Medical Device Link.

Originally Published MDDI January 2002

PACKAGING

Thermoform-fill-seal technology incorporates a wide range of variables that offer manufacturers flexibility in the design and modification of every area in the packaging process.

Wil Caraballo

With thermoform-fill-seal technology, a variety of films can be combined to yield flexible or semirigid packages. Photo courtesy of Multivac Inc.

When compared with other packaging technologies, thermoform-fill-seal (TFS) packaging technology offers manufacturers considerable opportunity for innovation. A wide range of three-dimensional (3-D) shapes and several different films can be combined to yield a variety of flexible or semirigid packages.

Packaging equipment can be designed and engineered to meet specific medical packaging needs and existing equipment is easily modified to accommodate different sets of variables or to add features. The technology streamlines production, resulting in productivity increases and significant cost savings.

CUSTOMIZATION

The key to the flexibility of TFS technology is that its two sets of tooling, forming and sealing, are customized to the requirements of the package. The design process begins with the creation of a 3-D package around the product, taking into consideration both the product configuration and the desired level of content protection.

Once the shape and nature of the package are established, the layout of the tooling is designed around the package, taking into account package size, the number of packages to be produced per index, the type of seal (fusion-welded or peelable), and the type of cutting used as packages are separated from the webs. The machine is then designed around the tooling. The final design step selects accessories, such as those for printing or affixing labels.

THE PROCESS

The basic idea behind the forming method is to take a flat, continuous piece of film in roll form (rollstock), heat a section of it, then draw it into a 3-D shape. Forming machines run from two webs of film: the thermoforming or bottom web that creates the 3-D shape of the package or tray, and the top web that places a lid of Tyvek, foil, paper, or other material on the formed, filled cavity. This technology takes a modular approach. The packaging material travels through several stations of the forming machine that convert it from rollstock into complete, filled, and sealed packages.

Film Unwind and Feed. In this first part of the process, a module unwinds and feeds film rollstock into the machine. Manufacturers offer a number of unwind systems to accommodate different ranges of material. As film is unwound, it is fed into gripper chains, which hold it firmly on both sides throughout the form-fill-seal (FFS) process, keeping it flat and taut.

Heating and Forming. Next, the film enters a forming area where heat softens it. All films, with the exception of special multilayer aluminum films, can be formed under the influence of heat—hence the term thermoforming.

Heating station configurations vary depending on the film used and the desired cycle speeds. The heating process may occur inside the forming die or immediately preceding it. Also in the forming area, vacuum or compressed air pulls or presses the film onto the die.

There are three basic types of thermoforming technology: negative, negative plug-assist, and positive. Inside the forming die, heated film can be negatively formed by pulling it into a concave-shaped mold, or it can be positively formed around a convex-shaped plug. In negative forming, depending on the package design and the material being used, it may be necessary to prestretch the film mechanically before pulling it into the negative mold. This is done with a plug, which redistributes the packaging material so that the vital corners and bottom edges remain relatively thick while ensuring consistent distribution in other areas.

The positive forming method is used only for rigid films. It offers three major advantages: it allows precise control of the thickness of the package wall, permits the forming of detailed shapes on the package’s bottom and side walls (e.g., company logos, support ribbing), and makes it possible to form packages with small radius corners from relatively thin and, therefore, inexpensive films.

Filling. The machine’s next module is called the filling or loading area. Here, either employees fill the formed package pockets manually, or a variety of automated counting, portioning, filling, and weighing devices perform the task. Vibratory loaders, bowl feeders, loaders, pick-and-place units, and robotic systems are some of the systems available. Machine manufacturers also offer various machine configuration options such as knee-free loading stations that allow operators to sit during manual product loading.

Sealing. Once product has been loaded into the packages, the lower and upper webs move into the sealing die. At this point in cases of flexible packages, air is evacuated out of the die to displace oxygen or moisture, and, if desired, various gases can be back-flushed into the packages. Following this evacuation step, heat and pressure seal the upper and lower webs.

In the case of nonpermeable top webs, this process forms air-tight, hermetically sealed packages. When paper or Tyvek top webs are used, the package is impermeable to microbes but breathable for gas sterilization. The pressure and temperature involved can be precisely controlled and monitored to best affect the materials used.

Also during the sealing step, a steam-shrink system eliminates unsightly package wrinkles before they have a chance to form by injecting a measured amount of superheated steam into the die. This happens after the top and bottom webs have been sealed and just before the die is vented to the outside atmosphere.

Some package designs, particularly those incorporating centrally located flanges or reclosable lids, require forming of the top web in addition to the bottom web. To do so, another forming station is positioned between the machine’s loading area and its sealing die. Both negative and positive forming methods are applicable to top forming of flexible and rigid materials.

Separation. In the separation phase of the process, several types of cross-machine and machine-direction cutting are used, depending on the package shape and materials. The one overriding criteria is that the cutting be virtually particle free. In the package separation process, a crosscutting unit typically separates the packages across the web (latitudinally), while a longitudinal cutting unit cuts them lengthwise before discharging them from the machine. These cutting systems also incorporate package features such as tear notches, hanger holes, extended headers, thumbhole notches, corner rounding, or perforations. In some cases a blanking press is used to stamp out entire arrays of packages with a single stroke of matched metal cutting tools.

Printing and Labeling. Optionally, machines can also be engineered to incorporate printing, code dating, and labeling equipment. As part of the on-line process, machines affix labels or print on the lid stock or the filled tray. Printing options include simple cold stamp–type printers, sophisticated flexographic printers, thermal-transfer printers, and ink-jet printers.

Control Systems. Forming machines are equipped with microprocessor control systems. With a basic PC system, operators make adjustments using a menu-driven set of screens on the display. More-advanced operator interfaces use touch screen potentiometers on the front control panel of the machine to set functions and parameters within the FFS process, such as sealing time and temperature, vacuum level, forming time and temperature, gassing pressure, etc. The PC also provides self-diagnostics to display problems.

With a more-sophisticated microprocessor system, the software controls the activation order of each machine’s distinct functions. Because the order is not fixed by relays and computer wiring, each machine function is programmable within the overall sequence.

OPTIONS

TFS technology incorporates a wide range of variables that allow for considerable flexibility in the initial design and later modification of nearly every area of the packaging process.

Customization. Although TFS packaging machines are manufactured on an assembly-line basis using standard components, each machine is designed and engineered to meet the individual company’s needs with regard to package shape, functionality, automation requirements, loading, and space constraints.

BD, a medical technology company headquartered in Franklin Lakes, NJ, uses three different models of forming machines to package products at its Sandy, UT, division headquarters. Robert Stanley of the Sandy facility explains, "One of the machines packages our scrub brushes, for example, and we’ve ordered two more for the same purpose. Five other machines package various types of catheters. Two of these machines have four different dies each to produce a variety of packages."

Instead of buying individual trays from an outside source, bringing them in, storing them, filling them manually, sealing them, and then sending them out for sterilization, the company simply buys the raw materials and manufactures and fills the trays in-house. "Since the material won’t be handled as much in the forming process, we’re able to use thinner film, which is more cost-effective," Stanley says. "We also eliminate the need for two employees to run the packages through a shuttle filler. One machine can produce five different packages filled with different products. This involves quite a few die changes, but it’s still more cost-effective than purchasing all the trays from outside sources."

Package Shapes. The current technology accommodates an extremely broad range of shapes, both flexible and semirigid. Shapes range from square packages to octagons to cone shapes, or from a deep tray for holding a surgery drape to a shallow tray for a single needle. Packages can incorporate special opening features such as lids with punched holes that can be easily peeled off by mobility-impaired end-users.

Medrad (Indianola, PA), a company that provides medical devices and services that enable and enhance imaging procedures, uses a number of FFS machines to package large, sterile, disposable syringes used in diagnostic imaging procedures. The packages are formed from polystyrene and have a Tyvek lid.

Thomas Beals, Medrad’s engineering manager, believes that FFS technology gives his company better control over the process, which translates to higher-quality packages. Another benefit, he says, is that the FFS process provides a cleaner product, which is important in the medical device arena. "The process also gives us the ability to produce new package designs in-house," Beals says. "It makes us less dependent on an outside supplier."

Film Choices. TFS technology works with any type of thermoformable and heat-sealable film, from flexible polyethylene-type products to tough nylon structures to semirigid styrene, PVC, PP, or PETG resins for trays that must maintain geometric stability. In many situations, the same forming tooling can handle both flexible and semirigid film. For lids, the top web accommodates every type of film material from paper to foil.

Safety 1st in Santa Ana, CA, owns multiple machines in multiple locations to package its safety syringes. "One machine makes packages in several different sizes to accommodate our variously sized syringes," says Craig Wilhelm, president. "The bottom web is nylon and the top web is 20-lb paper with polyethylene laminated to it."

In another setup, Bob Taylor, vice president of Aspen Surgical Products Inc. (Grand Rapids, MI), uses Surlyn flexible film for soft pouches and PETG rigid film for blisters. "For covers we primarily run 1059B Tyvek, which is Tyvek paper with an adhesive coating," he says.

New, more-economical packaging materials are always becoming available. These films, while retaining the required strength and puncture resistance, make die changeovers easier, are less expensive, and are light in weight to save money on shipping costs. Unlike other, less-flexible technologies that do not easily adapt to the new structures, TFS technology accepts each new film with only minor modifications.

Adaptability. There is no limit to the type or number of items that can be held in formed packages, from individual needles to bulk pipettes. Properly formed containers that fit the product provides maximal protection against moisture, oxygen, or light. Special features of the packages can make them more user-friendly and immobilize products to prevent damage.

The technology also easily adapts to the new disposable products, such as safety syringes, that seemingly enter the market almost daily. Modifying tooling to accommodate a new product is easy and inexpensive.

The technology can also be adopted quickly to changing sterilization needs. "While most of our products are sterilized with EtO and require a breathable Tyvek or paper cover," Stanley says, "[one of our] new products will be gamma sterilized or E-beam sterilized, which makes a film-to-film package the most appropriate option."

Flexibility. Because of the technology’s inherent versatility, a single machine can handle a wide range of packages. Some companies package hundreds of catalog items on a single machine. A quick removal of only two bolts, for example, changes plates to produce packages of a completely different configuration. In the sealing module, seal grids can be snapped in and out of the sealing-grid die to change the shape of the package seal. A simple changeover from running 10 packages of a certain size to 20 of a different size can be accomplished in 15 minutes. Even when multiple tooling sets are required to change mold shape and package size, a changeover can take as little as half an hour.

For Safety 1st, a changeover from one package size to another, which involves changing the forming and sealing tools, takes about 40 minutes. This translates to minimal downtime, according to Taylor.

"We’re running three different product groups that require different tooling," he says. "The tooling, forming, and sealing dies allow quick changes."

Printing options add extra flexibility. Medrad purchases Tyvek that is not preprinted. "We print all the standard and variable label information [ourselves]," says Beals. "It gives us greater flexibility and saves time because we’re not changing and stocking and restocking printed Tyvek."

The packaging process at Safety 1st incorporates a Bell-Mark flexographic printer, which permits two-color graphic printing in the on-line process, as well as a video-jet printer. "The benefit of having two different printers is that we can easily change the printing for different products. We don’t have to have an inventory of preprinted labels or vast amounts of rollstock in storage," says Wilhelm.

Modular Designs Permit Modification. In the process of designing the tooling layout, the company selects the desired machine width depending on the number of package components. Equipment can be easily modified to accommodate different sets of variables or to add features later. The modular nature of the equipment lends itself to making even drastic changes efficiently. For example, the machine’s modular design brings versatility in the loading area. By simply removing modular sections, a long machine incorporating loading space for 10 employees can be shortened quickly for automatic loading. Alternatively, a midsize loading module permits both automatic loading under the supervision of an operator and manual loading for items such as tubing that must be wrapped and placed manually.

Variable Machine Speed. Machine speed is almost infinitely variable, from a very slow speed for hand loading to 30 or more cycles per minute in automated processes. Manufacturers modify the speed of the machine depending on the characteristics of the product that is going through the line, the volume of product, and the number of people loading. "With the faster, more highly automated machine we just purchased for our catheters, we’re saving $600,000 a year per line," says Stanley. "The savings are primarily in labor, but also in efficiencies on the machines. Instead of producing about 50,000 units a day, we’re now making up to 70,000 units."

Microprocessor Controls. Microprocessors control other variables and settings, such as temperature. Operators can use a touch screen to raise or lower the temperature and to set alarms to warn of malfunctions that may affect the temperature. Manufacturers also use microprocessors to maintain consistent settings for temperature, vacuum, speed, and other process variables.

Space Savings. Among the features of a versatile forming machine is a system that can draw a slight vacuum over flexible packages. This vacuum not only holds products in place, it also compacts the package size, reducing the amount of space they take up in cartons. Less space means lower shipping costs.

Information Processing. An additional benefit inherent in the technology’s high level of automation is the ability to monitor and record information during processing. Control systems can be programmed to monitor the machine and to extract and store data from the microprocessor at any interval—once an hour, once a minute, 10 times per second, etc. That includes FDA-required validation data or any type of user-specific information, such as sealing temperature. Controls are user-friendly, so facility engineers can reprogram them as necessary. Control systems also offer traceability in case of failures, providing information on a package-by-package basis.

In the medical device arena, process validation is a critical consideration. "Some FFS equipment manufacturers now offer separate validation packages (software and hardware) that can be integrated within their technology to facilitate package and process validation," says Donald S. Barcan, president of Donbar Industries (Long Valley, NJ) and co-author of the ISO standard 11607, which covers the requirements for the packaging of terminally sterilized medical devices. FDA has adopted this standard as a consensus standard. Barcan recommends that companies contemplating the purchase of FFS equipment seriously consider adding the validation option. It should include separate sensors and data acquisition systems to monitor the equipment and shut down the process if it exceeds preset limits.

Companies considering the purchase of a machine should ensure that its technology can be integrated with other systems. Says BD’s Stanley, "We use video jets in combination with our machines to print the lot number, expiration date, and pallet number. The company that manufactured the TFS machine took care of the integration."

Package shaping and sealing methods; diverse packaging materials; cutting, printing, and labeling modules; and a range of customization options make for almost infinite permutations and combinations that result in freedom in package design. This makes the technology ideal for an industry that produces the widest possible range of product shapes, sizes, and configurations.

LIMITATIONS

TFS technology dates back to the mid-1960s. After decades of evolution, it has reached a highly sophisticated state. Nevertheless, there are some limitations. One problem concerns the shape of the forming tool. Because the package has to be removable from the tooling, the tool cannot have any shape that would trap the package inside the cavity or on the exterior shape of the plug once it is formed. There are exceptions, of course, so it’s best to explore the options with a manufacturer of forming equipment.

In addition, film selection is limited by the desired outcome. In the TFS process, a flat piece of film is shaped into a 3-D package that has the same footprint as the original flat piece of film. This means that the film is now stretched over a larger area, making it considerably thinner. It is therefore critical to select the proper thickness of the film, taking into consideration the required minimum strength of the finished package.
In some cases of unusual product shapes, some scrap material may need to be discarded and designed into packaging costs. However, any additional costs may be made up by using the same mold to package other products. If the result is a more attractive and user-friendly package, additional sales are likely to offset for any losses.

In fact, in the entire process, product presentation is an important consideration. Why not replace a poorly fitting pouch with a shaped tray designed around the product, integrating attractive graphics, and incorporating easy-to-open features? A more professional presentation of a user-friendly package can make smaller companies’ products more competitive and give them needed exposure.

Because the applications of TFS technology are almost unlimited, it’s important to be clear on the company’s particular goals. Medrad engineering manager Beals’s advice to companies considering the purchase of a forming machine is to establish their packaging requirements and determine how the package will interact with the product. "Many companies make good machines," he says. "What differentiates them is whether they’re able to help you make good packages. You have to know how your package needs to perform. It comes down to package design."

COST

Device manufacturers considering the purchase of a TFS packaging machine need the volume to justify the expense. "Companies with low volume often purchase premade packages and precut lids," says Beals. "With sufficiently high volume, TFS technology is probably the most cost-effective way to produce packages, because you purchase raw material and process it all at once. It takes cost out of the product and simplifies your supply chain."

The minimum investment by a manufacturer in TFS technology is typically around $100,000, although systems can be designed for as little as $75,000. Fortunately, purchasers can expect substantial savings on materials and labor. Producing packages from materials in roll form is much less expensive than purchasing preformed trays and precut lids and sealing them on a tray sealer. Packages made on forming machines typically save 50–75% of the packaging material costs and 50–70% of the labor costs for loading and sealing. Payback is frequently 3 to 12 months, with internal rates of return at 100% or more. Beyond the basic numbers, the investment can also bring a significant increase in productivity, not to mention additional sales of the more user-friendly packages.

"The FFS equipment has greatly enhanced our business capability," says Aspen’s Taylor. "It offers much greater latitude than I had expected and it’s cost-effective. We’ve been able to drive a lot of cost out of our products. In addition, it’s helped us to better position our products in the marketplace by convincing our customers that we’re a low-cost, high-quality provider."

CONCLUSION

Although the initial investment may be considerable, the benefits of the TFS technology outweigh any cost considerations. Even smaller companies in the medical device and diagnostic industry still using traditional packaging methods would do well to consider this option. The flexibility, versatility, and efficiency of the process, along with the need to adapt packaging methods to new products and films, make the technology a necessity for companies that want to remain competitive.

Wil Caraballo is technical manager of the medical division at Multivac Inc. (Kansas City, MO).

Copyright ©2002 Medical Device & Diagnostic Industry