Before visiting the machine, check:

• Available hours and maintenance records
• Number of mold changes (more changes = more wear on tie bars)
• Original manufacturer specifications and manuals available
• Reason for selling (upgrade? shutdown? problem machine?)

On-site mechanical inspection:

Injection unit:

• Check screw and barrel for wear marks. Measure screw outer diameter at feed zone vs metering zone
• Run screw rotation at low speed - listen for unusual noise
• Check barrel heater bands: heat to setpoint and measure actual temp with contact pyrometer
• Inspect nozzle tip and check ring for scoring

Clamping unit:

• Check tie bar parallelism and straightness. Uneven wear indicates alignment issues
• Run through full open/close cycle at low speed - check for smooth movement
• Listen for hydraulic cylinder seal noise (chattering = worn seals)
• Ejector system: cycle fully forward and back

Hydraulic system:

• Check oil temperature: should be below 55 degrees C after warm-up
• Inspect oil for water contamination (milky appearance) or burnt smell
• Leak test: run at full pressure and hold - check for pressure drop over 30 seconds
• Look at all hose condition (dry rot, bulging, cracked fittings)

Electrical:

• Turn controller on and off to check for parameter battery backup failure
• Check all safety gates and limit switch function
• Verify heater thermocouple readings match pyrometer

Test run:

• Run at least 20 cycles with a simple mold
• Check shot weight consistency over 10 consecutive shots
• Record cycle time and compare to spec
• Verify the machine can reach and hold its rated injection pressure

Red flags - walk away if:

• Maintenance records falsified or missing
• Tie bar nut tightening marks show recent major adjustment
• Oil smells burnt (indicates overheated operation)
• Platen surface has been re-machined (possible crash damage)

Where are you looking for used machines? Share your experience below.

你在实际生产中遇到过类似问题吗？欢迎留言讨论。