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.
Solution:
(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.
Production slow
(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.
In the process of injection molding, there are still many problems. For example
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