Plastic Blow Molding Tips
| Polymer sticking to core rods | Melt temperature
is too hot Parison mold temperature is too hot High or low packing or holding pressures Hot core rods Hot core rod tip Low lubricant level in resin |
| Polymer sticking to parison mold | Melt temperature
is too hot Parison mold temperature is too hot Packing or holding pressure is too low Packing or holding time is too short Low lubricant level in resin |
| Short moulding | Loss of heat in
the parison mold Loss of heat in the extruder or manifold Loss of injection pressure Loss of holding pressure Loss of screw RPM Foreign material is blocking the nozzle orifice. Nozzle is frozen off due to low temperature in base Manifold is too cold Nozzle orifice is too small Not enough preform time Hopper is empty |
| Neck folds and shoulder cuts | Neck zone
temperature is too cold Melt temperature is too cold Core-rod temperature is too cold Injection pressure is too high Holding pressure is too high Holding time is too long Cure time is too long |
| Parison Flashing | Melt
temperature is too hot Parison mold temperature is too hot High injection pressure High holding pressure Low clamping pressure Nozzle is damaged or not seated correctly Mold construction is poor Long, high-pressure, preform time Mold coolant lines are plugged |
| Pigtails | Reverse
RPM is too high Decompress time is too long. |
| Incomplete Threads | Neck
zone is too cold Melt is too cold Injection pressure is too low Holding pressure is too low Holding time is too short Poor venting in parison mold Insufficient blow pressure |
| Rocker bottoms | Blow
time is too long Poor blow mold venting Poor cooling in blow mold bottom Melt temperature is too high Cycle is too fast |
| Warped side walls | Insufficient
blow time Insufficient blow pressure Poor mold venting Poor mold cooling Low melt temperature Parison temperature is too low Cycle is too fast |
| Poor gates (fish eyes, flash, tails, etc.) | Too
much decompress, RPM or time (fisheyes only) Not enough slug on parison bottom (fisheyes and holes only) Too much slug on bottom of parison (tailsonly) Not enough decompress, RPM or time (drool and tails) Bottom zone is too cold (tails) Manifold is too hot (fish eyes) Manifold too cold (tails) Inadequate external tip cooling (fish eyes) Insufficient packing time Insufficient cure time Insufficient hold pressure |
The
injection moulding guide is based on our current knowledge and
experience. In view of the many factors that may affect processing and
application, this data does not relieve processors from the
responsibility of carrying out their own tests and experiments; neither
does it imply any legally binding assurance of certain properties or
suitability for a specific purpose. We expressly disclaim 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 in this documents. We expressly disclaim any contrary
implication.
