Other Plastics
What is Injection Moulding?
Injection moulding is a manufacturing process that allows producing parts in large volumes by injecting molten materials into a mould. It is typically used as a mass production process when it is necessary to produce thousands of identical items or to rapidly produce custom prototype parts.
This process basically consists in heating the material until it melts and injecting it under pressure into a closed metal mould tool. Once it cools it hardens into the shape inside the mould tool and can be ejected in the desired shape.
There is a wealth of different materials that can be used for injection moulding, such as metals, glasses, elastomers and confections, however, thermoplastic and thermosetting polymers are the most commonly used.
How does Plastic Injection Moulding work?
Plastic injection moulding is quite of a simple process, consisting in 5 basic steps:
The first step of injection moulding is mould manufacturing, this is, creating the tooling (mould) to be used. Usually they are made from metal, often steel or sometime aluminium, and precision machined to match the features of the product they are to produce.
Then it is time to pour the material into a heated barrel and mix it using helical shaped screws. Thanks to the heating bands the material melts. Here it is important to mention that separate materials can be combined, what is known as a two-shot mould. Normally this technique is used to add a soft touch to plastic products, add colours to a part or produce items with different performance characteristics.
The molten material is fed into the mould cavity where it will cool and harden matching its shape.
In case cooling time needs to be reduced, a good alternative is using cooling lines that circulate water or oil from an external temperature controller. This step is optional. This step is optional.
Finally, once the material has solidified, platens on which moulds are mounted open so that the part is ejected from the mould.
When is Injection Moulding used?
As shown previously, injection moulding is used to make a range of widely used products, from common plastic items like bottle tops to larger items such as car body panels. The common denominator is the need to manufacture extremely huge volumes of identical parts from the same mould, as it enables to scale up production to produce a large number of parts.
According to the type of part to be produced, the type of injection moulding we offer would be one of another. Find below a list with the main process variations:
- standard injection molding
- Gas-assisted injection moulding.
- 2K – 2-component injection molding
- Thin-wall injection moulding.
What makes it a good production alternative? It is a good option to guarantee reliability and consistency in high volume production. Besides, once the initial costs of the design and the moulds have been covered, the price of manufacturing is low and the production costs decrease as more parts are produced. Not to mention it generates minimal wastage when compared to traditional manufacturing techniques.
Mould design
When designing a mould for injection moulding there are several factors that must be borne in mind. This process is known as design for manufacturing or manufacturability (DfM).
The first decision is what material will be the mould made of. Normally they tend to be produced in metal, often aluminium or steel, however these two materials present some differences that must be stated. Steel moulds are more durable but also more expensive than aluminium moulds. For its part, aluminium moulds are cheaper but not the best candidates to high volume production or parts with narrow dimensional tolerances, as they have inferior mechanical properties which can lead to deformation and damage when applying the injection and clamping forces.
The second factor to consider is the shape. This part requires careful design and knowing very well the features of the part that needs to be manufactured. It is worth noting here that moulds can be made of single or multiple cavities. The latter can have identical parts in each cavity or can be unique to create parts of different geometries.
Even if designing the optimal mould can have considerable costs, there are several ways in which you can cheapen the process without compromising quality. Note down!
- Remove unnecessary features.
- Eliminate undercuts.
- Use a core cavity approach.
- Reduce cosmetic finishes.
- Design parts that self-mate.
- Monitor DfM analysis.
- Use a multi cavity or family type of mould.
- Consider your part sizes.
Applications
Injection moulding is the most common method for manufacturing plastic parts, particularly in high volumes. It is also used for a broad range of applications where mass production is required, such as packaging, bottle tops, toys, combs, wire spools, musical instruments (and components), chairs, mechanical and automotive parts or components.
In particular, there are four industries where plastic injection moulding applications are specially used:
Construction
Agrifood
Medical
Automotive
Home Appliances
HVAC
Construction
There are several reasons why this method is suitable for use in construction, being the most highlighted ones: the high stability of the materials, exceptional durability, better cost-effectiveness, lightweight and a broad range of finishes and materials. Some of the most commonly-produced elements in the construction industry are small and large accessories, fasteners or hand tools.
Agrifood
A key point in this industry is the need to ensure the wellbeing of individuals when using the products. In order to do so, moulded parts have to be BPA-free and completely non-toxic. The most commonly-manufactured parts for this industry are: containers for beverage and food, components for processing equipment, parts for filtering and dispensing beverages or overcaps.
Medical
Plastic parts manufactured for the medical and pharmaceutical industry have to follow strict regulations. Among them, materials need to have some chemical properties, such as high tensile strength or extremely high resistance to high temperatures. Here is where plastic injection moulding comes into play. Some of the most common parts produced with this process include testing kits, surgical preparation products dental X-ray components as well as casings and covers for medical equipment.
Automotive
Due to its high degree of flexibility and durability, plastic injection moulded parts are very frequently used in the automotive industry and namely for interior as well as exterior applications. The components, such as mirror housings, cup holders, bumpers, fenders and many other standard automotive components are manufactured for the most renowned OEMs and Tier 1 clients in our facility in Wrocław Poland.
Home Appliances
Injection molded components are widely used in home appliances sector. We find them in the form of aesthetic and easy to clean drawers and shelves in equipment like refrigerators. The injection molding technology is also widely used in the washing machine production. At Knauf Industries we manufacture injected washing machine tanks, doors, panels and many other components that comprise modern domestic appliances.
HVAC
As far as HVAC sector is concerned there is also a wide range of applications where injection molding is the best component manufacturing technology. Casings, frames, covers and many other custom-designed intricate plastic components can be found in fans, heaters and various HVAC system parts.
Experts in Plastic Injection
Knauf Industries has been a plastic injection expert for 20 years in France and in Poland.
Our 3 plastic injection facilities enable us to roll out our expertise in injecting small and large (from 5g to 15kg), complex and decorative items to the international market. Precisely, we have special knowledge in IML customisation.
Our plastic injection moulding services also include another field of vast expertise: thermoplastic injection and of plastic parts for the automotive industry. Our know-how here includes standard, gas-assisted injection as well as 2k – two-component injection. Furthermore, we ensure the whole set of assembly services which complement our manufacuturing offer. Clips and tapes application can be carried out manually or with the use of our 6-axis robots depending on the process requirements.
The best part? Our services include much more than injection moulding machinery. We offer you a dedicated team of specialized engineers on every step of the process from feasibility study, through tool development coordination till the mass production.
What’s more we are valued by our clients forflexibility and responsiveness in our service.
Do not hesitate to consult your project with us!