What is the bi-material injection moulding process?
Bi-material injection moulding is a process in which two different materials are used in a single part during the plastic injection moulding process.
This can be useful to create parts with properties such as stiffness in certain areas and flexibility in others, or to add features such as wear or corrosion resistance to specific parts of the part.
It is a very interesting technique that allows for greater versatility in the design and manufacture of plastic components.
Applications of bi-material parts
Bi-material parts that combine a rigid material with a soft rubber-like material have a wide range of applications in various industries.
Some common examples include:
1. Seals and gaskets: The combination of a rigid material with a soft rubber-like material is ideal for seals and gaskets in applications where compressive strength and flexibility are required to seal irregular surfaces.
2. Ergonomic grips: In tools, medical devices or consumer products, bi-material grips offer user comfort by combining the firmness of the rigid material with the softness and grip of the soft material.
3. Shock absorbers and shock absorption: In applications where shock or vibration absorption is needed, bimaterial feet can be used to absorb shock and vibration.
4. Automotive components: Bi-material parts are used in interior panels, door handles, switch controls, among others, to combine structural strength with comfort and aesthetics.
5. Medical devices: In medical devices such as surgical instruments or diagnostic equipment, bi-material parts offer the possibility to combine specific functionalities such as rigidity for handling and flexibility for patient contact.
Success story: Mudguard
A mudguard is a part that is placed on the underside of a vehicle, usually at the front or rear, to protect the inside of the wheels and nearby components from dirt, stones, water or other debris that may be projected from the road while the vehicle is in motion.
These mudguards not only help to keep the vehicle's internal components clean, but also help to prevent impact damage and improve aerodynamics by reducing air resistance.
They are therefore important components for the protection and performance of the car.
Injection moulding technology: 2-step bi-material injection moulding
Two-step bi-material injection moulding, using 2 separate moulds, is a process in which a plastic part made of two different materials is manufactured using two separate moulding operations.
In the first step, a material, in this case a rigid material (PP-Polypropylene) is injected into a mould to create a partially formed part.
This partial part is then removed from the first mould and placed in a second mould.
In the second step, the second soft material (SEBS - thermoplastic elastomer) is injected around a part of the part to perform the sealing function once assembled.
Considerations for bi-material injection moulding
Some key points to take into account in the injection of bimaterial parts are:
1. Selection of materials: It is essential to choose compatible materials that adhere correctly during the injection process to ensure the strength and durability of the final part.
2. Mould design: The mould design must allow the injection of the two materials in a precise way and ensure a proper bond between them.
3. Temperature and pressure control: It is important to maintain optimum temperature and pressure conditions during the entire injection process to avoid problems such as bond marks or deformation of the part.
4. Testing and Adjustment: Pilot testing and adjustment of the injection process is essential to optimize the quality and performance of bi-material parts.
OSF: Specialists in Bimaterial Injection Moulding for Custom Projects
At OSF we can manufacture bi-material parts with both technologies:
- Part Transfer Injection moulding: the machine has two units, one for each part and one for each part.
With a robotic or manual system, the part to be over-injected is moved into the cavity where the second material is injected.
A single mould is produced in which the two materials are injected.
At OSF we have two 50Tn machines with this technology.
- Injection in two steps: it is injected in two different machines and two independent moulds are made.
First the first part of the part is injected on one machine and then the other part is over-injected on a second machine.
In this case, standard injection moulding machines can be used.
At OSF we analyze our customer's individual project to propose the materials and technology best adapted to their needs.
For more information, please contact us.
