  Semantically rich descriptions of manufacturing machines, offered in a
machine-interpretable code, can provide interesting benefits in Industry 4.0
scenarios. However, the lack of that type of descriptions is evident. In this
paper we present the development effort made to build an ontology, called
ExtruOnt, for describing a type of manufacturing machine, more precisely, a
type that performs an extrusion process (extruder). Although the scope of the
ontology is restricted to a concrete domain, it could be used as a model for
the development of other ontologies for describing manufacturing machines in
Industry 4.0 scenarios. The terms of the ExtruOnt ontology provide different
types of information related with an extruder, which are reflected in distinct
modules that constitute the ontology. Thus, it contains classes and properties
for expressing descriptions about components of an extruder, spatial
connections, features, and 3D representations of those components, and finally
the sensors used to capture indicators about the performance of this type of
machine. The ontology development process has been carried out in close
collaboration with domain experts.
