Look before You Leap into a Tray
Before deciding upon a particular tray design, packaging engineers should work closely with suppliers and end-users to ensure the tray's user-friendliness and production efficiency.
Today's medical devices need trays of all shapes, sizes, thicknesses, and configurations. Procedural kits, implants, surgical supplies, and diagnostic products all need the room and rigidity of a tray. However, each product has its own requirements, so packaging engineers must carefully consider the individual needs of each. Otherwise, engineers are left with an inadequate package or an inefficient production process, resulting in lost time and money. In many cases, working with suppliers from the earliest stages of the project helps to avoid any such catastrophes.
TO THERMOFORM OR INJECTION MOLD?
One of the very first decisions to make is whether to produce the trays by thermoforming or by injection molding. Thermoforming is by far the most common practice for producing medical trays, but some devices have special requirements that make an injection-molded tray necessary.
The main reason device manufacturers choose thermoforming is cost. Because of the expense of the mold and the tooling in an injection molding operation, start-up costs for such a project can run 10 times more than those for thermoforming, suppliers say.
"A sophisticated tool for injection molding can cost more than $100,000," says Jim O'Dierno, senior vice president of sales at Prent Corp. (Jamesville, WI). "Injection molding is primarily dictated by customers' design requirements and is generally associated with extremely high volume. In the medical packaging market, the numbers are typically not there to justify the high capital tooling investment. As a result, thermoforming and pressure forming offer a number of beneficial options to accommodate initial development through full production needs."
Another priority in the medical field is speed. Thermoforming is therefore preferred because tool lead times are shorter than those for injection molding. "Thermoforming accommodates changes quite easily and offers more flexibility," he says. "In addition, part thickness limitations exist in injection molding that may affect optimal use of the raw materials involved."
Consequently, many device makers stick with thermoforming. Sarah Gabler, senior package engineer for device manufacturer Medtronic Inc. (Minneapolis), says that her firm uses thermoforming, "and it has not been worth it to look at other options."
Another reason thermoforming seems to be preferred is that "most designs aren't so sophisticated that they necessitate an injection molding operation," says Patrick Welch, vice president of medical sales for Barger Packaging, a division of Welch Packaging Group (Elkhart, IN).
However, there are some devices that do need the special capabilities of injection molding. "If the tray needs to be durable because it will be reused, or if it needs hinges or a certain thickness to help prevent light penetration," then injection molding is the choice, says Marty Shampoe, project manager for Erie Plastics Corp. (Corry, PA). "Maybe there is a feature that calls for it. If there is a locking feature or something you need to activate to get the device out, a thermoformed tray would not have the rigidity you'd need. The more the complexity, the more that dictates injection molding. For a lot of companies, cost is important, but if they have guidelines to meet, then they seem less reluctant to spend the money."
Indeed, although Prent is a thermoformer, it is considering beginning an injection molding operation "as an extension of future requirements," O'Dierno says. "As demands on thermoformers have increased, we have had to become more progressive in keeping thermoforming capabilities on the cutting edge, and we're getting closer to what injection molding can sometimes offer. However, injection molding may end up being a complementary capability for us."
Welch notes that some designs incorporate both thermoforming and injection molding. "These might have an injection-molded insert into a thermoformed tray, with the injection-molded part being a very small part of the package," he explains. "That's usually a use of last resort because of the expense. We did it when we had to help immobilize a product that was acting like a projectile, and the only way to stop it from moving around was to create a modular insert. It was very strong, and it contained the part very well. But you can only do that with a company that has the budget to pull it off."
Alloyd Company, Inc. (DeKalb, IL), offers pressure forming as an alternative for trays that need a heavier gauge than that yielded by conventional thermoforming but don't require injection molding. "If there are undercuts or a snapping function, we recommend pressure forming," says Keith Dirks, project engineer. "It depends on the gauge and the complexity of the tray. Anything that gets into the area of 0.040 to 0.045 in. is getting into pressure forming."
Regardless of whether a device packaging engineer has a preconceived tray design, it pays to be in constant communication with the tray supplier from the earliest conceptual stage.
"We play a key role in the design of the part," says Welch. "If a device maker needs a sterile package, we sit down with them and attempt to create a system including the tray, lidding, and carton that meets their needs, specifications, and timeline. Most importantly, we can ensure we've designed a producible package. If we are called in at the 11th hour because they just need someone to produce it, in many instances we are given an unproducible design. Then they have to modify it and spend more time and money. So we urge all firms to involve their design and manufacturing companies as early as possible to alleviate problems."
Dirks agrees. "Sometimes customers submit preliminary tray designs, and we often respond with recommendations to further improve the tray performance."
Particularly useful to a customer is when a supplier can provide a three-dimensional CAD rendering of a proposed tray before starting tooling manufacture, he says. "That allows us to address issues like product placement and orientation. The rendering also addresses the look and shape early, which may shorten design time and speed time to market. Customers may also want to specify the sealing flange configuration so as to conform to existing shapes already validated."
CAD renderings such as this one from Alloyd help firms finalize design before manufacture.
Other things to be considered during this process include user-friendliness and functionality, says Brian Meltzner, sales manager, Merrill's Packaging (Burlingame, CA). "You have to understand the customer's product. What it is, how it is to be used by the end-user, what environment it will be used in," he says. "Is the product intended to be loose in the package or locked in place? If you are working with a coiled product, we will need to know who will grab it, a sterile or nonsterile nurse? If it's a kit, what is taken out first? You want to design it as user-friendly as possible and think about how it will assist the user in product employment."
In addition, Meltzner says: "I counsel people to make sure they understand the distribution challenges. There are a lot of steps these products see. If you skimp on material, you may compromise the integrity of the package."
O'Dierno agrees. "You have to consider the handling of the tray and the order of use as well as stackability and warehouse issues," he says. "For example, as a value-added functional benefit, Prent Corp. has the ability to seal a drape planned to be sterile to the underside of a procedural tray. As a single unit, this concept eliminates the need for an independent packaged drape that must be unfolded separately to accommodate the sterile field. This facilitates handling ease and eliminates the need for an inner sealed tray."
Another design trend is to make trays that can be applicable to many different things. "We see more requests to put more instruments and implants into the same package, so we design trays that can accommodate 5 to 25 different parts," Welch says. "That is always a challenge in itself, but the payoff is one package for multiple parts and more quantity with just one design, and that lowers the overall manufacturing costs."
One more-frequent request, he says, is to use "plastic components for capture rather than foam. These are generated using thermoformed parts. Some of our customers like foamless packages because foam generates particulates and static electricity."
LOW COST OR BUST?
While cost is considered across the board as a major factor in tray design—some say it is prioritized to a fault—there are those who say it shouldn't be the first thing addressed.
"The most important thing is that when the package is in a sterile environment, you have to be able to get its contents into the sterile environment without compromising the integrity of the package," Gabler says. "The second-most important thing is that the vendor can form it. Cost is third."
If device makers and their suppliers can work together to optimize a tray's integrity and functionality and then determine how to produce it for the lowest cost possible, no one should be dissatisfied with the end result.
Equipment for Making Trays In-House
Some medical device manufacturers may wish to begin producing their own trays, but only if they can find a tray-producing machine that changes over quickly and keeps material, mold, and die costs down.
Sabin Corp. (Bloomington, IN), a medical device component manufacturer that specializes in extrusion, injection molding, insert molding, and thermoforming of thermoplastics, needed to find such a machine. The firm also thermoforms medical device trays and blisters for surgical kits and devices. But plagued with long setup and tool change times, the firm needed a more-efficient tray-forming system. Brett Baker, process engineer at Sabin Corp., points out that the firm also had "no verification of material temperature and system performance. Finally, trim press tolerances needed to be tighter and controlled for longer die life."
Baker first started searching back in October 1998 while in Venray, Netherlands, and that's where he saw a hydropneumatic in-line thermoformer from Paul Kiefel GmbH (Freilassing, Germany), which has a U.S. subsidiary, Kiefel Technologies Inc., in Hampton, NH. Then, at the K98 show in Dusseldorf, Germany, Kiefel was exhibiting its electric KMD 52 BFSS. "Two weeks later I visited Pack Expo in Chicago and further investigated the all-electric machine," he says.
Sabin ended up purchasing Kiefel's KMD 52 BFSS in-line thermoformer. "It had all of the elements to solve the problems we wanted to improve on," Baker says. The all-electric machine operates cleanly and features a quick-change tool system for faster setup times with precision, repeatability, and process control. Also appealing to Baker was the machine's precision press tolerances, material temperature control, and Windows NT interface. According to the machine manufacturer, Paul Kiefel designed the KMD line of thermoforming equipment to consume low amounts of energy to reduce operating costs. In addition, ease of operation and reduced maintenance requirements allow users to further reduce costs and to operate efficiently, while maintaining quality part production to meet customers' requirements.
At Pack Expo Las Vegas 99, Kiefel's machine operators changed over from one product to the next in an average of 35 minutes from shutdown to production, which required a different material type and width, a mold with a plug assist, trim die, and stacking unit.
This is exactly the capability Baker needed. "The fast tool change and start-up times dramatically reduce waste and scrap. Thermoforming is the smallest part of our business, but the equipment has allowed Sabin to become competitive with the largest thermoforming companies in the industry."
Sabin is now running the KMD 52 BFSS for production packaging. "We have 6 tools available and 40 tools slated for modification to be run before August 2000," Baker says.
PHOTO COURTESY OF KIEFEL
IMAGE COURTESY ALLOYD COMPANY, INC.
PHOTO BY RONI RAMOS