Micromolding, where small is not only beautiful, but profitable, too

All things small are making a big splash in manufacturing, and micro molds to make micro parts in micromolding machines are creating big opportunities for plastics processors.

Micro components are nothing new in the world of manufacturing, but have been around for more than 100 years—think small metal fabricated components used to make Swiss watches. Applications began expanding about two decades ago, again mostly in metal fabricated parts for electronics applications. The arrival and subsequent shrinking of computers, cell phones, and digital recording devices such as the iPod and the iPod Nano, which demand smaller and smaller plastic parts, have opened that world to injection molders and moldmakers.

In fact, DME Co.’s top advancement in hot runner technology in 2009 was the advanced micro-nozzle for processing close center-to-center small part applications, such as medical parts in polycarbonate, says Dave Lange, director of sales. “This new hot runner product has a smaller outer-diameter physical dimension and a smaller inner-diameter flow channel,” he says. “The spacing between one nozzle and the next is closer, which allows for molding smaller parts.”

DME continues to explore miniaturization of some of its products, especially for tiny medical applications. “Historically, those footprints have been a little bit larger because of the restraints of the nozzle diameter,” says Lange. “For the micro-nozzle, we had to reexamine the nozzle and then explore heater technology that would provide optimal heat distribution.”

A manufacturer of EDM equipment for micro molds, SmalTec International (Lisle, IL) is seeing a significant increase in demand for its products, says Jerry Mraz, general manager. Its primary product offerings, EM203 for EDM micro grinding (injection molded parts) and GM 703 for EDM nano grinding to 10 nm, derived their technology from Panasonic, and the independent company was established in 2002, according to Mraz.

“Micro is prevalent in the medical industry, where things are really picking up,” says Mraz. “As parts get smaller they can’t be machined; they have to be molded, and so you need a mold.” The downside is many medical device manufacturers have their own machine shops. “The big medical OEMs will spread the work out over 15 suppliers, and getting the benefit of volume work is difficult,” says Mraz. “There needs to be some consolidation.”

SmalTec also does prototyping. “We’ll do the micro part for our customers and they will do the macro side,” Mraz explains, noting that this year the company is on track to see its second-best year.

On the injection machinery side, there is agreement that miniaturization and micro molding are “hot right now,” says Tony Brusca, president of Alba Enterprises (Rancho Cucamonga, CA), North American distributor for the Barcelona-made Babyplast micro injection molding machines.

He points to the business that U.S. molders and moldmakers have lost to Chinese manufacturers. “Everyone is looking to different markets that can’t go offshore,” says Brusca. “I think a lot of this creativity came out of the fact that business was so bad, so a few people began specializing in micro, similar to what we see in the overmolding or two-shot area.” He says that he’s finding more interest in medical implantables, such as with bioresorbable materials.

In addition to processing most thermoplastic materials—engineering materials such as Torlon and carbon-filled PEEK—as well as LSR, metal, and ceramic, the full-proportion Babyplast has a production-space-saving footprint. “What some were doing when they first got into micromolding was using smaller screws and barrels to reduce the residence time in big presses, but the larger presses still have a big footprint,” says Brusca.

Serving this segment, Arburg recently introduced its new micro-injection module for milligram-scale parts, combining screw plasticating and piston injection. A servoelectric driven screw preplasticating section is installed at a 45° angle to the horizontal injection unit, ensuring that standard granulates are prepared under ideal conditions. The molten material is then transported from the preplasticating stage to the injection unit via the injection screw, which acts only as the carrier.

The screw has an 8-mm diameter and is fitted with a nonreturn valve that operates according to the screw/piston principle; this permits small shot weights to have a high level of precision. The melt is continuously fed from the material inlet to the tip of the injection screw, eliminating long dwell time in the injection unit—a problem in micromolding. (Read initial coverage at plasticstoday.com; search for “milligram-scale parts.”)

Big growth, small parts
Involved in molding “big” micro parts (as small as a grain of rice) on its 27 molding machines (25-110 tons), Plastikos Inc. of Erie, PA is an outgrowth of Micro Mold Co. Inc., which designs and builds molds for electronics OEMs primarily, but also has “a growing medical” business.

“We don’t think in terms of parts per pellet like some micro molders, but we focus more on very small parts with extremely tight tolerances and micro features,” says Philip Katen, GM at Plastikos and president of both companies. Micro Mold was founded by Philip Katen’s father Tim Katen and partner Dave Mead in 1978. Ownership and management of both companies transitioned in the fall of 2009 to Philip Katen, Ryan Katen, Matthew Mead, and Rob Cooney.

Philip Katen explains that Micro Mold and Plastikos have seen an evolution over the past decade in which engineers and designers are designing parts with ever-smaller features. “What was small 10 years ago is huge by today’s standards,” says Katen. “They’re definitely continuing to push the physical limits of the materials, and material suppliers are coming out with high-flow materials and other properties to accommodate micromolded parts. We’ve also seen the complexity and intricacy of these extremely small parts increase. We didn’t see anything like this 10 years ago.”

There are a select few materials that can be used in micromolding and still hold the tolerance dimensions required. In very thin-wall applications for electronic connectors, Katen says the company recommends liquid crystal polymer (LCP). Plastikos also uses engineering-grade or specialty-grade resins. “We worked with PolyOne to develop a custom grade of material—50% mineral-filled LCP—that would create a very thin-wall part with 1362 circuits in it on a structure only 1.5 by 1.5 inches,” relates Ryan Katen, engineering manager at Plastikos and GM at Micro Mold. “Originally the customer had specified a different material that did not work with this part’s geometry. In these parts with very thin walls, we’re asking the materials to do something that is a real challenge for the engineer.”

“PolyOne performed many DOEs trying to get the right balance of physical properties while providing an easily processable material for this part,” explains Jim Farwell, market development manager with PolyOne Specialty Engineered Materials. “The process required that we have extremely good flow properties for very tight-tolerance molding, given the number of circuits, and no flash or warp requirements. That meant our material had to flow well, which was one of the challenges.” PolyOne went to a 50% mineral-filled LCP material that had lower viscosity at high shear rates compared to the material being replaced.

Another challenge was that Plastikos was using high injection pressure and having inconsistencies filling the part, Farwell says. “They were getting short shots, and because of the part size and ejector pin location, the part would hang up in the tool,” he says. “Our LCP material provides better shot-to-shot consistency, consistent fill without flash, and positive ejection. Plastikos was having more than 50% scrap rate with the material they were using so being able to solve this problem for them . . . was huge.”

It’s tough to make the tools
Machining micro molds is also a challenge, and more tedious. “You have to rely on the CNC to hit the dimensions and it requires more attention from the toolmaker,” says Ryan Katen. “The smallest ball end mill we have will give you a 0.005-inch radius. And on the steel side, tolerance stack dimensions are generally ±0.000020 inch per core or ±0.0003 inch over a stack of 10 cores. We need a tight stack-up in these molds.”

Rob Cooney, manufacturing manager for Plastikos and VP of both companies, notes that over the years the companies have been in business, parts have become much smaller. “When Plastikos started, we had electronic connector parts with a 2- to 2.5-mm centerline that may have been 50-100 circuits long,” says Cooney. “We still run some production here on those, but the newer products are 0.5 mm, which doesn’t give you much more than typically a 7- or 8-thousandths piece of steel to make your circuit.
“We’ve focused on a number of different ways to add alignment and support in the mold, because injection pressure and cavity pressure go way up, which means we need a robust tool to support the material we’re trying to push into the tool,” Cooney continues. “We have a couple of applications where material suppliers designed custom materials so we could meet customer requirements. Our customers are also pushing us to mold some things that few, if any, materials are capable of. We’re really pushing the material limits.” Plastikos primarily uses Ticona’s LCP plus a number of other engineering resins.

Micromolding pushes the boundaries of just about everything—design, machinery, materials, and tooling—to meet the demands from Plastikos’ customers that even a couple of years ago they’d say were impossible, says Phillip Katen. “But that’s why we say we make the impossible possible for our customers.”

Mini + micro in medical
Clearly, not all micro parts are created equally. Medical contract manufacturer SMC Ltd. (HQ in Somerset, WI) defines “micro” as part sizes starting at 0.003 in3 (0.045g) and smaller, yielding approximately 10,000 parts/shots per pound minimum, including the runner, says Christie Wander, SMC’s marketing manager. With facilities across North America and in India, the company provides both micro and miniature molding capabilities for global OEMs.

Miniature parts, on the other hand, are bigger than 0.003 in3 but can be molded in a 10-ton (or smaller) conventional molding press. While miniature parts have close tolerances, micro parts have the closest possible tolerances. SMC molds parts from PEEK, Ultem, and bioresorbable materials in addition to other engineering thermoplastics.

There’s always been a need for miniature parts in various applications, and those were typically done on the smallest molding machines available, says Pat Kavanaugh, director of micro and miniature molding at SMC. “However, as materials and parts became smaller and more complex, there needed to be a more robust process to accommodate them—a process designed specifically for the part, rather than making the part fit a generic process,” he explains. “Because we do so many medical devices, the micro parts are typically components that are part of the devices. The whole piece of the puzzle is the complete device, which is what we focus on.”

Kavanaugh says SMC’s business has focused on small parts all along, “but as materials became tougher to mold in standard equipment, there was definitely a need to rethink how we manufacture them, and as little as three years ago, we needed to define a robust process for micromolding.”

SMC has experienced the industry trend of parts getting smaller to accommodate advancements in medical technology. With the increase in “micro surgeries” done through a tiny incision, implanting a small device or using smaller surgical instruments has become the norm. “The smaller they go and the less invasive the surgeries become, the less time the person spends in the hospital,” says Kavanaugh.

Often a customer comes to SMC with a concept for a full assembly and parts within the assembly that the customer doesn’t know how to make. “They want micro parts, which means we have to come up with a process. A unique material such as a bioresorbable or implantable material might need a unique process. As you get into things like implantables and bioresorbables, the cost goes up significantly as material costs can be $20-$30/lb all the way to $1800/lb,” Kavanaugh says. “Running these parts on standard equipment may not be cost effective. The delivery system [runners and sprue] in standard equipment will use a lot of material that cannot be reused due to FDA regulations.”

SMC focuses on developing a process to make micro parts, and if a specific machine is required, the company has the capability to make it in-house. “We build a system around a material and a part,” explains Kavanaugh. “That way we can use the best machine for the process. There’s no compromising at SMC. We’re building parts that are on the edge—thin walls, thin little cores—so we’re already on the edge of the process, which means you want to take advantage of everything around that process so the parts are not compromised more than they already are.”

All micromolded parts at SMC follow the same validation protocols as nonmicro parts. “The difference is in inspection methods and part handling,” says Kavanaugh. “Inspecting micro components requires the use of microscopes—and this has its challenges, too. When we blow a part up 10-20 times, we see things we don’t normally look at in a regular part because we’re looking at things in relationship.” For example, a gate vestige on a normal-sized part might look fine, and meet spec. “On a micro part under a microscope, that gate vestige looks absolutely huge when it might only be 0.010 inch—the microscope makes it look bad. The same is true for parting lines—they show up 10 or 30 times their size and look terrible.”

Handling micro parts is also a challenge and requires special procedures. Just picking up the parts is difficult, and usually the operators use small tools. “Because of static electricity, you can’t just set them down. The slightest movement of air can blow them away,” says Kavanaugh. “It certainly keeps things interesting!”

Separating fact from fiction in the micro/nano world
Micro and nano manufacturing might seem like futuristic ways of manufacturing but in fact, both micro and nano manufacturing are technologies whose time has come. A recent survey by the Society of Manufacturing Engineers (SME) found that out of 300 manufacturing professionals who expressed an interest in micro manufacturing, half are already using it in their products today. And more than 60% indicate nanotechnology is important to their organization’s future growth.

According to the SME, there are many myths associated with these smallest manufacturing processes, and SME wants to “bust these myths into nano-sized particles so that manufacturing practitioners can take advantage of these real-life sci-fi opportunities.”

Myth #1: Micro- and nano-manufacturing are technologies that may be something great in the future, but they are not viable for today’s business environment.
Fact: Both nano manufacturing and micro manufacturing are actively being used by many manufacturers. Nano manufacturing is being used by Boeing, RubberMaid, Gillette, and many other companies.

Myth #2: Micro manufacturing is used only in the electronics industry.
Fact: Micro-manufacturing now reaches far beyond electronics. For example, it is essential in the production of many medical devices and critical aerospace systems.

Myth #3: Micro and nano are just reduced sizes of the life-sized objects.
Fact:
The rules of the game are changed when dealing with these technologies. There are significant process and material behavior changes beyond size that you need to understand.

Myth #4: If I can machine “small” stuff, I can “micro” machine.
Fact: Machining micro pieces requires special tools and skills. In traditional machining, the greater force is exerted by the machine tool onto the material. For micro-manufacturing, it flips, and the material exerts more force on the tool.

Myth #5: If I can mold “small” stuff, I can mold micro parts.
Fact: Molding micro pieces requires special tools and skills. Often the piece or feature is smaller than a pellet of the material. This requires special attention to the flow, pressure, fill time, and increased impact of the material reaction with the mold wall and, most critically, the design of the mold itself.

Myth #6: Even if I wanted to use micro or nano manufacturing processes, the tools, suppliers, and materials are practically nonexistent.
Fact: While that once was true, it’s not so much any more. There are growing numbers of processes, tools, materials, and suppliers available for manufacturers ready to move into micro and nano manufacturing.

Myth #7:
What is happening in this field is all “hush, hush” so I can’t find experts to teach me.
Fact: Not true. Plenty of experts were available to teach SME members about these technologies at this year’s MicroManufacturing Conference and NanoManufacturing Conference held in Mesa, AZ April 14-15.
Clare Goldsberry

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