extreme case lead to possible seizing of a valve flap part 17 that moves in relation to the premolded part 41 in lieu of the above described thermal intermediate treatment in the broadest sense light and thermal energy can be coupled into the premolded part 41 for example an intermediate treatment can be carried out by coupling black infrared radiation into the premolded housing part 10 in addition it is also quite possible to couple oscillations u2014 be they electromagnetic or mechanical u2014 into the premolded housing part 10 it is also possible to radiate oscillatory energy into the premolded part 41 in order to reduce stresses inside the second injection molding station 40 the intermediate treatment executed before the second injection molding step i e before the second injection molding station 40 brings the premolded part 41 into a state with a minimum of internal stresses and a high degree of dimensional reproducibility before insertion into the second cavity 42 of the second injection molding station 40 the intermediate treatment following the first injection molding step simultaneously serves as a buffer step for regulating the state with regard to the component temperature of the premolded part 41 the premolded part 41 subjected to an intermediate treatment has a temperature at approximately the same temperature level as at the end of the first injection molding step inside the first injection molding station this makes it possible to largely avoid possible production interruptions that lead to irregularities in the production process and therefore to.