How Aluminium Bottles Are Made: From Slug to Sleek Containers

Aluminum bottles are becoming increasingly popular in a variety of industries due to the lightweight, durable, and recyclable nature of the material. But have you ever wondered how these versatile containers are actually made? Trust us when we say, it’s a fascinating process! The process begins with a simple piece of aluminum called a slug. Here, we’ll take a step-by-step journey from slug to finished aluminum bottle.

EBI’s Screw bottle production suppliers have two forms, one is automatic line and the other is semi-automatic line. As the name suggests, the automatic line means that all processes are completed by machines, while the semi-automatic line will be manually operated. For example, in the spray painting part, the direction of the bottle will be changed manually to ensure uniform spraying.

Production steps

Step 1: Billet casting
A metal block is a piece of aluminum stamped or pressed from a roll of aluminum plate or coil. It is essentially a blank that will be transformed into a bottle. These aluminum blocks are added with talc powder for billet casting.
Step 2: Extrusion
The slugs are lubricated and the slug is placed under a press. The press forces the slug through a die, a process known as cold extrusion. This creates a long, cylindrical shaped container.
Step 3: Trimming
The top of the bottle is usually a bit irregular. To fix this problem, bottles go through an edge trimming process where excess material is cut away, leaving a clean, even edge. At the same time, the bottle will be polished to make the entire bottle smoother to facilitate subsequent printing and painting processes.
Step 4: Cleaning and Washing
After trimming, wash the bottle to remove any oil or residue. Wash them first with detergent and hot water, then again with cold water. It is then placed in a drying oven for drying.
Step 5: Inner coating
Apply an interior paint (epoxy phenolic primer or polyester paint) to the inside of the aluminum bottle and pass the bottle through the drying oven a second time. The function of the inner coating is to prevent the bottle from reacting with the contents, and also to ensure that the bottle will not be corroded. Secondary drying allows the inner coating to better adhere to the inside of the bottle and prevent it from falling off during subsequent cleaning.
Step 6: Coating and Decorating
Before decorating, apply a coat of primer to the aluminum bottle to ensure subsequent layers of ink and graphics will adhere properly. The bottles are then decorated using indirect printing techniques, and depending on the desired design and surface treatment. Additional screen printing can be performed in a separate process.

Step 7: Overlacquering

To protect the printing, aluminum bottles are coated with a clear lacquer (glossy or matte). After painting, you must apply matte oil, otherwise the bottle will collide during transportation and the paint will fall off, which will greatly affect the appearance.
Step 8: Necking
To create the neck (the narrower opening at the top), the bottle goes through a process called “necking.” This involves a series of tools that gradually reduce the diameter of the bottle opening to the desired size.
The bottom of the bottle creates a concave base, giving it stability when standing. This is done using a special tool that shapes the bottom of the bottle. The design of the bottle mouth is made according to the needs. If it is a threaded bottle , you need to perform the thread rolling step. If it is an aerosol can, you need to perform another sealing operation.
Step 9: Inspection and Packaging
The final step involves a thorough inspection of the bottles to ensure they meet all quality standards. Once they pass inspection, they are packaged and prepared for shipping to customers.

The difference between automatic line and semi-automatic line

This is the production process of the automatic line. The production process of the semi-automatic line will be slightly different. After stamping to form the preform, the next step is to shrink the shoulders. The shape of the bottle mouth and shoulder will be determined first. For threaded bottles, the threaded mouth will be made. Then there are the cleaning and other operations.

There are also differences in the printing process between automatic lines and semi-automatic lines. Semi-automatic lines can do heat transfer printing, water transfer printing, silk screen printing, electroplating and hot stamping, while automatic lines can only do offset printing. Because the semi-automatic line has manual help, it can adjust the direction of the bottle, etc., so it can do more complex printing technology.

Printing process

Heat Transfer Printing：

Print the desired pattern or image on heat transfer paper. Tightly combine the heat transfer paper with the aluminum bottle, and then use a heat press or heat transfer equipment to transfer the pattern onto the bottle.
After the pattern has cooled, gently peel off the heat transfer paper, leaving the transferred pattern.

Water Transfer Printing:

Print the desired pattern or image on the water transfer film.Put the water transfer film into the sink and let it soak in the water.
Activation and transfer: The activator will cause the pattern to detach from the water transfer film and float on the water, and then slowly immerse the aluminum bottle in the water to transfer the pattern to the surface of the bottle.

Screen Printing：

Preparing the design: Transfer the desired pattern to the silk screen, on which the pattern is templated.
Coating: Place the ink or ink on the screen and then use a scraper to smooth the ink so that it can be transferred to the aluminum bottle through the holes in the screen.
Cure and dry: The ink cures and dries on the body of the bottle, forming a long-lasting pattern.

Electroplating:

Aluminum bottles undergo chemical treatments such as pickling, degreasing and activation to remove impurities and improve surface roughness.
Electrolyte preparation: Select the appropriate electrolyte and place it in the plating tank.
Electroplating: The target object is placed in a plating bath as a cathode (negative electrode), and a metal anode (positive electrode) is also placed in the plating bath. When an electric current is applied, metal ions on the anode are deposited on the surface of the target object to form a metal coating.
After electroplating is completed, the aluminum bottle needs to be cleaned and post-processed to remove residual electrolyte and improve the quality of the coating.

Hot Stamping:

Preparing the design: Transfer the desired pattern or image to foil, usually using a foil plate or foil.
Heating: Use a hot stamping machine or heat press to heat.
Imprinting: Place the hot stamping foil tightly onto the aluminum bottle and then apply pressure to bond the foil layer to the surface of the aluminum bottle.
Cooling and peeling: After the hot stamping area has cooled, gently peel off the hot stamping foil, leaving the hot stamping pattern.