Common failures and troubleshooting of die casting machine!

Time:2020-03-18 09:13:35 / Popularity: / Source:

Once failure of die-casting machine is threatened, operator should pay great attention to it, calmly observe, judge location of failure and possible cause, and determine a feasible maintenance method. Operators must be reminded to work in accordance with company's "working procedures" and not to operate in violation of regulations in order to avoid causing greater accidents. To deal with machine failure, whether it is a cold room die casting machine or a hot room die casting machine, following steps can be performed:
1) Determine symptoms and location of fault by looking, listening, and testing.
2) Analyze possible cause of failure.
3) Check equipment operation records and fault files.
4) Determine corresponding processing method and work steps.
5) Hands-on maintenance.
die casting 

1. Oil pump cannot start

Inspection and analysis: Press start button of oil pump observe whether motor relay is closed.

1.1 If relay is not closed, check following points:

1) Whether motor thermal relay is activated or damaged.
2) Whether power circuit is normal (check with a multimeter).
3) Whether start and stop button contacts are normal and control circuit is open.
4) Whether relay coil is damaged (check with a multimeter).

1.2 If relay is activated after oil pump starts, check:

1) Whether oil pump is damaged or stuck.
2) Whether wiring from relay to motor is normal.
3) Whether oil pump is damaged or over-tightened. It should be easy to dial coupling by hand, and a gap of about 3 ~ 5mm should be suitable for axially moving coupling.

2. Press oil pump start button, thermal relay trips

Inspection and analysis: Press oil pump start button, thermal relay trips. This is related to whether current, load, and three-phase resistance are symmetrical.
1) Motor thermal relay is damaged or setting current is too small.
2) If voltage is too low, current will increase or three-phase voltage will not be balanced.
3) Three-phase winding resistance of motor is unbalanced.
4) Total pressure or double pump pressure is adjusted too high, causing machine to overload and trip.
5) Oil pump is damaged or over-tightened, causing motor to overload and trip.

3. No total pressure

Inspection and analysis: After oil pump is started, press lift button, first observe pressure and flow indicating ammeter for indicated value to determine whether there is current in solenoid coil of proportional pressure valve (proportional relief valve), and distinguish between electrical and hydraulic faults.

3.1 Check if there is current output

1) Whether oil pump is reversed (when a person faces direction of oil pump shaft, clockwise rotation is forward direction).
2) Check relief valve for improper adjustment or stuck.
3) Check if shut-off valve is closed.
4) Whether throttle valve of proportional relief valve is missing or loose.

3.2 Check if there is no current output

1) Whether rectifier board is normal, and whether pressure proportional amplifier board is improperly adjusted or damaged.
2) Observe whether computer works normally, press pressure button with your hand to see whether there is input at corresponding point on the computer, and whether there is any output at total pressure point. If there is no output from total pressure point, computer failure or back door is not closed.
3) Check whether circuit between electric proportional plate output and oil valve is normal, and whether electric proportional coil is normal.
4) Check if pressure dial is normal.

4. No automatic

If manual actions are normal but there is no automatic action, you should check whether safety door limit switch is normal and whether relevant action returns to origin (according to requirements of machine's instruction manual). For example, Lijin horizontal cold room die casting machine should meet following conditions before automatic operation: safety door input signal is lit; automatic input signal is lit; mode-locked input signal is lit.
If manual action is abnormal, it should be checked and eliminated first.

5. Can not adjust mold

Inspection and analysis: Operation of mold adjustment method cannot be realized by selecting mode of adjustment. Following should be checked:
1) Whether conditions of mold adjustment movement are met.
2) Whether mold adjustment pressure is set too low.
3) Whether manual operation mode is correct.
4) If there is no problem in above check, check following:
① Whether mold adjustment hydraulic motor is stuck or mold adjustment motor is damaged.
② Check if valve core of mold adjustment hydraulic valve is stuck.
③ Whether transmission pair of mold adjustment mechanism is worn or stuck.

6. No action on the whole machine

Inspection and analysis: After starting oil pump, the whole machine has no manual or automatic action. Press pressure button (pressure and flow parameters have been set) by hand to see if there is pressure.

6.1 Check if there is no pressure

1) Whether rectifier board is damaged or fuse is burnt out.
2) Whether input and output of P01 board is normal.
3) Check whether proportional relief valve is properly adjusted, damaged or stuck.
4) Whether computer works normally.
5) Whether pressure dial is damaged, line is normal, or pressure flow setting is too small.

6.2 Check if there is pressure

1) Whether 14-way amplifier board is normal.
2) Whether 0V wiring of all oil valve lines is normal.

7. Do not lock mold

Inspection and analysis: Close safety door, press mold clamping button (if a mold is installed, choose a slow speed to avoid damaging mold), and observe whether mold clamping indicator on the panel of electrical box is on or host computer has a mold clamping signal output .

7.1 Check if there is no signal output

1) Whether there is signal input, if there is no signal input, check external circuit.
2) Whether ejector pin returns to its position.
3) Check whether limit switch is damaged when mold is locked in place.
4) If all mode-locking conditions are satisfied and no mode-locking signal is output, computer is damaged.

7.2 Computer has a signal output, but it still does not close mold.

1) Whether clamping pressure is normal (press clamping button to observe pressure value on pressure gauge).
2) Whether 14-channel amplifier board is normal (its input and output lights are on at the same time when working).
3) Whether normally slow valve is properly adjusted or damaged, whether mold opening and closing valve is incorrectly adjusted or damaged.
4) Check whether connection of mold-locking output from electrical box to oil valve is normal, and whether solenoid of mold-locking solenoid is normal.
5) Whether clamping cylinder is damaged.
die casting mould 

8. No low-voltage mold clamping

Inspection and analysis: Observe whether low-voltage mold-locking indicator on the panel of electrical box is on.
1) If light is off, check low-voltage mold-locking sensor switch to see if it can be sensed or damaged.
2) If light is on, check whether low-voltage dial is adjusted or damaged.

9. No high voltage mold clamping

Inspection and analysis: If there is no high voltage when mold clamping moves to high voltage induction switch, check whether high voltage induction switch is damaged or sensed. The total pressure is set too low and there is no high voltage mold clamping.

10. No constant speed close mold

Inspection and analysis: observe computer for constant speed input and output.
1) If computer has no constant speed input, then check whether line from external constant speed selection knob to computer is normal.
2) If computer has input or no output, computer is faulty.
3) Check if computer has input and output: whether 14-way amplifier board works normally; whether circuit from 14-way amplifier board to oil valve is normal; whether oil valve coil is damaged.
4) Spool of normal-speed hydraulic valve is stuck by a foreign body or normal-speed flow is too small.

11. Do not open mold

Inspection and analysis: First, observe whether mold opening indicator on main electrical box panel is on, and whether main computer has input and output.

11.1 No signal output check items

1) Whether mold opening and inductive switch is normal.
2) During manual operation, mold opening signal lamp on the computer should be on; otherwise, check whether wiring between mold opening button and computer is normal. If normal, computer is faulty.
3) During automatic operation, if contact of automatic selection knob is poor (vibration may cause automatic signal to break when material is being beaten), and an action cycle cannot be completed.

11.2 If computer works normally (input and output), check

1) Whether 14-way amplifier board works normally.
2) Whether circuit of 14-way amplifier board to oil valve is normal, and whether oil valve coil is damaged.
3) Whether mold opening spool is stuck by foreign objects.
4) Whether mold opening pressure is abnormal (observe pressure gauge).
5) Whether fixing nut of piston rod and cross head is loose.
6) Sudden power failure after mold is locked, and mold may not be opened for a long time. At this time, the total pressure should be set to maximum, select fast mold opening, press and hold pressure button, and then click mold button to open mold.
7) Check if there is any leakage in lock-up cylinder.

12. No shot action (referred to as no material)

Inspection and analysis: Manually operated punch movement is normal, but there is no injection action when automatic, then check following (hot chamber die casting machine should be removed for inspection):
1) Whether manual and automatic selection knob is normal.
2) Mold-locking termination sensor switch does not cooperate well with mold-locking confirmation limit switch. Mode-locking termination sensor switch sensed, but mode-locking termination confirmation limit switch is not pressed, or limit switch is damaged.
3) Injection termination sensor switch is damaged. (Not available in hot chamber die casting machine)
4) Whether speed of injection and hammer return valve have electrical signals, whether valve core moves.
5) Injection time is too short or speed is adjusted too slowly.
6) Fuel injection cylinder is damaged.
7) No pressure in hydraulic system.
8) Whether it is in place before buckle. (Cold chamber die casting machine does not have this item)

13. No second-speed shot movement

Inspection and analysis: Manual operation of punch moves normally, and there is no second-speed shot movement during automatic operation. First, you should observe whether computer has a two-speed injection signal input, whether there is a two-speed signal output when it is automatic (hot head die casting machine should be removed for inspection).

13.1 No signal input check items

1) Check if second speed sensor switch is normal.
2) Whether injection time is set properly.
3) Whether first speed exercise is normal.

13.2 Computer has signal input and output inspection items

1) Check if 14-way amplifier board has input and output to oil valve.
2) Whether oil valve coil is normal.
3) Whether two-speed control valve is normal and whether two-speed cartridge valve is normal.
4) First speed travel is too long, and second speed has no travel.
die casting mold 

14. Shot weakness

Inspection and analysis: first check whether there is a second-speed signal and whether there is a second-speed shot. If there is no second-speed, see second-speed fault analysis.
1) Whether first and second speed adjustment meets requirements and whether second speed flow adjustment can normally open two speed flow valve.
2) Whether nitrogen pressure of fast-pressure injection accumulator is within required range.
3) Whether injection pressure setting is too small.

15. Shot out pressure

Inspection and analysis: When pressure of the punch drops sharply during shot, check
1) Whether injection cylinder, pressure reducing valve and cartridge valve are leaking inside.
2) Whether shut-off valve is tightened.
3) Whether there is nitrogen, nitrogen pressure is insufficient or nitrogen pressure is too high.
4) Accumulator is faulty.

16. Furnace temperature cannot be controlled

Inspection and analysis: After heating furnace for a period of time, its thermometer pointer does not move. Reasons are as follows:
1) Reverse, loose or damaged probe wire.
2) Thermometer is damaged.

17. Alarm

Inspection and analysis: If machine is in an alarm condition during manual or automatic operation, that is, alarm lamp of electrical box flashes, and speaker on electrical box is buzzing, it may be caused by following factors (when machine has a fault display function, it can be handled directly according to fault location displayed on display screen):
1) Mold-clamping limit alarm: mold-opening termination, mold-clamping termination, induction switch, confirm whether limit switch is blocked by foreign objects at the same time.
2) Abnormal alarm for mold clamping protection: During automatic production, low-voltage mold clamping protection time is up, but mold clamping action is not completed.
3) Voltage of computer battery is too low: PLC program battery voltage of PLC is too low, battery must be replaced as soon as possible to avoid program loss.
4) Elbow lubrication alarm: Oil pressure of elbow cannot reach set pressure.
5) Ejector limit alarm: Ejector pin out limit and pin return limit are sensed by foreign objects at the same time.
6) Core-pulling limit alarm: Limit switch is ON at the same time before and after core-pulling stroke;
7) Motor overload alarm: Motor is overloaded and motor stops rotating at the same time.
8) Moulding limit alarm: Mould thin and mould thickness limit switch is OFF.

18. No eject

Inspection and analysis: Ejector cylinder cannot achieve ejector action. You should first observe whether ejector work indicator on the panel of electrical box is on or computer has a signal output.

18.1 If indicator is off or there is no signal output from computer, check

1) Whether mold is in place.
2) If core is installed, whether core is out of limit.
3) Whether eject limit switch is damaged.

18.2 Check if computer has a signal output

1) Whether pressure of ejector pin is normal (observe pressure gauge).
2) Whether 14-channel amplifier board is normal (observe whether eject output indicator on 14-channel amplifier board is on).
3) Whether line from 14-way amplifier board to hydraulic valve is open, and whether oil valve coil is normal.
4) Whether eject oil valve is normal and whether eject oil cylinder has internal leakage.
5) Ejector pin of mold is stuck and ejector pin cannot be ejected.

19 Computer failure

Inspection and analysis: Observe indicators on the computer PLC and perform following analysis:
1) POW power indicator is off, indicating no power supply; green light indicates normal.
2) ALM lights up red, indicating that CPU is not working properly; lights off indicate normal.
3) BAT lights up red, computer battery fails; lights up yellow, computer battery power is not enough; lights off indicates normal.
4) RUN lights up green, indicating that CPU is working normally; lights are off, indicating that CPU is not working properly.
die casting mold 

20. Oil temperature of hydraulic system is too high

Inspection and analysis: After machine works continuously for a period of time, oil temperature of hydraulic system is too high (normal oil temperature 15 ~ 55℃), following items should be checked:
1) Insufficient amount of cooling water is required.
2) Too much dirt in the cooler failed to clean up as required.
3) Storage capacity of hydraulic oil in the tank is lower than minimum oil level line.
4) Hydraulic system has internal leakage.
5) Water inlet and outlet of cooler are reversed, and cooling effect is poor.

21. Leakage of oil cylinder

Leakage of oil cylinder is one of causes of various failures of oil cylinder.
Leakage of oil cylinder includes two cases of external leakage and internal leakage. External leakage refers to external leakage of cylinder barrel, cylinder head, cylinder bottom, oil port, exhaust valve, buffer adjustment valve, cylinder head and piston rod. It can be directly observed from outside. Internal leakage refers to leakage of pressure oil from high-pressure chamber inside cylinder to low-pressure chamber. It occurs at the joint between piston and cylinder inner wall, piston bore and piston rod. Internal leakage cannot be directly observed. It is necessary to pass pressure oil unilaterally, stop piston at a certain point or after terminal, observe whether other port leaks oil to determine whether there is internal leakage.
Regardless of external leakage or internal leakage, main causes of leakage are poor seals and poor joints. Secondly, there is internal leakage caused by pressure expansion of cylinder barrel, and external leakage is caused by poor welding of cylinders with welded structures.

22. Gooseneck leakage (hot cell machine)

1) Taper of pot is damaged and needs to be repaired.
2) Taper of nozzle body is not correct. Nozzle body that meets requirements should be replaced.
3) Installation method of nozzle body is not correct. Clean cone hole and nozzle of pot, reinstall it according to correct method.

23. Plug (hot room machine)

Plug nozzle refers to fact that alloy solidifies in the nozzle head or nozzle body, cannot continuously produce, which is mainly caused by insufficient temperature. In case of such problems, nozzle temperature needs to be raised or directly heated by gas.

24. Card hammer head

1) Check whether piston rod and center of pot are aligned. Install a hammer to see if it can be rotated by hand. If it can be rotated, it is aligned.
2) Whether furnace temperature is normal, see if temperature displayed on furnace temperature meter is in the range of 400 ~ 430 ℃. (Hot chamber machine)
3) Because slag is not cleaned for a long time, slag accumulates in the furnace or alloy material in the furnace is too small. Generally, normal alloy liquid level is about 3 cm from crucible. (Hot chamber machine)
4) Mold gate sleeve does not fit well with feed barrel. (Cold room machine)

25. Without deduction (hot room machine)

First observe whether indicator light on the front panel of electrical box is on or whether main computer has a signal output.

25.1 No signal output check items

Check for signal input before buckle.

25.2 Check items for signal output

1) Whether connection from output point of computer to oil signal cable is normal.
2) Whether adjustment of beating pressure is normal (observe beating pressure gauge).
3) Whether nozzle oil valve and oil cylinder are normal.
Note: If there is a mold, it should be closed before buckling, so as not to knock mold off before buckling.

26. Without deduction (hot room machine)

Analysis: Check whether indicator light on the panel of electric box is on or whether computer has a signal output.

26.1 If there is no signal output

Then check whether signal after buckle is input. For example, check whether two-speed travel switch is pressed during automatic or semi-automatic operation.

26.2 If there is signal output check

1) Whether adjustment of beating pressure is normal (observe beating pressure gauge).
2) Whether 14-bit amplifier board is normal and connectiobuckled from output point to oil valve line after computer is normal.
3) Whether nozzle oil valve and oil cylinder are normal.

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