"The members of Kraftwerk were originally electronic engineers, and built all of their early instruments themselves as a demonstration of their abilities."

This would seem to be a partial truth, in that the members of the band did build and modify a few instruments, but on the whole, would use standard production equipment, such as Moog MiniMoog and Polymoog, ARP Odyssey, EMS-Synthi A, Korg PS-3300 and Sequential Circuits Prophet VS.

They do hold several patents for electronic instruments however.


Source:
http://ourworld.compuserve.com/homepages/aktivitaet/10_kk1.htm