the process for manufacturing a magnetic circuit for a valve represents a particularly cost - effective version with minimized material use . for this purpose , a single - part valve housing has a groove , where a non - magnetic intermediate ring is placed . an axial pressing force is applied on the intermediate ring using a pressing tool , radially displacing the material of the intermediate ring and the valve housing . with a simple machining operation , valve house material is removed from an opening , so that the internal field and the valve jacket are spatially separated from the components obtained from the valve housing by the intermediate ring . the magnetic circuit thus manufactured is particularly well suited for fuel injection valves for fuel injection systems of internal combustion working with an externally ignited compressed mixture .