Is your previous statement about machining accuracy correct?

We all know that machining accuracy refers to the degree to which the actual dimensions, shape, and position of the machined part surface conform to the ideal geometric parameters required by the drawing. So, when we have a demand for precision machining, our first reaction is to find a device that can perform precision machining, and our inventory of precision machining equipment comes from parameters. In fact, the definition of precision varies from country to country.

Let's take a rigorous look at those things about accuracy!

Accuracy: refers to the degree of closeness between the obtained measurement results and the true values. High measurement accuracy refers to a small systematic error, where the average value of the measurement data deviates less from the true value, but the data is scattered, that is, the size of the accidental error is not clear.

Precision: Refers to the reproducibility and consistency between the results obtained from repeated measurements using the same backup sample. It is possible to have high precision, but the accuracy is not precise. For example, the three results obtained by measuring with a length of 1mm are 1.051mm, 1.053, and 1.052, respectively. Although they have high precision, they are not accurate.

In a promotional article for a CNC machine tool, the "positioning accuracy" of machine tool A is marked as 0.004mm, while on another manufacturer's sample, the "positioning accuracy" of similar machine tool B is marked as 0.006mm. From these data, you would naturally assume that machine tool A has higher accuracy than machine tool B.

However, in fact, it is very likely that machine tool B has higher accuracy than machine tool A, and the problem lies in how the accuracy of machine tool A and B are defined respectively. So, when we talk about the "precision" of CNC machine tools, we must clarify the definitions and calculation methods of standards and indicators.