Here is a picture. it’s the lines going the same directions as the arrow I drew. It kind of seems like chatter but the x move areas are smooth. what would be some stuff for me to check? would a bad bearing block do this? Thank you.
I recently did a project where minimizing these lines was key. I have two observations that might help:
Tram your spindle! If it only happens in one axis (X motion vs Y motion), it’s likely your spindle is tilted a bit in the other axis (i.e. if motions along Y cause lines, you’re tilted in X - the tilt is perpendicular to the motion). I ended up building a tramming tool for mine and found it “nodded” forward quite a bit.
Inspect the lines under a microscope. I found that climb vs conventional cutting caused a different type of tear-out in the underlying wood pores, as well as the different feet-per-minute tool speed for the different sides of the bit. You might need to change your toolpaths to be less than 50% overlap and only one direction.
The other thing I thought of trying, but didn’t, was to use a bit that had a radius at the tip instead of a sharp corner. I thought the sharp tip was scratching the underlying wood, but it turned out that the above two options fixed it well enough. I also made sure my toolpaths ran in the same direction as the grain, to help hide what lines remained.
By this I mean, most metalworking end mills have a small radius, like 0.010 inch, instead of a sharp 90 degree corner like woodworking router bits have, at the outer edge of the tip of the cutting surfaces.
Figured it out. Had just a hair of play on the right side of my gantry. found a few of the bearing block screws that were under stuff loose. seems good to go now. I guess no more getting in a hurry when re tightening things. I know I should have looked there sooner. last time I looked for stuff to retighten I didn’t want to re set my square sensors so didn’t take it all apart. Lesson learned.