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Issues with accuracy

Discussion in 'CNC Mills/Routers' started by TC Follansbee, Apr 27, 2023.

  1. TC Follansbee

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    Openbuilds lead 1515 running router11. 1/4 compression bit. Cutting whisky smokers out, pretty simplistic design with 3 ovals. The problem is that while the first board cut worked perfectly every cut after the second board has had a growing problem where the outside cutout at the start isn't cutting the radius correctly instead it's flattening the corners.
    Does not seem to be skipping steps, whip doesn't seem to be an issue. I was worried it might be slop in the middle of the table but I moved to the home position in bottom left and re ran the file and it still cut bad.
    Using carbide create 6 to create the file and tiling the cut with gcode tiler by fjield. I've attached both gcode files.

    The one thing I'm noticing is that the plastic rollers in the aluminum track are not great at handling torque and there is slop in the z axis that won't go away even after tightening and adjusting the bolts holding the rollers.
     

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  2. TC Follansbee

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    I've sanded heavily the handful of pieces finished with an attempt to get rid of the scuff corners but I can try and post pictures if it's useful.
     
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Post some pictures of the cut pieces too :)
    Issues like these are usually more mechanical, and looking at the cut can give some clues. The GCODE doesn't show any obvious differences
     
  4. TC Follansbee

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    Like I said sanded down so it's probably pretty hard to see but there are flat-ish spots in the radius that didn't fully translate
     

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  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Check grubscrews on the X and Y leadscrews, looks like the coupler is either slipping a little on the motor shaft or the leadscrew during direction changes.
    Also make sure
    1) Nothing else is loose (give the endmill a wiggle by hand - if you feel unwanted movement, follow the "feeling" of the movement to locate source as you move up and away from the endmill (possibly loose wheels, loose fasteners, etc)
    2) Machine is trammed Tramming: A generic guideline
     
  6. TC Follansbee

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    There is definitely movement but it's in the wheels on the router plate on the z axis and they've already been tightened. I can wiggle the whole router plate a bit and it seems to be just the nature of the wheels on the track. It doesn't seem like enough movement to account for the level of off but I'll check the couplers
     
  7. TC Follansbee

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    Found another picture less sanded that shows the flat spots better. See the left side
     

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  8. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    If they have, they shouldnt have play:

    Adjust to dial out preload as shown in (not loose, not tight, just to the point the wheel starts to feel some grip)

     
  9. David the swarfer

    David the swarfer OpenBuilds Team
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    clear indication of backlash in Y I think. think about what direction the rotating bit is trying to move vs the direction the machine is trying to move it.
    apart from finding and fixing whatever is loose, consider reducing your step down, 1/8" is a lot in hardwood, especially with a compression bit
     

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