Molded hearing aid device

Medical device injection molding is the process of using medical-grade plastics and injecting them into highly precise molds to make medical components and parts. The process of medical device injection molding is highly precise and accurate, especially for medical-grade devices essential to healthcare. 

The process starts by precisely designing a mold for your components. After which, material selection follows to ensure it aligns with your parts application. After ensuring the prerequisites, the plastic is heated, then injected under high pressure into the mold and left to cool. After cooling, the part is ejected and sent for post-processing and inspection.

The process is primarily used for the production of medical devices that utilize advanced materials, such as thermoplastics like PEEK. Injection molding technology can produce complex geometries with tight tolerances and fine details.

It is a manufacturing process that features great surface finishes and precise measurements, especially for high-volume productions. The method enables the large-scale production of components that meet strict requirements and specifications.

Medical Injection Molding Processes

Insert Molding 

Assorted medical molded components

Insert molding involves molding a plastic or component of a preformed part or insert. It is similar to overmolding. The insert is generally made of metal or a harder, more durable material than the softer plastic. The insert is placed inside the mold, and molten plastic is then injected and forms around the insert. This process basically joins the two components, the insert and plastic, into a single, more durable part.

The process offers two methods for joining and ensuring proper bonding between the insert and the plastic part. One is mechanical bonding, and the other is molecular bonding. In mechanical bonding, the inserts feature threads or knurls where the plastics can set into and hold the inserts firmly. Molecular bonding occurs when the insert and plastic materials share similar chemical structures and polymer chains. They rely on mechanical locking, surface roughening and interfacial bonding. 

Over Molding

Examples of plastic overmolding

Overmolding is similar to insert molding. It involves layering a plastic or polymer over a pre-molded substrate to form a single fused part. It helps eliminate multistep assembly by enabling a component to be produced in a single step. For example, it is used to make handles for surgical tools. The substrate can be a molded surgical part or metal, and overmolding can make grips or shape the handle. Overmolding has one differentiating factor, which is that it molds one material over a premolded part, and typically, the two materials are different.

Thin Wall Molding

Thin-wall injection molding

Thin-wall injection molding is used to make components that require a thin-wall specification of thickness below 1mm. It is used to produce small, complex components that require greater precision.

Thin-wall molding is a molding technique for very thin features. It uses fewer materials, and this is important because the right amount of raw material is needed, meaning you can mass-produce parts for high-volume runs. It is used to make lightweight and durable medical device housings.

Liquid Silicone Rubber Molding

Liquid silicon rubber (LSR) injection molding is fast and precise. LSR is a two-part elastomer that sets when its molecules crosslink and form a bond. The process of injecting liquid silicone into a mold under high pressure and waiting for it to cure. Typically, its curing time ranges from 10 to 90 seconds. 

LSR requires a clean, hygienic environment to prevent impurities from contaminating it. LSR is mainly used to make surgical parts and instruments that require flexibility and biocompatibility, such as catheters and seals. 

Metal Injection Molding (MIM)

Precision gear mold tool

Metal injection molding works by combining metallic powder with binders to form a paste, which can then be injected into the mold and then formed. The molded part then undergoes a heating process called sintering, which helps remove the binders and densify the metal. It is mainly used for making high-volume, small, complex parts for the medical industry.

Others

Other manufacturing processes include micro injection molding, which is highly precise, 2-shot molding, and gas-assisted molding.

Material Used In Medical Device Injection Molding

Medical device injection mold is a versatile and broad process that works with different materials. Some common injection molding materials are listed below:

PEEK

High-performance PEEK implants

Polyetheretherketone is a highly durable, biocompatible thermoplastic. It has great wear resistance and dimensional stability. It can withstand high temperatures and radiation, making it a perfect choice for the medical industry. PEEK has excellent mechanical properties, which prevent its failure under elevated stress. It is commonly used to make implants and surgical tools that need excellent dimensional stability.

Silicone

Silicon is a two-part elastomer. It is a unique compound that is similar to rubber and has rubber-like behavior and exceptional mechanical properties for medical devices. It is biocompatible and flexible, which makes it the first choice when it comes to injection molding for medical devices. It is commonly used for tubing, gloves, catheters, and medical instruments.

Polypropylene

Polypropylene is a rigid and strong plastic polymer with great strength and resistance to cracking and impact. It forms tight seals, which is why it is widely used for fluid storage applications like lab vials and medical containers.

Syringes and connectors used in the medical industry are made from PP because it can withstand sterilization. For high-stress orthopedic applications like joint liners, you can use UHMWPE to minimize metal-on-metal contact. 

Polyerthylene

Polyethylene is biocompatible and can withstand harsh environments due to its great tensile strength and durability. Some common applications include connectors and containers. PE has three further types, which are listed below.

• High-density polyethylene (HDPE): It is tough, rigid, and moisture-resistant. It was used ot make bottle closures, caps, and vials for the medical industry.
• Low-density polyethylene (LDPE): It is a translucent and flexible material that I use to make squeezee bottles and various flexible parts.
• Ultra-high-molecular-weight polyethylene (UHMW): It has high impact and wear resistance, making it ideal for orthopedic implants.

Polycarbonate

Polycarbonate is a transparent thermoplastic that has exceptional dimensional stability. It has excellent mechanical properties. It is tough, flexible, and wear-resistant. It is used to make clear protective face shields, surgical tool handles and housings for blood oygenerators. 

Advantages Of Medical Device Injection Molding

Design complexity 

Injection molding for medical devices is highly versatile. It supports various designs of different complexity and precision. It creates parts with intricate designs and tight tolerances around 0.025mm. This is especially beneficial for medical devices that require extreme precision, as any deviation or malfunction can pose safety concerns and affect performance.

Injection molding allows for cavities, inlets, and contours to be molded with ease. Additionally, medical devices have unconventional shapes that can be difficult to machine, making injection molding the perfect choice.

Material Selections

The injection molding process is highly versatile and can accommodate a wide range of materials, primarily plastic polymers and metals. Plastic injection molding of medical parts is the ideal way for the medical industry to manufacture parts. It ensures that biocompatible material for medical devices is used. 

The ability to use different materials allows doctors and designers to experiment with them and select the most appropriate one for the application.

Cost Effectiveness

Injection molding is primarily an automated process, which results in lower labor costs. Since computers oversee the process with precision, they enhance efficiency and minimize mistakes. Injection molding medical parts is ideal for large-volume runs, as the per-part cost decreases. Additionally, injection molding offers fast cycle times of 30-120 seconds. It generates minimal waste and requires minimal post-processing, reducing costs.

Applications of Medical Injection Molding

Medical grade plastic caps

Medical injection molding supports a wide range of health care needs, which range from gloves for protection to surgical instruments to perform operations and implants. Below is a list of common applications of medical injection molding

• Implants: medical implants used in orthopedics, such as knee and hip joints, are made using injection molding because these products have to be durable and bio-compatible, along with high standards. Injection molding fulfills all these requirements. 
• Surgical tools: surgical tool handles such as scalpels, forceps, and clamps are made by overmolding for better grip and control.
• Lab Equipment: Laboratory equipment, such as vial bottles, tongs, droppers, and various other things, such as microplates, is all made using medical device injection molding.
• Medical device housing; medical devices and test equipment need enclosures to maintain stable conditions and protect them from the environment.
• Disposable devices: disposable, one-time-use devices such as blood bags, syringes, pipette masks, and similar items are made by injection molding, a quick process that ensures sterility and cleanliness

Medical Devices and Components Produced by Injection Molding

Devices and components produced by injection molding medical parts are listed below;

• Syringe barrels and plungers,
• Catheter hubs and connectors
• Surgical grips
• Handles
• Orthopedic implants
• anchors 
• Diagnostic equipment housings
• Fluid management components

Regulatory Compliance in Medical Molding

Medical injection molding is a highly regulated and strict process that needs to adhere to the standards of regulatory bodies, such as the FDA and ISO, to ensure safety and efficacy. 

ISO

ISO 13485:2016: it is the international quality systems standard that covers medical devices, design, and their production and traceability.  It is the most widely used certification globally for medical device manufacturers.

Iso 10993: it evaluates the biocompatibility of medical devices by evaluating toxicity, sterilization, irritability, etc.

ISO14644: it defines the clean room classifications, such as class 7 and class 8, required for medical device production.

FDA Regulations

• FDA Quality Management System Regulation (QMSR)
• U.S. FDA rule (21 CFR Part 820)

These FDA regulations ensure quality and consistent manufacturing through the auditing, process validation, and good manufacturing practices.

Medical Device Injection Molding Service

The medical device industry requires expert manufacturing and great responsibility with specialized injection molding to work around production problems. Proleantech provides manufacturing precision, cost-effective scalability, and ensures regulatory compliance as an OEM. 

Proleantech is among the top injection molding companies, focusing on accelerated development for critical healthcare applications.

• ISO certifications for cleanroom production with regulatory compliance
• Precision molding and deep tooling for tight tolerances and complex geometries
• Expert medical grade handling of parts and biocompatible materials
• Scalability assistance from prototype to high volume manufacturing

Get a quote for your precision injection molding project today!

Conclusion 

Medical injection molding is a crucial manufacturing process used in the medical industry to make different medical devices and components with high precision and accuracy. It works with common injection molding materials. The biocompatibility of the process and material versatility, and high volume, give it a great advantage over different manufacturing processes. Its compliance with regulations and standards ensures that it meets the medical industry’s demands.

FAQs

What Is Medical Device Injection Molding?

Medical device injection molding uses extremely precise medical-grade plastics and injects them into molds to produce complex, biocompatible components for medical devices.