[jjautomation]

Hi everyone.
I am working on a Beta 2/3000 motor. When we power ON the control as soon as motor comes in servo lock, if we try to rotate the motor shaft it rotates with a very little force and in control which is 21-T control Alarm 414-Axis detect alarm pops up.
I tried to tune the motor, increasing Prop gain etc but no luck.
Tried to drive same motor on another axis but problem remains same.
What I think is motor permanent magnet has demagnetized.
So what we can do now.
and how to check for magnetisation.
On googling I came across the topic back emf so how to check Back EMF and what voltage and current we should expect for a healthy motor.
Sent from my GT-I9100 using Tapatalk 2

[tc429]

if you have another good motor, just short the leads coming out of the motor and try to spin by hand- a demagged motor will turn a LOT easier... even a small servo will fight you if you try to rotate by hand with leads shorted... if you have a way to drive the motor shaft at low speed with a low speed air drill ~ something in the 300 rpm range (dont get electrocuted! it will generate hundreds of volts AC at full speed, and be sure its grounded!) you can test the volts and compare the two.

I assume resistance has already been checked on the power pins to look for a open winding...

your problem might well be inside the encoder- commutation is sent from there, a missing signal and she wont turn far.

[jjautomation]

Okay
Thanks for reply.
Motor winding is okay, insulation resistance is fine.
Motor encoder reading is okay, motor is rotating smoothly outside the machine but with low torque.

Sent from my GT-I9100 using Tapatalk 2

[cnzrepair]

The motor got too hot, lost most of its magnetism hence the low torque. Have it re-magnetized by a reputable motor shop.

[Al_The_Man]

The short test by tc429 will indicate if it has lost magnetism, How do you re-magnetize rare earth rotor magnets?
I would have expected the motor thermal sensor to have shut it down before overheat?
Al.

[cnzrepair]

Remember the drive signal that moves the motor is a very strong 3-phase AC, running the motor at elevated temperatures just below the thermal cutoff will demagnetize the rare-earth magnets faster. The thermal cutoff are usually there to protect the wiring and associated electronics inside the motor from overheating/melting which can potentially cause fire and not necessarily to protect the magnets.

There are companies that rebuild motors and part of their process is re-magnetizing the permanent rare-earth magnets. If you guys are interested, I can PM the company (located in West Chicago, IL) that my previous company recommends most of the time when customers call about their motor lacking torque.

[jjautomation]

Last day we replaced the motor with another motor.
Replacing motor was not new one but refurbished one.
Machine is Takisawa TC-10 CNC lathe.
Motor is for Servo controlled Turret
After replacing the motor we tried to run but motor runs okay for say 10-15 min that again 414 Detect alarm pops up.
After checking we found that motor is running okay CCW. But starts oscillating in CW.
Can this be because of Encoder or encoder feedback cable.
Checked the continuity of feedback cable which is okay.
Can't change the feedback cable for checking because another one not available and this cable is not matching with X and Z feedback cables.
Connector of encoder is D-Sub double row 15 pin.
When we rotate motor manually with hand with power leads disconnected motor shows position feedback on screen perfectly.
The servo is controlled with 21T system.
Can this be problem from motherboard or axis card in the main board?
Or the motor is having problem?
Or feedback cable can cause this type of problem.?

Sent from my GT-I9100 using Tapatalk 2

[cnzrepair]

The "new" motor runs OK CCW therefore the encoder and cabling are good, the same signals are used for CW operation. Next step is swap the servo drive with a known working one before you start poking at the axis control.

I don't know the state and history of your machine, etc. It's time you contact a field service in your area and have him troubleshoot it.

[tc429]

might sound silly, but i'd plug/unplug the little honda PCR20 plugs at the drive and axis card (dont bother if its the reliable old honda MR20 on the axis card) about 20 times...in the last few years we have had near constant servo issues with the PWM cables on everything we have with that POS honda plug... weve got some with the slightly bigger, infinitely easier to solder Honda MRs that are near 30 yrs old, never ever ever had one fail. one of our guys cut a pencil eraser like a 'flat', and uses that to clean the PCR plugs, but the sockets can have issues too...plugging them in/out repeatedly usually scrubs the contacts clean and the problems will go away...

Man I hated when Fanuc cheeped out with the plastic framed boards and PCR connectors... the old 6_B and 0_A boards were about bulletproof... seems as if 90% of our control issues on everything newer than 0-C is connection related...the 0-C woulda been great except for the constant ram parity/ trace failure repairs on memory cards from not enough copper, and cracked traces from bowing of the plastic framed /doublestacked connector axis cards- havent seen a non-bowed 0-C axis card in a control since our last new one came in 15-20 yrs ago... a month out of the box and they are looking like a bananna, expecially on 3 and 4 axis mills...bet the metal frame didnt cost but pennies more than that cheep yellow plastic


anyways back on topic- the ONLY fanuc AC motor Ive ever demagged happened in a instant (but DCs demagged all too often- from heat)...had a buzzy 6050 drive on a 20S motor, went a grabbed another drive off the shelf - with bigger problems- at ready the motor jumped hard, never moved again even with another drive... tried the shorting thing, no drag...pulled the thing apart, magnets were nearly dead- motor hadnt heated up, just took a big hit of current...wouldnt have thought it possible. the older motors were ceramic magnets, not rare earth, dunno about the latest... Ive played with the neodymium magnets, they go totally dead at over 300 degrees...think the ceramics could go a little hotter- from what I saw, the NeFB magnets die abruptly, like over a 20 degree span, dont recall, but think it was like from 330-350. thought it was kinda weird how a overheated then cooled NeFB magnet would barely even stick to a good one... almost diamagnetic...tried heating one and sticking to a stack of good ones before it cooled to see if it would pick up any strength again, nope... tinkering with magnets like a kid


I know a guy that used to recharge servo magnets- scary amounts of capacitor current needed to jolt them back...dunno the instant amps, but never saw so many big caps wired together... think he used a old motor stator rewound with a few turns of heavy gage wire if I remember right...didnt look like something I'd want to play with


wish I knew a way to remagnetize ac spindle mag sensors... every single one ive seen fail (hundreds?) had little or no magnetism left...think eddy currents in the motor kill them over the years...