Blow Moulding Process | Rotational Moulding Process

Blow moulding Process

The blow moulding procedure is intended for the production of large quantities of hollow items in a single piece. This is the procedure to use if you need to create a large number of bottles. Blow moulding is used to produce thin-walled containers that are highly homogeneous in thickness.

Working principle of Blow Moulding Process

In this process between the two parts of open moulds a hot extruded tube called parison is placed. The two valves of the moulds move close to each other so that the moulds closes over the tube.


The parison’s bottom end is sealed. The molten plastic is mould with the help of blowing compressed air and the tube gets pinched off and also gets welded at the bottom by closing the moulds. The air pressure is about 0.7 to 10kg/cm². This air pressure will force the tube against the walls of the mould. Then is component is cooled to room temperature, and the mould is opened to release the component. The bloe moulding method will vary from simple manual operation to complicated automatic ones. The different types of blow moulding process are

1. Injection blow moulding

2. Extrusion blow moulding

3. Multi blow moulding

In multilayer blow moulding, multi layer structure are generally used. Typical example for multilayer blow moulding are plastic packing for food and beverage.

Application of Blow Moulding Process

It is used in making plastic bottles and toys.The hollow containers are produced by this process only. The multilayer blow moulding is used in cosmetics and pharmaceutical industries.

Rotational moulding Process

With significant advancements in manufacturing technology over the last 20 years, rotational moulding (also known as rotomolding) is becoming increasingly popular among businesses. Rotational moulding (also known as rotomolding) is a multifunctional process that is being used by more and more businesses every day.

Plastic powder is added to a shell-like mould and then rotated and heated at the same time, resulting in hollow parts that are mostly used for hollow parts manufacturing. As a result of this process, the powder is fused together to produce a bubble-free liquid layer that conforms to the shape of the inner mould surface. After that, the mass is allowed to cool before the hollow section is removed.

This procedure is most often employed in the production of tanks, but it may also be utilised in the production of sophisticated medical devices, toys, recreational crafts, and a variety of other things.

Machining Equipment for Rotational Molding

Rotational moulding machines are comprised of many components, including an oven, a cooling chamber, and mould spindles. Molds are often manufactured of aluminium alloy, either by CNC machining or metal casting techniques. As a result, they are much thicker than an equal item made of stainless steel. It is also possible to create moulds from welded sheet steel, depending on the size and complexity of the object to be manufactured.

Working principle of Rotational moulding Process

Generally the thin walled hollow parts will be manufactured using rotational moulding process. In this method, a measured amount of polymer will be placed in a thin walled metal mould. Then the mould will be closed. And then it will be rotated about two mutually perpendicular axes as it is heated.


The rotation will make the powder to settle upon the mould walls. After heating and sintering, the mould is cooled while it is still rotating. The cooling of the mould is generally done by spraying air and water. After this the rotation is stopped and the moulded component is removed.

In this type of moulding a thin walled metal mould is made of two pieces and is rotated in perpendicular axis. A measured quantity of powdered plastic material is placed inside the mould. Then the mould is heated and rotated. Most of the thermo plastics and some types of thermosets can be formed into large hollow parts by rotational moulding.

Rotational moulding is also used for producing components with hollow shapes with a very less wall thickness of about 0.4mm. Larger parts in terms of 4m can also be produced using this process. The surface finish of the internal of the mould is the same as that of surface finish of the walls. In this process time and temperature plays a vital role.

Application of Rotational moulding Process

It is generally used in making large containers of polyethylene. Manufacturing of buckets, housings, boat hulls are made easy by this process. It is used to produce tanks of various sizes. It is also used for making football bladder. Tanks and containers made via rotational moulding have wall thicknesses ranging from 0.5 to 20 millimetres. Their total capacity might be as high as 13,000 gallons capacity.