I. Poor Roll Shape: "Chrysanthemum Pattern" or "Star Shape"
Problem Manifestation: The end face of the roll exhibits an inwardly concave "chrysanthemum pattern" or an outwardly convex "star shape."
Root Cause: "Chrysanthemum pattern" is often caused by excessive taper, resulting in rapid decrease in outer layer tension, insufficient interlayer support, and roll collapse.
"Star shape" is caused by insufficient taper, resulting in an overly tight outer layer, concentrated radial pressure, and forcing the material to bulge outward.
Impact: Irregular roll shape affects stacking and transportation, and is prone to deviation and material breakage during unwinding.
II. Inner Layer Crushing or Core Collapse
Problem Manifestation: The inner layer material of the roll is deformed by compression, and the core is bent or even broken.
Root Cause: Initial tension set too high, and insufficient taper attenuation, resulting in excessive radial pressure on the inner layer.
According to mechanical formulas, the internal pressure of the roll material is directly proportional to the tension and inversely proportional to the square of the roll diameter. Therefore, the inner layer pressure is much higher when fully wound than when empty.
Impact: Damage to material physical properties, such as stress lines on optical films and deformation of the carbon ribbon base film, severely affecting subsequent use.
III. Loose Outer Layer and Interlayer Slippage
Problem Manifestation: Loose outer layer of the roll material, resulting in "loosening" or "serpentine deviation" during unwinding.
Root Cause: Taper coefficient set too high, resulting in excessively rapid tension attenuation; Zero-speed tension not maintained (tension returns to zero when the machine stops), leading to loose winding.
Impact: Unstable unwinding, prone to material breakage, especially at high-speed lamination or slitting lines.
IV. Material Breakage During Roll Changes
Problem Manifestation: Frequent film or tape breakage during dual-station shaft changes.
Root Causes: "Soft Start" function not enabled: Tension is directly applied to full value during roll change. Dual-station tension output is asynchronous, or memory function is not enabled.
Impact: Increases scrap rate and reduces production efficiency, especially noticeable with thin materials (e.g., 0.012mm optical film).
V. Large Tension Fluctuations and Unstable Operation
Problem Manifestations: Tension curve oscillates; material shakes or drifts during operation.
Root Causes: Roll diameter detection device (e.g., proximity switch) is not calibrated, causing the controller to misjudge the current roll diameter.
Floating roller jamming or abnormal sliding resistance: Unable to provide real-time feedback on tension changes.
Impact: Tension control failure easily leads to wrinkling, stretching, or material breakage.
VI. Uneven Unwinding and Rewinding Tension
Problem Manifestations: Material exhibits serpentine deviation, wrinkling, or stretching in the traction zone.
Root Cause: Unwinding tension is greater than or equal to winding tension, disrupting the tension gradient.
The correct ratio should be unwinding tension : winding tension = 1 : 1.05~1.1.
Impact: The material is subjected to reverse tension, leading to interlayer misalignment or breakage.
VII. Inappropriate Material Compatibility, "One-Size-Fits-All" Parameter Application
Problem Manifestation: Using the same set of parameters for different materials results in film wrinkling, fabric indentation, and paper crushing.
Root Cause: The tension range and taper curve were not adjusted according to material characteristics.
For example, for films (PET/EVA), a tension of 2~5kg is recommended, while for fabrics it should be ≤3kg. Sensitive materials require closed-loop control.
Impact: Large fluctuations in finished product yield and extended equipment setup time.
