Types of Moulding

Injection Moulding

Injection molding is the most commonly used manufacturing process for the fabrication of plastic parts. A wide variety of products are manufactured using injection molding, which vary greatly in their size, complexity, and application. The injection molding process requires the use of an injection molding machine, raw plastic material, and a mold. The plastic is melted in the injection molding machine and then injected into the mold, where it cools and solidifies into the final part.

Advantages

• Fast production.
• Low labour costs.
• Design flexibility.
• High-output production.
• Multiple materials can be used at the same time.
• Can be used to produce very small parts.
• Leaves little post-production scrap.
• Ability to include inserts.
• Good colour control.
• Good product consistency.
• Reduced requirements for finishing.
• Good dimensional control

Disadvantages

• High initial tooling and machinery cost.
• Part design restrictions.
• Small runs of parts can be costly

Compressor Moulding

Compression Molding is a method of molding in which the moulding material, generally preheated, is first placed in an open, heated mouldcavity. The mold is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, while heat and pressure are maintained until the molding material has cured. The process employs thermosetting resins in a partially cured stage, either in the form of granules, putty-like masses, or preforms.

Types of Compressor Moulding

1. Flash Type
2. Positive Type
3. Landed Positive
4. Semi Positive Type

Advantages

• Lower cost Tooling
• Good for small production runs
• No gates, sprues or runners
• Good for large parts

Disadvantages

• Greater waste
• Higher labour cost
• Slower process times
• Not suitable for complex moulds
• Contamination
• Difficult to control flash
• Moulds can be damaged

Transfer Moulding

Transfer molding is a process where the amount of material is measured and inserted before the molding process takes place. The material is then preheated and loaded into a pot and a plunger is then used to force the material from the pot through the runner system into the mold cavities. The mold remains closed as the material is inserted and is opened to release the part from the runner. The mold walls are heated to a temperature above the melting point of the mold material; this allows a faster flow of material through the cavities.

Advantages

• High Cavity Count
• Short Production Cycle
• Design Flexibility

Disadvantages

• Complex Moulds
• Waste Material
• Mould Material

Blow Moulding

Blow molding is the process of forming a molten tube (referred to as the parison or preform) of thermoplastic material (polymer or resin) and placing the parison or preform within a mold cavity and inflating the tube with compressed air, to take the shape of the cavity and cool the part before removing from the mold.

Advantages

The blow molding industrial vertical has evolved so that it is almost universally used with plastic. Plastic blow molding is advantageous due to the significant increase in production capabilities.

This allows companies to produce far greater quantities in a shorter period of time. Molding machines allow for three-dimensional moldings, significantly reduced flash, and a much faster production cycle.

Disadvantages

The biggest disadvantage may be the negative environmental effect associated with plastic use. Plastic isn’t biodegradable and it typically makes its way in massive quantities into landfills. There is also the concern caused by such a wide use of petroleum. This is a valuable resource that is being reduced by its use in plastic production. However, recycling is available to allow for plastic to be reused.

Rotational Moulding

Rotational Molding, also called rotomolding or rotocast, is a thermoplastic process for producing hollow parts by placing powder or liquid resin into a hollow mold and then rotating that tool bi-axially in an oven until the resin melts and coats the inside of the mold cavity.

Advantages

• Large Size of Products
• Surface Quality
• Inserts
• Decorations in Mould

Disadvantages

• Varying Thicknes
• Time Taking

Thermo Forming

Thermoforming is a manufacturing process where a plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mold, and trimmed to create a usable product.

Advantages

• Extremely adaptive to customer design needs
• Rapid prototyping development
• Material and process is optimized for cost effectiveness
• High-speed production allows for just-in-time shipments
• Flexible tooling design offers a competitive advantage
• On-the-fly product enhancements with low additional costs
• Visually pleasing appearance
• Weight savings for consumer and manufacturer
• Wider design scope
• Lower tooling costs
• No anticorrosion spray necessary
• Paintable and colored plastic availability
• Fully integrated process with limitless flexibility for small to large product designs 

Disadvantages

• During this process, the plastic sheets that are in a pliable state can break due to excessive stretching under certain temperatures. This in turn leads to wastage and about 20% more use of plastic that results in higher process costs.
• Due to the use of higher-quality plastic sheets, this method is costly (about 50 % more) as compared to other methods.
• In this process, only one side of part is defined by the mold.
• Here, the parts that include sharp bends and corners are not easy to produce and internal stresses are common.