Mold temperature, as one of the most important parameters in die-casting process, has become a core means for manufacturing companies to improve casting quality, increase casting yield, and optimize equipment operating efficiency (OEE). In detection of mold temperature, traditional temperature measurement tools such as temperature boxes, multi-point thermometers (thermocouples) and spot thermometers have been widely used. However, these conventional temperature measurement methods have some inevitable limitations, such as deviations in thermocouple characteristic curves, influence of electromagnetic interference, temperature limits of viscose materials, accumulation of sticking point errors, and contact requirements for measured object. These problems significantly affect accuracy of mold temperature measurement, thereby restricting further improvement of mold temperature regulation. In contrast, by using infrared thermal imaging technology for online temperature monitoring, not only can real-time temperature detection of tens of thousands of measuring points of mold be achieved without stopping or touching mold, but also high-resolution infrared thermal images can be generated based on mold temperature matrix, providing scientific support and decision-making basis for intuitive analysis of mold temperature and process optimization.

Die-casting process is an efficient and precise metal forming technology that achieves mass production of complex-shaped parts by injecting molten metal into mold under high pressure for rapid forming. As a widely used process in modern manufacturing, die-casting is known for its high production efficiency, high precision, and good material utilization. In each die-casting cycle, whether in heating stage or mass production stage, mold temperature monitoring system can obtain heat distribution map of mold in real time and dynamically correct the heat balance of mold. This process helps engineers optimize die-casting parameters according to heat distribution and ensure that die-casting quality is always under control. By effectively monitoring surface temperature of mold and its changes, heat distribution can be accurately controlled and heat exchange method can be improved, thereby significantly improving quality of casting and reducing the casting defect rate. In addition to quality improvement, die-casting process also has significant advantages in resource conservation. Continuous monitoring of mold surface temperature not only extends service life of mold, but also shortens production cycle time and reduces frequency and cost of unplanned maintenance. At the same time, accurate temperature control can effectively reduce consumption of energy, compressed air and release agents, and reduce discharge of wastewater. In a mass production environment, mold temperature monitoring system has become an ideal choice for improving quality of castings and overall equipment efficiency (OEE), providing important technical support for manufacturing companies in competition.
In die-casting process, control of mold surface temperature is crucial to quality of casting. Temperature runaway is often one of main reasons for defects such as shrinkage marks, sand holes, cracks and bubbles in product. Uniformity of mold surface temperature directly affects solidification process of metal and internal structure of casting, thereby determining quality of final product. Therefore, accurate detection of mold surface temperature distribution is of great significance to ensure quality of die-casting process, achieve efficient and defect-free industrial production. With rapid development of infrared thermal imaging technology and continuous decline in hardware costs, it has become possible to use infrared thermal imagers to monitor mold surface temperature in real time. Compared with traditional contact temperature measurement method, infrared non-contact temperature measurement has advantages of fast, accurate and non-interference, which greatly improves efficiency and reliability of mold temperature monitoring. This technological advancement not only optimizes control accuracy of mold temperature, but also provides strong support for improvement of casting quality and production efficiency.
In die-casting process, traditional mold temperature monitoring method has obvious shortcomings it is difficult to meet needs of accurate and real-time control of mold temperature. For example, point temperature gun can only measure temperature of a single point of mold, and location of temperature abnormality area needs to be speculated based on experience, which lacks comprehensiveness and intuitiveness. Although thermocouples can also measure single-point temperature, they need to be in direct contact with mold, which not only increases complexity of operation, but also may bring safety hazards. In addition, although handheld thermal imagers can capture temperature distribution on mold surface, it is difficult to achieve continuous monitoring, and it is impossible to ensure that thermal images taken each time are uniform in time. These limitations make it difficult for traditional methods to provide reliable mold temperature data support for efficient and defect-free production, thereby limiting optimization and stability of die-casting process.
This paper aims to propose and design an innovative mold temperature control scheme to improve quality control level of die-casting process in response to shortcomings of current mold temperature control method. Traditional mold temperature monitoring methods, such as spot temperature guns and thermocouples, are difficult to meet needs of modern die-casting processes for precise temperature control due to limited measurement range, insufficient operational safety, and lack of real-time performance. Although handheld thermal imagers can provide visualization of temperature distribution, they cannot achieve continuous monitoring, and shooting time of thermal images is difficult to synchronize, which limits their application effect. Therefore, starting from solving these key problems, this paper designs a mold temperature control scheme based on infrared thermal imaging technology, combining real-time monitoring, non-contact temperature measurement, and high-precision temperature analysis, aiming to significantly improve accuracy and efficiency of mold temperature regulation. At the same time, through experiments, its actual effect in quality optimization of die-castings is verified, and potential of this scheme in industrial applications is explored, providing theoretical and technical support for improving casting yield and operating efficiency of die-casting equipment.

System consists of a variety of key hardware, including online infrared thermal imagers, thermal imager protective covers, power supply equipment installed at die-casting site, and industrial computers or PCs for on-site monitoring. Among them, online infrared thermal imager, as a core component, can collect temperature distribution data on mold surface in real time, generate high-resolution thermal images, and provide an intuitive reference for mold temperature analysis. Thermal imager protective cover provides necessary physical protection for equipment to ensure its stable operation in complex working environments such as high temperature, high pressure, and humidity. Power supply equipment provides stable energy support for continuous operation of system, while industrial computer or PC, as a data processing and monitoring center, is responsible for real-time reception, storage and analysis of temperature data collected by thermal imager, assists operators in dynamically monitoring and optimizing mold temperature control. Through close cooperation of various hardware, system can realize real-time and accurate monitoring of mold temperature without interrupting production, provide efficient and reliable temperature management support for die-casting process. Components will be described in detail below.

Core device of system is a high-performance infrared thermal imager, which integrates imported processing chips, French infrared thermal imaging chips and Xilinx FPGA logic chips. Combination of these high-end hardware ensures excellent computing performance and stability of equipment. Resolution of infrared thermal imager is 640×480 infrared pixels. Compared with traditional equipment, its pixel density is higher, which can present a clearer temperature distribution map, accurately capture temperature changes on mold surface, and meet needs of high-precision measurement. Equipment can accurately identify temperature distribution of measured object at a distance of 3 meters, ensuring that even in complex environment of production site, it can maintain high temperature measurement reliability and imaging quality. In addition, under visual conditions, infrared thermal imager can clearly distinguish mold contour and accurately measure temperature of a pin with a diameter of 10mm, providing support for thermal distribution analysis of fine parts. Infrared thermal imager also has excellent stability and supports 7*24 hours of uninterrupted operation. Even in harsh industrial environments such as high temperature, high humidity or vibration, it can continue to provide reliable temperature data. This design effectively avoids problem of reduced production efficiency caused by intermittent shutdown or errors of traditional temperature measurement equipment, and is particularly suitable for high-intensity die-casting production environments.
Specific equipment parameters are shown in Table 1:

In order to ensure that infrared thermal imager can operate stably in harsh environments such as high temperature, oil mist and gas mist in die-casting industrial site, system uses a specially designed IP67-level protective thermal imager protective cover. Protective cover has been rigorously tested in industrial site, has excellent sealing and anti-pollution capabilities. At the same time, it integrates multiple functional designs to fully guarantee long-term stable operation of equipment. Protective cover is equipped with an air-cooled cooling device, which effectively controls internal temperature of equipment through efficient heat dissipation technology, and can maintain performance of equipment even in extremely high temperature environments. In addition, front end of protective cover is equipped with an air curtain and a pneumatic baffle to form a clean airflow barrier, effectively isolate oil mist and gas mist, and ensure that lens surface is always kept clean, thereby avoiding degradation of imaging quality caused by dirt. Protective performance of protective cover not only extends service life of equipment, but also ensures accuracy and consistency of mold temperature monitoring.
Specific performance parameters of protective cover are shown in Table 2:

In order to ensure efficient operation of mold temperature monitoring system in industrial site, system adopts a fully functional integrated cabinet design, integrating various key components and functions into a unified structure, taking into account convenience and reliability. Design details of cabinet fully consider actual needs of die-casting site, with high performance, high durability and easy maintenance. Cabinet is equipped with an air source pressure detection device, which monitors air source pressure in real time through a pressure relay, and detection results are intuitively displayed on screen. When air source pressure is too low, system will trigger a fault alarm and stop automatic mold temperature collection to ensure safe operation of equipment. Cabinet also integrates a water separator filter for efficient filtration of impurities and water vapor in air source and is easy to maintain. Human-machine interaction terminal and equipment cabinet adopt an integrated design with a compact structure and a hook on the top for easy on-site lifting and transportation. According to on-site needs, external dimensions of cabinet can be customized to adapt to different installation environments. Core control hardware is Advantech brand industrial computer, pre-installed with 64-bit Chinese Enterprise Edition Windows 10 system, equipped with i5 and above processors, 16GB memory, 216GB solid state drive and 1TB mechanical hard disk, supports WIFI remote operation and upgrade. Interactive interface uses Philips 24-inch touch screen to provide users with a friendly and intuitive operation experience. In terms of power supply, cabinet supports AC220V 50Hz power supply and DC24V control power supply, which can be adjusted according to on-site conditions. System is designed with signal anti-interference measures and short-circuit protection functions to effectively improve stability of signal transmission and safety of equipment operation. In addition, cabinet is equipped with a three-color alarm light to indicate system operation status. Other functions include RJ45 interface reserved for external system communication and additional USB interface to meet diverse external connection requirements. The overall air source requirement of equipment is not less than 0.5 MPa to ensure stability and reliability of system operation. This integrated cabinet provides a solid foundation for mold temperature monitoring system through high integration and optimized design, which can meet diverse needs in complex environment of die-casting site. Detailed function introduction is shown in Table 3:

Mold temperature control system has high precision, high consistency and a wide temperature measurement range as its core technical features. Its performance upper limit fully reflects system's excellent adaptability and reliability in complex industrial environments. Following key parameters specifically describe the system's technical performance and application value:
1. Full-range temperature measurement accuracy: System achieves a temperature measurement accuracy of ±2℃ or ±2%, which can meet stringent requirements for mold surface temperature monitoring during die-casting process. Accurate temperature measurement data not only helps to identify temperature anomalies, but also provides a reliable basis for mold temperature adjustment, effectively avoiding casting defects caused by temperature fluctuations, such as shrinkage marks, cracks and bubbles;
2. Temperature measurement consistency: System's temperature measurement consistency is as high as ±1℃ or ±1%, which can ensure that temperature data at different time and space points always remain highly consistent. This feature is particularly important in continuous process of die-casting production, and can provide stable thermal distribution monitoring to provide support for precise control of process parameters;
3. Ambient temperature adaptability: System can operate stably in an ambient temperature range of -30℃ to 100℃, adapting to extreme working environment of die-casting site. This environmental adaptability ensures that system can still provide reliable temperature measurement results under harsh conditions, laying a solid foundation for long-term industrial applications;
4. Temperature measurement range: System's temperature measurement range covers -20℃ to 650℃, fully meeting full process requirements of mold from low-temperature preheating to high-temperature die casting. Wide temperature measurement range makes system suitable for a variety of different process requirements, with higher versatility and flexibility;
5. Infrared pixel resolution: System is equipped with a 640×480 pixel infrared thermal imager, which achieves clear thermal imaging effects with its high resolution. Imaging details are rich, which can intuitively show thermal distribution state of mold surface and provide engineers with accurate visual analysis tools. In addition, high pixel resolution ensures point density and resolution of temperature measurement, and can accurately measure temperature of a small target area with a diameter of 10mm.
Through above key parameters, system demonstrates its excellent performance in die-casting process, has ability to monitor mold temperature in real time, efficiently and accurately. These technical performances not only help improve quality of castings, but also significantly improve production efficiency, reduce resource waste and maintenance costs, and provide strong technical support for modern die-casting production.

During die casting production process, control of mold temperature is crucial, especially in cooling stage after spraying. Usually, mold temperature after spraying should be quickly reduced to about 150℃ to ensure good casting quality, avoid local stress concentration and crack generation of parts due to excessive temperature. However, in a certain production batch, temperature of pin part remained at 216℃ after cooling, which was much higher than ideal temperature, which led to frequent cracking of parts produced in this part. Since thermal imaging technology was not used in previous production process, production team failed to discover problem of cooling system in time. Only when quality of parts was abnormal did they realize that there might be a temperature control problem in this part. As shown in Figure 1

 

In order to accurately locate problems in cooling process, a thermal imaging monitoring solution was designed for this experiment. Core goal of experiment is to use thermal imaging technology to monitor cooling process of mold in real time, to promptly discover and analyze temperature abnormality area, especially temperature abnormality of pin part.
During experiment, a high-precision thermal imager will be used to monitor temperature of each part of mold, especially pin area, temperature distribution and changes will be clearly displayed with the help of thermal imaging images. In this way, it is possible to intuitively understand whether temperature drops evenly and accurately locate abnormal parts, thereby providing data support for subsequent adjustment of cooling system.
Experimental steps include:
First, a baseline measurement of temperature of mold after spraying is performed to ensure that its temperature distribution meets expected requirements;
Then, during cooling process of mold, mold is continuously monitored by a thermal imager, especially focusing on pin part to observe temperature changes during cooling process. As shown in Figures 2 and 3.

 

Infrared temperature change trend of pin after spraying

 

Through these data, problem of uneven cooling or insufficient cooling of pin part can be discovered in time. Finally, according to thermal imaging results, cooling system of mold is adjusted to optimize cooling efficiency and ensure that temperature of each part of mold drops to a reasonable range.

Through experiment, thermal imaging technology successfully revealed problems in cooling process. When thermal imager was used for the first time to monitor cooling process of mold, it was found that surface temperature of mold after spraying did not drop to 150℃ as expected, especially in pin area, where temperature drop was obviously insufficient. Through analysis of thermal imaging images, it is clearly shown that temperature in pin area is always maintained at around 200℃, which is much higher than target value of 150℃, resulting in insufficient cooling of metal material in this area, which in turn causes stress concentration. This excessive temperature directly leads to local cracking of parts, and this problem recurs during production process, seriously affecting quality and production efficiency of parts. As shown in Figure 4:

 

In response to uneven cooling problem reflected in thermal imaging image, production team rectified mold cooling system. By adjusting cooling channel layout of pin area, flow of coolant was increased, and temperature control strategy of coolant was re-optimized to ensure that pin area can be fully cooled. After rectification, thermal imager was used again to monitor same area, results showed that temperature drop in pin area was in line with expectations and successfully dropped to around 150℃. This change proves that adjustment of cooling system effectively improves cooling efficiency of this area.
Cooling system after rectification not only solved problem of excessive temperature at pin part, but also effectively avoided cracking of parts caused by excessive temperature. Through subsequent production verification, cooling process of mold monitored by thermal imaging technology was more uniform, and quality of parts was significantly improved. Finally, this experiment verified important role of thermal imaging technology in discovering cooling system problems and improving production quality, and provided effective technical means for solving similar problems in the future. Specific experimental results are shown in Figure 5

 

Pins on die-casting mold play multiple roles in positioning, fixing, guiding, ejecting, cooling, exhausting in high-pressure casting mold to ensure efficient operation of mold and quality of casting. It is also a place where it is easy to miss when controlling mold temperature. In addition to pins, cooling on the inside of slider connection is also a place where mold waterway and spraying are not easy to handle. During experiment, it was found that temperature at slider connection on mold was high. Temperature before spraying was 299℃ and after spraying was 285℃. Data for a whole day were compared as shown in following figure (Figure 6 is before spraying and Figure 7 is after spraying).

 

Through data analysis and mold abnormality inspection, it was found that cooling water interface inside mold leaked, resulting in mold temperature not being able to be effectively reduced to a reasonable range in a timely manner. Through maintenance, it was improved. Figures 8 and 9 are improved data.

 

Temperature trend after Sp1 improvement

 

This study successfully solved problem of component cracking caused by uneven cooling in die-casting production by introducing a mold temperature control system. Experimental results show that mold temperature after spraying should be quickly reduced to about 150℃, but before use of thermal imaging technology, temperature of pin part was still maintained at 207℃, which was much higher than standard requirements, which directly led to frequent cracking of parts during production process. Through thermal imaging technology, problems of cooling system in this part were discovered in time, then cooling system was adjusted in a targeted manner. Cooling effect of adjusted mold was significantly improved, and temperature of pin part was successfully reduced to 156℃, eliminating cracking problem.
Experimental data further verified effectiveness of mold temperature control system in improving quality of die casting, especially in ensuring uniform reduction of mold temperature and optimizing cooling process. Through precise temperature monitoring and timely adjustment, this study not only improved production efficiency, but also significantly reduced quality defects caused by improper temperature control. Key data of experimental results, such as temperature of pin part dropped from 207℃ to 156℃, provided a reliable basis for further optimizing mold temperature control system, proving important role of thermal imaging technology in mold temperature monitoring and control, and it can be predicted in advance based on temperature changes of each mold during production that if no human intervention is added during shutdown period, it will take about 7 molds to restore normal production status (as shown in Figure 10). Based on this, temperature of key parts can be appropriately increased after shutdown to reduce hot mold time and reduce production capacity loss. This improvement plan effectively improves quality of die-cast parts and provides valuable experience for application of temperature control technology in die-casting production process.
Temperature change trend of pin after spraying after adjustment (6 hours)