Micro moulding is injection moulding at the small end of the scale: tiny parts and fine features where precision is everything. Here is what is genuinely achievable, and where it stops.
Moulding at a Tiny Scale
Micro moulding produces very small plastic components, or parts carrying features so fine that a conventional moulding setup cannot fill or eject them reliably. Think small clips, gears, connectors, microfluidic detail, medical micro-components and precision detail parts.
At this scale small variations have a large effect, so tool precision and process control matter more than they do on a normal part.
How Small Is Small?
Numbers are more useful than adjectives here, so these are ours. We have moulded parts down to around 0.06 g, held 0.1 mm wall sections and formed 0.1 mm features such as holes, ribs and bosses. On the right material and geometry we have reliably held 0.01 mm.
Those are real production figures rather than a brochure claim, and they are not universal. What any particular part can achieve depends on its geometry, its material and which dimensions actually matter.
Why It Is Specialised
Filling a tiny cavity, packing it out, then ejecting a delicate part without damaging it takes tooling designed for the job and a tightly controlled process. Two things decide the outcome, and both happen before the machine is switched on.
The first is part design. A 0.1 mm wall has to be fed and packed before the material freezes off, and thin sections freeze very fast. The second is material selection: flow, shrinkage and stiffness determine whether a fine feature forms at all. When small features do not fill, the fix is nearly always in one of those two, not in the machine settings.
That is also why it pays to get design-for-manufacture feedback before the tool steel is cut rather than after the first trial disappoints.
The Machine Matters Too
A very small part made on a machine sized for much larger work tends to produce an unstable process, because the shot is a tiny fraction of the barrel. Dedicated small-shot machines exist for this reason. We run micro work on a BOY XS, an 11 ton machine built for small shots.
What Is It Used For?
Micro moulding is common in medical devices, diagnostics and laboratory products, electronics, and detailed products such as jewellery components, anywhere small, precise plastic parts are needed.
Materials matter as much as size in those sectors. Cyclic olefin copolymer (COC) is used where optical clarity and fine detail replication are needed, such as microfluidics and cuvettes. Medical-grade polypropylene, acetal (POM) and soft-touch TPV cover syringes, closures, device components, grips and seals. At the other extreme, heavily filled compounds such as a 90% copper-filled nylon are used where a small part needs real density.
Where Micro Moulding Stops
Defining the edge is as useful as defining the capability. Below roughly 0.1 mm features or 0.05 g, you are into nano moulding, which is a different discipline with different equipment. Some polymers are also a poor fit for small-scale work with standard tooling. We do not run PEEK, for example.
A good moulder will tell you when your part sits outside what they can do, rather than finding out after a tool is cut.
What It Costs and How Long It Takes
Micro tooling starts at around £2,500 and typically takes 4 to 6 weeks to design and cut. Once a tool is approved, first-off parts usually follow within 5 to 10 working days.
Because tooling is a one-off investment and the cost per part is low, quantity is what decides whether micro moulding makes sense. Below about 500 parts the tooling rarely pays back against machining or 3D printing. See injection moulding vs 3D printing for that comparison.
Inspecting Parts You Can Barely See
A 0.1 mm feature is not something you check with a rule and an opinion. Optical inspection equipment is what makes small features measurable, and logged dimensional and visual checks with full traceability are what make the result defensible later. Ours sit under our ISO 9001 quality system.
Repeatability Is the Point
The purpose of micro moulding is to reproduce fine detail consistently, part after part, which comes from precision tooling and a controlled process. See our micro moulding service for the full capability list, or send us the part and we will tell you honestly whether it is mouldable.
Sources & Further Reading
For independent background on the process, see the British Plastics Federation's guide to injection moulding and the overview on Wikipedia.