Control very small shot weights
Metering, residence time, runner ratio and process stability must be matched to part weight. Small variations can immediately become visible or functionally relevant.
Micro Injection Moulding
Micro Injection Moulding for Small, Function-Critical Plastic Parts
When micro injection moulding is the right solution
Micro moulding is appropriate for parts with very small dimensions, low shot weights, thin walls, fine snap-fit or guide features, microstructures or close fits.
The challenge is not size alone. Even minor flash, a slightly misplaced gate, insufficient venting or a damaged edge can have a greater effect on function than on larger moulded parts. Part geometry, tooling detail, material flow and part removal therefore need to be assessed together from the outset.
Metering, runner and cavity in balance
In micro parts, the runner may account for a large share of the total shot weight. Residence time, melt condition and metering accuracy therefore have a significant effect on surface quality, filling and dimensional accuracy.
On the tooling side, short controlled flow paths, effective venting, precise cavities, stable mould inserts and gentle demoulding are critical. The engineering also has to address how the part is collected, inspected and packaged safely after ejection.
Define inspection and handling early
The smaller the part, the harder it becomes to inspect it economically. Not every characteristic can be measured reliably with standard methods, and handling the samples can affect the result.
BERGER therefore defines early which characteristics are function-critical, how they can be inspected and which inspection strategy suits the production volume. For micro parts, a realistic inspection concept is essential for production readiness.
Critical points in micro injection moulding
Fully reproduce fine structures
Thin walls, free-form surfaces, snap-fit features and microdetails require precise tooling, effective venting and controlled mould temperature.
Control demoulding and subsequent handling
Small parts are sensitive to ejector forces, electrostatic effects, uncontrolled placement and mechanical loads. Part removal, transport, inspection and packaging therefore form part of the process concept.
Define an appropriate inspection scope
Function-critical characteristics must be assessed in a verifiable way. This requires suitable methods and an inspection strategy that remains technically meaningful and economically viable.
Bringing delicate parts into stable production
The key is not the small part size alone, but reliable function at that scale. Geometry, tooling, process, handling and inspection must work together so that a delicate sample can be reproduced reliably in production.
1
Assess geometry and function
BERGER identifies the details that determine function and assesses the risks associated with wall thickness, flow path, flash, demoulding and handling.
2
Align tooling and process with microfeatures
Gating, cavity, venting, temperature control, metering and demoulding are matched specifically to very small part sizes.
3
Validate inspection and production
Approval criteria, measuring methods and process windows are defined so that part function can be verified throughout production.
Micro injection moulding proves its value in fine functional details
Micro moulding is not judged by part size alone, but by whether the required function can be reproduced reliably at that scale. Fine contours, fits, snap-fit features and thin-walled geometries must remain stable across batches and production runs.
Questions about micro injection moulding
Above all, the relationship between shot weight, runner, tooling details and handling: small deviations have a much greater effect on function and process stability in micro parts.
Very small functional parts, delicate technical components, thin-walled geometries or parts with fine contours where dimensional stability and repeatability matter.
Small parts can be damaged, mixed up or moved uncontrollably more easily during demoulding, conveying, inspection or packaging. The process chain therefore needs to be planned early.
Especially with micro parts, it is worth reviewing geometry, material, tooling concept, handling and inspectability before the mould is built.
There is no fixed lower limit. What matters is the combination of shot weight, wall thickness, flow path, material, demoulding and inspectability. The practical limit is always part-specific.
