March 13, 2024

Plastic Injection Molding vs. Alternative Manufacturing Techniques in Medical Device Production

A line of plastic tipped medicine bottles in a production factory.

The medical device industry relies on various manufacturing techniques to produce the vast array of products needed for patient treatment and care. From high-tech diagnostic equipment to single-use disposable devices, choosing the right manufacturing process is crucial to achieving quality, efficiency, and cost targets.

Plastic injection molding has traditionally been the dominant manufacturing technique for medical device production. This versatile process uses mold cavities to form plastic components with the right material properties, geometries, and tolerances needed for function and assembly. However, alternative manufacturing methods are emerging to complement and, in some cases, displace injection molding.

Techniques such as 3D printing, CNC machining, and thermoforming now allow for faster prototyping, highly customized devices, and innovative combinations of materials. The choices offer tradeoffs across factors like per-unit economics, turnaround time, part complexity, and performance attributes.

As medical technologies continue advancing, manufacturers need to continually evaluate the optimal balance between proven high-volume plastic molding methods and newer emerging processes. This article provides a comparative assessment of plastic injection molding versus key alternative techniques for medical device production.

Plastic Injection Molding in Medical Device Production

Plastic injection molding is a manufacturing process that uses molded cavities to produce plastic components with consistent and repeatable properties. The process involves high-pressure injection of molten plastic material into these tooling cavities, allowing the plastic to conform and harden into the desired shapes.

This technique provides several key advantages for high-volume medical device production:

Consistency and Repeatability

Injection molding can reliably produce defect-free parts within tight tolerance specifications from one part to the thousands. This ensures consistency and safety in medical applications.

Ability to Produce Complex Geometries

Intricate and complex plastic-based medical components with hollow or textured aspects can be designed and injection molded. These include catheter tips, surgical screws, joint replacement parts, wearables, and drug delivery devices.

High-Volume Production Efficiency

For large production runs in excess of thousands of units, injection molding provides faster cycle times and efficient material use. This makes it cost-effective for mass-manufactured medical supplies and components.

Cost-Effectiveness for Large Runs

Though the initial tooling investment is high, individual part costs for injection molding are very low at high volumes. Per unit savings are substantial for established medical products with steady long-term demand.

Limitations To Consider

Initial Setup and Tooling Costs

Creating an injection mold cavity and establishing the production line requires extensive upfront investment. This can deter the adoption of newer medical innovations with uncertain demand.

Material Limitations for Certain Applications

Not all medical-grade plastics are suited for injection molding, constraining options for components that interface with internal tissues or fluids.

Environmental Considerations of Plastic Use

As awareness grows around sustainability, medical manufacturers must consider the environmental impact of scaled plastic injection molding and potentially supplement processes.

3D Printing (Additive Manufacturing)

3D printing, also known as additive manufacturing, is a technology that produces three-dimensional components from digital models by depositing successive layers of materials like metals, plastics, or even living cells. This enables on-demand production without dedicated molds and tooling.

In medical device production, 3D printing shows immense promise to improve treatment planning device customization and reduce waste:

Customization and Complexity without Additional Cost

Any required shape or size modifications can be easily accommodated by tweaking the base digital files used for printing. This also enables otherwise impossible geometries.

Reduced Waste and Potentially Lower Environmental Impact

As an additive process, 3D printing uses the minimal amount of material required for the component, eliminating molding byproducts or machining scrap waste.

Rapid Prototyping and Design Flexibility

Ideas can be quickly iterated by researchers and engineers using 3D-printed models for evaluation. Adjustments can be faster than remolding in injection processes.

Limitations To Consider

Lower Speed in Volume Production

Printing times restrict output volumes, with typical production runs in the tens or hundreds of units. This limits applications for high-demand or disposable items.

Material and Strength Limitations for Some Applications

The range of medical-grade printable materials is expanding but still constrained, especially for high-precision implants and interfaces. Material integrity may also require post-processing.

3D printing opens doors for healthcare innovation but may need to be selectively deployed based on product characteristics and demand patterns.

CNC Machining

CNC (computer numerical control) machining is a subtractive manufacturing process that uses pre-programmed computer software to control machinery and tools to shape metal, plastic, or composite components by precision removal of material.

For medical applications, CNC machining is used to manufacture custom patient-specific implants, prosthetics, surgical tools and high-accuracy components:

Precision and Repeatability

CNC machined parts meet strict dimensional and geometric tolerances thanks to accurate automated computer control of cutting tools. This ensures consistency.

Wide Range of Material Options

CNC systems can shape various biocompatible materials, from titanium alloys and polymers to ceramics, with the right tooling.

No Need for Specific Tooling

Part programming is flexible enough to accommodate changes without requiring physical tooling alterations, enabling easy adjustments.

Limitations To Consider

Higher Cost for Large Volumes

Though ideal for small batch quantities, CNC machining involves slower cycle times and higher tooling/labor costs, making it less suited for mass production.

Material Waste

Machining away excess material to form a part inherently leads to waste. For costly implant-grade alloys, this inefficiency and environmental impact add up.

With programming flexibility and precision, CNC machining serves as an alternative manufacturing approach for medical components where quality needs to supersede volume-driven cost efficiencies during production.


Thermoforming is a manufacturing process where a plastic sheet is heated until soft and pliable, then molded into shapes using a cavity die or pressure. Medical device applications range from hospital bed parts to sterilization trays and protective face shields.

Lower Tooling Costs than Injection Molding

Simple single-sided thermoforming only requires a male or female die mold rather than matched cavity tooling, substantially reducing initial setup costs.

Good for Large Parts

Forming flat plastic sheets allows larger sizes than injection molding nozzles can accommodate, which is ideal for things like body immobilization devices.

Limitations To Consider

Less Precision for Intricate Details

Due to the thickness and heating constraints, thermoformed components generally lack fine details and tolerances achievable with injection molding or CNC machining. Mostly suited for simple geometries.

Material Thickness Variability

Stretching of the heated material can result in uneven part thickness in different locations–a drawback for high-precision sizing and fitting.

As a cost-effective means for rapidly shaping flat plastic sheets, thermoforming balances economy with speed in medical contexts where ergonomics and fit may be a greater priority over tiny tolerances. Processes are also amenable to small batch or field production much closer to end-use points.

Blow Molding

Blow molding is a plastics manufacturing method where hot polymer material is extruded into a mold cavity and then inflated under pressure–either compressed air or mechanical stretching is used to push the material out to conform to the interior walls of the cavity.

The process is suited for hollow components and sees use in medical products like saline bottles:

Ideal for Hollow Parts, such as Bottles

Blow molding efficiently produces enclosed voids within an all-plastic enclosure using presses or automated machinery. This helps make sterile fluid containers and body collection bags.

Limitations To Consider

Limited to Simpler Geometries

Given parts form inflated cavities, excessively intricate product details are not easily possible. Mostly used for basic round shapes rather than precision components.

Not Suitable for all Medical Device Applications

Due to geometric and strength constraints, blow-molded applications in medicine are selective and tend to be limited to fluid storage and transfer rather than direct interfacing devices.

Offering efficient forming of hollow enclosures, blow molding serves specialty uses where intravenous fluids, body fluids, or gasses need containment and delivery in sterile medical systems, though it lacks versatility for more complex equipment.

Comparison and Selection Criteria

Determining the right manufacturing technique entails a close analysis of multiple factors:

Product Complexity and Design

Components with intricate geometries, precision fittings, or specialized multi-material integration favor injection molding or machining, while basic shapes suit thermoforming or blow molding.

Volume and Production Speed

When dealing with staple disposable supplies or routine diagnostic equipment needing 10,000+ units per year, injection molding provides the most automation and speed. Additive methods are far slower.

Material Requirements

Strict purity, grade, and consistency demands of implants and internal interfaces currently limit material options for techniques like 3D printing. Machining offers the widest choice.

Cost Considerations

For recovering high equipment and mold expenses, long, steady part volumes amortize injection molding setups the best. For limited runs, additive and machining methods compete on costs.

Regulatory and Quality Compliance

Stringent medical device protocols govern aspects like biocompatibility testing, sterilization, packaging, and more, irrespective of production technique. However, some methods, like 3D printing, currently lack clarity around regulations.

Based on the application area, cost targets, market demand visibility, and compliance needs, medical project teams have to balance the advantages and tradeoffs presented by both conventional manufacturing, like injection molding, as well as newer methods, like 3D printing and advanced CNC machining. An application-specific analysis is key to optimizing for efficiency.

Finding the Right Process for Your Medical Devices

Determining the most suitable production technique for your medical products can be complex–whether you seek quality, cost efficiency, or innovative capabilities. Striking the right balance requires experience and expertise.

MOS Plastics offers over 50 years of experience helping medical device companies identify and implement the ideal manufacturing methods for their needs. With a comprehensive focus on healthcare, we provide turnkey injection molding and assembly for medical devices and diagnostic equipment. Our investments in cutting-edge machinery, clean rooms, and quality processes allow compliance and innovation side-by-side.

We mold a diverse range of high-precision medical components in engineering-grade resins while ensuring dimensional accuracy, stability, and healthcare compliance at every step. Our partnerships with major players in wound care, drug delivery, instruments, and testing are a testament to our capabilities.

Reach out today to explore how our capabilities can make your next medical innovation a success.