edge curling troubleshooting

  No manufacturing process is perfect. Even with modern extrusion lines and strict quality controls, polypropylene spunbond nonwoven fabric can occasionally have defects. The difference between a good supplier and a great one is not whether problems occur — but how quickly they are identified, understood, and fixed. In this article, we'll walk through the most common quality issues in PP spunbond nonwoven, what causes them, and — most importantly — how to solve them. Whether you're a buyer, a converter, or a fellow manufacturer, this guide will help you spot problems early and work with your supplier to resolve them. 1. Pinholes & Visible Holes The Problem: Small, visible holes or thin spots in the fabric that allow light to pass through. These compromise barrier properties, tear strength, and appearance. Common causes: Contamination in the polymer melt (dust, degraded resin, or char) Clogged or partially blocked spinneret holes Inconsistent polymer flow due to pump or temperature fluctuations Foreign particles on the forming belt Solutions: Prevention: Install high-quality filtration systems and perform regular spinneret cleaning Inspection: Use online optical inspection (light table or laser scanners) to detect pinholes during production Fix: Adjust polymer melt temperature and pump speed to ensure consistent flow Quality check: Always hold a sample roll up to light or use a light table before shipment 2. Thickness Variation (GSM Fluctuation) The Problem: The fabric weight (GSM) is not consistent across the roll or along the length. Some areas are heavier, some lighter. This leads to uneven strength, poor print, and customer complaints. Common causes: Fluctuations in the extruder screw speed or polymer pump output Uneven cooling (quench air) — filaments cool at different rates Vacuum pressure variations on the forming belt Calender roller temperature or pressure inconsistency Solutions: Stabilize melt flow: Use a high-quality metering pump and maintain consistent extruder temperature Balance quench air: Ensure airflow is uniform across the full width of the web Maintain vacuum: Clean forming belts regularly and check for blockages Calender control: Monitor roll temperature and pressure across the width 3. Low Tensile Strength (Fabric Tearing Too Easily) The Problem: The fabric does not meet the specified tensile strength — it tears too easily in machine direction (MD) or cross direction (CD). This compromises durability for bags, covers, and gowns. ⚠️ This is one of the most common — and most frustrating — issues in the industry. Root causes of low tensile strength: A. Incorrect Basis Weight (GSM Too Low)The fabric is simply too light for the application. A 50gsm fabric will never have the tensile strength of a 100gsm fabric. If the supplier is offering "high strength" at a very low GSM, the numbers may not add up. Strength requires polymer mass — there's no shortcut. B. Insufficient PP Content — Excessive FillersSome manufacturers reduce cost by adding fillers (e.g., calcium carbonate, talc) to the polymer. This lowers the actual PP content per square meter. Fillers do not bond or provide strength — they weaken the fabric. A roll with 30% filler will have roughly 30% lower strength than a 100% virgin PP roll of the same GSM. C. Low-Quality PP Resin from Substandard SuppliersNot all PP resin is the same. Off-spec resin, recycled resin of unknown origin, or resin with inconsistent MFI (melt flow index) can cause weak filaments. Some small, unregulated suppliers offer resin at very low prices — but the resulting fabric fails tensile tests consistently. Quality resin costs more for a reason. D. Poor Process ParametersEven with good resin, a manufacturer that doesn't adjust its production parameters carefully will produce weak fabric. This includes: Insufficient filament drawing (stretching) Under-bonding or over-bonding at the calender Incorrect quench air temperature and speed Extruder temperature profiles that degrade the polymer A manufacturer must actively monitor and adjust these parameters during the run — not just set them once and walk away. Red flag: If a supplier offers spunbond fabric at a price that seems too good to be true — it probably is. The savings likely come from fillers, low-grade resin, or corners cut in production. The cost of field failures and customer complaints will far outweigh the upfront savings. 4. Uneven Fabric Surface (Waviness / Buckling) The Problem: When laid flat on a table or on a converting machine, the fabric does not lie smoothly. It shows waves, ripples, or buckling — especially near the edges. This is often called "wavy edges," "baggy fabric," or "camber." Why this matters: An uneven surface prevents smooth printing, causes misalignment in bag-making, and creates wrinkles in laminated products. In automated lines, it can cause jams and rejects. Common causes: Uneven winding tension — if tension is too high in the middle and low at the edges, the fabric will buckle Calender roll temperature variation — hot spots or cold spots create differential shrinkage Inconsistent filament lay-down — if the forming belt has uneven vacuum or the web is laid unevenly, the fabric will have built-in stress Excessive stretching during rewinding — especially for lightweight fabrics Moisture absorption or release — PP doesn't absorb water, but temperature changes during shipping can create temporary surface distortion Solutions: Winding tension control: Use automatic taper tension systems that reduce tension as roll diameter increases Calender maintenance: Ensure roll surfaces are clean, smooth, and uniformly heated Web formation: Clean forming belts and check vacuum uniformity across the width Slitting and rewinding: Use sharp, aligned blades and moderate tension Storage: Keep rolls on flat surfaces; avoid stacking heavy rolls on top of each other 5. Edge Curling (Dog-Ear / Roll Edge Lift) The Problem: The edges of the fabric curl upward or inward, making it difficult to unwind, feed through machines, or print on. This is especially problematic for bag making and converting lines. Common causes: Uneven tension across the web during winding Edge trimming that creates uneven edge stress Calender pressure being higher at the edges than the center Over-tight winding on the core Solutions: Calender adjustment: Ensure even nip pressure across the full width Winding tension: Use tapered tension control — reduce tension as the roll diameter increases Edge trimming: Trim edges cleanly and consistently to avoid stress points Slitting: Use sharp, properly aligned slitting blades to avoid edge distortion 6. Static Charge Build-Up The Problem: The fabric generates static electricity during unwinding or converting. This attracts dust, causes layers to stick together, and can interfere with automated equipment or electronic components. Common causes: Polypropylene's natural insulating properties Low humidity in the production or converting environment High-speed unwinding or slitting creates friction and static Solutions: Antistatic additives: Add internal antistatic agents (e.g., glyceryl monostearate) during extrusion Surface treatment: Apply topical antistatic finishes Environmental control: Maintain 45–55% relative humidity in the production and converting areas Grounding equipment: Use anti-static bars or ionizing air guns on unwinding and slitting machines 7. Uneven Width / Telescoping Rolls The Problem: The roll is not uniform — layers slide sideways (telescoping) or the width varies along the roll length. This makes it impossible to run on automated lines. Common causes: Incorrect winding tension Misaligned edge guides or slitting position Inconsistent fabric width from the production line Vibration in the winder Solutions: Precise edge guiding: Use automatic edge guide systems (with infrared or ultrasonic sensors) Controlled winding tension: Use taper tension to reduce tension as roll diameter grows Regular calibration: Ensure slitting and winding equipment are properly aligned Monitor width: Use online width measurement to catch deviations 8. Surface Defects — White Spots, Streaks, or Dark Specks The Problem: Visible blemishes on the fabric surface — white spots (unmelted resin), dark specks (carbonized polymer or contaminants), or streaks (uneven melt flow). These ruin print quality and appearance. Common causes: Unmelted resin pellets (white spots) from inadequate extrusion temperature Carbon buildup on the spinneret or die (dark specks) Contamination in the raw material Uneven melt flow due to temperature fluctuations Solutions: Precise temperature control: Maintain consistent extrusion and die temperatures Regular cleaning: Schedule spinneret and die cleaning to prevent carbon buildup Quality raw material: Source high-quality virgin resin from reputable suppliers Filtration: Use fine-mesh filters (e.g., 40–60 mesh) to remove contaminants Quick Troubleshooting Reference Quality IssueLikely Root CauseQuick Check Pinholes Clogged spinneret or contamination Hold fabric to light; check for repeats GSM variation Pump fluctuation or quench air imbalance Weigh samples from edge, center, edge Low tensile strength Low GSM, fillers, poor resin, or bad process parameters Test MD and CD; check ash content for fillers Uneven surface Winding tension or calender temperature variation Lay flat on table; check for waves Edge curling Uneven calender pressure or winding tension Lay flat; measure curl height Telescoping roll Winding tension or edge guide problem Check roll ends; measure width   The Bottom Line Quality issues in spunbond nonwoven are preventable, detectable, and solvable. The key is having a supplier that understands the root causes and has the systems in place to prevent them. Most quality problems trace back to three things: Cheap materials — fillers, low-grade resin, recycled content Poor process control — manufacturers who don't monitor or adjust parameters Choosing a supplier who invests in quality resin, careful production will save you headaches — and money — in the long run. Looking for a reliable supplier of PP spunbond nonwoven with consistent quality? We manufacture single-layer spunbond from 10gsm to 250gsm, with stringent quality controls, good quality new virgin PP resin, and 22 years manufacture experience at nonwoven production. Contact us for samples or a quote – Quality you can rely on, from roll to roll.