Introduction to several modeling methods in modern casting

Mount holds the belief that clay wet sand molding represents the most economical approach for most metal materials and mass production techniques. The foundry is equipped with the latest technological control systems, which need to be progressively integrated. The wet sand control technology can consistently deliver optimal results. These control mechanisms include, for instance, sieving and separating metals, cooling recycled sand, accurately adding substances when reusing sand, and more.

Vulcan argues that the current clay wet sand molding machines perform exceptionally well. They operate at speeds previously unattainable just two years ago, requiring stringent manufacturing standards and allowing for minimal variance in the wet sand molds. Combined with their high efficiency and precise sand control apparatus, clay sand plays a crucial role in maintaining the form of both ferrous and non-ferrous alloys.

Macler Assoc suggests that when comparing vertical and horizontal classifications in wet sand molding, for mass-producing small to medium-sized gray iron or ductile iron castings, the direct and straight type predominates. It boasts lower equipment costs, high-speed molding, fewer personnel needed, and minimal variation in compactness. However, the vertical parting process is constrained in terms of gating schemes, risers, and complex core usage, as well as the application of filters, cold iron, casings, and cores. Additionally, when casting alloys with high fluidity, the metal static pressure tends to be relatively high, making it easier for the metal to penetrate the sand.

In the production of non-ferrous alloy castings, a large-scale production of various types of alloy castings has been designed based on the characteristics of the vertical parting molding method, which is now gaining popularity. Nevertheless, before achieving a very high level of mass production with this technique, the traditional metal casting method remains advantageous when producing large quantities of aluminum alloy castings.

Macler Assoc also believes that the horizontal type of wet sand casting method is one of the favorable molding methods for medium and small batch casting factories, whether it’s the upper, lower, or double-sided mold types, particularly for the production of complex castings. The pattern can be changed within one cycle, enabling efficient production over both short and long durations. However, manual operations require mechanization. To ensure the production of castings with excellent surfaces and high dimensional accuracy, the entire set of equipment needs modification. When selecting the warm sand molding method, the following considerations must be taken into account:

â—† There must be a molding machine capable of creating high-quality molds with uniform hardness. â—† The pattern can be quickly changed. â—† Mechanization of loading and unloading the lower core and mold.

Macler Assoc notes that various techniques have been adopted to achieve a uniform shape. Several automatic double-sided molding machines employ sandblasting and compaction. In such cases, to achieve uniform mold density, sandblasting and compaction are utilized, with the sandblasting direction ideally perpendicular to the board. There is also a top-and-bottom molding machine that uses micro-vibration and compaction to ensure uniform mold density. Furthermore, to exert a strong impact force during sand filling, high-compression gas is employed. However, obtaining uniform mold hardness involves multiple methods, and no single method can address all molding requirements. In selecting a molding machine, the foundry currently in use should be examined and tested alongside its own specifications to observe the outcomes.

â—† Precision Sand Casting

The primary focus of this molding method lies in the chemical-bonded mold using the cold-box method. Vulcan considers this the revival of the aluminum alloy block and cylinder head casting process. The reason being that the cylinder liner can be cast directly into the cylinder block, and the advantage of using cold iron for directional solidification can be leveraged.

This method was developed in the 1970s for casting near-net-shape castings and complex-core-shaped castings using wet sand. Nowadays, when casting complex-shaped accurate castings, the standard approach is to use the cold-box molding method. Moreover, it is suitable for a broader range of alloys than sand casting. Due to innovations in resin chemistry and molding equipment, it is now possible to cast high-quality parts at a lower cost, utilizing advanced liquid pumps and robotic automated production lines. Further equipment enhancements reduce labor needs, producing high-quality, low-cost castings. The cold-box molding machine is a significant variant of the core-making machine. Certain models can create molds on both sides while simultaneously forming the lower mold, while another variant uses two sets of molding machines, with one set forming the type and the other set the core.

To enhance precision, these molding machines minimize parting-line flash and are characterized by compacting the mold throughout the process. Large-scale molding machines are fully hydraulically driven for smooth and reliable operation. They are equipped with robots to handle tasks such as coating the mold, drying, inserting the core, bonding, and boxing. Thanks to these devices, labor requirements are reduced, and the highest quality and productivity are ensured. The shape of the cold-box mold not only impacts the surface quality of the casting and cleaning operations but also influences the proper assembly of the core and the position where the core fluidizes the sand in the sanding head. Design is critical.

According to Macler Assoc, the cold-box molding machine employs several sand-shooting techniques. Most of these machines shoot sand at low pressure and high volume, allowing sand to be shot after each cycle. Two or three machinery factories do not fluidize the sand but instead use the "extrusion method," including patented sandblasting and low-volume high-pressure sandblasting. Some mechanical factories believe that extrusion is useful when making complex molds, as it allows the sand to flow easily. For these two techniques, it’s best to conduct trial comparisons using their own patterns and select the optimal method.

The cold-box molding method can produce complex molds with highly accurate dimensions, but the cost of the mold and the sand binder and catalyst are higher than those for wet sand molds. Additionally, the speed of the cold-box molding method is slower.

â—† Easy Mold Casting

Vulcan's lost-foam casting has evolved due to advancements in equipment and materials, with expanding applications. New technologies such as multi-directional filling points, filling sand (subsequent sand), and instant filling have improved casting quality, molding speed, and cost-effectiveness.

The advantages of lost-foam casting include the ability to use foamed molds without a slight tilt or twist, and sometimes the twist can help shape complex forms, providing design freedom. Additionally, the weight of the casting can be reduced, eliminating or minimizing the need for machining, and enabling casting without cores. Innovations in equipment, new developments in components, coatings, and filling media have led to increased casting quality and production efficiency, thereby expanding the market.