G.Siempelkamp GmbH & Co. KG is the holding company of a group of affiliated companies consisting of the business units machine and plant engineering, foundry technology and service.

Siempelkamp's machine and plant engineering business unit is a system supplier of press lines and complete plants for the wood-based products industry, the metal forming industry and the rubber industry. Siempelkamp's foundry technology business unit has the world's largest hand-molding foundry capable of producing castings made of ductile cast iron with weights of up to 320 t (353 US tons). Siempelkamp NIS Ingenieurgesellschaft mbH is a component supplier as well as service provider for safety equipment around the reactor core.