INJECTION MOULDING TROUBLESHOOTING GUIDE
| 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.