Did you know that injection molding is transforming the medical device industry? This advanced manufacturing process enables the production of high-quality, precise, and cost-effective medical components.
What Is Injection Molding for Medical Devices?
Injection molding for medical devices involves heating medical-grade plastics until they melt, then shaping them into precise forms using specialized molds. This technique produces durable, high-performance equipment with smooth finishes and exact measurements.
With advancements in additive manufacturing, medical professionals now have access to high-quality molded parts that meet stringent industry standards. Whether it’s intricate surgical instruments or complex implantable devices, injection molding ensures the flawless fabrication of essential components for optimal performance.
This process is widely used to manufacture various medical parts, including:
- Knee and hip joint replacements
- Surgical implants and instruments
- Blood bags
- Syringes
- Catheters
- Petri dishes
- Healers
- Test tubes
Injection molding continues to play a vital role in medical manufacturing, delivering reliable and consistent components for healthcare applications.
Types of Injection Molding for Medical Devices
Various injection molding techniques are used in medical device manufacturing to ensure precision, durability, and compliance with industry standards. Below are some of the most common methods:
Plastic Injection Molding
Plastic injection molding involves heating plastic polymers to high temperatures and shaping them into sterile, contaminant-free medical devices. Using aluminum or steel molds, manufacturers can create highly precise, customized components that meet strict hygiene and safety standards.
Insert Molding
Insert molding is a single-step process in which a secondary component is molded over an existing insert. Unlike overmolding, this method integrates different materials—such as plastics, metals, or alloys—into a single structure, improving strength and functionality while reducing assembly time.
Overmolding
Overmolding, also known as two-shot molding, involves molding one or more layers over an existing structure to enhance grip, durability, and ergonomic design. Though it has a longer production cycle, overmolding is ideal for creating medical devices with enhanced comfort and usability, such as surgical tool handles.
Liquid Silicone Injection Molding
Liquid silicone injection molding involves heating silicone into a liquid state before molding it into medical components. This method is highly versatile and biocompatible, making it ideal for medical applications. However, silicone molds are generally less durable than aluminum or steel, making this technique best suited for prototyping and low-volume production.
Each injection molding technique offers unique advantages, allowing manufacturers to develop high-quality medical devices that meet the demands of modern healthcare.
Types of Medical-Grade Plastics Used in Injection Molding
Medical device manufacturing relies on specialized plastics that offer durability, biocompatibility, and resistance to environmental factors. Here are some of the most commonly used medical-grade plastics in injection molding:
Poly ether ether ketone (PEEK)
PEEK is a high-performance thermoplastic known for its exceptional resistance to radiation, high temperatures, chemicals, and wear. It offers outstanding dimensional stability even under stress, making it ideal for medical and surgical implants.
Polyethylene (PE)
Polyethylene is a strong and versatile plastic composed of thousands of ethylene polymers, providing excellent tensile strength and rigidity. Highly compatible with biological tissues and resistant to sterilization processes, PE is widely used for joint prostheses, tubing, connectors, and pharmaceutical containers.
Polycarbonate (PC)
Polycarbonate is a transparent, tough, and flexible plastic with excellent mechanical properties. It is highly resistant to abrasion, impact, and temperature fluctuations. Due to its biocompatibility, polycarbonate is commonly used in medical equipment such as clear masks, protective gear, and oxygenators.
Polypropylene (PP)
Polypropylene is a durable plastic known for its resistance to cracking, radiation, impact, and temperature variations. Its strength and versatility make it a preferred choice for medical components such as syringes, connectors, and knee and hip replacements.
Silicone
Silicone is a chemically inert, rubber-like polymer valued for its exceptional flexibility and biocompatibility. It is commonly used in the production of catheters, tubing, and connectors due to its ability to withstand extreme conditions while maintaining its integrity.
Polystyrene (PS)
Polystyrene is a rigid, high-quality engineering plastic with excellent dimensional stability. While less flexible than other plastics, it is ideal for manufacturing medical components such as petri dishes, culture trays, and diagnostic equipment.
Each of these medical-grade plastics plays a crucial role in developing safe, reliable, and high-performing medical devices, ensuring precision and quality in healthcare applications.
The Benefits of Injection Molding for Medical Devices
Injection molding is a highly efficient manufacturing process that ensures precision, consistency, and compliance in the production of medical devices. Here are some of its key advantages:
Compliance With Industry Standards
Medical injection molding adheres to strict regulatory requirements set by organizations like the FDA, ensuring that all components meet the highest safety and quality standards.
Cost-Effectiveness
As an automated process, injection molding significantly reduces labor costs while enhancing efficiency. With computer-controlled precision, each part is manufactured with minimal material waste, resulting in lower costs per unit.
High Precision and Accuracy
Medical devices require exact specifications, and injection molding delivers exceptional dimensional accuracy with tight tolerances. This minimizes deviations, ensuring patient safety and optimal device performance.
High-Volume Reproducibility
For medical products like syringes, gloves, and masks, consistency in mass production is essential. Injection molding enables manufacturers to produce thousands of identical, high-quality parts with minimal maintenance and downtime.
Reliable and Scalable Manufacturing Solutions
Looking for high-quality, precise injection molding solutions for your medical devices? Ace Mold specializes in contract manufacturing services that deliver consistent, large-scale production.
Our advanced injection molding technology ensures precision, efficiency, and scalability to meet your needs. Whether you require small or high-volume production, we guarantee consistent quality at every stage.
Specialized Injection Molding Techniques for Medical Devices
Medical device manufacturing requires precise, efficient, and cost-effective production methods. Two advanced injection molding techniques—thin wall injection molding and gas-assisted injection molding—offer unique advantages for creating high-quality medical components.
Thin Wall Injection Molding
Thin wall injection molding is designed for producing lightweight, high-precision parts with minimal material usage and faster cycle times. This technique is ideal for small, complex medical components where precision is critical.
- Wall Thickness Considerations: Typically, parts with walls thinner than 1mm fall under thin-wall molding. However, the minimum thickness depends on the size and structural integrity of the part.
- Applications: Used in high-volume production, thin wall molding is perfect for creating small enclosures for medical devices, ensuring durability without excessive material consumption.
- Prototyping & Low-Volume Production: Manufacturers like Fictiv provide cost-effective steel molds for prototyping and small production runs, offering an alternative to 3D printing for functional medical samples that match high-volume production materials.
Gas-Assisted Injection Molding
Gas-assisted injection molding is a low-pressure process that injects pressurized nitrogen or carbon dioxide gas into molten plastic, pushing it into the mold’s extremities and forming hollow sections with thicker walls.
- Key Benefits:
- Reduces plastic usage while maintaining structural integrity
- Minimizes cycle times, leading to lower production costs
- Enhances part quality by reducing sink marks, warpage, and surface defects
- Decreases residual stress on molded parts, prolonging mold lifespan
- Applications: This method is ideal for medical device casings, ergonomic handles, and components with large surface areas that require superior textures and precise detailing.
Both thin wall injection molding and gas-assisted injection molding provide cost-effective, high-precision solutions for medical device manufacturing, ensuring efficiency, durability, and compliance with industry standards.
Advanced Injection Molding Techniques: Over molding & LSR Injection Molding
Injection molding technology continues to advance, providing innovative solutions for manufacturing high-quality medical devices. Over molding and LSR injection molding are two key processes that enhance performance, durability, and efficiency in medical applications.
Overmolding
Overmolding is a specialized injection molding technique where a polymer is molded over a substrate, eliminating the need for post-molding assembly. This process is widely used for medical products, including:
- Surgical instrument handles
- Soft-touch medical device grips
- Silicone or thermoplastic elastomers (TPE) overmolded onto thermoplastic substrates
How Overmolding Works
Overmolding is more than just layering materials—it involves the formation of chemical and mechanical bonds:
- Chemical Bonds: Form at the molecular level based on how well the overmold material wets the substrate.
- Mechanical Bonds: Depend on the physical interface between the substrate and the overmold material.
Types of Overmolding Techniques
- Two-Shot Molding (Double-Shot Molding) – A continuous two-step process where a substrate is molded first, then overmolded with a different material.
- Pick-and-Place Molding – Used mainly for prototyping and low-volume production, where the substrate is manually positioned in a mold before overmolding.
LSR Injection Molding (Liquid Silicone Rubber Molding)
LSR injection molding is a process used for liquid silicone rubber (LSR), a two-component elastomer that requires curing to develop its final properties.
How LSR Injection Molding Works
- Material Preparation: LSR components come in 5-gallon pails or 55-gallon drums and are mixed in a static mixer.
- Injection & Mixing: The material is further mixed inside the injection unit before being injected into the mold.
- Curing Process:
- The mold remains clamped while the silicone cures—typically 30 seconds for LSR.
- In contrast, high-consistency rubber (HCR) requires longer cure times (5+ minutes).
Platinum-Cured LSR for Medical Applications
- Platinum-cured LSRs offer higher optical clarity, tensile strength, and tear resistance.
- They contain fewer extractables (compounds that can leach out), making them ideal for medical-grade applications.
- Used in high-volume medical products, such as spacers for asthma inhalers.
HCR Injection Molding & Metal Injection Molding in Medical Manufacturing
Injection molding is essential for medical device production, enabling high-precision, durable components. Two advanced techniques—HCR injection molding and metal injection molding (MIM)—are widely used for manufacturing complex medical parts with excellent mechanical properties.
HCR Injection Molding
HCR injection molding is used with high-consistency silicone rubber (HCR), also known as heat-cured silicone rubber. This process involves heating a gum-like raw material and injecting it into a mold under high pressure. The injection screw preheats the rubber to reduce its viscosity, allowing the silicone to fill the mold cavity completely. The preheating step at the beginning of the molding cycle helps speed up the process.
HCR has a higher viscosity than liquid silicone rubber (LSR), making it more challenging to process. The injection molding process for HCR is generally more complex, but it can achieve better overall properties than LSR. However, high shear conditions in the mold can cause shrinkage rates to vary, making proper tool design and an experienced manufacturing partner crucial.
Common applications for HCR injection molding in the medical industry include gaskets and O-rings used in medical devices.
Metal Injection Molding
Metal injection molding (MIM) combines powdered metal with a thermoplastic binder, which is heated so that the metal grains bond with the thermoplastic. The material is then injected into a mold to create the desired part. Once the part is formed, the thermoplastic binder is removed, and the part undergoes sintering, a heat treatment process that compacts loose material, resulting in a net-shape or near-net-shape final product. Some parts may require post-sintering operations for additional finishing.
MIM is ideal for high-volume production of medical parts with complex shapes and varying sizes. It offers superior strength and an excellent surface finish while providing a cost-effective alternative to CNC machining. This process is particularly useful for manufacturing parts made of difficult-to-machine metals such as stainless steel, cobalt-chromium alloys, and titanium alloys. The dimensions and end-use properties of MIM parts are comparable to those of wrought and cast materials.
Common applications for MIM in the medical industry include surgical instruments and implants, both of which often use stainless steel.
Complex Medical Parts at High Speeds
For medical injection molding projects, whether for prototyping, low-volume, or high-volume production, a well-planned approach and an experienced manufacturing partner are essential. Inadequate drying or improper processing methods can lead to unnecessary costs and risks.
Fictiv offers a global manufacturing network and industry experts to help produce high-quality medical injection molded parts, no matter how complex the design. From part design to prototyping and full-scale production, having the right expertise ensures efficiency and precision throughout the manufacturing process.
