A base assembly configured to cooperate with an injection blow molding machine for forming a polymeric container from a preform by injection blow molding. The base assembly includes a base insert defining a base mold configured to form a base of the polymeric container during injection blow molding. The base insert is slidably seated within the base assembly. The base insert is slidably movable between a retracted position and an extended position during injection blow molding of the polymeric container.

A method for holding together, in its closed state, a blow mold of multipiece design of a blowing station for the blow molding of containers from preforms made of a thermoplastic material using a compressed air-operated mold clamp exerting a holding-together force. The mold clamp is pressurized with compressed air for the purpose of and for the duration of the generation of the holding-together force. The blowing station has a relief valve which can be controlled by control compressed air from a control compressed air line. The mold clamp is pressurized at least at times with control compressed air from the control compressed air line.

In at least some implementations, a blow molding process provides that portions of the parison are engaged by one or more clamping devices disposed on or adjacent to the blow mold parts, and that the blow mold is opened whereby the parison is torn apart between the clamping devices, into two or more pieces of the parison. In other implementations, the clamping devices may be moved relative to the blow mold to tear the parison, or the parison may be torn by a combined movement of the blow mold parts and clamping devices.