Ranica Arrowsmith, Associate Editor06.02.15
A few years ago, a certain set of “crazy job interview questions” made the rounds. One of these (real) questions was, “How do you think M&M candies are coated with their colored shell?” The interviewer didn’t care about—and may not even have known—the correct answer. The question was supposed to elicit creative, quick thinking, allowing interviewers to evaluate how a potential employee thinks on her feet. In various magazine and website articles, commentators gave their answers: the chocolate balls are dropped through the air and sprayed with a colored sugar coating as they fall; colored sugar is poured over the candies and they are rolled around in a device with gears until the desired shape is formed; they are then polished to a shine. The answers vary.
A medical device manufacturer, however, may have had better insight into how these multicolored candies get their signature coatings. Dip molding is a process that some molding providers use instead of injection molding as its low cost enables low production runs. It is a simple matter of dipping a mandril (an object in the inverse shape of what a manufacturer wants the produced object’s shape to be) into plastisol, a suspension of polyvinyl chloride (PVC) particles in a liquid plasticizer, cooling and removing the hardened plastic object. Common medical devices made in this method are nasal cannulas and stethoscopes. Many coated candies and cookies get their coating this way. Incidentally, this is not how M&Ms get their coating—but it would have made a good answer.
The advantage of dip molding is that the tooling is inexpensive and consequentially can be used to perform short runs. As a result, many parts can be produced for pennies apiece. The technique also is good for manufacturing thin-wall parts in a cost-effective way. Consequently, it can be used to manufacture such medical devices as balloons. When using such materials as PVC or plastisol, dip molding can create devices with walls ranging in thickness from 0.008 to 0.010 inches. When using latex, wall thicknesses down to 0.004 or 0.005 inches can be achieved. Thus, the technology can make very thin-wall parts. In addition to the technology’s ability to produce thin-wall components, it works with such shape-memory stretchable, elastic materials as latex and more-rigid materials such as PVC.
Innovative yet simple and refined processes such as dip molding have allowed molding, which has been a mainstay in the manufacturing world, to remain a coveted and necessary manufacturing process for medical devices. In fact, of all the processes available to manufacturers such as subtractive, machining and additive, molding is the most commonly used process across industries. Its touchstones are the ability to produce large volume outputs at a low per-item cost—the high volume offsetting the high cost of molds.
Molds are expensive. Varying greatly on complexity, quality, and size, a mold can cost anywhere from $2,000-$3,000 for a simple, single cavity mold, or $60,000-$100,000 or more for a high production, multi-cavity mold made with hardened tool steel. It can take between two to 12 weeks to build a molding tool. To make an easy comparison, 3-D printers and other additive manufacturing machines come ready-made, as such machines can make any type of shape or complex geometry with a tweak to the design input in the software.
Recently there has been discussion in the medical device industry about whether new methods of additive manufacturing will one day supplant molding as the most-used, cheapest manufacturing process worldwide because of 3-D printing’s capability to produce small runs and more customized devices and components. However, the reality is that 3-D printing has only bolstered molding as a process while establishing strong footholds of its own. With the ability to 3-D print molds, for instance, molds do not have to be as expensive as they once were. This low-cost model also allows for smaller runs, allowing device manufacturers to produce wider size ranges of a component in smaller lots, for example. This, along with processes such as dip molding, has expanded the possibilities molding offers. Molding is only advancing in sophistication, aided by advances in other areas of manufacturing.
Living in a Material World
One of the key movements in medical device molding is the evolution of metal, glass and ceramic parts to plastics. As materials science advances, plastics now have the capability to last longer, withstand higher temperatures, and present greater wear resistance than some metals. This has prompted OEMs to move to convert many devices and device components to plastic, both biocompatible and otherwise, depending on the application of the device. Although plastics present more of a problem in terms of environmental impact in disposal, the benefits of plastics are particularly apparent in medicine and public health. Single-use devices made of low-cost polymers, for instance, reduce the risk of hospital acquired infections.
“The plastic materials now available to produce medical, diagnostic and orthopedic components are enabling the aforementioned industries to develop technologies that could have not been imagined 10 years ago,” Ryan Heidenfeld, process engineering manager for Medbio Inc., a contract manufacturer specializing in injection molding, injection mold tooling and assembly and packaging, told Medical Product Outsourcing. “We are being asked to ‘push the envelope’ regarding the geometries that can be injection molded. Material-science developments have allowed us to offer solutions for difficult-to-manufacture components. Metal-to-plastic conversions in the implantable and surgical instrument sectors has become commonplace. Glass-to-plastic conversions are also very common in the diagnostics arena.”
Much has been made of the negative implications of all-metal implants, particularly hip implants, several brands of which have been shown to deposit tiny metal fragments into the surrounding tissue after wear. Potential wear is one of the major attractions to converting metal components to plastic. Another of course, is cost, as plastics cost far less than specialized metals to obtain and process. High-performance polymers offer similar and sometimes better levels of strength and rigidity as some metals at ambient temperatures. In addition to cost benefits, they offer enhanced aesthetics and ergonomic improvements such as a range of grip options. High-performance polymers also can be colored, thus enabling the production of devices in a variety of sizes that can easily and quickly be identified in the operating room.
“One significant development in the industry is the need to combine different materials in order to include soft touch and aesthetic features, or even more importantly, for applications that require reliable sealing solutions or connections to other mating parts,” explained Rudi Gall, managing director for Raumedic Inc., an extrusion, injection molding and assembly provider. “Such materials can be combined by molding techniques such as two-shot molding or overmolding, which are both offered by Raumedic.
“In a two-shot molding—also called a multi-component injection molding process—a hard thermoplastic polymer, such as polypropylene, is molded in the first shot and a soft thermoplastic polymer, such as a SRT (synthetic rubber thermoplastic) or TPE (thermoplastic elastomer), is added in a second shot, allowing both to be combined in one product without post-assembly. The soft component connects to the hard component and can only be separated through destructive force. This allows for a perfect seal and/or connection and makes the product perfectly safe, an important factor in any medical device or pharmaceutical application.”
“In recent years, a large step forward has been made in materials used for the delivery of pharmaceuticals and for bio-absorbable materials,” said Michael Leslie, new product development engineer for ProMed Molded Products Inc., a Plymouth, Minn.-based company that specializes in the molding of small, tightly toleranced components and assemblies for the medical industry. “Many of these materials are proprietary, meaning there is little to no history on the processing of these materials. This has introduced a new level of molding development which requires the use of scientific molding, much more than when the majority of materials used in molding had a long history of processing, such as PEEKs (polyether ether ketone), PSUs (polysulfone), and TPUs (thermoplastic polyurethane).”
However, all is not rosy in the world of plastics. One might assume that polymers, unlike metals, are a never-ending resource because they are a manufactured material. Late last year, Riyadh, Saudi Arabia-based SABIC Innovative Plastics, the only manufacturer of a plastic known as Ultem, announced a shortage of the material. The Ultem resin (resin is synonymous with plastic in the plastics world) family of amorphous thermoplastic polyetherimide resins is fashioned to offer elevated thermal resistance, high strength and stiffness and broad chemical resistance. Its shortage is due to a rapid growth in demand for the polymer, and the company anticipated significant shortages through the second quarter of 2015—i.e., now. This shortage has of course raised the price of Ultem significantly. In March, the company announced its plans to add more than 700 million pounds of material production capacity in the next five years, including a 30 percent capacity increase into Ultem.
Ultem’s use in high-temperature electric components and aerospace applications alone demonstrate why this resin is so desirable among medical device manufacturers looking to create durable devices. The material has a very high heat threshold at 340 degrees Fahrenheit. Ultem also is hydrolysis resistant, highly resistant to acidic solutions and can tolerate repeated autoclaving cycles, such as with the repeated steam sterilization required of reusable medical devices. These properties were a major contributing factor to the current shortage, as Ultem’s desirability drove demand too high for SABIC to keep up with.
This is how a man-made material can mimic precious metals in scarcity and value fluctuations. One company holding the trademark over such a coveted commodity can create a monopoly and trigger supply issues.
Behind the Machine
While the general concept of molding, i.e. using a cast to shape a whole object, has existed since humans started using the most primitive of tools, the process of injection molding has been in existence since the late 1800s. Either way, it is a proven process, and advancements not only in material but technique and manufacturing technology have allowed it to retain its hold in the manufacturing marketplace.
“Most customers that come to us are typically on the verge of making a decision. Is it time to spend money on an injection mold? They’re leveraging their quantities,” said Tom Star, president of Riverside, Calif.-based Molded Devices Inc.’s Tempe, Ariz. molding operations. “Injection molding doesn’t really make sense until you get over 5,000-10,000 pieces a month because of the cost of tooling. Additive manufacturing and some of these other entry points into the market make a lot of sense until you get up to that 10,000 range. Molding offers OEMs the opportunity to leverage the economy of scale. That’s tried and true, that’s always been the case, but with the advance of technologies such as additive manufacturing, the materials you can 3-D print now even include metals. So an injection molder can actually make core and cavity sets through the 3-D printing process to get you to say 50-100 parts. And a lot of times a customer will want to mold 100 pieces so they can submit them through for biocompatability and proof of concept testing, but they need it in an injection molded form because you can hold the precision tolerances much better than you can in a 3-D printing process. And you need have the parts in the right material for biocompatibility tests. 3-D printing allows for using some U.S. Pharmacopeial Convention class VI materials but not all at this point unless you have an Arburg Freeformer. So technology has really affected that in the last five years, because now a customer can spend a lot less money getting to a precision component much quicker and much faster, and it’ll serve their needs.”
Unlike conventional additive manufacturing techniques, with Arburg Plastic Freeforming, standard granulates are melted as they are in the injection molding process. The freeformer produces the component layer by layer from minuscule droplets. The discharge unit with nozzle remains stationary, while the component carrier moves.
“Our company uses specific mold tools with rotary technology with defined mold rotations, of e.g. 180 degrees,” added Raumedic’s Gall. “A multi-component injection molded product eliminates established assembly and sometimes labor intensive assembly processes, thus reducing cost and offering more robust and reliable product solutions.
“An overmolding process on the other hand allows you to add customer-specific hubs and connectors to an extruded part, such as tubing. For a long time it was an industry standard to assemble molded connectors to a tube with help of solvent bonding or adhesive bonding in a secondary process. Overmolding can eliminate established assembly processes, thus reducing cost and offering a more robust production solution. It also allows you to eliminate any kind of health and environmental concerns related to solvents used in the solvent bonding process. A good example for devices with need for such molding capabilities are injection devices. Fully automated handling with linear or six-axis robot systems allow for direct overmolding with a polymer injection molded part.
“For such devices also an insert molding process could come into play, whereby a metal needle can be directly overmolded with a two-component injection molding technology, first with a soft polymer and subsequently with a hard polymer, whereby the soft component also offers a sealing function feature. The adhesion between the metal insert and the polymer is comparable with the adhesion achieved with help of an ultraviolet bonding solution. Insert-molded devices are particularly of interest for industries, such as biotechnology and the pharmaceutical industry, in which extractables and leachables are of concern, as any given drug only comes into contact with the polymer and the needle but not with any adhesive used.”
Overmolding is a type of multi-material molding by which an overmold is injected over, under, around or through a substrate material. Usually, the overmolded material is elastomeric resin, which allows for a soft touch on components such as handles or buttons. A soft touch is what the technique is known for, but it also can improve ergonomics and add functionality such as noise and vibration dampening, water- and shock-proofing.
Overmolding also is just one example of the ways in which two different materials can be integrated into a seamless whole. Consolidation is key as device technology advances, as simplifying a multi-component device into less or even one part saves time and money.
“One of our challenges has always been to consolidate, where possible, parts into net shapes,” said David Hanna, new business unit manager for Alliance Precision Plastics Corp., a Rochester, N.Y.-based injection molding solutions provider. “So what may have been two, three or four metal parts can now be molded as one plastic component. The material development, which has led to higher temperature resistance or higher impact materials that are medical grade, has allowed us to go forward with those designs and really create parts that weren’t available before. So now we’re routinely making components that are autoclavable or resistant to higher temperatures and impact forces that 10 or even five years ago weren’t possible.”
Outside of the manufacturing process, supply chain improvements also advance medical device molding. OEMs consistently have been wanting to consolidate their outsourcing to fewer service providers, so companies that can streamline manufacturing and offer more services win.
“Major OEMs are really keen on suppliers that can offer more than one technology,” Star observed. “There’s a huge push to shrink the vendor base. That’s been going on for 15 years or so, but for many companies the cost of entering into those technologies didn’t make sense at the time. Now that’s becoming much more feasible.”
“Two of the most impactful technologies have been improved automation and online inspection,” said ProMed’s Leslie. “Both of these help improve cycle times and the defect rate by stabilizing cycle times and achieving consistency. Molding machines built for micro-molding have also helped advance the industry of molding by expanding the ability of molding into new territories. All electric machines that have high repeatability and capability make parts possible that once were never considered to be moldable.”
Scaling Down
Miniaturization of devices is a trend that is both inevitable and necessary in a medical device market that is seeking less invasive procedures as well as more wearable technologies that are user-friendly for the patient. In fact, miniaturization of medical devices in some ways is closely tied to the scaling-down consumer electronics has experienced since the advent of cell phones and personal gaming devices mere decades ago. Insulin pumps, for instance, now often look like smart phones, which make them intuitive and attractive for patients, especially younger and older patients, to use without difficulty. The parts that go into such an electronic can be extremely tiny. But as Aaron Johnson from Ankeny, Iowa-based micro and injection molding company Accumold LLC explained to MPO, “tiny” is relative. What is considered miniature is only based on the user or manufacturer’s experience and goals.
“There’s no textbook definition for micro-molding, but in our experience we’re often dealing with features and geometry requirements that aren’t really achievable yet through 3-D printing, so it’s a matter of perspective,” said Johnson, vice president of marketing and customer strategy at Accumold. “Is someone who’s making large housings for a medical instrument saying that that’s micro-molding because it’s smaller than they’re used to dealing with? It all depends on the perspective on what you’re calling ‘micro’ or what you’re calling a ‘fine feature.’ We did a study recently to show the differences between the commercially available prototyping processes, and if you’re looking for features in microns and tolerances in microns, 3-D printing hasn’t quite gotten there yet. We’re hopeful that someday it will because it’s a complementary technology, to help those that are designing new products to have faster ways to work through research and development. 3-D printing doesn’t necessarily give you a manufacturable process or a production-like material or process in a lot of cases. There are definitely some distinct advantages and we’re watching the 3-D market advance. But pretty much anything that we micro-mold, they would no-quote. I mean, we have one part that’s only 800 microns long and has features that are smaller than that. 3-D printing is a fabulous technology that can do a lot of great things and has a great application, but just like anything else, it has its limits.”
“The trend toward miniaturization due to the rise of minimally invasive procedures requires smaller products, tolerances, wall thicknesses and an increasing demand to show process capabilities that can control the production of such complex parts,” added Gall. Raumedic also specializes in micro-molded parts. “Such demands are answered by Raumedic with the investment in specialty micro-molding equipment/molding presses. The size of micro-molded parts is in the range of one single pellet, working with part weights down to 0.004 grams. Besides standard thermoplastics such as PE (polyethylene), PA (nylon), PC (polycarbonate) and PUR (polyurethane), high temperature thermoplastics such as PEEK, PSU and PPSU (polyphenylsulfone) can also be used for this specialized molding process. Again different molding processes can be combined, e.g., by overmolding a micro-molded atraumatic tip on an extruded PEEK guide catheter used in cardiovascular applications. The challenge is that micro-molded parts have many of the same features as traditional molded parts, such as gates, ventings, knit lines and parting lines. Micro-molded components must be qualified and validated like any traditional component. This requires accurate measurement and demonstrated repeatability while working on the miniature level, with parts so small that their features are hardly visible to the naked eye. Special jigs, fixtures, measurement devices but foremost well-trained operators are needed to qualify such components.”
A medical device manufacturer, however, may have had better insight into how these multicolored candies get their signature coatings. Dip molding is a process that some molding providers use instead of injection molding as its low cost enables low production runs. It is a simple matter of dipping a mandril (an object in the inverse shape of what a manufacturer wants the produced object’s shape to be) into plastisol, a suspension of polyvinyl chloride (PVC) particles in a liquid plasticizer, cooling and removing the hardened plastic object. Common medical devices made in this method are nasal cannulas and stethoscopes. Many coated candies and cookies get their coating this way. Incidentally, this is not how M&Ms get their coating—but it would have made a good answer.
The advantage of dip molding is that the tooling is inexpensive and consequentially can be used to perform short runs. As a result, many parts can be produced for pennies apiece. The technique also is good for manufacturing thin-wall parts in a cost-effective way. Consequently, it can be used to manufacture such medical devices as balloons. When using such materials as PVC or plastisol, dip molding can create devices with walls ranging in thickness from 0.008 to 0.010 inches. When using latex, wall thicknesses down to 0.004 or 0.005 inches can be achieved. Thus, the technology can make very thin-wall parts. In addition to the technology’s ability to produce thin-wall components, it works with such shape-memory stretchable, elastic materials as latex and more-rigid materials such as PVC.
Innovative yet simple and refined processes such as dip molding have allowed molding, which has been a mainstay in the manufacturing world, to remain a coveted and necessary manufacturing process for medical devices. In fact, of all the processes available to manufacturers such as subtractive, machining and additive, molding is the most commonly used process across industries. Its touchstones are the ability to produce large volume outputs at a low per-item cost—the high volume offsetting the high cost of molds.
Molds are expensive. Varying greatly on complexity, quality, and size, a mold can cost anywhere from $2,000-$3,000 for a simple, single cavity mold, or $60,000-$100,000 or more for a high production, multi-cavity mold made with hardened tool steel. It can take between two to 12 weeks to build a molding tool. To make an easy comparison, 3-D printers and other additive manufacturing machines come ready-made, as such machines can make any type of shape or complex geometry with a tweak to the design input in the software.
Recently there has been discussion in the medical device industry about whether new methods of additive manufacturing will one day supplant molding as the most-used, cheapest manufacturing process worldwide because of 3-D printing’s capability to produce small runs and more customized devices and components. However, the reality is that 3-D printing has only bolstered molding as a process while establishing strong footholds of its own. With the ability to 3-D print molds, for instance, molds do not have to be as expensive as they once were. This low-cost model also allows for smaller runs, allowing device manufacturers to produce wider size ranges of a component in smaller lots, for example. This, along with processes such as dip molding, has expanded the possibilities molding offers. Molding is only advancing in sophistication, aided by advances in other areas of manufacturing.
Living in a Material World
One of the key movements in medical device molding is the evolution of metal, glass and ceramic parts to plastics. As materials science advances, plastics now have the capability to last longer, withstand higher temperatures, and present greater wear resistance than some metals. This has prompted OEMs to move to convert many devices and device components to plastic, both biocompatible and otherwise, depending on the application of the device. Although plastics present more of a problem in terms of environmental impact in disposal, the benefits of plastics are particularly apparent in medicine and public health. Single-use devices made of low-cost polymers, for instance, reduce the risk of hospital acquired infections.
“The plastic materials now available to produce medical, diagnostic and orthopedic components are enabling the aforementioned industries to develop technologies that could have not been imagined 10 years ago,” Ryan Heidenfeld, process engineering manager for Medbio Inc., a contract manufacturer specializing in injection molding, injection mold tooling and assembly and packaging, told Medical Product Outsourcing. “We are being asked to ‘push the envelope’ regarding the geometries that can be injection molded. Material-science developments have allowed us to offer solutions for difficult-to-manufacture components. Metal-to-plastic conversions in the implantable and surgical instrument sectors has become commonplace. Glass-to-plastic conversions are also very common in the diagnostics arena.”
Much has been made of the negative implications of all-metal implants, particularly hip implants, several brands of which have been shown to deposit tiny metal fragments into the surrounding tissue after wear. Potential wear is one of the major attractions to converting metal components to plastic. Another of course, is cost, as plastics cost far less than specialized metals to obtain and process. High-performance polymers offer similar and sometimes better levels of strength and rigidity as some metals at ambient temperatures. In addition to cost benefits, they offer enhanced aesthetics and ergonomic improvements such as a range of grip options. High-performance polymers also can be colored, thus enabling the production of devices in a variety of sizes that can easily and quickly be identified in the operating room.
“One significant development in the industry is the need to combine different materials in order to include soft touch and aesthetic features, or even more importantly, for applications that require reliable sealing solutions or connections to other mating parts,” explained Rudi Gall, managing director for Raumedic Inc., an extrusion, injection molding and assembly provider. “Such materials can be combined by molding techniques such as two-shot molding or overmolding, which are both offered by Raumedic.
“In a two-shot molding—also called a multi-component injection molding process—a hard thermoplastic polymer, such as polypropylene, is molded in the first shot and a soft thermoplastic polymer, such as a SRT (synthetic rubber thermoplastic) or TPE (thermoplastic elastomer), is added in a second shot, allowing both to be combined in one product without post-assembly. The soft component connects to the hard component and can only be separated through destructive force. This allows for a perfect seal and/or connection and makes the product perfectly safe, an important factor in any medical device or pharmaceutical application.”
“In recent years, a large step forward has been made in materials used for the delivery of pharmaceuticals and for bio-absorbable materials,” said Michael Leslie, new product development engineer for ProMed Molded Products Inc., a Plymouth, Minn.-based company that specializes in the molding of small, tightly toleranced components and assemblies for the medical industry. “Many of these materials are proprietary, meaning there is little to no history on the processing of these materials. This has introduced a new level of molding development which requires the use of scientific molding, much more than when the majority of materials used in molding had a long history of processing, such as PEEKs (polyether ether ketone), PSUs (polysulfone), and TPUs (thermoplastic polyurethane).”
However, all is not rosy in the world of plastics. One might assume that polymers, unlike metals, are a never-ending resource because they are a manufactured material. Late last year, Riyadh, Saudi Arabia-based SABIC Innovative Plastics, the only manufacturer of a plastic known as Ultem, announced a shortage of the material. The Ultem resin (resin is synonymous with plastic in the plastics world) family of amorphous thermoplastic polyetherimide resins is fashioned to offer elevated thermal resistance, high strength and stiffness and broad chemical resistance. Its shortage is due to a rapid growth in demand for the polymer, and the company anticipated significant shortages through the second quarter of 2015—i.e., now. This shortage has of course raised the price of Ultem significantly. In March, the company announced its plans to add more than 700 million pounds of material production capacity in the next five years, including a 30 percent capacity increase into Ultem.
Ultem’s use in high-temperature electric components and aerospace applications alone demonstrate why this resin is so desirable among medical device manufacturers looking to create durable devices. The material has a very high heat threshold at 340 degrees Fahrenheit. Ultem also is hydrolysis resistant, highly resistant to acidic solutions and can tolerate repeated autoclaving cycles, such as with the repeated steam sterilization required of reusable medical devices. These properties were a major contributing factor to the current shortage, as Ultem’s desirability drove demand too high for SABIC to keep up with.
This is how a man-made material can mimic precious metals in scarcity and value fluctuations. One company holding the trademark over such a coveted commodity can create a monopoly and trigger supply issues.
Behind the Machine
While the general concept of molding, i.e. using a cast to shape a whole object, has existed since humans started using the most primitive of tools, the process of injection molding has been in existence since the late 1800s. Either way, it is a proven process, and advancements not only in material but technique and manufacturing technology have allowed it to retain its hold in the manufacturing marketplace.
“Most customers that come to us are typically on the verge of making a decision. Is it time to spend money on an injection mold? They’re leveraging their quantities,” said Tom Star, president of Riverside, Calif.-based Molded Devices Inc.’s Tempe, Ariz. molding operations. “Injection molding doesn’t really make sense until you get over 5,000-10,000 pieces a month because of the cost of tooling. Additive manufacturing and some of these other entry points into the market make a lot of sense until you get up to that 10,000 range. Molding offers OEMs the opportunity to leverage the economy of scale. That’s tried and true, that’s always been the case, but with the advance of technologies such as additive manufacturing, the materials you can 3-D print now even include metals. So an injection molder can actually make core and cavity sets through the 3-D printing process to get you to say 50-100 parts. And a lot of times a customer will want to mold 100 pieces so they can submit them through for biocompatability and proof of concept testing, but they need it in an injection molded form because you can hold the precision tolerances much better than you can in a 3-D printing process. And you need have the parts in the right material for biocompatibility tests. 3-D printing allows for using some U.S. Pharmacopeial Convention class VI materials but not all at this point unless you have an Arburg Freeformer. So technology has really affected that in the last five years, because now a customer can spend a lot less money getting to a precision component much quicker and much faster, and it’ll serve their needs.”
Unlike conventional additive manufacturing techniques, with Arburg Plastic Freeforming, standard granulates are melted as they are in the injection molding process. The freeformer produces the component layer by layer from minuscule droplets. The discharge unit with nozzle remains stationary, while the component carrier moves.
“Our company uses specific mold tools with rotary technology with defined mold rotations, of e.g. 180 degrees,” added Raumedic’s Gall. “A multi-component injection molded product eliminates established assembly and sometimes labor intensive assembly processes, thus reducing cost and offering more robust and reliable product solutions.
“An overmolding process on the other hand allows you to add customer-specific hubs and connectors to an extruded part, such as tubing. For a long time it was an industry standard to assemble molded connectors to a tube with help of solvent bonding or adhesive bonding in a secondary process. Overmolding can eliminate established assembly processes, thus reducing cost and offering a more robust production solution. It also allows you to eliminate any kind of health and environmental concerns related to solvents used in the solvent bonding process. A good example for devices with need for such molding capabilities are injection devices. Fully automated handling with linear or six-axis robot systems allow for direct overmolding with a polymer injection molded part.
“For such devices also an insert molding process could come into play, whereby a metal needle can be directly overmolded with a two-component injection molding technology, first with a soft polymer and subsequently with a hard polymer, whereby the soft component also offers a sealing function feature. The adhesion between the metal insert and the polymer is comparable with the adhesion achieved with help of an ultraviolet bonding solution. Insert-molded devices are particularly of interest for industries, such as biotechnology and the pharmaceutical industry, in which extractables and leachables are of concern, as any given drug only comes into contact with the polymer and the needle but not with any adhesive used.”
Overmolding is a type of multi-material molding by which an overmold is injected over, under, around or through a substrate material. Usually, the overmolded material is elastomeric resin, which allows for a soft touch on components such as handles or buttons. A soft touch is what the technique is known for, but it also can improve ergonomics and add functionality such as noise and vibration dampening, water- and shock-proofing.
Overmolding also is just one example of the ways in which two different materials can be integrated into a seamless whole. Consolidation is key as device technology advances, as simplifying a multi-component device into less or even one part saves time and money.
“One of our challenges has always been to consolidate, where possible, parts into net shapes,” said David Hanna, new business unit manager for Alliance Precision Plastics Corp., a Rochester, N.Y.-based injection molding solutions provider. “So what may have been two, three or four metal parts can now be molded as one plastic component. The material development, which has led to higher temperature resistance or higher impact materials that are medical grade, has allowed us to go forward with those designs and really create parts that weren’t available before. So now we’re routinely making components that are autoclavable or resistant to higher temperatures and impact forces that 10 or even five years ago weren’t possible.”
Outside of the manufacturing process, supply chain improvements also advance medical device molding. OEMs consistently have been wanting to consolidate their outsourcing to fewer service providers, so companies that can streamline manufacturing and offer more services win.
“Major OEMs are really keen on suppliers that can offer more than one technology,” Star observed. “There’s a huge push to shrink the vendor base. That’s been going on for 15 years or so, but for many companies the cost of entering into those technologies didn’t make sense at the time. Now that’s becoming much more feasible.”
“Two of the most impactful technologies have been improved automation and online inspection,” said ProMed’s Leslie. “Both of these help improve cycle times and the defect rate by stabilizing cycle times and achieving consistency. Molding machines built for micro-molding have also helped advance the industry of molding by expanding the ability of molding into new territories. All electric machines that have high repeatability and capability make parts possible that once were never considered to be moldable.”
Scaling Down
Miniaturization of devices is a trend that is both inevitable and necessary in a medical device market that is seeking less invasive procedures as well as more wearable technologies that are user-friendly for the patient. In fact, miniaturization of medical devices in some ways is closely tied to the scaling-down consumer electronics has experienced since the advent of cell phones and personal gaming devices mere decades ago. Insulin pumps, for instance, now often look like smart phones, which make them intuitive and attractive for patients, especially younger and older patients, to use without difficulty. The parts that go into such an electronic can be extremely tiny. But as Aaron Johnson from Ankeny, Iowa-based micro and injection molding company Accumold LLC explained to MPO, “tiny” is relative. What is considered miniature is only based on the user or manufacturer’s experience and goals.
“There’s no textbook definition for micro-molding, but in our experience we’re often dealing with features and geometry requirements that aren’t really achievable yet through 3-D printing, so it’s a matter of perspective,” said Johnson, vice president of marketing and customer strategy at Accumold. “Is someone who’s making large housings for a medical instrument saying that that’s micro-molding because it’s smaller than they’re used to dealing with? It all depends on the perspective on what you’re calling ‘micro’ or what you’re calling a ‘fine feature.’ We did a study recently to show the differences between the commercially available prototyping processes, and if you’re looking for features in microns and tolerances in microns, 3-D printing hasn’t quite gotten there yet. We’re hopeful that someday it will because it’s a complementary technology, to help those that are designing new products to have faster ways to work through research and development. 3-D printing doesn’t necessarily give you a manufacturable process or a production-like material or process in a lot of cases. There are definitely some distinct advantages and we’re watching the 3-D market advance. But pretty much anything that we micro-mold, they would no-quote. I mean, we have one part that’s only 800 microns long and has features that are smaller than that. 3-D printing is a fabulous technology that can do a lot of great things and has a great application, but just like anything else, it has its limits.”
“The trend toward miniaturization due to the rise of minimally invasive procedures requires smaller products, tolerances, wall thicknesses and an increasing demand to show process capabilities that can control the production of such complex parts,” added Gall. Raumedic also specializes in micro-molded parts. “Such demands are answered by Raumedic with the investment in specialty micro-molding equipment/molding presses. The size of micro-molded parts is in the range of one single pellet, working with part weights down to 0.004 grams. Besides standard thermoplastics such as PE (polyethylene), PA (nylon), PC (polycarbonate) and PUR (polyurethane), high temperature thermoplastics such as PEEK, PSU and PPSU (polyphenylsulfone) can also be used for this specialized molding process. Again different molding processes can be combined, e.g., by overmolding a micro-molded atraumatic tip on an extruded PEEK guide catheter used in cardiovascular applications. The challenge is that micro-molded parts have many of the same features as traditional molded parts, such as gates, ventings, knit lines and parting lines. Micro-molded components must be qualified and validated like any traditional component. This requires accurate measurement and demonstrated repeatability while working on the miniature level, with parts so small that their features are hardly visible to the naked eye. Special jigs, fixtures, measurement devices but foremost well-trained operators are needed to qualify such components.”