Abstract: An extrusion machine for continuously making articles, such as concrete slabs, by forcing the article-forming material through a mold, said machine being moved forwardly by reaction as the material is forced against the portion of the article already formed. The material is moved under pressure by one or more spiral conveyors through the mold, and a forming element of any predetermined cross-sectional shape is substantially aligned with the down-stream end of each spiral conveyor and is mounted so as not to rotate with the latter. It is preferable to provide a vibrator in each forming element.