In the competitive world of iron foundries, selecting the right molding process is paramount. It directly dictates the precision, surface finish, and production efficiency of your castings. While both Resin Sand Casting and Shell Mold Casting (using Coated Sand) utilize resin as a binder, their production methodologies, outcomes, and ideal use cases are fundamentally distinct.

1. Resin Sand Casting Process

1. Mixing: Raw sand (e.g., silica) is thoroughly mixed with liquid resin (furan or phenolic) and a curing agent (acid catalyst).

2. Ramming: The mixture is filled into molds (wood, plastic, or metal patterns) and compacted pneumatically or hydraulically.

3. Curing & Stripping: The sand cures at ambient temperature via chemical reaction, after which the mold is stripped.

4. Core Setting & Closing: Cores are placed, and the mold is closed for pouring.

5. Pouring & Shakeout: After pouring molten iron, the casting cools (12-72 hours), then is extracted via a shakeout machine.

6. Inspection: Critical checks for roughness, dimensions, and mechanical properties are conducted.

Key Outcomes & Considerations

• Dimensional Accuracy: High (Grade CT9-CT12), better than green sand but less than shell molding.

• Surface Quality: Good (Ra50-Ra100), though minor sand adhesion may occur.

• Efficiency: Moderate. Curing time limits line speed.

Best Applications

• Iron Casting Types: Machine tool beds, housings, columns, worktables.

• Scenarios: Large/medium castings, single-piece or small-batch production.

→ Click to view this tech’s production process

2. Coated sand shell casting

Shell molding utilizes heat to activate the binder for superior precision.

1. Coating: Sand is pre-coated with thermoplastic phenolic resin and a hardener (Hexamine) at the supplier's facility.

2. Shooting: The coated sand is shot into a heated metal die (180°C - 250°C).

3. Heat Curing: The sand forms a thin, hard shell as the resin melts and cures upon contact with the hot pattern.

4. Ejection & Assembly: The shell is ejected, assembled, and placed in a flask.

5. Pouring: Molten iron is poured directly (approx. 1400°C). The shell has high hot strength.

6. Knockout & Finishing: After cooling (7-24 hours), the box is opened for finishing.

7. Inspection: Critical checks for roughness, dimensions, and mechanical properties are conducted.

Key Outcomes & Results

• Dimensional Accuracy: Very high (Grade CT7-CT9), with excellent repeatability.

• Efficiency: Very high, ideal for automated mass production.

Best Applications

• Iron Casting Types: Engine blocks, cylinder heads, gear housings, precision valves.

• Scenarios: High-volume production, precision castings, complex internal cavities.

→ Click to view this tech’s production process

3. Core Comparison Summary

4. How to Choose for Your Iron Foundry Project?