In a method of manufacturing discs, with an information structure on one side, from a synthetic material by an injection molding device, the injection molding device comprising:
- a mold having a first mold section (1) and a second mold section (2) which are movable relative to one another between an open and a closed position, a mold cavity (3) is defined between the mold sections in the closed position, and the synthetic material is injected into the cavity to form said discs,
- a flat mirror plate (12) located on the first mold section,
- a disc-shaped stamper (16) bounds a first side of the mold cavity and the disc-shaped stamper is detachably secured to the mirror plate (12),
- a guard ring (17), detachable from the first mold section, covering the periphery of the stamper (16) in an operating position,
- a quick-fastening device (18-20) cooperating with the guard ring (17) for rapidly securing the guard ring to the first mold section in the operating position,
- a coupling device (33, 37) coupling the guard ring (17) to the second mold section (2) in the closed position of the mold, and
- said stamper (16) being detachably secured to a stamper support (21), the stamper support cooperates with a stamper changer (26-32) provided on the first mold half (1) for changing the stamper when the mold is in the open position and the guard ring (17) is coupled to the second mold section (2),
- the method comprising a number of production runs comprising a plurality of production cycles, each production cycle, comprising the following steps:
- closing the mold, injecting and cooling the synthetic material, opening the mold, and removing the disc, the stamper being changed after every production run, after the stamper is changed a starting run is performed, said starting run comprising a plurality of starting cycles comprising the same steps as the production cycles but yielding a reject product, after the starting run, a next production run commences, the improvement comprising
- the automatically controlling of a sequence of successive production runs, stamper changes and starting runs,
- each stamper change is carried out within a fixed time interval and comprises the following steps:
- coupling the guard ring (17) to the second mold section (2) towards the end of the last production cycle of a production run by actuating the quick-fastening device (18-20) and the coupling device (33, 37), opening the mold releasing the stamper support (21) from the first mold section (1) by actuating the quick-fastening device after removal of the last disc of the production run from the open mold, removing the stamper support with the stamper from the first mold section by a stamper manipulator, positioning a next stamper support with a next stamper on the first mold section by the stamper manipulator, securing said next stamper support to the first mold section by actuating the quick-fastening device, and securing the guard ring to the first mold section by actuating the coupling device and quick-fastening device prior to the beginning of the starting cycle of the next starting run.