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Coolant Pump Puzzle

Mr.Chipeater

Aluminum
Joined
Apr 20, 2021
I'm hoping someone has run into a similar problem once before and can help me solve a problem we are having with the coolant pumps on our Mikron.

When the TSC (through spindle coolant) pump motor is turned on, it spins for a fraction of a second then the machine E-stops. All other coolant pumps (flood and wash down) work fine. There are no other alarms on the machine other than "safety circuit emergency stop." Here's what we've tried so far:

Swap TSC motor for another similar size 3 phase motor - same result (E-stop)
Connect flood coolant motor to TSC circuit - circuit works fine.
Connect TSC motor to flood coolant circuit - Trips relay breaker
Bench test TSC motor- spins without issue.

Given the TSC motor spins just fine when connected to a different power source and the problem follows the TSC motor, I'm leaning towards 2 possibilities: Either its drawing too much current when first starting up or the draw is causing a momentary drop in voltage causing the machine to freak out by E-stoping. Although I'm not satisfied with either guess because if its current, why is the breaker only tripping when connected to the flood circuit (smaller breaker) and if its voltage, wouldn't there be other alarms on the control?

Has anyone else had a similiar experience? Any suggestions on things to try?
 
Pump may be deadheading. Stuck check or inner hose liner collapse can cause it. Unhook the output hose and plumb in a hose and run it to the inside of the cabinet, which will take the check and factory feed hose out of the equation..
 
I had an 1k PSI MP systems relay trip in my new mill.
The apps engineer said that the relays have an adjustment dial on them that has something to do with when they trip.

Do your relays have anything like that on them?
 
If you deadhead a conventional centrifugal pump, the pump will be at it's lowest power draw point over the range of it's operation. This link has a quick discussion of the pump curves. It's aimed at a bigger pump, but the principles are the same:


Could it be that the machine has some sort of GFCI/RCD protection that is absent from the bench test?
 
I should have clarified originally, the motor shaft is disconnected from the pump so there's 0 load during these tests. Right now its just a relay to an AC motor.

Also, I don't see any way to adjust the relay.
 
Run the pump motor and check current draw with a clamp on amp meter. Then check the heaters in the contactor in your machine
and see how they compare. The heaters / overload setting on the contactor needs to be a bit higher than the no load current draw of the motor. thats a start anyway. Your TSC motor probably draws more current that your flood motor (check the motor nameplates to see) thats why the flood pump contactor tripped- most likely not a good test.
 
Run the pump motor and check current draw with a clamp on amp meter. Then check the heaters in the contactor in your machine
and see how they compare. The heaters / overload setting on the contactor needs to be a bit higher than the no load current draw of the motor. thats a start anyway. Your TSC motor probably draws more current that your flood motor (check the motor nameplates to see) thats why the flood pump contactor tripped- most likely not a good test.
I agree. The flood motor certainly draws less current. However the TSC motor isn't tripping the TSC contactor/breaker.

I spoke with a service tech familiar with these machines and he's stumped as well. He says that there's nothing on this circuit other than the incoming voltage, breaker, relay, pump, and 24V signal for the M code. Each component when tested individually works just fine but when all together, the machine E-stops.
 
I’m leading towards an earth leakage detection circuit somewhere, although it doesn’t sound like you need to physically reset anything in the cabinet to recover the e-stop state. Is anything physically tripping with the tsc pump hooked up like normal? What do you need to do to recover it after e-stopped caused by tsc?
 
I’m leading towards an earth leakage detection circuit somewhere, although it doesn’t sound like you need to physically reset anything in the cabinet to recover the e-stop state. Is anything physically tripping with the tsc pump hooked up like normal? What do you need to do to recover it after e-stopped caused by tsc?
Nothing needs to be physically reset. Its a Heidenhein control and the alarm is a "safety circuit emergency stop" which is the generic e-stop alarm. If I bring up more info on the alarm it just states to make sure all estop switches are released and reset the machine.
 
and then a simple reset does the trick without fussing with anything else? Problem repeats when TSC is called again? Do you have circuit diagrams on this system?
 
I'm hoping someone has run into a similar problem once before and can help me solve a problem we are having with the coolant pumps on our Mikron.

When the TSC (through spindle coolant) pump motor is turned on, it spins for a fraction of a second then the machine E-stops. All other coolant pumps (flood and wash down) work fine. There are no other alarms on the machine other than "safety circuit emergency stop." Here's what we've tried so far:

Swap TSC motor for another similar size 3 phase motor - same result (E-stop)
Connect flood coolant motor to TSC circuit - circuit works fine.
Connect TSC motor to flood coolant circuit - Trips relay breaker
Bench test TSC motor- spins without issue.

Given the TSC motor spins just fine when connected to a different power source and the problem follows the TSC motor, I'm leaning towards 2 possibilities: Either its drawing too much current when first starting up or the draw is causing a momentary drop in voltage causing the machine to freak out by E-stoping. Although I'm not satisfied with either guess because if its current, why is the breaker only tripping when connected to the flood circuit (smaller breaker) and if its voltage, wouldn't there be other alarms on the control?

Has anyone else had a similiar experience? Any suggestions on things to try?

If your at a dead end, id probably just add my own contactor/overload and use the weak TSC output power to control the new contactor.
 
Phase rotation?
Swapped the TSC motor with the regular flood coolant motor and everything works.

Service tech I spoke to is convinced the TSC motor is bad and needs to be replaced but I'm not convinced because I get equal resistance measurements across all 3 windings and it spins fine on bench power.
 








 
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