Multi Durometer Molding
April 18, 2024Multi durometer injection molding
Commonly referred to as Dual Durometer Injection Molding, this type of Two Shot Injectoin involves utilizing materials of varying hardness – one being flexible and the other rigid.
Through a co-extrusion process, dual durometer extrusion combines these two materials by simultaneously extruding them through the same mold, resulting in the creation of a unified component.
Manufacturers may choose dual durometer extrusion when seeking a product that encompasses a blend of soft and durable materials.
What Durometer means?
Durometer is a measure of the hardness of a material, particularly for polymers, elastomers, and rubbers. A lower durometer indicates a softer material, while a higher durometer signifies a harder material.
The process and purpose of multi-durometer injection molding can be understood as follows:
1. Process
Initial Molding: Similar to the overmolding process, the initial part, often made from a harder plastic, is molded first.
Once the initial part has cooled or semi-cooled, it’s placed in another mold or remains in the same mold (depending on the mold’s design) for the secondary injection.
The secondary material, which can be softer or harder depending on the design requirements, is then injected.
This second material will form around or alongside the initial part, adhering to it.
After cooling, the two materials, having different hardness values, become one integrated part.
Utilizing dual durometer extrusion enables you to:
Incorporate multiple colors
Include pre-made holes, notches, slots, or other shapes
Attach Pressure-Sensitive Adhesives (PSAs) directly onto the component
Develop a visually appealing part
Utilize a more affordable “filler” material for cost-effective parts
This technique serves to bridge the divide between customer demands and production constraints. Importantly, it does not necessitate significant initial expenses to implement these modifications.
2. Advantages
Allows for parts with varying hardness to be produced in a single step, reducing assembly processes.
- Eliminates the need for compromise in a design
- Cuts down on post-processing cost and time
- Improves reliability of the final part
- Allows a combination of material properties in one piece
Gives designers more flexibility in part design, allowing for a balance between rigidity and flexibility in specific areas of a part.
The ability to combine hard and soft materials can improve the overall functionality and user experience of a product.
Instead of fabricating and joining two distinct components, the entire process is completed in a single step. This results in cost savings for manufacturers in terms of equipment, production time, labor, and storage space.
In certain scenarios, a more economical “filler” material may be utilized to reduce the overall cost of raw materials for each component, while still maintaining acceptable material properties.
This approach is particularly beneficial for the production of mass-consumer goods.
3. Applications
Commonly found in tool handles, medical devices, or consumer electronics, where one part needs to be rigid (hard) for structural purposes and another part soft for comfort.
In cases where a part needs a rigid structure but also requires an integrated soft seal.
Like those on flip-top caps, where a rigid cap might have a flexible hinge made from a softer material.
The primary application of dual durometer extrusion is combining a sealing material with an attachment material.
The softer material is utilized for the seal, while the harder material is used for attachment purposes.
If you have experience working with gaskets, you are aware that achieving a reliable seal necessitates additional machining and post-processing.
Dual durometer extrusion addresses this issue, leading to time and cost savings.
As a result, various industries can derive advantages from dual durometer extrusion. Industrial and commercial businesses engaged in extrusion-based product manufacturing can explore dual durometer extrusion as a viable option.
This manufacturing technique offers opportunities for innovative and effective solutions to challenging products in diverse industries
4. Challenges
It’s crucial to ensure that the materials selected bond well with each other during the molding process.
The material limitations are the same as standard extrusion processes. It mainly consists of plastics of varying durometers:
- Acetal
- Acrylonitrile Butadiene Styrene (ABS)
- Polycarbonate
- Polyvinyl Chloride (PVC)
- Polyethylene
- Nylon
- Thermoplastic Elastomer (TPE) and Thermoplastic Rubber (TPR)
- Thermoplastic Polyurethane (TPU)
- Polyethylene Terephthalate (PET)
- High Density Polyethylene (HDPE)
Designing molds and processes for multi-durometer molding can be more complex than for single material parts.
As with overmolding, ensuring a strong bond between materials of different hardness requires precision in temperature, pressure, and other process parameters.
Summary
Essentially, it’s a variation of overmolding but focuses on the specific characteristic of material hardness. It is a specialized injection molding technique that allows for the simultaneous or sequential molding of materials with different hardness (or durometer) values into a single part.
Acquiring an understanding of the operational principles of dual durometer extrusion is the essential initial step in incorporating this manufacturing technique into your processes.
When there is a demand for cost-effective and dependable units that possess a combination of material properties, multi durometer extrusion often emerges as the optimum solution.
Have Questions about Plastic Injection Molding?
Please contact us, and we shall be happy to answer them!