Medical injection molding is the most common process for producing medical supplies. Medical plastics are melted and then formed and molded into the desired shape of the medical device.
This additive manufacturing process creates robust, long-lasting medical injection molded parts with high-quality surface properties and high dimensional accuracy. Since many medical instruments are intended for single use, this technique is also suitable for high-volume production while reducing production costs for injection molding.
Why use plastics for injection medical devices?
All materials used in the manufacture of medical devices must meet industry standards. Thermoplastics, especially so-called “medical plastics”, meet all FDA requirements and are therefore an excellent material for the production of injection medical devices.
Furthermore, plastic polymers are comparatively cheaper than metals and alloys but offer comparable durability and mechanical properties. Using plastics to produce medical devices is therefore a sensible way to reduce healthcare costs without compromising quality.
On the other hand, plastics are generally more flexible in processing during the manufacturing process and even in terms of usability of the final products. Unlike metals, plastics are inert materials. Therefore, they are often the best choice for manufacturing components that interact with organic tissues.
Advantages of injection molding for the medical industry
Injection molding is an automated process used to quickly produce parts and components for medical devices. Its advantages exceed those of similar additive manufacturing processes such as plastic extrusion. That includes:
1. Compliance with industry standards
Components manufactured by medical injection molding are suitable for use in the medical industry because they meet government regulations. The FDA has established a series of requirements related to safety, sterility, cleanliness, etc., that all devices must meet.
Unlike metals and other materials, these plastics are easy to clean and sterilize, are resistant to contaminants and require fewer post-processing requirements, making them ideal for the medical industry.
2. Value for money
Medical plastics injection molding is automated and cost-effective, especially in large quantity production. As it is a computer-controlled process, less labor is required, ensuring lower costs per part. Furthermore, the injection molding process is faster and allows the reuse of molds, further reducing medical device production costs.
3. Compatibility with a variety of materials
During the injection molding process, machinists can choose between different materials. The technique is suitable for plastics, fibers, composites, etc. However, since this is plastic injection molding for the medical industry, we have already optimized the required material. However, the process is compatible with virtually all medical plastics.
4. High precision and accuracy
The medical industry demands exceptional dimensional accuracy in its devices because it works with blood and various internal structures of the human body. A simple deviation of a few millimeters can be harmful to the patient.
However, injection molding is ideal for achieving the highest dimensional accuracy and tight tolerances in plastic production. Furthermore, as it is an automated process, less human influence is required, eliminating errors caused by external interference.
5. High reproducibility
Many medical products such as syringes, gloves, masks, etc. are intended for single use. Therefore, the need for a manufacturing process with high repeatability is one of the main advantages of injection molding.
This technique allows you to produce thousands of precise parts without the need for maintenance after creating the mold. A typical aluminum mold – the most common for injection molding – can survive thousands of production cycles.
6. Little or no material loss
As with any manufacturing technique, medical injection molding creates waste – excess waste is created during the manufacturing of your parts. Unlike other processes, the advantage of this technique is that you can grind and melt this waste and reuse it to make other parts. Therefore, the waste generated after the production of your medical prototype is almost negligible.
Different Types of Medical Device Injection Molding Processes
Now let's take a quick look at some injection molding processes used in the production of medical devices.
Plastic injection molding (normal)
During injection molding, plastic polymers are liquefied at high temperatures before being molded into the desired shape in an aluminum or steel mold. Plastic injection molding is of great value to the medical industry because the process takes place under hygienic conditions. The high temperatures used to melt plastics ensure that they are free from contaminants and microbes that could harm patients' health.
Overmolding
Overmolding is a type of injection molding in which one or two components are molded onto an already formed and cured structure – the substrate. The process is called two-component injection molding because it requires at least two steps and therefore has a long production cycle. However, this technique is valuable for plastics manufacturing, particularly in manufacturing cables and components that require a firm grip.
Insert template
Insert molding is similar to overmolding in that a secondary component is molded onto an already molded part – the insert. Unlike overmolding, insert molding is a unique process because the substrate (inserts) is a pre-existing structure. Furthermore, this technique is not limited to plastic parts, as overmolded inserts can be made from metals or alloys.
Liquid silicone injection molding
In this process, the silicone is heated until it melts and then molded into the desired shape of the medical device. Silicone is a typical plastic polymer suitable for use in the medical industry.
However, because silicone molds are not as durable as aluminum or steel molds, silicone injection molding is typically only suitable for producing small quantities of medical parts, especially in the early stages of medical prototyping and product development.
Various medical plastics for medical injection molding
There are several engineering plastic polymers that are suitable for medical injection molding parts. These plastics are mainly thermoplastics and not thermosets because they perform better than thermosets.
1. Polyetheretherketone (PEEK)
PEEK is a widely used engineering thermoplastic with excellent resistance to harsh environmental conditions, including radiation, high temperatures, chemicals, wear, etc.
Furthermore, it guarantees perfect dimensional stability, even after loading. It also has other premium mechanical properties, making it ideal for manufacturing medical devices. Additionally, it is compatible with injection molding and other manufacturing techniques used in the manufacture of medical devices.
2. Polyethylene (PE)
Polyethylene is a common plastic polymer used for medical purposes. It is composed of thousands of ethylene polymers, with the resulting material having high tensile strength and rigidity.
PE's compatibility with biological tissues and its resistance to adverse environmental conditions, including sterilization, make it a valuable plastic for medical injection molding processes. It is suitable for the production of joint prostheses, connectors, tubes, medicine containers, etc.
3. Polycarbonate (PC)
Polycarbonate is a reinforced engineering thermoplastic made from bisphenol A and phosgene condensation. Although it appears transparent, it has excellent mechanical properties including toughness, flexibility, abrasion resistance, fracture resistance, temperature resistance, etc.
It is also very compatible with body tissues, a typical property of medical plastics. It is suitable for producing many medical plastic injection molding parts, such as transparent masks, protective equipment, oxygenators, etc.
4. Polypropylene (PP)
Polypropylene is another common plastic polymer for plastic injection molding created from the condensation of multiple propylene units. It has incredible toughness and is resistant to cracking, radiation, shock, temperature, wear, etc.
For all these reasons, it is a suitable plastic for the production of components for the healthcare sector. It is ideal for the production of connectors, tubes, syringes, knee and hip prostheses, ventilators, etc.
5. Silicone
Silicone is a chemically inert chemical compound, similar to synthetic rubber, has excellent mechanical properties and is compatible with biological tissue. It is the plastic polymer of choice for medical applications where flexibility plays an important role.
It is suitable for manufacturing products and devices such as catheters, cosmetic products, contact lenses, breast implants, drug delivery systems, connectors and tubes, etc. Additionally, silicone is extremely cost-effective in manufacturing medical devices.
6. Polystyrene (PS)
Polystyrene is another premium engineering plastic suitable for manufacturing medical injection parts. Unlike most other thermoplastics discussed previously, it has little or no flexibility, but offers other excellent mechanical properties and is compatible with body tissue.
It is resistant to adverse conditions, ensuring high dimensional stability, crucial for all medical components. It is widely used to make petri dishes, culture dishes and other diagnostic parts.
What materials are the available medical injection parts made of?
There are several thermoplastics used to manufacture injection parts for hospitals and medical purposes. However, each polymer is best suited for certain applications. Let's discuss the criteria to consider when selecting medical plastics.
1. Industry Regulations (FDA)
When developing components for medical devices, compliance with regulations from relevant authorities, especially the FDA, must first be taken into consideration. Every medical instrument must meet certain guidelines and requirements before being released to the general public.
These standards include compatibility with biological tissues and the ability to withstand extreme physical and chemical conditions. Other criteria are also subject to these regulations. Therefore, if plastics meet all FDA regulations, they are suitable for the production of medical plastic injection molded parts.
2. Strength and durability
Plastics used to produce injection molded medical parts must have distinct mechanical properties in terms of strength, stiffness and durability. When developing components for the healthcare sector, it is important to avoid fragile plastics that can break easily. Instead, use impact- and shatter-resistant thermoplastics that serve their purpose for long periods of time.
3. Adequacy of the environment within the organism
Some medical products, such as prosthetics and surgical implants, come into direct contact with organic tissues. Therefore, plastic polymers for such products must be inert and must not interfere with the normal activities of the body. Instead, they must remain compatible with the environment of the body's internal structures, even after prolonged use.
4. Ability to withstand sterilization conditions
Many medical devices must be sterile – free of contaminants and microorganisms that could be harmful to patients. However, these medical devices are exposed to adverse conditions during the sterilization process, such as high temperatures, radiation or chemicals.
Therefore, plastic polymers used in the manufacture of instruments that require sterilization must maintain their dimensional accuracy even after exposure to these aggressive environments.
5. Selection of molding method
The injection molding process is also a criterion that must be taken into account when selecting the correct medical plastic. When processing silicone, for example, the liquid silicone injection molding process is best suited for such manufacturing processes.
Other plastic injection molding techniques include insert molding, micromolding, ultrasonic bonding, overmolding, etc.
6. Consider general usage
The intended use of the manufactured components is another aspect that must be taken into consideration when using plastic polymers for medical injection molding processes. For example, medical devices such as gloves, masks, ventilators, tubes, catheters and syringes are intended for single use only.
Therefore, few materials must be used in the manufacture of such components; they must be flexible, light, transparent and easy to sterilize. Spending a lot of money on these products would be very expensive and unwise for the manufacturer.
Plastic injection molding applications in medical devices
Given the advantages discussed above, you will agree that injection molding is an extremely efficient and effective manufacturing technique for the medical industry. It is a continuous process that offers high precision and accuracy even when producing large quantities. This makes it the preferred method for many companies that produce components for the medical and pharmaceutical industries.
The process is widely used to produce the following medical plastic injection molded parts.
- Knee and hip replacements
- Various implants and surgical devices
- Simple and essential components such as blood bags, syringes, catheters, connectors, tubes, ventilators, masks and protective equipment
- Enclosures, panels and covers for advanced medical devices such as MRI and ECG machines
- Components such as Petri dishes, elevators, test tubes, etc. for laboratory testing.
- Dental x-ray equipment
- Orthopedics
- Pharmaceutical containers and packaging
WayKen: Your Injection Molding Services Expert
We have a team with extensive experience in injection molding and can produce more sophisticated aluminum molds and steel molds depending on your machining needs. We also offer professional advice on choosing the right material for your medical injection parts so that you get a high-quality and cost-effective final product.
Simply upload your CAD files and we will provide a free DfM analysis and insights into how your manufacturing is carried out.
Concluding
Medical injection molding is cost-effective and allows the production of high-quality products with excellent mechanical and chemical properties. Injection molding makes it relatively easy to produce both simple medical injection molded parts and complex components that require tight tolerances.
Common questions
What are medical plastics?
Medical plastics are plastic polymers used to manufacture medical products and devices. These plastics are biologically inert and have undergone tests and stability studies that ensure their safety and compliance with industry standards. They have excellent mechanical, physical and chemical properties. Some examples are polyethylene, PEEK, polypropylene, ABS, etc.
What is an injection molding medical device?
Medical device injection molding simply refers to the application of injection molding techniques in the manufacturing of medical devices. Medical injection molded parts are manufactured by heating plastic components until they are melted before molding them into appropriate shapes that conform to specific designs and are intended for use as medical device components.
What types of medical products are available for injection molding?
Medical injection molding can be used to produce virtually all plastic medical devices because the technique meets all FDA safety and structural stability regulations. Simple devices such as Petri dishes, syringes, tubes and blood bags, as well as complex structures such as implants, casings and covers for large medical devices, prosthetics, etc., are all compatible with plastic injection molding processes.
