Losing hydraulic chuck pressure

Mazak QTN100 consistently losing chuck pressure while engaged. Starts at 350 and will slide under 150 within 20 minutes. When its not engaged it pops back to the set 350. Could this be an actuator issue? Any thoughts?

what pressure gauge are you talking about.. one for CHUCK ? what about pressure indicator on systems hydraulic pump???
do you have this safety valve? that can be leaking OR main hydraulic valve isnt holding pressure, lets say solid state relay failing after a period of time. Open you hydraulic drawing in your parts manual and have a look how oil is going towards CHUCK ACTUATOR

I would guess internal leakage in the actuator.

benganboll said:

I would guess internal leakage in the actuator.

Click to expand...

it will be a simple piston configuration. if it leaks unclamp, them it will leak CLAMP. too easy forus

noname777 said:

if it leaks unclamp, them it will leak CLAMP. too easy forus

Click to expand...

I will not agree.
My excavator had no force in one direction but full force in the other direction on one actuator.
It was the sealing around the piston that was broken and fliped out of position in one direction and sliped back in in the other direction.

It is easy to test, disconnect actuator pipes/hoses and plug them, if you then have full pressure when you clamp unclamp the problem is at the actuator.

benganboll said:

I will not agree.
My excavator had no force in one direction but full force in the other direction on one actuator.
It was the sealing around the piston that was broken and fliped out of position in one direction and sliped back in in the other direction.

It is easy to test, disconnect actuator pipes/hoses and plug them, if you then have full pressure when you clamp unclamp the problem is at the actuator.

Click to expand...

the guy says:

-When its not engaged it pops back to the set 350

I would assume actuator is OK, as it should be simple hydraulic o-ring,I might be wrong here.



the other thing is that configuration has two check valves (if pump stops they will still hold the job), and they can be lifted with pilot pressure. What if one cannot be lifted properly with pilot pressure? One for UNCLAMP. When you clamp, oil goes into right side of cylinder and cannot escape from left side but....through , pressure safety relief valve (on the top) it will drain itself into right side, allowing clamping.

By now chuck is closed. All is ok. After a certain period of time, internal leak will push oil into left part of cylinder ( on attached picture) where bigger area of piston will push it into left( unclamping) .

That is how theoretically the problem can be explained. But what is inside CYLINDER ? I dont have this drawing at this moment.