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A Big Demand for the Smallest of Parts

Micro Molding

Iowa pioneer of micro-molding says art of producing small parts is not just about size

There's small. There's micro. And then there's super-micro. Accumold handles all three with a "micro-mindset," where artistry, talent, and tooling have as much to do with crafting the smallest of critical components as the molding machine that forms them.

The company, which primarily serves clients in the medical, micro-electronics, and micro-optics industries, is able to handle part sizes less than 1mm in size, tolerances under 5 microns, and part features at sub-micro levels, according to Accumold's marketing manager, Aaron Johnson. The largest part Accumold ( produces is about three inches in diameter and micro-molded parts range in size from 1/2 inch to parts with features measured in microns. But micro-molding goes far beyond part size.

"We define micro-molding by size, features, and tolerances," Johnson said. "You can mold simple little pieces here and there, but if the parts don't contain micro features, tight tolerances, tough geometry and/or the parts aren't on the extreme side of size, then it probably isn't true micro-molding."

Injection molders who simply buy a machine to get into micro-molding are in for a big awakening. "It's not just about making a big tool small. When making small parts, not only do you need to know how to build the tool, you also need to know how to handle the material so it gets to where it needs to go," Johnson said. Ankeny, Iowa-based Accumold has been in the business of micro-molding for the past 25 years. When two tool makers who started the company built their first micro-molder, it was possibly the first in the world. Accumold came to "shape and define what micro-molding is" just when electronics and medical applications were beginning to get smaller, he said.

Minimally-invasive Procedures Trend Smaller

The medical industry often requires the smallest of parts so procedures are less intrusive to the body. The most challenging parts Accumold faces come from the medical industry, said technology manager Greg Peterson, who started with Accumold 22 years ago as a tool maker. Parts for the medical industry continue to get smaller with even tighter tolerances. "If you're making parts for a delicate surgical procedure, you need to have very little flash or parting line defect because it could actually scratch tissue during the procedure. So we are very aware of how these parts are used and how critical common molding features are," Peterson said.

Areas of growth include medical parts for hearing instruments, surgical tools, and catheters. "The tip of the catheter is where we make components and their (medical industry's) goal is always to go smaller so it's less intrusive to the body," Peterson said.

Accumold is ISO 9001:2008 and ISO 14001:2004 certified, and is working toward obtaining ISO 13485 certification for medical devices. With experience molding medical-grade thermoplastics, including PEEK, PC, and PSU, Accumold also has three class 100,000 and two class 10,000 clean rooms and experience working with timelines dictated by medical testing and regulation processes.  "The constraints put on a medical part go beyond the part geometry itself because you have to have clean environments, you have to work with their medical-grade materials, and you have to have traceability," Johnson said.

Even with strict timelines affecting the medical industry, quality always reigns supreme, Peterson said. "They're willing to wait for quality. They have had parts in development for anywhere from two to five years and are just now getting to the point where they're molding, so they're willing to wait a few extra weeks to get a useable molded part and go into qualification with it," he said. Johnson added that the medical industry has to meet certain FDA timelines, and devices that parts go into run the gamut from hearing instruments to life-saving mechanisms. "They want a group of suppliers that can basically supply them with perfect parts so their devices go together without hassle," Johnson said. "They have a lot of interest in the details, and a lot of interest in the quality."

In the past, many medical device manufacturers had been developing parts that were machined, but now want molded parts with the same surface quality. "Imagine a surface that had to be tight enough to seal an O-ring on–we're molding that today," Peterson said.

A medical customer needed a tip over-molded on the end of a 0.030-inch-diameter tube, and the tip had to have a particular port so it could inject liquid through it at an "unfriendly angle." The part was critical to how the assembly worked, and the customer had been searching for years for a company that could handle the requirements. Accumold, with its micro-molding capabilities, was able to handle the tough size constraints and geometries.

"Because of that success, the company has been able to design similar parts and begin to push the limits of their own technology now that they've been awakened to the possibilities of micro-molding. It's an enabling technology, and it's one of our strategies to help educate designers and product developers out there that maybe are not familiar with the benefits of the process and the types of designs it opens up," Johnson said.

Micro-optics for the medical industry is another area of strength for Accumold, with a lot of parts going into catheters for endoscopic use and for imaging. "They take a video as a catheter travels through your artery system or your veins or your heart, and all that is done with micro-optics," Peterson said. "And we have other components, too. There's some amazing technology out there. They're actually mapping surfaces inside your arteries with some of the parts we make."

Accumold handles extremely tight requirements with lens-to-lens centricity for 250 micron fiber optic lenses, parallel array products, demux devices, and diffractive lenses. The company also handles molding attenuated resins and adding IR, AR, and reflective coatings onto plastics. And while telecommunications is a big market for micro-optics, products like medical diagnostics, endoscopic, and minimally-invasive surgical tools and micro-sensor applications are taking advantage of these tiny lenses.

"Sensors are another application where optics comes into play for diagnostics or a measurement. We worked on one project for a customer that wanted to count blood cells as they travelled by in a fluid channel, and they were using optics to measure that," Johnson said.

Accumold has an optical tooling expert on staff, and some tasks include running micro-sized optical couplers, integrating lenses into housings, replicating lens profiles within a quarter of a wave, and lens surface finishes within 50 angstroms.

High Material Costs Demand Efficiencies

One major benefit to the micro-molding process is the efficiencies in materials usage. With PEEK costing about $40 to $60 per pound, implantable PEEK costs around $1,500 per pound, and Accumold is very sensitive to the customer's concern with keeping costs down. "Micro molding is very efficient and some of these materials are very expensive, so our customers are looking for ways to make their micro and small parts efficiently because they don't want to waste any effort on the runner or screw system. They want to maximize what they're spending on the part itself," Johnson said. "Because we find ourselves running a lot of these exotic and engineered resins, there's a huge advantage in the efficiency of micro molding."

The efficiencies are achieved through precision tool design. "That's where our 25 years of experience in doing very small parts gives us the advantage," Peterson said. "We are very conservative when it comes to the tool design for the runner and the gate systems. We always keep the sizes of those features as small as possible, reducing any more materials cost that way, and that allows us to be more competitive. Efficiencies in molding are our niche because we are very aware of the cost and of reducing any type of scrap as far as a runner and that sort of thing. That is our micro-molding advantage right there. The more expensive the material, the more competitive we are."

Although Accumold does not aid in the development of raw materials, it does help test the new materials that resin suppliers are coming out with to see how the plastic flows and whether it can fill very small features and thin walls. "We have a lot of insight into how different materials flow and how material choice alone can affect feature performance," Johnson said. "Material is a bigger piece of the puzzle for micro-molding than it may be in a more standard injection molding environment, and our expertise and experience with those materials gives us an advantage for evaluation."

Accumold's projects include highly-engineered materials, such as PEEK, UltemĀ® (PEI), liquid crystal polymer (LCP), and nylons, which are sometimes processed with glass, carbon nanotubes, or other resin fillers that add certain strength or stability to a part.

Accumold has state-of-the art machinery and builds custom machinery for micro-molding, but both Johnson and Peterson stress that a micro-molder is not classified by hardware alone. It is the combination of innovation, processing, and expert tool building that make up the elements of true micro-molding. "Equipment is one thing, but finding the right people to operate and use that equipment to be able to do the craft of building these tools is the key to our success," said Peterson, adding that of the 165 employees in the recently expanded, 82,000 square foot facility, six have been with the company for more than 20 years.

"The machines in the tool room are something you find in any state-of-the-art tool shop for our industry," Johnson said. "Where the custom side comes in is with our micro molder. We have standard injection molding presses, which we buy, and then we have the micro molder, which we build ourselves. It's the same idea as how the company started, and it's something we continue to innovate over the years. It's unlike anything on the market and it's something we keep as a trade secret," Johnson said.

Accumold's strongest capabilities fall into three categories: Micro-Mold® parts, small parts, and lead frame/ insert molded parts where the company can mold plastic on and around different types of metals, plastics, fabrics, foils, and devices. Lead frame is described by Johnson as a continuous reel-to-reel molding where a strip of metal is constantly articulating through a mold base. The micro-electronics industry is a prominent user of lead frame or insert molding for high-volume applications.

"Lead frame is perfect for those high-volume applications because what our customer does is take the giant reel and put it into their assembly system so that it's what we call 'manufacture ready,' saving many steps in the process," Johnson said.

One company required a custom micro-connector that called for multiple metal micro-inserts embedded in the plastic. This project required a system to automatically load the metal inserts, mold the parts, test them for defects and continuity, then package them in a custom tape-n-reel system. This project had several challenges: the micro-inserts required special handling and manipulation; the complete part required very tight tolerance with very thin-wall sections; and the part needed to be clocked and oriented in packaging so the customer's next phase of manufacturing could accept the parts correctly. Accumold applied its expertise in micro-molding, Johnson said, to build a dedicated molding system complete with a custom molding press outfitted with custom insert articulation, quality inspection points, and automated packaging.

Part handling and packaging is, in many cases, almost as important to the process as making the part, Johnson stressed. Molding and packaging a small part so it's oriented in a manner that's useful to the customer is no small feat and is a necessary part of the process. Accumold offers reel-to-reel packaging, light subassemblies, lead frame die-forming and singulation, in-line inspection, and other custom secondary processes.

Ultem is a trademark of SABIC Innovative Plastics IP BV.

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