Molding gets even more challenging as OEMs continue to demand smaller sizes. Advanced designs in surgical tools, diagnostics and sensing devices are putting extreme pressures on supply chains to provide high-tech, intricate and micro-sized components. Customers are asking for more thin-wall applications, with tolerances as tight as 5 micrometers or less, or insert molding with unique materials like fabric or glass. Doctor feedback on devices, implants and instruments also results in next-generation design changes that push the limits of injection molding.
“The need for doing more in smaller spaces is pushing the physical limits of design and engineering,” said Aaron Johnson, sales and marketing manager for Ankeny, Iowa-based Accumold, which provides high-precision micro-molding services to medical device companies. “We are seeing an increasing number of complex molding projects that are calling for micro-molding and thin-wall molding.”
For example, catheter tubes have fixed diameters, but designers want to create more functionality inside them, such as deploying highly sophisticated devices. Requests for plastic components with wall thicknesses of .010 inches or less are almost an everyday occurrence at Accumold.
“Limits can be very material dependent,” noted Johnson. “
Geometry can also have an impact. We have molded some materials with a .003-inch wall-thickness at a 42:1 aspect ratio. Other parts we have produced are only 800 micrometer length or have features less than 1 micron in size.”
In some cases, especially with larger devices, tolerances can be “looser” and not affect the overall performance of the part or product, which also reduces cost; at micro-dimensions, however, there is very little room for variance. Also, many product designers do not have in-depth molding experience—they know the basics, but that may not be enough when it comes to designing with manufacturability in mind. This is where the experienced molder can “save the day” by bringing deep expertise in material science, mold design and production technology to the design table. With the constant evolution of new materials and production technology, leading molders stay on top of new developments that can make the process even better.
“Smaller sizes, tighter dimensional tolerances, more stringent acceptance criteria and the demand for lower-cost components continue to challenge our industry,” said Jason Nelson, manager of the New Product Development Tech Center for ProMed Molded Products Inc., a Plymouth, Minn.-based molder of silicone and plastic components and assemblies for medical device companies.“Our advanced engineering group attends all the technology shows that pertain to our industry, keeping an eye on new advancements that can help increase productivity and keep us state of the art.”
More than Just a Vendor
With so much riding on the design and operation of the mold, it’s smart to include the molder as a valued partner in the earliest stages of design to discuss part or product performance, manufacturability and cost expectations. The molder’s deep insight and knowledge in these areas are absolutely critical for success, especially in limiting or eliminating rework, redesign and unnecessary iterations.
For example, at Accumold every project goes through a design-for-manufacturability process.
Customers often bring in components they have designed based on feedback from their end users, or because of new market trends—but because they can be drawn on a CAD program does not necessarily mean they can be molded. Sometimes the engineering team also has to look beyond the part to the full-assembly design, because many parts comprise only a small section of a larger assembly.
“The most difficult part of the manufacturability process is balancing what the customer desires and what the molding process requires,” said Johnson. “For example, sometimes the customer’s requirement for a particular surface finish is located at the most ideal place for gating into the part. In this case, the mold design has to be developed from a different perspective, sometimes requiring a non-traditional or innovative approach. Also, the smaller the part, the more innovative the approach may need to be.”
Circle Pines, Minn.-based Advanced Molding Technologies LLC is a provider of clean-room medical molding and medical device assembly. One of its project management goals is getting involved with new product development as soon as possible to provide design input from a manufacturing viewpoint. This includes complete risk assessment, which can take considerable time and requires significant interaction with the customer’s design team. This also is beneficial for designing schedules and benchmarks.
“Our design-for-manufacturing collaboration allows us to work with customers to optimize their part or assembly for manufacturing, while we gain a clear understanding of the critical design features and how they affect the product’s overall functionality,” said David Johnson, engineering manager for Advanced Molding Technologies. “We then conduct a complete risk analysis and, along with the Design Failure Mode and Effects Analysis and our understanding of the part’s or assembly’s function, we can complete the Process Failure Mode Effects Analysisto mitigate any identified risks.”
During a recent design-for-manufacturability collaboration with a client, Advanced Molding Technologies identified potential risks associated with the design of a UV-cure glue joint. The original lap joint design tended to result in non-uniform glue distribution between the two mating parts; at some locations, leaks developed. “With a redesign of the glue joint to be a self-centering tongue-and-groove concept, we were able to distribute the glue consistently to three sides rather than just one, eliminating the leaks,” said Johnson.
At ProMed Molded Products, a molder of silicone and plastic components and assemblies for the device industry, a project manager or project engineer typically is assigned to work directly with an OEM on design and manufacturability issues. On a recent project, for example, a customer suggested reducing overall part cost by prototyping an insert using a different, less-expensive manufacturing technique.
“We conducted a full evaluation of the prototype insert, using this suggested manufacturing process,” said Mike Ramirez, associate engineer with ProMed Molded Products. “Our engineering report showed that this process actually compromised the bond between the silicone and the metallic insert, which would have been a problem in the field. We provided alternative design and manufacturing recommendations that still reduced costs but did not compromise performance.”
OEMs are pushing hard to “lean out” their supply chains tocontrol costs, inventories and internal resources.This requires developing highly trusted and transparent partnerships with key vendors and asking them to provide more value-added services, including design recommendations. Sometimes this requires getting actively involved in research and development. For example, at Polymer Technologies Inc., a Clifton, N.J.-based custom manufacturer of metal, plastic and ceramic injection-molded components for the medical device industry, engineers sometimes work with clients to develop new materials that provide higher performance in complex or challenging environments.
Innovative overmolding of long-term hybrid polymers can be used for implantable applications such as the hip component above. Photo courtesy of Polymer Technologies Inc. |
Using another approach, Polymer Technologies overmolds high-purity, implantable titanium with a special polymer that bonds cohesively to the metal, creating a low-friction joint. “With this, we have also developed a polymer replacement joint that requires no secondaries, and also removed any potential parting and/or witness line that, if left after molding, would abrade the joint,” added Melvyn Goldenberg, founder and director of technology for Polymer Technologies.
More Precision, Less Rework
More OEMs are asking molders to follow scientific molding principles—this especially is important with smaller, more complex devices, advanced materials and tight tolerances, where even the slightest variance in tolerance or dimension or material behavior negatively can impact performance of the device.
“Scientific molding is a science-based, systematic approach to establishing a molding process,” said Francine Petrucci, president of Aurora, Ill.-based B A Die Mold Inc., which builds molds for medical device manufacturers. “This allows to us to create molds that can repeatedly produce high-precision, miniature parts, such as needle hubs with luer locks.We follow a ‘de-coupled’ scientific approach for setting molding parameters. This involves setting the nominal melt and mold temperatures for the material, as well as developing the viscosity curve and picking a value on the low slope of the curve for the first stage of injection. We fill the shots 95-98 percent fulland add packing to achieve full parts.Then we run a gate freeze study to assure consistentpacking and a stable process has been achieved.”
Perhaps B A Die Mold Inc.’s greatest expertise lies in the innovative design and manufacture of unscrewing molds. The company’s patented PERC system is a compact, high-speed, high-torque system that uses programmable servo motors instead of hydraulics for unscrewing applications—a far more efficient way to mold threaded parts. Typical products made with PERC are needle hubs with luer locks, tuohy borst adapters and caps and fittings.
Not only is it faster, with PERC there is no need for auxiliary equipment or hydraulic oils. It is easy to set up and provides fast positioning with unlimited turns and programmable speed profiles. PERC also can help medical molders obtain or maintain clean-room certification.
“The servo motors can be sealed for clean rooms and the control cabinet can be in another room where the other press auxiliary equipment resides,” said Petrucci. “PERC is a clean/green alternative to conventional, messy hydraulic unscrewing. Even medical device manufacturers who do not require clean room molding can benefit—when they have potential customers touring their facilities they want their manufacturing cells to be as clean as possible.”
For some medical markets, aesthetics also is an important consideration when it comes to product design. OEMs want their products to be stylish and visually attractive, which can be accomplished with a greater variety of colors and textures, overmolded surfaces and glossy or matte finishes. More durable and UV-resistant paints or antibacterial paints also may be required.
“In our market segment, the trend is toward higher cosmetic value,” said Doug Culbertson, vice president of Premold Corporation, an Oconomowoc, Wis.-based supplier of molded housings, bezels and skins for medical and laboratory instruments. “Not only do companies want their products to be functionally reliable, they want them to be visually attractive and stand out from the competition.”
One way of improving appearance (and sometimes function) is by designing more complex molds that include some of the individual parts that originally were conceived for the product, thereby reducing the number of pieces that need to be molded and assembled. This also eliminates visible joining lines and fasteners and minimizes issues with stack-up values.
“We recently partnered with an ultrasound OEM on the design of its housings and reduced the number of molds from five to two,” said Culbertson. “The two molds were more complex, but did not change the dimensional design of the package. This improved the cosmetics, reduced tooling cost, reduced overall part cost and reduced system assembly cost.”
Advanced Technologies and Materials
Many OEMs are trying to get away from machining thermoplastics and molding them instead to reduce costs. Molding-related technologies continue to improve, including more accurate and repeatable molding machines, cold decks, vision systems, coordinate measuring machines and robotics. Improvements to tooling design and injection-molding machines enable extreme precision even at the micro level, proprietary material delivery systems and wash systems.
Early work with customers optimizes assembly and manufacturing. It also provides understanding of critical features and how they affect the product’s function. Photo courtesy of Advanced Molding Technologies. |
Micro-structure-enhancement molding is another advanced process that can mold tiny substructures onto the surface of the plastic. These features can be as small as a few microns and, in some cases, even sub-micron. “This technology is useful for applications like micro-fluidics, diffractive optics or any part that requires a finely detailed structure,” said Aaron Johnson.
Silicone increasingly is in demand for components such as seals, grommets, suture sleeves, combination products, neurological implants, urological devices, respiratory care, rings, catheters, tubing, IV fluid handling, dialysis and more.
“Silicone has unique physical properties,” said Ramirez.“It’s flexible and durable.Medical-grade silicone is not harmful when in contact with the human body’s blood path. Another attractive property is that many pharmaceuticals have excellent elution properties when mixed with silicone—this is why so many OEMs are now looking into drug-eluting silicone products.”
Some OEMs, however, do not completely understand design for manufacturability for products made of silicone. Design engineers tend to approach silicone materials the way they do plastics. The biggest disconnect for designers with silicone is dimensional tolerance.Even though silicone is flexible, “some designers do not always account for this and specify what can sometimes be unnecessary and hard-to-achieve tolerances for the part,” said Ramirez.
Another big challenge with molding silicone is that, in their raw material form, the most commonly used silicones are liquids.
“Liquids always seek the path of least resistance when flowing,” said Ramirez.“Many mold designers and other manufacturers design silicone molds like they would plastics molds.This can cause a lot of issues with silicone flash getting in places that plastic would not, like ejector pins and bars, if not properly accounted for.This makes part removal and automation more challenging and often requires a creative approach that is quite different from what would be used on a plastic part of the exact same geometry.”
Silicone also can be micro-molded and insert overmolded. These processes, however, require special engineering expertise and equipment to automate the removal of the sticky, soft, flexible and geometrically complex part—often miniature in size and with thin walls—without altering its shape.
Special molding equipment and procedures sometimes also must be developed for unique advanced materials such as Eastman’s Tritan Copolyester WX500, which is being used as a BPA-free alternative material in medical devices. Tritan’s high melt strength, toughness, hydrolytic stability and heat and chemical resistance make it ideal for the manufacture of large bottles and other food containers.
“We use Triton for molded components in blood oxygenator devices,” said David Johnson. “This material has unique and challenging properties from a processing perspective. It is very sensitive to mold and melt temperatures. Uniform mold cooling and maintaining tight controls on the melt temperature are critical. Mold steel selection and considerations for draft and plating also need to be addressed during mold design.”
Looking to the Future
With the rapidly increasing numbers of retired baby boomers, and about 30 million Americans that will become newly insured under the Affordable Care Act, medical devices will be in high demand. However, revenue growth within this market will be challenged by changes in reimbursement formulas and by the medical device tax, forcing OEMs to become more cost- and process-efficient, optimizing both internal and external resources.As a result, OEMs are expecting the same of their suppliers.
“In order to meet these challenges, injection molding companies must achieve higher cost efficiency within their organizations, which will result in the ability to provide cost savings to their customers,” said Myhre. “Automation, lean processing, diversity (providing value-added services) and developing innovative material options versus high-cost materials, such as titanium, are at the forefront of what we are seeing with the injection molding industry.”
Ramirez agrees automation will be a rapidly advancing trend in medical molding.
“To meet pricing pressures, everything needs to be automated,” said Ramirez. “Not very many manual operations will be coming out of ProMed over the next few years—there is simply no advantage to manual molding any longer. Non-recurring engineering, product development, piece part price and development time are all improved when proper automated platforms are used.”
Another cost-reduction strategy is near-shoring. About six years ago ProMed opened a facility in Dorado, Puerto Rico, to provide customers with a lower-cost alternative. “This proactive approach seemed to be the best of both worlds by allowing us to have lower labor rates, but still be part of the United States,” said Connie Laumeyer, director of sales and marketing for ProMed. “Customers have embraced both options.”
OEMs continue to push molders to improve lead times on new tools and validation processes—this is always a challenge, especially as devices continue to get smaller and more complex. One of the best ways to reduce lead times, indicated Advanced Molding Technologies’ Johnson, is by streamlining the validation process.
“It is often a delicate balance of ensuring that everything is completed and documented as required, with the need to get it done faster,” said David Johnson. “At Advanced Molding Technologies, the best way we can manage this is to have constant communication with our customers and ensure that the validation protocol is developed and clearly understood by all parties prior to the mold completion. Having this in place ahead of time allows us to be prepared and most efficient with the validation activities once the mold is delivered. This could mean completing validation for a molded part in six weeks versus three months.”
Mark Crawford is a full-time freelance business and marketing/communications writer based in Madison, Wis. He also writes a variety of feature articles for regional and national publications and is the author of five books. Contact him at mark.crawford@charter.net.