Injection product problems and solutions (b)

Posted August 6, 2015 by cnmoulding

Custom Plastic Injection Molding Maker,Factory,Manufacturer,Supplier,Exporter of plastic products and parts in China

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.

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


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.


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
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Last Updated August 6, 2015