Advances in thick-gauge thermoplastic parts

Departments - Components 4 Design

Technology is the star in medical devices from MRI and blood analysis machines to CT and PET scan equipment, but they could not function without the custom covers, panels, housings, and enclosures that provide sensitive electronic components structure, protection, and aesthetics.

March 27, 2014
Danny English

Custom medical device parts have long been made from thick-gauge thermoformed plastics for cost-effective quality and cosmetics, and recent advancements in thermoforming have increased the advantages of doing so.

Thick-gauge thermoforming traditionally involves heating a 1/16" to 5/8" plastic sheet to a pliable temperature, shaping it in a mold, and then finishing it into a usable part. The result is an extremely durable, anti-abrasive, lightweight, part with crisp features and fine surface detail.

With recent advances, medical device designers and manufacturers have a new range of options, starting with the capability of some vendors to create thick-gauge thermoformed parts large enough for even the largest MRI covers.

New choices also include built-in, anti-microbial agents and a twin-sheet thermoforming process that simultaneously thermoforms two sheets of plastic and bonds them together. Screen-printing, hot stamping of logos, and even assembly, fabrication, and fulfillment are also options.
 

Oversize medical parts

MRI, PET, and CT equipment designed to image an entire human body, or significant parts of it, can be massive. Even X-ray, radiology, mammography, incubator, and diagnostic blood analysis equipment can be large and bulky.

For larger parts, the traditional approach has been molded fiberglass where size, wall thickness, and radii limitations are typically heavier. Oversized thick-gauge thermoformed parts, on the other hand, are lighter and stronger at nearly half the cost.

“Thermoformed plastic is the logical upgrade from fiberglass when large medical parts, panels, housings, or enclosures are needed that must be durable and lightweight, yet aesthetic and affordable,” says Wynn Kintz, president of Kintz Plastics, a New York-based thermoformer that has specialized in medical devices for almost 40 years, making products for the industry leaders in biomedical equipment.

Yet creating parts large enough to encompass the entire human body is unique to all but a few thermoformers because it requires large capital investments. Kintz’s company, which makes large covers for a majority of the MRI machines in the medical market, can thermoform parts up to 9ft x 13ft with a 60" draw. It achieves this using a piece of equipment called Jumbo, the largest four-station rotary thermoforming machine available in the eastern United States.

Built-in anti-microbial protection

In healthcare, maintaining a hygienic environment is critical. That can be difficult in a clinical setting, even with routine equipment cleaning, because a variety of patients and personnel use medical devices.

“One helpful new option for medical device manufacturers is to add an anti-microbial agent during the manufacturing process that fights microbes such as bacteria, fungi, mold, and mildew for the life of the product,” Kintz says.

When the anti-microbial agent is spread throughout the thermoformed material, its protection is effective both on its surface and in its substrate, and will not wash or wear off.
 

Twin-sheet thermoforming

Twin-sheet thermoforming, an advanced vacuum-forming technology, is a good choice for some medical device panels and enclosures. These parts will be seen from both sides, needing added strength, or will house insulation, mechanical, or electrical components. The process simultaneously thermoforms two sheets of plastic, then bonds them together to create a durable, lightweight, and economical double-walled structure.

“Since twin-sheet thermoforming replaces two processes with one, it saves time and labor, creates a seamless part and stronger structure, and results in a lighter, more cost-effective component,” Kintz explains.

On a recent redesign of enclosures for a medical diagnostic testing instrument, twin-sheet thermoforming reduced the cost of the doors by 30% to 50% compared to a fiber reinforced plastics (FRP) process, according to Kintz.

“Compared to injection molding or blow molding, twin-sheet thermoforming can reduce tooling costs by up to 90% and cut tooling development time in half,” Kintz says.
 

Early vendor assistance

Because every thick-gauge thermoforming application is unique to the medical device, some vendors are willing to send engineering teams to customers to consult during the early stages of development.

Even the largest, most sophisticated biomedical companies can benefit from early vendor involvement. Beckman Coulter, a company that develops, manufactures, and markets biomedical testing products, realized significant improvements in the manufacture of several blood analysis instrument parts after partnering with Kintz Plastics.

Kintz & VeinViewer collaborate

Kintz Plastics was awarded production of the covers for the VeinViewer. This product has achieved significant visibility worldwide, including recognition by Time magazine as “one of the coolest medical inventions of the year.”

VeinViewer makes veins visible to the naked eye, eliminating multiple sticks to draw blood or insert IVs. Using multiple patented technologies, it projects a real-time image of the underlying veins onto the patient’s skin, enabling a clinician to locate the exact location of a vein to within 0.06mm.

Six pressure-formed parts cover the unit – ranging in size from 2.0" x 6.0" to 21.5" x 20.0" with a 19.0" depth of draw – and each part is designed with a formed-in undercut to fit precisely together on the unit so that all the seam lines are uniform once assembled.

www.christiemed.com

“Engineers know the required design outputs, but the product can benefit from expert vendor input,” says Sean Peters, a senior procurement analyst with Beckman Coulter’s diagnostics division in Chaska, Minn. “When Kintz Plastics helped our engineers with thick-gauge thermoforming material selection and manufacturability on several blood analysis instrument parts, we achieved at least 20% cost savings, 20% time savings, and enhanced quality with a three month ROI on the tooling.

“Any time we can reduce the cost of material, it goes right to our bottom line,” Peters adds.

The consultation also enhanced the function and aesthetics of several parts.

“Several vendors had previously refused to even quote us on a part because its shape was unique and difficult to make,” Peters says. “Another part, a sample presentation unit input door, required a clear, high-impact, blemish-free surface for easy viewing. Kintz Plastics worked with us on both these high-tolerance parts to get the precision and aesthetics just right.”

The optimal material for a part is usually based on cost, performance, appearance, and regulatory requirements.

“When my design and engineering team consults with medical device designers or manufacturers, some of the factors considered include necessary part rigidity versus appearance, cost, finish options, conductivity, as well as density and weight,” Kintz explains.
 

One-stop shopping

From design engineering to fulfilling and shipping the thick-gauge thermoformed part, the more a vendor outsources any aspect of the work, the greater the potential for delays.

For the best results and turnaround, Kintz recommends working with a vendor with in-house engineering, tooling, and post-forming capabilities. “A thermoformer with its own engineering staff can provide practical, on-site expertise to the design and engineering process,” Kintz says.

“A one-stop-shop that can make its own tooling, and can trim, route, paint, screen print, assemble, and ship products has more direct control over the entire process and can complete the job faster and at lower cost.”

 

Kintz Plastics Inc.
www.kintz.com