Application of Fan-Shaped Servo-Controlled Pouring Machines in Vertical Parting Boxless Die-Casting Automatic Molding Lines

Release time:

2014-07-21

Baoding WeLL Foundry Machinery Co., Ltd. Chang Xinping (excerpted from "Foundry Equipment," April 2014 issue)

1. Preface

In recent years, an increasing number of manufacturers have been adopting the ZZ416 and ZZ418A vertical-parting, boxless, die-casting automatic molding lines for producing small- and medium-sized castings. Our factory sells over a hundred such lines annually, serving a wide range of industries—including automotive, building materials, construction machinery, metallurgical and mining equipment, and more. These vertical-parting, boxless, die-casting automatic molding lines feature a high degree of automation and exceptional efficiency; therefore, the selection of the pouring method has become a critical factor in maximizing the performance of the production line. To address this need, our factory has developed a fan-shaped servo-controlled pouring machine specifically designed to work with vertical-parting, boxless, die-casting automatic molding lines.

Previously, due to the lack of standardized casting equipment, casting methods on the production line varied widely. The simplest method involved manual ladle pouring, with three or four workers taking turns to pour molten metal. Because the skill levels of the pouring workers differed, the defect rate of castings rose significantly. Moreover, spills and mold explosions easily led to burns, and the work was physically demanding, with workers exposed to smoke and intense heat in a poor working environment. Later, with technological advancements, the casting method evolved to the rail-guided ladle pouring system, eliminating the need for manual ladle handling. While this change reduced the physical strain on pouring workers and represented a significant step forward, it still failed to address the fundamental issue of smoke and heat exposure during casting. Another type of casting machine is the bottom-pouring machine (or one equipped with insulation), which features a simple structure and has its spout located at the bottom of the pouring ladle, providing excellent slag removal capability. However, as the liquid level within the ladle fluctuates, the filling pressure also varies accordingly. Additionally, the plunger rod remains immersed in molten metal for extended periods, resulting in poor durability and frequent damage, thus increasing maintenance workload. Furthermore, since the spout is positioned at the bottom, operators cannot visually monitor the pouring process, leading to poor operability. This type of machine is suitable for casting materials other than ductile iron. On the other hand, the fan-shaped servo-controlled casting machine—commonly referred to as the "fan-shaped casting machine"—is easy to operate and can achieve continuous inoculation and constant-pressure pouring, meeting the casting requirements of various types of cast iron, especially for the production of ductile iron.

2. Characteristics of the fan-type casting machine

The fan-shaped casting machine mainly consists of: a crucible body, a random crucible cover, a casting main unit, a flow-controlling inoculation device, an electrical control system with an operator’s console, and a waste liquid dumping mechanism. The electrical control system employs a PLC, a touch-screen display, servo controllers, and frequency converters, enabling the setting and display of various operating parameters, monitoring of running status and fault indication, and real-time diagnostic alarms. The control system features a simplified Chinese menu. The main specifications are available in three models: 600 kg, 800 kg, and 1000 kg. Casting speed: 0–3.5 kg/s; Repeatability accuracy of weight: ≤0.5%.

Features of the fan-shaped casting machine:

1. The pouring basin is fan-shaped, and the molten metal flows along the axis of the fan shape, enabling constant-pressure casting.

2. The pouring ladle tilting is driven by servo control, with the tilting angle and speed following a typical flow-time curve to achieve optimal casting results and high repeat positioning accuracy.

3. Follow the “slow—fast—slow, rapid package retraction” procedure to achieve quantitative pouring at the optimal process pouring speed.

4. Equipped with manual, automatic, and teach-in functions, the machine allows users to input and store different casting parameters, enabling the casting of various products. Parameter adjustments can also be made directly on the operator’s console. 5. The casting machine can move in both the X and Y directions, controlled by a variable-frequency drive system.

3. Operating conditions under different scenarios

The operating conditions for the fan-shaped casting machine are described below: On the vertical-parting, boxless die-casting line, the production cycle is 12–20 seconds per mold, with each mold containing metal liquid weighing 10–25 kg. The temperature drop of the fan-shaped casting machine is 4–6°C per minute. The ZZ416 and ZZ418A vertical-parting, boxless die-casting automatic molding lines can achieve a pouring time of 6–8 seconds.

1. For gray iron and alloy cast irons, as long as the pouring temperature meets the requirements of the casting process, continuous pouring is possible. You can either completely empty the metal liquid from the fan-shaped ladle and then refill it with fresh metal, or you can leave a small amount of metal remaining before adding new metal. In practical operation, heat the molten metal to a temperature at least 100–120°C above the minimum pouring temperature. Each ladle of molten metal can be poured for 15–24 minutes. When the volume of metal per mold is 10 kg, at a pouring cycle of 18 seconds per mold (200 molds per hour), in 15 minutes—900 seconds—the number of molds that can be produced is 50, requiring 500 kg of molten metal. In this case, a 600-kg ladle would be ideal. If the volume of metal per mold is 10 kg, at a pouring cycle of 13 seconds per mold (277 molds per hour), in 15 minutes—900 seconds—the number of molds that can be produced is 70, requiring 700 kg of molten metal. Here, an 800-kg ladle would be more appropriate. When the volume of metal per mold is 15 kg, in 15 minutes—900 seconds—the number of molds that can be produced is 70, requiring 1050 kg of molten metal; in this scenario, a 1000-kg ladle would be ideal. The above calculations indicate that four ladle turnovers per hour are required. Alternatively, when the volume of metal per mold is 25 kg, at a pouring cycle of 18 seconds per mold (200 molds per hour), in 12 minutes—720 seconds—the number of molds that can be produced is 40, requiring 1000 kg of molten metal. In this case, a 1000-kg ladle should be used, and a ladle turnover would need to occur every 12 minutes, meaning five ladle turnovers per hour. Under normal conditions, each ladle turnover takes between 70 and 120 seconds, during which the machine must be stopped and allowed to idle.

2. For ductile iron castings, the allowable pouring time for ductile iron is 8 to 10 minutes. It is required that the pouring time per batch be as short as possible; at the same time, the superheat temperature of the molten metal should not be too high. At a molding speed of 12 seconds per mold, with a molten metal charge of 10 kg per mold, the number of molds that can be processed in 600 seconds is 50, requiring a total of 500 kg of molten metal. In this case, a 600-kg ladle would be appropriate. At a molding speed of 15 seconds per mold, with a molten metal charge of 15 kg per mold, the number of molds that can be processed in 600 seconds is 40, requiring a total of 600 kg of molten metal. In this case, an 800-kg ladle would be more suitable. Under the same casting weight conditions, the molding and pouring speeds for ductile iron castings should be faster. The ladle size for ductile iron castings should be one grade smaller than that for gray iron castings. During operation, if the pouring time or pouring temperature after spheroidization falls below the process requirements, pouring should be immediately halted. The ladle should then be reversed, allowing the molten metal inside to flow through the waste-gate channel into the waste-metal container, from where it is transferred via a transfer cart back to the melting furnace.

3. Malleable cast iron, primarily used for the production of malleable steel fittings, is characterized by high production volumes and the use of sand cores (molding line cycle time: 15–20 seconds). Each mold produces lightweight castings, with a single mold requiring 10–15 kg of molten iron. The pouring temperature must be ≥1440℃. Under normal conditions, the molten metal is superheated to 1590℃ and then transferred to the pouring machine at a temperature of 1560℃. Pouring begins when the superheat reaches 120℃. When the amount of molten metal per mold is 10 kg, it can be poured continuously for 20 minutes, with a casting cycle of 15 seconds per mold. At this rate, 80 molds can be produced in 1200 seconds, requiring 800 kg of molten metal; therefore, an 800-kg ladle is recommended. To meet hourly demand, 3 ladles of molten iron need to be poured each hour. If the amount of molten metal per mold is increased to 15 kg, with a casting cycle of 15 seconds per mold, the pouring duration extends to 15 minutes, yielding 60 molds in 900 seconds. In this case, 900 kg of molten metal is required, making a 1000-kg ladle more suitable. Considering all factors, an 800-kg ladle is the most appropriate choice for casting malleable steel fittings. Under these conditions, 3 to 4 ladles of molten iron need to be poured each hour.

The fan-shaped casting machine features a detachable ladle with two ladle bodies that alternate in use for convenient replacement. Each shift lasts 10 hours, and each ladle body can be used continuously for 50 to 80 days (during each shift, it is necessary to clean the slag adhering to the ladle walls and the liquid outlet).

4. The effectiveness of using a fan-shaped pouring machine

According to user feedback on usage, the productivity of vertical-parting boxless die-casting lines equipped with fan-shaped pouring machines is approximately 15% higher than that of manual pouring. Moreover, casting defects caused by pouring have decreased by 5% to 8%. The servo-controlled tilting mechanism of the fan-shaped pouring machine ensures a smooth flow of molten metal, significantly reducing iron dross and overflow at the gate. As a result, the magnetic separator at the sand-processing stage now produces 200–300 kg less broken iron dross per day. Assuming an annual working period of 250 days and maintaining the same production volume, this translates into a reduction of 50–75 tons of molten metal melted annually. In terms of manpower, manual pouring requires 3–4 workers per line, whereas pouring with a pouring machine only needs 1–2 workers, resulting in a labor-saving of 1.5 workers. This greatly reduces labor intensity, eliminates exposure to smoke and heat, and minimizes the risk of burns. Today, when upgrading and introducing new vertical-parting boxless die-casting lines, the fan-shaped pouring machine has become the preferred choice for pouring operations.

Keywords:

Previous item

Zhu’er Casting Machine: Showcases Top-Grade Vertical Automated Production Line at the Exhibition

The factory’s greening efforts have yielded abundant results.

Next one