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  #1  
Old Wed 07 November 2007, 04:04
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
Stepper motors giving trouble - Motors burnt while serving as ground for elec. fault

Gereald, I am having some problems with my Mechmate. The motors have all of a sudden stopped working. I am not very sure weather it is the Motors or something else which is faulty. I could start with the steppers. How should I check them.
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  #2  
Old Wed 07 November 2007, 04:40
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
If they all suddenly stopped together, then it is definitely:
- not the motors
- not the Geckodrives

Either:
- the Geckos are not getting the (big) power from your transformer supply system, or
- the gecko's are not getting (small) commands from the parallel port via the PMDX.
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  #3  
Old Wed 07 November 2007, 04:52
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
Not all only three stopped. One X axis motor One Y axis and one on the indexer.
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  #4  
Old Wed 07 November 2007, 04:58
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Can you tell us what is working? Is the E-stop switch working? Are the power supplies all generating power? Are the LEDs on all devices properly lit? Do the direction LEDs turn on/off when you use Mach 3 manually to move an axis forward and backward?

In order to help you find the problem, we will need to have as much detailed information as possible.

Edited:
Fabrica, we cross posted, but we still need more information.

Last edited by Richards; Wed 07 November 2007 at 05:02..
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  #5  
Old Wed 07 November 2007, 05:01
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
That is very unusual. Are your Geckos (can't remember your type) showing fault lights? (Motors very, very rarely go faulty - I have not heard of a faulty motor for years). Did you have lightning? Did some someone drive over some wires?

Did 3 out of 4 motors really stop at the same instant? Was the operator's face white with fear? All these things can give hints. . . . .

Otherwise, you have to start swapping motor cables from one gecko drive to another. First loosen all the springs and move the motors away from the racks - then you are free to try anything.

Hi Mike!

Daya, remember to let the capacitors discharge before you move motor wires around for testing.
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  #6  
Old Wed 07 November 2007, 05:06
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Hi Gerald. It's good to have good friends on line at 4:00 a.m.
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  #7  
Old Wed 07 November 2007, 05:14
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Yes, it sure is. Still that early? It's lunch time here, and Daya probably wants to go home for supper.
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  #8  
Old Wed 07 November 2007, 05:15
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Funny, I was thinking the same thing when I saw Gerald online here at 12:05 am EST and again at 6:15am. Now that I think of it, I am working to much
Sean
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  #9  
Old Wed 07 November 2007, 05:18
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
For reference, this is Daya's (Fabrica's) board in Sri Lanka:



Sean, I have had a bad night with flu, so you saw me at some very strange hours.
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  #10  
Old Wed 07 November 2007, 05:22
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Ditto - I have been up all night with my kids who are sick....now daddy's feeling a little under weather
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  #11  
Old Wed 07 November 2007, 05:22
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
One thing that we found out was that we had live current on the earth line. We found this the hard way. One guy touched the table and got a hair raising shock.
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  #12  
Old Wed 07 November 2007, 05:24
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
He changed the transformer later. The Gecko's are G202's - red light is good, no light could mean anything.:



Daya, under that condition I would say to disconnect the geckos and PMDX from their power supplies, and then slowly and carefully check electrical circuits for mechanical damage.

See, I told you somebody had a white face!
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  #13  
Old Wed 07 November 2007, 05:35
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
Mike, Yes the E-stop is working. The transformer is showing 56 volts at the output. Direction LED's on the PMDX card is working ok when working with mach 3. when jogging. When we got to know that the three motors were not functioning we plugged in a new motor to all gecko's and they worked fine. This was yesterday morning. In the afternoon we fixed the old motor into the indexer gecko it was not working. Then we fixed the new motor on to the indexer gecko that too did not work. That is how things stand at the moment.

Today in the morning we did another trial. We removed al,l motors from the system and went on the jogging mode. All LED's in geckos were working fine. After this we connected the motors. Then the LED's in the Gecko's were not that brightly lit. The voltages on the output sgoing into the motor showed zero voltage when trying to jog and also when not running.
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  #14  
Old Wed 07 November 2007, 05:41
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
How is your controller connected to power? Do you use a two-prong reversible plug? Do you have the controller hard-wired to a breaker/fuse panel? Has anyone re-wired the connections between the controller box and main power?
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  #15  
Old Wed 07 November 2007, 05:46
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Daya, you are using a PMDX-135 and I wonder if that has gone faulty. But that should never cause live voltage on the frame. My guess is:

1. Some mechanical event happened - somebody hit a wire, then;
2. This caused a power spike in the control box, which;
3. Damaged components on the PMDX 135, which;
4. Allows the PMDX 135 only to give enough output for one motor, otherwise;
5. The PMDX 135 protects itself by not supplying more power.

I would test another DC power supply to the geckos . . . . .
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  #16  
Old Wed 07 November 2007, 05:50
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
We cross posted again. It's a good sign that the LED's on the Geckos are working without motors attached. Voltage between the G202 and the motor depends on which coil(s) is active at any particular time. Also, the voltage going to the motor is usually just a few volts. (Remember that the high voltage going to the G202 allows the G202 to work as a chopper. The high voltage never gets to the stepper motor.)

Check the connections between the motor and the G202. If there is a short, the G202 shuts itself off - and stays off until power is turned off.
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  #17  
Old Wed 07 November 2007, 05:59
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
I just checked the voltage between a G202 and its motor. In standby, there is less than one volt showing on the meter; however, the LED on the G202 is bright. Do you have 56V going into all of the G202s?

Here's some documentation from the G202 manual that describes what happens with a short circuit:

There is no protection against reversed power supply polarity, power supply voltages greater than 80VDC or exceeding the drive’s rated maximum temperature limit. It is also recommended not to connect or disconnect a motor while the G202 is powered up. The POWER indicator LED shows whether the drive has power applied. When a short-circuit condition is encountered, the G202 goes into protective shutdown by turning off the winding outputs. The G202 outputs stay in protective shutdown until the power supply is turned off and discharged, then turned on again. Should this happen, please check the motor wiring and the cable going to the motor for errors.
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  #18  
Old Wed 07 November 2007, 06:21
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
Guys Thanks for the trouble. I am going home now. It's almost 6.00 in the evening. I will get in touch with you guys early tomorrow morning.

Thanks again Gerald and mike for paying prompt attention to my matter.
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  #19  
Old Wed 07 November 2007, 21:14
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
I am back again at work. Can some guy help me out on this issue. Mike Are you awake.
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  #20  
Old Wed 07 November 2007, 21:34
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
Today morning we checked the coil resistances of the motor. The reading were 5 ohms on one coil and 1 ohm on the other coil. How are we to check weather the transformer is giving out enough power and not faulty.
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  #21  
Old Wed 07 November 2007, 21:40
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
One more thig that we found out today is that the motor shafts of the faulty motors cannot be turned with the hand. They are stuck.
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  #22  
Old Wed 07 November 2007, 23:20
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Daya, are the motors disconnected (lying on the workbench) when you measure the resistance, or try to turn the shafts?

Are your motors direct drive, or with gearboxes? If direct drive, I would be suspicious of sawdust in the front bearing. Read these two threads:
http://www.mechmate.com/forums/showthread.php?t=485
http://www.talkshopbot.com/forum/messages/26/7470.html
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  #23  
Old Wed 07 November 2007, 23:22
driller
Just call me:
 
Quote:
Originally Posted by Daya View Post
One more thig that we found out today is that the motor shafts of the faulty motors cannot be turned with the hand. They are stuck.
remove all the wires to one motor. make sure no two wires are touching.

then try to spin the motor.

connecting motor wires is like putting on a brake if not connected properly.

Very simple test.

Maybe remove one wire at a time and try to spin the motor after each wire.

also, look for tiny strands of wire that may be touching something they should not be.

Dave
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  #24  
Old Wed 07 November 2007, 23:24
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Found a pic of your motors:



Quote:
Originally Posted by Gerald_D View Post
Were your stepper motors open on the back? I strongly suggest you put a label/tape over those holes because the dust gets into the bearings. That hole traps dust and your operator will try to blow it out with compressed air - he will force the trapped dust into the bearing. (I had to replace bearings on my first stepper motors because of dust).
Quote:
Originally Posted by fabrica View Post
Yes, They were open in the back. I will seal it today.
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  #25  
Old Wed 07 November 2007, 23:33
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
I have removed all wires and tried to turn the motor. It is stuck.

Gerald, I do not see any mechanical damages.
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  #26  
Old Thu 08 November 2007, 01:09
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Are the wires not touching each other?

If you cannot turn the motors by hand (while the wires don't touch other) then the motor/gearbox is damaged or there is dirt stuck inside. Okay, they are not very easy to turn, but it should still be the same as your good motor.

I don't think you have any other option, but to open the worst motor.
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  #27  
Old Thu 08 November 2007, 02:31
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
The wires are not touching each other. So can I open the motors and see. But what would have caused it.
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  #28  
Old Thu 08 November 2007, 02:49
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Dust could have caused it. Did you read my experience at the ShopBot forum at the link I gave you above? Sounds like your situation.

Remember, the very standard advice is that you should never open a stepper motor . . . . . .
(They want you to throw them away and buy new ones)
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  #29  
Old Thu 08 November 2007, 04:11
Daya
Just call me: Fabrica
 
Kandy
Sri Lanka
But Gerald how come dust effected all three motors at the sam time.

Yesterday the motors were very difficult to turn. Today it has become easier adn when turning slips at one point. Can we supect the lead wires shortening inside the motor. What are the risks involved in dismantling the motor.
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  #30  
Old Thu 08 November 2007, 05:13
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Why would 3 sets of leadwires short out together? Why would dust do it to all together?

Whether it is dust or the lead wires shorting, it is still inside the motor and there is only one way to find out . . . . . look inside.

Read those threads and you hear about the risks.

What are your choices? Throw the motors away before you open them, or throw them away after you open them?
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