| Defective phenomena |
| Causes |
Countermeasures |
| 1) Flash |
1. Too high fluidity
2. Slow crystallization speed
3. Small influence from shear
rate to viscosity |
Reduction of pressure which is the main cause of flash
Decrease injection pressure or
holding pressure
Set the V-P switching position to
the rear side
Decrease injection speed
Lower cylinder temperature
Enlarge sprue and runner
Change to high-flow grade |
Acceleration of resin solidification
Lower mold temperature
Lower cylinder temperature
Improvement of mold precision and prevention of mold deformation
Check mating surface of mold
Check heat balance in heater etc. Do not make mating surfaces in places where no flash is required |
| 2) Short shot |
1. Insufficient fluidity
2. Insufficient degassing /
No gas vent or clogging of
gas vent |
Measures in molding conditions
(1)
Insufficient fluidity
Increase injection speed or
pressure
Raise cylinder temperature Set
the V-P switching position to the
front side
Raise mold temperature
(2) Insufficient degassing
Decrease injection speed or
pressure
Lower cylinder temperature
Make the V-P switching position
small
Decrease clamping force |
Mold countermeasures
Provide gas vent
Carry out mold maintenance
Change number or position of
gates
Enlarge gate size
Eliminate uneven wall thickness
of molded parts
Material countermeasures
Change to high-flow grade |
| 3) Gas burn |
1. Insufficient degassing
2. No gas vent or clogging
of gas vent
3. Too high injection speed |
Measures in molding conditions
Decrease injection speed or
pressure
Lower cylinder temperature
Set the V-P switching position
to the rear side
Decrease clamping force
Peripheral machinery countermeasures
Adopt vacuum pulling
equipment |
Mold countermeasures
Provide gas vent
Carry out mold maintenance
Change number or position of
gates
Use porous steel etc. |
| 4) Haze |
1. Poor transcription due to gas
2. Influence of temperature in
transcription |
Measures in molding conditions
Lower cylinder temperature
Set the V-P switching position to
the rear side
(1) Poor transcription due to gas
Raise mold temperature
Decrease clamping force
(2) Influence of temperature in
transcription
Lower mold temperature |
Mold countermeasures
Provide gas vent
Carry out mold maintenance
Change position of gates
Carry out mold cooling
Material countermeasures
Change to a low-gas grade |
| 5) Sink mark, void, blister |
1. Shrinkage due to thick wall
shape
2. Entrapment of gas or air |
Measures in molding conditions
Decrease injection speed
Lower cylinder temperature
Increase holding pressure
Lower mold temperature
Enhance pre-drying
Prolong cooling time
(blister countermeasure) |
Mold countermeasures
Reduce wall thickness of molded
parts
Carry out mold cooling
Provide gas vent
Carry out mold maintenance
Enlarge gate and runner
Material countermeasures
Change to a low gas-grade |
| 6) Black streak and discoloration |
1. Heat generation by shear
force at injection or
plasticization process
2. Heat reaction |
Measures in molding conditions
Decrease injection speed
Raise cylinder temperature
Decrease screw speed
Decrease back pressure
Carry out nozzle backward
molding
Molding machine countermeasures
Use low-compression screw
Avoid using Ni treated screw |
Mold countermeasures
Provide corner R (radius)
Enlarge gate size
Material countermeasures
Change to low-corrosive grade |
| Defective phenomena |
Causes |
Countermeasures |
| 1) Release defect |
1. Stick in mold due to shrinkage
2. Adhesion between mold
and resin |
Measures in molding conditions
Lower mold temperature
(or raise, depending on the
situation)
Lower cylinder temperature
Prolong cooling time
Decrease holding pressure
Shorten holding time
Decrease ejection speed |
Mold countermeasures
Enlarge taper
Polish mold surface
Carry out surface treatment of
the mold |
| 2) Mold deposit |
1. Attaching gas |
Measures in molding conditions
Lower cylinder temperature
Shorten residence time
Enhance pre-drying
Raise mold temperature
Decrease clamping force
Peripheral machinery countermeasures
Adopt vacuum pulling equipment |
Mold countermeasures
Provide gas vent
Carry out mold maintenance
Material countermeasures
Change to a low-gas grade |
| 3) Mold corrosion |
Metal corrosion due to gas
originating from PPS gas |
Measures in molding conditions
Lower cylinder temperature
Shorten residence time
Enhance pre-drying
Decrease clamping force
Peripheral machinery countermeasures
Adopt vacuum pulling equipment |
Mold countermeasures
Provide gas vent
Carry out mold maintenance
Use stainless steel material
Carry out surface treatment
of the mold
Material countermeasures
Change to low-corrosive grade |
(481KB)