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Thread: Z-Axis Linear Guide Replacment Options - PRS 4 x 8

  1. #1
    Join Date
    Jan 2020
    Posts
    4

    Default Z-Axis Linear Guide Replacment Options - PRS 4 x 8

    This will be my first post.

    I picked up a very distressed 2008 PRS 4 x 8 in December for a good deal and have slowly been taking it apart bolt by bolt to remove rust, refinish, clean, etc.

    I'm now working through the Z-axis sled and have run into some trouble. The Bishop Wisecarver steel channels have severe divots along the machined surface of the guide, and I've also found the V-wheels to have flat spots as well.

    Working through some quotes a fix for this is looking to be well over $1,000 through ShopBot, and almost as much through Bishop Wisecarver.

    I'm wondering if anyone has run into a similar problem and transitioned their machine Z-carriage to a more standard linear MGN rail system and saved some money.

    Looking for any recommendations here for a low-cost solution.

    0126201342b.jpg
    0126201342_HDR.jpg

    Here is a video of how jolty the movement is.
    https://youtu.be/PkozNoUkvW4

  2. #2
    Join Date
    May 2014
    Location
    MA
    Posts
    529

    Default

    Depending on how crafty you are you might consider retrofitting some linear rails on that instead trying to replace those BWC bits.

    Newer ShopBots come with linear rails on the Z anyway so you could probably look at those for inspiration, or just come up with your own setup.

  3. #3
    Join Date
    Jan 2020
    Posts
    4

    Default

    Thanks Eric. I looked around for some examples of folks having run linear rails and just can't quite find enough. I think what I am going to end up doing is biting the bullet for the Bishop guides new, but swapping all the V-Bearings from the blocks on the Z-axis with ones from the Y and X.

    Since the Z-axis bearings run external, wear there shouldn't matter on the Y and X rails, and vice versa. I at least save myself a couple hundred on new bearings this way.

  4. #4
    Join Date
    May 2014
    Location
    MA
    Posts
    529

    Default

    It really shouldn't be that hard.. Just look at just about any DIY CNC builds out there that have liner rails for the Z. Basically you can bolt just about whatever you want to that big blue back plate that slides back and forth in Y.

    On a PRS you don't need to get the spindle exactly back where it was from the factory, there's plenty of extra travel on X, and there's extra on Y too.

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