When to use plastic injection molding for medical parts
Plastics have revolutionized the medical industry. Not only does plastic lower the spread of infection, but it’s also an affordable material and when used in the injection molding process, they can deliver precise, lightweight and durable devices.
The different polymers available are vast and can be formulated specifically for healthcare applications. These plastics don’t harbor pathogens and can stand up to different sterilization processes. Plastics have given us one-time-use tools and devices, such as surgical gloves, syringes and IV tubes. These materials are also used for durable applications, such as hospital beds and medical equipment.
The benefits of plastics in medical fields, from dentistry to orthopedics, are many. So are the advantages of the medical injection manufacturing process. If you’re not familiar with plastic injection molding, we suggest you read In-depth: the injection molding process. We’ll give a quick summary of the process here:
- A mold is made from metal and precision machined to match the geometries and measurements of the product you’re manufacturing.
- Plastic resins are fed into a heated barrel and mixed.
- Heating bands melt the resins.
- The molten plastic is then injected into the mold cavity, where it cools and hardens.
- When the plastic solidifies, the part is ejected from the mold.
You can learn more about this process in The future of injection molding and in the video Injection Molding: How does it work?
Plastic insert molding is a close cousin of injection molding. This takes an already fabricated component, such as a surgical knife blade or surgical tube, and encapsulates it in molten resin to manufacture a finished product. Plastic injection molding involves injecting one or more molten plastic resins into a mold to produce single, finished parts.
Examples of products made with plastic injection molding for the medical-device industry:
- Beakers
- Test tubes
- Lab and clinic housings and casings
- Implantable components
- Surgical blades
- Surgical tools
- Pacemaker parts
- Orthopedic and dental instruments
- Needle housing
- Instrument handles
- Suture delivery devices
- Prosthetics
Now the question is, why produce your plastic components for medical devices with plastic injection molding, versus another process? The reasons vary:
Compliance
In order for any medical device to reach the market, it has to satisfy FDA regulations, which recognize ISO standards. Plastic injection molding is a controlled process, which makes it easier to meet ISO compliance. Examples include the tight controls on materials and measures taken to prevent contamination. Even the manufacturing facility itself is controlled to help regulate temperatures.
Note, in order to meet plastic injection-molding standards, the manufacturer must be ISO 13485 certified, which sets out standards for quality management systems.
Cost efficiency
Plastic-injection-molding medical parts offer significant cost benefits. The molding tool and die require a high up-front cost compared to other manufacturing processes, but the mold only needs to be created once. After hundreds of thousands of runs, it may need to be replaced, but this will be easier and cheaper to recreate.
The benefit is in the overall costs. Injection molding is efficient and fast. You can do high-volume production runs with lower per-part costs. In other words, the more parts you produce, the lower the cost. If you’re manufacturing components or devices in bulk, plastic injection molding will almost always be the most cost-effective option.
Precision
There is no official designation of medical-grade plastic, but for plastics used in medical devices to be considered as such, it must be compatible with our body’s biological system. The overall device, which includes materials, must satisfy regulatory requirements in order to reach the market. Part of those requirements include specifications.
Medical injection molding enables devices to be manufactured to your exacting specifications. Tolerances in medical device molding are tight. As technologies continue to advance, those tolerances become even tighter. The more complex the part, the tighter the tolerance should be to ensure a uniform performance at scale, which makes plastic injection molding the ideal manufacturing process for critical parts.
Design flexibility
Plastic injection molding does have a few restrictions, such as the need to avoid sharp corners, which increases stress concentration. Also, wall thickness should be uniform to prevent inconsistencies in the cooling process, which can cause defects.
Still, you have a lot of leeway regarding your design. Medical plastic molding allows complex geometries and intricate designs, for example. Medical plastic parts form in the mold cavity, so you can achieve different features with just one injection. Designing for different features with another process would take costly, multiple assemblies.
Reduced weight of device
Plastics in the medical field possess unique mechanical properties designed to improve the performance of medical devices while reducing their weight. This is critical, as it diminishes the fatigue surgeons experience while performing long procedures.
Medical injection parts also enable patients who depend on continuous monitoring with wearable medical devices to go about their daily lives. Another benefit to lightweight medical plastic parts is the convenience they offer EMTs, who have to carry them to attend patients in emergencies.
Durability
Plastics that must be biocompatible are formulated for those properties. As the resins are to be used in injection molding, they also contain another quality: durability. Plastic-injection-molding medical parts are incredibly strong and can stand up to heat in autoclaves, which is necessary for sterilization. These materials also resist impact and vibration, making them versatile for medical applications.
Plastic injection molding vs other processes
Is the medical injection manufacturing process the most appropriate for your application? To help you make the right decision, we’ve devised the table below.
| Plastic injection molding | Medical plastics machining – CNC | Fused deposition modeling (FDM) | Selective laser sintering (SLS) | Sterolithography (SLA) | |
| Typical applications | Casings/housings, surgical parts, syringes, containers, test tubes, beakers | Bone and joint replacements, catheters | Biomedical implants, surgical devices | Dental tools, hearing aids | Biomedical implants |
| Low-to-medium volume | X | ||||
| High volume | X | X | |||
| High-dimensional accuracy | X | X | X | ||
| Not suitable for intricate details | X | ||||
| Complex geographies | X | X | |||
| Complex geographies | X | ||||
| Cost-effective for custom parts | X | ||||
| Wide range of thermoplastics | X | X | |||
| Mechanical properties degrade over time when exposed to sunlight | X | ||||
| Long lead times | X | X | |||
| Short lead times | X | ||||
| Short production time | X |
What else should you know?
The more you know, the better decisions you can make. These topics provide in-depth information to help you learn more:
You’ll also need components for your design. These guides tell you about solutions already being used in the medical industry, from handles to cable management.
Download free CADs and try before you buy
Download free CADs and request free samples, which are available for most of our solutions. It’s a great way to ensure you’ve chosen exactly what you need. If you’re not quite sure which product will work best for your medical device, don’t worry. Our experts are always happy to advise you. Whatever your requirements, you can depend on fast despatch.
Request your free samples or download free CADs now.
Questions?
Email us at sales@essentracomponents.com or speak to one of our experts for further information on the ideal solution for your application 800-847-0486.