Formkernes

Formkernes is a term used in Danish metal casting to denote the internal cores placed inside a mold to create hollow or complex internal geometries in cast parts. The word derives from form, meaning mold, and kerne, meaning core. In practice, formkernes are equivalent to “cores” in English casting terminology.

Function and use: Formkernes are typically made from bonded sand, ceramic, or composite materials that can withstand the temperatures of molten metal and resist deformation during handling. They are produced in a core box or pattern that shapes the core and are placed in the mold either in the cope or drag before the mold halves are closed. During pouring, the molten metal fills the mold around the formkerne, forming cavities such as channels and hollow sections. After solidification and cooling, the core is removed or broken away, leaving the desired internal geometry. Core design and placement are critical to tolerances, surface finish, and dimensional accuracy, and require attention to core prints, venting, and runner systems.

Materials and methods: In traditional green-sand casting, formkernes are often made of silica sand bound with clay or resin; in high-temperature applications, ceramic cores or resin-bonded sands are used to prevent erosion. Production methods range from manual setting for simple cores to automated core making for complex shapes.

Applications and challenges: Formkernes support components in automotive, aerospace, and general engineering, including engine blocks, valve bodies, and pump housings. Challenges include core collapse, sand burnout, binder washout, and core shift during pouring, all of which can affect dimensional accuracy and surface finish.