Maintenance and treatment of common faults of injection molding machine

    Before repairing the injection molding machine, we must first have a complete and clear understanding of the working principle of the machine, such as electrical principle, hydraulic principle and mechanical principle. Secondly, we should follow the four steps of seeing a doctor in ancient times, that is, seeing, smelling, asking and cutting. Insist on waking up and don't be impatient. First make clear which problems belong to electrical appliances, hydraulic pressure and machinery. Simple identification can be carried out according to the following steps:

    The following are common faults and solutions for reference

    1、 Oil pump motor does not start

    1. If the motor does not rotate and makes an abnormal sound, immediately turn off the emergency stop button, check whether the fuse is blown or loose, and then check whether the three-phase power supply of the motor is normal

    2. When the motor start button is pressed, there is no possibility that the motor makes a sound, the line of the button switch and AC contactor is loose, or the thermal relay acts

    3. The oil pump is stuck, causing the motor not to rotate (there is some sound from the motor at this time)

    4. If the motor is burnt out, repair it according to the original specifications and find out the cause (such as phase failure, overload, poor contact of AC relay, loose contact of motor line, or unbalanced and unstable three-phase power supply voltage)

    2、 The motor can rotate, but the pressure does not rise or the large pump does not rise

    1. If the solenoid coil of the electromagnetic overflow valve or pressure proportional valve of the small pump does not suck or the internal valve core is stuck by sundries, remove it for cleaning. At the same time, check whether the electromagnet coil can be burned, whether the wiring can be loose, or whether the contact is poor

    2. If the oil pump is damaged, repair or replace the oil pump

    3. The oil level is too low to form pump suction

    4. Can the oil filter be blocked

    5. Can the motor be reversed and commutation

    6. There is air in the oil pump. Bleed first

    7. The main valve core of the overflow valve of the control pump is stuck, and the overflow valve shall be removed for cleaning

    3、 Out of mold

    1. The wiring of the safety door travel switch is loose or damaged, and the safety door travel is not pressed down. Check SQ1, SQ2 and SQ3

    2. Sq4 travel switch closed

    3. The mode locking solenoid valve is stuck or the solenoid valve socket is loose

    4. The constituent switch of thimble retreat is not closed

    5. Failure of system pressure: repair according to item (2)

    4、 No injection or slow speed

    1. The injection pressure is low and the speed is too slow: increase the injection pressure and speed up the injection speed

    2. Plastic heating temperature: increase the temperature

    3. Nozzle blockage, remove heating and clean

    4. Injection time is too short

    5. Injection solenoid valve stuck

    6. The injection solenoid valve shall not be energized. Check the electrical cause

    5、 No or too slow pre molding

    1. The pre molding end travel switch has been closed, turn off the striker of the travel switch,

    2. The one-way throttle valve is closed

    3. If the material temperature is too low, increase the material temperature

    4. The pre molding solenoid valve is stuck and removed for cleaning

    5. The pre molding pressure is too low, increase the pre molding pressure

    6. Foreign matters enter the screw and block the screw. Remove the screw and clean the barrel

    7. The hydraulic motor is broken and the bearing is stuck

    6、 During pre molding, the screw rotates but does not feed

    1. Back pressure too high

    2. There is a lack of cooling water from the feeding port, and the materials in the feeding port are "bridged"; Adjust the water volume and take out the plastic block with adhesive structure

    3. Material shortage

    4. Screw break

    5. Adjust the back pressure too high and lower the back pressure

    7、 Unable to adjust the mold or difficult to adjust the mold

    1. System pressure conditioning is too low

    2. The pull rod nut of the rear formwork is stuck due to impurities or lack of smooth oil and grease; When cleaning and repairing the pull rod nut, pay attention to the divergence of the axial clearance of the four nuts, and then add smooth grease

    3. Stuck mode adjusting solenoid valve or loose socket: check and repair

    4. The hydraulic motor for mold adjustment is damaged. Repair or replace it

    8、 Hydraulic oil temperature too high

    1. Too high oil pump pressure: stop according to the plastic forming process and properly reduce the working pressure

    2. Lack of oil in the oil tank: add enough hydraulic oil

    3. The oil cooler is used for too long, full of scale and poor cooling effect. Clean the cooler

    4. The flow of cooling water is not large enough or the temperature of cooling water is not low enough

    9、 Semi automatic operation failure

    The semi-automatic operation of the machine is to open the safety door, close the travel switch, send a signal to make the machine start the semi-automatic action, and then close the mold. After touching the sq4 travel switch, the mold is closed, and the injection is started at the same time. The injection time relay starts timing. After the injection time, the pre molding is started. After touching the pre molded travel switch, the anti flow is started. After touching the anti flow travel switch, The cooling time relay starts timing. When the time is up, it will open the mold, and then open the mold. After touching the mold opening end travel switch, it will do the ejection action. After touching the ejection end travel switch, it will do the ejection action. After touching the ejection end travel, it will wait for the safety door to be opened. In this way, it will cycle back and forth. It can be seen from the above that if the manual operation is normal, it is generally caused by the failure of signal from travel switch and time relay. According to the failure of semi-automatic action in the mechanical cycle, find out the corresponding control components according to the electrical and hydraulic schematic diagram, stop inspection and deal with it.