Extrusion molding processThermoplas

Extrusion molding processThermoplastic plastic extrusion molding process is divided into four stages lesson.Plasticizing stageThrough dry processing plastic raw materials by extruder hopper to join a nitrogen-treated barrel nitrogen-treated barrel, after the heating and screw rotation, compaction and the mixing action below, by solid powder or aggregates into uniform melt with some liquidity for the process plastication.Extrusion stageEven with the plastic melt plastication screw rotation was sent to a nitrogen-treated barrel in front, screw rotation extrusion action by extrusion die, on a certain shape mouth mode and get section and mouth model shape continuous profiles consistent.Finalizes the design phaseThermoplastic plastics in leave immediately after mouth mode, extruded plastic continuous profiles for cooling and finalize the design, or plastic in self-respect under the action of will deformation, appear sag or distortion phenomenon.In most cases, qualitative and cooling is finish at the same time, only in extrusion various bar stock and pipe, just have a separate qualitative process, and the extrusion film, finalize the design process, no single etc, if only by cooling can be. Extrusion plank and sheet, sometimes by a pair of roller planish, while rise to finalize the design and cooling effect. Cooling generally USES air cooling or water cooling, cooling speed on the plastic parts surface roughness, size shape accuracy etc performance has very big effect. Hard plastics (such as polystyrene, low density polyethylene and rigid PVC etc.) can't cooling too fast, otherwise easy to cause the residual stress, and affect the appearance of plastic parts quality; Soft or crystallization type requires plastic parts in time, lest plastics deformation cooling.Traction plastic parts. Coiling and cuttingPlastics extruding the mouth mode since, usually because of pressure from mold and happen suddenly lifted after inflation phenomenon, and cooling shrinks will happen again, thus make the size and shape of the plastic parts changes. In addition, because plastics was continuous extrusion, self-respect is more and more big, if not guidance, can cause plastics stagnation, make plastic thing cannot be smooth extrusion. Therefore, in the cooling at the same time, we should continuously will plastics derivation, this is traction.Traction process one by extruder auxiliary device to complete. Traction Traction with extrusion speed speed will adapt to, general traction speed slightly higher than the extrusion speed, so as to eliminate the plastics dimension change, at the same time for plastics proper stretching can improve the molding quality. Different plastics traction at different speeds. Usually film and monofilament traction speed can be quicker, its reason is drawing speed, the plastic parts decreased diameter and thickness, longitudinal strength increases, elongation fracture resistance reduction. For extrusion hard plastic parts, traction speed cannot big, usually takes will drag speed regulation within a certain range, and to be very evenly, otherwise it will affect its size uniformity and mechanical properties.Through the plastics class traction in cutting device according to use requirement on cutting (such as rods, tubes, plate, sheet etc), or in coiling device made around a roll (such as film, monofilament, cables, etc). In addition, some plastic parts such as films etc, sometimes need to undertake post-processing, in order to improve dimensional stability.