| Possible problems |
presumable causes |
Propositional measures |
Embrittlement |
1.
lack
in drying
2.
temperature
too high in processing
3.
too
much recycled materials
4.
unreasonable
design for parts |
1.
full
drying to lower the temperature of barrel
2.
not
more than 20% recycled materials
3.
shorten
the residence time of materials and lower backpressure
4.
enlarge
the sprue size |
| Air
bladder and holes |
1.
incomplete
exhaust and too fast chop-out die
2.
too
high temp of materials
3.
low
injection pressure
4.
lack
in drying for pellets |
1.
enlarge
the exhaust hole and lower the injection speed
2.
lower
the barrel temp and improve injection pressure
3.
fulling
drying of pellets |
| Become
black or gray |
1.
too
high processing temp and too long residence time of
materials
2.
uncleaned
barrel
3.
decomposers
in pellets |
1.
lower
the barrel temp and shorten the residence time of materials
2.
clean
the barrel and use qualified materials |
| Shrink
hole in surface |
1.
lack
in injection pressure and short in pressure hold time
2.
small
size in sprue and high temp of materials
3.
parts
walls too thick |
1.
improve
injection pressure
2.
prolong
pressure hold time
3.
enlarge
sprue size and lower the materials temp
4.
try
to reduce the wall thickness |
| warping |
1.
improper
sprue position
2.
not
well-distributed wall thickness of parts
3.
short
in pressure hold time and cooling time
4.
uneven
mould temp
5.
lack
of reinforced wall |
1.
change
the position of sprue
2.
equalize
the wall thickness of moulds
3.
prolong
the holding and cooling time
4.
change
the mould design |
