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Help please!! Backlash

Discussion in 'CNC Mills/Routers' started by Helzya907, Jul 6, 2020.

  1. Helzya907

    Helzya907 New
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    After running a test on some plywood I noticed the circle is not very circular. Will eventually be made from acrylic. Object was copied and grouped to run as one on Inkscape. Both left sides of the circle are slightly wrinkled. WorkBee 1510 tapered ball nose 1/16 endmill. I'm a newb. Thanks you. 20200706_173845.jpg 20200706_173816.jpg 20200706_173750.jpg
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Mechanical in nature... Something is loose that should be tight. Hold the endmill, give it a wiggle and see what moves. Follow that movement to the source.
    - loose wheels (adjust eccentrics)
    - loose setscrews on shaft couplers or pulleys (a little loctite prevents them rattling loose)
    - stop collars on leadscrews not tight against the bearings
    - etc
     
  3. Christian James

    Christian James Journeyman
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    ...belts not tensioned correctly?
     
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  4. Helzya907

    Helzya907 New
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    Everything feels right, no play anywhere. The part in the top photo lower arrow seems to be a code issue. Anyone know how to read the code to see if i have an issue there?
     
  5. Helzya907

    Helzya907 New
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    When it runs the second pass a you can see in the picture it has a separate line. It's only on the bottom half of the circle. Corrects itself then continues on normal!!
     

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  6. Helzya907

    Helzya907 New
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    These are two circles made on the Openbuilds Cam gcode generator. Just as a test. Do I need to reset something? I'm lost!!
     

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  7. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Clearly shows mechanical deviation.. Something is loose... Software cannot fix that, check the machine itself. Loose pulleys, couplers, belts, wheels etc.
     
  8. Helzya907

    Helzya907 New
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    Thank you for the replies. Everything is tight, wriggled everything, checked every wheel, nut, bolt no play. How tight should the belts be?
     
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    About 12kg or force. But recheck the setscrews on the pulleys. That looks like pulley slightly loose on motor shaft. Tight enough that when you check it it looks right, but under load it shifts on the D shape (thus just slightly, not all round)
     
  10. JustinTime

    JustinTime Veteran
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    People take pictures in Portrait mode and then post it in Landscape, so it's difficult to tell which axis has the play. In the first batch of pictures it looks like the X axis has a play but in the second batch it looks like the Y axis.

    What you see is called backlash and can have two main reasons. One is a loose connection, like Peter mentioned (and the most common one) and, two, a play in the nut of the lead screw. Since you don't use lead screw, IIRC, than look at what Peter said.
     
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