Micro Injection Molding

Machine Architecture

Traditional reciprocating screws cannot maintain adequate residence time or shot-volume control when metering fractions of a gram, leading to severe thermal degradation of the polymer melt. Micro injection molding systems solve this limitation by decoupling the plasticizing step from the injection phase, using an extrusion screw to melt the polymer and a separate micro-injection plunger to meter the shot. Plungers with diameters between three and eight millimeters achieve linear positioning accuracy within micrometers, providing exact volumetric dosing for minute cavities.

Ultra-high injection velocities exceeding one thousand millimeters per second overcome instant freeze-off within thin-wall features. Evacuation systems draw vacuum on the mold cavity before injection to eliminate air entrapment and prevent diesel effects in micro features.

Process Stability

Thermal stability throughout the melt delivery system dictates part-to-part weight repeatability across extended production campaigns. Because runner volume frequently exceeds the total component volume by an order of magnitude, runner optimization through micro-hot-runner designs or direct gate plungers is necessary to limit material waste. Variothermal mold control heats the cavity above the resin melt temperature during injection and rapidly cools it before ejection, preventing frozen layers from blocking fine channel filling.

Process sensors monitor cavity pressure profiles at sub-millisecond intervals to verify complete feature replication. Slight fluctuations in melt temperature or ambient factory humidity alter resin viscosity, producing immediate short shots or excessive parting line flash.

Production Scale

Transitioning from single-cavity development presses to high-cavity automated manufacturing cells exposes tooling to severe thermal fatigue and mechanical wear. Prototype runs operating on slow cycle times fail to replicate the dynamic thermal loads, mechanical friction, and degassing challenges encountered in continuous multi-cavity operations. Premature release of tooling into production without verifying optical dimensional stability results in high scrap rates and frequent machine downtime for gate cleaning.

Optical automated visual inspection systems integrated into the handling robot verify feature completeness prior to packaging. The micro injection molding process delivers repeatable structural integrity only when mechanical dosing, mold evacuation, and variothermal cycles operate in absolute synchronization.