Robodrill T14iB Z axis screw problem
Close
Login to Your Account
Likes Likes:  0
Results 1 to 5 of 5
  1. #1
    Join Date
    Jan 2011
    Location
    Estonia
    Posts
    761
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    207

    Default Robodrill T14iB Z axis screw problem

    Hello !

    Our robo has Z axis screw like on attached picture. It actually has 2 nuts bolted together, I dont know if its for improved rigidity (iB has faster rapids compared to iA)

    Problem - it makes rumbling noise and lately has started nonsmooth movement on Z axis (jumps about 0.1mm, checked with dial indicator). If I let the nut move down by weight, I can feel rumbling noise when holding screw.
    And, at the ends of screw it moves a bit harder. I think because the ends are not much used during normal machining and maybe they are worn out.

    My question - could there be an easy "mcgyver" fix to remove 0.1mm jumping and sticking ? I know that it needs replacement but I would like to use the old one until that (avoiding Z-sensitive work).

    Maybe the balls are not circulating ? I got no experience with that. On the screw I dont see much wear or "brinelling" but of course it could be thereimg_20210604_190044.jpg

  2. #2
    Join Date
    Oct 2007
    Country
    SPAIN
    Posts
    4,516
    Post Thanks / Like
    Likes (Given)
    448
    Likes (Received)
    263

    Default

    Is the problem definitely the screw?
    "Usually", rumbling axes are because of thrust bearings which make the "harsh" sound when rapid.

  3. #3
    Join Date
    Mar 2017
    Country
    LATVIA
    Posts
    841
    Post Thanks / Like
    Likes (Given)
    235
    Likes (Received)
    483

    Default

    if the nut threading along the screw feels rough, then I doubt it would be thrust bearings making the rumbling, but those could be shot as well if the rumbling went on for long enough, think about the increased dynamic load on them from all the vibration...

    could try reballing the nut, upon disassembly pay attention to size of each ball that comes out, they might be staggered in size, small/large/small/large and so on

    double nut setup, apart from increased load bearing, might be to eliminate any backlash, Fehlmann had something similar, but had a belleville washer in between the nuts to tension them and allow to compensate for uneven wear of the screw

  4. #4
    Join Date
    Jan 2011
    Location
    Estonia
    Posts
    761
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    207

    Default

    Quote Originally Posted by barbter View Post
    Is the problem definitely the screw?
    "Usually", rumbling axes are because of thrust bearings which make the "harsh" sound when rapid.
    I just checked thrust bearings - 2 oppositely placed ball bearings (J- shaped ruynway). Dont make much noise and seems there is no movement too.
    Can the bearing fail "invisibly" or is it obvious and easy to test ?

    Also, can the Z-servo go haywire when there is some rumble on axis ? Sounds improbable but who knows.

    I meaan, can small vibration mess with feedback so the servo "amplifies" these ?

  5. #5
    Join Date
    Oct 2007
    Country
    SPAIN
    Posts
    4,516
    Post Thanks / Like
    Likes (Given)
    448
    Likes (Received)
    263

    Default

    I wonder if you have a servo amp failing (or needs tuning)? Do you get oscillation at a point and the motor humming?
    I think with thrusts, they're either okay or shot. But they are cheap to replace compared to a ballscrew so would be my first thing to change to eliminate your problem.


Tags for this Thread

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
  •