Medical and electronic cleanroom hot runner workshops control air particulate concentration strictly, yet tiny suspended dust, plastic filler powder and mold release agent aerosol particles still accumulate on thermocouple plugs, wire shielding braids and sensing heads, triggering hidden signal interference and measurement drift. Unlike ordinary workshop oil mist pollution, cleanroom dry dust forms conductive particle layers under high-temperature hot runner radiation, creating unique interference modes that require dedicated dust prevention maintenance standards.
Three interference mechanisms caused by cleanroom dust accumulation.
1. Plug pin conductive dust bridging: Micro-conductive carbon and metal filler dust settles between two-pin plug gaps; under temperature difference alternating condensation, dust absorbs trace water vapor to form temporary conductive paths, generating intermittent short-circuit and temperature jump alarms. Cleanroom dust has no heavy oil adhesion, so the conductive layer is thin and intermittent, making faults hard to reproduce during offline inspection.
2. Shielding braid dust insulation failure: Non-conductive plastic dust clogs gaps in metal shielding braids, reducing electromagnetic noise absorption capacity. External servo motor magnetic field penetrates incomplete shielding, causing irregular temperature fluctuations of ±1~2℃ during continuous molding cycles.
3. Sensing head dust thermal barrier: Dry polymer dust accumulates on manifold flat-head and nozzle probe surfaces, forming a thin low-thermal-conductivity layer after high-temperature baking, leading to consistent negative temperature drift and slow response speed. Optical transparent product molds suffer the most obvious quality defects from this drift, including lens haze and micro-bubbles.
Differences between cleanroom dust and ordinary workshop contaminants. General industrial workshops produce oil-mixed carbon sludge that adheres firmly to thermocouple surfaces; cleanroom dust is dry, loose and easily blown off by air guns, but re-accumulates rapidly within 24 hours of production resumption. Dust in medical cleanrooms contains biocompatible plastic filler mineral powder, which does not corrode metal sheaths but forms persistent thermal insulation layers once carbonized under hot runner temperature. Electronic workshop dust contains conductive metal cutting powder, which poses higher short-circuit risk than non-conductive medical plastic dust.
Cleanroom dedicated dust prevention and cleaning specifications.
1. Daily on-machine dry dust removal (per shift end): Use low-pressure dry nitrogen air gun (pressure ≤0.2MPa) to blow dust off thermocouple plugs, wire harnesses and sensing heads; prohibit compressed workshop air with oil moisture content. Cover junction box openings with dustproof rubber caps during production standby to block suspended dust settling inside.
2. Weekly disassembly precision cleaning: Remove all thermocouple plugs and wipe pin surfaces with lint-free IPA alcohol cleanroom wipes; fully extract probe and flat-head sensors to wipe dust residue off contact surfaces, then blow dry with nitrogen before reinstallation. Do not use ordinary cotton cloth that sheds fiber particles, which will become new dust contamination sources.
3. Mold structural dust isolation optimization: Design fully sealed mold junction boxes with dustproof gaskets; route thermocouple wires through closed wiring channels instead of exposed open layout. Install small dust baffles beside hot runner measuring points to block flow channel plastic dust from drifting onto sensing heads during molding.
4. Thermocouple material selection for cleanrooms: Select smooth electropolished sheath and nano anti-stick coated sensing heads to reduce dust adhesion force; use fully enclosed bayonet sealed connectors instead of open friction two-pin plugs that trap dust easily.
Cleanroom maintenance forbidden operations. Never use water-based cleaning agents to wash thermocouple assemblies-residual moisture combined with dust creates permanent conductive residue. Avoid disassembling thermocouple wiring during production running to prevent massive cleanroom dust stirred up by operation from covering exposed pins and sensing heads. Schedule all thermocouple deep cleaning during off-shift production downtime when cleanroom air circulation dust concentration is lowest.
