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The relationship among the spindle rotation speed, processing speed, and the tools
--- Does higher spindle revolutions equal top-of-the-line machine? ---

High Revolutions Spindle Motor: Advantages and Disadvantages

Advantages
  1. Effective for small-diameter drilling
  2. Increase in processing speed

Disadvantages
  1. Required for idle running/warm-up before
  2. Needs maintenances with extra care, will result malfunction if not
  3. Increase in run-out
  4. Highly expensive

Above-mentioned are both advantages and disadvantages for high revolutions spindle motor.


Considering the application of the prototyping machine

The following points are to be considered for mass production and prototyping machine tools.

Spindle Motor for Small-Size PCB Prototyping Machine
Most of commonly used spindle motors use ball bearings. However, with ball bearings, it is practically impossible to eliminate vibration or tool runout at high rotation speed.
Desk top PCB prototyping machines use compact spindle motors. If you try to run them at higher revolutions, the level of runout becomes too high to perform precision milling.


Spindle Motor for Large-Size Mass Production PCB Drilling Machine
Some of the high performance spindle motors used on large-size mass production PCB drilling machines are capable of running at 200,000 rpm or higher.
Their internal mechanisms, bearings, Collet Chuck mechanisms and others are specially designed and built so that runout at higher speed is minimal. Bearing mechanisms are closely related to the runout and hydrostatic bearings (fluid bearings), such as oil lubricated bearings and air bearings, are employed to minimize.



The picture one the right illustrates the spindles motors installed on; ① is mass production model
and ② is desktop type prototyping machine model.

Maintenance for Spindle motor
It is required to have 5 minute idle running before operation and cleaning the collet especially for the spindle motor over 100,000 rpm; it may be a cause of technical troubles. For the mass production factory, they even employ staff specialized for the spindle motor maintenance.

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 rotation 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.


Conclusion

In PCB prototyping machine, from the above, machine installed with high revolutions spindle motor will be expensive, however it does not mean the performance will be superior. Please select your machine deliberately with its cost-effectiveness.


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