It is misleading to regard that the better resolution of the machine is the better finishes
of the processing.

The limit of resolution

The limit of resolution means the value of the minimum step of the command signal
regulating the X, Y, Z axis of the machine.
It does not mean the processing accuracy.

In order to realize the processing the PCB of great precision, it is much more difficult to
mitigate the backlash on each axis of the machine and to produce machines with utmost
care and attention to the degree of orthogonality or flatness of the table, than to
increase the limit of resolution.

What is the accuracy of a board making machine?

The following factors dominate the accuracy of the finished products by the
prototyping machines;

1. Accuracy in the repeated milling operation
2. Accuracy in tool positioning
3. Degree of machine vibration during operation
4. Degree of the spindle runout
5. Accuracy of a milling tool and the degree of the tool wear

The processing accuracy is influenced by the worst value of the above five factors.
Hence, it is delusive to state that the overall accuracy is good enough by taking up
the partial factor (resolution).