Good day, we have a 14 tonne Doosan Excavator and have recently ended up with the thumb cylinder rod becoming bent. There is no sign of contact between the rod and any object, the operator is pretty careful. Could it be a freak or is the thumb relief not set right and the bucket has over powered the tumb cylinder and bent the rod? How can I prove it was machine set up not operator error? Comments + thoughts appreciated Farmer Guy
One way to check is to curl the bucket into the thumb. If the thumb does not retract, then the thumb relieve is to strong.
Agreed. That bucket cylinder has enough power for material breakout, and more than enough power to damage a thumb cylinder when clamping an object. Thumb cylinder relief must be low enough to breakaway when bucket force is applied during clamping. If you choose to have higher clamping force to tightly clamp objects by having relief pressure set high, one should be careful not to clamp and object with the bucket cylinder, rather with the thumb cylinder. Then once the object is clamped, don't curl the bucket.
Pretty much what those two said. Should be able to back off or retract the thumb by curling your bucket in. You could always buy or rent a pressure gauge and hook it up to the pressure side of your thumb circuit. Than you know for sure. Does your machine have plumbing for attachments? Reason I'm asking is to run some attachments you need higher pressure than the factory setting for a thumb. Maybe the circuit is set to run a breaker.??
Good day There is always a possibility to add a crossover relief valve to prevent that kind of damage as always extra cost. Kind regards Uffex
Doosan if it is a -3 and -5 model can use monitor to see pressure of auxillary circuit. Also pressure can be set in the monitor because most have electronic inline reilefs. But i would not rely on that id verify the port relief in the valve it self is set low enough. Seen to many curious operators mess with settings in dash
Is it a direct connect cylinder or a progressive link thumb?