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Having to retighten eccentric spacers

Discussion in 'CNC Mills/Routers' started by Andreas Bockert, Nov 23, 2017.

  1. Andreas Bockert

    Andreas Bockert Well-Known

    Oct 1, 2017
    Likes Received:

    After running for a while I there seem to be slack creeping in to my CNC. I have had to readjust the eccentric spacers a number of times to take out the slack. Since many of the them are hidden inside the C-beams this is a PITA.

    I've tightened the bolts down as hard as I dare (I've stripped a few already).

    Is this just a run-in problem that I can expect to resolve it self?
    Is this just something I have to live with?
    Have I done something wrong?
    Is there a hack that fixes it?

  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Dec 20, 2013
    Likes Received:
    Haven't experienced this personally but understand the potential for it. One suggestion would be in situations where there is gravity load affecting one line of wheels more than another to put the wheels with the regular (non-eccentric) spacers to be carrying the load. I.e. for a horizontal gantry beam with outside wheels, the top wheels will be carrying the gravity load of the gantry and thus should be the non-eccentric spacers whereas for a C-Beam with interior wheels the lower wheels would be the gravity wheels and would receive the fixed spacers. (Granted none of this helps on sphinx style machines where the eccentrics are where they are.) Another suggestion would be using witness marks across the interface of the eccentrics and plates to be certain that movement of the eccentrics is the problem and not bearing wear. Red nail polish would be the easiest way to accomplish this. A final thought would be a dab of thread-lock on seat of the eccentric spacer. You don't want to glue these in place as they may need future adjustment but anything that would add a bit of friction should be helpful. Do be sure and check the problem is not bearing wear though as I have had problems with this on a system that took a lot of abuse.

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