Troubleshooting guide for PP Multifilament Spinning Applications
PP Multifilament Spinning Troubleshooting
Problem
Probable Cause
Suggested Remedy
Temperature Setting
Temperature setting are crucial parameter for proper plastic processing ,hence one should check temperature controller, thermocouple and solid state relay(SSR)
- when you cold start the machine ,wait for 2hours.
Filament breakages due to degradation
- Moisture in the material
- Polymer dust/powder in the material
- High level of low molecular weight component in the material
- Pigments degrading at spinning temperature
- Higher melt residence time in the extruder/manifold
- Extrusion temperature too high
- Uneven temperature distribution in manifold and spin pack
- Use hopper dryer
- Use polymer dust free material, eliminate sharp corners in conveying system particularly at hopper valves which generate polymer dust due to abrasion of granules at these sharp corners
- Use narrow molecular weight distribution material, reduce extrusion temperature
- Use high temperature grade pigments
- Adjust melt residence time to optimum level
- Optimize extrusion temperature profile
- Check heating system, temperature controllers and thermocouples for its working
Filament breakage at spinneret
- Melt viscosity is too high or too low
- Addition of some types of pigments drastically reduce melt viscosity
- Uneven melt flow or formation of melt flow channel due to damaged filter pack of spinning head
- Uneven melt flow due to malfunctioning of metering pump
- Bits of decomposed material clog spinneret holes
- Adjust melt viscosity by optimizing extrusion temperature
- Use high pressure and temperature stability pigments, reduce extrusion temperature
- Replace damaged filter pack, reduce the pressure between extruder and filter pack
- Check metering pump drive system, replace worn out parts of metering pump
- Clean and replace spinneret, check for pigment degradation, reduce spin pack temperature
Filament breakage at quenching zone
- Melt drops down too high creating very high filament tension in spin-line zone
- Quench air velocity too high, filaments sticking to each other
- Filamentation at spin finish applicator, worn out thread guides
- Reduce take-up velocity
- Reduce quench air velocity, reduce quench air temp.
- Check thread guides for damage/serration, repair/replace spin finish applicator
Filament breakage at winding zone
- Jerks, vibrations and erratic drive of godet, the winder
- Worn out thread guides resulting into filamentation
- Increase viscosity with fresh ink
- Replace worn out thread guides
Non-uniformity of spun filaments
- Degradation of material
- Non-uniform dispersion of pigments, degradation of pigments
- Through-put variation
- Damaged or choked filter pack causing uneven melt flow
- Temperature variation between various spinning heads resulting into variation in melt viscosity
- Partial blocking of spinneret holes causing uneven melt flow
- Variation in quench air velocity
- Variation in take-up/winding speed
- Use polymer free of moisture and polymer dust, use hopper dryers and feeders, reduce extrusion temperature, use narrow molecular weight distribution polymers
- Use high temperature grade pigments, particle size of pigment should be less um size
- Check metering pump drive system, check and replace worn out metering pump parts
- Replace damaged filter pack with new pack
- Check temperature controller and thermocouples, maintain temperature variation between all spinning head within +/- 1°C
- Clean the spinnerets holes or replace spinning block with new pack
- Check and adjust air blower speed, clean air filters and nets
- Check AC inverters of godets and winders for their performance
Low elongation of spun filaments (POY)
- High MW polymer, wide molecular weight distribution polymer
- Heterogeneity of polymer melt; polymer mixing not proper
- Non-uniform dispersion of pigments
- Extrusion temperature too low making polymer melt extremely viscous
- Higher melt draw-down ratio and higher take-up velocity
- Higher quench air temperature
- Low quench air velocity
- Select polymer of low MFI and narrow molecular weight distribution
- Use static or dynamic melt mixers before spinning head, select pigments with particle size less than 5µm
- Use pigments with high temperature stability
- Increase extrusion and spinning head temperature
- Reduce take-up velocity, increase through-put rate
- Maintain quench air temperature between 7-9°C
- Maintain quench air velocity at 0.6 m/sec
