Glass Bottle Forming Process

I. The Forming Process
The forming stage for glass bottles and jars refers to a specific sequence of combined actions-involving mechanical, electrical, and other systems-that are repeated according to a programmed order. The objective is to manufacture a bottle or jar possessing a specific, predetermined shape. Currently, there are two primary processes for the production of glass containers: the "blow-and-blow" method, used for bottles with narrow necks, and the "press-and-blow" method, used for bottles and jars with wider openings.
In the blow-and-blow process, molten glass is initially forced downward by compressed air introduced through a baffle, thereby shaping the glass within the neck ring. Subsequently, the plunger retracts slightly; compressed air then flows upward through the resulting gap around the plunger, expanding and pressing the glass to completely fill the parison mold. Through this initial blowing action, the glass forms a hollow, preliminary shape (known as a parison), which is then transferred to the final mold and blown a second time with compressed air to achieve its ultimate, finished form.
In the press-and-blow process, the parison is not formed using compressed air; instead, it is created by a long plunger that presses and displaces the glass within the confined space of the parison mold cavity. The subsequent transfer (inversion) and final blowing stages are identical to those in the blow-and-blow method. Once formed, the finished bottle is extracted from the final mold by a takeout tong and placed onto a deadplate-where it is cooled by an upward flow of air-to await transfer by a conveyor mechanism to the annealing stage.
II. Glass Bottle Forming Machines
A glass bottle forming machine is a piece of equipment specifically designed to manufacture glass bottles and jars. Typically, a forming machine executes a sequence of 19 fundamental operations to produce a single bottle. Currently, the majority of glass bottle forming machines and their associated mechanisms are actuated by compressed air; the entire system is electronically controlled via a timer network that coordinates every action in the sequence.
The most widely used type of equipment is the "Individual Section" (IS) machine. This machine consists of anywhere from 2 to 20 identical, independent sections, each containing a complete set of mechanisms capable of fulfilling all the requirements for bottle production. The molten glass gobs (parcels) for all sections are delivered to their respective stations via a moving chute, commonly referred to as a gob distributor. These forming machines are capable of simultaneously producing one, two, three, or four bottles per section (referred to as single-gob, double-gob, triple-gob, and quadruple-gob configurations, respectively). In recent years, even six-gob machines have been successfully developed and put into commercial production. In the case of multiple gob production, the shears simultaneously cut the glass gobs, which then drop into the blank molds at the exact same moment.
III. Annealing
As glass cools, it contracts and solidifies. Uneven or rapid cooling induces internal stress within the glass, rendering it brittle or prone to shattering. The function of the annealing lehr is to heat the glass bottles and jars to approximately 580°C, followed by a gradual cooling process designed to relieve the stresses generated during the forming stage, thereby ensuring the structural integrity and safety of the glass containers. The duration of this annealing phase depends on the thickness of the glass, typically ranging from 20 to 60 minutes.