Plastic Injection Defects: Splay or "Silver Streaking"

• Check for Contamination:

  It is important to make sure that the materials you are using are not contaminated. Also, review the regrind percentage to assure that you aren't beyond normal levels. If regrind is in the equation, could it have absorbed moisture?

• Increase/ Decrease Melt Temperature:

  Two separate conditions can arrise that could cause splay conditions ..The first is if your material is overheated... material that is overheated by shear or regulation setpoints can result in heat-related splay defects. But remember... low temperatures can also lead to poor flowfronts which can show signs of splay due to poor flow conditions due to sheer heat. Check the MSDS for proper melt and mold temperatures.

• Increase/ Decrease Nozzle Temperature:

  Low nozzle temperature can lead to poor viscosity and shear heat at the beginning of fill.It's important to remember that the primary causes of splay are moist materials or temperature profiles. Drastic changes in temperature during material transfer can lead to splay defects. If the nozzle temperature is too high this too can lead to an overheat condition.

• Dry resin pellets before use... Check Moisture Content:

  Moisture content is key to any plastic injection process. Review the material manufacturers processing data, as well as monitor pressures/ fill speeds that produced satisfactory product in previous runs. (MSDS)

• Incorrect storage of pellets:

  Review how the material was stored... was it kept in a cold silo? Were there factors that could have led to absorption of moisture? Was the material stored over the weekend in a drying hopper, and could overdrying be a factor?

• Mold Temperature:

  Raise mold temperature. This will prevent condensation on the mold walls from being carried into the melt. Are you using the same tip as on a previous run? If this is the first run... is the tip 1/16" smaller than the bushing orifice?

• External Moisture Sources

  Ensure the mold is not leaking water onto the cores or cavities. Again this will prevent condensation on the mold walls from being carried into the melt. Is the mold sweating due to the use of chiller water?