Mark Crawford, Contributing Writer06.04.18
Medical injection molding and toolmaking are exceptionally strong in the medical device industry—both for new product development and legacy products. Molding equipment manufacturers continue to improve control systems, enabling even tighter tolerances and better surface finishes. Molders are getting better at making difficult part geometry, such as thin walls, undercuts, overhangs, and parting line restrictions. A greater variety of advanced materials is available for molding, including bioabsorbables. Medical device manufacturers (MDMs) are designing more products that require processes such as overmolding/insert molding to combine materials (plastic, metal, rubber, or thin flexible circuit electrodes) to create unique physical characteristics or specific surfaces or textures. Depending on the project, metal injecting molding can be competitive with additive manufacturing and 3D printing, especially for prototypes.
Medical device designs continue to evolve, with innovative new molded products entering the market more rapidly than ever before. “Focus continues to be on patient care and comfort, minimally invasive procedures, out-patient procedures, and treatment options that have only recently been envisioned,” said Jared Sunday, technical sales manager at RAUMEDIC, a Mills River, N.C.-based provider of extrusion, injection molding, and assembly services to the medical device industry. These products include image-guided treatments, rapid and accurate diagnostic procedures, laser-based surgical tools, micro implants, and bioabsorbable connections.
Making smaller and more complex medical devices requires more experience and precision from molders, including a deep knowledge of material behavior, especially for advanced materials. As a result, MDMs often want to work with molders that are dedicated to only making medical products. They are sometimes reluctant to partner with molders who may not have the same depth of skill and knowledge as a medical molder. In addition, MDMs expect their molder to be a steady partner and advisor through all phases of design and production.
“I get asked all the time, what percent of your business is medical?” said Randy Ahlm, CEO of NPI Medical, an Ansonia, Conn.-based provider of tooling and injection molding services to the medical device industry, with a special emphasis on prototyping. “I never used to get asked that question, but now nearly every customer wants to know. OEMs seek suppliers that can help them drive out supply chain costs and consolidate their supply base. We helped one customer consolidate from six suppliers to one, because we were able to bring multiple capabilities into play. If we were just a molder, there is no way we would have been awarded that business.”
Currently, the medical molding market is experiencing considerable consolidation with almost constant acquisitions and mergers. “In addition to M&As, the market is seeing considerable vertical integration—plastics companies buying metal companies, plastics companies buying other plastic commodities such as extrusion, plastics companies buying small contract manufacturing firms, etc.,” said Timothy Reis, vice president of healthcare business development at GW Plastics, a Bethel, Vt.-based provider of contract manufacturing, injection molding, and precision tooling.
As companies continue to acquire/merge, “it will be interesting to see how things shake out for all suppliers, not just molders,” said Dan Snyder, sales manager for Plastikos, an Erie, Pa.-based manufacturer of precision plastic components for medical devices. “We’ve seen it play both in our favor and quite the opposite, depending on the specific merger/acquisition.”
More new players are also coming into the field. Highly skilled molders and mold makers who were not working in the medical device field before are now aggressively making their way into some segments of the industry, and also cross-segmenting—“for example, thermoplastic molders molding silicone and vice versa,” said Pradnya Parulekar, vice president of global business development, silicone, for RAUMEDIC in Mills River, N.C. “China is definitely a serious player when it comes to making quality tools and they are coming on aggressively.”
What OEMs Want
There is one constant in the medical device industry—OEMs want more speed and less cost. OEMs seek improvements throughout the product development process. Even if they are small improvements—an adjustment here, a modification there—they all add up to savings. For example, faster tool making and shorter tool changes help keep up with design iterations, saving time. Reduction in development time (including shorter mold validation time) and faster ramp-up to production also save time and money and contribute to faster print-to-part turnaround time.
“Medical device manufacturers are looking for fast-track turnaround time for product cycles, starting from concept through prototype, pilot run, validation, launch, and scale-up production,” said Rey Obnamia, vice president of technology and regulatory affairs at IRP Medical, a San Clemente, Calif-based provider of injection molding services, with a primary emphasis on liquid silicone rubber and high-consistency rubber.
“OEMs are looking for production-equivalent components quicker than ever before, as speed to market remains a critical focus,” added Sunday. “Those molds and the parts they produce, although considered prototype parts, are expected to be dimensionally accurate, functionally robust, and validation-ready. This has resulted in a new demand for rapid lead time tooling that is able to produce certified human-production components for product launch and Year-1 serial production.”
Molders play a bigger role than ever before in manufacturing complex medical devices. OEMs want seamless delivery across the entire product development lifecycle, which means they expect their molders to support them from prototype to production. This includes assisting with biological reactivity, cytotoxicity, and physicochemical requirements on molded components, complete process validations such as installation qualification, operational qualification, and performance qualification, and even robust risk mitigation strategies via multiple molding sites or redundant mold storage, etc. And increasingly, OEMs expect molders to make completely statistically capable parts regardless of the volumes, materials, tooling, and product design challenges. In fact, some OEMs request tolerances that are beyond the capability of most materials and injection molding processes.
“There has been a departure from reality in the design world,” said Reis. “The overuse of plus or minus 0.001 inches and use of profile tolerances have become commonplace and serve as an easy default using CAD in a perfect world. It short-circuits the reality of the effects of the molding world, the effects of poor product design, warp, shrinkage, and tooling limitations, and the variability in materials and the molding process itself.”
There is also a push to put more added value into product design, which drives more complex tooling and processing skills. An example is combining two parts into a single higher-level part by eliminating a simple assembly step, such as the inclusion of the stop cock housing to a cannula. “OEMs are also pushing the boundaries of design capabilities by molding in specific materials or features, or electronics or nanotubes, instead of trying to assemble these items into the product later,” said Parulekar.
Latest Technology Trends
The continuous drive toward miniaturization requires more micro molding. A tolerance of ±0.001 inches is fairly common in the industry (a human hair is roughly 0.002 inches thick). Holding that kind of precision repeatedly over several million parts shows how advanced the science of micromolding has become. Micro-molded components are typically complex and often have complicated shapes. Molding materials include a variety of polymers, including polyetheretherketone (PEEK), as well as heat-sensitive bioabsorbables. Sophisticated in-line inspection systems can identify variances as small as 0.0001 inches. Micro molding is especially in demand for interventional devices, surgical devices, or drug combination products, where active pharmaceutical ingredients are delivered through tiny, long-term implants.
Overmolding/insert molding combines two dissimilar materials without using primers or adhesives to achieve a robust bond that eliminates potential points of product failure and assembly/labor steps; examples include molding plastic over a preformed plastic or metal part. This is where material science really comes into play—polymers must be chosen carefully for compatibility to ensure a permanent bond. Different plastics undergo thermal expansion at different temperatures, and any incompatibilities will become serious design issues.
Increasingly complex designs are pushing the technological/production limits for advanced molding techniques such as overmolding, two-shot molding, and multi-material molding. In most cases, these require product design nuances to make the techniques work from a tooling and process standpoint, which often results in a modification from the original design. “These changes may be slightly more intrusive, depending on what needs to happen,” said Reis. “This is typically ironed out during the design for manufacturing process. If that is not possible, it may mean a complete shift in the manufacturing concept to something different. This may result in a more costly part or a process that may not be best-suited in the long term, as well as the use of cavity pressure transducers and vision systems to help ensure sound processes and quality.”
More sophisticated tools are being built by mold makers who are growing increasingly skilled with their tooling design technologies. For example, RAUMEDIC has developed a modular approach to tooling construction so that robust tooling packages can be built quickly to meet individual client needs. Engineers can create new insert stacks to fit into a wide variety of available frames. This results in a rapidly developed tool that can produce production-equivalent testable parts to support an aggressive development schedule. From there, it can be validated for certified production almost immediately after product design testing has been approved. For future needs, it can be expanded into a dedicated frame with higher cavitation, or reserved as a manufacturing spare.
The affordability of 3D printing is pushing material suppliers to provide materials that can cure quickly and still meet mechanical and regulatory requirements. Additive manufacturing and 3D printing are also forcing fabricators to seek out partners and innovative tool vendors who are able to produce proof-of-concept parts and tools within days instead of weeks. “Some of the metal treatments are making soft tools into hard tools, new curing packages are making elastomers faster to cure [some are even getting into 3D prototype fabrication], and multi-tasking presses are allowing for easier two-shot tools and multi-materials to be utilized,” said Parulekar.
Successful molders and their tool shops have responded proactively to meet these needs. Faster delivery on materials, utilizing immediately available components, lights-out 24/7 operations, and immediately available dedicated design and sampling capacities are continually being improved. “This has resulted in an unsettling trend of tooling and equipment being in place and ready to go before material is available to use for that trial order or initial sampling date,” said Sunday.
There is also an increased push for automation and robotics to maximize quality, speed, and cost savings.
“Automation, inspection, and parts handling directly out the mold is becoming the norm, especially for high-value applications,” said Snyder. “Integrated quality directly into these various systems is much more efficient than offline inspection.”
Current automation/robotics applications in molding include centralized material drying and handling for highly-automated press side assembly equipment. Cavity pressure transducers and vision systems help ensure process adherence and quality real-time as parts are manufactured. Press-mounted robotics allow for part diversion and the ability to hand-off higher level automation.
Internet of Things-driven sensor technologies can gather and analyze data in real time to optimize machine performance. For example, new processing software controls by some advanced machine suppliers, such as Engel’s iQ Weight Control, improves shot-to-shot consistency. “Automated technology like this compensates for material and molding environment fluctuations, without manual labor,” said Reis. “Overall, the ability to integrate automation within the molding process continues to expand rapidly.”
Metal injection molding (MIM) can produce parts for a wide range of medical devices. MIM is considered to be a hybrid process, where a metal powder is mixed with a thermoplastic binder and injected into a mold. The molded part is then sintered, removing the binder material and creating a net-shaped, high-density component. MIM can produce a wide variety of complex geometries from materials including titanium, tungsten alloy, ceramic, and various grades of stainless steel.
MIM is most beneficial for medium- to high-volume production of small precision parts with complicated design geometries and tight tolerances. Medical devices made with MIM include surgical instruments (ablation electrodes, endoscopic graspers and scissors, forceps, instrument bodies, scalpel handles); cardiac instruments; pacemakers; orthopedic surgery tools; screws; spine implants; trauma plates; and retinal, cochlear, and dental implants. Compared to machined and cast parts, medical MIM can cost less per unit and provides highly repeatable quality.
Advanced molding materials continue to come onto the market. For example, with the advent of power devices, fire-retardant and shielding materials are in higher demand. Materials must also be able to withstand regular sterilization treatment by radiation, chemicals, or the high heat and steam of autoclaving. The increased need to provide chemical compliance and bio-related certificates of confirmation requires more attention than in the past and is an important consideration for any development project. This trend continues to be an area of focus and required resource allocation. “As new and custom materials are created almost daily, the level of certifications required of these materials is growing more restrictive,” said Sunday. “Terms such as Registration, Evaluation, Authorization and Restriction of Chemicals (REACH), Restriction of Hazardous Substances Directive (RoHS), di(2-ethylhexyl) phthalate (DEHP), Safe Drinking Water and Toxic Enforcement Act in California (Prop 65), flame retardants, perfluorinated compounds, and heavy metals are becoming commonplace and are part of material selection considerations.”
Although new materials offer impressive performance characteristics, they face an uphill battle with MDMs because they typically take longer to validate—and MDMs are reluctant to do anything that slows down the regulatory approval process. They prefer to use materials that have been on the market for years and are well-studied and approved by the FDA.
From the molding perspective, any new material has some learning curve, especially determining long-term effects on tool steel. Is it corrosive or abrasive? What kind of life expectancy can be expected for a mold and machine components such as screws and barrels from a new material, compared to one that is well-accepted in the market? And will that material still be on the market five or 10 years from now? “Material suppliers often consolidate resins, so we try to find something that is readily available to avoid a discontinuation in the future,” said Snyder. “It’s not uncommon for a medical device to stay in the market for that length of time, so long-term availability is an important consideration.”
An Evolving Science
The science of injection molding continues to advance rapidly, driven by increasingly complex medical device designs and the need to stay competitive with other manufacturing technologies, such as advanced CNC hybrid equipment and additive manufacturing, including 3D printing. A greater variety of sophisticated tools are available to molders to predict product outcomes and monitor in-process plastic variables. Mold advances such as conformal cooling in mold plates and cavity blocks expand the potential to further reduce cycle times and address parts with non-uniform wall thickness.
Kaysun Corporation, a Manitowoc, Wis.-based provider of injection molding services to the medical industry, calls this higher-level injection molding “scientific molding.” Sensor technologies and analytical software collect and analyze operational data from the injection molding equipment to document the specifications, settings, and steps needed to ensure reproducibility over time and across equipment. “This practice is invaluable in designing and producing components for critical-use medical devices,” Kaysun stated in its online white paper, “The Importance of Scientific Molding in Medical Device Manufacturing.” Scientific molding principles are applied across all phases of medical device component manufacturing, including product design, building of the tool, debugging the tool, material selection, and the injection-molding process. Different engineers with specialized expertise oversee each of these phases.
Testing and monitoring tools that Kaysun uses during tool development and production include rheology curve (or viscosity curve), velocity profiling for determining the fastest fill rate that can be used without causing flash or other aesthetic flaws, cavity pressure readings that show pressure inside the mold, and gate seal (or gate freeze) studies. “During rheology studies, data measured during short-shot injections is used to create a viscosity curve that shows the ideal viscosity and first-stage injection speed,” said Kaysun. “By analyzing injection speed, pressure, and fill time, along with gate-seal studies, engineers determine the optimal mold parameters for a robust and repeatable process that delivers consistently defect-free components.”
Instead of the term “scientific molding,” Obnamia refers to this advanced practice as “predictive molding,” where a product’s design can be tested and verified prior to mold design/build for an efficient and effective molding process at full-scale production. These advanced tools and methodologies include 3D printing for prototyping, finite element analysis, and mold flow analysis.
“Mold flow analysis helps engineers understand how the material of choice will flow and fill the mold cavity with the least chance of molding defects and, more importantly, the number of cavities possible and cavity layout depending upon the available footprint of maximum mold size possible,” said Obnamia. “The analytical results will facilitate building the production mold scalable to maximum cavities possible.”
State-of-cure analysis is critical for medical components, especially for organic rubber compounds that come into direct contact with blood or drugs. This is achieved via traditional swell testing or non-destructive nuclear magnetic resonance.
All of these techniques are in practice now,” said Obnamia. “They provide a big advantage in achieving a robust product design of a ‘critical-to-function’ medical component, scalable to high level production at optimum efficiency and maximum performance, at a very competitive price point. As products become more complex and high precision, predictive molding will be in high demand for meeting the very specific design and performance specifications.”
Mark Crawford is a full-time freelance business and marketing/communications writer based in Madison, Wis. His clients range from startups to global manufacturing leaders. He also writes a variety of feature articles for regional and national publications and is the author of five books.
Medical device designs continue to evolve, with innovative new molded products entering the market more rapidly than ever before. “Focus continues to be on patient care and comfort, minimally invasive procedures, out-patient procedures, and treatment options that have only recently been envisioned,” said Jared Sunday, technical sales manager at RAUMEDIC, a Mills River, N.C.-based provider of extrusion, injection molding, and assembly services to the medical device industry. These products include image-guided treatments, rapid and accurate diagnostic procedures, laser-based surgical tools, micro implants, and bioabsorbable connections.
Making smaller and more complex medical devices requires more experience and precision from molders, including a deep knowledge of material behavior, especially for advanced materials. As a result, MDMs often want to work with molders that are dedicated to only making medical products. They are sometimes reluctant to partner with molders who may not have the same depth of skill and knowledge as a medical molder. In addition, MDMs expect their molder to be a steady partner and advisor through all phases of design and production.
“I get asked all the time, what percent of your business is medical?” said Randy Ahlm, CEO of NPI Medical, an Ansonia, Conn.-based provider of tooling and injection molding services to the medical device industry, with a special emphasis on prototyping. “I never used to get asked that question, but now nearly every customer wants to know. OEMs seek suppliers that can help them drive out supply chain costs and consolidate their supply base. We helped one customer consolidate from six suppliers to one, because we were able to bring multiple capabilities into play. If we were just a molder, there is no way we would have been awarded that business.”
Currently, the medical molding market is experiencing considerable consolidation with almost constant acquisitions and mergers. “In addition to M&As, the market is seeing considerable vertical integration—plastics companies buying metal companies, plastics companies buying other plastic commodities such as extrusion, plastics companies buying small contract manufacturing firms, etc.,” said Timothy Reis, vice president of healthcare business development at GW Plastics, a Bethel, Vt.-based provider of contract manufacturing, injection molding, and precision tooling.
As companies continue to acquire/merge, “it will be interesting to see how things shake out for all suppliers, not just molders,” said Dan Snyder, sales manager for Plastikos, an Erie, Pa.-based manufacturer of precision plastic components for medical devices. “We’ve seen it play both in our favor and quite the opposite, depending on the specific merger/acquisition.”
More new players are also coming into the field. Highly skilled molders and mold makers who were not working in the medical device field before are now aggressively making their way into some segments of the industry, and also cross-segmenting—“for example, thermoplastic molders molding silicone and vice versa,” said Pradnya Parulekar, vice president of global business development, silicone, for RAUMEDIC in Mills River, N.C. “China is definitely a serious player when it comes to making quality tools and they are coming on aggressively.”
What OEMs Want
There is one constant in the medical device industry—OEMs want more speed and less cost. OEMs seek improvements throughout the product development process. Even if they are small improvements—an adjustment here, a modification there—they all add up to savings. For example, faster tool making and shorter tool changes help keep up with design iterations, saving time. Reduction in development time (including shorter mold validation time) and faster ramp-up to production also save time and money and contribute to faster print-to-part turnaround time.
“Medical device manufacturers are looking for fast-track turnaround time for product cycles, starting from concept through prototype, pilot run, validation, launch, and scale-up production,” said Rey Obnamia, vice president of technology and regulatory affairs at IRP Medical, a San Clemente, Calif-based provider of injection molding services, with a primary emphasis on liquid silicone rubber and high-consistency rubber.
“OEMs are looking for production-equivalent components quicker than ever before, as speed to market remains a critical focus,” added Sunday. “Those molds and the parts they produce, although considered prototype parts, are expected to be dimensionally accurate, functionally robust, and validation-ready. This has resulted in a new demand for rapid lead time tooling that is able to produce certified human-production components for product launch and Year-1 serial production.”
Molders play a bigger role than ever before in manufacturing complex medical devices. OEMs want seamless delivery across the entire product development lifecycle, which means they expect their molders to support them from prototype to production. This includes assisting with biological reactivity, cytotoxicity, and physicochemical requirements on molded components, complete process validations such as installation qualification, operational qualification, and performance qualification, and even robust risk mitigation strategies via multiple molding sites or redundant mold storage, etc. And increasingly, OEMs expect molders to make completely statistically capable parts regardless of the volumes, materials, tooling, and product design challenges. In fact, some OEMs request tolerances that are beyond the capability of most materials and injection molding processes.
“There has been a departure from reality in the design world,” said Reis. “The overuse of plus or minus 0.001 inches and use of profile tolerances have become commonplace and serve as an easy default using CAD in a perfect world. It short-circuits the reality of the effects of the molding world, the effects of poor product design, warp, shrinkage, and tooling limitations, and the variability in materials and the molding process itself.”
There is also a push to put more added value into product design, which drives more complex tooling and processing skills. An example is combining two parts into a single higher-level part by eliminating a simple assembly step, such as the inclusion of the stop cock housing to a cannula. “OEMs are also pushing the boundaries of design capabilities by molding in specific materials or features, or electronics or nanotubes, instead of trying to assemble these items into the product later,” said Parulekar.
Latest Technology Trends
The continuous drive toward miniaturization requires more micro molding. A tolerance of ±0.001 inches is fairly common in the industry (a human hair is roughly 0.002 inches thick). Holding that kind of precision repeatedly over several million parts shows how advanced the science of micromolding has become. Micro-molded components are typically complex and often have complicated shapes. Molding materials include a variety of polymers, including polyetheretherketone (PEEK), as well as heat-sensitive bioabsorbables. Sophisticated in-line inspection systems can identify variances as small as 0.0001 inches. Micro molding is especially in demand for interventional devices, surgical devices, or drug combination products, where active pharmaceutical ingredients are delivered through tiny, long-term implants.
Overmolding/insert molding combines two dissimilar materials without using primers or adhesives to achieve a robust bond that eliminates potential points of product failure and assembly/labor steps; examples include molding plastic over a preformed plastic or metal part. This is where material science really comes into play—polymers must be chosen carefully for compatibility to ensure a permanent bond. Different plastics undergo thermal expansion at different temperatures, and any incompatibilities will become serious design issues.
Increasingly complex designs are pushing the technological/production limits for advanced molding techniques such as overmolding, two-shot molding, and multi-material molding. In most cases, these require product design nuances to make the techniques work from a tooling and process standpoint, which often results in a modification from the original design. “These changes may be slightly more intrusive, depending on what needs to happen,” said Reis. “This is typically ironed out during the design for manufacturing process. If that is not possible, it may mean a complete shift in the manufacturing concept to something different. This may result in a more costly part or a process that may not be best-suited in the long term, as well as the use of cavity pressure transducers and vision systems to help ensure sound processes and quality.”
More sophisticated tools are being built by mold makers who are growing increasingly skilled with their tooling design technologies. For example, RAUMEDIC has developed a modular approach to tooling construction so that robust tooling packages can be built quickly to meet individual client needs. Engineers can create new insert stacks to fit into a wide variety of available frames. This results in a rapidly developed tool that can produce production-equivalent testable parts to support an aggressive development schedule. From there, it can be validated for certified production almost immediately after product design testing has been approved. For future needs, it can be expanded into a dedicated frame with higher cavitation, or reserved as a manufacturing spare.
The affordability of 3D printing is pushing material suppliers to provide materials that can cure quickly and still meet mechanical and regulatory requirements. Additive manufacturing and 3D printing are also forcing fabricators to seek out partners and innovative tool vendors who are able to produce proof-of-concept parts and tools within days instead of weeks. “Some of the metal treatments are making soft tools into hard tools, new curing packages are making elastomers faster to cure [some are even getting into 3D prototype fabrication], and multi-tasking presses are allowing for easier two-shot tools and multi-materials to be utilized,” said Parulekar.
Successful molders and their tool shops have responded proactively to meet these needs. Faster delivery on materials, utilizing immediately available components, lights-out 24/7 operations, and immediately available dedicated design and sampling capacities are continually being improved. “This has resulted in an unsettling trend of tooling and equipment being in place and ready to go before material is available to use for that trial order or initial sampling date,” said Sunday.
There is also an increased push for automation and robotics to maximize quality, speed, and cost savings.
“Automation, inspection, and parts handling directly out the mold is becoming the norm, especially for high-value applications,” said Snyder. “Integrated quality directly into these various systems is much more efficient than offline inspection.”
Current automation/robotics applications in molding include centralized material drying and handling for highly-automated press side assembly equipment. Cavity pressure transducers and vision systems help ensure process adherence and quality real-time as parts are manufactured. Press-mounted robotics allow for part diversion and the ability to hand-off higher level automation.
Internet of Things-driven sensor technologies can gather and analyze data in real time to optimize machine performance. For example, new processing software controls by some advanced machine suppliers, such as Engel’s iQ Weight Control, improves shot-to-shot consistency. “Automated technology like this compensates for material and molding environment fluctuations, without manual labor,” said Reis. “Overall, the ability to integrate automation within the molding process continues to expand rapidly.”
Metal injection molding (MIM) can produce parts for a wide range of medical devices. MIM is considered to be a hybrid process, where a metal powder is mixed with a thermoplastic binder and injected into a mold. The molded part is then sintered, removing the binder material and creating a net-shaped, high-density component. MIM can produce a wide variety of complex geometries from materials including titanium, tungsten alloy, ceramic, and various grades of stainless steel.
MIM is most beneficial for medium- to high-volume production of small precision parts with complicated design geometries and tight tolerances. Medical devices made with MIM include surgical instruments (ablation electrodes, endoscopic graspers and scissors, forceps, instrument bodies, scalpel handles); cardiac instruments; pacemakers; orthopedic surgery tools; screws; spine implants; trauma plates; and retinal, cochlear, and dental implants. Compared to machined and cast parts, medical MIM can cost less per unit and provides highly repeatable quality.
Advanced molding materials continue to come onto the market. For example, with the advent of power devices, fire-retardant and shielding materials are in higher demand. Materials must also be able to withstand regular sterilization treatment by radiation, chemicals, or the high heat and steam of autoclaving. The increased need to provide chemical compliance and bio-related certificates of confirmation requires more attention than in the past and is an important consideration for any development project. This trend continues to be an area of focus and required resource allocation. “As new and custom materials are created almost daily, the level of certifications required of these materials is growing more restrictive,” said Sunday. “Terms such as Registration, Evaluation, Authorization and Restriction of Chemicals (REACH), Restriction of Hazardous Substances Directive (RoHS), di(2-ethylhexyl) phthalate (DEHP), Safe Drinking Water and Toxic Enforcement Act in California (Prop 65), flame retardants, perfluorinated compounds, and heavy metals are becoming commonplace and are part of material selection considerations.”
Although new materials offer impressive performance characteristics, they face an uphill battle with MDMs because they typically take longer to validate—and MDMs are reluctant to do anything that slows down the regulatory approval process. They prefer to use materials that have been on the market for years and are well-studied and approved by the FDA.
From the molding perspective, any new material has some learning curve, especially determining long-term effects on tool steel. Is it corrosive or abrasive? What kind of life expectancy can be expected for a mold and machine components such as screws and barrels from a new material, compared to one that is well-accepted in the market? And will that material still be on the market five or 10 years from now? “Material suppliers often consolidate resins, so we try to find something that is readily available to avoid a discontinuation in the future,” said Snyder. “It’s not uncommon for a medical device to stay in the market for that length of time, so long-term availability is an important consideration.”
An Evolving Science
The science of injection molding continues to advance rapidly, driven by increasingly complex medical device designs and the need to stay competitive with other manufacturing technologies, such as advanced CNC hybrid equipment and additive manufacturing, including 3D printing. A greater variety of sophisticated tools are available to molders to predict product outcomes and monitor in-process plastic variables. Mold advances such as conformal cooling in mold plates and cavity blocks expand the potential to further reduce cycle times and address parts with non-uniform wall thickness.
Kaysun Corporation, a Manitowoc, Wis.-based provider of injection molding services to the medical industry, calls this higher-level injection molding “scientific molding.” Sensor technologies and analytical software collect and analyze operational data from the injection molding equipment to document the specifications, settings, and steps needed to ensure reproducibility over time and across equipment. “This practice is invaluable in designing and producing components for critical-use medical devices,” Kaysun stated in its online white paper, “The Importance of Scientific Molding in Medical Device Manufacturing.” Scientific molding principles are applied across all phases of medical device component manufacturing, including product design, building of the tool, debugging the tool, material selection, and the injection-molding process. Different engineers with specialized expertise oversee each of these phases.
Testing and monitoring tools that Kaysun uses during tool development and production include rheology curve (or viscosity curve), velocity profiling for determining the fastest fill rate that can be used without causing flash or other aesthetic flaws, cavity pressure readings that show pressure inside the mold, and gate seal (or gate freeze) studies. “During rheology studies, data measured during short-shot injections is used to create a viscosity curve that shows the ideal viscosity and first-stage injection speed,” said Kaysun. “By analyzing injection speed, pressure, and fill time, along with gate-seal studies, engineers determine the optimal mold parameters for a robust and repeatable process that delivers consistently defect-free components.”
Instead of the term “scientific molding,” Obnamia refers to this advanced practice as “predictive molding,” where a product’s design can be tested and verified prior to mold design/build for an efficient and effective molding process at full-scale production. These advanced tools and methodologies include 3D printing for prototyping, finite element analysis, and mold flow analysis.
“Mold flow analysis helps engineers understand how the material of choice will flow and fill the mold cavity with the least chance of molding defects and, more importantly, the number of cavities possible and cavity layout depending upon the available footprint of maximum mold size possible,” said Obnamia. “The analytical results will facilitate building the production mold scalable to maximum cavities possible.”
State-of-cure analysis is critical for medical components, especially for organic rubber compounds that come into direct contact with blood or drugs. This is achieved via traditional swell testing or non-destructive nuclear magnetic resonance.
All of these techniques are in practice now,” said Obnamia. “They provide a big advantage in achieving a robust product design of a ‘critical-to-function’ medical component, scalable to high level production at optimum efficiency and maximum performance, at a very competitive price point. As products become more complex and high precision, predictive molding will be in high demand for meeting the very specific design and performance specifications.”
Mark Crawford is a full-time freelance business and marketing/communications writer based in Madison, Wis. His clients range from startups to global manufacturing leaders. He also writes a variety of feature articles for regional and national publications and is the author of five books.
