Injection moulding is a common manufacturing method, used to produce large volumes of plastic parts. The process involves injecting molten plastic into a mould under high pressure until it cools and hardens into a desired shape. Plastic moulding is ideal for producing precise, high quality plastic parts due to its accuracy. It’s used across a variety of industries including automotive, consumer goods, electronics and construction.
In this post, we’ll explain the process of injection moulding, common materials used and which industries rely on this manufacturing method.
How does it work?
The injection moulding process consists of 5 key steps. Here’s a more detailed breakdown of how it works.
1. Loading and melting: Plastic granules are placed into a hopper, then a heating chamber, where they are melted into a liquid using heat and friction.
2. Injection: Once the plastic has fully transformed into a liquid, it is fed through a nozzle into a closed mould cavity, where pressure is applied.
3. Cooling: The mould is cooled, and as the plastic inside hardens, it takes on the shape of the mould.
4. Ejection: Once fully cooled, the finished part is ejected.
5. Cycle repetition: The process is repeated to produce as many parts as necessary.
Plastic injection moulding allows for large scale production without compromising on precision and efficiency. It’s a versatile method that can be used to produce a range of different shapes and sizes for plastic components, making it useful for a variety of industries.
What is it used for?
Plastic injection moulding is used across many industries to produce large quantities of identical parts from a single mould. It is a versatile and efficient manufacturing method for mass production.
Here are a few examples of the key industries that commonly use plastic injection moulding.
Automotive: Injection moulding is used to produce lightweight and durable parts such as headlight surrounds, door handles, and dashboard panels. It is ideal for the automotive industry because it is highly precise and can produce the complex shapes needed for specific parts.
Medical: Precision and durability are essential in the medical industry. Injection moulding is ideal for creating products such as syringes, medical vials, and microplates. The process ensures that each product is consistent so that they are reliable in medical applications.
Consumer goods: Toys, containers, and household items are all a common end product of injection moulding. This is because it has the ability to produce large quantities with detailed designs. This is well suited for the consumer goods industry as it is affordable to mass produce with an efficient turnaround time (dependent on the manufacturer).
Fire and safety: Injection moulding is a common method to produce nozzle guards and handles in the fire safety industry. It can produce strong, durable components that withstand high-impact and harsh conditions.
Construction: The construction industry needs sturdy components for electronics, fasteners and connectors. Plastic moulding is ideal for producing large quantities of precise parts that can withstand environmental conditions.
Aquatics: Filters for fish tanks and water treatment systems can also be produced using injection moulding. The process ensures precision and sophistication for the complex component designs used in water filtration systems.
What are the advantages of injection moulding?
Injection moulding offers many benefits that make it the preferred manufacturing choice for many businesses.
Cost-effective: After a mould tool has been made, the process of injection moulding becomes a highly economical method for large scale production. As production volume increases, the cost per unit will decrease, making it ideal for mass production of identical components. This makes it a suitable choice for businesses that are aiming to scale up their production while controlling costs,
Design complexity: Plastic moulding can produce highly detailed and complex parts that would be difficult to achieve with other manufacturing processes. Features such as undercuts, threads and thin walls can be integrated into a single part, avoiding the need for multiple assembly steps or additional machining.
Consistency: Automated systems and high-precision equipment ensures tight control and high quality standards, ensuring each part is produced identically. This is essential for industries where uniformity is crucial, such as medical and automotive parts manufacturing.
Efficiency: Once tooling is complete and the process is fine-tuned, injection moulding can run consistently with minimal human intervention. It can produce thousands of parts per hour with very low waste and energy. The end result is fast turnaround times and a lower environmental impact compared to other manufacturing techniques.
What are the disadvantages of injection moulding?
While injection moulding is a popular and efficient manufacturing method, there are a few important considerations to bear in mind when deciding if it’s the right fit for your project.
Initial setup costs: There is a high upfront initial investment when producing a mould tool. They are often custom made and require precise engineering. However, consider that this is a one-time investment, and your mould tool can be modified in line with changes to your component.
Production quantity: Injection moulding is best suited to high volume-production. It’s important to consider the number of parts you require as projects with very low quantities may be better suited to other methods such as 3D printing or CNC machining.
What materials are used in plastic injection moulding?
Many different plastic materials can be used in injection moulding, each with their own set of unique properties and applications. Here are some of the most common ones:
Polypropylene (PP): A cost-effective, versatile material that has good chemical and heat resistance. It has a range of applications, from heat proof food containers, to car parts and medical equipment. It’s worth considering that polypropylene would not be suitable for a component that is exposed to the sun due to poor UV resistance, and can scratch easily.
Acrylonitrile Butadiene Styrene (ABS): A very rigid, impact resistant plastic with a smooth surface finish and strong chemical resistance. It is commonly used to create products like LEGO blocks, keys for a keyboard, and automotive parts. However, it also has poor UV resistance, isn’t biodegradable and can emit fumes when in a molten state.
Polycarbonate (PC): A strong, tough and transparent plastic, making it a great material to use for electronic and automotive parts. It generally has a higher price point due to its durability, however might not be the best choice for use with solvents and hot water.
High Impact Polystyrene (HIPS): Derived from standard polystyrene, is a material that is modified for high impact resistance. It’s typically used for a range of domestic and commercial applications such as packaging or appliance housings, but may become weak, flakey or brittle with prolonged outdoor use.
Low Density Polyethylene (LDPE) and High Density Polyethylene (HDPE): LDPE is chemically resistant and flexible, a popular material used in trays, containers, plugs and pipes. HDPE has more strength and rigidity, often used in bottles, hard containers and outdoor furniture. Both have a high resistance to moisture, but may weaken under UV light without treatment.
Nylon or Polyamide (PA): A common engineering plastic with excellent high temperature performance alongside resistance to wear and chemicals. Nylon is best applied to electrical components and automotive parts and shouldn’t be used in low temperatures as it may become brittle in the cold.
Polymethyl Methacrylate (PMMA): known for its clarity and resistance to UV, ideal for vehicle lights and safety glass and acrylic products. However it is prone to stress-cracking, meaning it wouldn’t be the best choice for high-impact applications.
Injection moulding at Bowles & Walker
Choosing the right injection moulder is crucial for your project’s success. Here at Bowles & Walker, we’re all about delivering high quality parts efficiently and consistently. We’re also on a mission to become as sustainable as possible and reduce our carbon footprint. We’ve already implemented a range of sustainable practices, including using recycled plastic materials and renewable energy sources, like wind and solar power.
If you’re looking for a reliable, environmentally friendly, UK-based injection moulder, look no further. Whether you have a new project or looking for a new manufacturer, reach out to us today by either filling out our contact form below or calling 01953885294. Let’s mould success together!
