Electrical system of a Haitian injection molding machine is like its central nervous system. It can be divided into several main parts: computer controller (HMI screen plus CPU motherboard), I/O signal board, analog feedback components like electronic rulers and pressure sensors, servo drive system, and the overall power supply circuitry. These are roughly five main components.

 

Currently, Haitian machines used in our factory are equipped with two main types of computer systems: older, commonly used Hongxun series, some high-end models equipped with imported KEBA system. These are the two most frequently encountered systems in daily maintenance.
1.1 Black Screen and Complete Failure to Start Up
The most crucial factor in whether motherboard can start normally is stability of power supply. Normal operation requires a stable 24V DC power supply, which motherboard internally steps down to 5V and 3.3V to power chips.
The first common cause of this problem is an unclean power supply with excessive ripple. After prolonged use, aging power supplies develop high-frequency noise in their output voltage. This prevents motherboard and CPU from resetting properly, resulting in a black screen and inability to boot.
Another common issue is damaged storage media. Machines operating in high-temperature, high-vibration workshop environments, especially those storing system on memory cards (CF or SD), are prone to sector damage over time. This makes system unreadable and prevents booting.
In practice, following steps are typically taken: First, measure output voltage of power supply in electrical panel. If voltage is below 23.5 volts, or waveform is noticeably unstable, replace power supply immediately. Then, check indicator lights on motherboard. If power light is on but operation light is off, this usually indicates a poor connection or damage to memory card. Try removing and reinserting it firmly. If that doesn't work, re-flash system image.
One more point not to overlook: communication connection between HMI and host machine. Some are network cables, others are dedicated ribbon cables. Shielding layer of this cable must be properly grounded; otherwise, excessive interference can cause unexpected screen blackouts and system crashes.
1.2 Screen Prompting Waiting for Communication, or Communication Disconnecting Directly
This type of fault is quite common. Symptom is that HMI screen appears to be lit normally, but it cannot connect to main control motherboard, meaning HMI and the host machine are disconnected.
During troubleshooting, first check transmit/receive signal indicator lights on motherboard. Normally, they should flash. If lights don't flash at all, it's highly likely that internal communication chip has been damaged by a sudden high voltage. Commonly used RS-485 communication chips and CAN driver chips are easily damaged.
Actual solution is simple: first check for short circuits in 5V power supply on motherboard. Also, many modern bus communication machines have terminating resistors on the lines, typically 120 ohms. Sometimes, a loose or faulty resistor can directly cause communication interruption.

All actions of the entire machine are transmitted via I/O signals. Computer issues commands, which are then sent through this signal line to control various external actuators. If this part malfunctions, operation will definitely be abnormal.
2.1 No Input Signal Response or Inability to Receive Signals
The most obvious symptom on-site is that machine has reached limit position when opening or closing mold, but computer interface does not display "complete" signal.
Inductive switches used on Haitian machines are basically of two types, mostly NPN and PNP. Generally, if indicator light on input panel is not lit, nine times out of ten fuse on common terminal is blown; this is the most common minor problem.
Another more subtle fault is false signal interference. Especially when servo motors and frequency converters are working, surrounding electromagnetic interference is particularly strong. Excess voltage can easily be induced in circuit. Even when mechanical position has not moved, computer may still show a signal connection. This false signal is particularly misleading in repair diagnosis.
Routine troubleshooting steps: Use a multimeter to measure voltage at input terminals. During normal operation, there should be a clear 24-volt jump. If there's no jump, problem lies with wiring or switch. If a specific point on I/O board is completely burned out and unusable, you don't need to replace the entire board. Machine system has a built-in point remapping function, which can remap faulty signal to a reserved spare point for continued use, saving considerable costs.
2.2 No output signal, interface shows action but no actual operation
This phenomenon is also easy to identify. Computer screen shows action has been output, but corresponding solenoid valve externally shows no movement and is completely inactive. These output circuits are generally driven by transistors or small relays.
When troubleshooting, start with the simplest thing: fuse on output power supply side. Many Haitian models have separate fuses for output lines, mostly 10A or 15A. Blowing fuses is commonplace. Ultimately, if internal driver transistor is faulty due to a short circuit, whether it's continuously conducting or completely disconnected, corresponding driver chip must be replaced. Commonly used driver chips like ULN2803 will restore normal output after replacement.

 

Many Haitian MA series and IA Changfeiya series machines on the market are equipped with servo drive systems. Servo alarms are among the most difficult aspects to handle in routine maintenance.
3.1 Servo Alarm Codes and Their Causes
Whether it's original driver or a commonly used external driver brand, alarm meanings are basically same:
E001 and E002 overcurrent alarms mostly indicate broken insulation or leakage in three power lines of motor; in more severe cases, internal windings of motor may be burnt out. E012 overload alarms are generally caused by mechanical jamming, insufficient lubrication, or system pressure parameters being set too high, exceeding motor's rated load. E047 encoder failure is basically due to poor shielding of encoder communication line, resulting in excessive external interference. Driver cannot recognize motor rotor position, causing an alarm and immediate shutdown.
Key points for on-site repair:
When testing motor wiring insulation with a megohmmeter, always disconnect driver's wiring beforehand. Failure to do so will result in high voltage from megohmmeter burning out driver module. This is a common mistake for beginners. Also, braking resistor should be checked frequently. If it is open-circuited and damaged, high voltage generated during machine deceleration will have nowhere to dissipate, eventually damaging servo power module and causing significant losses.

Stability of machine's injection molding accuracy depends entirely on these analog signals. Abnormalities in this area typically manifest as erratic and unstable data.
4.1 Inaccurate Electronic Ruler Position
Common issues include erratic readings of mold opening/closing position and injection position, leading to large deviations in movement and, in severe cases, risk of mold collision.
There are essentially two root causes: either internal carbon brushes of electronic ruler are worn out or there is a break or poor contact in external shielding circuit.
Routine troubleshooting methods:
First, measure reference voltage of electronic ruler's power supply. It's typically 10V or 5V. If voltage fluctuates along with other machine actions, it indicates a decrease in the overall DC power supply's load-carrying capacity, and root cause lies with power supply. A simple and practical anti-interference method is to connect a small capacitor in parallel at signal input location, or to ground electronic ruler's shielding wires at a single point on mainboard. This can significantly reduce interference.
4.2 Abnormal Pressure Sensor Feedback
Symptom is that machine cannot generate high pressure, or pressure fluctuates wildly during pressure holding phase, resulting in unstable product quality.
Most pressure sensors currently use a standard 4 to 20 mA current signal transmission.
The simplest on-site repair method is to connect an external standard pressure gauge for comparison. Check difference between actual pressure and computer display. If difference is significant, directly access machine's calibration interface, adjust zero-point offset and slope parameters. Once adjusted, it should function normally.

5.1 Overheating Causing Automatic Machine Restart
Servo drive generates a significant amount of heat during operation, making it primary heat source within electrical box. Over time, cooling fan filter becomes clogged with dust, hindering ventilation. When internal temperature rises, drive's built-in temperature protection activates, directly cutting off power supply to protect power module, causing machine to stop and restart.
Routine maintenance is essential. Clean filter regularly each month. Never leave electrical box door open while machine is running, as this worsens heat dissipation, allows dust and moisture to enter.
5.2 Various Strange Problems Caused by Loose or Loose Wiring Connections
Injection molding machines operate under continuous vibration for years, causing all wiring terminals inside electrical box to gradually loosen. Loose connections in AC contactors can generate electrical sparks and arcs during operation, radiating a large amount of interference signals. This can eventually lead to inexplicable problems such as computer crashes, parameter loss, and system malfunctions.
Therefore, during annual major maintenance, all terminals on 380V main power supply line must be tightened one by one to eliminate risk of loose connections.

Many times, machine problems are not due to burnt-out parts, but simply internal program logic interlocking.
6.1 Safety Interlock Conditions Not Met
Machine appears normal, but it cannot lock mold, and system does not report any fault codes, making it difficult to find cause after extensive troubleshooting. This is actually because various safety limit switches have not been fully reset, such as safety door switch, ejector pin return, and core pulling limit switch. If any one of these signals is not in place, system directly prohibits mold locking output, which is a low-level logic protection.
During troubleshooting, directly check system's action flow interface; whichever indicator light is not lit indicates which circuit is malfunctioning, making it immediately clear.
6.2 System Zero-Point Data Loss Calibration
After replacing motherboard or when motherboard battery is dead, it is common to encounter situations where all position readings return to zero, and machine's movement becomes completely disordered.
Handling process is also fixed. Manually move mold closing, injection stage, and injection mechanism to their actual physical origin positions, then manually confirm and save system calibration. Zeroing time will restore normal operation.

 

Before any repair, the first important thing is to back up all machine's internal molding parameters and mold formula data to a USB drive. This is crucial to prevent data loss after repair and should become a habit. Never plug or unplug any low-voltage electrical lines or communication signal lines while they are powered on. Sudden voltage surges can easily damage delicate chips on motherboard, causing unnecessary damage.
When cleaning dust from electrical box, use a vacuum cleaner slowly. Do not use an air gun to blow directly at it. Dust contains conductive metal powder, which, when blown out, can cause short circuits and burn out board if it gets damp.
Finally, let's summarize repair approach:
A very practical repair mantra: Check simple external components first, then disassemble complex internal circuits; determine software settings first, then check hardware; for all faults, prioritize checking power supply.
Actual statistics show that over 80% of minor electrical malfunctions are due to small issues like external limit switches, damaged wiring, or loose plugs; about 10% are caused by unclean power supplies or electromagnetic interference; damage to core components like motherboards and servo drives accounts for less than 5%.
Another reminder: when repairing parts involving 380V high-voltage circuits, always strictly adhere to power outage, tagging, and locking procedures. Safety first. After replacing any electrical component, do not immediately put device into production. First, run it under no-load for ten minutes to observe for any abnormalities in temperature and sound. Only resume normal production after confirming there are no problems.