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hydraulic circuit problem? breaker tripping while pressure builds.

fignoggle

Plastic
Joined
May 16, 2010
Location
CA
hi all-

this is a general type of question re: hydraulic circuits for cnc lathes with hydraulic chucks.

on our recently acquired no-brand gang style cnc lathe, upon pressing the "machine ready" button (it's a yasnac lx3 control), the hydraulic motor starts pumping and after a minute or so, it trips the breaker in the electrical box in the back of the machine. while the motor's pumping, we can use the hydraulic chuck (on/off).

the gauge connected to the solenoid doesn't move (can't imagine the gauge is bad) - so does this mean that the solenoid isn't turning on or what? we've never dealt with hydraulics so this is new to us.

are there basic troubleshooting steps to take? thanks! :crazy:
 
What voltage is the machine currently (pun?) hooked to?

And what did it come from?

(208 / 240 ???)

My need next size up heaters.






OK - machine is prolly newer than that.

Maybe just turn up the overload on the motor starter if there is headroom. Otherwise may hafta buy next size up overload.





Sounds like the guage is bad to me. ???



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Think Snow Eh!
Ox
 
Try changing the rotation by changing the incoming phases.The traditional test to check phasing on a cnc is to try either coolant or hydraulics.You need to see pressure on the gauge to ensure the motor isn`t overloaded.The easy way is a tong test.
 
Is the oil tank full?? dont laugh, I've seen people expect oil to be there by magic.

and wy the no name?... the builder not prowd enough to put their name on it?

"on our recently acquired no-brand gang style cnc lathe"
 
Hyd Circuit problem, breaker tripping

I would for sure check the voltage coming in as to what the last user was wired to.
Remove the gauge and "bump" the hyd motor to see if you have an "air lock" in the line.
I thought I had a hydraulic motor wired wrong (3 phase), reversed two wires and I heard bubbling in the hyd tank. Turn on the pump and listen in the tank for bubbling.
Another check might be look at the hydraulic motor coupling, and (1) determine direction of rotation and (2) turn the pump on and then watch the coupling. When it turns off, dose it back up rebound. That would indicate maybe the hydraulic lines are reversed somewhere..
However, if you can use the chuck, sounds electrical to me.
Maybe an AMP meter is in order.
Regards Walt.....
 
Reverse rotation?

He said that he could cycle the chuck while the pump was running eh?


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Think Snow Eh!
Ox
 
How much pressure did he have,eh? :D

Mark.

the gauge connected to the solenoid is dead, so we swapped that one for the gauge connected to the pump. we showed 25 psi at the solenoid, turned it down to zero and we got a hydraulic alarm (no surprise). while the pump was stilling pumping away, we dialed the solenoid back up to 25 psi, the alarm on the yasnac lx3 went away. no surprise here as well... i forgot what it read at the pump.

about a minute later, "click", the breaker tripped again.

there's a pressure switch connected to the manifold as well and it was set to lowest setting on the range (something like 100 psi). is this pressure switch a safety switch?

although the motor seems to be somewhat noisy, it appears to be pumping properly. i presume that if i had the motor wired in reverse, the motor pressure gauge wouldn't move?
 
You sure it's PSI and not BAR or some metric thing?


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Think Snow Eh!
Ox


oops! how embarassing! :o

yup, it's 500 psi at the pump and 350 psi at the solenoid.

here are some pics of the assembly and a wav file of the noise (i can't tell if that sound is good or bad).

come to think of it, the pressure switch (the light blue unit mounted to the solenoid) is set the min at 138 psi.

figNoggle_CKHydPump1.jpg


figNoggle_CKHydPump2.jpg


s wav sound file of the pump
 
The pressures look ok.Machine tools rarely use high hydraulic pressures.The pressure switch is used to signal the cnc control that the pressure has reached a set minimum.If the control doesn`t see the signal it will fault out on low pressure.
It may be a faulty contactor for the pump motor.If you have a tong tester check each phase after the contactor to see what current it`s pulling.You can also put the power off,disconnect the outgoing wires from the contactor,push it in by hand and measure the resistance across each set of contacts with an ohmeter.An old contactor can have a high resistance on one phase which leads to higher current on the other two,which makes the overload trip.
Mark.
 
Hows about you check the label on the motor and see what Amps it is rated for at what volts at 60Hz. (There may be 60hz and 50hz ratings posted - we are at 60hz here.)


Then check to see what the overload is set for.


What volts doo you have it hooked to currently?



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Think Snow Eh!
Ox
 
The pressures look ok.Machine tools rarely use high hydraulic pressures.The pressure switch is used to signal the cnc control that the pressure has reached a set minimum.If the control doesn`t see the signal it will fault out on low pressure.
It may be a faulty contactor for the pump motor.If you have a tong tester check each phase after the contactor to see what current it`s pulling.You can also put the power off,disconnect the outgoing wires from the contactor,push it in by hand and measure the resistance across each set of contacts with an ohmeter.An old contactor can have a high resistance on one phase which leads to higher current on the other two,which makes the overload trip.
Mark.



thanks mark and all-

i wanted to make sure the motor wasn't being overloaded on the hydraulic side, so the pump was disconnected from the motor so that the motor had nothing connected to it.

powered up the machine, started the motor and again, breaker trips. here's a picture of the contactor in question.

figNoggle_CKContactor.jpg


there's no tong tester here so, with power off, we checked resistance between 1 and 2, 3 and 4, 5 and 6. each one when the contactor was pushed down, we get 0.3 ohms.

there's that little dial on the bottom right, is that useful to adjust? (what is it?)

also, forgot to mention that our shop has 250v at the wall, and this machine is supposed to run on 220v. there are no taps inside the machine, so i'm guessing it handles the 30+V difference...

i'm going to swap one of the other contactors and see if that does anything... :confused:
 
And you are having to re-set the Overload on this manually right?


If not - and I hafta ask - (You are just finishing machine install if I remember right?) doo you have air hooked up to the machine? This may sound "out there" as you apparently are gitting a hydro alarm, but if by chance you are not re-setting the O/L, then something else could be taking down the machine - resulting in a "Low Hydro" message. (Mine doo this when put in E-stop as example)


Pressure switch is set to 138#?

I kant imagine a hydro switch set that low. ??? Mine run at 1000# "system pressure" and then regulated down from there.


Does the pump git loud jist before it drops out? Could be really low on fluid (possibly drained or at least lowered for shipping sometimes) and sucking some air - resulting in lower pressure - and the switch to drop out. ???


-------------------

Think Snow Eh!
Ox
 
Last edited:
And you are having to re-set the Overload on this manually right?


If not - and I hafta ask - (You are just finishing machine install if I remember right?) doo you have air hooked up to the machine? This may sound "out there" as you apparently are gitting a hydro alarm, but if by chance you are not re-setting the O/L, then something else could be taking down the machine - resulting in a "Low Hydro" message. (Mine doo this when put in E-stop as example)


Pressure switch is set to 138#?

I kant imagine a hydro switch set that low. ??? Mine run at 1000# "system pressure" and then regulated down from there.


Does the pump git loud jist before it drops out? Could be really low on fluid (possibly drained or at least lowered for shipping sometimes) and sucking some air - resulting in lower pressure - and the switch to drop out. ???


-------------------

Think Snow Eh!
Ox


no changes in sound before the contactor trips. we're going to swap the one for the coolant pump with the hydraulic one and see if that changes anything.

as of now, the machine is nearly naked with most of its sheet metal off while being cleaned up. years of chips, oil and such have found their way into the machine's nooks and crannies.

over the weekend we'll put things back together and get the contactor tested. since the motor ran at no load and still tripped the contactor, we're thinking that's the culprit (hopefully it's not the motor!).
 
Measure voltage and currrent

The quickest way to identify the root cause of the problem is to measure the voltage and current on all 3 legs. Verify the current measured with the rating label on the motor.

If the voltage and current is within spec. suspect that the thermal overload is bad. Theses devices tend to get resistive if they have tripped a few times which will cause a continuous failure cycle.

If the current is high and the voltage is in spec. suspect your motor has either a shorted winding or possibly a resistive short to ground (would faile a Megohm test).

The meter below is short money to quickly ID the problem.

http://www.sears.com/shc/s/p_10153_...Testers&psid=FROOGLE01&sid=IDx20070921x00003a
 
years of chips, oil and such have found their way into the machine's nooks and crannies.
I had a listen to your Audio on Saturday. Hard to say, but it sounded really “tinny” to me. While your pulling things apart, take the 3 screws off the fan cover and make sure there’s nothing rubbing on the fan.


And you are having to re-set the Overload on this manually right?
You really need to confirm what Ox is asking you. Do you have to push that little grey tab / button, under that dial you were asking about. That’s the reset on the thermal overload. It can only be manually reset, by pushing it back in. There’s a difference between that tripping on high current, and the contactor being turned off for another reason.


Regards Phil.
 
Did anyone suggest taking the cover off of the motor, and verifying that the motoro is in fact wired for 240 volts, and not 480 volts?
Having the voltage wiring wrong might not make it happy.

Otherwise, time to measure the actual amps draw here.
 
I had a listen to your Audio on Saturday. Hard to say, but it sounded really “tinny” to me. While your pulling things apart, take the 3 screws off the fan cover and make sure there’s nothing rubbing on the fan.

You really need to confirm what Ox is asking you. Do you have to push that little grey tab / button, under that dial you were asking about. That’s the reset on the thermal overload. It can only be manually reset, by pushing it back in. There’s a difference between that tripping on high current, and the contactor being turned off for another reason.

Regards Phil.

thanks phil. yes, we have to push in the gray tab each time it trips. it also looks like that contactor had been split apart in the past. will still check current draw after buying a tong tester and post results tomorrow.

what does the dial do?
 
The dial sets the current that the overload will trip at.It should not be set higher than the full load current of the motor.Should be on motor data plate,sometimes shown as F.L. or F. Load amps.

Mark.
 








 
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