Hisson Plastic Machinery Co., Ltd. 

Maintenance and treatment of common faults of injection molding machines

by:Hisson     2020-01-19

Before maintaining the injection molding machine, one must first fully understand the working principles of the machine, such as electrical principles, hydraulic principles and mechanical principles. Secondly, we must follow the four steps of the ancients to see, smell, ask, and cut. Keep a clear head, don't be impatient, first find out which aspect of electrical, hydraulic and mechanical faults belong to, and simply distinguish them according to the following steps: the following are common faults and treatment methods for reference 1.  The oil pump motor does not start 1.  The motor does not rotate, and at the same time, it emits an abnormal sound.  Immediately turn off the emergency stop button and check whether the fuse is blown or loosened, then check whether the three-phase power supply of the motor is normal.  2.  Press the motor start button.  There is no possibility for the motor to sound.  The button switch, the wire of the AC contactor is loose, or the thermal relay moves.  3.  The oil pump is stuck and the motor does not rotate (At this time, the motor has some sound) 4.  If the motor burns 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 wire, or unbalanced and unstable voltage of three-phase power supply) II.  The motor can rotate, but it can not withstand the pressure or the big pump can not withstand the pressure 1.  The electromagnetic coil of the small pump electromagnetic relief valve or the pressure proportional valve does not suck or the internal valve core is stuck by sundries, remove and clean, at the same time, check whether the electromagnet coil is burned, whether the wiring is loose, or the contact is poor.  2.  The oil pump is damaged.  Repair or replace the oil pump.  3.  The oil level is over the bottom, cause the pump to suck empty 4, whether the oil filter net is blocked 5, whether the motor is reversed, commutation 6, air in the oil pump, deflate first 7, control the main valve core of the large pump overflow valve to get stuck, remove the overflow valve to clean, three, does not fit the mold 1, the safety door travel switch wiring loose or damaged, the safety door travel is not pressed down, check that the travel switches of SQ1, SQ2, SQ3 2 and SQ4 are closed.  3.  The valve of the mode-locked solenoid valve is stuck or the socket of the solenoid valve is loose.  4.  The forming switch of thimble receding is not closed.  5.  The system pressure is not: Press (2) Item content repair, 4, no injection or slow speed 1, low injection pressure, too slow speed: increase injection pressure, speed up injection Speed 2, plastic heating temperature bottom: raise the temperature 3, the nozzle is blocked, remove the heating and cleaning 4, the injection time is too short 5, the injection solenoid valve is stuck 6, the injection solenoid valve cannot be powered. Check the electrical reasons, five, not pre-plastic or pre-plastic too slow 1, pre-plastic stop travel switch has been closed, open the stroke of the travel switch, 2, one-way throttle valve closed 3, the material temperature is over the bottom, increase the material temperature 4, the pre-plastic solenoid valve is stuck, remove the cleaning 5, the pre-plastic pressure is too low, increase the pre-plastic pressure 6, the screw enters the foreign body to jam the screw. Remove the screw and clean the feeding barrel 7.  The hydraulic motor is broken and the bearing is stuck.  6.  The screw rotates during pre-molding, but does not feed.  1.  The back pressure is too high.  2.  The cooling water from the feeding port is insufficient, the material in the feeding port is 'bridging '; Adjust the amount of water, take out the plastic block of the sticky structure 3, lack of material, feeding 4, screw break 5, back pressure adjustment is too high, lower back pressure 7, unable to adjust the mold or difficult to adjust the mold 1, system pressure adjustment is over the bottom 2, after the template pull rod nut due to impurities, lack of lubricating oil and grease stuck; When cleaning and repairing the pull rod nut, pay attention to the axial clearance of the four nuts to be consistent during installation, and then add lubricating grease 3.  The die adjusting solenoid valve is stuck or the socket is loose: check and repair 4.  The hydraulic motor of mold adjustment is damaged, repaired or replaced.  8.  The hydraulic oil temperature is too high 1.  The oil pump pressure is too high: properly reduce the working pressure according to the plastic molding process 2.  Insufficient 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, cleaning the cooler 4.  The flow of cooling water is not big enough, or the temperature of cooling water is not low enough.  9.  The semi-automatic operation fails.  The semi-automatic operation of the machine is opened by the safety door and the travel switch is closed, signal the machine to do semi-automatic action to start, then close the mold, touch the SQ4 travel switch, close the mold, and start the injection at the same time, the injection time relay starts timing, after the injection time, start pre-molding, after touching the travel switch at the end of pre-molding, the flow prevention starts.  After touching the travel switch at the end of flow prevention, the cooling time relay starts timing, the mold opening action is made after the time is up, and then the mold is opened, when it comes to the die opening termination travel switch, do the ejection action, when it comes to the ejection termination travel switch, do the ejection withdrawal action, when it comes to the ejection termination travel switch, wait for the safety door to be opened, so that the work goes round and round. It can be seen from the above that if the manual operation is normal, it is generally caused by no signal from the travel switch and the time relay. According to the failure of semi-automatic action in that stage of mechanical cycle, find out the corresponding control components according to the electrical and hydraulic schematic diagrams, and check and solve them.                                

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