Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: jonny quest on September 11, 2012, 10:26:15 PM
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i goofed... burned a z axis servo. moved machine and left gibs tight from when i lifted it, and started to re-tram Z from move. Axis moved just fine... but little servo got real hot until I realised what I did.
it's a industrial hobbies (RF45 style) mill. It has Gecko 320 drivers,Mach3, and servos.
After i realized what I did, shut off machine to allow servo to cool (it was still working fine) when I restarted it Z no longer worked.
I replaced servo, and new one faults when limit on Gecko is anywhere over 30%. Gain and damp have no effect at all.
I swapped driver from a working axis... and Z acts bad still.
I replaced encoder, still doesn't work. Did I burn out a prarallel cable or parallel card? I'm stumped and need to get this running again, any suggestions greatly appreciated!
Mach3's DRO does show movement, but no movement from servo
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When you say it faults could that just be indicating that your axis motor is too small and with you tightening the gibs it just cant keep on track without exceeding the following error? Have you tried with the motor disconnected from the axis? Is the axis properly lubed (screw and slides)
Hood
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Encoder is attached to ballscrew on this machine.
What I did do last night is take a battery charger... 12v 10a unplugged servo from system and hooked charger directly to servo... it barely lifted z, and easily dropped z. So servo is working correctly. It a brushed dc servo.
Problem is in machines power supply to z servo I think.
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Can you burn out a parallel port card or cable when a servo gets overheated?
What's the trick to measuring the parallel port to see if my z pins are sending out a signal?
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Would think that almost impossible as the servo is connected to the drive and then the drive to the breakout (if you have one) then finally the breakout to the port so it would be the breakout that damaged the port if it is but cant see how an overheat could cause that to happen.
You can test the Dir pin with a volt meter, if you connect the meter between the Dir pin and a Gnd pin you can jog one way and the other and you will see the voltage change, the Step pin can also be checked to a certain extent with a volt meter. You connect between the step pin and Gnd and depending on the active state you will either see maybe a few hundred mV register when you jog or see the 5v drop a few hundred mV. The only real way to check though is with a scope.
Have you tried using different pins on the breakout if you have any spare, even swapping around an axis on the breakout, say X for Z and vice versa.
Hood
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I did swap drives all around. It is definitely just a z axis issue, with gecko driver known to be good, and servo known to be good.
When I check voltage on just the z axis servo... at rest I get same power as known good axis. As soon as I jog the bad axis voltage drops to zero for both directions.
The z definitely isn't getting power when jogged
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I was really meaning to try different pins on the BOB, its not uncommon for CNC4PC bobs to blow their optos, dont know if thats what make you have but if it is then it could well be the problem.
Hood
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I'm a doofus with the electrical stuff. This was a turnkey mill, I didnt build it.
coming into control cabinet, I switched parallel cable wires 4/5 (which is the Y axis) with 6/7 (which is troublesome Z axis). Y still works fine, but Z still does the same thing.
So that will rule out the parallel cables, computer, and parallel port.... I think?
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I'm a doofus with the electrical stuff. This was a turnkey mill, I didnt build it.
coming into control cabinet, I switched parallel cable wires 4/5 (which is the Y axis) with 6/7 (which is troublesome Z axis). Y still works fine, but Z still does the same thing.
So that will rule out the parallel cables, computer, and parallel port.... I think?
Pretty good troubleshooting for a doofous. Can you measure volts between terminals coming from the bob Z axis when you do a jog move? You can compare to the working axis values. Maybe you did this? Your getting warm pun intended. Not sure if you covered the bob yet in your process of elimination. Your running out of things to check!
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I don't know what a "bob" is?
Apparently there is no breakout board.... so I'm told. I'll snap a picture tomorrow and post cabinet electronics.
Couple more tests I did... verified the 4 encoder wires aren't shorted.
I then disconnect my two Z axis servo wires from Z gecko... piggybacked them to my working Y... and jogged Y. Z moved fine. That verified Z servo Is working correctly (it used Y's power and encoder)
I think there is only two possibilities left, bad encoder... or power going to gecko.
I did check voltage variance on working drives to bad drives.. they do seem similar.
Could a bad encoder head cause gecko to not allow me to turn up limit past 30% without faulting?
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It could be the encoder but I am thinking the Z drive or upstream of it. You overdrew current which is felt by the motor/drive evidenced by it getting hot. The motor survived but the drive took the brunt of the over current. Can you stick one of the other drives in the Z position? You have essentially done that when you piggy backed the Y drive to Z motor but that does not eliminate what's up-stream of the Z drive just yet. As you say it's not a Break Out board per say but whatever it is, it gives the Gecko its move instructions. The encoder is essentially feedback so it might be the problem but intuitively the drive or its control seems more likely to have failed. How tough is to get a spare encoder? Any existing parts servcie on this machine? Pictures are always good. You almost got this.
Like this one: http://cnccookbook.com/CCMillCNCConversionHome.html
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(http://img.photobucket.com/albums/v250/williamsmotowerx/20120914_120901.jpg?t=1347642917)
(http://img.photobucket.com/albums/v250/williamsmotowerx/20120914_120913.jpg?t=1347642947)
I did take working Gecko drive from Y, and put it on the Z. Z still didn't work. I also took Z drive and verified it worked on the Y. If that maks sense... drive is working correctly.
As you can see in first pic, my Z drive is close to where parallel wires come into cabinet. They seem to go directly to drive.
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Where does your parallel port connect to? is it just bare wires taken to each drive/component or is there a plug on the end that goes to a board and then wires from that?
Hood
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thats what i was hoping you could tell me from bigger pic. it seems like they go direcly to drive
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Can you not see the cable that comes from the computer? Trace it to the cabinenet and see if it goes to a board or if its just wires that come out the end of it that go to the drives etc.
In the pic I cant really tell where the cables go, they seem to go to a breakout board (BOB) of sorts, I think its the green and yellow wires? If it is then you could swap the Z for another axis on that BOB and see if the problem follows the wring change or stays with the axis,
Hood
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On the zoomed in picture the blue terminal strip to the right with all the yellow & green wires are hooked to step and direction on each drive. If you look closely it looks like where the computer ties in from the port. You see a dark connector betwen the terminal strips below. Compare signals coming from Z(terms 6 &7) and Y (4,5) ect. I bet something is corrupt off that so called break out.
I am a bit puzzled what the 2 boards in the middle do, 1 has a bunch of black capacitors (left) and the other looks like some sort of logic card(right, green board blue relays and chips). Maybe these are amplifiers...to handle feed back?? They tie together. Keep going!
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Think the middle cards may well be spindle control boards.
Hood
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(http://img.photobucket.com/albums/v250/williamsmotowerx/20120914_145855.jpg?t=1347652787)
Here's a better picture.
Hood id correct the middle ones a re spindle control.
The thing is, the Gecko faults...WITH NO MOVEMENT AT ALL ABOVE ABOUT 30% ON LIMIT. Doesn't that rule out the bob pins?
The encoder is constantly giving feedback to servo at all times, correct?
I'm almost sure the reason Z isn't moving up and down is because I can't turn limit up enough (without a stationary fault) on Gecko drive so it has enough voltage to move servo.
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Never used Geckos or DC servos so cant really help on them, only used AC servos.
What is the black wire hanging loose?
BTW thatBOB is just a basic connection board by the looks of it so unlikely there is a problem with it.
Hood
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Those are encoder wires. Had them off testing them.
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Have you uncoupled the motor and tested it?
You have confirmed its not the computer or drive or anything up to there I think by swapping axis wires around and swapping drives. Think you said you had swapped encoders, so really that only leaves the motor.
Hood
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Reading thru this thread I understand JQ has verified the drives and the motor are all good but the Z position where any particular drive is connected still does not work. So what's left are the inputs and outputs.
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Not sure if I am reading right but this would seem to suggest that the signals and wiring from Mach to drives are OK
I switched parallel cable wires 4/5 (which is the Y axis) with 6/7 (which is troublesome Z axis). Y still works fine, but Z still does the same thing.
The drive itself has been swapped and the problem persisted so drives not to blame.
Encoder has been swapped so its not to blame.
Motor has been tested on a battery charger which seemed to show it worked but possibly not as it may be moving but just not well enough to keep up with the position and speed requirements when the drive is running it.
Hood
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Maybe the motor is damaged goods after all...is there 1 of the 5 motors than can be swapped out as a test? Everything the same just try a different motor. Working poor JQ to death here.
Robert
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Actually I do have a Hardinge dovetail conversion Servo 8000 lathe made in the 80's. She's a killer, works nice. I got a bunch of spare Pittman dc brushless motors with it. If these are anything like JQ's they are real simple, just 2 leads, a + & -. If there's damage, either a short to ground/casing or the resistance in the winding is low or high you should be able to measure it with a basic ohm meter and then compare to one of your other drive motors. If the motor overheated resulting in damage that could be pricey to replace as the Z is the big boy motor. I am not sure but repair of this type of motor may also be an option. Hope you can nail this down soon.
By monitoring and trying to participate in this thread and off course "Hood", I feel I learned allot and that more servo machines are in my future seeing how simple this is set up with the geckos.
Robert
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I had to walk away from it for a couple of days... I'll keep you guys posted.
What really frustrates me is the fact that I can describe the problem. Gecko won't accept enough limit to power servo to move Z. When I called gecko on this they didn't have an answer. Its not the gecko thats bad.. but something either up or downstream of the gecko.
I'd think that gecko would be able to tell me what this could be.
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You would think so but I have experienced that sometimes manufacturers don't like to offer too much outside of the component they sell. I guess that offering assiatance before or after a drive could be asking for trouble. In a sense it's not thier problem however I always hear good things of Gecko service. You eliminated the Z drive so that's good a good thing.
Give some diagnostic time to that motor. It was after all what got finger burning hot. When I checked the resistance across the leads of my motor it was around 4.5 ohm and niether was shortd to ground or motor casing. Simple check you can do to the motor which our old pro Hood was hinting at possibly being the damaged. If you were to connect leads from a working motor to that Z drive everything else the same it should prove to be the motor or something before.
RG
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It's a brand new motor. I knew old one was toast...I replaced it.
The problem is, I can't tune new one. The drive faults anytime I try and put more than about 30% power to it.
I've verified that the encoder works perfect, the drive works like it should, the new servo works like it should.
All other drives work like they should, and all 5 drives work off same power source.
I'm stumped!
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Hook the new motor up to the X drive, leaving Machs ports and pins as X, you will also have to connect Z encoder to X drive, see what happens.
Hood
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When you say applying 30% power, are you doing that on the drive dip switching for different amp ranges? Or are you trying different speed and acceleration settings in motor tuning or both? Sounds like a possible ground fault in the wiring in or out as you know the motor is good & drive is also good. I think checking wiring for ground faulting is not a bad idea at this point.
Since the basic breakout goes direct to Geckos maybe some damage happened back as far as the computer... pins 6/7? Roger stumped.
RG
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there's a limit pot that you turn on the Gecko drive. The Gecko isn't allowing me to turn up this pot switch enough to allow the servo to move the Z axis, the limit controls the voltage and or amps going to the servo. Even at rest if I turn the pot switch up past about 30% A fault light comes on the Gecko.
Not changing any settings in Mach at all.
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As far as I know... pins 6/7 control the Z... but they only send a 5v signal to the Gecko telling Gecko to apply power to servo.
If my servo won't even accept enough power at rest without faulting... it has nothing to do with the pins, computer, or Mach
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So your not moving yet and you are overdrawing current...so does that mean the holding torque is causing the fault? What does Gecko say instigates the fault light? Has to be a short or overdraw of current right? Check all your conductors to ground(a wire touching, bare?). Keep disconnecting conductors, power off course until fault goes away. If you lift 6 & 7 and the fault is the same then lift the wires going to the motor. Something you take away will stop the fault. Not sure if the lack of impedence will cause issues on the drive so be real careful about the conductors going to the motor. Don't want you to cause addtional damage.
RG
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Have you tried swapping the motor and encoder wires to the X axis drive whilst keeping the X axis ports and pins settings the same?
Hood
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Found this for the G320 surfing about;
FAULT INDICATOR:
The FAULT indicator is on while the drive is in power-on reset, the DISABLE input is held “low” or if the protection circuit is tripped due to a fault condition. All power MOSFETs are turned off and all internal counters are reset. The FAULT condition lasts for 3 seconds, and then self-resets to try again. If the protection circuit tripped it and the cause is not cleared, then it will immediately re-enter the FAULT state again and repeat the cycle.
There are two conditions that will trip the protection circuit. One condition is if a short-circuit occurs and current exceeds 20 amps.
The other condition is if the POSITION ERROR exceeds +/- 128 counts causing a break of the servo-lock. This condition can have several causes:
1) The loop settings are severely under-damped and the motor breaks out into oscillation.
2) Excessive motor load due to acceleration or workload.
3) The speed command in excess of what the motor can deliver.
4) The current LIMIT is set too low.
5) The power supply current is insufficient for the demand.
6) The motor is wired backwards, is broken or disconnected.
7) Encoder failure.
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Thank you! On phone 3 times with gecko... never once did they mention this.
I'll trouble shoot with this later tonight.
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Thank you! On phone 3 times with gecko... never once did they mention this.
I'll trouble shoot with this later tonight.
Have you not read the G320 manual?? It's all in there....
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i never got a manual, and i did look at gecko's site.... never found this info.
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i never got a manual, and i did look at gecko's site.... never found this info.
They're right there under "Support":
http://www.geckodrive.com/support/motor-control-manuals/dc-servo-drives/g320-rev-7.html
http://www.geckodrive.com/support/motor-control-manuals/dc-servo-drives/g320x-rev-10.html
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I did buy another servo, just to make sure the one I originally bought wasn't faulty. put it on and same thing.
So now I'm 99% sure it's the encoder. Yes, I did try 2 new encoders... one of them I stole from a working axis to verify. Still same problem.
Earlier I did a continuity test of the encoder wires, going from Gecko to the encoder... checked out good... that may not tell whole story,. with just continuity.
I just did a resistance test of the encoder wires... they all read the same.
Everything now does point to the encoder... but everything checks out fine.
Am I missing anything to check dealing with the encoder? Does Mach have anything to do with the encoder that I could be missing with the problem I'm having?
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I may have missed it so I will ask again, have you tried swapping the motor and encoder wires from the Z to the X drive and jogging the X axis?
Hood
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I would take Hood's advice. It's just one more step in the elimination process, it might lead you to solve the problem. He has an end game...your checking pins from X versus Z I take it.
Otherwise go back to the manual and the conditions for a fault:
Are you exceeding 20 amps, basic overcurrent? You'll need to measure somehow.
Is POSITION ERROR exceeding +/- 128 counts causing a break of the servo-lock. If so;
Conditions 1-3 are generally during a run so disregard for now
4) The current LIMIT is set too low. Not sure where your at with this?
5) The power supply current is insufficient for the demand. Don't think so your not moving yet but only drawing holding current
6) The motor is wired backwards, is broken or disconnected. It's new but could plus be reversed with minus on motor end?
7) Encoder failure. Most proable but you say you eliminated this with replacement known to be good?
The troubling part is that the fault should only come on for one of the above conditions so you have to figure out which one it is. If you lift the encoder wires power off does the fualt stay on?
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there's a limit pot that you turn on the Gecko drive. The Gecko isn't allowing me to turn up this pot switch enough to allow the servo to move the Z axis, the limit controls the voltage and or amps going to the servo. Even at rest if I turn the pot switch up past about 30% A fault light comes on the Gecko.
Not changing any settings in Mach at all.
Stupid question...but you first turn the unit on it's stable then you increase the current limit to ~ 30% and fault comes on right? What happens if you leave the pot lower than 30%? Will the motor turn in jog? According to the manual (item # 4) the fault should light with too low of a pot setting... not higher. It sounds like its working backwards. It's like you should have the pot set up higher before you power up. Reaching a bit but a thought to consider.
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If you do what hood asked you should find your answer. Pick a good axis then move the bad axis wiring and motor over to that drive. IF it runs ok then it is the drive if not it is either the servo/encoder or wiring.
Just a thought, (;-) TP
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FIXED!
I reversed polarity on servo motor... go figure
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Wrong polarity would normally make a DC servo run away but maybe the Geckos are smart enough to detect that and fault the drive?
Hood
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FIXED!
I reversed polarity on servo motor... go figure
Good job, I am happy for you. You did admit in the beginning that you were electrically challenged, lol.
The manual tells no lies brother:
6) The motor is wired backwards, is broken or disconnected. It's new but could plus be reversed with minus on motor end?
Rob
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And FYI.. the servo did have red and black leads coming off of it... I just assumed they were correct.
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What motor polarity is correct is determined by how the encoder is connected, as well as what rotation you consider to "correct". You cannot go purely by wire colors.
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On my old servo that I ruined... the red and black were correct.
Just hoping this thread could help someone else in the future.