The purpose of a blow moulding machine is to assist in the task of blow moulding or BRE moulding. It is a manufacturing process for making and joining hollow plastic components. The use of the blow moulding process is also seen in the formation of glass bottles and other hollow components.
HISTORY OF BLOW MOULDING
The process of blow moulding originated from the idea of glass blowing. It started on a commercial scale in the year of 1938. The variety of products that could be produced with blow moulding was highly limited during the 1940s. The process did not gain popularity until the later years of the decade. As the popularity was not immense, the rates that blow moulding yielded were also less. Once the production rates boosted, the rates started increasing as well.
As glass is a fragile and easily breakable component, it was replaced by plastic in the later years. Plastic bottles were the first mass-produced in America in the year 1939. Germany adopted this technology a lot later. In the US itself, the number of plastic containers shot up a great deal. They went up from 0 in 1977 to more than 10 billion in the year 1999. It expected that this industry will grow more In the coming years.
In the recent years, more and more efforts are being made to extend the use of blow moulding to BMGs or bulk metallic glasses as well.
PROCESS OF BLOW MOULDING
The process starts with melting the plastic and then moulding it into a pare (also called parison) in case of extrusion blow moulding. In case of injection stretch and injection moulding, a preform is formed in place of a parison. The pare is basically a tubular component with a single hole at one end which provides a passage for air. This parison can be easily clamped into the mold. Air is then allowed to pass through it. The pressure of air is such that it pushes out the plastic in the mold. The mold cracks open as the plastic cools down and gets hardened. This part is now ejected from the mold.
TYPES OF BLOW MOULDING
There are three types of moulding, namely:
- Injection stretch moulding: There are types of injection stretch moulding namely, single-stage process and double-stage process. The outline of both these processes involves moulding the plastic into a preform and then using the traditional injection moulding process.
- Injection blow moulding: In this, the polymer is molded with an injection onto a pin which is then rotated to a BRE moulding station where it is allowed to be inflated and chilled.
- Extrusion blow moulding: In this, the plastic is melted at high temperatures and then poured into a parison which is then allowed to cool down in the metal mold. Air is circulated through the parison which inflates them to take up the shape of a hollow vessel. After the plastic sufficiently cools down, the mold cracks open and the part is separated.
Among these, the injection blow moulding process is the least preferred one. The other two are extensively and widely used by different manufacturers throughout different industries.