Injection molding products refer to plastics that are heated, plasticized and melted by an injection molding machine, and then injected into the cavity of a molding mold for molding. After cooling down, the melt is solidified and demolded, and the injection molding machine is injection molded.
Flash may occur during the injection molding process (also called flash, burr, burr, etc.). Flash occurs mostly at the opening and closing positions of the mold, such as the parting surface of the movable mold and the static mold, and the sliding of the slider. To a large extent, the flashing at the matching position, the gap of the insert, the hole of the ejector pin, etc. is caused by the failure of the mold or the clamping force of the machine. Some specific reasons are summarized as follows:
1.If the maximum clamping force of the machine is not enough, a machine with sufficient clamping force should be selected. The hinges of the clamping machine are worn or the sealing elements of the clamping cylinder are worn and the oil drips or backflows, which causes the clamping force to drop. The heating system is out of control and the actual temperature is too high. Check whether there is any problem with the thermocouple, heating coil, etc.
2. Unbalanced mold cavity distribution or insufficient parallelism can cause unbalanced forces and cause local flash and local dissatisfaction. The runner should be placed in the center of mass symmetry as far as possible without affecting the integrity of the part. Unbalanced forces on movable components and sliding cores in the mold will cause flash. When the mold is poorly exhausted, the compressed air will cause the mold parting surface to expand and flash, so a good exhaust system should be set up, or an exhaust ditch should be dug on the parting surface.
3. If the fluidity of the plastic is too large, or add too much lubricant, the pressure, speed, temperature, etc. should be appropriately reduced, and the amount of lubricant used should be reduced. If necessary, plastics with low fluidity should be used.
4. Processing and adjustment aspects:
(1) If the temperature, pressure, and speed are set too high, segmented injection should be used. Injection time, pressure holding time, and too much feed will cause flash.
(2) When adjusting, the hinge of the mold clamping machine is not straightened, or the mold adjusting nut often moves when opening or clamping the mold, resulting in insufficient clamping force and flashing.
(3) The parallelism between the adjusting head and the diode is not enough or the adjusted system pressure is too high.
5. Reasons for recurring flash and part dissatisfaction:
(1) Uneven particle size of plastic raw materials will cause the feeding amount to be uncertain.
(2) Excessive wear of the screw head, rubber ring and rubber gasket may cause the melt to slip between the screw and the barrel and return to cause flashing or dissatisfaction.
(3) The cooling system of the inlet fails, which makes the feed adjustment.
(4) The set injection volume of the barrel is insufficient, that is, if the cushion is too small, it will cause flashing or part dissatisfaction when the material is injected more and more times.
Post time: Nov-10-2021