Wuxi Wondery Industry Equipment Co., Ltd

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.

I. Project Background and Equipment Specifications This case study involves a fully automatic intelligent ion nitriding furnace, model WDL-IV-30A, employing a vertical single-bell-jar single-station structure. The equipment is capable of ion nitriding and soft ion nitriding of titanium alloys, alloy steels, mold steels, and stainless steels. The effective working zone of the furnace body measures 300 mm in diameter and 400 mm in height, with a maximum loading capacity of 100 kg. The common operating temperature range is 500 to 600°C, with a maximum operating temperature of 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 pump 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, 30 represents the maximum average current of the pulse power supply at 30 amperes, and A represents the fully automatic intelligent type. II. Physical Constraints of the Ion Nitriding Process Ion nitriding is conducted in a low-pressure gas discharge environment, and its volt-ampere characteristic curve is non-linear. Ion nitriding of metallic materials generally operates in the "abnormal discharge" segment of the volt-ampere characteristic curve, and the upper limit point G of this segment is a dangerous inflection point. Gas discharge, as a power source, presents a load with negative resistance characteristics. The workpiece, acting as the cathode, has its surface shape and surrounding environment (workpiece stacking) both affecting the surface current density. These physical characteristics determine that the ion power supply must overcome three technical difficulties. The first is arc discharge: when the workpiece surface is not clean, a non-conductive oil film can easily form. When charge accumulates on the surface to a certain extent, it breaks down and forms a momentary high-current discharge, producing high-energy sparks. If not cut off quickly, this will cause power failure and workpiece damage. The second is the hollow cathode effect: when workpieces have holes or slots, gaps between workpieces, or uneven bends, a critical state of glow discharge overlap occurs at certain gas pressures. This manifests as uneven glow discharge brightness across the workpiece surface, corresponding to uneven surface current density, causing uneven temperature distribution. The third is the coupling relationship between current density and gas pressure: gas pressure affects glow thickness, which in turn affects current density – higher pressure produces a thinner glow, beneficial for temperature uniformity; however, when pressure is high enough to uniformly cover all groove and hole surfaces, the current will greatly exceed the power required for workpiece insulation. III. Technical Response Logic of the Pulse Power Supply The pulse power supply configured for this equipment has an output frequency of 20,000 Hz, a square wave output waveform, an output voltage continuously adjustable from 0 to 900 V with no sudden jump above 200 V, a duty cycle continuously adjustable within the range of 10% to 85%, a maximum pulse output average current of 30 A, and an arc extinguishing time of no more than 2 μs. The duty cycle is defined as the ratio of on-time to pulse period. The average heating power equals the peak voltage multiplied by current, then multiplied by the duty cycle. The introduction of an adjustable duty cycle in the pulse power supply effectively resolves the contradiction between the average heating power and the threshold conditions required for workpiece processing – the essence of this contradiction being that, to satisfy the current density required for uniform glow coverage, the heating power may exceed the power required to maintain workpiece temperature, and duty cycle adjustment allows these two to be decoupled. Fast arc extinguishing is achieved by utilizing the principle of electromagnetic induction in the discharge circuit to rapidly detect the arcing signal (with almost no delay), 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. The application of the pulse power supply also yields several process effects: the absolute off-time of the pulse is relatively short, and after power is turned off, the concentration of charged particles does not immediately drop to zero but decreases slowly. Before it has decreased significantly, the next pulse arrives, resulting in a higher average electron concentration and increased ionization rate; the hollow cathode effect is effectively suppressed; and because the pulse power supply widens the adjustment range of nitriding process parameters, with each parameter independently adjustable, it can improve the uniformity of glow coverage on workpieces with complex surface shapes, thereby enhancing infiltration layer quality and surface smoothness. IV. Three-Parameter Closed-Loop Control System The control system uses a programmable logic controller and touch screen as the main control center. The PLC is an FX3G series unit with 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. Flow control is configured with one dedicated mass flow meter to control gas flow. The pressure closed-loop implementation path 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 precision of ±1 Pa, while 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. Flow control employs Japanese HORIBA S500 series mass flow meters, 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. V. Furnace Body System Structural Features The furnace body adopts a vertical bell-jar structure, consisting of two parts: the bell and the base. The bell cylinder adopts a water-cooled double-wall structure and multi-channel water cooling system to ensure furnace temperature uniformity. Six layers of 310S stainless steel heat shields are installed inside the cylinder, and two layers of stainless steel heat shields are installed on the upper part of the furnace base, enabling long-term high-temperature operation and significant energy savings. A layer of aluminum silicate insulation cotton with a thickness of 20 mm is added inside the insulation layer near the furnace wall. 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 310S stainless steel plate with a thickness of no less than 30 mm; the material tray fixture frame that contacts the workpiece is also made of 310S stainless steel. The cathode connection device is designed as a rigid connection to avoid overheating problems caused by loose quick-connect couplings. 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. The base center has a vacuum extraction port and a cathode inlet, connected by flanges, thick-walled stainless steel pipe, and stainless steel bellows, with sealing provided by high-temperature-resistant fluororubber sealing rings. VI. Vacuum and Gas Systems 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 system is equipped with one 2X15 rotary vane pump as the vacuum unit. The pump set includes 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. Vacuum measurement employs a ZJ-1C type capacitive diaphragm absolute pressure transmitter. This vacuum gauge is not affected by the type and composition of the measured medium, providing accurate and reliable measurement, with the measured value displayed by a digital display instrument and participating in furnace pressure control. The gas distribution system is used to control the introduction of process gas into the furnace, consisting of a gas source, flow meter, and corresponding pipelines. Process gases (such as ammonia) are provided by the user, passing through a mass flow meter and then introduced into the furnace body through a dedicated mixing tank according to the process formula. Gas pipelines are made of stainless steel, with each gas line equipped with a pressure reducing valve, manual shut-off valve, filter, pressure gauge, and solenoid valve. VII. Cooling Water System The cooling water system adopts a circulating cooling method, with the water source provided by the cooling tower and water pump (buyer's responsibility). 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 for individual flow adjustment. 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, and the control system will take corresponding protective actions. A backup water inlet valve is installed at the main water inlet pipe, connected to the user's tap water pipe – in the event of an unexpected power outage or water outage, the furnace body can be cooled by tap water. VIII. Safety Interlock and Alarm Logic The system has alarm functions for over-temperature, over-pressure, thermocouple damage, water shortage, and phase loss, with both audible and visual alarms and control interface alarms, taking corresponding protective actions such as prohibiting power-on, prohibiting heating, cutting off or resuming heating according to specific problems. The control system can realize self-diagnosis of equipment faults, prompting users to check and repair the corresponding fault points. When a fault occurs, the system automatically shuts off all valves. The vacuum system has sequential start and stop functions, equipped with a complete interlocking and mutual interlocking mechanism, with all valves being power-off shut-off type.

I. Project Background and Equipment Application Positioning This case study involves a ladle heating station used for preheating ladle linings after repair and before receiving molten metal. The core function of the equipment is to provide smooth and controllable heating of the lining prior to casting, in order to stabilize the casting temperature regime, reduce metal loss, and ensure process repeatability. The operating environment is an industrial workshop, requiring stable operation across multiple heating cycles. The station is designed to accommodate a conical ladle with a 1-ton molten steel capacity. The ladle has an internal top diameter of 500 mm, internal bottom diameter of 410 mm, and depth of 900 mm; the external top diameter is 770 mm, and the overall height is 1,050 mm. These dimensions establish the geometric boundary conditions for heating element arrangement and station structural design – the conical inner cavity means the radial spacing of heating elements varies along the height direction, precluding the conventional arrangement used for equal-diameter cylindrical furnace chambers. II. Heating System Technical Parameter Requirements The equipment requires electric heating with a total installed power of no less than 30 kW. Heating elements are resistance type, required to withstand high-temperature long-term operation and cyclic thermal loading. The maximum heating temperature must be no less than 800°C, and the heating element temperature must exceed the lining working temperature to ensure sufficient heat transfer intensity without localized overheating. There are inherent constraints among these parameters: an 800°C lining target temperature means the heating element surface temperature must be maintained at a higher level to establish an effective radiative heat transfer differential. If the element surface load is set too high, heat transfer intensity increases but element life under cyclic thermal loading is shortened; if set too low, heating time is extended. Therefore, element material selection and surface load design constitute the core technical trade-off of this project. III. Temperature Uniformity and Control Accuracy Requirements The technical requirements specify two temperature indicators: system temperature stability control accuracy of at least ±10°C, and internal ladle temperature differential not exceeding 50°C. Uniform heating of the ladle inner surface is required along the full height, meaning the type and arrangement position of heating elements must be specifically selected in conjunction with the conical ladle geometry to minimize temperature gradients. The design challenge presented by the conical structure is that the lower section has a smaller diameter while the upper section has a larger diameter. If vertically suspended straight rod elements were used, the spacing between the lower section and the lining would be greater than at the upper section, resulting in insufficient radiative heat transfer intensity at the bottom. Therefore, elements may require segmented arrangement or non-standard geometry to compensate for this geometric difference. The control system must be capable of operating automatically according to a given heating curve, and also allow manual control of main parameters. Temperature control is achieved through real-time thermocouple monitoring, with real-time parameters displayed on the operation panel. Lining heating must be smooth and controllable, eliminating abrupt temperature changes – this requirement points to a heating rate limitation function, meaning the control system requires slope control capability rather than simple on-off temperature regulation. IV. Structural and Safety Design Requirements The heating unit must be insertable into the ladle interior and lockable in the working position. Heating elements must have protective structures to prevent mechanical damage and contact with the lining, such as heat-resistant steel protective mesh or protective sleeves. This requirement stems from actual operating conditions: during ladle lifting and positioning, positional deviation exists, and without protection, elements could be damaged by collision with the lining or ladle wall. Cable routing and connection points must be constructed from high-temperature-resistant materials suitable for high-temperature operation. The equipment structure must facilitate maintenance, allowing heating element replacement without complete disassembly – an important availability indicator, since heating elements are periodic consumables and replacement convenience directly affects equipment downtime. Safety requirements include short circuit, overload, and leakage protection devices, as well as emergency stop, over-temperature protection, and abnormal condition interlock protection functions. Hazardous areas must have structural guards to prevent accidental personnel entry. The equipment must be grounded per code, with no accessible live parts under normal operating conditions. Protection scope covers three risk categories: electric current injury, high-temperature injury, and injury from moving and rotating equipment parts. V. Environmental Adaptability and Power Supply Conditions The equipment is powered by AC 380V, 50Hz. The operating environment temperature range is +5°C to +40°C. The equipment structure must be resistant to dust, vibration, and other factors typical of metallurgical production conditions. This environmental requirement imposes constraints on the protection rating and cooling method of the electrical control cabinet – the dust and vibration environment of a metallurgical workshop is unsuitable for conventional open cooling structures. VI. Scope of Supply and Documentation Requirements The scope of supply includes the complete heating station, comprising heating elements, control cabinet, temperature measurement system, and connecting cables. Supply completeness must ensure the equipment can be directly commissioned without additional procurement of major components. Technical documentation includes operation manual, electrical schematic diagrams, general assembly drawings, and installation instructions, sufficient to ensure safe operation and maintenance of the equipment. VII. Service Life and Technical Support Requirements The warranty period is no less than 12 months from the date of commissioning. During the warranty period, faults and defects attributable to the manufacturer shall be rectified by the supplier. Under compliant operating conditions, equipment service life is no less than 5 years. The equipment must reach the set heating temperature within a reasonable process time agreed with the customer, and ensure parameter stability across multiple heating cycles for repeatable process operation. The control system must have high reliability and resistance to industrial interference. Technical support scope includes operational technical consultation, melting mode setup recommendations, and technical assistance under emergency conditions