Wuxi Wondery Industry Equipment Co., Ltd

I. Project Background and Process Positioning This case study involves an aluminum ingot continuous casting machine, model WDL-ZDX-7, designed for automated continuous production of various aluminum ingot shapes, capable of 24-hour uninterrupted operation. After molten aluminum is injected into the chute, it is evenly distributed into the aluminum ingot molds of the chain casting machine by the distribution system, cooled and solidified by water spray, and finally demolded by a hammer demolding device. The equipment dimensions are 7,500 mm in length, 1,250 mm in width, and 1,100 mm in height, with adjustable height. The single ingot weight is 6 kg, with a designed capacity of no less than 3 tons per hour. The casting temperature range is 680 to 720°C. II. Matching Relationship Between Capacity and Mold Quantity The equipment is equipped with 90 aluminum ingot molds, using chain-plate transmission for circulating casting. Based on a single ingot weight of 6 kg and a capacity of 3 tons per hour, approximately 500 casting actions are required per hour, corresponding to a mold circulation cycle of approximately 7.2 seconds per mold position. The configuration of 90 molds means there is sufficient cooling travel between the casting point and the demolding point. The residence time of molten aluminum in the mold is determined jointly by chain speed and mold spacing – this parameter matching is the physical basis for ensuring that the ingot is sufficiently solidified at demolding. The power system employs a K97 model 3 kW variable-frequency motor with a helical gear reducer, with stepless adjustment via variable frequency. The significance of speed adjustment lies in the following: when casting temperature is lower or ambient temperature is lower, chain speed can be appropriately reduced to extend cooling time; when production pace needs to be increased, chain speed can be correspondingly increased. This adjustability enables the equipment to accommodate differences in solidification characteristics among different aluminum alloy grades. III. Mold Material and Demolding Process The aluminum ingot mold core adopts a coated sand casting process, with a single mold weight of 28 kg. The surface quality of coated sand molds is superior to ordinary sand molds, resulting in fewer surface defects on the cast ingots, while the mold itself offers higher dimensional accuracy and thermal stability. The 90 molds are arranged in chain-plate circulation, running synchronously with the transmission chain. Demolding employs a mechanical hammer impact method. The reliability of hammer demolding depends on the matching between the mold draft angle design and the aluminum ingot cooling shrinkage – if the draft angle is insufficient or cooling is inadequate, the hammer impact force must be increased, which accelerates wear on both the mold and the hammer mechanism over long-term operation. The mold service life is specified at 24 months, an indicator directly related to casting temperature control, cooling intensity, and demolding operation discipline. IV. Transmission System and Key Component Parameters The transmission system consists of gears, chain plates, rollers, and pin shafts. The casting machine chain is 30 meters long with a pitch of 165 mm. The chain plates are made of 8 mm thick manganese plate, quenched, with built-in wear-resistant sleeves; rollers are 45# steel, and wear-resistant sleeves and pin shafts are 40Cr. This material combination addresses the operating conditions of casting machine chains under high temperature, abrasive wear, and alternating loads – manganese plate quenching provides surface hardness for the chain plates, while 40Cr pin shafts provide core toughness. There are 4 transmission gear disks, made of 45# steel with high-frequency quenched tooth tips, 8 teeth at the rear and 8 teeth at the front. There are 2 transmission shafts, lathe-machined, with both driving and driven shafts at Ø70, material 45# steel. The coupling flange disk adopts a sprocket plus double-row chain clamp-type connection, which transmits torque while allowing compensation for certain installation deviations. The frame is welded from channel steel and rectangular tube, with structural rigidity and dimensional stability meeting the load-bearing requirements of a 7.5-meter-long equipment. V. Cooling and Distribution Systems The cooling method is water spray. The water distributor is a cast-iron part with 8 nozzles, uniformly spraying cooling water onto the bottom and sides of the molds. The cooling water collection system is included in the equipment supply scope, with sprayed water collected and recovered to prevent workshop flooding. The distribution system moves synchronously with the molds. Molten aluminum enters the distributor through the chute and is evenly injected into each mold. The purpose of synchronous movement is to ensure that the distributor outlet and the mold pouring gate remain aligned during the casting instant, avoiding aluminum overflow or uneven pouring that would cause ingot weight deviation. VI. Electrical Configuration and Operational Stability The power supply is 380V three-phase four-wire 50Hz AC, customizable as required. The control system includes an inverter, with Delta as the inverter brand. Electrical components are all international brands with reliable performance. All accessories are market standard parts, offering high convenience for procurement and repair. Operational stability is ensured by two aspects: first, variable frequency speed adjustment allows continuous adjustment of chain speed according to process requirements, avoiding rigid impact at fixed speeds; second, the K-series helical gear reducer offers smoother transmission than ordinary gear reducers, with better noise and vibration control under long-term continuous operation.

I. Project Background and Equipment Specifications This case study involves the WDL-RG series elliptical resistance crucible furnace, available in 400 kg, 600 kg, and 800 kg capacity configurations. The equipment is designed for factory workshop environments with an ambient temperature of 0 to 60°C and relative humidity of 40% to 70%. The rated aluminum liquid temperature is 650 to 700°C. All three configurations achieve a full-load melting time of no more than 4 hours. Heating power increases with capacity: the 400 kg model is rated at 66 kW, the 600 kg model at 90 kW, and the 800 kg model at 105 kW; corresponding heating currents are 99 A, 135 A, and 158 A respectively. The input power supply is uniformly 380V AC, 50Hz, three-phase five-wire. The control cabinet measures 650×600×400 mm, with an S7-200smart PLC and touch screen as the main control system. Temperature measurement uses 2 channels with a range of 0 to 1300°C. Aluminum liquid temperature control accuracy during the holding stage is ±5°C. Protection mechanisms include leakage protection and over-temperature protection. II. Cascade PID Temperature Control Architecture The core feature of this equipment's temperature control is the adoption of a cascade PID control structure rather than single-loop PID. There are two temperature measurement channels in the system: one for furnace atmosphere temperature and one for aluminum liquid temperature. The cascade control action path is as follows: the outer loop uses aluminum liquid temperature as the main control parameter, and the inner loop uses atmosphere temperature as the auxiliary parameter. The setpoint of the inner loop is dynamically generated by the PID output of the outer loop. The engineering significance of this architecture lies in the fact that aluminum liquid temperature changes with relatively large lag, while atmosphere temperature responds faster. If the heating power were adjusted directly based on aluminum liquid temperature deviation, overshoot or sluggish response would be likely. With atmosphere temperature introduced as the inner loop, the system can respond quickly through the inner loop before the aluminum liquid temperature deviates significantly, ensuring both response speed and overshoot suppression. The PID control interface on the touch screen provides three independent input boxes for P, I, and D parameters, with a real-time temperature curve displayed at the top of the interface, supporting sliding of the time axis to view historical data within 0.5 hours. When parameters are adjusted, the temperature curve provides real-time feedback to help operators judge the adjustment effect. III. Three Process Modes Related to the Crucible The equipment has three preset working modes, switched via a drop-down menu on the touch screen. The design of all three modes revolves around thermal stress management of the graphite crucible. The sintering and solidification mode is a dedicated program for the first heating of a new crucible. This program is divided into 6 heating steps, with the starting setpoint rising progressively from 50°C to 800°C, and the corresponding heating rate decreasing progressively from 36°C/s to 6°C/s. The design logic of this decreasing heating rate is that faster heating can be tolerated in the low-temperature stage, while the rate must be reduced near the sintering temperature to avoid thermal stress cracking of the crucible caused by excessive temperature differential between the interior and exterior. The upper right corner of the interface verifies operating prerequisites in real time, with items that do not meet the standards warned in black font and items that pass marked in green font. The preheating mode is a secondary preheating program after the equipment completes the first sintering and solidification. Its running time is shorter than that of the sintering and solidification mode, but the temperature curve settings, condition verification rules, and temperature monitoring parameters are completely consistent with the sintering and solidification mode. This design enables the equipment to restore working temperature along a controlled heating path when restarted after shutdown, avoiding direct full-power startup from a cold furnace. The working mode is the standard state after the equipment enters normal production. When the furnace temperature reaches the preset operating threshold and the thermal field uniformity meets the requirements, the system confirms the state switch through audible and visual prompts. IV. Parameterized Requirements for Crucible Installation and Preheating The selection of the crucible base directly affects crucible life. The base shape should match the crucible bottom, with a size approximately 2 cm larger. Crucible bases of appropriate height should be selected for different types of crucible furnaces. Using discarded crucible bases will greatly shorten the crucible's service life. For installing a resistance furnace crucible, the crucible should be placed in the center of the furnace, with the bottom of the crucible higher than the bottom row of heating elements. Insulation cotton should be used to seal the area between the top of the crucible and the furnace rim. The parameter path for the first preheating of the crucible is as follows: without adding any material, preheat to approximately 200°C for 30 minutes, then dry for 4 hours. The purpose of this step is to evaporate moisture adsorbed on the crucible surface, preventing cracking during initial use. After preheating, the crucible should be heated to 800 to 900°C (about 2 hours) as soon as possible and held at that temperature for 1 hour, then raised or lowered to the working temperature. This rapid passage through the temperature range is designed to move the graphite crucible quickly through the oxidation-prone temperature band. After the first preheating, the crucible usually does not need to be preheated again unless the crucible becomes damp again. V. Thermal Stress Constraints in Charging and Operating Procedures The metal material must be dried before it is added. When adding materials, place them gently; do not throw or pour metal ingots into the crucible. Place the metal ingot vertically into the crucible, ensuring sufficient space between the ingot and the crucible wall for expansion. Do not place the ingot horizontally in the crucible, as the expansion of the ingot during heating may damage the crucible. You can first add some small pieces of metal into the crucible as a base for the larger ingot. During continuous smelting, some molten metal can be retained in the crucible to accelerate the melting process. However, large pieces of metal should be avoided incorporating into small amounts of solution, as this could cause the solution to cool rapidly or solidify, damaging the crucible. When adding liquid metal, avoid overfilling; generally, the crucible should not be filled to more than 80% capacity. Additives should only be added after the metal has completely dissolved. Additives should never be added to an empty crucible or to solid metal, nor should they be allowed to directly contact the crucible wall or outer rim. The prescribed dosage must be strictly followed, as excessive use of additives will significantly shorten the lifespan of the crucible. The size of the crucible tongs must match the size and shape of the crucible, and they must not squeeze the upper edge of the crucible. The crucible tongs should be clamped in the lower middle part of the crucible – if too high, the crucible may fall off or be damaged; if too low, it will be difficult to operate during pouring. When moving a hot crucible, it should be placed on a high-temperature resistant plate or transport tool. Do not place a hot crucible on a cool surface to avoid damaging the bottom of the crucible. When it is necessary to temporarily stop using the crucible for reasons such as removing slag or repairing the crucible furnace, the molten metal inside the crucible should be emptied. If the molten metal is left to solidify inside the crucible, it will burst due to expansion during the next heating. VI. Slag Removal Frequency and Crucible Corrosion Control During the smelting process, additives and impurities in the molten metal will form slag, which adheres to the crucible wall. Because the slag contains additive components, it will corrode the crucible wall, so the slag should be removed once a day. Specialized tools should be used to remove molten slag before it solidifies. Solidified slag will be difficult to remove. When removing slag, avoid scratching the crucible wall. When multiple layers of slag solidify and remain on the crucible wall, they will corrode the crucible, affect its thermal conductivity, and cause the crucible to crack during heating and expansion, thus shortening the crucible's service life. VII. Control System Interface and Data Recording The control cabinet panel is equipped with a three-color indicator light: red for Level 1 error alarm, yellow for Level 2 warning alarm, and green for automatic operation indication. The LED digital display shows the current ambient temperature during preheating and sintering modes, and the current aluminum liquid temperature during operating mode. The touch screen system features hierarchical user permissions, with different permission levels corresponding to different operating scopes. The main interface displays equipment status, heating system status (including power regulator contactor open/closed state and regulator readiness status), real-time three-phase current monitoring values, and the current and set values of atmosphere temperature and aluminum liquid temperature. The atmosphere temperature setpoint upper limit is 950°C, and the aluminum liquid temperature setpoint upper limit is 900°C. The energy consumption statistics interface records the cumulative electricity consumption since the equipment was put into use, as well as the daily electricity consumption of the last two weeks. The I/O monitoring interface displays the real-time action status of PLC input points. The alarm event interface sounds the buzzer immediately when a fault occurs; if the fault cannot be eliminated temporarily, clicking the mute button silences the buzzer, and a new fault will automatically unmute and sound again. After the fault is cleared, clicking the reset button clears the current alarm.

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.