The company was formed by a merger between Yhtyneet Paperitehtaat ('United Paper Mills') and Rauma-Repola.
Yhtyneet Paperitehtaat was the forestry and papermaking subsidiary, Rauma Oy the engineering.
From 1987, Sunds Defibrator had acquired the equipment companies Jylhävaara and Rauma Repola Pulping Engineering, whilst in exchange becoming owned by the overall groups UPM and Rauma-Repola.
In 1991, SCA sold the final third of Sunds Defibrator, it becoming wholly owned by Repola Oy.
From 1995, Repola and its subsidiary Yhtyneet Paperitehtaat ('UPM'), merged with Kymmene Oy [fi] to form UPM-Kymmene.