In simple words, medical injection molding is the process of manufacturing high-quality medical parts. In this process, thermoplastic is injected into a mold cavity. The process should comply with the FDA and ISO 13485. Medical injection molding also makes manufacturing other complicated implants difficult. The common examples are drug delivery devices and surgical instruments.
In this article, you will acquire in-depth knowledge of the following areas:
- How do you select materials for medical injection molding parts?
- Medical Mold Design and Manufacturing
- Biocompatible Polymers
- Applications
- Compliance and Quality
Material Selection and Preparation for Medical Injection Molding
Biocompatible Polymers
Choosing a material for a medical device is a vital step in development. Every material selected is unique to the needs of the device and not accidental. All biocompatibility standards, for example, ISO 10993 and USP Class VI, are met. These standards keep the material safe from biological incompatibility for production utilization.
Mechanical Properties
The mechanical properties of the materials studied include essential characteristics such as tensile strength, flexural modulus, impact resistance, and fatigue life. These have to be essential for proper functioning in the desired application.
Sterilization Compatibility
The second critical parameter of a stent is compatibility for sterilization. It must be indifferent to commonly employed sterilization techniques, either an autoclave, gamma irradiation, or ethylene oxide (EtO).
Chemical Resistance
Furthermore, they have to be chemically inert. This means that they should not become active in response to contact with body fluids, drugs, or chemicals. Material selection should take seriously the controlled degradation rate.
| Property | Polycarbonate (PC) | Polypropylene (PP) | PEEK | Silicone (Medical Grade) |
| Tensile Strength | 9,000 – 10,000 psi | 3,000 – 5,000 psi | 14,000 – 17,000 psi | 700 – 1,500 psi |
| Flexural Modulus | 300,000 – 350,000 psi | 150,000 – 250,000 psi | 500,000 – 600,000 psi | Highly variable (low) |
| Impact Strength (Izod notched) | 12-16 ft-lb/in | 0.5 – 1.5 ft-lb/in | 1.0 – 1.5 ft-lb/in |
For example, PLA, PGA, PCL, and their copolymers Such materials are excellent candidates to be used in implants such as sutures and drug delivery systems.
Some such as PEEK, polycarbonate, polypropylene, and certain silicones may be employed with reasonable success due to their high strength and cross-linking potential.
Drying
During drying, we need to dry well to remove the moisture from the materials. If moisture is there in the material then it can act as a defect in the final product. Various methods play a pivotal role in moisture analysis, including Karl Fischer titration.
This gives accurate measurements of the material’s moisture content. However, since the hygroscopic nature of the polymer determines the drying method, suitable methods are chosen. These methods include desiccant drying, vacuum drying, and dehumidifying dryers.
Drying is carefully controlled to minimize the thermal degradation of the material. Adhering to the suggested drying conditions ensures that the material remains high-quality. Skipping this step would endanger the performance and reliability of the final device.
Pelletizing
Materials are processed into consistent pellets so that they provide a uniform melt flow when injected into the mold. The size and shape of the pellets are precisely regulated. It ensures a smooth feed and melts in the injection molding machine.
Contamination is Prevented Using Proper Material Handling Practices. They are kept in clean surroundings and away from moisture.
Mold Design and Manufacturing
Design engineers create high-resolution 3D CAD models of medical devices. They ensure that many stages of production are successful. These designs include features such as cooling channels that maintain the temperature and ejection systems that assist in ejecting the component parts from the molds.
Molds are produced using high-precision machining strategies. A thorough process ensures that the molds obtained adhere to the specific nature of the medical devices.
Operation of Medical Injection Molding Machines
Medical Injection Molding process, the two mold halves are tightly clamped together. Hot, molten plastic is injected under pressure, forming a phase of the mold cavity. Engineers use holding pressure to ensure complete mold filling and achieve uniform part density. These steps help ensure that the molded parts achieve design and quality requirements.
Cooling and Solidification
Once the plastic has been inserted into the mold, the cooling starts. Cooling takes place in a manner such that warping and shrinkage occur nothing at all.
Cooling is necessary to manage pressure so that the material is uniformly distributed. It also applies for contributing decent dimensional stability. Stable cooling profiles are decisive for the high-level production of dimensionally accurate and surface-finished medical devices.
Ejection and Post-Processing
After the molded part has cooled sufficiently, it is ejected from the mold via an ejection system designed for the mold. Part edges are trimmed off to remove excess material – flash. Secondary operations, if required, include machining, assembly, or sterilization. This last step is to ensure the medical devices meet all quality standards for safe and effective use.
Medical Injection Molding Materials
The materials used in medical injection molding must satisfy stringent safety, performance, and regulatory requirements. They should also remain biocompatible and withstand the multiple processes of medical device manufacturing. Thus, they should be stiff and durable. Here are the frequently utilized materials for medical injection molding.
Silicone
Silicone has a significant advantage due to its low biocompatibility. It is extremely flexible and can withstand high temperatures. Therefore, it is quite good for systvac kind of medical application setups; being inert in an organism; does not cause any unwanted reaction with the body tissue.
For this reason, silicone is one of the most used materials for medical devices. Further, its flexibility allows it to fit different shapes and dimensions — an evident need for devices that must adapt to the human body.
Thermoplastic Elastomers (TPEs)
TPEs retain the elasticity of rubber with the processability of plastics. The materials are good for flexible applications because they are soft and pliable. That is why this versatility is characteristic of them. The uses of C203M and C203WN include cases where strength is needed coupled with flexibility.
Polyolefin(Polyethylene and Polypropylene)
For example, polyolefins like PE and PP come with excellent mechanical properties and good chemical chemicals. The resistance to fatigue is very predictable with polypropylene as well.
This feature makes it ideal for applications where it will be repeatedly used. Their resistance to sterilization methods, such as autoclaving and gamma irradiation, makes them suitable materials for single-use medical devices.
Polycarbonates
Polycarbonate is a strong, solid, clear material commonly used in devices that require strength along with transparency. It also possesses good impact resistance-an important property of devices which may undergo stress or impact.
Polyamides (Nylon)
Nylon is very good in high strength, and fatigue resistance. This is a very good material for making surgical instruments and implantable devices. Why are they famous? The reason is that it does not break under repeated stress. Its wear resistance makes it suitable for components with frequent contact or movement.
Medical Device Regulatory Compliance and Quality
Since the medical field is very delicate, injection molding manufacturing ensure strict inspections. For this purpose, there are some regulations which are important for the quality of the product. These regulations include regulatory authorities like the FDA and ISO to ensure product safety and effectiveness.
FDA Regulations and Guidelines
In the US, the FDA regulates medical devices via many standards:
Quality System Regulation (QSR)
This regulation helps maintain different quality standards. For your understanding, these standards are design, production, and post-market of the device lifecycle.
Good Manufacturing Practice (GMP)
GMP provides criteria on quality that would apply when the medical devices are manufactured and stay controlled under the intended use.
Design Controls
These guidelines focus on the documentation process for the entire design of medical devices. This encompasses essentials related to risk assessment requirements:
- Design output validation requirements
- Design verification requirements
- Validation testing requirements.
ISO 13485 is the international standard of medical device quality management systems. This ensures that the manufacturer will follow the best practices and use high-quality processes. Many countries require market authorization by following the ISO 13485 standards.
Medical Injection Molding Applications
Medical injection molding is a process for creating a range of medical products. It is a great method because the products need to be very precise and maintain quality and safety standards.
Medical Device Manufacturing
Orthopedic and dental implants are among the widely injection molded devices. They need to be strong, biocompatible, and at the same time able to give high accuracy. This is because it is also used to make surgical tools.
It comes with scalpels, forceps, and retractors. The reason is that they have to function well in procedures and thus have to be very precise and hard.
Consumable Medical Products
With injection molding, injection molding companies make syringes, IV tubing, catheters, and pipette tips. These products must meet strict safety and performance criteria. Moreover, medical injection molded parts also need tight precision.
Apart from medical devices, sterile packaging solutions are also prepared using injection moulding such as blisters, vials, etc.
Conclusion
Rapid Manufacture accelerates medical injection molding by quickly producing prototypes and small batches. It incorporates faster tooling methods and materials like aluminum. This allows for quick design changes and faster market entry.
