Injection Molding, Explained
This cost-effective and efficient manufacturing process is rather complex. Injection molding involves melting a material and injecting it into a specific mold with a hydraulic or electric machine and is set, resulting in shaped rubber or plastic. This process is used widely today because of the flexibility in mold design and type of plastic used, efficiency in production, and low-cost manufacturing. Injection molding is used to create many medical devices since the process allows complete control over the product’s dimensions, materials, and sterilization to meet strict regulations set by the FDA.
Manufacturers have to choose the correct materials to create medical devices using injection molding
Thermoplastics
Since polymers are considered to be a better fit for many medical applications than most metals, injection molding has become a popular choice in medical manufacturing. Thermoplastics are the most commonly used plastic in injection molding due to their unique characteristics. These specific polymers have the capability to be melted and molded repeatedly, making them recyclable. Additionally, they are resistant to chemicals, making thermoplastics ideal for medical and scientific use.
With multiple types of thermoplastics, there are certain uses for each of the common thermoplastic polymers. Polyethylene is commonly used for medical tubing, bottles, and plastic surgery implants because it does not degrade in the body and is corrosion-resistant. Polypropylene is used for disposable syringes, reusable plastic containers, and prescription bottles. For diagnostic tools, such as test tubes and tissue-culture trays, polystyrene is used. Disposable medical devices like catheters and blood bags are created from polyvinyl chloride (PVC). ABS or acrylonitrile butadiene styrene is used in the manufacturing of nonabsorbable sutures, tendon prostheses, tracheal tubing, and drug-delivery systems (such as IV tubing).
Elastomers
Elastomers are known for their elasticity. They are held together with weaker molecular bonds, allowing them to flex and move more than some of their plastic counterparts while still being durable. Elastomers are commonly used to make ventilation tubes, IV tubes and bags, catheter bags, and orthopedic gels.
Biocompatible Polymers
Biocompatibility is important for applications in which it is important that the immune system can function properly. These polymers do not affect the immune system at all. Blood bags, catheters, sutures, surgical and medical devices, artificial heart components, and artificial tendons are all made from biocompatible polymers.
Applications of Injection Molding in Medical Devices
Many medical devices are injection molded. Plastic has become the top choice for many medical applications because of its ability to be easily formed, its flexibility, its lower cost, and its capacity to survive in the human body without degrading.
Thermoplastics are generally used to create medical devices, as it is the most common plastic used in manufacturing. It can be recycled and remolded, but it also doesn’t corrode or retain moisture, making it a good fit for applications both in and out of the body. Applications of injection molding in medical devices include syringes, IV catheters, respiratory devices, surgical instruments, orthopedic and cardiac implants, dental devices, diagnostic equipment, and medical equipment housings.
Advantages of Injection Molding for Medical Device Production
Medical devices need to be safe, durable, and dependable to keep patients safe. Plastic injection molding is a cost-effective option that creates precise, corrosion-resistant, sterile medical devices.
Cost-Effective
Producing medical devices in high volumes can be costly. Injection molding manufacturing offers automated technology to reduce labor costs and speed up production while also producing large volumes of high-quality products.
Precision and Consistency
The automation and the use of molding ensure precise dimensions for consistency throughout production. These capabilities align with the tight tolerances required by the FDA and other associations when producing medical equipment.
Create Complex Geometries
Since the melted plastic is injected into the mold under extremely high pressure, the plastic is able to be pushed up against all edges of the mold, allowing complex geometries with great detail to be produced. This is especially beneficial for complex medical devices that require immense detail.
Fast Production Cycles
Production cycle times are rapid once the mold is produced. Automation helps create high volumes of nearly identical products in minutes, sometimes even seconds.
Scalability
With the ability to control how much you are producing and how you are producing it, you have full control of the injection molding process. From a high-volume production to a low-volume production, you have control over the production of your injection molding.
Sterilization
The plastic used in injection molding for medical devices is designed to be resistant to contaminants and chemical corrosion, making it easy to keep sterile and sterilized when needed. This advantage allows injection molded medical devices and equipment to meet FDA requirements and standards easily.
Challenges Associated with Injection Molding for Medical Devices
While injection molded medical devices offer many advantages, there are a few challenges that you can run into.
Complex Geometries and Thin-Walled Designs
Thin-walled designs are great for creating lighter and thinner devices with shorter cooling times, however, there are some challenges that come with the thinner material, especially when working with a complex design. You need higher pressure and faster speeds to make sure all of the cavities in the mold are filled. If you don’t have this pressure, there can be unformed areas, warps, or cracks. You can avoid this by taking your material into consideration and making sure you have uniform wall thickness.
Controlling Variations in the Manufacturing Process
Production line variations can cause deformities in your products. Unwanted excess material, shrinkage, sink marks, and air pockets are all some of the defects that can occur to your product if the manufacturing process isn’t consistent or if the environment is changed. It is important to regulate temperature and humidity to reduce the likelihood of this occurring.
Meeting Stringent Quality and Regulatory Standards
Medical devices have some of the strictest and most important regulations and standards on the market. Because they are used in and on humans, it is necessary these devices meet all standards so as to not put the patient at risk. The FDA divides medical devices into classes based on their functions and each one has different standards they must meet. There are also other common standards that must be met, such as ISO 13485 for medical devices, ISO 10993 for the biological evaluation of medical devices, and ISO 14644 for cleanrooms and controlled environments. Quality control and choosing the proper medical-grade plastic are crucial to meeting these standards.
Advancements and Trends in Medical Device Injection Molding
Medicine and technology are always advancing and medical device injection molding has to grow with them. From materials to the technology used in manufacturing, new trends are emerging constantly.
Integration of Additive Manufacturing with 3D Printing
Fabricating metal molds for injection molding is time-consuming and extremely expensive. With the integration of 3D printing technology, medical device injection molding manufacturers are able to eliminate the costly, time-consuming process of metal mold fabrication. These molds can be produced in-house and decrease production time and cost.
Use of Advanced Materials and Biocompatible Polymers
It is important that medical devices don’t affect the way the human immune system functions. Medical device injection molding manufacturers have turned to biocompatible polymers, plastics that do not affect the function of the immune system, to ensure the product can be integrated into the human body without unnecessary complications.
Automation and Robotics in Injection Molding Processes
Automation and robotics are making their way into every part of manufacturing. Automation through robotics makes injection molding more sustainable, increases production speed, and reduces labor costs.
Work with SEA-LECT Plastics for Your Medical Device Needs
SEA-LECT Plastics is a top-tier manufacturer for supporting the medical industry through rapid prototyping, mold creation, and design engineering. Our quality standards, recognized through our ISO 9001: 2015 certification, keeps our molded products in pristine condition before distribution.
Our production of plastics for the medical industry reduces manufacturing side effects, reduces tool investment, offers unlimited design options, provides biocompatibility and corrosion resistance, and is regulatory compliant for medical tubing, implants, surgical and dental instruments, diagnostic equipment, and prosthetics.
If you are considering using plastic injection molding for your medical device needs, contact our team of experts to see how we can help you.