Abstract: A plasticizing and injection group of mechanisms is detatchably secured on the injection side tool holder through a press-on and shift assembly. Releasable attachment occurs by automatically engageable and disengageable couplings each having a head, arranged at the end of an axially movable connecting element, e.g. of a piston rod of a press-on and shifting device. Slides engage the piston rod from behind a protuberance thereof slide back and forth crosswise to the connecting element. The slides are controlled by a central control unit of the machine. To perform maintenance work, the coupling is disengaged, and for better accessibility of the injection nozzle, the plasticizing and injecting group is moved away from the tool holder and can be pivoted out of the injection axis. Any manual work for releasing the attachment of the connecting element on the tool holder is eliminated.