Brett Saddoris, Technical Marketing Manager, Accumold
In product development, the concept of “design for manufacturing” (DfM) is well established. It’s a guiding principle that ensures a product’s geometry, material selection, and feature set are compatible with the realities of manufacturing. But when you scale that concept down to the micro level for plastic parts — which can weigh less than a fraction of a gram and feature tolerances are measured in microns — DfM evolves into something far more nuanced — Design for Micro Molding (DfMM).
And at this scale, the margin for error is virtually non-existent.
At Accumold, we’ve spent decades mastering the art and science of micro injection molding. But one thing has become increasingly clear over the years, no matter how advanced the equipment or how skilled the technicians, the long-term success of any micro molded product is determined before the first shot of resin ever hits the mold. It begins with thoughtful, collaborative design.
RETHINKING DESIGN FUNDAMENTALS FOR MICRO SCALE
DfMM demands that engineers rethink some of the most basic assumptions that apply at the macro scale. Traditional part design strategies — gate placement, draft angles, parting lines, even wall thickness — don’t translate directly. They must be reinterpreted for a world where a 0.005″ shift can render a feature unusable or make a part unmoldable altogether.
For example, gating options at the micro level are drastically reduced. Typical gate diameters might range from 60 to 200 microns. Ejector pin placement — an afterthought in many traditional mold designs — becomes a critical constraint, as pins must be not only tiny (sometimes as small as 0.25 mm) but strategically placed to avoid damaging fragile features or interfering with part function.
Even the choice of materials isn’t as simple as it might seem. Engineers often consult datasheets and choose materials that perform well in macro applications — PEEK, Ultem®, LCP, carbon-filled nylons, and others. But many resin data sheets are based on test bars molded in large-scale tools with large gates. That data is often misleading when you’re trying to push high-temperature polymers through a 0.1 mm gate into a micro-scale cavity with extreme aspect ratios.
That’s where true DfMM begins — with deep, early collaboration between designers and micro molding experts.
THE CASE FOR EARLY ENGAGEMENT
If there’s one universal truth in micro molding, it’s this. The earlier the micro molder is brought into the product development conversation, the better the results will be.
At Accumold, we often say we’re not just manufacturers — we’re consultants. We don’t just build tools and run parts; we partner with design teams to guide them through the micro manufacturing process, from CAD file to finished, validated part. That partnership starts with candid, pragmatic design reviews that assess part feasibility, material compatibility, moldability, and downstream processing implications like assembly and inspection.
Designs can — and should — be challenged at this stage. Sometimes, we’ll work with customers who are convinced their design is un-moldable. But with a few subtle changes to wall thickness, draft, or gating, we can turn a problematic concept into a manufacturable part. Other times, we’ll encounter features that are simply impossible to mold or measure. In those cases, early engagement allows us to recommend changes before they cascade into tooling rework or program delays.
This design-stage collaboration is not just useful — it’s mission critical.
DFMM AS A RISK MITIGATION STRATEGY
From the outside, it can be easy to underestimate just how much risk is embedded in micro-scale product development. The parts may be small, but the stakes are large — especially for medical, aerospace, and microelectronics applications where failure is not an option.
Each stage of development — from part design and tooling, to molding, validation, and metrology — can introduce variability that jeopardizes the success of the project. One of the best ways to mitigate those risks is through comprehensive DfMM that bakes in quality from the start.
Consider tooling. A micro molding tool is not a scaled-down version of a conventional mold. It is an entirely different engineering challenge. Core pins, for example, can be thinner than a human hair and must withstand extreme pressures without deflecting. Without precision tooling — fabricated in-house under tight control — even the best part design can’t be realized with any consistency.
Or take measurement. In many cases, the features we mold are too small to be measured with conventional tools. Validating parts at this level requires specialized metrology equipment and techniques that must be planned for at the design stage. If the part isn’t designed to be measurable, it’s not manufacturable — at least not in a way that instills confidence.
BEYOND THE PART — DFMM INCLUDES PROCESS AND PEOPLE
It’s also important to recognize that DfMM doesn’t end with geometry and material selection. It extends to the molding process, automation strategies, and even the people involved in the project.
Scaling a part from prototype to production is not a plug-and-play exercise. At micro scale, the smallest process variations — residence time, melt temperature, injection velocity — can influence shrinkage, flash, or parting line mismatch. If the design hasn’t accounted for these sensitivities, problems emerge when volumes ramp up.
That’s why vertical integration matters so much in micro molding. At Accumold, our engineers, toolmakers, quality specialists, and automation experts work under the same roof, in constant collaboration. This allows us to test, refine, and perfect the process early — not after a program is already in crisis.
And it enables us to take projects from single-cavity prototype tools to 16- or 32-cavity production molds that run millions — or even billions — of parts per year, all while maintaining tight quality controls.
CHOOSE THE RIGHT PARTNER — AND ENGAGE EARLY
If you’re developing a product that will rely on micro injection molding, the message is clear, DfMM is not optional. It is the foundation upon which your program’s success will rest.
The most sophisticated mold designs, the most advanced molding presses, the cleanest cleanroom — none of these assets can compensate for a flawed design that wasn’t engineered for micro manufacturing from the outset.
That’s why partner selection is so important. When evaluating a micro molder, don’t just ask about press size or ISO certifications. Ask about their ability to support DfMM. Do they have in-house toolmakers? Can they simulate flow and optimize part design? Can they validate, automate, and scale? Do they see themselves as a partner — or just a vendor?
At Accumold, we believe the answer should be clear. Because in this business, success is not measured in parts molded. It’s measured in parts delivered — consistently, cost-effectively, and with the confidence that they’ll perform exactly as designed.
So, if your next innovation hinges on micro molding, remember:, don’t just design for function. Design for micro manufacturing. The difference may be measured in microns — but its impact is enormous.
