What is compression moulding?
Compression moulding involves using heat and force to mould a product in to a specific shape. Most basically, in the very first stage of the process, the mould is full of the material. The material may be inserted in the proper execution of a good sheet or pellets or it may be loaded from a plasticating extruder. After the raw material has been loaded in to the mould, it is heated to its melting point so that it becomes malleable. It is then left to cool in the mould shape. A premier force or plug is used to force the mould and material into contact. The technique is suitable for complex and high-strength fibreglass and thermoplastics. The products most typically manufactured by the compression moulding method are polyester fibreglass resin systems, vespel, poly(p-phenylene sulphide) (PPS) and polyether ether ketone (PEEK).
This moulding method was introduced to create parts for metal replacement purposes. It is still typically used to manufacture large flat or slightly curved parts Compression Moulding. Hence, the process is suited to making car fenders, hoods, scoops and more intricate parts. Yet, its other uses range from household appliances to buckles and buttons.
The features of compression moulding
• Ease of manufacture
Before the resin material undergoes the process of moulding, it is in a soft and solid state. Hence, the manufacturer can easily decide which quantity of the material is needed, endowing the process easily and accuracy.
• Little waste
Once the quantity of material required has been calculated, it is heated and poured in to the mould until there isn’t any more space available. Thus, there is minimum waste. This efficiency is particularly important when expensive compounds are involved. Additionally, unlike other moulding systems, such as injection moulding, there are no gates, sprues and runners (passages) through that your material can pass before entering the mould – less material is lost and wasted.
• Low cost
Compression moulding is one of the simplest and consequently, most inexpensive moulding processes. The labour is cheap and as there is less waste involved, there are fewer costs for materials.
This moulding method has the capacity to mould large and fairly intricate parts. This technique also outweighs the aptitude of extrusion techniques in that it is suitable for ultra-large basic shape production.
Unlike other moulding methods, compression moulding produces fewer knit lines and causes a low quantity of fiber-length degradation. Therefore, compression moulding produces more accurate and quality results than other techniques.