POM Injection Process
Small Hole Diameter
1,Extend cooling time;
2, reduce the mold temperature, especially the die temperature on
the fixed needle side.
Big hole diameter
1,Shorten the cooling time;
2. Raise the mold temperature, especially on the side of fixing pin.
Smaller outer diameter
1. Increase the material shot and holding pressure;
2. Extend injection time and holding pressure time.
larger Out diameter
1, decrease shotting,holding pressure;
2. Shorten the time of shooting material and holding pressure time.
The thinner thickness
1. Increase shot and holding pressure;
2. Extend injection time and pressure holding time;
3. Increase the injection speed.
1. Reduce injection and holding pressure;
2. Shorten the time of shooting and holding pressure time;
3. Reduce the injection speed.
The thickness smaller but outer diameter larger
1.Reduce the injection speed and pressure in the first stage;
2.Increase the holding pressure of the first stage.
The thickness larger but the outer diameter smaller
1.Increase the injection speed and pressure in the first stage;
2.Reduce the first stage holding pressure.
I: Diameter is a
little larger or smaller
The shrinkage of POM material has a great relationship with cooling time. Short cooling time is
slow to set, small size. But, product finalize the design fast, slow have a limit, if reach a limit to
still continue to adjust time, won't work. We can use this method to quickly test the results:
assume the original cooling time is 10 seconds, the aperture is relatively small, and adjust to
20 seconds for beer test. If the aperture does not change, it means that it cannot be enlarged
any more. At this time, other methods (such as mold modification) should be considered
to solve this problem.
II: The thickness and outer diameter is smaller or large at the same time
These cases are relatively easy to solve, and here won't go into details.
III: The thickness and outer diameter are smaller or larger in opposite directions
These two situations are arguably harder to deal with. When the
thickness is relatively small and the outer diameter is relatively large,
reducing the speed and pressure of the first phase in injection can help reducing the outer diameter. Increasing the first stage pressure can increase the thickness to some extent. When the thickness is too large and the
outside diameter is too small, increase the speed and pressure of the first phase which is helpful
to increase the outside diameter. Small thickness
can be increased to a certain number by reducing the first stage holding pressure.
However, for the thickness adjustment, there are certain limitations,
the process method can not solve the problem, should be in priority to adjust the outer diameter, repair mold. Increase or remove material to adjust the thickness. The reason is that it is very difficult to repair the outer diameter of the
gear, and it is almost impossible to repair, so, unless it is a special case, otherwise generally do not consider the repair of the outer diameter of the mold, and mold
thickness size is relatively easy to repair.
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