Some mechanical properties are inherent in the material, which is usually a starting point for design, said Johnson. In material selection, criteria such as biocompatibility, heat deflection, wear patterns or flexibility are important considerations. Accumold works with common thermoplastic materials, including PEEK, Ultem, glass-filled Nylons, and other medical grade and attenuated materials.

According to Johnson, OEMS interested in procuring micro-molded components tend to have pain points that revolve around two aspects: geometry and scale.

Editor in chief of PlasticsToday since 2015, Norbert Sparrow has more than 30 years of editorial experience in business-to-business media. He studied journalism at the Centre Universitaire d'Etudes du Journalisme in Strasbourg, France, where he earned a master's degree.

But Johnson noted that providing a set of rules can be limiting, particularly when the rules are based on principles intended for traditional injection molding. “The guidelines break down when you start to push the limits,” he said. “I asked one of our technology managers who’s been here almost 35 years: ‘What’s your guideline to give a customer on aspect ratio?’ He originally told me six to one. Then you could push him and he could say 10 to one, or eight to one—somewhere in that realm.”

As Johnson sees it, a component or manufacturing part that weighs less than a gram is considered a candidate for micro-molding and can further be defined along three criteria:

Lucid Motors is a Silicon Valley–startup that began in 2007 as a supplier of EV batteries and powertrains. It pivoted to the production of high-performance luxury EVs in 2016 and announced plans to build a $700-million manufacturing plant in Casa Grande, AZ. The company received an influx of funding in September 2019 from the Saudi Arabian sovereign investment fund to the tune of more than $1 billion. In February 2021, Lucid Motors announced a deal valued at more than $11 billion to merge with Churchill Capital Corp IV, a publicly traded special-purpose acquisition company.

Central to successful design for micro-molded components and parts is having a clear understanding of the end-user’s stated and unstated needs. That’s because producing components and devices from design parameters for small or micro parts come with a unique set of challenges and opportunities—and these are not typically associated with traditional injection molding techniques, argued Aaron Johnson, vice president of Marketing & Customer Strategy at Accumold, during a Nov. 30 Virtual Engineering Week presentation.

The Lucid Air reportedly is the world’s fastest-charging luxury electric car with a range of up to 530 miles on a single charge under ideal conditions. Materials supplier Sabic helped to make that happen, which is why the Lucid Air is on display in hall 6 on stand D42 at K 2022 in Düsseldorf, Germany.

Sabic thermoplastics are present in more than 25 applications, including structural and battery components and interior parts. Sabic said that its engineering support helped reduce warpage, optimizing manufacturability as well as part performance. At its stand, Sabic highlights three of those applications.

When a client specifies a particular material in order to meet an environmental condition, the geometry will need to be adapted to match that choice. In some instances, the processing properties of the material can make or break a project, Johnson said.

In terms of geometry, there are basic questions about the mechanical needs that designers should ask: Is the design a moldable shape? Can the design hit the tolerances? Is there a way to open and close or eject the component from the mold? “Sometimes there’s the notion that because it’s small, it doesn’t need some of these [parameters], and yet, the traditional rules of injection molding still apply,” said Johnson.

His employer, Accumold, offers tooling, molding, packaging and metrology. The company operates from a 15-acre campus near Des Moines, Iowa, where its climate-controlled facility is boasts five clean rooms. Parts and components manufactured here are commonly measured in microns; they range from micro-optic molded lens arrays and small mold pupil dilators to micro rotor pinions and micro molded gears, as well as some with micro features that may be molded in and around existing components.

His colleagues might agree. “Some laws of physics like electrostatic induction, the triboelectric effect and Lenz Law can make a very small part not go where we need it to go, specifically, downward to the earth via gravity,” wrote his colleague Ron Baiotto in a company blog.

Johnson pointed out that design engineers are often able to design innovative products on screen, but that it does not necessarily translate in the molding process. “A design at the micro scale requires careful attention to what otherwise might not be a big deal for larger parts,” he said. “You can design things in CAD that you cannot mold.”

The company has had a bumpy ride recently, with its stock price plummeting by 68% this year, according to capital.com. Lucid Motors cut its production target in half for 2022, from 12,000 to 14,000 vehicles per year to 6,000 to 7,000, which was already a reduction from the original forecast of 20,000 cars this year. The company blamed supply chain and logistics issues for the scale back.

Nowhere is this more evident than in the medical devices industry, where efforts to optimize form factors—smaller, faster, cheaper—are limited only by the ability to innovate. Medication delivery systems, point of care delivery systems, microfluidics and electronic components make up only a smattering of examples.

Accumold also connects clients and resin suppliers so they can explore different materials that may be suited to the requirements of a unique component. “The aim is to give clients manufacturer-ready components,” he said.

The front-end module was molded in a single shot using Stamax long-glass-fiber polypropylene with organosheets. The pre-cut sheets were inserted into the mold, shaped, and combined with additional inserts and then overmolded to form a lightweight yet rigid composite. The process eliminated some assembly work and consequently lowered production cost, according to Sabic.

The upshot, according to Johnson, is that designing micro-molded components is situational and designers who are bound strictly by a set of rules will stymie their own capability and creativity, which will restrict the outcomes. The one micro-molding design rule worth noting, he said, is to “start with your ideal…it really comes down to what you are ultimately trying to accomplish.”

Whereas injection molding is a process for producing parts by injecting molten material into a mold, micro-injection molding focuses on producing small, high-precision parts and components with micron tolerances. In both cases, the process involves injecting molten plastic into the cavities of a steel mold. Once cooled, the parts are ejected.

And, rather than abandoning an idea that seems too complicated, Johnson’s advice is to discuss it with an expert micro molder. Understanding the material properties and the experience of matching the material with the appropriate geometry can make all the difference, he said.

Micro-injection molding also enables a high level of customization and complexity, making it suitable for specialized and miniaturized applications in the medical devices and automotive industries, where manufacturers must produce millions of parts with consistent levels of quality, precision and reliability.

Producing the highest-quality part requires understanding potential flaws that could affect its application, Johnson said. These details should be a part of the design for micro molding (DfMM) process at the beginning of every project. In essence, at Accumold, the DfMM process includes connecting the client with a project engineer, mold designer and a quality engineer who walk clients through the steps of the process. A considerable amount of time is spent on the front end of projects as a way to fully understand clients’ needs and requirements, he said.

So, there’s that. But how does the Lucid Air drive, you may be wondering? Dan Carney took it for a test spin last year; here’s what he had to say.

The expansion rate of miniaturized, high-precision engineering components debunks the claim that micro-molding is niche. Demand for wearable smart devices and implantable sensors enabled by small components with tight tolerances continues unabated.

A common query about micro-molding is whether it has any guidelines for micro-molding. A general guideline might include the following rules:

The battery module housing called for Lexan FR resin because of its stiffness-to-weight ratio, light weight, thermal and dimensional stability, and impact and ductile properties. The design integrates the electrical conductor directly into the housing in a one-shot molding process. No adhesives were needed, thus saving assembly time and improving quality and consistency, according to Sabic.

Consider PEEK (polyetheretherketone) as an example. Commonly used in implantable devices, this material is 30% glass fiber reinforced and pelletized for injection molding. The downside to using it is that it cannot fill ultra-thin areas. The same holds true for Ultem, another durable thermoplastic used in micro-optics applications, and a go-to for aerospace and automotive manufacturing.

As Machine Design’s content lead, Rehana Begg is tasked with elevating the voice of the design and multi-disciplinary engineer in the face of digital transformation and engineering innovation. Begg has more than 24 years of editorial experience and has spent the past decade in the trenches of industrial manufacturing, focusing on new technologies, manufacturing innovation and business. Her B2B career has taken her from corporate boardrooms to plant floors and underground mining stopes, covering everything from automation & IIoT, robotics, mechanical design and additive manufacturing to plant operations, maintenance, reliability and continuous improvement. Begg holds an MBA, a Master of Journalism degree, and a BA (Hons.) in Political Science. She is committed to lifelong learning and feeds her passion for innovation in publishing, transparent science and clear communication by attending relevant conferences and seminars/workshops.

The front trunk, or frunk, is a single-piece molded tub that combines thermoplastic elastomer with the aforementioned Stamax resin. Again, the production process eliminated several assembly steps compared with traditional approaches. In both of these applications, Stamax resin was selected because of its high stiffness-to-weight ratio, low warpage, adhesive properties, and impact performance.

Through a series of case studies, his presentation showed how knowledge of materials, processing knowledge, dimensional tolerances, thin walls, injection speed and assembly played into the design for micro-manufacturing (DfMM) process before components can be produced.