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Velcro molded on a wheel

DTI Globalwatch : 21 October, 2006  (Technical Article)
The mold for continuous injection molding of Velcro hooks consists of several dozen thin plates mounted on a wheel. Thanks to purpose-designed Velcro fasteners, a field crew can perform ceramic-composite armoring of military vehicles.
Hook-and-loop fasteners are on a list of unique technologies that scientists say have modified our lives. No less unique is the injection molding technology that Velcro uses to make this amazing stuff.

Listen for a moment and you may hear a distinctive ripping sound. It could be coming from baby diapers, aerospace vehicles, backpack flaps, shoes, or the seat covers and headliners in most automobiles, and much more. And we suspect that you, like most everyone else, know this magic stuff as Velcro.

The origin of hook-and-loop fastening is credited to George de Mestral of Vaud, Switzerland in 1948. Velcro is the registered trademark of the eponymous company that has been pushing the technology forward for more than 40 years, and that today offers hundreds of application-specific products from its locations around the globe.

Weaving a Good Start
The earliest hook-and-loop fasteners were woven textiles, and that technology is still used to make a wide variety of touch fasteners. But even as far back as 1970, Velcro Cos. was thinking about how to move from the relatively slow and complex textile process to something faster. Its principal goal was a more economical way to make the hundreds of thousands of 3D fasteners that secure upholstery onto automotive seat frames.

“We knew we wanted to make plastic hook and loops, but we didn’t know how to make it happen,” says Howard Kingsford, VP R&D of Velcro Cos. That desire led to a collaboration between Velcro USA (Manchester, NH) and Foster-Miller (Waltham, MA), a contract engineering firm founded 40 years ago for the purpose of turning ideas into production machinery and systems.

Foster-Miller designed and engineered an injection molding process for Velcro that made the hook material at high volumes with consistent closure performance, thus meeting Velcro’s business goals. As a bonus, the molded Velcro is less expensive and has many more uses than the standard textile-type fastener. Kingsford says it gave Velcro an industry edge.

Interestingly, the process FM designed for Velcro ignores one of the most fundamental characteristics of injection molding. The new process is called continuous injection molding. Injection molding, however, is known as a discontinuous process, owing to the need to open the mold to extract moldings. Wisely, Foster-Miller did not hire someone to say, “You can’t do that!” We know you’ve been looking, possibly very intently, at the photo of the Velcro CIM system above. The wheel-like structure in the foreground is the continuously rotating mold for the hook component of the hook-and-loop system. The material, most often PA66, is continuously extruded and fed to the mold through what FM refers to as a “shoe.”

The mold contains more than 15,000 cavities, each about 1?16 inch deep and less than 1?16 inch apart, in parallel rows across the circumference of the wheel. It is critical that the mold holds its shape without distorting to ensure quality and repeatability, and this design achieves that.

To strip the hook from the mold, Foster-Miller’s design employs several dozen thin (.06-inch) rounded plates that alternate across the thickness of the wheel. Between each cavity is a spacer plate, which seals off the open side of the cavity. This process design ensures that the hooks can be easily removed without damage as they are peeled from the mold.

Besides molding the male hook strips, the Foster-Miller system trims them, conditions them for flatness, and applies adhesive backing, doing away with those items as separate production steps. All of FM’s patent rights on the CIM system were assigned to Velcro Cos., giving them a proprietary process that sets an industry standard for fastener production.

The process still confers a significant advantage today thanks to its continuing evolution. Current systems are much different from the originals, says Ed Goldman, senior VP of Foster-Miller. For example, the initial width of the molded strip was a few inches. It is now “measured in feet,” he says.

Foster-Miller is as protective of Velcro’s exclusivity as ever, so key details of the design are not public. The Velcro CIM systems are in production around the world, and the collaboration between Foster-Miller and Velcro Cos. not only continues, but deepens.

Good for You, Good for Me
Foster-Miller continues to provide project support that ensures efficient application of the Velcro CIM technology, as well as find ways to expand its capability. As a result, Velcro has been able to stay focused on the process, not on machine building. Foster-Miller’s multidisciplinary engineering team, working as an extension of Velcro’s staff, provides those resources. Kingsford says the collaboration saved Velcro time and the technical hurdles prerequisite to doing the work internally. “We didn’t have to explain our business to Foster-Miller,” he says. “Even more critical was their respect of confidentiality, giving us exclusivity and market ownership.”

The relationship continues to be a win-win. Each has referred the other for business opportunities and they have worked together on a variety of projects. Velcro has Foster-Miller as a sounding board and resource for design, materials, and technology that the company does not have internally. “We can explore technologies and are able to sustain ourselves as industry leaders throughout the different markets we serve,” says Kingsford.

The latest cooperative effort between the two firms could also be called unique. Last Armor, a division of Foster-Miller, makes a special armor appliqué system that increases the protection for light-armored personnel carriers. The armor installs on the exterior of the vehicle without any cutting, welding, or drilling. FM collaborated with Velcro to develop the specially designed spiral hook fasteners that make the armor easy to replace and/or reconfigure onto other vehicles. Velcro, in this case, is Foster-Miller’s supplier.

Foster-Miller developed a special adhesive for the fasteners so the armored tiles stay in place with increasing movement. The more the ceramic tiles wiggle, the tighter they become. The fastener technology means that Last Armor kits can be sent to vehicles deployed in the field, and the vehicle crew can do the install in a short time.

“Velcro Cos. has been an excellent customer, and also a business partner when we needed them to help with our own products,” says Goldman.
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