0102030405
Die Casting Defect Series - Flash
2025-09-28
Flash can also be called: flying material, seam, burr, flying wing, escaping material, and bulging mold.
Defect characteristics:
Flash is the excess metal that protrudes from the part along the parting surface, movable mating surface or cavity joint of the casting. The flash inside the internal hole of the casting is usually called the flash.
Generally, the thickness of the flash is about 0.1~0.3mm. If the flash is too thick, it will affect the size of the die casting. Although a small amount of flash can increase the exhaust performance, it will cause more and more flashes and even damage the mold. Too many and too thick flashes will cause material to fly (leave material) and affect the internal and external quality of the casting.
Cause:
(1) The clamping force of the Injection Molding machine is not adjusted large enough, or the die casting pressure is too large, exceeding the clamping force of the die casting machine;
(2) The injection speed is too high, resulting in a high pressure shock peak;
(3) The slider of the mold is damaged or the locking parts are too tight or too loose;
(4) The insert and the slider are worn, or the clearance is too large, the slider is not inserted into place, and the alloy liquid penetrates into the clearance.
(5) The dynamic and fixed molds are not tightly closed and the gap is too large. The dynamic and static mold surfaces of the Die Casting Mold are not parallel. The mold strength is insufficient, causing deformation. The mold support plate has a large span, and the injection force causes the sleeve plate to deform.
(6) Before closing the mold, the mold parting surface is not clean, and there is residual aluminum or other adhesions that have not been cleaned.
(7) The parallelism of the die-casting motor and fixed die mounting plates is too large. The four Green columns are unevenly stressed, the crankshaft and connecting rod mechanism are worn, and the die mounting plate is uneven.
Countermeasures:
(1) If the flash of the parting surface is in a certain direction, not in every direction, remove the adhesion of the parting surface and ensure that the parting surface is clean before closing the mold. Make the mold tightly closed, reinstall the mold if necessary, and clean the dirt on the mold and the die-casting machine mold mounting plate.
(2) If the flash of each casting is the same, the cause is in the mold or equipment.
① Check the deformation and damage of the mold, check the mold sealing condition, if the seal is not tight, repair the mold, weld and repair the sunken parts of the mold surface to prevent flying material channels;
②. Check and trim the flatness and surface roughness of the parting surface and the surface of the local insert. The concave and convex parts should be well fitted. If there is still flash when high-speed injection without using boost, it means that the high speed is too high. If there is still flash when half the high speed injection without using boost, it means that the mold fit accuracy is not good.
(3) Check the strength of the die casting mold. The mold must be rigid and not deform. The locking components (wedge blocks, oil cylinders, etc.) should be tightened with locking blocks after the slider. Confirm the tightness of the mold guide pin and guide sleeve, and whether the step end surface is higher than the mold plate surface.
(4) Check the contact surface between the movable core and the mold, etc., reduce the mold clearance of the slider and other molds, and repair the wear. When the sliding joint is clean, use a feeler gauge to check the clearance. When the side core slider is clean, check the wedge of the slider, color and grind it, repair or replace the wedge.
(5) The height of the module above the parting surface of the sleeve is 0~0.05mm. If it is too high, the sleeve will not be able to seal the alloy liquid. The large cavity module should be enlarged to prevent the appearance of flash at the exhaust groove. After the mold is closed, if the depth of the outer side of the exhaust groove is greater than 0.05mm, the aluminum alloy liquid will flow out of the exhaust groove, resulting in flying materials.
(6) Correctly calculate the mold strength and reasonably design the thickness of the sleeve. Strengthen the mold support and add support plates and support columns to the movable mold.
(7) Reduce the depth of the exhaust groove, increase the length of the exhaust groove, change the direction of the exhaust groove to prevent the alloy liquid from flowing out of the mold, and increase the rigidity of the sleeve plate.
(8) If the shape of the flash changes significantly, especially when the heat of the mold rises, the thermal shock force exceeds the clamping force, or the gap between the parting surfaces increases due to thermal expansion of the mold, causing the molten metal to overflow the cavity. The temperature difference between the high and low temperatures of the mold should be reduced, the clamping force should be increased appropriately, or the injection force and boost pressure should be lowered to prevent the expansion force during die casting from being greater than the clamping force of the die casting machine.
(9) Before starting die casting process, preheat the mold and cool it down with cooling water during the die casting process. A good temperature field ensures a good fit and seal between the molds during the production process. Lowering the mold temperature at the exhaust groove reduces the flow of alloy liquid in the exhaust groove.
(10) Reduce the high-speed injection speed and the fluidity of the alloy liquid to reduce the expansion force and reduce the impact of the alloy liquid drilling into the parting surface;
(11) Reduce the alloy liquid pouring temperature and reduce the alloy liquid fluidity;
(12) Reduce the boost rising speed, extend the boost rising time, and reduce the flash caused by the boost pressure;
(13) Slow down in advance, reduce the speed after deceleration, and reduce the impact force at the end of filling.