Overflow edge
For the overflow edge
processing should be mainly focused on improving aspects of mold. And in the
molding conditions, we can begin to reduce liquidity. Specifically, the
following methods may be used:
1) reduce the injection pressure.
2) reducing the temperature of the resin.
4) The use of high viscosity grades of
material.
5) lowering the mold temperature.
6) mold surface grinding overflow edge
occurred.
7) The harder the steel mold.
8) increase the clamping force.
9) Adjust the exact molds and other parts
of the joint surface.
10) increase in die support columns, in
order to increase the rigidity.
11) is determined depending on the material
of the exhaust ducts of different sizes.
Burn
According to Burns by different
reasons machinery, molds or molding conditions caused by the solution adopted
is different.
1) mechanical reasons, e.g., due to an
abnormal condition caused by overheating of the barrel, the resin pyrolysis,
injected into the product after burn
, Or simply because the material in the
nozzle and the screw thread, check valve and other parts of the stagnation
caused by the resin, after decomposition of color into the products, with dark
brown burn scar in the article. At this time, we should clean up the nozzle,
screw and barrel.
2) Cause molds, primarily because due to
bad exhaust. Such burns generally occurs in a fixed place, easy to distinguish
the first case. Then add exhaust ducts should pay attention to take measures
such as anti-blow-down bar.
3) in the molding conditions, when the back
pressure above 300MPa, the barrel portion would overheat, causing burns. Screw
speed
When too high, it will produce heat,
generally in the 40 ~ 90r / min range as well. Did not set in exhaust ducts or
exhaust ducts is small, the injection speed too high will cause superheated gas
burns.
Warping, deformation
Injection products, warp,
deformation is very difficult problem. Mainly from mold design to address, and
to adjust the effect molding conditions is very limited. Warp, causes and
solutions of this variation may refer to the following items:
1) residual stresses caused by the molding
conditions cause deformation, by reducing injection pressure, improve mold and
mold temperature uniformity and increase the resin temperature or the use of
annealing method to eliminate stress.
2) the release of stress and deformation
caused by bad, it can be solved by increasing the number or area of the push rod, a release gradient methods.
3) As the cooling method is inappropriate,
uneven cooling or insufficient cooling time, cooling method and the extension
of the adjustable cooling time. For example, you can set up close to the
deformation of the cooling circuit in place as possible.
4) For the deformation caused by mold
shrinkage, it is necessary to revise the design of the mold. One of the most
important to pay attention to the wall thickness is consistent. Sometimes, in
the last resort, it had by measuring the deformation of the article, in the
opposite direction trimming die, to be corrected. Larger shrinkage resin, a
crystalline resin is generally ~ (e.g. polyoxymethylene, nylon, polypropylene,
polyethylene and PET resin) than the non-crystalline resin (such as PMMA resin,
polyvinyl chloride, polystyrene, ABS resin and AS resin) of deformation.
Further, since the glass fiber-reinforced resin having fibers
Bubble
According causes bubbles, solving
strategies in the following areas:
1) is larger in wall thickness, the outer
surface of the cooling rate faster than the central portion, and therefore, as
cooling proceeds, the resin shrinkage side edge of the central portion of the
surface of the expansion, the central unit generates less filling. This
condition is known vacuum bubbles. Solutions include:
a) according to the thickness, to determine
a reasonable gates, runner dimensions. General gate height should be 50% to 60%
of the wall thickness.
b) to the gate sealing up, leave some
supplementary material injection.
C) injection time should be slightly longer
than the gate seal.
d) reducing the injection speed, injection
pressure increase,
e) the high melt viscosity grade material.
2) due to the generation of volatile gas
bubble caused, the solution are:
a) full pre-drying.
b) reducing the temperature of the resin,
to avoid decomposition gas.
3) bubble caused by poor liquidity, can be
resolved by increasing the temperature of the mold resin and improve injection
speed.
Albino
Whitening phenomenon occurs in the launch
of the most important parts of ABS resin article. Stripping ineffective is the
main reason. Injection pressure can be reduced, increased stripping slope,
increase the number of push rod or area, reducing the surface roughness of the
mold and other ways to improve, of course, spray release agent is also a
method, but should be careful not to follow the process , such as stamping,
painting and other adverse effects
In the process of injection molding, there are still many problems. For example www.injectionmoldchina.com
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