Transparent plastic is very common, but there are often problems with its molding. The editor has collected some articles and summarized them for reference. If there are any mistakes or additions, you can discuss and communicate in the comment area.
Silver streaks: Influenced by the anisotropy of internal stress during the filling and condensation process, the stress generated in the vertical direction causes the resin to flow upward, and the refractive index of the non-flow orientation is different from that of the non-flowing orientation. , may cause cracks in the product. In addition to paying attention to the injection molding process and mold (see the table, it is best to anneal the product. For example, PC materials can be heated to above 160 ° C for 3 to 5 minutes, and then naturally cooled.
Bubbles: Mainly because the water vapor and other gases in the resin cannot be discharged, (during the mold condensation process) or due to insufficient mold filling, the condensation surface condenses too quickly to form "vacuum bubbles". Its overcoming method is shown in the table.
Poor surface gloss: Mainly due to the large roughness of the mold, on the other hand, the condensation is too early, so that the resin cannot copy the state of the mold surface, all of which make the surface produce tiny unevenness, and make the product lose its luster. Its overcoming method is shown in the table.
Vibration lines: refers to the dense corrugations formed from the sprue as the center. The reason is that the front-end material has condensed in the cavity due to the excessive viscosity of the melt, and the later material breaks through the condensation surface, resulting in vibration lines on the surface. Its overcoming method is shown in the table.
Whitening and halo: Mainly caused by dust falling into the raw material in the air or the raw material has too much water content. Its overcoming method is shown in the table.
White smoke and black spots: mainly due to the decomposition or deterioration of the resin in the barrel due to local overheating of the plastic in the barrel. Its overcoming method is shown in the table. In order to clearly illustrate the measures taken to overcome these deficiencies, the table is listed for your reference.
Table 4: Defects and overcoming methods of transparent products:
Bubbles and voids
(1) The melt temperature is too high. The molding temperature should be lowered appropriately.
(2) The injection pressure is too low. should be raised appropriately.
(3) The pressurization time is too short. should be extended appropriately.
(4) The holding time is too short. should be extended appropriately.
(5) The mold temperature is too low. should be raised appropriately.
(6) Poor drying of raw materials. Pre-drying treatment should be carried out, and the drying temperature should be increased and the drying time should be extended.
(7) There are obstructions in the flow channel. Should be completely removed.
(8) The cooling time of the product in the mold is too long. It should be appropriately shortened, and it is best to slowly cool the demoulded product in a hot water bath.
Stomata and Trachoma
(1) Foreign matter impurities are mixed in the raw materials. A complete removal should be performed.
(2) The injection pressure is too low. should be raised appropriately.
(3) The back pressure of the screw is insufficient. should be increased appropriately.
(4) The screw speed is too high. should be reduced appropriately.
(5) Poor exhaust of the mold. Mold venting should be increased.
(6) The cooling time of the product in the mold is too short. should be extended appropriately.
Weld marks and material flow marks
(1) The melt temperature is too low. The molding temperature should be increased appropriately.
(2) The injection pressure is too low. should be raised appropriately.
(3) Insufficient supply. The amount of feed should be increased or a larger size injection machine should be used.
(4) The mold temperature is too low. should be raised appropriately.
(5) The holding time is too short. should be extended appropriately.
(6) The pressurization time is too short. should be extended appropriately.
(7) There are obstructions in the gate and runner. Should be completely removed.
(8) Poor exhaust of the mold. The mold vent hole should be increased or the mold clamping force should be reduced to vent at the mold clamping or welding point.
(9) The structure of the gating system is unreasonable. The form of the runner should be improved, and the gate should be re-selected to open.
cracks and streaks
(1) The melt temperature is too high. The molding temperature should be appropriately reduced and the temperature distribution of the barrel should be adjusted.
(2) The injection pressure is low. should be raised appropriately.
(3) Foreign matter impurities are mixed in the raw materials. Should be cleared.
(4) Poor drying of raw materials. Should increase the drying temperature and extend the drying time.
(5) The molding cycle is too long. should be appropriately shortened.
(6) Screw back pressure is too high or too low. should be adjusted appropriately.
(7) The gating system design is unreasonable. The gate, runner and sprue should be checked for blockage, and the layout and section size of the gate and runner should be adjusted reasonably.
swirl
(1) The melt temperature is too high or too low. should be adjusted appropriately.
(2) Too much feed. should be reduced appropriately.
(3) The mold temperature is too low. should be raised appropriately.
(4) The nozzle hole is blocked. Should be completely removed.
(5) Improper gate positioning. The opening should be re-selected.
(6) There are obstructions in the gate and runner. Should be completely removed.
Spots and Streaks
(1) Impurities are mixed in the raw materials. A complete removal should be performed.
(2) The barrel temperature is too high or too low. should be adjusted appropriately.
(3) The temperature distribution of each section of the barrel is unreasonable. should be adjusted appropriately.
(4) The injection pressure is too high or too low. should be adjusted appropriately.
(5) The structural size of the gating system is too small, the positioning is improper, and the flow resistance is too large. The gate and runner section should be appropriately enlarged to check whether there are obstructions in the runner.
(6) Poor exhaust of the mold. Mold exhaust should be increased to improve mold exhaust performance.
(7) There are hot spots and stagnant corners in the barrel and nozzle. The angle of stagnant material should be repaired to eliminate hot spots.
Cloud pattern and fog halo
(1) The melt temperature is too low. The molding temperature should be increased appropriately.
(2) The mold temperature is too low. should be raised appropriately.
(3) The injection pressure is too low. should be raised appropriately.
(4) Screw back pressure is too low. should be raised appropriately.
(5) Impurities are mixed in the raw materials. It should be completely removed or replaced with new materials.
(6) The temperature distribution of each section of the barrel is unreasonable. should be adjusted appropriately.
(7) The moisture or volatile matter content in the raw material is too high. Should be pre-dried.
Poor gloss and rough surface
(1) The melt temperature is too low. The molding temperature should be increased appropriately.
(2) The injection pressure is too low. should be raised appropriately.
(3) The mold temperature is low. should be raised appropriately.
(4) Insufficient supply. The amount of feed should be increased.
(5) Improper gate positioning. The opening should be re-selected.
(6) Insufficient cooling time. should be extended appropriately.
(7) There are obstructions in the flow channel. Should be completely removed.
(8) The surface finish of the mold cavity is too poor. Grinding and polishing should be done to improve the surface finish.
sunken
(1) The melt temperature is too high. The molding temperature should be lowered appropriately.
(2) The injection pressure is too low. should be raised appropriately.
(3) The mold temperature is too high. should be reduced appropriately.
(4) Insufficient supply. The amount of feed should be increased.
(5) The pressurization time is too short. should be extended appropriately.
(6) Insufficient cooling time. It should be extended appropriately, and the cooling time of the product in the mold can be shortened by placing the demolded product in a hot water bath for slow cooling.
(7) The holding time is too short. should be extended appropriately.
(8) Poor exhaust of the mold. Mold venting should be increased.
(9) There are obstructions in the flow channel. Should be completely removed.
Peeling and layering
(1) Insufficient supply. The amount of feed should be increased or a larger size injection machine should be used.
(2) The mold temperature is too low. should be raised appropriately.
(3) Foreign matter impurities are mixed in the raw materials. It should be completely removed or replaced with new materials.
