Family-owned Kumera, which has three core businesses - process equipment for base metals, metal foundry and mechanical power transmissions - did not disclose any financial details of the transaction.
"The product lines of Kumera and Keller complete each other perfectly," officials said.
"The companies shall combine their skills and know-how in R&D, as well as improve production efficiency and utilisation of their increased volumes in economical purchasing and subcontracting."
Kumera employs 650 people at its manufacturing locations in Finland, Austria, Norway, China and now in Germany, promoting its lines via its own sales organisation and global agent network. The system, it said, is complementary to Keller's marketing network.