First, black point problem analysis and solution analysis: (1) The sealing and dustproof work of the injection processing raw materials is not completed, which causes dust to be mixed into the raw materials, resulting in contamination of the injection molding processing materials. (2) During the feeding process, the bags or other utensils loaded with the injection molding raw materials are not cleaned up in time, so that the raw materials are doped with impurities. (3) The injection molding mold was not cleaned up in time, so that the mold and the raw material were rubbed for a long time, which caused black spots in the injection molded workpiece. (4) In the process of injection molding, the color matching bag is mistakenly incorporated. (5) During the refueling process, it was not cleaned up in time, which resulted in the mixing of dark and light colored injection molding parts, resulting in black lines. (6) The cleaning of each injection molding component is not thorough enough, resulting in the inclusion of impurities in the injection molding process. method: (1) Reduce the material temperature and reduce the residual amount (2) Cleaning the drying hopper (3) Check raw materials to prevent foreign matter from being mixed (4) Replace the diffusing agent or increase the amount of diffusing agent (5) Control the nozzle material (6) Cleaning the barrel Second, the analysis of problems in the process 1. Insufficient pressure on the nose method: (1) Increase the mesh number or the number of sheets (2) Adjust the main engine speed or increase the feed speed appropriately; (3) Properly reduce the extrusion processing temperature (head or other zones). 2, external impurities Analysis: Check whether the dead angle of equipment in all aspects of mixing and discharging is cleaned up and impurities are mixed in; method: (1) Minimize the addition of broken materials or artificially screen the broken materials to remove impurities; (2) increase the mesh number and the number of sheets; (3) Try to cover the holes that may fall into the debris. 3. Internal impurities (1) The pressure of the machine head is too high (including the blockage of the die, too much filter screen, the temperature of the machine head is too low, etc.), causing the increase of the reflux to cause the carbonization to increase, and the carbonized material is taken out to the material strip, which causes the traction force to cause Broken strip (2) The extruder is partially overheated, causing the carbonization to increase, and the char is taken out to the strip, causing a broken strip under the action of traction. (3) The screw shearing is too strong, causing the local carbonization of the material to increase, and the char is taken out to the strip, causing a broken strip under the traction force. (4) The machine has a long service life, the screw and the barrel are worn, the gap is increased, the backflow is increased, and the carbon carbide adhering to the barrel wall is increased. As the extrusion time is extended, the char is gradually taken out to the strip, under the traction force, Causing fracture (5) Vacuum or natural exhaust ports (including gaskets and dead ends) are not cleaned for a long time, and the existing char is brought to the strip, causing broken strips under the action of traction. (6) The die of the machine head (including the discharge port and the internal dead angle of the machine head) is not cleaned, and the die contains carbonized material or impurities and is brought to the strip. Under the traction force, the broken strip is caused. (7) The time interval for replacing the filter screen is too long, the filter screen is blocked, and the material does not come out, causing a broken strip. 4. Poor plasticization of materials: (1) The extrusion temperature is too low or the screw shear is too weak, the material is not fully plasticized, and the material is smashed, causing a broken strip under the action of traction. (2) Low melting point auxiliaries (including EBS or PETS, etc.) in the formulation system, weak in screw shearing (usually reflected in line 2) or increased clearance between screw and barrel (often reflected in line 1) and shearing Under the premise of weaker, resulting in poor plasticization, resulting in broken strips Third, granulation hollow problem analysis and solution Poor exhaust Exhaust (or steam) is not smooth: due to natural exhaust or vacuum exhaust (may be too heavy in the material itself, it may also be decomposed by additives such as flame retardants, there may be vacuum blockage or vacuum is too small or leaking or The vacuum gasket is too high, etc., causing the presence of gas (vapor) in the particles, forming a hollow Poor plasticization The processing temperature is low, the material is not completely plasticized, the light (small hole) causes the particles to be hollow, and the heavy one (large hole) causes the broken piece Low melting point auxiliaries (including EBS or PETS) are too much, and the shearing of the screw is weak (for example, the ordinary aBS is produced on the 2nd line, the EBS cannot be too much, and too many "pores" appear), resulting in poor plasticization of the material. Hollow There are too many low melting point auxiliaries (including EBS or PETS), and the gap between the screw and the barrel is increased (for example, ordinary wire aBS is produced on line 1, sometimes EBS is not too much, too many "pores" appear) or screw shear Under the premise of weakening, the plasticization is poor and the hollow is formed. The water temperature is too low: the cooling water temperature is too low, the material shrinks with water, causing shrinkage holes, such as PP products - such phenomena are mainly for crystalline plastics; in general, crystalline plastics (such as PP, Pa, PBT, etc.) Low water temperature should be used, and non-crystalline plastics (such as aBS, PC/aBS, HIPS, etc.) should adopt high water temperature. Fourth, the analysis of bubble problems Air bubbles often occur at the last seam of the plastic article or in the thicker portion of the article. The product is first surface cooled in the model, and when the outer surface is cooled, the central portion is still hot. The central part is shrunk when it cools, and the plastic surface is already cooled, so it can only be formed by the internal contraction itself. There are many thick parts that have no bubbles at the time of ejection, but after several tens of seconds, bubbles appear in the center. There are several kinds of bubbles, the phenomenon is different, and the reasons are different. The description is as follows: Thicker products, the surface is fat and bulging, there are bubbles at the sawing section, the reasons may be: (1) The injection speed is too fast, enveloping the air, can not be ruled out, forming bubbles (2) If the feeding amount is too much or too little, and the injection pressure is too high, this phenomenon will also occur. If the feeding amount is properly adjusted, the phenomenon will be improved. (3) The cooling time is too short (especially thick-walled products), and the solution can be cooled by using cold water and cold die outside the machine. (4) There is a phenomenon of decomposition of black lines in the product, which is formed due to excessive temperature. If the situation is not serious, the temperature can be lowered appropriately. If the entire barrel is disassembled, it must be removed by car. (5) The phenomenon that the mold inlet is too small and the exhaust gas is bad, this phenomenon will also occur. Five, hopper bridge analysis Too much filler, moisture absorption, agglomeration, resulting in increased friction between the mixture and the hopper wall, adding liquid lubricants such as “white oil†to reduce the friction between the mixture and the hopper wall and the mixture, and the mixture can be decomposed. Block (including high temperature agglomeration and liquid additives added too much to agglomerate), reduce drying temperature or high mixing time, reduce the amount of liquid additives added, add powdery resin or auxiliary agent that absorbs "oily" substances (eg, high rubber powder, aS powder, PP powder, etc.) can be solved. Heavily Hot-Dip Galvanized Wire
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Common problems in plastic processing and solutions