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Problem Possible causes Possible solution
  Brittle mouldings Sharp corners, notches Increase radii
 PE grade has insufficient impact strength Use lower flow and/or lower density grade of PE
 Excessive orientation Increase melt temperature
 Inadequate thickness Increase thicknes of moulding
  Burn marks. Carbonised material at end of flow path Insufficient venting Increase Venting
 Injection speed too high Reduce Injection Speed
 Melt temperature too high Reduce Barrel and Nozzle temperature settings
  Delamination Incompatible masterbatch Ensure PE based masterbatch is used
 Contaminant Check feed for contamination
 Material freezing prematurely Increase temperature settings. Increase gate size
  Demoulding difficulties Poor design, insufficient draft angles Increase draft angles, Incorporate "slip"additive
 Over packing Reduce injection speed and or second stage time/pressure, use higher flow PE grade
 Excessive second stage Reduce second stage pressure and/or time
  Distortion Moulded in stress/ orientation Increase melt temperature. Use increased melt flow index grade of PE
 Ribs too thick Employ more, but thinner ribs to impart stiffness
 Variation in thickness Use ribs for varying thickness rather than solid walls
 Variation in mould cooling Increase cooling channels in difficult to cool areas
 Sink marks Increase second stage pressure and or time
 Gate freezing off too quickly Increase gate size
  Flashing Inadequate Clamp force Increase clamp force. Move mould to a higher clamp force machine
 Excessive vent size Reduce venting
 PE melt flow index too high Change to a low flow grade of PE
 Excessive injection speed Reduce injection speed
  Matt or Streaky surface Gate inappropiately positioned resulting in snake -like jetting Position gate so that the material is forced to change direction immediately upon entering the mould
 Melt disturbance resulting Matt - Gloss pattern Increase melt temperature. Reduce injection speed
 Moisture Dry the polyethylene or masterbatch
 Incompatible masterbatch Change masterbatch to one with a PE base
  Poor Colour homogenisation Back pressure too low Increase back pressure
 Masterbatch not compatible Ensure PE based masterbatch is used
 Barrel size too small, insufficient shots in barrel Move to a larger machine
 Masterbatch add rate too low Use masterbatch with lower pigment concentration at higher add rate
 Temperature too low Increase temperature settings
  Short shots. Incompletely filled mouldings PE melt flow index too low Change to higher meltflow index grade
 Melt temperature too low Increase melt temperature.
 Inadequate vent size Increase venting
 Inadequate thickness Increase thickness
 Insufficient injection speed Increase injection speed
 Insufficient gating Increase gate size or number
  Weak weld lines Melt temperaure too low Increase temperature settings
 Flow of polymer too low Use higher melt flow grade
 Injection speed too low Increase injection speed
 Gate(s) too far from weld line Move gate or increase number of gates

The information contained in these guidelines is provided in good faith and may assist with problem solving and troubleshooting.

The information is offered solely for your information and is not all-inclusive – other variables or constraints may impact the ability of the user to apply them. The user should conduct its own investigations and satisfy itself as to whether the information is relevant to the user’s requirements. The user should not rely upon the information in any way. The information shall not be construed as representations of any outcome for which Qenos assumes any legal liability. Qenos expressly disclaims liability for any loss, damage, or injury directly or indirectly suffered or incurred as a result of or related to anyone using or relying on any of the information. There is no endorsement of any product or process, and Qenos expressly disclaim any contrary implication.