shellstøpning

Shell casting (dansk: shellstøpning) is a metal casting technique that produces close‑to-net‑shape parts with high dimensional accuracy and excellent surface quality. The process employs a disposable mold made from a thin ceramic or polymer‑based shell that rapidly sets around a pattern or a master vacuum symmetry.

The basic sequence begins with the creation of a central pattern, often considered a "core" or "master mould". A fine mist of resin and silica or a similar filler is sprayed onto the pattern and rapidly cured, forming a very thin, solid shell. Once the shell is sufficiently hard, the pattern is removed, leaving a cavity that is filled with molten metal. After solidification, the shell fragment and the pattern are broken away, leaving the cast part. Variants of the method use fusing materials or foamy plastics cast around a metal “master” in industrial sand moulds.

Shell casting is popular in small and medium production runs because it requires no expensive tooling or complex machinery. The products typically exhibit good dimensional stability, reduced burn‑through and improved surface finish compared to conventional sand casting. Typical applications include automotive components, aerospace fittings, tooling accessories and architectural castings.

Limitations include the relatively high waste of material—each part requires a draft pattern and a discarded shell—as well as the upper size limit governed by the thickness of the shell material. Additionally, the process is best suited to ferrous and non‑ferrous alloys that can withstand the rapid cooling imposed by the thin shell walls. Despite these drawbacks, shellstøpning remains a valuable casting method for rapid prototyping and low‑to‑medium volume production.