Common quality defects in extruded products fall into appearance, dimensional accuracy, performance, and other categories. Troubleshooting by category helps you find the cause and take action faster. We can machine screws, barrels, dies, and mandrels from customer drawings, in single pieces or small batches.
1. Appearance defects
1.1 Bubbles or silver streaks on the surface
Causes: Moisture in the raw material, barrel temperature too low so the melt is not fully plasticized, extrusion speed too high, or poor die venting.
Solutions: Dry the raw material in advance to a moisture content of no more than 0.02%. Raise barrel zone temperatures as needed. Adjust extrusion speed to match melt flow. Clean die vent grooves and increase vent area as needed.
1.2 Flow marks or ripples on the surface
Causes: Uneven melt temperature, large screw speed fluctuation, uneven die gap, or uneven raw material mixing.
Solutions: Extend barrel holding time to stabilize melt temperature. Check and tighten the screw drive to remove speed fluctuation. Calibrate the die gap to make it uniform. Re-mix the material to keep components consistent.
1.3 Black spots or impurities on the surface
Causes: Impurities in the raw material, decomposed material buildup in the barrel, or metal chips from screw and barrel wear.
Solutions: Filter the raw material and add an inline screen. Clean dead spots in the barrel regularly. Replace severely worn screw and barrel components. Hansheng Automation can machine replacement screws and barrels from customer drawings.
2. Dimensional accuracy defects
2.1 Uneven wall thickness
Causes: Die concentricity deviation, unstable extrusion speed, or haul-off speed fluctuation.
Solutions: Adjust the die center to align with the machine axis. Stabilize screw speed to keep output consistent. Calibrate the haul-off device for constant speed.
2.2 Dimensions out of tolerance
Causes: Mismatch between haul-off speed and extrusion speed, melt density change from barrel temperature fluctuation, or die wear.
Solutions: Adjust the haul-off ratio to a stable range, usually 1.05 to 1.2 times. Stabilize barrel heating temperature. Replace worn die and mandrel components.
3. Performance defects
3.1 Insufficient product strength
Causes: Poor plasticizing leads to insufficient molecular orientation, cooling speed too fast, or raw material degradation.
Solutions: Raise screw speed and barrel temperature as needed to ensure full plasticizing. Adjust cooling water temperature and speed to match process requirements. Replace degraded material and clean residual material from the barrel.
3.2 Product cracking
Causes: Melt temperature too high causing material degradation, insufficient cooling leaving internal stress, or too much filler in the formula.
Solutions: Lower the rear barrel temperature to avoid overheating. Extend cooling and shaping time or lower cooling water temperature. Adjust filler ratio back into the process range.
4. Other common defects
4.1 Product cracking
Causes: Haul-off tension too high, sharp edges or burrs on the die, or uneven cooling.
Solutions: Reduce haul-off speed or adjust haul-off tension. Polish the die to remove sharp edges and burrs. Arrange cooling devices evenly to keep cooling temperature consistent.
4.2 Unstable output
Causes: Poor screw feeding, barrel temperature fluctuation, or material bridging.
Solutions: Check the feeding device to ensure smooth feed. Stabilize heating system temperature. Add a small amount of lubricant to improve material flow and prevent bridging.
Beyond extrusion equipment, our precision custom machining capability is not limited to one industry. Hansheng Automation can machine non-standard metal parts for medical devices, food packaging machinery, printing equipment, and tobacco packaging machinery from customer drawings. We also machine yacht components, RC car components, and specialized parts for filling machinery. We focus on build-to-print custom machining and produce single pieces or small batches according to customer drawings. We do not sell complete machines.
