Regeneration of Waviness

​While this is an animation of a single point tool it illustrates how regenerative chatter vibration occurs in milling. The tool is not 100% rigid (no physical object is), so it leaves an irregular surface as it cuts. The next tooth travels over that irregular surface so the vibration increases and chip thickness variation gets worse with each pass from no contact at all to well beyond the recommended limit. This chip thickness variation creates the feedback loop that we audibly hear as chatter.