How to improve the problem of plastic defects
- Categories:News
- Time of issue:2021-05-21 11:47
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(Summary description)The plastic injection molding process is appropriately complicated and involves many elements. When a problem is found, the stability of the process should be confirmed first, and that the defect is not caused by an excessive process. There is no fixed process for sweeping injection molding problems, but at least for some defects caused by operating characteristics, useful improvement methods can be advocated.
How to improve the problem of plastic defects
(Summary description)The plastic injection molding process is appropriately complicated and involves many elements. When a problem is found, the stability of the process should be confirmed first, and that the defect is not caused by an excessive process. There is no fixed process for sweeping injection molding problems, but at least for some defects caused by operating characteristics, useful improvement methods can be advocated.
- Categories:News
- Author:
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- Time of issue:2021-05-21 11:47
- Views:
The plastic injection molding process is appropriately complicated and involves many elements. When a problem is found, the stability of the process should be confirmed first, and that the defect is not caused by an excessive process. There is no fixed process for sweeping injection molding problems, but at least for some defects caused by operating characteristics, useful improvement methods can be advocated.
(1) Adjust the data preparation process: plastic storage cylinders and hoppers should be covered to avoid material contamination. Set appropriate drying conditions, excessive drying time or drying temperature, the volatiles in the plastic will be driven away, or the embrittlement or cracking of the plastic may be formed. Plastic suppliers can provide the best drying conditions for plastics. If the process conditions of low-strength materials are not appropriate, embrittlement may be formed, and high-strength and excellent thermal stability plastics can be considered. Embrittlement may also be caused by the increase in the amount of plastic recovered and reground, and the decrease in the test increases the amount of plastic recovered and reground. When replacing plastics, the injection system should be thoroughly cleaned up, and the hopper should be cleaned up thoroughly to avoid mixing the plastic with different colors or unidentified plastics in the hopper.
(2) Change the mold plan: black spots are found at the end of the movement path, which may be caused by a bad exhaust system. The compressed air may be burned to form surface defects, and the exhaust system should be improved. Set up an appropriate exhaust system in the mold to remove the wind. The end of the movement path and the exhaust system of the blind hole are particularly important. It is advocated that the vent hole size of crystalline plastic is 0.025 mm (0.001 inch), and the vent hole of amorphous plastic is 0.038 mm (0.0015 inch). Excessive shear heat may occur in the too narrow vertical sprue, runner, gate, and even the thickness of the plastic part, which will make the overheated material worse and cause the plastic to crack. Capable of testing enlarged down sprues, runners and/or gates. For mold materials with too low thermal conductivity, the cooling rate can be reduced to improve the appearance of the plastic part.
(3) Fixing the mold regularly: The mold should be arranged before injection molding. Perhaps it is the elements of the injection machine that form resin accumulation and cracking. The smoothness of the resin movement should be checked and the accumulated waste should be sorted out regularly. The black streaks may be formed by the lubricating grease of the slider and the top nail, and the thimble and the slider should be cleaned regularly. The surface of the runner system should be cleaned or polished regularly to avoid accumulation of dirt in these areas. The black lines may be contaminated by the wall of the barrel or the outer surface of the screw, especially when the two plastics are injected and molded, the former plastic may still remain in the barrel and must be thoroughly cleaned up.
(4) Standards for selecting an injection molding machine suitable for the mold: Select a screw that is more suitable for the plastic to be used, so that the plastic can achieve a better mixed melt state. The plastic suppliers can be required to provide proper screw planning information to avoid plastic overheating and cracking. The injection volume should generally be maintained at 20~80% of the machine standard. For temperature-sensitive data, a narrower temperature scale is used. Check the scratches or tooth marks on the surface of the barrel/screw to avoid accumulation of plastic, which may cause overheating or incineration of the plastic. Check whether the solid heating plate or the controller fails to avoid the formation of plastic overheating. The mold flow analysis software for plastic injection molding can help the mold select the appropriate standard injection machine, so that it can avoid the plastic staying in the barrel for too long.
(5) Adjust the forming conditions: If the temperature of the barrel and nozzle is too high, the plastic in the barrel may overheat and cause cracking, which can lower the barrel temperature and nozzle temperature. In addition, the back pressure, screw speed, injection speed or injection pressure can be reduced to avoid the formation of cracking due to too high shear heat. In addition, check the heating fins of the barrel and nozzle, and calibrate the thermocouple to confirm the temperature of the barrel and nozzle.
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