A Tube for All Occasions

A Tube for All Occasions

Tighter Tolerances Are Key to Development Of Minimally Invasive Medical Devices

By Ed Kensik – Associate Editor

Despite demand for tighter tolerances, faster turnaround times and spiraling material costs, custom metal and plastic tubing suppliers and contract manufacturers are receiving high grades in sales as many are experiencing double-digit growth.

Many are looking for a continuing robust industry as OEMs build more minimally invasive surgical technology and advanced procedures that help baby boomers as they grow older.

Custom metal tubing manufacturers and suppliers receive inquiries for all different types of  tubing. Photo courtesy of MicroGroup.

Be it ID, OD or walls, the tolerances are getting tighter and tighter as OEMs continue to minimize the size of the patient’s entry wound for a procedure.

In addition, contract manufacturers and suppliers are facing increasing prices for oil and hydrogen, be it directly or indirectly.

“It’s a constant pressure of cost reductions and constant pressure to tighten tolerances,” said Richard Brooks, vice president of sales and marketing for Filtrona Extrusion. in  Northborough, MA. “As raw material costs continue to go up, you better get damn good at the manufacturing process and also pass through the appropriate price increases to your customers. You’ve got no choice. With raw materials such a large portion of our costs, you’ve got to eliminate the fat, whatever fat is left. Trim it, trim it, lean manufacturing, Six Sigma—the whole gamut of lean manufacturing principles.”

Not only have tubing contract manufacturers and suppliers seen double-digit revenue increases, some are reporting more than 20% or even 30% hikes in sales, and it should not end in the foreseeable future.

“We do continue to see growth because there are new projects, new products, and we see a good number of startup companies as well as larger companies going after development,” said Bob Lamson, marketing manager of MicroGroup in Medway, MA., a supplier of custom metal tubing.

Part of the key is sticking with the ever-changing direction of the medical device industry.

“If you follow the trends of the engineers, you will be there in time to make some money,” said Bob Poirer, vice president of sales at Manchester, NH-based Dunn Industries, a maker of plastic tubing. “The market is growing with the aging population and the new procedures that they are coming up with.”

OEMs are asking plastic tube contract manufacturers and suppliers for thinner diameters used in more minimally invasive procedures. Photo courtesy of Zeus.

To stay current with the industry, tubing suppliers and contract manufacturers need to decrease the turnaround time for OEMs who are trying to beat their competitors to the market.

“If the company doesn’t meet its window of opportunity, its product is scrapped,” said Poirer. “It’s a timeframe to get the development of the extrusion into the engineer’s hands so they can fabricate their device and get it through the FDA and into the market place as soon as possible.”

Part of helping that turnaround time is offering as many services under one roof as possible. Krissi Heard, technical sales of Tampa, FL-based MicroLumen, said that the supplier of plastic tubing offers sub-assembly, precision trimming, marker band implantation and integrating flexible tips into the tube shaft. She added that MicroLumen also offers kanban stock holding and dock-to-stock programs.

Sean Lynn, associate director of extrusion R&D for Research Triangle, NC-based Teleflex, a plastic tube maker, said many OEMs demand bonded stem sections, a traumatic tip, embedded marker bands and coil sections.    

“I genuinely think that to compete effectively in today’s extrusion market, a broad portfolio of technologies and capabilities are required,” said Lynn. “Client companies are more interested in dealing with suppliers that can meet a broader range of their requirements. Sometimes a client company is looking for more than just an extrusion.”

Outsourcing Trends

More and more OEMs are discovering the only way to go for their tubing is to go through one of the contract manufacturers or the suppliers.

“First, since we perform the finishing procedures for a number of customers, we are able to leverage economies of scale and invest in automation equipment that is not economically feasible for our customers at their usage volumes,” said Karl Graffte, director of marketing for Orangeburg, SC-based Zeus, a plastic tubing supplier.

“Second, the customers are ensured 100% yields. When they open the package, they get all usable parts. If they purchase tubes and perform the procedures themselves, there will be some waste and scrap.”

Going along with outsourcing is the need for contract manufacturers to be involved earlier in the process, especially in the design stage of the medical device. Working with OEMs earlier in the design process gives them more options to use either standard sizes or specialized tubing that could take longer to produce.

“This is increasingly the case both when we are supplying the device and when we are supplying the actual extrusions. This is a positive development over the last few years as bringing in an OEM partner at the very early stages of the design is critical,” said Lynn, who added that more OEMs today are adopting partnership models with contract manufacturers.

Tighter Tolerances

Year after year, tolerances continue to get smaller and smaller. Although some companies are trying to make walls, IDs and ODs smaller, contract manufacturers need to put some caution into the clients who are looking to go even smaller.

“There is a point where the trade offs between the expense of manufacturing of the product versus the obtained attributes of the finished tube is kind of a trade off,” said Jeff Warden, vice president of business development at Superior Tubing of Collegeville, PA. He added that the company’s tolerance for custom metal tubing can go as low as ± .002 inch for walls and as small as ± .028 inch OD with the smallest ID being ± .020 inch.

And Brooks agrees that there is a point where you can’t go thinner, at least right now. “It is a dichotomy because what happens if you go too thin on the wall, it could kink,” said Brooks. “That is the worst possible nightmare of any tube because if you have a kink, it will stop fluids from moving, air from moving. The patient does not get a consistent flow. It can’t get any worse than that.”

Poirer, though, said that there have been ways in the past and there will always be ways in the future. “Looking at it and you say, ‘Yeah, you can’t go any smaller,’ but somebody always finds a way,” said Poirer.

Makers of catheters and stents are continually reducing the sizes as they try to minimize the size of the patient’s entry wound from the procedure. Lynn added that the size of the entry wound directly affects the length of the hospital stay for a patient.

“In broad terms, these developments mean that the challenge for tubing manufacturers is to do more with less,” said Lynn. “There is a lot less margin for error in many areas of extrusion now than in the past.”

And Graffte said that it has become more and more evident that medical device engineers are trying to do more with less. “What I mean by this is they want to be able to perform multiple procedures or put more devices down the same tube,” said Graffte. “For that reason, they are continually pushing to extrude thinner walls and tighter tolerances.”

To satisfy the ever increasing demands of OEMs, contract manufactuers of plastic and metal tubing are offering various services including laser cutting, soldering, brasing, flaring, flanging and custom cutting. Photo courtesy of Peridot Corp.

He added that there is the continuing use of  “tolerance stacking,” where three tubes have an OD tolerance of ± .002 inch and each is at the top of the tolerance range. The overall finished OD size of the catheter could be ± .006 inch larger.

Brian Martin, marketing segment manager of the orthopedic products group at Handy and Harman Tube Company in Norristown, PA, said the advancement of industry machinery has accelerated the tolerance requirements.

“The Swiss centers are very accurate and it turns back to the raw material vendor the need to manufacture a raw material product to very exacting standard,” said Martin. “Specifications are getting very, very tight with very small sizes, and we are going to continue to see that. It happened in the stent industry.”

Materials Use

Stainless steel and titanium are mostly used in custom metal tubing while PVC, polyurethane and fluropolymers are still the materials of choice for plastic tubing.

But the increasing advancements in medical devices are helping to push some of the exotic materials into the forefront. For custom metals, stainless steel still is the most popular and least expensive material of choice, but that is changing.

“It’s always cheaper to go with 300 stainless steel tubing,” said Patrick Pickerell, president of Pleasanton, CA-based Peridot. “We always make sure that when we work with clients on designing products that they explore the issue of cost options first before they push the more exotic products. The exotics are really coming into favor, and those people who ignore that will be left in the dust.”

But many times it comes down to which applications contract manufacturers specialize in, like titanium, for instance.

“It is the biggest, hottest sexiest thing in the orthopedic industry right now,” said Handy and Harmon’s Martin, who added that the material is 40% lighter and 30% stronger than its competitors.  “It has no nickel so it has biocompatibility. Its high acceptability to the human body is excellent. It is highly corrosive resistant. It is the implant maker’s alloy of choice.”

Martin added that demand for the material combined with supply scarcity has caused the price of titanium to skyrocket. In 2002, the cost for titanium sponge was $4 to $6 a pound, but now it is between $33 and $38 a pound.

“In their development, the companies try to work around titanium if they can, but a lot of them already have titanium in place,” said Martin. “Through certification and what they have to do to get an implant device into the field and due to FDA regulations, it is not an overnight turn to take the product out of the mix and replace it with something else. You are married to titanium for a while, particularly in what you have seen that has transpired in that market and how so many products in the portfolio have transitioned into primarily titanium products.”

But for many contract manufacturers who specialize in custom metal tubing, it is still 300 series stainless steel that makes up the lion’s share of their volume. “The reasons for that are, one, availability and, two, price that tend to drive people’s applications unless something or unique comes up,” said Lamson.

In addition to stainless steel and titanium, demand in metal tubing also includes nitinol and other alloys.

Plastic Developments

In terms of plastic, PVC still offers a strong and cost-effective solution, but other materials are continuing to grow within the industry.

“PVC without a doubt was, is and will be,” said Brooks. “It’s not going to change. It’s too cost effective. Its characteristics lend it to just so many diverse areas that there’s just nothing out there with comparable cost that can do it.”

One of the many services that custom plastic tubing providers offer is PTFE and FEP heat shrink tubing. Photo courtesy of Teleflex Medical.

The question also comes up about the toxicity of DEHP, the compound used as a plasticizer in many products made out of PVC. On its website, the FDA states that there have been no human studies showing the same adverse effects that animal tests have shown, but the agency does recommend against using the compound in some applications.

But Brooks defended the use of PVC: “There has never been a reported injury, sickness, death from PVC or phthalate absorption in a human being; never, zero.”

Poirer, though, said that his customers have been distancing themselves from PVC, choosing instead materials such as Pebax and polyurethanes because of the outgassing of chlorine when burning the material.

He added that PVC costs between $1 and $1.50 per pound and urethane could cost from $6 to $50 per pound for use in a long-term implantable device.

According to Heard, polyimide is MicroLumen’s primary plastic used for devices requiring superior mechanical, thermal and chemical properties.  Polyimide is flexible, kink-resistant and has excellent torque ratios. Other popular plastics are fluoropolymers (PTFE and FEP), Pebax and other nylons. 

Plastic Versus Metal   

While many said that the two sectors do not meet and have thrived separately, Warden, said that there is some conversion between the two.

“Plastics are always a threat,” said Warden, whose company is a contract manufacturer of custom metal tubing. “When they do it with plastics, it is always a lot cheaper, but the attributes, stiffness, strength and so forth that you can’t get with plastics and you can get with metal. Radiopacity is another key factor.”

The best characteristic that OEMs want from plastic is flexibility, especially in ventilator tubes and catheters, while metal tubing is needed for devices requiring precise tolerances.

But Graffte gave the plastic side of the debate.

“PEEK is an excellent replacement for stainless steel and other metals,” he said, adding that the material is used in many medical applications. He pointed out that one example was a customer who replaced PEEK tubing with stainless steel, and the result was that it created plenty of friction, causing heat to build up. “PEEK is chemically inert and replaced stainless steel years ago as the tube of choice as it does not leach anything into the sample being tested.”

Poirer noted that “You can’t flex a metal tube like you can flex a plastic tube, and then you can’t make the plastic tube as stiff as a piece of metal.”

But no matter whether it is plastic or metal tubing, suppliers and contract manufacturers continue to thrive and meet the challenges that are thrown at them by OEMs.