Injection Molding Machine Chapter 5
V3.0
5-15
3. Hydraulic part
Symptom Possible causes Solution
3.1 Pump noisy A Sucking side air leakage
B Coupling damaged
C Motor damaged
D Pump damaged
A Check O ring or packing on
filter suction line
B Check rubber gasket of coupling
C Check motor
D Check pump
3.2 No system pressure A PV board damaged or
improper adjustment
B PV fuse burnt out or no
power
C Loose wiring of proportion
valve
D Proportion valve
seizure/damage
A Adjust PV board or replace
B Check or replace fuse (2A)，
Replace transformer PT2
C Check proportion valve
connecting wire
D Clean/replace proportion valve
3.3 Pressure unstable
A Air is in proportion valve
B Suction pipe air leakage
C Oil viscosity too low or too
high
D Oil contaminated
/deteriorated
A Expel air in proportion valve
B Check according to 3.1 above
C adjust oil temperature(20-50℃)
D change hydraulic oil
3.4 Vibration during
operation
A Air in system line
B lubrication not enough
C Hyd. cylinder damaged
A Expel air in cylinder or system
line
B more lubrication
C. Check hydraulic cylinder
3.5 Machine
inoperative
A Pressure insufficient
B Flow insufficient
C Directional valve no signal
D Directional valve seized
E Hyd. cylinder leakage
F Back pressure too high
A Increase pressure
B Increase flow
C Check signal wire & terminal
D Clean direction valve
E Replace piston oil seal
F Decrease back pressure
3.6 Hydraulic system
oil leakage
A Oil pipeline connector
loosened
B Hyd. hose aged
A Tighten the bolt or nut
B Replace hydraulic hose
3.7 Cylinder leakage A Bolt loosened
B Cylinder oil seal
damaged/aged
A Tighten nuts
B Replace cylinder oil seal
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