Moulding is a process that is used in the manufacturing industry where a raw material like rubber, plastic, glass or metal is given a different shape through the use of a mould. The mould is a container that will hold the raw material in a liquid state and then allow it to become solid. Moulds are often made of steel to avoid quick wear and tear. If you are unfamiliar with the rubber moulding industry, this article brought to you experts at Camberley Rubber should help your basic understanding.
What Is Rubber Moulding?
Rubber moulding is the process where a rubber product is made from untreated rubber or elastomers. An elastomer is a natural polymer which has elastic properties which mean that they will return to their original shape after applying pressure. They are widely used in a number of industries because they are malleable. However, they also have many uses in industrial and domestic sectors.
Rubber Material Selection
There are different kinds of rubber compounds and each is different to the others. A selection process helps people choose the correct compound to use. There are a number of things that need to be kept in mind which will help achieve the best performance levels.
The main function of the part and whether it will absorb or transmit fluid or energy must be remembered. The material costs per part need to be looked at along with the location of the part. The temperature requirements and the exposure to chemicals should also be considered. The physical property and regulatory requirements will have to be looked at.
The Rubber Moulding Process
This is the process where heated rubber materials or compounds are injected into the mould under high pressure. The material will be in a molten state and kept inside the injection barrel. This is the most efficient way of creating any moulded rubber products.
The injection process starts with the uncured material being fed into the injection barrel as a continuous strip. The material is then warmed by an auger screw within the barrel. The auger screw will then pull back once the material has accumulated in front of it.
Once the auger screw has moved, the rubber material will be injected into the cavities of the mould by the injection press. The auger screw will then push forward when the mould is closed under high pressure to force the material into the mould cavities. The auger screw will turn again to refill the barrel when the material in the heated mould has cured. The part will then be removed from the mould once it opens and the press is ready to start the process again.
Advantages Of Injection Moulding
The primary advantage of this moulding is that it provides fast production. There is also minimal waste material and the design is flexible. The cost of labour with this is low and there is a flexibility in the material and colour used.
Disadvantages Of Injection Moulding
The primary disadvantage is that the tools are expensive. It is difficult to create accurate costing and there is a restriction in the parts design.
This is the simplest form of the moulding process and will have rubber or compound materials placed into a mould cavity directly. It will then take the shape of the mould once it is closed. The compression mould will differ in shape and size.
The compression mould process starts with the uncured material being placed into the mould which is then closed under hydraulic pressure. The part will be removed once the mould opens. The excess rubber is trimmed from the part. This moulding is done for any compound with medium hardness.
Advantages Of Compression Moulding
The primary advantage is that the tools are inexpensive for this moulding. It is also ideal for small productions and for big parts. The materials do not have to pass through sprues, runners or gates.
Disadvantages Of Compression Moulding
While the process is simple, the labour costs are high. There is also a high wastage of materials and the process is slow. This moulding is not ideal for complex moulds and there is an increased rejection rate from contamination.