valupinnan

Valupinnan is a Finnish-language term used in metal casting to refer to the surface of a casting that is formed by contact with the mold or pattern. In practice, it describes the outer or interface surface that becomes the visible part of the finished casting after solidification. The concept encompasses both the mold-side surface and the resulting casting surface, and it is central to assessing cosmetic appearance, dimensional accuracy, and the need for post-processing.

The quality of the valupinnan is influenced by multiple factors, including the mold material (such as sand, ceramic, or metal, and any coatings), mold temperature, metal pouring temperature, and cooling rate. The design of the mold and gating system, venting, and the use of chills or cooling aids also play crucial roles. Proper control aims to minimize surface defects such as roughness, porosity near the surface, cold shuts, and oxide films, while achieving the desired surface texture for subsequent finishing.

In practice, engineers specify target valupinnan characteristics early in the design and process planning. Achieving a good surface may involve selecting appropriate mold materials and coatings, optimizing pouring and cooling, and applying finishing steps such as machining, grinding, shot blasting, or chemical treatments as needed to meet final specifications.

Measurement and quality assessment of valupinnan typically use surface roughness parameters (for example Ra and Rz) obtained with profilometry, along with visual inspection and, where needed, optical or 3D surface scanning. The term is common in Finnish foundry literature and quality documentation, and it reflects the importance of the mold-casting interface in producing reliable, accurately finished parts.