Casting fettling is a processing technology in which cooled and solidified castings are taken out from the mold, and excess substances other than the casting body such as surface adhering sand, cores, gating and riser systems, flash and burrs are removed. The surface of the casting is trimmed to meet the required surface quality of the casting.
Casting fettling occupies a pivotal connecting position in the entire production process.
The whole casting production process generally consists of the following procedures: raw material preparation, melting, sand mold making, pouring, shakeout and fettling after cooling. Only after secondary fettling can the castings undergo visual inspection and non-destructive testing, followed by subsequent heat treatment or machining.
Casting fettling mainly addresses the following issues:
It removes burned-on sand on castings. Dedicated professional machines are adopted for sand fettling, to eliminate residual molding sand and sand slag on the casting surface to the maximum extent.
It gets rid of excess metal such as surface burrs and flash. It removes surplus metal scraps at parting lines and corners generated during casting pouring, as well as redundant metal from gates and risers.
It eliminates surface oxide scale on castings. For this problem, physical grinding and impact methods like barrel tumbling are generally used, or manual trimming with grinding tools to remove the dark, hard oxide scale on the casting surface.
It facilitates quality inspection of castings. After fettling, the coverage of adhered sand and oxide scale on the casting body is removed, making it easier to detect hidden quality defects such as cracks, sand holes and blowholes.
Why is casting fettling indispensable in casting production?
In terms of appearance: Freshly poured and cooled castings come with various surface flaws and an overly rough finish. After fettling, the casting surface becomes clean and compliant with appearance standards, allowing it to pass visual inspection directly and be sold and put into use.
In terms of dimension: Raw castings often have excess metal edges and burrs, leading to poor form accuracy and uneven surfaces. This will compromise the dimensional accuracy and subsequent assembly of the castings.
Casting fettling has a direct impact on downstream processes. Castings usually undergo drilling, grinding, painting, assembly and other subsequent operations.
If raw castings with various defects are processed directly, they will damage processing equipment and impair the processing quality. Therefore, surface trimming via fettling is required in advance to ensure smooth follow-up production.
There are many conventional methods for casting fettling, which are mainly divided into the following four types in daily production.
- The first is manual fettling. Workers use tools such as angle grinders to remove excess metal and surface oxide scale, featuring high flexibility and convenience in casting treatment.
- The second is mechanical grinding fettling, which replaces manual work with special grinding equipment or grinders.
- The third is shot blasting or sand blasting fettling. High-speed steel shots or sand particles are sprayed to impact the casting surface, achieving the effect of sand removal and oxide scale elimination.
- The fourth is special shakeout fettling, a preliminary sand removal process in the early stage. Vibrating barrels are used to shake off large blocks of molding sand on the outer surface and inner cavity, or remove them during tumbling.
Each of the above fettling methods has its own applicable scenarios, which can be flexibly selected according to the size, batch quantity and structural characteristics of castings.
Shata Machinery has long been deeply engaged in the casting industry, integrating professional casting fettling technology into the casting production process.
With mature casting fettling expertise, Shata Machinery optimizes the appearance and dimensional accuracy of castings, while laying a solid foundation for quality inspection, mechanical processing, surface coating and other subsequent procedures.
