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Hot Melt Nozzle Clogging, Charring and Smoking

Clogged nozzles are usually caused by char: glue degraded by heat, oxygen, contamination and time. Dust and debris in the tank, long idle periods at full temperature and a near-empty tank all speed it up. Smoking or darkening glue is a sign of overheating or oxidised glue. Keep the tank covered and at least half full, use standby (setback) temperature when idle, filter, and replace charred glue. [1][2][3]

Sources: H.B. Fuller / Adhemelt Hot Melt Preventative Maintenance (PDF)；H.B. Fuller Packaging Adhesive Best Practices (PDF)；H.B. Fuller Hot Melt Troubleshooting Guide (PDF)

Phenomenon / Likely cause / Fix

Phenomenon	Likely cause	Fix
Nozzle blocks, bead skips	Char particles from degraded glue	Use tank and inline filters; purge through the tank drain port monthly [1]
Black specks in the bead	Char / contamination in tank	Clean out the tank interior every six months; replace compromised adhesive [1][3]
Glue darkens, smokes, smells	Temperature too high or glue oxidised	Check thermostat, reduce temperature, use setback or turn off when idle; replace glue and cover reservoir [3]
Char builds faster than expected	Tank lid open, dust falling in; tank run near-empty	Keep lid closed; keep tank at least half full [2]

Nozzle blocks, bead skips

Likely cause: Char particles from degraded glue
Fix: Use tank and inline filters; purge through the tank drain port monthly [1]

Black specks in the bead

Likely cause: Char / contamination in tank
Fix: Clean out the tank interior every six months; replace compromised adhesive [1][3]

Glue darkens, smokes, smells

Likely cause: Temperature too high or glue oxidised
Fix: Check thermostat, reduce temperature, use setback or turn off when idle; replace glue and cover reservoir [3]

Char builds faster than expected

Likely cause: Tank lid open, dust falling in; tank run near-empty
Fix: Keep lid closed; keep tank at least half full [2]

How this relates to Zhishang machines: The Zhishang brochure states: "Glue nozzles are covered by lifetime repair and replacement (trade-in). The nozzle is our own developed brand, with invention and utility-model patents." Maintenance above still applies. See our hot-glue dispensing machines.

Related machines

Zhishang machines dispense glue along a programmed path, with a 3-10MM glue width and 0.6MPa working air pressure (product brochure). Specifications are for reference only; final specifications are subject to our quotation.

Inline with a box line (hot melt)