Gas-assisted injection is a variant of the conventional injection process, and should not be confused with blow injection since the process is practically the same.

The process consists of several stages:

Through this process we can obtain thick or thin designs without marks or sinkholes. In some very specific cases, the gas and the molten polymer can also be injected simultaneously.

short piece

The cavity is partially filled with the polymer, then the gas is injected, which pushes the material until the cavity is completely filled, in this way the piece remains hollow in the areas where the gas is introduced.

Complete piece

The mold cavity is completely filled with polymer, and the gas is subsequently injected. When the gas is injected, the excess material passes into an auxiliary cavity that houses it, thus leaving a hollow piece.

Recoil by machine nozzle

The polymer is injected into one end of the mold, and after this the gas is injected from the opposite side. In this case, the excess material returns through the injection nozzle due to the pressure that the gas exerts on it.

The materials that can be molded using this process are the same as those that can be used for conventional injection; they may even include different types of fillers or reinforcements, such as fiberglass.

Some of them are:

The main characteristic of this process is that it allows the creation of hollow pieces, which leads to material savings. Furthermore, thanks to the pressure that the gas exerts uniformly on the piece, an extra compaction pressure is achieved. The pieces that can be manufactured through this process can be distinguished into three large groups.

The advantage of gas-assisted injection molding is that it does not require too much investment if you already have a conventional injection molding machine, since it will be enough to install an additional module that will allow us to carry out this process.

Therefore, to carry out gas-assisted injection molding we must have:

Of course, the processing parameters must be selected according to the shape of the mold and the characteristics of the selected polymer. Likewise, it is evident that semi-crystalline polymers have, due to their lower viscosity in the melt state, better flow characteristics and ease of forming with respect to amorphous polymers.