Wood milling problems

I don’t know why im having this problem. As shown in the picture, i’m getting like curves in places where it supposed to be straight lines. Any recommendation to fix this issue?


I’d say one of your axis has allot of play in it, or you have going too deep per cut?

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Hi MrBeaver! Thanks for your fast reply!

I think I might be a little too deep but for some reason I think is not too deep (0.1500" Depth per pass), maybe it could be an axis too loose?

This is the actual setup for that part.


This will be easier to puzzle out if you’ll share your entire machine setup:

  • machine
  • variation
  • endmill
  • material
  • clamping orientation

Hi WillAdams, sorry about that.

Machine: Shapeoko 3 XXL
Endmill: 1/4" 4 Flute Endmill (.250")
Material: 1.330" thick maple wood.
Clamping orientation: About 5.75" in X axis, 9.0" in Y axis, 1.330" in Z axis.
Variation: (not sure if you refer to speed in RPM, if so is 4,000 RPM).


By variation, I meant which specific model, one of:

  • SO3 initial version
  • SO3 initial version but with upgraded Z-axis plate and/or 9mm belts
  • SO3 summer 2015 or later
  • SO3 XL
  • SO3 XXL

Those look to be very regular — what does the toolpath preview look like?

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Ok got it! in that case mine is a SO3 XXL, I bought it in 2016.

For me it looks pretty good.

Are all the outer edges straight and cut at the same time? No changes to the tools?

It doesn’t look like your cutting paths.

Have you checked belt tension and spindle wobble?

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Yes, correctly. I’m not sure if a tool change is necessary and im a little worried that if the program requests a tool change it might come with an error if I turn off the router.

No I haven’t do you have any information on how to check for spindle wobble and belt tension?
I made some research and found this video on youtube about belt tensioning: https://www.youtube.com/watch?v=_lIIb_PdziA

Hold the mill end and give it a wobble with your hand - if you see any play something is wrong

Couple thoughts come to my mind, but thinking out loud anyways. May be a dumb question, but are you sure you have a 0.25" end mill installed (forgive me if I’m wrong, not trying to insult). As was pointed out these look like really consistent defects, maybe it thinking it’s a 0.25" end and you have something larger installed. Other thought is this part appears to be pretty much a 2.5D milling operation, is there some reason why you have 3D roughing passes and not just plain roughing with a waterline and pencil cleanup? Again, just thinking out loud, disregard if not helpful.


Already did a quick troubleshoot and noticed that my SO3 doesn’t have rails in the Y axis motors to be adjusted. So I noticed that the belts were a little loose, and adjusted it, same for the X axis. About the wobble, it doesn’t feel like its wobbling.

So now thinking about it, I did a bigger piece (the one attached, not finished) and noticed that the X and Y planes are straight. The problem with the piece with four squares shown before may be linked with the necessity of tool change with a smaller bit (as the squares are smaller)? I need to mention that this last piece was cut in the X direction only, and the one with four squares in X and Y direction for the finishing pass.

Hi DanonlnTx,

Yes Im sure its a 0.250" end mill, no I don’t have any reason to have a 3d roughing pass. Is there any difference when milling and object with 3D roughing pass and without it? This piece was 3d modeled.

Thanks Dan!

Beware I’m nowhere near an expert at these things, but just looking at the part I see no details that have to be truly cut in 3D. In 2.5D the machine cuts a layer in X/Y, then lowers to the next depth in Z, then resumes the next layer in X/Y. Whereas when doing true 3D all axis are moving at the same time (great for parts with complex curves, lithophanes, stuff without square sides, etc.). The part I’m seeing in your photos looks to be pretty square and I’m thinking all of the 3D passes you’re making are not efficient at all. I don’t know/think they are the source of your problems per se, but they definitely make it more complicated and time consuming. Try getting rid of the 3D roughing and “Cut X then Y” finish passes and see what the preview looks like, should be less complicated and much quicker to machine. Again, I’m barely a newbie myself;-)


It looks like backlash. That is, the router is in a different position in Y for the same coordinate depending on which direction it was traveling from. My guess is that with the steppers engaged (but not moving), you can move the carriage forward and back about an 1/8". Perhaps a loose pulley?

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