What is compression moulding?
Compression moulding involves using heat and force to mould a material into a specific shape. Most basically, in the first stage of the process, the mould is filled with the material. The material may be inserted in the form of a solid sheet or pellets or it may be loaded from a plasticating extruder. Once the raw material has been loaded into the mould, it is heated to its melting point so it becomes malleable. It is then left to cool in the mould shape. A top force or plug is used to force the mould and material into contact. The method 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). evertrue moulding
This moulding method was first introduced to make parts for metal replacement purposes. It is still typically used to manufacture large flat or slightly curved parts. 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 advantages 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 determine which amount of the material is required, endowing the procedure with ease and accuracy.
• Little waste
Once the amount of material required has been calculated, it is heated and poured into the mould until there isn’t any more space available. Thus, there is little or no 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 which the material can pass before entering the mould – less material is lost and wasted.
• Low cost
Compression moulding is one of the simplest and consequently, least expensive 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 process also outweighs the aptitude of extrusion techniques in that it is suitable for ultra-large basic shape production.