More ovals -- even after new set screws

I was super excited to cut my first aluminum last night. I researched my speeds and feeds extensively and was happy with how easily I was able to get the machine to work.

I was cutting Aluminum Flat Bar, 1/4" x 4", 6061 General-Purpose Plate, T6511 Mill Stock with Kodiak Cutting Tools KCT166406 1/8 End Mill. I was cutting a 5 mm holes using 10k rpm with a feed rate of 500 mm/min and plunge of 120 mm/min for a boring operation in fusion 360 with a pitch of 0.5 mm.

Just because I was nervous, I only drilled down 2 mm and the whole operation was super fast and easy with nice circles. Confident, I increased my depth to 5mm but the resultant boring operation produced ellipse bigger than the hole with the major axis in the y direction. I had this problem before as mentioned in Strange Behavior - Shapeoko cuts Ellipse, not circle.

I did the machine checklist, replaced and tightened the set screws, cleaned all the interfaces between the belts and the machine.

Any ideas?

Tim

Can you flex your z-axis about the X-rail? Grab the bottom of router and pull and push along the Y-axis.

If you’ve thoroughly ruled out all of your set screws and pulleys, maybe you’ve got slop in your Z-axis?

Even check that your Y-plate screws are tight into your X-rail. A little slop there could cause the rocking back and forth?

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And after you are done with the mechanical checks, check your belt calibration params too ?
i.e. when jogging by e.g. 1inch along X or 1 inch along Y, does the router actually move by exactly 1 inch? If the size difference in your oval between the X and Y dimension is not a lot, it could just be that a little belt calibration adjustment is required.

Can you cut perfect circles in a soft material ?

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Thank you very much for your quick suggestions. I continue to be inspired and impressed by this community.

Next steps:

  • Check for y-axis slop
  • Check all set screws and pulleys to include y-plate screws
  • Check belt calibration params
  • See if I can cut perfect circles in soft material

I’ll try this tonight and post results here.

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