The relationship among the spindle rotating speed, processing speed, and the tools

The rotation speed of the spindle motor should not necessarily
be high

Higher rotation speed of the spindle motor tends to cause the large degree of runout.
The below figure represents the correlation between the rotation speed of the small size spindle motor (Max speed 100,000 rpm) and its runout.

The Correlation between the rotation speed of the small size spindle motor and its runout Measuring instrument; MITS NANOMETRIC SENSOR MODEL 211

In this figure, degree of the runout sharply increases from the point over 75,000 rpm.
Additionally, when the degree of the runout augments, it ends up in many unfavorable results, such as

- Causing a lot of burrs on the circuits
- Thin end mills become even more fragile

There is the optimum rotating speed for the tools

Tools have their own optimum speed of rotation and processing that the tool manufacturer recommends.

For instance, 90 degrees end mills, it is 30,000 rpm and 15mm/sec.
Higher rotating speed shortens the longevity of the tools and higher processing speed makes the tools fragile.

The optimum rotating speed and the optimum processing speed vary depending on the tools and the substrate board.
The finishes of the processing is better when the rotating speed is lower than higher depending on the processing material as reported by the case example by The University of Tokyo.