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Silver Streaks

Author : Date : 4/21/2013 7:52:21 AM

Silver Streaks

Silver streaks are distinct streaks, usually radiating from the gate and are often caused by excess moisture, air introduced or degradation during plasticisation of

the melt in the barrel of the machine.

Many plastics absorb moisture from the atmosphere; how much they absorb depends on the type of resin. Moisture in the granules, even if it is only surface

condensation, can cause problems in parts including, poor surface finish, processing issues, increased flash or loss of mechanical properties such as impact and

tensile strength in some materials.

Solution:

         1. Increase back pressure.

         2. Decrease melt temperature.

         3. Check the mould cooling circuit for leaks onto the mould face.

         4. Check the packaging of the plastic granules damage.

         5. Check the moisture content of the granules,

         6. Ensure pre-drying at recommended temperature and time.

         7. Reduce the quantity of granules held in the feed hopper.

         8. Check raw material storage conditions.

         Most engineering materials require between 2 and 4 hours drying to reach typical acceptable moisture content for moulding: 0.02%. Hot air dryers are not

always effective especially in humid environment; therefore dehumidified-air drier systems are the preferred method.

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