Results 1 to 9 of 9
  1. #1
    Milacron's Avatar
    Milacron is offline Diamond
    Join Date
    Dec 2000
    Location
    Coastal Dogpatch, SC, USA
    Posts
    45,400

    Default How to clean motor armature ?

    DC perm magnet (German CNC axis) motor that has internal short. Slight possilbity if cleaned and baked to remove all oil traces it might be ok... so how do professional facilities do this..ultrasonic or ?

  2. #2
    Mike K is offline Cast Iron
    Join Date
    Nov 2002
    Location
    Southern Indiana
    Posts
    465

    Default

    Milacron,

    I have a '91 HAAS that alarmed out 3 or 4 years ago because of brush dust buildup. The dealer said the only solution was to replace the motor. I had nothing to lose so I took the motor apart and put the whole armature in the ultrasonic for about 10 minutes. I put in new brushes and it's been working fine ever since.

    YRMV though.

  3. #3
    bdx
    bdx is offline Cast Iron
    Join Date
    Apr 2007
    Location
    N. Ireland
    Posts
    260

    Default

    Wash and stove.
    Wash with a solvent (gen clean) or hot soapy water forced into windings. Place in stove at about 110 deg C with a temp probe on the armature (Don't over cook it) for several hours. Remove and megger, plot result over time on a graph, repeat until reading stabilises. As armature cools, insulation reading may fall.

    Ultrasonic tank would be quicker? (don't have the luxury)

    If and when readings improve to a satisfactory value, re insulate.

    Mark

  4. #4
    Forrest Addy is offline Diamond
    Join Date
    Dec 2000
    Location
    Bremerton WA USA
    Posts
    9,299

    Default

    Only thing I'd add would be clean out the armature slots if they need it. The comm may need to be re-cut and undercut but all that is obvious.

    Trink is to get the armature out without buggering up the magnets.

  5. #5
    9100's Avatar
    9100 is offline Diamond
    Join Date
    Nov 2004
    Location
    Webster Groves, MO
    Posts
    4,194

    Default

    I used to reclaim locomotive fuel pump armatures on a regular basis. The advice so far has been good. Avoid any sort of caustic or otherwise harsh solvent. Soapy water and a good rinse is fine. I then would heat them up to just over boiling, 110C is fine, then put them in a vacuum chamber overnight. That almost always brought the megger reading up to infinity. Then I would vacuum impregnate them with transformer varnish in the vacuum chamber, pumping it down, then letting varnish in to cover the armature. The vacuum in crevices pulls varnish into them when you let atmospheric pressure back in, really sealing them. For some jobs, people pressurize the chamber, but that mostly just speeds things up. Then they got a couple of hours bake at 265F to cure the varnish. They almost always needed the commutator turned and the slots undercut, so getting varnish on it didn't matter. About the only failures we had were when someone used a strong caustic solution. Those usually had to be rewound. Of course, if the breakdown has carbonized a track, none of this will help.

    If you want, I can do yours, but there probably is a local motor shop that would save shipping. Don't settle for just dunking it in varnish, which is what some of them do. They may give you a song and dance about how it doesn't matter. Don't listen. Insist on vacuum impregnation.

    Bill

  6. #6
    Milacron's Avatar
    Milacron is offline Diamond
    Join Date
    Dec 2000
    Location
    Coastal Dogpatch, SC, USA
    Posts
    45,400

    Default

    Quote Originally Posted by 9100 View Post
    If you want, I can do yours, but there probably is a local motor shop that would save shipping. Don't settle for just dunking it in varnish, which is what some of them do. They may give you a song and dance about how it doesn't matter. Don't listen. Insist on vacuum impregnation.

    Bill
    I can't find anyone that I can trust to do what you propose (which sounds the most logical cure I've heard yet) so I actually would be interested in sending you the rotor if you are still game. What say ye ?

    procyon@charter.net

    If your cure works, I will have numerous "bow down" emoticons thrown your way and you will be hailed here on PM as the Armature King, posthaste, forthwith and forthwright !

  7. #7
    chuckey is offline Stainless
    Join Date
    Jul 2005
    Location
    Wensleydale, UK
    Posts
    1,136

    Default

    On inspection, the state of the armature looks "as new", except for dirt, doesn't it? If one winding has been overheated (darker brown), but not black, I would try and figure out what could be the most likely cause. As far as I know windings are wound on a former, extricated like a hank of wool, they are then taped to hold the turns in place then "crushed" into a pair of straight sides with rounded ends. The straight sides are put in the pre-lined (with insulation) slots with a strip of insulation pushed in to hold them in the slot. The rounded ended are then dressed neatly (with a hammer?). So it is most likely that any damage is in the rounded ends if it were there to start of with but its the slots where the windings will over heat. The other factor is if the leadout wires were stretched as tight as a bowstring before being crimped at the communtator segements, the tension (+vibration) could have caused the leadout to rub through another turns insulation.
    We had a range of motors that failed after a couple of years age in service because the windings slowly moved with heat cycling and stressed an added component (temperature detector).
    If I could not figure out any potential fault with a strong eyeglass and fix it. I would just go for ultrasonic cleaning if that clears the fault, then a bakeout and vacuum impregnation, to try and hold the wires in this position while its spinning at 10k RPM.
    I am thinking if over heating caused the wires to touch each other, what would happen if you put it in a deep freeze for a couple of hours. In my simple mind, if the expansion due to heat pushed the wires together, then contraction due to cold. . .?
    Frank

  8. #8
    jim rozen is offline Diamond
    Join Date
    Feb 2004
    Location
    peekskill, NY
    Posts
    21,459

    Default

    Ah, you do have a megger, right?

    Jim

  9. #9
    Mike C. is offline Diamond
    Join Date
    Nov 2004
    Location
    Birmingham, AL
    Posts
    10,848

    Default

    9100 has got it right.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •