Why Deformation Occurs in Lost Foam Casting and V-Process Casting, and How to Prevent It

Causes of Deformation

1.Stress-induced deformation

2.Deformation during coating application

3.Deformation during drying

4.Deformation during flasking (molding and sand filling)

5.Deformation caused by improper bonding

Solutions

1. Prevention of stress-induced deformation
Stress deformation is mainly caused by excessive moisture content inside the foam pattern, which generates high internal stress. Although the pattern may not deform during bonding, deformation often appears after drying.
To prevent this, the foam pattern should be pre-dried before bonding to remove internal moisture, allowing internal moisture content to reach equilibrium with the external environment. This eliminates internal stress and also prevents shrinkage deformation caused by moisture release.

2. Prevention of deformation during coating application
After bonding, the foam pattern may remain stable, but deformation can occur during coating application due to added weight and moisture from the coating. The increased weight reduces the structural strength and support capacity of the foam pattern.
To prevent this, special fixtures or tooling should be used when necessary, and coating should be applied while the pattern is supported by the tooling to avoid deformation.

3. Prevention of deformation during drying
During drying, coated patterns must be placed steadily and level to prevent deformation. Drying temperature should be controlled between 40 °C and 50 °C, avoiding large temperature fluctuations. Alternating wet and dry conditions caused by unstable temperatures are a major cause of deformation.

4. Prevention of deformation during flasking
Flasking deformation occurs due to uneven vibration force and amplitude of the vibration compaction table. If one side vibrates more strongly than the other, sand compaction becomes uneven, and the pattern is unevenly compressed by the sand, leading to deformation.
Uniform vibration force and amplitude are essential to ensure even sand compaction.

5. Prevention of bonding-related deformation
Bonding deformation is caused by dimensional errors during cutting and assembly, such as incorrect foam dimensions, inaccurate angles, or asymmetric bonding between curved surfaces. Strict control of cutting accuracy and bonding symmetry is required.