Engineering at the micron level

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 which is discussed by Brett Saddoris

In product development, the concept of ‘design for manufacturing’ (DfM) is well established. It is 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 moulded 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 — do not translate directly. They must be reinterpreted for a world where a 0.005-in 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 0.25mm) but strategically placed to avoid damaging fragile features or interfering with part function.

Even the choice of materials is not 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 are trying to push high-temperature polymers through a 0.1mm gate into a micro-scale cavity with extreme aspect ratios​​.

That is where true DfMM begins — with deep, early collaboration between designers and micro molding experts.

The case for early engagement

If there is one universal truth in micro molding, it’s this. The earlier the micro moulder is brought into the product development conversation, the better the results will be.

At Accumold, we often say we are not just manufacturers — we are consultants. We do not 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, mouldability, and downstream processing implications like assembly and inspection​​.

Designs can — and should — be challenged at this stage. Sometimes, we will 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 will encounter features that are simply impossible to mould 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 is 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 moulding, validation, and metrology — can introduce variability that jeopardises 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 moulding 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 cannot be realised 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 specialised metrology equipment and techniques that must be planned for at the design stage. If the part is not designed to be measurable, it is not manufacturable — at least not in a way that instills confidence.

Beyond the part

It is also important to recognise that DfMM does not end with geometry and material selection. It extends to the moulding 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 is 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​.

If you are 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 mould designs, the most advanced moulding 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 is why partner selection is so important. When evaluating a micro molder, do not 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 optimise 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 is measured in parts delivered — consistently, cost-effectively, and with the confidence that they will perform exactly as designed.

So, if your next innovation hinges on micro moulding, remember: do not just design for function. Design for micro manufacturing. The difference may be measured in microns — but its impact is enormous.

Brett Saddoris is Technical Marketing Manager at Accumold.