1. Fault Phenomenon 1: Mold adjustment unavailable (no movement when pressing mold adjust key)

Possible Causes

1. Safety circuit / door limit not closed: Poor contact, broken wire or loose connection of front/rear safety door limit switches; safety relay not energized, PLC blocks mold adjustment output.
2. Incorrect mold adjustment parameters / mode setting: Mold adjust pressure or flow set too low; mold adjust lock function enabled; manual mode not activated. For some machine models, mold adjustment is only permitted when injection retraction and mold clamping home position are reached.
3. Hydraulic machine: Oil circuit / valve assembly failure: Burned coil or spool sticking of mold adjustment solenoid valve; mold adjust relief valve pressure set too low; insufficient pump pressure; blocked or leaking oil pipe, pressure cannot build up.
4. Electric mold adjustment model: Power and communication failure: Alarm on mold adjustment servo drive, faulty servo motor; broken servo encoder wire, communication abnormality; servo enable not activated.
5. Mechanical seizure (most frequent): Tiebar nut seizure, rust due to insufficient thread lubrication; seized mold adjusting nut; scratched platen guide post or foreign object jammed; mold not fully opened, platen pushing against mold leading to overloaded mold adjustment.
6. Electrical signal fault: Damaged or displaced mold adjust home sensor / proximity switch; no mold adjust output signal from PLC; burned contacts of contactor or relay.
7. Load protection triggered: Overload, current or pressure protection activated, system cuts off mold adjustment output directly.

Corresponding Solutions

• Check front and rear safety door switches, confirm door fully closed, intact wiring; replace faulty limit switches and reset safety relay.
• Enter parameter page: Disable mold adjust lock; appropriately increase mold adjust pressure and flow; confirm machine under manual mode; verify home position of mold clamping and injection unit.
• Hydraulic machine: Inspect mold adjustment solenoid valve, clean spool or replace coil; recalibrate pressure of mold adjust relief valve; check oil pump and pipeline for leakage or blockage.
• Electric mold adjustment: Check alarm codes on servo drive; inspect servo power cable and encoder cable; restart servo and re-home servo system.
• Mechanical seizure:
  1. Fully open mold, remove mold and test mold adjustment under no-load condition.
  2. Clean tiebar threads and apply high-temperature grease.
  3. Inspect tiebar nuts. Mild seizure can be released by low-speed jog forward/reverse; severe seizure requires disassembly and maintenance.
• Test PLC output and relay contacts with multimeter; reposition or replace home proximity switch.
• Check system alarm log, clear overload alarm and locate root cause of overload (mechanical seizure to be checked first).

2. Fault Phenomenon 2: Mold adjustment functional but abnormal noise during operation (rattling, friction sound, buzzing / howling noise)

Classify noise types for quick diagnosis: Metallic rattling / squeaking friction / motor or hydraulic howling

Possible Causes

1. Poor mechanical lubrication: Insufficient grease on 4 tiebar threads, dry friction resulting in squeaking or sanding noise; insufficient lubrication and internal wear of mold adjusting nut.
2. Worn tiebar nuts with uneven clearance: Inconsistent wear of four mold adjusting nuts causes eccentric loading of platen and periodic rattling; scratched threads with iron debris.
3. Worm gearbox / gear wear (common on electric mold adjustment): Insufficient oil, pitting or chipped gear teeth in reduction box leads to periodic clunking noise during rotation; damaged bearing.
4. Howling from mold adjust servo motor / hydraulic pump: Servo motor howling under heavy load; unstable throttling of mold adjust valve or air entrapment in hydraulic oil generates high-frequency buzzing howling on hydraulic mold adjust machines.
5. Friction between platen guide bushing and guide post: Insufficient lubrication or scratch on guide bushing causes friction noise during platen movement; eccentric wear of guide bushing.
6. Foreign matter entering thread pair: Iron scraps and dirt trapped between tiebar thread and adjusting nut cause intermittent impact noise during rotation.
7. Unbalanced mold adjusting force: Uneven tightness of four tiebars leads to tilted platen and unilateral impact during mold adjustment; forced mold adjustment with mold not fully separated.
8. Chain-driven mold adjustment: Loose or worn chain: Excessively loose chain jumping teeth creates rattling impact noise; insufficient chain lubrication.

Corresponding Solutions

• Power off and shut down machine, remove old grease on tiebar threads, apply dedicated high-temperature grease, manually turn nuts to ensure full lubrication.
• Inspect wear condition of four tiebar nuts, clean iron debris; recalibrate preload of four tiebars to ensure uniform stress; replace nuts if threads are severely scratched.
• Check oil level and oil quality of electric mold adjust reduction box; replace reduction box / bearing directly if gears are damaged.
• Hydraulic machine: Check hydraulic oil level and oil quality, bleed air; clean mold adjustment solenoid valve to stabilize mold adjust pressure and flow. Electric machine: Check servo load and tune servo gain parameters.
• Lubricate guide posts and guide bushings; repair or replace severely scratched guide bushings.
• Disassemble and clean iron debris and impurities inside thread pair, check for wear and metal chipping; filter hydraulic oil if needed.
• Perform no-load mold adjustment test, recalibrate four tiebars to guarantee platen parallelism; prohibit forced mold adjustment with mold loaded.
• Chain type mold adjustment: Adjust chain tension, apply chain lubricant; replace chain if heavily worn.

3. Quick Troubleshooting Sequence (Standard Maintenance Procedure, directly applicable to documents)

1. Confirm alarm information and record PLC / servo alarm codes.
2. Verify safety door status, operation mode and preconditions for mold adjustment.
3. No-load test (remove mold): Judge whether abnormal noise / failed mold adjustment is caused by mold or machine body (mechanical/hydraulic/electrical).
4. Observe mold adjustment pressure and current curve to judge overload condition.
5. Locate noise source: Distinguish noise from tiebar nut area / reduction box / servo motor / valve block & oil pump.
6. Lubricate and clean thread pair, inspect tiebar nuts.
7. Troubleshoot electrical / oil circuit / servo system item by item.
8. No-load trial run after repair, then test mold adjustment with mold installed.

4. Safety Precautions (Mandatory)

• Before mold adjustment maintenance, shut down machine, cut off main power supply, release system pressure and hang maintenance warning sign to prevent accidental movement.
• Forbid mold adjustment under mold clamped condition, otherwise tiebars and adjusting nuts are easily damaged.
• Keep personnel away from moving platen zone during no-load test.
• System pressure must be fully released before servicing hydraulic components.