In the manufacturing industry, sand casting remains a pivotal process for producing complex parts, especially for applications in automotive, agricultural machinery, and industrial pump valves. As a researcher and engineer focused on advancing foundry technologies, I have observed that traditional sand casting lines often suffer from inefficiencies such as unstable mold transportation, low recycling of auxiliary equipment like flasks and weights, high labor intensity, and suboptimal production environments. These challenges directly impact the quality and cost-effectiveness of sand casting parts. To address these issues, I embarked on designing a fully automatic horizontal parting molding line tailored for sand casting parts, aiming to enhance automation, improve spatial fluency, and boost productivity. This article details the comprehensive design, key mechanisms, control system, and practical application of this line, emphasizing its role in optimizing the production of sand casting parts.
The design task was driven by specific performance indicators from a foundry producing automotive wheel hubs and clutches as sand casting parts. The workshop spans 140 m × 24 m, with sand flask dimensions of 610 mm × 610 mm × 280–400 mm and 570 mm × 670 mm × 360–560 mm, corresponding to average part weights of 20 kg and 40 kg, respectively. Operating on a two-shift, 8-hour daily schedule for 300 days a year, the line needed to achieve a yield rate of 90%, adjustable sand mold height for varying flask thicknesses, and an annual capacity of 12,000 tons (equivalent to 440,000 molds per year). My goal was to develop a layout that minimizes resource waste, reduces human intervention, and ensures smooth logistics for sand casting parts production. The overall planning involved production line design, equipment zoning, and auxiliary area arrangement, adhering to principles of quality, low consumption, high efficiency, and minimal pollution.
The layout of the fully automatic horizontal parting molding line is critical for seamless operation. I designed a configuration with four conveyor lines: the first for pouring, the second for mold ejection transition, and the third and fourth for cooling. Two identical horizontal parting molding machines, capable of adjusting sand mold thickness, are integrated with sand storage and conveyor systems to enable full automation. The line includes key components such as a sand handling system with belt conveyors and bucket elevators for recycling used sand, a molding system for shape formation, and mechanisms for flask and weight handling. The logistics flow ensures that sand casting parts move efficiently from molding to pouring, cooling, and shakeout. Below is a table summarizing the main design parameters of the line:
| Parameter | Value | Description |
|---|---|---|
| Workshop Area | 140 m × 24 m | Total space for the production line |
| Sand Flask Dimensions | 610 mm × 610 mm × 280–400 mm; 570 mm × 670 mm × 360–560 mm | For automotive wheel hubs and clutches as sand casting parts |
| Annual Capacity | 12,000 tons (440,000 molds) | Target output for sand casting parts |
| Yield Rate | 90% minimum | Quality requirement for sand casting parts |
| Operating Schedule | Two shifts, 8 hours each, 300 days/year | Production timeline |
| Key Mechanisms | Molding system, flask/weight converter, clamping device, etc. | Components enabling automation |
The workflow of the line is automated to handle sand casting parts from start to finish. It begins with the molding system initiating a sand supply signal, followed by horizontal parting and molding. After molding, a bottom plate clamping mechanism positions the sand mold on the first conveyor line. A flask and weight conversion device then places reusable flasks and weights onto the mold for pouring. The mold is transported to a pouring platform for automated pouring, then cooled on subsequent conveyors. After cooling, the flask and weight are removed and recycled, and the sand mold is pushed into a shakeout machine for separation of sand casting parts and sand. The used sand is recycled via a belt conveyor system, while the parts are cleaned and output. This cyclic process ensures continuous production of sand casting parts. The automation reduces human labor and minimizes errors such as misalignment or sand spillage.
To achieve this, I designed several key mechanical mechanisms that are integral to the line’s performance. The molding system consists of upper and lower molding modules, a pushing mechanism, and sand cylinders. It uses compressed air to shoot sand into flasks and employs hydraulic cylinders for compaction. The system’s adjustability allows for different mold thicknesses, catering to various sand casting parts. The force during compaction can be described by the formula: $$F = P \times A$$ where \(F\) is the compaction force, \(P\) is the hydraulic pressure, and \(A\) is the area of the cylinder. This ensures uniform density for sand casting parts.
The flask and weight conversion device is pivotal for reusing auxiliary equipment. It comprises two lifting cylinders, brakes, and a roller chain drive. When activated, the cylinders lower clamping arms to grip flasks and weights from the second conveyor line and transfer them to the first line for placement on molds. The positioning accuracy is enhanced by alignment pins and sensors, reducing misalignment risks for sand casting parts. The device’s motion can be modeled with kinematic equations. For instance, the vertical displacement \(y\) of the lifting cylinder over time \(t\) is: $$y = v_0 t + \frac{1}{2} a t^2$$ where \(v_0\) is initial velocity and \(a\) is acceleration, ensuring precise handling of flasks for sand casting parts.
The bottom plate clamping and positioning device ensures stable transport of sand molds. It uses a gear-driven mechanism with four clamping arms actuated by a pneumatic cylinder. When a sensor detects a mold, the cylinder rotates gears to clamp the bottom plate. The clamping force \(F_c\) can be calculated as: $$F_c = \tau \times r$$ where \(\tau\) is the torque from the cylinder and \(r\) is the gear radius. This design accommodates different plate distances, crucial for varied sand casting parts.
The automatic conveying unit includes four welded steel rail tracks, bottom plate carts, a bottom plate conversion device, and a mold ejection device. The bottom plate conversion device uses servo motors and cylinders to transfer plates between conveyor lines, with dampers and limit switches ensuring precise positioning. The mold ejection device employs chain drives to push cooled molds into a vibrating conveyor for shakeout. The speed of conveyance \(v\) for sand casting parts can be optimized using: $$v = \frac{d}{t}$$ where \(d\) is the distance between stations and \(t\) is the cycle time, balancing efficiency and stability. The used sand recovery line features belt conveyors driven by motors to collect and transport spilled sand from molding, pouring, and shakeout processes, promoting recycling for sand casting parts production.
In terms of control system design, I implemented a Programmable Logic Controller (PLC)-based system to coordinate all mechanisms. The core is a Mitsubishi FX5U series CPU, with a Weintek touchscreen for human-machine interface. Communication uses N:N network configuration over RS-485 for connecting the molding system, and CC-LINK for remote I/O devices like sensors and actuators. The control logic ensures sequential operation, with interlocking between steps to prevent faults. For example, after molding, a signal triggers the clamping device, and upon completion, the flask converter activates. The PLC program uses ladder logic to manage inputs (e.g., sensors, buttons) and outputs (e.g., motors, valves). Below is a table summarizing key I/O addresses in the PLC system for controlling sand casting parts production:
| Input Address | Function | Output Address | Function |
|---|---|---|---|
| X0 | Manual/Auto Mode | Y10 | Mold Ejection Forward |
| X3 | Single/Joint Operation | Y20 | Flask/Weight Advance |
| X4 | Emergency Stop | Y24 | Flask/Weight Brake |
| X11 | Sand Shakeout Belt Monitor | Y30 | 1st Bottom Plate Converter Push Cylinder |
| X21 | Flask/Weight Device Fault | Y37 | Shakeout Belt 1 |
| X26 | Mold Ejection Monitor | Y42 | 2nd Bottom Plate Converter Push Cylinder |
| X36 | Sand Recovery Operation | Y46 | Shakeout Belt 2 |
| X40 | Line Transport Inhibit | Y54 | Molding 1 Ejection Permit |
| X41 | Shakeout Belt Overload | Y56 | Auto Operation Indicator |
| X42 | Pouring Emergency Stop | Y57 | Molten Metal Wait |
| X44 | Molding Emergency Stop | Y62 | Line Transport Active |
| X51 | Molding System Ejection End | Y67 | Sand Return System Start |
The control flow is designed to optimize the production of sand casting parts. Upon start, the molding system checks sand level and initiates molding. After molding, the bottom plate clamping device secures the mold, and the ejection device pushes it to the first conveyor. The bottom plate converter then moves it to the flask/weight station, where flasks and weights are attached. The mold proceeds to pouring, cooling, and then to the shakeout area. The flask/weight converter recycles the auxiliary equipment, and the cycle repeats. The PLC uses timers and sensors to synchronize steps, with feedback loops ensuring accuracy. For instance, the position control for the bottom plate converter can be modeled with a PID controller: $$u(t) = K_p e(t) + K_i \int e(t) dt + K_d \frac{de(t)}{dt}$$ where \(u(t)\) is the control output, \(e(t)\) is the position error, and \(K_p\), \(K_i\), \(K_d\) are gains. This enhances stability during transport of sand casting parts.
In practical application, the line was implemented in a foundry to produce automotive wheel hubs and clutches as sand casting parts. The setup includes the molding system, pouring and cooling conveyors, flask/weight converter, bottom plate converters, an automated pouring machine, mold ejection device, shakeout machine, apron conveyor, and sand recovery lines. Testing showed that the line operates smoothly, with minimal human intervention. The automation allowed for a significant reduction in workforce: from 32 workers in traditional semi-automatic lines to only 4 workers for two shifts, while meeting daily targets of 640 wheel hubs and 1,040 clutches as sand casting parts. The yield rate reached approximately 99.4%, exceeding the 90% target, and the production environment improved due to enclosed sand recycling and dust control. The table below compares performance before and after implementing the automatic line for sand casting parts:
| Aspect | Traditional Semi-Automatic Line | Fully Automatic Horizontal Parting Line |
|---|---|---|
| Workers Required | 32 | 4 |
| Workspace Utilization | 87.3% | 65.2% |
| Daily Capacity (Parts) | 28.8 tons equivalent | 46.4 tons equivalent |
| Yield Rate for Sand Casting Parts | ~90% | ~99.4% |
| Labor Intensity | High | Low |
| Sand Recycling Efficiency | Moderate | High |
The economic and operational benefits are substantial. The line reduces labor costs by over 85%, minimizes material waste through flask and weight recycling, and cuts downtime due to its robust design. The spatial layout efficiency, achieved by compact mechanisms and automated transfers, allows for more sand casting parts to be produced in a smaller area. Additionally, the PLC-based control enables real-time monitoring and adjustments, further optimizing the production of sand casting parts. For example, the cycle time \(T_c\) for producing one sand casting part can be expressed as: $$T_c = T_m + T_t + T_p + T_c + T_s$$ where \(T_m\) is molding time, \(T_t\) is transport time, \(T_p\) is pouring time, \(T_c\) is cooling time, and \(T_s\) is shakeout time. With automation, \(T_t\) and \(T_s\) are reduced, boosting overall throughput.
From a technical perspective, the integration of mechanical and control systems is key. The molding system’s hydraulic circuits—for upper/lower frame lifting, flask sliding, mold ejection, probe mechanisms, and合模—are managed via solenoid valves, with servo motors driving gear pumps for precise actuation. The pneumatic system includes cylinders for sand shooting and mold release, controlled by valves and regulators. Sensor feedback, such as from displacement sensors, ensures each step meets set parameters for sand casting parts. The energy efficiency can be analyzed using power consumption models. For instance, the total power \(P_{total}\) for the line is: $$P_{total} = \sum (P_{motor} + P_{hydraulic} + P_{pneumatic})$$ where each component’s power is optimized through variable frequency drives and pressure controls.
Looking ahead, this design offers a scalable template for modernizing foundries. The principles can be adapted to other sand casting parts with different sizes or materials by adjusting mechanism dimensions and control parameters. Future enhancements could include IoT connectivity for predictive maintenance or AI-based quality inspection of sand casting parts. However, the current system already represents a significant leap in automation, addressing common pain points in sand casting production.
In conclusion, the fully automatic horizontal parting molding line I designed effectively tackles inefficiencies in traditional sand casting lines. By incorporating key mechanisms like the flask/weight converter and precise clamping devices, and leveraging a PLC-based control system, it achieves high automation, stability, and productivity for sand casting parts. The practical results demonstrate improved yield rates, reduced labor, and better resource utilization, making it a viable solution for foundries seeking to upgrade their operations. This work underscores the importance of integrated design in advancing sand casting technology, and I believe it will inspire further innovations in the production of sand casting parts.