1.Broken strips caused the original deficiency
■Increase the mesh or number of filters;
■ Appropriately reduce the speed of the main engine or increase the speed of feeding;
■ Appropriately lower the extrusion processing temperature (machine head or other areas).
2.External impurities
■ Check whether the dead corner of the equipment in the mixing and unloading process is cleaned and whether impurities are mixed in;
■ Add as little crushed material as possible or manually screen the crushed material to remove impurities;
■ Increase the mesh and the number of filters;
■ Try to cover the holes (solid cover or mesh cover) where debris may fall.
3.Internal impurities
■ The pressure of the machine head is too high (including clogging of the die, too many filters, the temperature of the machine head is too low, etc.), which causes an increase in the backflow and causes the carbonization to increase. ;
■ The extruder is locally overheated, causing the carbonization to increase, and the carbonized material is taken out to the material strip, which causes a broken strip under the action of traction;
■ The shearing of the screw is too strong, which causes the localized carbonization of the material, and the carbonized material is taken out to the material strip, which causes a broken strip under the action of traction;
■ The machine has a long service life, the screw and barrel are worn, the gap is increased, the backflow is increased, and the carbonized material adhered to the barrel wall increases. With the extension of the extrusion time, the carbonized material is gradually taken out to the strip, which causes breakage under the action of traction. article;
■ Vacuum or natural exhaust ports (here including gaskets and dead corners) are not cleaned for a long time, and the existing carbonized materials are brought to the material strip, which causes the strip to break under the action of traction;
■ The die of the machine head (here including the discharge port and the internal dead corner of the machine head) has not been cleaned up, and the carbon or the impurities contained in the die are brought to the material bar, which causes a broken bar under the action of traction;
■ The time interval for replacing the filter screen is too long, the filter screen is blocked, and the material cannot come out, causing broken bars.
4.Changes in raw material properties
■ The fluidity of the blended components is too different at the same temperature. Because the fluidity does not match or is not completely compatible (including physical entanglement and chemical reaction), in theory this is called "phase separation" "Generally, it does not occur in blending and extrusion, and more often occurs in the injection molding process. However, if the MFR difference is too large, broken bars may occur under the premise that the screw shear is relatively weak;
■ Viscosity changes of blended components: For the same material, if the MFR decreases, the hardness, rigidity and notch become larger, it is possible that the molecular weight of the batch is larger than before, causing the viscosity to become larger and the original processing Under the action of temperature and process, it causes poor plasticization. At this time, it can be solved by increasing the extrusion temperature or reducing the screw speed of the host machine.
5.Poor plasticization of materials
■ The extrusion temperature is low or the screw shear is too weak, the material is not fully plasticized, and there are pimples, which cause broken bars under the action of traction;
■ Low melting point additives (including EBS or PETS, etc.) in the formulation system cause poor plasticization and broken bars under the premise that the screw shear is weak or the gap between the screw and barrel is increased and the shear is weak.
6.The strip is trapped in steam or exhaust is not smooth
■ The processing temperature is too high or the local shear of the screw is too strong or the local screw is overheated, which causes the decomposition of some flame retardants and other additives, releasing gas, the gas is not drawn out in time by the vacuum, and the gas is trapped in the material strip and acts on traction Down, causing broken bars;
■ The material is seriously damp, the processed water vapor has not been exhausted by natural exhaust and vacuum in time, the vapor is trapped in the strip, and the strip is broken under the action of traction;
■ Natural exhaust or vacuum exhaust is not smooth (including blockage, air leakage, too high gasket, etc.), causing gas (or steam) to be trapped in the material strip, resulting in broken strips under the action of traction.
7.Material rigidity, water cooling or excessive water, traction mismatch
■The rigidity of the material is too high, the water temperature is too low, too much water is passed, the discharge of the machine head is very soft, and the water immediately becomes very hard. Under the effect of the mismatch of the traction force, it causes a broken strip-this phenomenon often occurs in PBT or PET plus fiber, PC plus fiber, AS plus fiber, ABS plus fiber and other materials with very fast crystallization speed or very high rigidity, especially the small machine is more serious for experiment, at this time increase the water temperature, reduce the amount of excess water, let the cut The pellet of the pellet machine can maintain a certain degree of softness, which can be solved.
