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Thread: Drifting Skipping Axis?

  1. #51
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,904

    Default

    Please run the US command in SB3 so that it creates a snapshot of your settings and creates an .SBD file. Give it a meaningful name and save it to your desktop or you might have trouble finding where you saved it. ZIP it up or rename the .sbd to .txt and post here. - OR, just open it up, copy the text and paste into the body of a post/message.

    It appears to me that you have some settings that are not working for what you are doing. This would be especially true if you have been messing with VR commands ~ it's VERY easy to get them to a point where the tool does weird things.

    It's also important to note that you are running the tool in all 3 axes when rastering, which uses up a lot of COM. 3,2 might be a bit too aggressive - but lets look at your settings first.

    -B
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  2. #52
    Join Date
    Apr 1999
    Location
    Rock Hill SC
    Posts
    460

    Default

    I have the same desktop and have dealt with a similar problem. If the machine is making a "groaning" noise when the Y axis moves you have fouled the linear bearings on the left and right side of the machine. I see from your earlier posts that you have already been into this, but let me add some extra light to the situation.
    I can see that you are running speeds that produce chips rather than sawdust, a very good thing. But keep in mind that there is also some very fine wood dust being produced. It lands on the rails of the Y axis and will eventually work its way into the linear bearings and cause the balls inside to jam and stick.

    There is no real adjustment for squaring the Y axis, but you can help it a little bit by loosening the screws on each side and holding it as square to the X axis as you can while you tighten the screws.

    Another good thing to do. At the front of the machine loosen the screws that hold the end of the ball screw for the Y axis. Run the axis all the way forward and tighten the screws. Now loosen the screws on the motor at the rear of the machine. Run the axis all the way to the rear and tighten these screws.

    I also removed the bearings, one at a time, and cleaned them in mineral spirits and lubricated with WD-40. I have two sets of bearings now so that I can just change them out if need be. Finally I made a couple of "Elephant Ears" that magnetically attach to the cheeks of the gantry and keep dust from falling on the rails of the Y axis. As part of the daily shut down I wipe the rails down and use a little 3 in 1 oil on them. The real answer is two motors driving two jackscrews for that axis but the foregoing has kept my desktop running smoothly for a couple of years now.

  3. #53
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,904

    Default

    For sure the Y axis bearings are very susceptible to getting jammed up from chip/dust infiltration. Take care when servicing them. Without a complimentary section of rail to slide them onto when removing - the balls will fall out. SB sells replacement bearing blocks. Be sure to note what brand they are - THK or PMI when you order...they are not cheap. The placement of the rails on the DT was a poor design decision. The added protection of the DT Max is way better.

    As Tom pointed out - a chip guard of sorts will help keep them clean. I did the same thing with some 6" tall (just enough to clear the bottom of the gantry beam) coroplast mounted on some angle iron. It makes a huge difference. As also noted, after or during - it's a good idea to clean those rails. You can vacuum them off or blow them off, but avoid blowing chips into the bearing blocks.

    I saw your VR settings posted above, but since then you commented about altering your VR settings. Please post them up again or copy/paste the content of your SBD file AFTER you run US.
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  4. #54
    Join Date
    Oct 2012
    Location
    Leesburg, VA
    Posts
    8

    Default

    @tlempicke: Ugh.... I'm getting the "moan and groan" again on my DT (THK bearings). Last time this manifested itself as jittery behavior while doing small-ish circles (under an inch in diameter -- same conditions repeating). Problem was solved by replacing one of the bearings on my gantry.

    I ass-u-me-d that once the bearings "failed" they were done for (though at the replacement cost, I kept the old one for posterity). It sounds like you have had success with cleaning and re-lubing the bearings, and in fact, have a good maintenance plan for keeping them in good shape. Any side-effects to the mineral spirits and WD40?

    Also, I make it a habit of vacuuming and brushing all dust from the rails (both x and y) after most tool changes, but liked the idea of your elephant ears. Do you have a picture of your elephant ears?
    Last edited by CNCDave; 03-06-2019 at 10:44 AM. Reason: Add reference to original poster

  5. #55
    Join Date
    Apr 1999
    Location
    Rock Hill SC
    Posts
    460

    Default "Elephant ears"

    Sorry to take so long getting these to you. Here are four pix. The first shows the "elephant ears" in action, the fourth shows the magnets that hold them to the supports for the gantry.
    Attached Images Attached Images

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