In milling, vibrations can be caused by limitations in the cutting tool, tool holder, machine tool, workpiece, or fixture. To reduce vibrations, there are a number of strategies to consider.
Cutting Tools
（1）For face milling, the direction of the cutting forces must be considered:
1）When using a 90° cutter, the cutting forces are mainly concentrated in the radial direction. This can cause the cutter to wobble in long overhang conditions; however, low axial forces are beneficial when milling thin-walled/vibration-sensitive parts.
2）45° milling cutter can generate evenly distributed axial and radial forces
3）Round insert cutters direct most of the forces upward along the spindle, especially at shallow depths of cut. In addition, 10° cutters transfer the majority of the cutting forces into the spindle, reducing vibrations caused by long tool overhangs.
（2）Choose the smallest possible diameter for the process
（3）DC should be larger than ae for about 20-50%
（4）Choose a coarse pitch and/or uneven pitch cutter
（5）Lightweight milling cutters are advantageous, such as those with aluminum alloy cutter bodies.
For unstable thin-walled workpieces, use a large entering angle = low axial cutting forces; for long tool overhangs, use a small entering angle = high axial cutting forces.
Handle
The modular toolholder system enables the assembly of the required tool length while maintaining high stability and minimal run-out.
1）Keep the tool assembly as rigid and short as possible
2）Choose the largest possible post diameter/size
3）Use adaptors that fit oversized cutters and avoid using reduced-diameter adaptors
4）For small cutters, use a tapered adapter if possible
5）In operations where the last pass is deep in the part, switch to an extended tool at a predetermined location. Adjust cutting parameters for each tool length
6）If the spindle speed exceeds 20,000 rpm, use a dynamically balanced cutting tool and tool holder.
Oversize milling cutter
Always use the shortest possible tool length and gradually increase the length
Vibration-damping milling cutter
If the overhang is greater than 4 times the tool diameter, the tendency for milling vibrations may become more pronounced and a vibration-damped milling cutter can significantly increase productivity.
Cutting edge
To reduce cutting force：
1）Choose a lightly loaded geometry -L with sharp cutting edges and a thinly coated grade
2）Use inserts with small nose radius and small parallel lands
Sometimes the tendency to vibrate can be reduced by adding more damping to the system. Use a more negative cutting edge geometry and a slightly more worn cutting edge.
Cutting parameters and tool path programming
1）Always position the milling cutter off-center relative to the milling surface
2）For KAPR 90° long-edge milling cutters or end mills, use a small radial depth of cut (max. ae = 25%×DC) and a large axial depth of cut (max. ap = 100%×De)
3）When face milling, use a small depth of cut ap and a high feed fz with round inserts or a high feed cutter with a small entering angle.
4）Avoid vibrations in corners by programming large circular cuts, see Milling inside corners
5）If the chip thickness becomes too thin, the cutting edge will scrape instead of cut, causing vibration. In this case, the feed per tooth should be increased.
Lathe
The condition of the machine tool can have a large impact on the tendency of milling vibration. Excessive wear on the spindle bearings or feed mechanism will lead to poor machining performance. Carefully choose the machining strategy and cutting force direction to make full use of the machine tool stability.
Every machine tool spindle has unstable regions that are prone to vibration. The stable cutting region is described by the stability diagram and increases with increasing speed. Even a speed increase of as little as 50 rpm can change the cutting process from an unstable state with vibration to a stable state.
Workpiece and fixture
When milling thin-walled/base parts and/or when the fixture is less rigid, consider the following:
1) The fixture should be close to the machine table
2) Optimize tool paths and feed directions toward the strongest machine/fixture to achieve the most stable cutting conditions
3) Avoid machining in directions where the workpiece is not well supported
4) When the fixture and/or workpiece are less rigid in a particular direction, reverse milling can reduce vibration tendencies
When the fixture rigidity is poor, use the feed direction toward the machine table.
Note that the first cut should be made at 1/2 the depth of the second cut, the second cut should be made at 1/2 the depth of the third cut, and so on.
