Injection Molding Machine Noise: Causes & Fixes

Pump and motor are not concentric

Adjust concentricity to within 0.1 mm

Loose coupling

Repair or replace the coupling

Internal pump failure

Repair or replace the pump

Low oil level, causing air to be drawn in through the strainer or fittings

Raise oil level to at least 400 mm above the strainer and fittings

Air drawn in through the rotary shaft seal

Replace the rotary shaft seal

Clogged oil strainer due to contamination

Clean the strainer and filter the oil

Loose return line or return pipe positioned above oil level, introducing air

Tighten the return line; extend the return pipe below the oil surface

Worn motor bearings

Replace the bearings

Faulty motor winding

Replace or repair the motor

Incorrect motor wiring (noise increases as system pressure rises)

Reconnect the wiring according to the correct wiring diagram

Air trapped in the pilot stage chamber

Improve sealing; raise and lower the pressure setting several times to bleed air

Clogged damping orifice in the main spool due to contamination

Clean the valve body to restore unrestricted flow through the orifice

Damaged or mismatched pilot valve and seat

Repair or replace as needed

Spring deformed or incorrectly installed

Check and replace the spring

Excessive flow through the remote control port

Reduce flow through the remote control port

Hydraulic oil viscosity too high or too low

Replace with oil of the correct viscosity

Resonance with other circuit components

Ensure other pressure settings are not close to the relief valve setting

Air is mixed into the hydraulic oil or not completely vented from the hydraulic cylinder

Vent the air from the hydraulic oil and the hydraulic cylinder

The cylinder head oil seal is too tight, or the piston rod is bent

Replace the oil seal or straighten the piston