CNC Machining Guide & Methods Of Improving Machining Accuracy Of CNC Parts

November 4, 2021

CNC machining accuracy and machining error are terms to evaluate the geometric parameters of machined surfaces. However, the actual parameters obtained by any machining method will not be absolutely accurate. From the function of the part, as long as the machining error of the part is within the tolerance range required by the part drawing, it is considered to ensure the machining accuracy.


CNC machining accuracy refers to the degree that the actual geometric parameters (size, shape and position) of the part after machining are consistent with the ideal geometric parameters. The difference between them is called machining error. The machining error reflects the machining accuracy. The larger the error, the lower the machining accuracy, and the smaller the error, the higher the machining accuracy.


The following briefly introduces 7 methods to improve the machining accuracy of CNC parts:
Adjustment of process system:

1. The adjustment of trial cutting mode is through a series of processes of "trial cutting - measuring size - adjusting tool cutting amount - cutting - re cutting", which can be repeated until the required size is reached. However, this method has low production efficiency, so it is mainly used for single piece and small batch production.

2. Adjustment method the adjustment method is to obtain the required size by adjusting the relative position of machine tool, fixture, workpiece and tool in advance. However, due to its high productivity, this method is mainly used for mass production.

3. Reduce machine error, in order to improve the manufacturing accuracy of spindle components, the rotation accuracy of bearings should be improved:
① Select high-precision rolling bearing.

② High precision multi oil wedge dynamic pressure bearing is adopted.

③ High precision hydrostatic bearing.

4. The accuracy of accessories with bearings shall be improved:

① It can improve the machining accuracy of box support hole and main shaft journal.
② It can improve the machining accuracy of the mating surface with the bearing.
③ By measuring and adjusting the radial runout range of corresponding parts, the error can be compensated or offset.

5. The rolling bearing needs proper preloading:
① Clearance can be eliminated.
② Improve bearing stiffness.
③ Uniform rolling element error.

6 Reduce the transmission error of the transmission chain:
① Less transmission parts, short transmission chain and high transmission precision.
② By adopting deceleration transmission, this is an important principle to ensure transmission accuracy. And the closer to the end of the transmission pair, the smaller the transmission ratio.
③ The accuracy of the end piece needs to be higher than that of other transmission parts.

7. To reduce tool wear, the tool must be reground before the tool size wear reaches the sharp wear stage.