Causes and Solutions of Bubbles Appearing on the Surface of Aluminium Extruded Profiles

What is aluminum profiles?

Aluminum profiles are products born from aluminum alloys that are transformed into shaped objects through the extrusion process. Aluminum's unique combination of physical characteristics mostly depends on this process. Aluminum extrusions are used in several fields because this metal is: Strong and stable.

When the aluminum profile is squeezed and compressed, the air will stay in the aluminum profile, causing bubbles to appear inside and on the surface of the aluminum profile, causing defects that cannot be completely resolved, and making the aluminum profile a waste. In order to prevent air from entering the aluminum profile, it is necessary to find out why it was introduced.

The main causes of air entrapment in the four extruded aluminum profiles are as follows:

Thermal shearing of long rods results in entrapped air

When a pole is thermally sheared, the resulting shear plane is never perfect and vertical.

Simple thermal shearing of long rods of industrial aluminum profiles can bend the rods very severely, resulting in an oval cross-section of the aluminum profile with a very large fillet at the end of the shear. Even with the newest long rod shears, the edge corners of the shear rods are always rounded, and these rounds are the best places for air to hold.

Solution: Carry out standard inspection on aluminum rods, and resolutely put an end to unqualified aluminum rods.

The upsetting of aluminium extruded profiles leads to the residue of air

Air turmoil can lead to trapped air. Only when the diameter of the aluminum ingot cylinder is larger than the diameter of the column rod, the column rod can be put into the cylinder containing the aluminum ingot.

After applying pressure to the column rod inside the aluminum ingot cylinder to cause the column rod to expand to the diameter of the ingot cylinder, the gas carried must be discharged. The gas is not exhausted, and it remains in the aluminum ingot and eventually turns into air bubbles.

Solution: Configure the extrusion gasket according to the minimum size of the extrusion cylinder lining, replace the extrusion cylinder regularly, check the corrosion of the extrusion cylinder and extrusion pad, measure the inner diameter of the extrusion cylinder and extrusion pad and configure a suitable extrusion gasket, every shift Clean once and corrode the extrusion cylinder regularly.

The connection of two aluminum rods leads to the residual air

Due to the contact of the two aluminium rods, air will remain. Because the surface layers of the two stub rods are basically flat, the probability of entraining air is very small. The quality of the sawing directly interferes with the amount of air carried between the two stubs. At present, there is a high-tech that can prevent the two short column rods from being connected to eliminate the possibility of air entering.

Solution: Determine the aluminium rod with a reasonable rod length according to the process parameters, such as the single weight of the aluminium extruded profiles and the number of discharge counts.

Extruded aluminum profiles cause air entrapment

When extruding aluminum profiles, it is necessary to avoid air ingress and residual air, which will cause various defects in post-processing.

1. Improper oiling can cause air bubbles in the product.

Solution: adopt the correct refueling method to reduce the amount of refueling; strengthen the training of employees on operating techniques before taking up their jobs;

2. The excess pressure is too thin, causing the cracked metal to be pulled out during the shearing process, leaving a gap in the cracked hole of the mold.

Solution: According to the tonnage of the extruder, keep a reasonable excess thickness, and determine a reasonable aluminum rod length according to the process parameters such as the single weight of the profile and the number of discharges;

3. The extrusion die is designed with a flat die welding chamber, and the diversion hole of the diversion die is too large to cause air bubbles to flow into the cavity.

Solution: Reduce the size of the welding chamber of the flat die, reduce the die hole of the splitter die, and keep the distance from one side of the extrusion cylinder to more than 5MM.

Design molding causes bubbles in aluminum profiles

For example, in the mold design of the motor casing, during the production process of the aluminum profile of the motor casing, there are often phenomena such as air bubbles in the product due to the mold. At the same time, the service life of the mold is not long, and the phenomenon of premature failure of the mold also occurs. After the mold fails, the interchangeability of the motor housing is poor.

This article introduces the design and production drawings of a typical motor housing aluminum profile mold, which effectively solves the problems that often occur in the profile production process and can be used as a reference for similar products.


When the aluminum profile extruder is pressurized, air remains, causing bubbles to appear inside and on the surface of the aluminum profile, resulting in defects that cannot be completely resolved, making the aluminum profile a waste. Through the analysis and comparison of traditional and improved aluminum rod casting, extrusion and mold design and manufacturing process, it can be known that the output efficiency of extruded profiles can be improved, the control of extrusion surface requirements can be improved, and extruded aluminum profiles can be used in production. The solution of medium bubbles is critical.

Price of aluminum profiles

Usually the price will be affected by raw materials, market environment, research and development costs, etc. If you need to know the latest price of aluminum alloy, you can contact Staral’s customer service to answer your questions.

About Staral

Staral specializes in the deep processing business of aluminum products. Its main equipment include melting and holding furnaces from Switzerland GAUTSCHI, electro-magnetic stirring machines, refinery equipment and casting machines etc., 1+1+4 continuous hot rolling mill, 1+5 continuous hot rolling mill/three-stand and single-stand cold rolling mills with patent CVC flatness control imported from Germany SMS Group. Staral also placed large investments for high performance assisting equipment.

Staral’s main products are series 1, 2, 3, 4, 5, 6, 7, 8, etc. The main products are ultra wide aluminum alloy plate, aluminum alloy medium plate, aluminum alloy heckered plate, aluminum alloy brazing plate, aluminum coil, aluminum tube, aluminum profile, aluminum circle, aluminum forges, etc.

Staral has a large number of 5083/5052 aluminum alloy plates in stock, welcome to consult us and order.