes is that the workpieces contain organic or polymer materials inside that need to be removed, and the combustion products must be discharged promptly. The workpieces themselves are elongated cylindrical structures, imposing relatively high requirements on furnace temperature uniformity. The rated temperature of the equipment is 500°C, with adjustable operating temperature. II. Main Technical Parameters and Power Configuration The rated power of the equipment is 500 kW, adjustable within a percentage range; rated voltage 380V, three-phase 50Hz. The full-load heating rate is adjustable from 20 to 80°C per hour, and the empty furnace heating time does not exceed 90 minutes. Furnace temperature uniformity during the holding stage does not exceed ±5°C. The temperature control instrument is a Japanese Shimaden SRS13A with an accuracy of no more than ±1°C. The temperature control method combines a touch screen human-machine interface with the Shimaden intelligent instrument and a power regulator for PID voltage regulation control. The heating elements are 0Cr25Al5 high-resistance alloy resistance strips produced by Shougang Group, processed into a waveform structure using a special mold, and arranged on five surfaces: both sides of the furnace, the furnace door, the rear wall, and the furnace bottom. The number of temperature control zones is set at 4, with each zone independently equipped with an ammeter, voltmeter, and on/off indicator for ease of fault localization. The furnace body insulation material is standard aluminum silicate refractory fiber cotton with a thickness of 240 mm. The furnace air guiding mechanism material is 304 stainless steel with a thickness of 2 mm. The furnace bottom plate material is CrMnN cast steel with a thickness of 30 mm, in strip form. III. Lining Structure and Energy-Saving Logic The lining uses standard aluminosilicate refractory fiber blankets, specially processed into large plate structures with a density of 230 kg/m³, finally assembled into a lining with a thickness of 240 mm. The fiber cotton modules are anchored to the steel structure of the furnace body using SUS304 stainless steel round bar anchors. The weight of an all-fiber lining is approximately one-thirtieth that of a refractory brick furnace body. The direct consequence of this weight difference is a substantial reduction in steel structure load. The comparison reference given in the proposal is that, under the same specifications, the all-fiber structure saves approximately 30% more energy than a brick-based resistance furnace. This figure is an engineering empirical value; actual energy savings depend on operating conditions such as furnace sealing condition, heating curve, and loading rate. All-fiber refractory structures have good thermal shock resistance, can withstand rapid heating and cooling, and have a longer service life than brick structures. IV. Heating Device and Suspension Structure The heating elements adopt an advanced suspension structure with high radiation efficiency, enhancing heat exchange within the furnace, improving furnace thermal efficiency, and extending heating element life. The resistance strips are processed from 0Cr25Al5 into a waveform structure, convenient for installation and maintenance. V. Furnace Door Structure and Sealing Mechanism The furnace door adopts a steel frame structure with refractory fiber as the heat insulation material, installed in the same manner as the furnace body. The furnace door is equipped with a 2-ton electric lifting mechanism, with the electric hoist installed above the furnace door gantry frame. The door lifting speed is 8 m/min. The furnace door sealing employs a cam mechanism for automatic clamping combined with a soft-edge sealing device, ensuring the door automatically seals against the furnace body. The function of this sealing mechanism is to guarantee furnace sealing throughout production, prevent the escape of high-temperature furnace gases, improve the working environment, and also ensure furnace temperature uniformity and enhance energy efficiency. This sealing device is simple in structure, safe, reliable, and easy to maintain, having been verified over years in the production of all-fiber cotton cart-type furnaces. Regarding safety protection, both upper and lower travel of the furnace door are equipped with double safety limit mechanisms, along with an interlocking device with the furnace car. Heating power is automatically cut off the moment the furnace door opens. Limit switches are Omron brand. VI. Trolley and Traction Mechanism The trolley consists of a frame, trolley furnace lining, furnace bottom plate, and trolley traction mechanism. The frame is welded from channel steel, with 10 mm side plates and 5 mm bottom plates (Q235), firmly and reliably constructed, not easily deformed or warped. The bottom insulation layer of the trolley furnace base consists of two layers of alternating diatomaceous earth bricks and lightweight straight bricks, while the refractory layer is constructed using heavy bricks. The trolley perimeter uses irregularly shaped bricks to prevent furnace gas from directly contacting the trolley side plates. The refractory layer on the trolley is constructed in a groove shape for placing heating elements, which also serves as a support for the furnace bottom plate. The furnace bottom plate is made of CrMnN cast steel with a total thickness of 30 mm, resting above the groove where heating elements are placed to prevent oxides from falling onto the heating elements after the workpiece is heated. The furnace bottom plate is equipped with a snap-fit design to prevent movement. The rear of the trolley is equipped with RT0 moving and stationary contacts for power connection, completing the power supply to the heating elements on the trolley. This contact method has a large and sufficient contact surface, good contact, and no electric sparks or overheating after long-term use. The traction device uses a frame structure for load-bearing and movement. The frame is mainly welded from 16 channel steel and steel plate. The wheels are forged from 45# steel with strong wear resistance. The drive is a motor plus a reducer, with an entry/exit speed of 6 to 8 m/min, driven by one motor. Both furnace entry and exit are equipped with double safety limit mechanisms and interlocking mechanisms – if the trolley does not reach the correct position, the furnace door cannot be opened or closed, and the entire furnace body cannot be powered. Synchronous geared motors make the trolley entry and exit flexible, stable, and accurately positioned. VII. Hot Air Circulation System To achieve uniform furnace temperature, 4 centrifugal circulating fans are installed at the top of the furnace along its length, each rated at 7.5 kW, 4-stage motors. The fan blades and shaft are made of 304 stainless steel. The fan is a one-piece design, with the motor rotor and fan shaft as a single unit, providing stable speed, low noise, and strong airflow. The furnace air guiding mechanism is made of heat-resistant SUS304 steel plate, with convection walls on both sides. Considering that the workpieces are plate-shaped or cylindrical, the hot air circulation direction is designed as horizontal – air flows horizontally from one side of the convection wall to the other, that is, air passes through the middle of each layer of workpieces. This airflow path ensures even heating and uniform temperature of the workpieces, further improving product performance.

I. Project Background and Capacity Matching Logic This case study involves an aluminum alloy induction heating production line, processing A6061 and 5083-H111 aluminum alloy bars with a diameter of Ø245 mm and a length of 500 mm, each weighing 68.406 kg. The capacity design derivation path is as follows: with a cycle time of 246 seconds per piece, dividing 3600 seconds by 246 seconds yields 14.634 pieces per hour; multiplying 14.634 pieces by the single-piece weight of 68.406 kg gives an output capacity of approximately 1,000 kg per hour. This calculation chain demonstrates that cycle time is the baseline parameter for the entire production line's power configuration, conveyor mechanism speed, and sorting logic – not an indicator that can be arbitrarily adjusted. The heating temperature requirement is 480 to 495°C, with a permissible deviation of ±15°C. The operating temperature range given in the equipment proposal is 460 to 480°C, showing a slight offset from the buyer's process requirement range. This difference typically requires calibration confirmation during the commissioning stage based on the actual forging process. II. Power Supply System Configuration The heating power supply employs a fully digital IGBT power supply, model IGBT300/0.15, with a rated power of 300 kW and a nominal frequency of 0.15 kHz, i.e., 150 Hz. The system power factor exceeds 0.9. The inverter combines fast thyristors with IGBT modules, with an input voltage of 380V and an output voltage of 1000V. The control program features automatic voltage regulation. Protective devices cover overcurrent, overvoltage, grounding, fast fuse, frequency abnormality, and cooling water abnormality conditions. The induction coil is made of copper tube with a purity of no less than 99.9% and a wall thickness of no less than 2.0 mm, using Luoyang Copper T2 oxygen-free cold-drawn copper tube. After winding, the coil undergoes acid washing, high-temperature insulating varnish impregnation, and resistance furnace baking to ensure good insulation, with withstand voltage (to ground) of no less than 5000V. The coil design life is no less than 8,000 hours. The furnace lining uses austenitic stainless steel tubing. III. Frequency Selection and Load Characteristics The nominal frequency of this equipment is 150 Hz, falling within the medium frequency induction heating range. In a parallel resonant load, once the values of inductance L and compensation capacitor are determined, the natural resonant frequency is also determined. As the load (inductor) impedance changes, the natural frequency also drifts – the frequency is lower when the furnace is empty or lightly loaded, and higher when the furnace is fully loaded with cold material. This load characteristic imposes requirements on the startup phase: the closer the startup frequency is to the actual load frequency, the higher the startup success rate. The frequency sweep startup method adopted in the proposal sends a set of frequencies covering the range of load frequency variation to start the equipment, unaffected by load changes, thereby improving startup reliability. The equipment uses automatic frequency tracking control during operation, requiring no manual adjustment; when used in different frequency bands, simply connecting the appropriate compensation capacitor bank adjusts to the suitable impedance value. IV. Cooling Water System Parameters The cooling water inlet temperature requirement is 5 to 35°C, outlet temperature below 55°C, and working pressure of 0.2 to 0.3 MPa. The cooling water flow rate for the power supply section is 7.5 m³/h, and for the furnace body section is 37.5 m³/h, with a total water requirement of 45 m³/h. The cooling method employs a closed-circuit cooling tower. The internal water circuit layout logic of the power cabinet merits separate explanation: all hoses are made of carbon-free rubber, and the water path length between components is maintained at at least 1.5 to 2 meters to avoid equipment instability caused by cross-contamination between components via the water path. Red pipes are used for return water (hot water) and blue pipes for inlet water (cold water), for rapid distinction of flow direction. The internal metal water tank uses 304 stainless steel for centralized water supply. Temperature sensors are installed on all branch pipes and numbered; when water temperature is abnormal, the control system alarms and displays the faulty water line number on the touchscreen. V. Mechanical Conveying and Sorting Mechanism Bars are neatly placed on the storage platform by hand. The turning mechanism turns the bars into the feed trough according to the heating rhythm. The feeding mechanism is a cylinder feeding system that feeds at a uniform speed according to the rhythm. The discharge end is equipped with a rapid discharge device composed of a water-cooled hexagonal shaft roller and conveyor chain, with sufficient force to prevent material from tipping over, and structural strength and high-temperature resistance meeting the needs of various material specifications in this project. The sorting mechanism is a three-part design that can quickly, accurately, and promptly separate low-temperature and high-temperature materials, conveying them to their respective bins via chutes. The initial forging temperature of forgings must be controlled between 480 and 495°C (the setting can be adjusted according to the customer's process). Forgings within this temperature range proceed to the next processing step; forgings below or above the forging temperature are sorted into different bins, with a sorting rate of 100%. VI. Temperature Measurement and Temperature Control A dedicated aluminum alloy temperature measuring instrument is installed at the furnace outlet of the inductor. A hole is made on the side of the furnace at a certain distance from the outlet, and a dedicated aluminum alloy temperature measuring instrument is installed to meet the temperature measurement needs of different working conditions. When the temperature difference of the measuring instrument is too large or the temperature is abnormal, an audible and visual alarm is triggered. The initial forging temperature can be displayed in real time on the human-machine interface and large screen display. Temperature measurement uses an infrared thermometer, equipped with temperature display and storage functions (storage period of 180 days), and upper and lower limit alarm devices. The temperature measuring device is not affected by surface oxide scale, dust, smoke, or water vapor. The accuracy and durability of the temperature measuring device are guaranteed for 12 months. VII. Electrical Control and Human-Machine Interface The control cabinet adopts an electromechanical integrated control box, made of high-strength board with powder coating to prevent oxidation. The external control cabinet is manufactured according to a protection level of not less than IP54. Main low-voltage electrical components in the cabinet are Schneider Electric brand, circuit breakers are Chint, cables are high-quality copper core cables, and signal lines are shielded cables. The PLC is a Siemens S7 series unit with a Profinet communication interface module, and the program design includes a fault information feedback and self-diagnosis system. The human-machine interface adopts a 15-inch color touch screen (TPC1571) from Beijing Kunlun Tongtai. Program-related settings can be input via the touch keyboard, and verified and stored product parameters (capable of loading and reading more than 50 kinds of process parameters) can be queried and printed at any time. The cycle time (directly input time) and material length can be set on this screen, and the screen can automatically record the quantity of low-temperature material, qualified material, and high-temperature material. Operation is divided into two modes: automatic and manual, switched via a two-position selector switch. In automatic mode, the entire device can be started and stopped using only the start and stop buttons; in manual mode, various functions can be started individually using buttons, with all operations performed on the touch screen. The intelligent fault identification function displays fault content and provides corresponding solutions when misoperation or special working condition alarms occur, enabling operators to quickly handle more than 90% of common faults. The medium frequency power supply cabinet is equipped with a fault diagnosis panel. When the system experiences faults such as overvoltage, overcurrent, water outage, or fuse failure, it immediately stops the machine and automatically disconnects the main power switch. VIII. Special Working Modes for Forging Enterprises Initial working mode: When each shift starts, the induction heating system has just started and the temperature inside the inductor furnace is the initial temperature. To reduce the generation of low-temperature material, this mode increases or maintains power accordingly in rhythm or speed when the heated material is fed in a rhythm or speed, ensuring that each bar reaches the forging temperature. Menu mode: When the user reheats the billet, they only need to enter the order number in the menu, and the induction heating system automatically runs according to the heating data in the menu without manual adjustment, ensuring consistency in product heating quality. Furnace cleaning mode: When furnace cleaning is required after the day's work, simply activating the furnace cleaning mode causes the feeding mechanism to push empty dummy material into the furnace chamber according to the set rhythm, with power gradually decreasing, maximizing energy savings during the furnace cleaning process.