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Molding Defects: Stringiness
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The term "stringiness" is used to refer to a phenomenon
where string-line sections of plastic which are formed upon opening
of the die adhere to the inside of the die and are transferred to
the product during the next shot, resulting in string-line unevenness
on the surface of the molded component.
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Thin plastic string formed at the tip of a sprue
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Plastic string after transfer to the molded component
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| Cause : |
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This problem is principally caused by high nozzle temperatures. |
Countermeasures: |
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Lower the nozzle temperature; alternatively, make combined use of
pull-back and cylinder repetition. |
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Strings can be forced to break by increasing the
speed of die opening, however, care must be taken as this can
result in reduced die service lives for certain die designs (i.e.,
slides, etc.). |
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Use a string-prevent ring (commercially available).
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