By Bruce Geiselman
Micromolding — a highly specialized injection molding process — in recent years has received increased attention from designers and manufacturers as technological advances require the miniaturization of parts.
One of the fastest growth areas for micromolding is micro-optics, according to Accumold, one of the country’s oldest micromolding companies.
Parts for micro-optics require micron-level tolerances. Micro-optics are used in fiber optics for the telecommunications industry and have applications in sensors and medical devices, like endoscopes and minimally invasive surgical tools.
“Some of the micro-optics that we mold for the datacom [data communications] and sensing market have plus or minus 2-micron positional tolerance on a lens,” said Aaron Johnson, Accumold’s VP of marketing and consumer strategy.
Micromolders also produce microelectronics, other components for various medical devices, automotive sensors and lights, and parts for emerging technologies, such as components for smart devices like smart watches and fitness trackers.
Defining micromolding can be tricky, and different micromolders offer different definitions. However, Accumold defines micromolding as having one of three features:
Parts that are micro in size, often under a few millimeters;
Larger parts, up about 5 centimeters, with microfeatures;
Parts with accuracy to within 25 microns or less.
Johnson said there is not a textbook definition.
“We usually tell our customers, if you’ve got 50 other molders that you can quote this with and they can mold it, that’s not something we’re going to get involved with,” Johnson said. “At least for us, precision is a big piece of it, and that’s the space we hover around.”
The smallest commercial part that Accumold has manufactured and is permitted to discuss measured 800 microns long by 360 microns by 380 microns, Johnson said.
Some of the plastics used in the process include PE, PP, polyamide, PC, polyoxymethylene, polysulfone, polybutylene terephthalate, acrylic, PEEK, polyetherimide and liquid crystal polymers.
Three decades of experience
A pair of mold makers with experience with microelectronics formed Accumold 35 years ago, making it one of the first companies dedicated to micromolding.
The founders realized there would be a demand for better micromolding services because of advances in microelectronics. To meet that need, Accumold decided to build its own injection molding machines.
Today, several injection molding machine manufacturers target the micromolding market, but that was not true in 1985. Accumold today continues to use its own equipment. Being a machine builder is “part of our DNA,” Johnson said.
“It gives us the control and the kind of efficiencies that we believe are important to serving our industry,” he said.
Speed, precision and repeatability are key requirements for injection molding equipment used in producing micro and small parts, he said.
The company, citing proprietary concerns, does not release specifications regarding its injection molding presses.
“It’s one of those things that we’ve kept close to our vest because it’s a unique thing to Accumold and something they decided many, many years ago, so it’s not for public consumption,” Johnson said.
In addition to 80 proprietary Micro Mold machines, Accumold operates 70 small machines manufactured by Sumitomo, which are used for slightly larger parts, many of which might include microfeatures.
“We have up to 35-ton Sumitomo machines for what we call our small molds — that’s for the larger components, maybe with microfeatures or other critical details,” Johnson said.
The company calls its 35-ton injection molding machines “monster presses,” he said. In addition to building its own machines, Accumold employs its own moldmakers.
“It also means that we’re kind of tool builders by our heritage, so we have a fully integrated tool shop,” Johnson said.
Building its own presses and molds ensures the company’s injection molding processes minimize material usage and have the speed and efficiencies scaled for microparts.
“If you think about trying to make a grain of rice in an injection molding tool that’s on a press that’s built for making Frisbees, you’re going to have a part-to-runner ratio that’s extreme, and that means waste,” Johnson said. “That means all sorts of challenges. We wanted to build something that could give us the efficiencies in material usage and speed that match the parts that we’re producing.”
Johnson compared Accumold’s approach to a musician playing a Steinway piano.
“It’s important to have the right machine — a good machine — but you also need the virtuoso to go with it,” he said.
That means employing workers with the moldmaking and processing skills to understand how a material works with tools that include microfeatures. While the company’s toolroom features equipment commonly used in producing molds, employees need specialized skills. A lot of the challenge in working with a client on a mold design lies in knowing how a particular resin will behave.
“They don’t all perform the same way at the microlevel,” Johnson said. “There really isn’t a textbook way to say, will this material work? You go to the datasheet, you ask your resin suppliers, and sometimes they are not familiar with what you can do at a microlevel. … With the datasheets, the suggested gate size is often bigger than the parts we are making, so there isn’t really an easy way to say.”
That’s where the company’s 35 years of experience helps it to pair the best resin with the best mold design, he said.
To ensure an adequate supply of skilled workers, Accumold awards scholarships each year to students to attend a local community college’s tool and die program.
“They will need the basic machine skills, but then we come in and teach them and train them on the Accumold way and the way we do things,” Johnson said. “That’s really kind of the pattern throughout the rest of our organization. Whether it’s our press operators or our quality technicians or quality engineers, it’s all about, here is the basic skill set we need, but then here’s the Accumold way. … We do a lot of internal training and ongoing training as an organization.”
To handle the complexity of building molds with microfeatures and to meet the company’s goal to bring products to market quickly, mold makers specialize. Specialty areas include mold design, core pin construction and cavity construction. The company employs 75 workers in its toolroom, and 15 to 20 of those workers might be involved with a specific mold.
“It’s not one guy making a mold,” Johnson said. “It’s a team of people and the different specialty machining processes that they’re involved with, and it all has to come together. It’s like doing a jigsaw puzzle and you have 15 pieces made by 15 different people, but at the end of the day, they all have to fit and make the right picture.”
Bringing all those people together to create one part — quite often, just a small component of a bigger product — is one way Accumold has found to manufacture parts other molders have passed on. When other molders have said a project is impossible, Accumold have zoomed in on a strategy.
Accumold, Ankeny, Iowa, 515-964-5741, www.accu-mold.com