Advanced molding methods are vital for the production of complex, medical device components made from high-performance materials, which provide exceptional strength and biocompatibility. Injection molding technologies are evolving to include multi-cavity molds, advanced automation, and in-process quality controls for high-volume production to provide consistent high-quality parts. Overall, these innovative design and manufacturing processes enable medical device manufacturers (MDMs) to make increasingly complex medical devices that meet unique or unmet healthcare needs—for example, smaller devices for less invasive surgeries or at-home, self-monitoring devices that rely on sensors and real-time data collection to provide continuous care.

“In particular, miniaturization trends in the industry present new challenges for mold design and production, which require precision injection molding to achieve accuracy and complexity,” said Josh Nobis, program manager at Plastic Design Company, a Scottsdale, Ariz.-based specialty manufacturing company focused on precision micro injection molding and value-added assembly for the medical device and life science industries.

Miniaturization of molded components and assemblies continues to advance at a rapid pace, enabled by Industry 4.0 technologies. “For example,” said Brent Hahn, vice president of business development and strategy for Isometric Micro Molding, a New Richmond, Wis.-based vertically integrated micro molding and automated assembly company serving high precision market segments in medical device and drug delivery, “we can produce parts six inches and smaller with micro features, thin walls with long aspect ratios in challenging resins, and tighter tolerances of the molded parts and assemblies.”

As the world continues to rebound from COVID-19, demand for new medical devices is on the rise as more people are following through with elective surgeries and other healthcare procedures. Making these products using injection-molded plastics is still one of the most cost-effective manufacturing methods for producing medical device components in high volume. Even though additive manufacturing (AM) technology continues to improve rapidly and will have a key role in future manufacturing of lower-volume medical devices for unique applications, “injection molding will still be the preferred method for volume manufacturing,” said David Stephens, principal technology engineer for Health Solutions at Flex, a global contract manufacturer whose services include providing complex injection molding and mold fabrication services to the medical device industry. “To manufacture geometrically complex component parts in hundreds of millions or billions per year, no other manufacturing method has yet surfaced that is a significant challenger to injection molding.”

The molding market is currently very dynamic with multiple trends driving growth and the need for advanced or innovative approaches. “From product growth areas such as single-use devices and wearables to geographic trends such as reshoring, we’re seeing increased demand for molding, especially complex molding—smaller and more intricate parts, made from challenging materials—and always with the focus on speed and quality,” said Tobe Allenbrand, global vice president of operations for GlobalMed/MDI, a Tempe, Ariz.-based provider of specialized engineering and manufacturing services including injection, blow, and dip molding; extrusion; coatings; and assembly.

Along with the intricate tooling and precision molding demands by MDMs, metrology requirements must also keep pace—”it does not matter if you can mold and measure the part or assembly, you must be able to validate it,” said Hahn.

There are still supply chain issues that impact the speed of medical device innovation and manufacturing, but MDMs have found ways to cope with the frustrating shortages.

“As COVID-19 has taught the world,” said Donna Bibber, CEO for Isometric Micro Molding, “having multiple suppliers in multiple locations mitigates business continuity risks. Medical device OEMs are adding niche suppliers to their approved vendor lists, such as micro molders with miniaturized device capabilities; this is not only necessary, but critical to success. It is important to partner with suppliers that are culturally working in micron tolerances to lessen program risks.”

In addition, noted Cory Heckman, injection molding engineering manager for Raumedic, a Mills River, N.C.-based developer and producer of polymer-based and silicone-based solutions for customer-specific medical and pharmaceutical applications, “the pandemic has driven a lot of nearshoring and onshoring activity. Increasingly, manufacturers want their suppliers to stay local because they can see what something like a pandemic can do to their supply chains.”

Latest Trends

Current trends that challenge the technical limits of medical molding include miniaturization, connectivity in devices for remote/at-home monitoring, and customization for specific patient and/or treatment needs. The development and progression of advanced, precisely engineered materials are often needed to achieve specific performance requirements and tighter product tolerances. It is not uncommon for large MDMs to have multiple contractors handling various parts of a single device. However, increasingly, MDMs also appreciate vertically integrated suppliers that offer an expanded range of capabilities, making it easier to manage the supply chain and track progress.

The latest molding trends are focused on improving efficiency and reducing lead times through the use of advanced manufacturing methods such as multi-cavity molds. “There is also growing emphasis on using advanced materials such as polyether block amide [PEBA], polyether ether ketone [PEEK], and cyclic olefin copolymer [COP] for improved functionality and durability, enabling the production of high-performance molded parts,” said Nobis. In addition, the ability to produce increasingly smaller dimensions enables the production of miniaturized components that have opened up new possibilities in interventional medicine and other fields.

The growing disposables market is also driving molders to produce larger volumes, resulting in the need for further automation, in-line assembly at the injection molding press, and higher volume cavitation, “resulting in more cost-effective production,” said Charles Klann, director of engineering for Saint-Gobain, a Portage, Wis.-based silicone-molded manufacturer of medical components.

Wearables, robotic-assisted procedures, and single-use applications are product groups that could benefit from converting metal parts to plastic because they are more lightweight and reduce vibration. “These types of parts often require more highly engineered materials, which in turn, requires using advanced simulation data,” said Allenbrand. “Just as important is the know-how to actually understand what the data is saying and then adjust the tool and part design to be reproducible at scale.”

What OEMs Want

OEMs want the highest levels of performance and quality for their products. They seek contract manufacturers (CMs) that have automated facilities, cleanrooms, extensive knowledge about complex materials, and in-house tooling and design to speed along project timelines.

“They are also interested in risk mitigation strategies such as supply chain and disaster recovery plans, evidence of sustainability programs, technical skills including design for manufacture and assembly, tool design and manufacturing services, program management validation services, and material compliance,” said Kelly Stichter, senior vice president and general manager for Velosity, the Minn.-based parent company for Teamvantage, a full-service contract manufacturer that provides custom contract manufacturing, injection molding, precision machining, and tooling.

Sometimes MDMs approach their molders with just an idea and count on them to share their knowledge and expertise throughout the entire process, from concept through design, development, prototyping, manufacturing, validation, and shipping. “There is increased need to support the translation of a design or product idea to manufacturing,” said Ray Scherer, global engineering manager for GlobalMed/MDI. “It is a bit of a catch-22 with the tools available now. You can design almost anything, but that does not mean you can manufacture it reliably—at volume and a viable cost. As we continue to push the envelope on part size, complexity, and performance requirements, this becomes increasingly true.”

MDMs want their CMs to be skilled and knowledgeable partners rather than just a supplier. MDMs seek vertically integrated molders that offer other key services, such as assembly, packaging, kitting, and drop-shipping to multiple and global locations—which of course, accelerates time to market. MDMs also look for CMs that work in other industries, such as aerospace or electronics, that can bring inspiration and high-tech approaches or innovations from these industries to the design for manufacturing (DfM) phase of their medical designs.

“The advantage of a company like Flex is that we manufacture for most of the other major markets including consumer, industrial, automotive, and cloud,” said Stephens. “We enable customers to improve lead times through our learnings across other markets, while still maintaining the rigor required for the medical market. For example, we used our 5G expertise to help a client innovate its next-generation wearable medical device and our optics experience to help a catheter provider address technology challenges working with fiber optics.”

Ultimately, OEMs are looking for molding suppliers that can go beyond “the ‘shoot and ship’ models of the past,” said Richard Ford, vice president of business development for RenyMed, a Baldwin Park, Calif.-based, 100% medical custom injection molder, with on-site, integrated tool making. “For new product development and new tooling projects, medical molders need to be involved from the earliest DfM and functional testing of the product. OEMs are looking for molders who can collaborate with all functions of their team to reduce risk and maintain sustainability.”

Bibber agreed.

“DfM and DfA [design for assembly], especially for high-precision molding, are services that OEMs value,” said Bibber. “Where there are multiple parts to an assembly, and millions annually—for example, 16 cavities of one part, 32 of another, 64 of another, and two purchased parts, along with the Design of Experiments inputs—all have to roll up to a full-factorial tolerance that is still capable of 1.33 Cpk or better. The high skill, and proof of familiarity with tolerances, material grades, and size of parts, all help mitigate risks. A scope of work and risk-mitigation strategy is of value to the OEM, even at the quoting stage, so there are no surprises as the project unfolds later on, when the risks and costs are higher.”

Sustainable/recyclable plastic resins, packaging, and energy conservation are now key topics in MDM strategic planning sessions. Not only are these practices better for the environment, they also resonate with consumers and strengthen brand awareness and market share. There should be no more “mold and dispose”—instead, the focus should be on how to reduce waste (energy, materials, packaging) and reuse and recycle the molding materials that are used. “In the past 24 months, we have seen a significant uptick in requests to help our customers find more sustainable/recyclable plastic resins,” said Stephens. “We meet with our major plastic resin suppliers regularly to determine what they are developing and to recommend sustainable resin options to our customers so they can incorporate those resins into their device designs.”

How Small Is Small?

Precision injection molding is critical for achieving the necessary levels of accuracy and complexity required by the growing demand for miniaturized components, especially in the interventional catheter and orthopedic markets. “Examples include bone anchors and screws with outside diameters as small as 500 microns and tolerances in the 25-micron range, as well as molded assemblies with complex geometries and varying wall thicknesses,” said Nobis.

The smallest parts that Isometric Micro Molding makes “are so small that over 1,000 parts can be made from a single plastic pellet of resin,” said Bibber.” What is amazing is the size and thickness of the molded parts—for example, Isometric Micro Molding can mold 0.0001-inch [3 microns] channels in microfluidic diagnostic chips or 0.001-inch [25 microns]-thick cannulas, sheaths, and catheter tips with extremely high aspect ratios. These features and tolerances are enabling many new robotic surgery applications, continuous glucose monitoring, insulin delivery, diagnostics, and other miniaturized devices.

“It all begins with an understanding of the customer’s needs,” added Klann. “We will provide a recommendation based on customer specifications. For liquid silicone rubber [LSR] materials, we can create parts as small as 0.001 g with tolerances as low as 0.001 inches. We also make holes as small as 0.003 inches and wall sections as thin as 0.0015 inches.”

New Tools and Technologies

New molding machinery is getting more compact (some machines are small enough to sit on top of a desk). However, despite the impressive dimensions and tolerances injection molding can achieve today, there are still tooling and material challenges. “Material choices can be limited based on the performance requirements—for example, fillers such as metal, glass, fibers, and antimicrobial agents, along with specific degradation rate and melt flow index, can all influence performance and sometimes limit selection options,” noted Stephens. “With plastic molding, there will always be limits on dimensions/tolerance due to plastic resin type. Different type plastic resins have different melt flow and shrinkage properties, which impact the ability to meet the dimensional and tolerance requirements of the molded part.”

“However,” said Ford, “using scientific molding and DOE [design of experiments] process development, material type/shrinkage can be understood and controlled.”

Continued advances in 3D printing have been instrumental in enabling improvements in injection molding. This is especially true in rapid prototyping of part designs to enable initial functional design evaluation, as well as production of 3D-printed mold cavities to accelerate the evaluation of part designs in the actual representative material that will be used in commercial production. “The technological advances in this area continue to be driven by applications that require smaller, tighter-tolerance part designs and the continued pressure to reduce timelines and retire risk earlier in the development process,” said Nobis.

Another area of significant technological advancement is process control. Typically, this involves the integration of pressure transducers and sensors into the injection mold and associated injection molding machine. “It is apparent that advances in artificial intelligence and machine learning will be key enabling technologies to drive improvement in scientific injection molding through closed feedback loop optimization,” said Nobis.

Computer-controlled machines are constantly updating and expanding or creating new capabilities. Molding machines are making major advancements in programming, “giving the user full control to write custom machine sequences to accommodate some of the most sophisticated tooling designs,” said Heckman. “Machines can be programmed now to monitor their process outputs and can self-compensate during production for some of the tasks that previously required visual inspection and manual adjustment.”

Since 2014, Isometric Micro Molding has used CT scanning technology for in-process and final release inspection. This technology enables fast and accurate process window development using color deviation plots that, within 15 minutes, provide a full first article inspection, including which process variables have the most influence over critical to quality attributes. Isometric Micro Molding uses a Werth CT scanner for sub-micron accuracy, the ability to see through the parts to detect bubbles and inclusions, and quick scanning of all parts in a multi-cavity shot at the same time.

Isometric Micro Molding’s high-resolution micro 3D printers support customers in their early design phases and allow for the evaluation of multiple design options at the same time, including printed medical-grade photopolymers. Ultra-fine resolution 3D printing of parts and mold inserts for molding parts in the intended thermoplastic can be received in about one week. For example, Isometric Micro Molding can 3D print parts with the largest part dimension being only 25 microns having 2-micron feature sizes, or 3D print mold inserts of different part designs in a matter of days. These capabilities help customers with DfM/DfA early in the development phase so scalability can be reviewed, even at the prototype stage.

Adding micro surface finishes that incorporate biomimicry of hydrophobic and hydrophilic surfaces are additional advancements in surface functionality that can be incorporated into micro molding solutions. “For example, lasers can now be used for surface modifications on mold steel, which allows us to provide custom surface finishes,” said Klann. “Closed-loop molding capabilities for LSR utilize pressure transducers, which give us even a greater control for a more consistent process.”

Material Advances

As part of the sustainability trend, molders are trying to move away from carbon resources and develop environmentally friendly materials from plant-based resources and biodegradable polymers. “Introducing antibacterial materials to components, like connectors in IV sets, is another trend,” said Heckman. “When fluid flows through the connector, for example, the antibacterial component can help prevent infections that can be caused by bacteria/pathogens that are sometimes found in the connectors or other sources prior to patient administration.”

New tool steels are also being created that are better suited for molding, whether it is hardness, durability, or thermal transfer, which is one of the biggest drivers of cycle time. “Many geometries of parts make that very difficult to do within the traditional tool design, but there have been so many advancements in different types of steel and technologies that can transfer heat out quickly that it is not much of an issue anymore,” said Heckman.

Material formulations continue to evolve to meet ever-changing customer design and product specifications. Additives optimize performance and/or provide the ability to incorporate certain features, such as laser-etched graphics, at very low cost. Materials used for permanent implants (permanent or bioresorbable) can be molded to provide innovative complex parts. Plastic resins, too, can be engineered to include a growing number of additives. For example, copper-filled or tungsten-filled plastics are new materials that have two distinct advantages: 1) they add molecular weight to a part and 2) they provide heat conductivity. “They mold like plastic so you can create features that are typically too expensive for metal,” said Scherer. “For example, you can create a poka-yoke feature or mechanical engagement directly in the part. It also has enough metal load that you can electroplate it, which is often a desired cosmetic feature.”

Newly developed polymer formulations continue to enter the market with ISO 10993 ratings and the melt flow properties needed to fill ultra-thin and high aspect ratio injection-molded components. Materials such as Pebax and Arnitel nylon copolymers have strong tensile and other physical properties, even down to 25-micron thicknesses. “With smaller spaces in catheters, endoscopes, and robotic surgery instruments, these materials are key drivers to successful miniaturized device sizes and strength,” said Hahn. “Other commonly used micro molding polymers are PEEK, polycarbonate, polysulfone, polyurethane, bioresorbables, and liquid crystalline polymers.”

Moving Forward

MDMs sometimes do not fully understand all new product introductions require a long runway before the product actually makes it to the market. They often request unrealistic timelines that do not allow enough time for unforeseen delays, engineering changes, or changing capacities. “When an original schedule starts experiencing delays—which it almost always does—some companies will throw money at the problem to try and maintain schedules,” said Ford. “They do not realize that tool building, process development, and especially validations take weeks or months, no matter how much money is spent.”

Stichter is excited by the potential to further integrate and utilize AM technologies and molding to reduce lead times and to provide customized solutions that will be needed as additional medical applications are developed to address specific patient needs. In addition, as materials and process refinements continue to evolve in the additive space, there will be additional opportunities to integrate multiple technologies such as additive, molding, and assembly to “provide solutions that are not currently available to the market,” she said. “Integration of electronics into very small, molded products for connectivity, remote monitoring, and diagnostic applications are also areas where molding will continue to advance to deliver solutions that achieve customer and market needs.”

Heckman agreed.

“The sky is the limit,” he said. “I have never seen technologies advance as quickly as they are now.” 

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Mark Crawford is a full-time freelance business and marketing/communications writer based in Corrales, N.M. His clients range from startups to global manufacturing leaders. He has written for MPO and ODT magazines for more than 15 years and is the author of five books.