Binnenvlak

Binnenvlak is a Dutch term that translates to interior plane or interior surface. It denotes the inner face or boundary of a solid or hollow object—the surfaces that enclose the interior volume. This is distinct from buitenvlak, the exterior surface or outer boundary. The term is used in geometry, engineering, CAD, architecture, and manufacturing to refer to the faces that form the inner boundary rather than the outside.

In geometry, binnenvlakken occur on objects with cavities or walls; for a hollow polyhedron, the inner faces that define the cavity are binnenvlakken. The total interior surface area, binnenvlakoppervlak, is relevant for calculating coatings, insulation, fluid contact, and other functional properties of the interior. Orientation and treatment of the binnenvlak can differ from exterior surfaces because conditions such as exposure, cleanliness, and thermal or chemical environment may vary.

In practical applications, binnenvlakken are often specified separately from outer surfaces in design drawings and manufacturing processes. Finish, coating, material compatibility, and tolerances may differ for interior surfaces to meet specific performance criteria, such as ease of cleaning, corrosion resistance, or hydrodynamic properties.

Examples include the inner walls of a bottle, the interior faces of a duct or pipe, and the inner planes of a hollow shell or prosthetic component.

See also: buitenvlak, oppervlak, binnenoppervlak, binnenvolume.