In modern manufacturing, sand casting remains one of the most prevalent methods for producing complex metal components, particularly in industries such as automotive, agriculture, and machinery. The efficiency, cost-effectiveness, and quality of sand casting processes are heavily dependent on the design and integration of molding lines. Traditional sand casting lines often suffer from issues like unstable mold transportation, low recycling rates of auxiliary equipment, high labor intensity, and suboptimal production environments. To address these challenges, we have developed a fully automated horizontal parting molding line specifically for sand casting applications. This system integrates advanced mechanical structures, precision control systems, and automated material handling to enhance productivity, reduce human intervention, and improve the overall sustainability of the sand casting process. In this article, I will detail the design, implementation, and performance analysis of this innovative molding line, emphasizing key aspects such as layout optimization, critical mechanism design, and control system integration. Throughout the discussion, the term ‘sand casting’ will be frequently referenced to underscore its centrality to this work.
The design of the fully automated horizontal parting molding line was driven by specific performance requirements derived from industrial needs. The target production environment is a casting workshop measuring 140 meters by 24 meters, focusing on two types of sand casting products: automotive wheel hubs and clutches, both made from HT250 cast iron. The sand molds used have dimensions of 610 mm × 610 mm × 280–400 mm and 570 mm × 670 mm × 360–560 mm, with average weights of approximately 20 kg and 40 kg, respectively. Operating on a two-shift system of 8 hours each for 300 days per year, the line aims to achieve an annual output of 12,000 tons (equivalent to 440,000 molds per year) and a product yield rate of over 90%. Additionally, the system must accommodate adjustable mold heights to suit different sand box thicknesses, ensuring versatility in sand casting operations. The overall planning prioritized optimal resource utilization, minimal energy consumption, high efficiency, and reduced environmental impact, leading to a comprehensive layout that includes equipment zoning, material flow management, and auxiliary area design.
The overall layout of the automated horizontal parting molding line for sand casting is structured around four main conveyor lines to facilitate seamless material flow. The first line handles pouring operations, the second serves as a transition for mold ejection, while the third and fourth lines are dedicated to cooling processes. Key components include two identical horizontal parting molding machines, which enable adjustable mold thickness and communicate with sand storage and conveyor systems for automated control. Sand handling involves belt conveyors and bucket elevators that transport raw and recycled sand through a processing line to a sand reservoir, ready for molding. The molding system, after completing sand compacting, ejects molds onto the first conveyor line, where mechanisms like clamping devices, box and weight conversion units, and plate transfer systems coordinate to apply jackets and weights for pouring. After pouring, molds move to cooling zones, and subsequent processes involve jacket and weight removal, mold breaking, and casting extraction. A dedicated sand recovery system, located in pits beneath key stations, collects and recycles used sand, promoting sustainability in sand casting operations. This layout minimizes spatial conflicts, enhances production fluency, and supports the high-volume demands of sand casting.
The workflow of the automated molding line for sand casting is designed as a cyclic process to ensure continuous operation. It begins with the molding system initiating a sand supply signal, followed by horizontal parting and compacting of sand into molds. Once molding is complete, the molds are ejected onto the first conveyor line, and clamping mechanisms secure the base plates for stability. Jackets and weights are then applied via conversion devices, and the prepared molds are transferred to pouring stations for automated casting. After pouring, the molds undergo cooling on designated lines, followed by jacket and weight removal, mold ejection into vibrating conveyors for sand separation, and final casting retrieval. Sand recovery occurs concurrently, with fallen sand transported back to the processing line. This integrated workflow, controlled by programmable logic controllers (PLCs), ensures that each step in the sand casting process is synchronized, reducing downtime and maximizing efficiency. Key steps include mold positioning, pouring, cooling, and recycling, all optimized for the repetitive nature of sand casting production.
Critical mechanical structures are essential for the reliability and automation of the sand casting molding line. The molding system itself comprises upper and lower molding modules, pushing mechanisms, and sand cylinders, all controlled by hydraulic and pneumatic actuators. For instance, oil cylinders and electromagnetic valves manage operations such as mold closing, sand shooting, and compaction, allowing for manual adjustments via configuration software to suit different mold geometries and sand thicknesses in sand casting. The jacket and weight conversion device uses升降 cylinders and clamping mechanisms to handle jackets and weights, ensuring precise positioning through sensors and alignment pins. This device facilitates the cyclic use of jackets and weights, which is crucial for cost reduction in sand casting. The base plate clamping and positioning mechanism employs gear-driven arms actuated by cylinders to secure plates during transport, preventing misalignment and improving stability in sand casting processes. Additionally, automatic transfer units, including base plate conversion devices and mold ejection systems, utilize servo motors and chain drives to move molds between conveyor lines, with dampers and limit switches ensuring accurate positioning. These mechanisms collectively address common issues in sand casting, such as mold shifting and resource wastage, by enhancing mechanical precision and automation.
To illustrate the design parameters and performance metrics of the sand casting molding line, the following table summarizes key aspects:
| Parameter | Value | Description |
|---|---|---|
| Annual Output | 12,000 tons | Total production capacity for sand casting |
| Mold Dimensions | 610×610×280–400 mm, 570×670×360–560 mm | Sand box sizes used in sand casting |
| Mold Weight | ~20 kg and ~40 kg | Average weight per sand casting mold |
| Operation Schedule | 2 shifts × 8 hours, 300 days/year | Work schedule for sand casting line |
| Target Yield | >90% | Acceptable product rate in sand casting |
| Adjustable Mold Height | Yes | Flexibility for different sand casting requirements |
The control system for the automated sand casting molding line is centered on a PLC-based architecture, which coordinates all mechanical and electrical components. Using a Mitsubishi FX5U series CPU as the main processor, the system integrates with touchscreens and remote I/O modules via CCLINK and RS-485 communication protocols. Input devices include control buttons, sensors, and limit switches, while output devices drive servos, motors, heaters, and electromagnetic valves. The hydraulic system consists of multiple circuits for operations like mold升降 and compacting, with servo motors driving gear pumps to achieve precise movements. For example, the flow rate of the gear pump can be described by the equation: $$Q = n \times V$$ where \(Q\) is the flow rate (in mL/min), \(n\) is the rotational speed (in rpm), and \(V\) is the displacement per revolution (in mL/r). In this sand casting application, with a pump displacement of 32 mL/r and a motor speed of 2400 rpm, the flow rate is calculated as: $$Q = 2400 \times 32 = 76,800 \, \text{mL/min}$$ This ensures adequate hydraulic power for mold operations in sand casting. The pneumatic system, involving cylinders and valves, manages sand shooting and mold release, with timing and limit controls ensuring sequential operation. The overall control logic implements interlocking between processes, such as sand supply, molding, and ejection, to maintain synchronization and safety in sand casting production.
A portion of the I/O address allocation for the PLC in the sand casting control system is detailed below:
| Input Address | Function | Output Address | Function |
|---|---|---|---|
| X0 | Manual/Auto Mode | Y10 | Mold Ejection Forward |
| X3 | Single/Joint Operation | Y20 | Jacket/Weight Advance |
| X4 | Emergency Stop | Y24 | Jacket/Weight Brake |
| X11 | Sand Drop Belt Monitor | Y37 | Sand Drop Belt 1 |
| X21 | Jacket/Weight Device Fault | Y42 | Base Plate Transfer Push |
| X26 | Mold Ejection Monitor | Y46 | Sand Drop Belt 2 |
| X36 | Sand Recovery Operation | Y54 | Molding 1 Ejection Permit |
| X40 | Line Transfer Inhibit | Y56 | Auto Run Indicator |
| X41 | Belt Overload | Y57 | Molten Metal Wait |
| X42 | Pouring Emergency Stop | Y62 | Line Transfer Active |
| X44 | Molding Emergency Stop | Y67 | Sand Return System Start |
| X51 | Molding System Ejection End |
In practical application, the automated horizontal parting molding line for sand casting has demonstrated significant improvements over traditional methods. For instance, in producing automotive wheel hubs and clutches, the line operates fully automatically for 16 hours daily with only four workers per shift, compared to 32 workers in manual or semi-automated sand casting setups. This reduction in labor translates to lower operational costs and minimized human error. Performance analysis shows a daily output of 640 wheel hubs and 1,040 clutches, with a yield rate of approximately 99.4%, surpassing the initial target of 90%. The production area footprint was reduced by 22.1%, and overall productivity increased by about 61.11%, highlighting the efficiency gains in sand casting. Environmental benefits include cleaner workshop conditions due to integrated sand recovery and dust control systems. The following equation can be used to estimate the production efficiency improvement: $$E = \frac{(P_a – P_m)}{P_m} \times 100\%$$ where \(E\) is the efficiency gain, \(P_a\) is the automated output (e.g., 46.4 units/hour), and \(P_m\) is the manual output (e.g., 28.8 units/hour). Substituting the values: $$E = \frac{(46.4 – 28.8)}{28.8} \times 100\% \approx 61.11\%$$ This quantifies the advantage of automation in sand casting. Additionally, the use of recyclable jackets and weights, coupled with precise control mechanisms, has reduced mold damage and material waste, further optimizing the sand casting process.
The development and implementation of this fully automated horizontal parting molding line represent a significant advancement in sand casting technology. By addressing common challenges such as unstable transport, low recycling rates, and high labor dependency, the system enhances production fluency, product quality, and environmental sustainability in sand casting. The integration of mechanical innovations, like the jacket and weight conversion devices and base plate clamping systems, with a robust PLC-based control framework, ensures reliable and efficient operation. Practical results confirm that the line meets industrial demands for high-volume sand casting, with notable improvements in output, yield, and resource utilization. Future work could focus on incorporating IoT technologies for real-time monitoring and predictive maintenance in sand casting lines, further elevating automation levels. This design not only serves as a viable solution for modern foundries but also provides a reference for upgrading traditional sand casting processes, underscoring the enduring relevance of sand casting in manufacturing.