1. Raw Materials

There are four main ingredients used to manufacture glass:

Silica sand, soda ash, limestone and recycled glass (cullet).

There are also a variety of minor ingredients, (some are included to give glass its colour). These raw materials are simple and readily available.

Whilst the process of glass manufacturing has been refined over the centuries, it still remains similar to that first used by the Egyptians around 3000 BC. Obviously the process used today is more sophisticated and highly technical.

The materials are stored in the Batch House in compartments, gravity fed into the weighing and mixing area, and finally elevated into batch hoppers, which supply the glass furnaces.

2. Furnace

The two furnaces are capable of producing 210 and 250 tonnes of glass per day.

Firing is by natural gas through the side ports and the glass temperature in the furnace ranges from about 1100 – 1590 degrees Celsius.

The batch and furnace control room where the batch and melting processes are controlled with computer systems.

The batch and furnace laboratory.

Molten glass flows out through two feeders to the forming machines attached to each furnace.

Economical melting [within the furnace] of raw materials into glass requires constant supervision and monitoring with the use of sophisticated computer-based control systems.

An open, empty decommissioned furnace after 12 years of service

The furnace inside

3. Forming

From the furnace, the melted glass goes to the refiner and then the forehearth where the glass is “conditioned” before entering a bottle forming machine. These are either double or triple gob machines.

Gob is the measure of molten glass delivered to the machines.

The number of gobs vary depending on how many sections are in the forming machines. The sections within the forming machine contain bottle or jar moulds. Each mould comprises 11 separate pieces and a large forming machine can carry as many as 30 moulds.

The animation on the left shows a gob of molten glass being formed into a bottle within the mould. (Macromedia Flash Player required)

4. Annealing Lehr

Anneal is to toughen (glass or metals) by heating and slow cooling.

An annealing lehr is a long, flat oven, which first reheats the bottles to 550 degrees Celsius and then gradually cools them until they emerge at the cold end, between 30 minutes and one hour later.

Annealing is necessary because the glass is a poor conductor of heat and cools unevenly when it emerges from the forming machine.

The lehr ensures even cooling of the whole bottle, which reduces residual stresses inside the glass.

The bottles are given two surface treatments during their journey through the lehr. One at the “hot end” – which helps maintain their strength, and one at the “cold end” – which helps prevent scratching.

The surface treatments also aid bottles to move smoothly along the filling line at a customer’s plant.

5. Quality Inspection

After leaving the cold end of the lehr, bottles then pass through electronic inspection machines, which automatically detect faults.

These include, wall thickness inspection, squeeze testing, sealing surface inspection, side wall scanning and base scanning.

The information from the quality inspection machines is relayed back to the “hot end” forming machine operators who can then make adjustments to remove the problem.

Rejected bottles are returned to the raw materials area and recycled as cullet in the batch for making new glass.

Quality inspection is an essential part of the manufacturing process. It ensures the best product possible is always distributed to customers.

6. Distribution / Customer

Once the bottles have passed inspection, they are packed in pallets.

Each pallet can be 4-11 layers high and contain as many as 5000 bottles. Once the pallet has been assembled, a large plastic envelope is placed over it and shrunk until tight. This makes sure the pallet is stable, ready for transportation to the warehouse.

Quality bottles and jars are then distributed to customers around New Zealand to be filled with food and beverage products.

7. Recycling

Once the glass bottle or jar is empty, it can be recycled either through kerbside recycling or a public recycling facility.

Recycling is a positive step, which is supported and promoted through most local councils who provide a weekly kerbside collection recycling service.

O-I then buys the recycled glass (cullet) through its network of Principal Suppliers throughout New Zealand.

The glass recycling rate in New Zealand compares very favourably with other countries around the world.

8. Beneficiation

Beneficiation is the process of treating raw materials to improve their properties. This is carried out for O-I by a company called Visy Recycling New Zealand, who has a plant adjacent to O-I in Penrose.

Throughout New Zealand, there is a network of recycled glass collectors who pre-process the glass by colour sorting it and removing contaminants such as crockery, window glass, metals, etc.

Waste glass (cullet) then arrives at the Visy Recycling plant in Penrose to be further processed. Already separated by colour, the cullet is placed into a hopper and fed onto a belt. The belt carries the cullet through a powerful magnet to remove bottle tops and other metals. The belt then carries the cullet below a metal detector, which removes segments of glass contaminated with aluminium and other metals. This will be processed again until no metal is detected.

It then passes through picking stations to remove contaminants such as ceramic, pyrex and other rubbish that cannot be removed mechanically as shown in the picture below.

It is then crushed and fed via a weighing conveyor into the O-I Glass Packaging site ready to be made into new bottles and jars.