1. You first need to analyze the possible causes of error according to the situation of the workpiece after processing.
2. Then exclude one by one according to the size of the impact.
3. Sometimes the final workpiece error is an accumulation of every small error.
4. There are some factors that cannot be eliminated due to your objective conditions.
Possible measures:
1. Reduce the spindle runout accuracy to within 0.005mm.
2. Change to a hydraulic toolholder.
3. Slide rail with needle bearings, steel guide.
4. Select ball screw.
5. Add digital display device.
6. Improve the clamping form, strengthen the workpiece, fixture system rigidity.
The above suggestions are for reference only.