Plastics Flow into the Medical Device Industry
A look at materials and applications in the field with EVCO Plastics’ Michael Kvalo
By Michael C. Anderson
Although the North American medical device industry continues to grow, its players are under an extraordinary number of constraints. FDA requirements top the list, of course, controlling what, how, and from what materials a device can be made. On top of that are cost pressures brought on by international competition, safety and sustainability concerns, and, finally, manufacturability issues. This is not a field for the timid.
At the same time, those pressures are an incubator from which exciting new products, processes and materials are emerging. Last year, we focused on metals used in the industry (“Living in the Materials World” in our May 2013 issue). This year, to get a line on how device makers are using new developments in plastics, ME Media turned to Michael L. Kvalo of EVCO Plastics (DeForest, WI), who walked us through how new, better plastics are making an impact in the industry.
Kvalo’s title is Project Engineering Manager at EVCO; he’s been with the company for 21 years, following six years in medical-device R&D at Johnson & Johnson and stints at Pfizer and other companies. “My passion is product development,” Kvalo said. That passion was evident when he described materials that are replacing lead and PVC as well as the advances in injection molding that are making such materials viable in the marketplace.
“We touch and feel plastic parts all day, from all industry sectors—from parts that run on our 3500-ton press in Oshkosh to tiny parts that run in our clean room—parts that may only weigh one or two grams. We see the full spectrum and work with all kinds of plastic resins,” Kvalo said. New materials come to the company’s attention in three different ways. Every three years, a team of EVCO engineers attends the triennial K Plastics and Rubber Trade Show held in Germany as well as the triennial NPE Plastics Trade Show in Orlando, FL. Customers will also bring new materials to EVCO’s attention. The third resource for new materials is the company’s subscription to the IDES database, which includes over 40,000 plastics.
“We can search the database by properties—maybe its impact, maybe it’s a particular FDA DMF listing, or elongation or tensile strength,” Kvalo said. “We can narrow the search by specific grades or classifications of polymers. Customers find that [ability] very helpful because we can do side-by-side comparisons—maybe on a material they’re currently using versus a material we are proposing they use.”
For all of their sakes, EVCO likes to help their medical manufacturing clients with material selection as, he said, they often need help in that area. “Typically, they don’t have experience with as many resins as we do. We know what resins don’t run well, and typically the resins that we use a lot of are good performers. Another benefit is that when we are using a lot of a given material, we get a good price on it. We can save the client money in that way and get them a better material.
“The other thing we try to do—and it’s more difficult in the medical device field because of FDA-mandated safety and efficacy testing—is to qualify a backup material for the customer,” Kvalo said. The reason this is important points to a difference between working with plastics and working with metals: While a manufacturer can presumably get a needed grade of steel or titanium from more than one supplier, the custom-made formulations of plastics are proprietary—made by a single company and sometimes made only at a single facility. So if a fire or natural disaster cuts off access to that single source, the medical OEM can get burnt. It can take six months to get use of a different grade of material approved by the FDA. “So when a backup material can be qualified up front, it can save a lot of trouble later on,” Kvalo explained.
From Metal to Plastic
EVCO Plastics has been on the front lines of a trend in the industry to, when feasible, move from metals to plastics. There are a number of reasons that the latter can be a better choice. One of the most important of these is that working in plastics can simplify the manufacturing process, saving time and removing variables that can affect part quality.
“Generally speaking, when we’re talking about going from metal to plastic, we’re taking a metal assembly that may have multiple clips and snaps, and we’re able to mold all of those features onto one part. I can’t think of any situation offhand where we didn’t take a metal assembly of maybe a dozen parts and get the part count down to three or four or five,” Kvalo said. “That does multiple good things. It gets the cost down and it mistake-proofs the assembly for the OEM.
“You know, the tooling in injection molding is probably the most expensive tooling of any plastic process and technology—but if you make that investment, you end up with the lowest part cost. And you’re able to put a range of features in the mold that can replace what were separate parts or operations in a metal version of the product.”
Another advantage of plastic is cosmetic, Kvalo noted. “In many applications, plastic is going to stay newer-looking longer than steel. Steel corrodes; paint on steel scratches, but colored plastic is the same color all the way through.”
Get the Lead Out
Another strong impetus to move from metal to plastic is ecological: there are metals, such as lead, that can damage the user’s health and environment. Lead has been the go-to material for radiation shielding since the development of diagnostic X-ray, fluoroscopy and, more recently, CAT scanning. “There’s been a real push throughout the medical industry to get rid of lead,” Kvalo noted.
“We’re now making parts for some medical OEMs with a material called ‘ecomass,’ which can be alloyed with a polypropylene or a polycarbonate, depending on what the needed properties are. What makes ecomass special is that it has tungsten as a filler, giving the material a density close to that of lead. Tungsten is a nontoxic inorganic material, so the customer can get the necessary radiation-shielding properties in a material that can be injection-molded using fairly conventional injection molding equipment.
“Ecomass was originally marketed to the military as a replacement material for lead in bullets—consider the amount of lead that must be present in a military shooting range. It’s been available for less than 10 years, and it’s starting to catch on now in the medical field. The material is more expensive than lead, but the medical industry seems willing to bear that cost increase—the benefits are worth it,” Kvalo said.
Another material is moving into the medical realm from the world of plumbing—another industry that’s strived to get lead out of its products. It's a kind of brass substitute made with a PPS plastic alloyed with glass, mineral and graphite. “Well-wearing machinable brass generally has lead in it in order for it to achieve those properties,” Kvalo explained. The PPS alloy, like brass, is “very resistant to hot water, very resistant to massive fluctuations in temperature that you see in a plumbing situation, and it wears real well—parts made from it can last 20–30 years”—but doesn’t contain lead. EVCO is working with a customer to bring the material into the medical arena (and no, for the sake of customer confidentiality, he can’t name the company).
From Plastic to Plastic
If the industry’s move from metal to plastics bring pain to metal suppliers, they can take comfort from knowing that they’re not alone: a range of plastics too are being replaced by new and better formulations, and often for the same reason: the new stuff is either more cost-effective or safer than what it replaces. The poster child for a plastic that is being shown the exit in many medical applications is PVC.
“When I started in medical device R&D 30 years ago, PVC was pretty much ubiquitous in the industry, used in tubing, in shunts, drains, and all kinds of devices,” Kvalo remembered. But, as has been widely reported in recent years, PVC has toxicity concerns—not only for patients but also to the environment at large. “When it is incinerated—and incineration is a preferred way for hospitals to dispose of medical waste—PVC emits chlorine gas.” Chlorine gas—the scourge of the battlefields of Europe in WWI.
“PVC is probably one of the cheapest thermoplastics available today—still is. But because of these concerns, we’ve been trying to steer customers [in all industries] away from it. If a customer comes to us requesting to have something made from PVC, we’ll want to talk to them about it,” Kvalo said. “There might be some better materials that cost a little bit more but that won’t lead to the problems that can come with PVC use.”
The ‘End-of-Life’ Discussion
Mike Kvalo understands what some in the industry are still coming to grips with, namely that in medical, as in other industries, sustainability concerns are not going away.
“In our initial quality planning meetings with a customer, long before we cut any steel for a new mold, we talk about ‘end-of-life’ considerations for the product,” Kvalo said. “We ask, ‘How are you going to recycle this? How are you going to dispose of it?’ Questions like that, just to get the conversation going. Of course, our customers are concerned about the environment, and they’re concerned about safety, too. So we have these questions on our checklist and make sure these issues are raised up front.”
Finding the right substitute for PVC depends on how the product is used. “This is where we’ve really got to apply intelligence,” Kvalo said. “What does this thing have to do? What kind of temperature range will it see? What kind of chemicals will it be exposed to? Does it need to be clear or is it light-
opaque? What’s the expected life? Is it a single-use disposable device?
“When someone comes to me and says they want to make a single-use medical device, probably the first question I’m going to ask is, 'Is it going to be sterilized?' If the answer is ‘yes,’ then my next question would be, ‘Can you use polyethylene?’ Polyethylene is cheap, readily available, nontoxic, and easily recyclable—it’s the same stuff that milk jugs are made out of now. And polyethylene is naturally resistant to gamma radiation, so it’s not going to get brittle and yellow when you radiation-sterilize it. I’ll try to get the customer to look at it as a material choice.
“If they have a reason that polyethylene can’t be used for the product, then we start going down the list of materials with similar desirable properties— ‘How about polypropylene,’ I might ask. It’s a harder material, more temperature resistant. We know that part cost is important—that’s just a given today—so we try to recommend materials and manufacturing methods that are going to be cost-effective for the client.
“Another question we’ll ask is ‘What do you think your annual volume is going to be on this part? What is it going to start at and what do you think it will mature at?’ The answers will help us decide on what kind of tooling and automation will have to go along with this program too.”
Mold Flow Analysis
With advances in materials come advances in the manufacturing process. An example of a process that EVCO Plastics uses now that the company didn’t—at least not regularly—in past years is “a full mold flow analysis for every new mold we build,” Kvalo said. “We look at whether a part is going to warp, a particular problem with larger parts.
“The current state of the art in mold flow analysis and predicting warp is that we—the industry, the science—can’t predict it quantitatively very accurately yet. But we can predict it qualitatively; we know which direction it’s going to go. And once we know that, we can suggest design modifications to try and mitigate it, to minimize the amount of warp, or maybe get it to go in a different direction, one that’s not going to cause problems for the OEM.
“That’s something relatively new that we do 100% of the time now. We have the software in-house—we use the Autodesk Moldflow program," Kvalo said. "We’ve used it for a number of years. We’re just routinely doing more of it now.” ME
This article was first published in the May 2014 edition of Manufacturing Engineering magazine. Click here for PDF.
Published Date : 5/1/2014