Hey, my dash 3 120 hitachi is making a grinding noise when i release the control while slewing. It seems to me that the brake hasn't enough oil pressure to stop straight away. It does lock on after a few seconds but it takes longer than it should. Any help please!
Brake should be spring applied, pressure release. Does it act the same in either direction?
Yes its the same either way. Is the spring being applied located in the head of the slew motor?
I believe so, should be like 8 springs in a circle I think, with a short stack of steel and friction disks below that.
maybe a broken spring or some friction material came off a disc. how many hours on the machine?
There should be a delay in the brake being applied. Its the crossline relief valves that brake the upperstructure to a stop, Normally a few seconds after it stops then the brake is applied. On this model when you swing left or right, or roll the arm in, the pressure sensors send a signal to the controller which De energizes the solenoid which releases the brake. There's a lack of info in the manual about the delay system but i'd imagine that a certain amount of seconds after both of the pressure sensors lose the signal, the controller will apply the brake. Is there any excess heat in the head of the motor that could indicate friction discs dragging or binding?If they were binding with the speed of the motor turning i'd expect 3 or 4 revolutions of the upperstructure and the swing motor would be really hot. I'd start with the basics, check swing bearing/ bearing grease, check inside the grease tub and make sure the ring gear and pinions well lubed. Check the swing device gear oil for contamination/debri. Check the brake line going to the motor, should be around 40 bar swing left or right, same pulling the arm in and the same when swinging then letting the lever go to decelerate.
If the servo filter is due a change ,Iwould start there . The brake may be draging constant due to low servo pressure but can sounds louder as it slows