Micro injection molding produces very small plastic components and parts containing fine functional features. Applications can include miniature mechanisms, electronic components, and fluid-handling parts. The engineering challenge extends beyond making a small cavity: material preparation, dosing, filling, removal, and measurement all need to suit the scale of the product.
A useful project brief identifies what makes the component demanding. Low part weight, a narrow channel, and a tightly controlled assembly feature may require different tooling and inspection approaches.
How micro injection molding works
- Define the functional geometry. Identify critical features and tolerances, then design cavities, cores, gates, and vents around them. Tool manufacturing and inspection must be capable of resolving the required detail.
- Prepare the selected resin. Follow the material supplier’s drying and processing recommendations. The resin must meet both the application requirements and the filling demands of the geometry.
- Meter and inject the shot. An appropriately sized injection unit prepares and delivers a controlled quantity of melt. The mold is closed and clamped before injection, and process settings are developed for the actual resin and tool.
- Control cooling and release. After filling and packing, the component cools sufficiently for removal. Ejection must avoid damaging delicate features or distorting the part.
- Handle and verify the parts. Removal, separation, inspection, and packaging are planned as part of the production process, with methods suited to components that may be difficult to handle manually.
Why shot size and thermal control matter
The complete shot includes the part and any sprue or runner material. Selecting a machine only from the finished part weight can therefore miss an important part of the process. Conversely, an oversized injection unit may leave a small quantity of resin exposed to heat for too long or make dosing difficult.
Short flow paths, stable melt preparation, cavity venting, and suitable mold-temperature control support reliable reproduction of fine features. These priorities are described in ARBURG’s micro molding guide. They must be evaluated together rather than addressed by increasing injection pressure alone.
Equipment architectures vary. For example, WITTMANN describes a two-stage screw-and-plunger approach that reduces the melt volume between the injection plunger and the component. The choice between dedicated micro equipment and a suitably configured conventional press should follow the shot, tooling, and handling requirements.
Material and quality decisions
A micro part does not automatically require a special polymer. Select the specific grade for its functional properties, processing behavior, and any applicable product requirements. A familiar resin family name is insufficient to establish that a very thin section or fine feature will fill consistently.
Write a measurement plan before committing to the tool. Specify the datums, critical dimensions, inspection method, and acceptance criteria. A dimension that is difficult to measure repeatedly can become a production bottleneck even if initial samples appear satisfactory.
Handling also deserves attention. Decide how parts will remain identified through removal and inspection, whether cavities need separate records, and how packaging will protect the features that matter to the final assembly.
Benefits and economic limits
Once a suitable tool and process are established, molding can reproduce complex small geometries repeatedly and support volume production. It may reduce the need to machine individual features into every component.
Precision tooling, process development, automation, and inspection create upfront costs. For a short prototype run, machining or another route may be more economical. Compare total program cost using realistic quantities, acceptable yield, inspection effort, and the expected life of the design.
Small size does not remove the need for a complete manufacturing strategy. Reliable micro molding depends on matching fine geometry with controlled melt delivery, suitable ejection, repeatable measurement, and handling that protects the finished features.
