Some plastics molding after releasing soon in the back of the piece of metal inserts or swelling and bubbling in the thickest part of the special, which is released under the effect of gas expansion cooling due to the incomplete hardening of plastic, including pressure caused.
(1) reduce the mold temperature, mold extend time.
(2) reduce material drying temperature and processing temperature; lower filling rate; reduce the molding cycle; reduce flow resistance.
(3) improve the packing pressure and time.
(4) to improve products or thick wall thickness variation in the situation.
(1) plastic high temperature, long products cooldown. Barrel temperature should be lowered to reduce the screw speed or back pressure, adjusting temperature of each barrel is good.
(2) mold temperature is high, the impact of stereotypes, and cause card, clip articles and downtime. We must focus on strengthening the cooling channels. (3) molding time unstable. It should be automatic or semi-automatic operation.
(4) a barrel for the lack of heat. Plasticizing capacity should be used to strengthen the preheating of the machine or materials.
(5) to improve the conditions of machine production, such as oil, fuel, clamping force and so on.
(6) nozzle drool. Should control the barrel and nozzle temperature or replaced with self-locking nozzle.
(7) the part thickness is too thick. Mold should be improved to reduce the wall thickness.
Backpressure: When feeding, the screw in the opposite direction retrograde added pressure on the molten plastic;
Back pressure effect:
1. To improve the plastics melt kneading effect;
2. Increase the temperature of the molten plastic;
3. Increase the density of the molten plastic;
4. promote uniform plastic colors;
5. The exhaust gas within the molten plastic;
Low voltage protection: refers to a protective device for mold resistance when clamping generated, which can make the mold when pressed by the smallest foreign object damage, reduces die losses. The working principle is the distance from clamping in the mold clamping pressure is set low to a certain time, when the mold clamping encountered foreign body in this process. Plastic or due to insufficient lubrication within a set time is less than the high-pressure lock When the switching point, the machine will generate an alarm, and the mold is opened;
Hot runner system leak-Analysis:
1. The support pad is too low. Under the influence of the injection pressure, the flow channel plate and hot mouth creating a gap resulting from drooling.
2. The support pad is too high. Support pad into the top mold base plate, this prevents leakage of plastic flow channel between the nozzle plate and the heat, but in the role of injection pressure and clamping pressure manifold is pushed to one side, resulting in leakage of plastic.
3. The center pad is too high. Manifold empty frame on the center pad, plate and hot runner nozzle from creating a gap caused by drooling.
4. The center pad is too low. Injection pressure in the injection molding machine, the center pad collapsed manifold bent, causing leakage of plastic.
5. hot mouth highly uneven. Lowest thermal drooling mouth easily.
6. spacing the screws and manifold or hot mouth too much. Manifold and heat seal the mouth is not enough, resulting in leakage of plastic.
7. The locating pin high. Manifold empty frame on the positioning pin, plate and hot runner nozzle from creating a gap caused by drooling.
8. hot mouth too long. Hot mouth no room for expansion and generate pressure on the heat loss of the role of the mouth of the ring, resulting in leakage of plastic. 9. The seal is too high or too low. Ring approximately 0.3 mm pre-compression, high cause manifold easily deformed, easy to drain the hot glue on the plane of the mouth. There is no initial clamping force is too low, after heating the hot runner system leak glue.
10. The hot mouth locate the installation location of the error. Shen head hot mouth or on the front frame in a mold insert on the front mold core die rather than leave the front, hot mouth by the time the injection pressure or thermal expansion mouth, clamping pressure error will force the front-Hui , resulting in leakage of plastic.