The casting molds of gravity casting are mainly divided into four types: wet mold, dry mold, surface dry mold, and self hardening mold. The selection of each casting mold needs to be determined based on factors such as the weight, structure, and quality requirements of gravity casting parts, production batch size, and workshop production conditions.
1,2,1-
The wet type gravity die casting process maintains dominance in metal forming applications due to its operational efficiency. As the most prevalent method in gravity casting manufacturing, this approach utilizes undried sand molds without hardening treatments, making it particularly suitable for high-volume production environments.
Key advantages driving its adoption by gravity casting suppliers include:
Enhanced production flexibility for diverse component requirements
Rapid cycle times supporting just-in-time manufacturing
Seamless integration with automated production lines
Cost-effective material utilization
Streamlined workflow organization for mass production
While offering significant productivity benefits, China-based foundries note characteristic challenges requiring precise control:
Higher moisture content impacting mold stability
Increased susceptibility to surface defects (sand scars, rat tails, adhesion)
Potential internal flaws (porosity, sand expansion, inclusion defects)
Industry best practices recommend this method primarily for:
✓ Mechanized production of small-to-medium gravity cast components
✓ High-volume orders requiring consistent output
✓ Projects prioritizing speed-to-market over extreme precision
Technical considerations for gdc casting implementations:
• Maintain optimal sand-to-binder ratios
• Implement real-time moisture monitoring systems
• Utilize advanced sand reclamation technologies
• Establish rigorous quality control checkpoints
Professional gravity casting services in China typically combine this method with complementary processes to address limitations. Reputable manufacturers often integrate automated sand preparation systems and advanced venting designs to mitigate defect risks while preserving production efficiency. For critical applications, many foundries recommend hybrid approaches combining wet type efficiency with secondary hardening processes.
This cost-competitive solution continues to evolve through improved material science and IoT-enabled process monitoring, maintaining its position as a fundamental technique in modern metal casting operations. Manufacturers seeking reliable gravity casting supplier partnerships should prioritize facilities demonstrating expertise in moisture control protocols and defect prevention strategies specific to wet mold applications.
When the casting has a large horizontal wall during pouring, using wet molds can easily cause sand inclusion defects, and other sand molds should be considered.
When the gravity casting is too high and the static pressure of the metal exceeds the compressive strength of the wet mold, dry sand mold or self hardening sand mold should be considered.
When placing a large amount of cold iron inside the mold, wet molds should be avoided. Due to the rusting or cooling of the cold iron, water droplets may condense and cause porosity defects after pouring. If it is necessary to use cold iron, it should be preheated in advance and poured into the mold in a timely manner after being placed in the mold.
Gravity cast parts that require a long molding process or a long waiting time for pouring should not be wet molded, as placing the wet mold for too long will air dry, reduce surface strength, and are prone to sand flushing defects.
1.2.2-The characteristics of dry casting are high strength, good fire resistance and breathability, easy to ensure casting quality, but long production cycle and high cost. Dry casting is generally suitable for single piece or small batch production of gravity casting parts, as well as large, heavy, complex shape, and high technical requirements of gravity casting parts.
1.2.3-Surface dry molding is a casting process where only the surface layer is dried and poured after the sand mold is made. It overcomes some of the drawbacks of dry casting, maintains some of the advantages of dry casting, reduces costs, and improves productivity. It is commonly used in the production of large and medium-sized gravity castings.
1.2.4-Self hardening mold is a casting mold that hardens by the chemical reaction of the molding material itself after the sand mold is made, and generally does not require baking or low-temperature baking. Its advantages are high strength and high accuracy. In recent years, the application of hard gravity castings in production has become increasingly widespread.
