Removing brakes from Servos

[bvan1941]

Gents,
I think I have inadvertently pulled another subject ("a little Gem") off topic by asking about this brake removal process. If that's so I apologize. If anyone has experience on FANUC servo brake removals, I would appreciate any help provided. By the way a 7/32 Allen wrench just doesn't feel right when trying to remove the (4)  recessed Allen head screws from front of the unit. I am assuming the case has to be split to access the brake assembly. That assumption is from looking at a FANUC servo picture "Birdhouse" was showing on Servos from another Forum.
Bill

[wilfor03]

Gents,
I think I have inadvertently pulled another subject ("a little Gem") off topic by asking about this brake removal process. If that's so I apologize. If anyone has experience on FANUC servo brake removals, I would appreciate any help provided. By the way a 7/32 Allen wrench just doesn't feel right when trying to remove the (4)  recessed Allen head screws from front of the unit. I am assuming the case has to be split to access the brake assembly. That assumption is from looking at a FANUC servo picture "Birdhouse" was showing on Servos from another Forum.
Bill

Hey Bill, this is Bill

You might want to send a PM to "birdhouse" and "97fishmt" cuz they are very fluent in Fanuc servo motors. I think "birdhouse" even talked about pulling the brake off of one in "another" life.    (pun intended)  I'd love to help ya but can't on the Fanuc's . Good luck, Bill......

[bvan1941]

Bill,
Thanks, I should have thought of that----Duh! LOL (When in doubt ask the Teacher!)
Bill

[birdhouse]

bill-
yea, i've removed the brake from an A-06b xxxxxxxxx   unit. 

all allen head bolts are metric (japan).  and just so ya know it's pronounced "fanoook"

so ya, remove the end cap, and yank the encoder.  it's of no use to ya.  then, you remove the long bolts that hold the thing together, and begin prying/banging with chisels, bars ect. to break the case between the rear case and the laminations.  you want to "pull" the rear bearing from it's press yet keep the front bearing in its home.  problem is, the rear bearing has a spring washer in front of it, so you have to pry (easily) for about 3/8"  to collapse the spring washer, then pry (hard) to actually get the bearing to move within the press. 

the other beautiful part, it the coils are right behind where your sharp tools are being inserted, so be careful! 

you want to do it this way, because it will leave the mags right next to the coils.  i've never tried, but have read about how removing the magnet rotor from the coils/laminations, can greatly reduce the magnetic strenght of the rotor. 

one the back half of the case is off, you can remove the break pretty easily.  i also took the opertunity to solder/wire nut on #6 copper extensions to the three hot leads within the case.  i removed the funny prug, and ran the three wires out the hole. 



adam

[bvan1941]

Birdhouse,
Thanks for the help, you are correct the screws are 5mm . That pix you posted here is the one I've been studying (On another Forum). I'm not sure from your directions about which way (or why) to compress the spring  behind the "press fit plate" the tach was mounted on.   If I'm reading you correctly, I would first have to split the case apart (as per the picture) just ahead of the (4) prong receptacle right? Basically, reach the brake from splitting the case apart , not going in from the back end. 
I can understand about not removing armature and being careful of the coils when splitting the case apart!
Bill
 

[birdhouse]

bill, it's been a few years since i did that.  the more i think about it, the spring washer is on the other side of the bearing, so it should fall out when the case is split. 

yea, you can't get to the brake through the encoder cover (red usually)

if you go shaft to back of motor on the case, it should be smooth aluminum, then kinda ribbed (steel laminations)  <------CRACK between these--->, then back to smooth aluminum. 

what are the specs on your motor?  and if you don't mind asking, how much did it run ya?  oh and system voltage?

adam

[bvan1941]

Birdhouse,
Here are some specs on the servo: Fanuc MODEL 10F TYPE AO6B-0351-B731 PULSE CODER $40 (+)shipping= $69.28
                                                         148Vac ,21Amps, 3.1Kw
                                                          13.5 rpm/Volt  = Cut-in Approx. 202 rpm@15V (all calculated)

Is it a great buy, probably not but for the price- it's OK.  Already working on a much, much better motor with a lot more wattage between cut-in and 300 RPMs. Again, I've learned from both you and 97 fishmt. You both are generous, helping us guys trying to use Servos. I'll try and document my progress, observations and mistakes.
How has your servo been producing?
Thanks again,
Bill

[birdhouse]

bill-
that sounds like a decent one!  how'd you get rpm/v figures if the brake hasn't been removed yet?  or are you just guessing with math?  many of these don't follow exactly as the math would dictate. 

mine does pretty well.  it cuts in a little late, but that also keep it out of stall.  i have no anemometer, or Kwh recording stuff, so it's all guesstimates, but i think it starts charging at 12mph and i've seen over 700w out of it according to my ts-60 dumping while batteries where on float. 

one of these days i'll get some data logging stuff going on.  but i've gotta get the little 4' mill jerry sold me finished and up in the air first!

adam

[m12ax7]

Hello!

Many many times I've heard/read about the magnets losing their power if the rotors are removed.  I'll not say it isn't true, but I will say that in the numerous servos I've taken apart I haven't noticed this happening.

I've a Kollmorgen servo that I pulled out of a scrap barrel.  When I found it  the rotor was on the top of the junk, and the rest at the bottom.  I don't know how long the rotor was out of the stator,  but when I got it home I put it on a shelf, where it sat (in two pieces) for over a year before I got around to putting it back together.  Once assembled, shorting any one of the three legs, while spinning by hand would produce a sizable spark and make turning the shaft very difficult.  Short all three legs, and you can hardly turn the shaft.

Before I had ever heard "issues" with ruining the magnets I took apart several Allen Bradly servos and a few Emmerson's.   None of these servos were put back into their applications which they were intended for,  but each one would behave the same way as the Kollmorgen.

There  a small electric motor repair business just down the road and while there I asked one of their people about this issue and he "shrugged"  and said they're careful not to damage them when they remove them,  when asked how he said "we keep em wrapped with shop rags,  so they don't collect $#!+".  Now this guy didn't appear to be the sharpest tool in the drawer but he did seem to have some experience.

Again,  I'm not saying it isn't so,  just that I haven't seen proof.
I will mention,  that I would NEVER take apart a servo if it was expected to ever act like a SERVO motor again.   Most every servo I took apart I wrecked (not that I cared) the encoder/resolver in the process.

[bvan1941]

Birdhouse,
Yes I calculated cut-in and rpm/v speeds based on formulas. No actual hard data figures as yet! Being in a seasonal lower wind area,
Though this first Servo doesn't reflect ideal characteristics for me (price was right), I lean towards units with higher operating voltage, lower rpms and reasonable amperage. Thanks to you,12ax7 and 97fishmt, documenting your experience, advice and pointing me and others  to look at Manufacturers data sheets for additional information, really helps.
You guys have given us Noob's a good head start in picking better units to start with. We'll see if we can produce something like you all have made! What the ---- It's fun, personally satisfying and keeps friends and neighbors entertained !! Keeps me off the streets!

12ax7--I'm going to try REAL HARD to heed your advice and not remove the rotor from it's setting during disassembly.
I'm sure lots of us would like more follow up info on your past / current projects as well
Bill

[ghurd]

Many many times I've heard/read about the magnets losing their power if the rotors are removed.  I'll not say it isn't true, but I will say that in the numerous servos I've taken apart I haven't noticed this happening.

Again,  I'm not saying it isn't so,  just that I haven't seen proof.

Young Mr. Fungus experienced a 35% or 50% drop (can't recall which) from having the rotor out for just a couple minutes.
He had documented, in detail, all the operating stats before and after.

I have/had a small (100W~200W?) 100V 3000RPM one here that wouldn't make 3V AC at a few 100 RPM.
The sticker said "Do not remove this part" (paraphrased), but the screws were obviously removed at some point.
Gotta love ebay. 

I personally dinkered up a few, but did not save the before : after papers.

Mine are all small.  Can't recall what size Fungus' was, but guessing it was not 'big'.
Could be the smaller ones are more suseptable to the damage?

I don't leave the rotor out of an ECM without keepers on the magnets.
I even ruined a muffin fan PMA by leaving the rotor out too long.
G-

[birdhouse]

mike- thanks for the kind words.  i just keep after it and it gets better and better.  at the bottom i've put in a pic of my latest finished project. 

12ax-  i really have no idea if removing the rotor can cause damage, as i've never tried.  could very well be an old wives tail?  either way, if it's a motor i care about, i try to keep it fairly together just to stay on the safe side. 

bill-  i'd be curious to hear actual v/rpm versus mathed v/rpm.  and how much they vary!

adam

[bvan1941]

Adam,
Will do.
Right now I'm wrestling with some screws that are "tighter than a bulls a-- in fly time."  LOL
Bill

[birdhouse]

when i encounter tough screws, i go screw driver, to impact driver, to impact with break loose goo, to heat, to angle grinder.  the last always gets the bolt/screw out, though usually causes harm in the process.

good luck!

[m12ax7]

Many many times I've heard/read about the magnets losing their power if the rotors are removed.  I'll not say it isn't true, but I will say that in the numerous servos I've taken apart I haven't noticed this happening.

Again,  I'm not saying it isn't so,  just that I haven't seen proof.

Young Mr. Fungus experienced a 35% or 50% drop (can't recall which) from having the rotor out for just a couple minutes.
He had documented, in detail, all the operating stats before and after.

I have/had a small (100W~200W?) 100V 3000RPM one here that wouldn't make 3V AC at a few 100 RPM.
The sticker said "Do not remove this part" (paraphrased), but the screws were obviously removed at some point.
Gotta love ebay. 

I personally dinkered up a few, but did not save the before : after papers.

Mine are all small.  Can't recall what size Fungus' was, but guessing it was not 'big'.
Could be the smaller ones are more suseptable to the damage?

I don't leave the rotor out of an ECM without keepers on the magnets.
I even ruined a muffin fan PMA by leaving the rotor out too long.
G-

Like I said, not saying it isn't true!   30/50% decrease in what?  Magnetic force?  or power out put?

Don't know if this will work, but here's a pic of the rotor/magnets

http://www.otherpower.com/images/scimages/4822/Not_quiteperfect.jpg

and here is a end view of the rotor.  Blue tape is covering bearing and the black area is a voided/hollow.  Notice how thin the magnets are! 

http://www.otherpower.com/images/scimages/4822/Rotor_endview.jpg

I still have problems understanding WHY magnets that are on a metal surface/keeper would lose power?

With out having a method of measurement all I can say is that, when it was possible I turned the rotors by hand and observed the difference in force needed with and without the leads shorted and noticed no real difference before or after the rotor was removed/reinstalled.

If a servo motor needs it's bearing replaced,  how do they press the bearing off with the rotor still in the stator?

AGAIN,  I am not saying do as I did,  just saying what I observed in my little world.